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Sample records for memory polymer stents

  1. Thermomechanical Properties, Collapse Pressure, and Expansion of Shape Memory Polymer Neurovascular Stent Prototypes

    PubMed Central

    Baer, Géraldine M.; Wilson, Thomas S.; Small, Ward; Hartman, Jonathan; Benett, William J.; Matthews, Dennis L.; Maitland, Duncan J.

    2011-01-01

    Shape memory polymer stent prototypes were fabricated from thermoplastic polyurethane. Commercial stents are generally made of stainless steel or other alloys. These alloys are too stiff and prevent most stent designs from being able to navigate small and tortuous vessels to reach intracranial lesions. A solid tubular model and a high flexibility laser etched model are presented. The stents were tested for collapse in a pressure chamber. At 37°C, the full collapse pressure was comparable to that of commercially available stents, and higher than the estimated maximum pressure exerted by intracranial arteries. However, there is a potential for onset of collapse, which needs further study. The stents were crimped and expanded, the laser-etched stent showed full recovery with an expansion ratio of 2.7 and a 1% axial shortening. PMID:19107804

  2. Fabrication and In Vitro Deployment of a Laser-Activated Shape Memory Polymer Vascular Stent

    SciTech Connect

    Baer, G M; Small IV, W; Wilson, T S; Benett, W J; Matthews, D L; Hartman, J; Maitland, D J

    2007-04-25

    Vascular stents are small tubular scaffolds used in the treatment of arterial stenosis (narrowing of the vessel). Most vascular stents are metallic and are deployed either by balloon expansion or by self-expansion. A shape memory polymer (SMP) stent may enhance flexibility, compliance, and drug elution compared to its current metallic counterparts. The purpose of this study was to describe the fabrication of a laser-activated SMP stent and demonstrate photothermal expansion of the stent in an in vitro artery model. A novel SMP stent was fabricated from thermoplastic polyurethane. A solid SMP tube formed by dip coating a stainless steel pin was laser-etched to create the mesh pattern of the finished stent. The stent was crimped over a fiber-optic cylindrical light diffuser coupled to an infrared diode laser. Photothermal actuation of the stent was performed in a water-filled mock artery. At a physiological flow rate, the stent did not fully expand at the maximum laser power (8.6 W) due to convective cooling. However, under zero flow, simulating the technique of endovascular flow occlusion, complete laser actuation was achieved in the mock artery at a laser power of {approx}8 W. We have shown the design and fabrication of an SMP stent and a means of light delivery for photothermal actuation. Though further studies are required to optimize the device and assess thermal tissue damage, photothermal actuation of the SMP stent was demonstrated.

  3. Biodegradable shape-memory block co-polymers for fast self-expandable stents.

    PubMed

    Xue, Liang; Dai, Shiyao; Li, Zhi

    2010-11-01

    Block co-polymers PCTBVs (M(n) of 36,300-65,300 g/mol, T(m) of 39-40 and 142 degrees C) containing hyperbranched three-arm poly(epsilon-caprolactone) (PCL) as switching segment and microbial polyester PHBV as crystallizable hard segment were designed as biodegradable shape-memory polymer (SMP) for fast self-expandable stent and synthesized in 96% yield by the reaction of three-arm PCL-triol (M(n) of 4200 g/mol, T(m) of 47 degrees C) with methylene diphenyl 4,4'-diisocyanate isocynate (MDI) to form the hyperbrached MDI-linked PCL (PTCM; M(n) of 25,400 g/mol and a T(m) of 38 degrees C), followed by further polymerization with PHBV-diol (M(n) of 2200 g/mol, T(m) of 137 and 148 degrees C). The polymers were characterized by (1)H NMR, GPC, DSC, tensile test, and cyclic thermomechanical tensile test. PCTBVs showed desired thermal properties, mechanical properties, and ductile nature. PCTBV containing 25 wt% PHBV (PCTBV-25) demonstrated excellent shape-memory property at 40 degrees C, with R(f) of 94%, R(r) of 98%, and shape recovery within 25s. PCTBV-25 was also shown as a safe material with good biocompatibility by cytotoxicity tests and cell growth experiments. The stent made from PCTBV-25 film showed nearly complete self-expansion at 37 degrees C within only 25 s, which is much better and faster than the best known self-expandable stents.

  4. Shape memory polymers

    DOEpatents

    Wilson, Thomas S.; Bearinger, Jane P.

    2017-08-29

    New shape memory polymer compositions, methods for synthesizing new shape memory polymers, and apparatus comprising an actuator and a shape memory polymer wherein the shape memory polymer comprises at least a portion of the actuator. A shape memory polymer comprising a polymer composition which physically forms a network structure wherein the polymer composition has shape-memory behavior and can be formed into a permanent primary shape, re-formed into a stable secondary shape, and controllably actuated to recover the permanent primary shape. Polymers have optimal aliphatic network structures due to minimization of dangling chains by using monomers that are symmetrical and that have matching amine and hydroxl groups providing polymers and polymer foams with clarity, tight (narrow temperature range) single transitions, and high shape recovery and recovery force that are especially useful for implanting in the human body.

  5. Shape memory polymers

    DOEpatents

    Wilson, Thomas S.; Bearinger, Jane P.

    2015-06-09

    New shape memory polymer compositions, methods for synthesizing new shape memory polymers, and apparatus comprising an actuator and a shape memory polymer wherein the shape memory polymer comprises at least a portion of the actuator. A shape memory polymer comprising a polymer composition which physically forms a network structure wherein the polymer composition has shape-memory behavior and can be formed into a permanent primary shape, re-formed into a stable secondary shape, and controllably actuated to recover the permanent primary shape. Polymers have optimal aliphatic network structures due to minimization of dangling chains by using monomers that are symmetrical and that have matching amine and hydroxyl groups providing polymers and polymer foams with clarity, tight (narrow temperature range) single transitions, and high shape recovery and recovery force that are especially useful for implanting in the human body.

  6. Bare metal stents, durable polymer drug eluting stents, and biodegradable polymer drug eluting stents for coronary artery disease: mixed treatment comparison meta-analysis

    PubMed Central

    Toklu, Bora; Amoroso, Nicholas; Fusaro, Mario; Kumar, Sunil; Hannan, Edward L; Faxon, David P; Feit, Frederick

    2013-01-01

    Objective To compare the efficacy and safety of biodegradable polymer drug eluting stents with those of bare metal stents and durable polymer drug eluting stents. Design Mixed treatment comparison meta-analysis of 258 544 patient years of follow-up from randomized trials. Data sources and study selection PubMed, Embase, and Central were searched for randomized trials comparing any of the Food and Drug Administration approved durable polymer drug eluting stents (sirolimus eluting, paclitaxel eluting, cobalt chromium everolimus eluting, platinum chromium everolimus eluting, zotarolimus eluting-Endeavor, and zotarolimus eluting-Resolute) or biodegradable polymer drug eluting stents, with each other or against bare metal stents. Outcomes Long term efficacy (target vessel revascularization, target lesion revascularization) and safety (death, myocardial infarction, stent thrombosis). Landmark analysis at more than one year was evaluated to assess the potential late benefit of biodegradable polymer drug eluting stents. Results From 126 randomized trials and 258 544 patient years of follow-up, for long term efficacy (target vessel revascularization), biodegradable polymer drug eluting stents were superior to paclitaxel eluting stents (rate ratio 0.66, 95% credibility interval 0.57 to 0.78) and zotarolimus eluting stent-Endeavor (0.69, 0.56 to 0.84) but not to newer generation durable polymer drug eluting stents (for example: 1.03, 0.89 to 1.21 versus cobalt chromium everolimus eluting stents). Similarly, biodegradable polymer drug eluting stents were superior to paclitaxel eluting stents (rate ratio 0.61, 0.37 to 0.89) but inferior to cobalt chromium everolimus eluting stents (2.04, 1.27 to 3.35) for long term safety (definite stent thrombosis). In the landmark analysis after one year, biodegradable polymer drug eluting stents were superior to sirolimus eluting stents for definite stent thrombosis (rate ratio 0.29, 0.10 to 0.82) but were associated with increased

  7. Bare metal stents, durable polymer drug eluting stents, and biodegradable polymer drug eluting stents for coronary artery disease: mixed treatment comparison meta-analysis.

    PubMed

    Bangalore, Sripal; Toklu, Bora; Amoroso, Nicholas; Fusaro, Mario; Kumar, Sunil; Hannan, Edward L; Faxon, David P; Feit, Frederick

    2013-11-08

    To compare the efficacy and safety of biodegradable polymer drug eluting stents with those of bare metal stents and durable polymer drug eluting stents. Mixed treatment comparison meta-analysis of 258,544 patient years of follow-up from randomized trials. PubMed, Embase, and Central were searched for randomized trials comparing any of the Food and Drug Administration approved durable polymer drug eluting stents (sirolimus eluting, paclitaxel eluting, cobalt chromium everolimus eluting, platinum chromium everolimus eluting, zotarolimus eluting-Endeavor, and zotarolimus eluting-Resolute) or biodegradable polymer drug eluting stents, with each other or against bare metal stents. Long term efficacy (target vessel revascularization, target lesion revascularization) and safety (death, myocardial infarction, stent thrombosis). Landmark analysis at more than one year was evaluated to assess the potential late benefit of biodegradable polymer drug eluting stents. From 126 randomized trials and 258,544 patient years of follow-up, for long term efficacy (target vessel revascularization), biodegradable polymer drug eluting stents were superior to paclitaxel eluting stents (rate ratio 0.66, 95% credibility interval 0.57 to 0.78) and zotarolimus eluting stent-Endeavor (0.69, 0.56 to 0.84) but not to newer generation durable polymer drug eluting stents (for example: 1.03, 0.89 to 1.21 versus cobalt chromium everolimus eluting stents). Similarly, biodegradable polymer drug eluting stents were superior to paclitaxel eluting stents (rate ratio 0.61, 0.37 to 0.89) but inferior to cobalt chromium everolimus eluting stents (2.04, 1.27 to 3.35) for long term safety (definite stent thrombosis). In the landmark analysis after one year, biodegradable polymer drug eluting stents were superior to sirolimus eluting stents for definite stent thrombosis (rate ratio 0.29, 0.10 to 0.82) but were associated with increased mortality compared with cobalt chromium everolimus eluting stents (1.52, 1

  8. Bioresorbable Polymers and Stent Devices.

    PubMed

    Dehghani, Payam

    2017-02-01

    Percutaneous coronary interventions will never become obsolete, as evolution is inherent to interventional cardiology. Current drug-eluting platforms have appreciably improved their safety and efficacy profiles in different clinical settings compared to first-generation devices such that it is difficult to consider other alternatives. However, there is definite biological plausibility to consider devices with bioabsorbable polymers and/or scaffolds. It is also an undeniable fact that many patients, based on variety of belief systems, would prefer not to have a permanently implanted device. BP DES with or without bioresorbable scaffolds offer advantages over durable polymer DES in restoring normal coronary physiology and vascular adaptive responses, resulting in late lumen gain and plaque regression. They will likely allow flexibility in treating complex CAD. However, so far, we have been able to prove non-inferiority in a selected population of patients without long-term data. Is "as good as" good enough? Are we ready to reach for the BRS or a BP DES in our catheterization laboratory based on preclinical and mechanistic data (endothelialization, OCT imaging, vasomotion) with limited human experience? I am not. While I will maximize my efforts to recruit patients in related randomized controlled trials, the technology is not ready for prime time. Randomized controlled trials are needed to determine whether any or all of these devices improve long-term outcome compared to best in class DP DES. Most definitive evidence is likely about a decade away. Until then, we can learn to be disciplined implanters not only in selecting the appropriate patient but also in perfecting implantation techniques.

  9. Biodegradable Shape Memory Polymers in Medicine.

    PubMed

    Peterson, Gregory I; Dobrynin, Andrey V; Becker, Matthew L

    2017-09-21

    Shape memory materials have emerged as an important class of materials in medicine due to their ability to change shape in response to a specific stimulus, enabling the simplification of medical procedures, use of minimally invasive techniques, and access to new treatment modalities. Shape memory polymers, in particular, are well suited for such applications given their excellent shape memory performance, tunable materials properties, minimal toxicity, and potential for biodegradation and resorption. This review provides an overview of biodegradable shape memory polymers that have been used in medical applications. The majority of biodegradable shape memory polymers are based on thermally responsive polyesters or polymers that contain hydrolyzable ester linkages. These materials have been targeted for use in applications pertaining to embolization, drug delivery, stents, tissue engineering, and wound closure. The development of biodegradable shape memory polymers with unique properties or responsiveness to novel stimuli has the potential to facilitate the optimization and development of new medical applications. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Shape memory polymer medical device

    DOEpatents

    Maitland, Duncan; Benett, William J.; Bearinger, Jane P.; Wilson, Thomas S.; Small, IV, Ward; Schumann, Daniel L.; Jensen, Wayne A.; Ortega, Jason M.; Marion, III, John E.; Loge, Jeffrey M.

    2010-06-29

    A system for removing matter from a conduit. The system includes the steps of passing a transport vehicle and a shape memory polymer material through the conduit, transmitting energy to the shape memory polymer material for moving the shape memory polymer material from a first shape to a second and different shape, and withdrawing the transport vehicle and the shape memory polymer material through the conduit carrying the matter.

  11. Vessel healings after stenting with different polymers in STEMI patients

    PubMed Central

    Jin, Qin-Hua; Chen, Yun-Dai; Tian, Feng; Guo, Jun; Jing, Jing; Sun, Zhi-Jun

    2016-01-01

    Background Different stents implantation in ST-segment elevation myocardial infarction (STEMI) patients may influence the long term prognosis by affecting vessel healings after stenting. The aim of this study was to evaluate the vessel healings after implantation of drug eluting stents (DES) with biodegradable or durable polymer or of bare-metal stents (BMS) in patients with acute STEMI. Methods This study included 50 patients, who underwent follow up angiogram and optical coherence tomography (OCT) assessment about one year after percutaneous coronary intervention (PCI) for STEMI. According to the initial stents types, these patients were classified to durable (n = 19) or biodegradable polymer sirolimus-eluting stents (n = 15), or BMS (n = 16) groups. The conditions of stent struts coverage and malapposition were analyzed with OCT technique. Results A total of 9003 struts were analyzed: 3299, 3202 and 2502 from durable or biodegradable polymer DES, or BMS, respectively. Strut coverage rate (89.0%, 94.9% and 99.3%, respectively), malapposition presence (1.7%, 0.03% and 0 of struts, respectively) and average intimal thickness over struts (76 ± 12 µm, 161 ± 30 µm and 292 ± 29 µm, respectively) were significantly different among different stent groups (all P < 0.001). Conclusions Vessel healing status in STEMI patients is superior after implantation of biodegradable polymer DES than durable polymer DES, while both are inferior to BMS. PMID:27403139

  12. Porous Shape Memory Polymers

    PubMed Central

    Hearon, Keith; Singhal, Pooja; Horn, John; Small, Ward; Olsovsky, Cory; Maitland, Kristen C.; Wilson, Thomas S.; Maitland, Duncan J.

    2013-01-01

    Porous shape memory polymers (SMPs) include foams, scaffolds, meshes, and other polymeric substrates that possess porous three-dimensional macrostructures. Porous SMPs exhibit active structural and volumetric transformations and have driven investigations in fields ranging from biomedical engineering to aerospace engineering to the clothing industry. The present review article examines recent developments in porous SMPs, with focus given to structural and chemical classification, methods of characterization, and applications. We conclude that the current body of literature presents porous SMPs as highly interesting smart materials with potential for industrial use. PMID:23646038

  13. Porous Shape Memory Polymers.

    PubMed

    Hearon, Keith; Singhal, Pooja; Horn, John; Small, Ward; Olsovsky, Cory; Maitland, Kristen C; Wilson, Thomas S; Maitland, Duncan J

    2013-02-04

    Porous shape memory polymers (SMPs) include foams, scaffolds, meshes, and other polymeric substrates that possess porous three-dimensional macrostructures. Porous SMPs exhibit active structural and volumetric transformations and have driven investigations in fields ranging from biomedical engineering to aerospace engineering to the clothing industry. The present review article examines recent developments in porous SMPs, with focus given to structural and chemical classification, methods of characterization, and applications. We conclude that the current body of literature presents porous SMPs as highly interesting smart materials with potential for industrial use.

  14. Bioresorbable ureteral stents from natural origin polymers.

    PubMed

    Barros, Alexandre A; Rita, Ana; Duarte, C; Pires, Ricardo A; Sampaio-Marques, Belém; Ludovico, Paula; Lima, Estevão; Mano, João F; Reis, Rui L

    2015-04-01

    In this work, stents were produced from natural origin polysaccharides. Alginate, gellan gum, and a blend of these with gelatin were used to produce hollow tube (stents) following a combination of templated gelation and critical point carbon dioxide drying. Morphological analysis of the surface of the stents was carried out by scanning electron microscopy. Indwelling time, encrustation, and stability of the stents in artificial urine solution was carried out up to 60 days of immersion. In vitro studies carried out with simulated urine demonstrated that the tubes present a high fluid uptake ability, about 1000%. Despite this, the materials are able to maintain their shape and do not present an extensive swelling behavior. The bioresorption profile was observed to be highly dependent on the composition of the stent and it can be tuned. Complete dissolution of the materials may occur between 14 and 60 days. Additionally, no encrustation was observed within the tested timeframe. The ability to resist bacterial adherence was evaluated with Gram-positive Staphylococcus aureus and two Gram-negatives Escherichia coli DH5 alpha and Klebsiella oxytoca. For K. oxytoca, no differences were observed in comparison with a commercial stent (Biosoft(®) duo, Porges), although, for S. aureus all tested compositions had a higher inhibition of bacterial adhesion compared to the commercial stents. In case of E. coli, the addition of gelatin to the formulations reduced the bacterial adhesion in a highly significant manner compared to the commercial stents. The stents produced by the developed technology fulfill the requirements for ureteral stents and will contribute in the development of biocompatible and bioresorbable urinary stents.

  15. Tricuspid valved stent implantation: novel stent with a self-expandable super-absorbent polymer.

    PubMed

    Iino, Kenji; Lozonschi, Lucian; Metzner, Anja; Marczynski-Bühlow, Martin; Renner, Jochen; Cremer, Jochen; Lutter, Georg

    2011-08-01

    Trans-catheter aortic and pulmonary valve replacement procedures can result in favorable outcomes in selected patients. The aim of this study was to investigate the functioning of a novel self-expanding valved stent with super-absorbent polymer (SAP) for minimally invasive replacement of the tricuspid valve. A newly designed nitinol stent with SAP was specially designed for the tricuspid annulus. This device was composed of right atrial anchoring elements, a left ventricular tubular stent, and a trileaflet bovine pericardial valve. The stent was coated with a waterproof material, and a pouch containing SAP for minimizing paravalvular leakage was placed beneath the atrial element. Seven pigs underwent minimally invasive off-pump tricuspid valved stent implantation. This was performed through a lower ministernotomy using a transventricular approach under transesophageal echocardiographic guidance. After 1 and 6h, a complete echocardiographic evaluation and hemodynamics (Swan-Ganz catheter) were performed. Six of seven pigs exhibited normal hemodynamics immediately after tricuspid valved stent implantation and maintained stability for the entire period of monitoring. In one pig, a part of the atrial stent elements was deployed into the right ventricle, leading to significant paravalvular leakage, and died very soon. All subsequent animals survived with good results in the observation period. Accurate positioning of the valved stent was documented in six of seven pigs. SAP expanded and filled the gap between the stent and the native annulus in all animals. Mild paravalvular leakage was found in two of the six animals. Nevertheless, the observed leakage decreased to trace levels 6h after implantation. In the additional four pigs, only trace tricuspid regurgitation was revealed. No right ventricular outflow tract obstruction was detected. Trans-apical off-pump tricuspid valved stent implantation is feasible in an acute experimental setting, and SAP may help to reduce

  16. Shape memory alloy/shape memory polymer tools

    DOEpatents

    Seward, Kirk P.; Krulevitch, Peter A.

    2005-03-29

    Micro-electromechanical tools for minimally invasive techniques including microsurgery. These tools utilize composite shape memory alloy (SMA), shape memory polymer (SMP) and combinations of SMA and SMP to produce catheter distal tips, actuators, etc., which are bistable. Applications for these structures include: 1) a method for reversible fine positioning of a catheter tip, 2) a method for reversible fine positioning of tools or therapeutic catheters by a guide catheter, 3) a method for bending articulation through the body's vasculature, 4) methods for controlled stent delivery, deployment, and repositioning, and 5) catheters with variable modulus, with vibration mode, with inchworm capability, and with articulated tips. These actuators and catheter tips are bistable and are opportune for in vivo usage because the materials are biocompatible and convenient for intravascular use as well as other minimal by invasive techniques.

  17. Randomized clinical trial comparing abluminal biodegradable polymer sirolimus-eluting stents with durable polymer sirolimus-eluting stents

    PubMed Central

    Zhang, Haijun; Wang, Xiangfei; Deng, Wei; Wang, Shenguo; Ge, Junbo; Toft, Egon

    2016-01-01

    Abstract Background: The biodegradable polymer drug-eluting stents (DES) were developed to improve vascular healing. However, further data and longer-term follow-up are needed to confirm safety and efficacy of these stents. This randomized clinical trial aimed to compare safety and efficacy of 2 sirolimus-eluting stents (SES): Cordimax—a novel abluminal biodegradable polymer SES and Cypher Select—a durable polymer SES, at 9 months angiographic and 5-year clinical follow-up. Methods: We randomized 402 patients with coronary artery disease to percutaneous coronary intervention with Cordimax (n = 202) or Cypher select (n = 200). Angiographic follow-up was performed at 9 months after the index procedure and clinical follow-up annually up to 5 years. The primary endpoint was angiographic in-stent late luminal loss (LLL). Secondary endpoints included angiographic restenosis rate, target vessel revascularization (TVR), and major adverse cardiac events (MACEs; defined as cardiac death, myocardial infarction, or TVR) at 5-year follow-up. Results: Cordimax was noninferior to Cypher select for in-stent LLL (0.25 ± 0.47 vs 0.18 ± 0.49 mm; P = 0.587) and in-stent mean diameter stenosis (22.19 ± 12.21% vs 19.89 ± 10.79%; P = 0.064) at 9 months angiographic follow-up. The MACE rates were not different at 1 year (5.9% vs 4.0%, P = 0.376); however, MACE rates from 2 to 5 years were lower in the Cordimax group (6.8% vs 13.1%; P = 0.039). Conclusion: Abluminal biodegradable polymer SES is noninferior to durable polymer SES at 9-month angiographic and 1-year clinical follow-up. However, MACE rates from 2 to 5 years were less in the abluminal biodegradable polymer group. PMID:27661023

  18. [Numerical modeling of shape memory alloy vascular stent's self-expandable progress and "optimized grid" of stent].

    PubMed

    Xu, Qiang; Liu, Yulan; Wang, Biao; He, Jin

    2008-10-01

    Vascular stent is an important medical appliance for angiocardiopathy. Its key deformation process is the expandable progress of stent in the vessel. The important deformation behaviour corresponds to two mechanics targets: deformation and stress. This paper is devoted to the research and development of vascular stent with proprietary intellectual property rights. The design of NiTinol self-expandable stent is optimized by means of finite element software. ANSYS is used to build the finite element simulation model of vascular stent; the molding material is NiTinol shape memory alloy. To cope with the factors that affect the structure of stent, the shape of grid and so on, the self-expanding process of Nitinol stent is simulated through computer. By making a comparison between two kinds of stents with similar grid structure, we present a new concept of "Optimized Grid" of stent.

  19. The SYNERGY biodegradable polymer everolimus eluting coronary stent: Porcine vascular compatibility and polymer safety study.

    PubMed

    Wilson, Gregory J; Marks, Angela; Berg, Kimberly J; Eppihimer, Michael; Sushkova, Natalia; Hawley, Steve P; Robertson, Kimberly A; Knapp, David; Pennington, Douglas E; Chen, Yen-Lane; Foss, Aaron; Huibregtse, Barbara; Dawkins, Keith D

    2015-11-15

    SYNERGY is a novel platinum chromium alloy stent that delivers abluminal everolimus from an ultrathin poly-lactide-co-glycide (PLGA) biodegradable polymer. This study evaluated the in vivo degradation of the polymer coating, everolimus release time course, and vascular compatibility of the SYNERGY stent. SYNERGY stents were implanted in arteries of domestic swine. Devices were explanted at predetermined time points (up to 120 days) and the extent of PLGA coating or everolimus remaining on the stents was quantified. Everolimus levels in the arterial tissue were also evaluated. A pathological analysis on coronary arteries of single and overlapping stents was performed at time points between 5 and 270 days. PLGA bioabsorption began immediately after implantation, and drug release was essentially complete by 90 days; PLGA absorption was substantially complete by 120 days (>90% of polymer was absorbed) leaving a bare metal SYNERGY stent. Vascular response was similar among SYNERGY and control stents (bare metal, polymer-only, and 3× polymer-only). Mild increases in para-strut fibrin were seen for SYNERGY at an early time point with no significant differences in all other morphological and morphometric parameters through 270 days or endothelial function (eNOS immunostaining) at 90 or 180 days. Inflammation was predominantly minimal to mild for all device types. In a swine model, everolimus was released by 90 days and PLGA bioabsorption was complete shortly thereafter. The SYNERGY stent and its biodegradable polymer, even at a 3× safety margin, demonstrated vascular compatibility similar to bare metal stent controls. © 2015 Wiley Periodicals, Inc.

  20. Intense Inflammatory Reaction to Heparin Polymer Coated Intravascular Palmaz Stents in Porcine Arteries Compared to Uncoated Palmaz Stents

    SciTech Connect

    Goodwin, Scott C.; Yoon, Hyo-Chun; Chen, Gary; Abdel-Sayed, Peter; Costantino, Mary M.; Bonilla, Sheila M.; Nishimura, Earl

    2003-04-15

    The objective of this study was to evaluate the efficacy of heparin-polymer-coated intravascular stents in the reduction of vessel stenosis. Three types of coatings for Palmaz stents were tested: 1) heparin covalently bound to a polyethylene oxide(Hp-PEO) tether; 2) heparin copolymerized with ethylene vinyl acetate(Hp-Elvax) and 3) Elvax alone. Polymer-coated stents and uncoated controls were deployed in the external iliac arteries following endothelial injury in 18 swine. The animals were maintained on anatherogenic diet and examined by angiography at 6 and 12 weeks. The stented segments were then harvested for histopathologic analysis. Both types of heparin-coated stents resulted in increased luminal narrowing as compared to the contralateral uncoated stents. At 6 weeks, average luminal stenosis was 48% for Hp-PEO stents vs 35% for uncoated stents (p < 0.05). At 12 weeks, average luminal stenosis was 36% for Hp-PEO stents vs 26% for uncoated stents(p = NS). For Hp-Elvax stents, the average stenosis was 58% vs 33% for uncoated controls (p <0.05) at 6 weeks and 47% vs 19% for uncoated controls(p < 0.05) at 12 weeks. There was no significant difference between Hp-Elvax stents and Elvax stents(p = NS). Increased luminal narrowing in coated stents was primarily secondary to a marked inflammatory response.Heparin-polyethylene oxide and heparin-ethylene vinyl acetate-coated stents resulted in increased luminal narrowing as compared with uncoated stents, due to a marked inflammatory response.

  1. Histopathological comparison of biodegradable polymer and permanent polymer based sirolimus eluting stents in a porcine model of coronary stent implantation.

    PubMed

    Koppara, Tobias; Joner, Michael; Bayer, Gerd; Steigerwald, Kristin; Diener, Tobias; Wittchow, Eric

    2012-06-01

    Biodegradable stent coatings were recently introduced as a potential solution to overcome sustained inflammatory responses observed with permanent polymer-based drug-eluting stents. In a preliminary study, selected biodegradable or permanent polymer-based sirolimus-eluting stent (SES) formulations were screened for effectiveness in comparison to bare metal stents (BMS) at 28 days. Subsequently, the most favourable SES formulation was compared to commercially available SES (Cypher™) at 28, 90 and 180 days to investigate the histopathologic response as well as tissue, blood and organ pharmacokinetics. Overlapping SES implantation was conducted to evaluate vascular healing at 28 days in this particular setting. SES with biodegradable poly (L-lactide) polymer (PLLA) or poly(lactide-co-glycolide) showed the most favourable outcome with regards to reductions in neointimal area in comparison to BMS at 28 days. The PLLA SES showed a similar reduction in neointimal area compared to Cypher™ at 28 days, with significant greater reductions at 90 and 180 days (1.7 ± 0.7 mm² vs. 3.1 ± 1.5 mm², p=0.03 and 1.8 ± 1.2 mm² vs. 3.0 ± 1.5 mm², p=0.01, respectively). Sirolimus vascular tissue concentrations were detectable up to 90 days following implantation. Overlapping stented segments showed favourable histopathologic results with respect to fibrin deposition and endothelialisation at 28 days. In conclusion, the use of PLLA as drug-eluting matrix resulted in mild inflammatory responses in the presence of effective sirolimus tissue concentrations. The greater efficacy observed at long-term follow-up in PLLA SES compared to Cypher™ may be a multifactorial result of stent design, polymer biocompatibility and improved release kinetics.

  2. Biodegradable-Polymer Biolimus-Eluting Stents versus Durable-Polymer Everolimus-Eluting Stents at One-Year Follow-Up: A Registry-Based Cohort Study.

    PubMed

    Parsa, Ehsan; Saroukhani, Sepideh; Majlessi, Fereshteh; Poorhosseini, Hamidreza; Lofti-Tokaldany, Masoumeh; Jalali, Arash; Salarifar, Mojtaba; Nematipour, Ebrahim; Alidoosti, Mohammad; Aghajani, Hassan; Amirzadegan, Alireza; Kassaian, Seyed Ebrahim

    2016-04-01

    We compared outcomes of percutaneous coronary intervention patients who received biodegradable-polymer biolimus-eluting stents with those who received durable-polymer everolimus-eluting stents. At Tehran Heart Center, we performed a retrospective analysis of the data from January 2007 through December 2011 on 3,270 consecutive patients with coronary artery disease who underwent percutaneous coronary intervention with the biodegradable-polymer biolimus-eluting stent or the durable-polymer everolimus-eluting stent. We excluded patients with histories of coronary artery bypass grafting or percutaneous coronary intervention, acute ST-segment-elevation myocardial infarction, or the implantation of 2 different stent types. Patients were monitored for 12 months. The primary endpoint was a major adverse cardiac event, defined as a composite of death, nonfatal myocardial infarction, and target-vessel and target-lesion revascularization. Durable-polymer everolimus-eluting stents were implanted in 2,648 (81%) and biodegradable-polymer biolimus-eluting stents in 622 (19%) of the study population. There was no significant difference between the 2 groups (2.7% vs 2.7%; P=0.984) in the incidence of major adverse cardiac events. The cumulative adjusted probability of major adverse cardiac events in the biodegradable-polymer biolimus-eluting stent group did not differ from that of such events in the durable-polymer everolimus-eluting stent group (hazard ratio=0.768; 95% confidence interval, 0.421-1.44; P=0.388). We conclude that in our patients the biodegradable-polymer biolimus-eluting stent was as effective and safe, during the 12-month follow-up period, as was the durable-polymer everolimus-eluting stent.

  3. Finite element modeling of a progressively expanding shape memory stent.

    PubMed

    Thériault, Philippe; Terriault, Patrick; Brailovski, Vladimir; Gallo, Richard

    2006-01-01

    Cardiovascular stents are small cylindrical devices introduced in stenosed arteries to reopen the lumen and restore blood flow. However, this treatment presents complications, including restenosis, which is the reclosing of the artery's diameter after the insertion of a stent. The structure of the prosthesis penetrates into and injures the walls of the patient's artery. There then follows a proliferation of cells and the formation of scar tissue around the injury, similar to the scarring of other organic tissues. This reaction to the trauma subjects the artery to close. The proposed solution is to develop a Nitinol stent with a progressive expansion device made of polyethylene, allowing smooth and gradual contact between the stent and the artery's wall by creep effect. The purpose of this paper is to describe the technology and methodology for the numerical study of this kind of stent through the finite element method. ANSYS 8.0 software is used to perform the analysis. The Nitinol is modeled with a superelastic law and the polyethylene with a yield hardening law. A first simulation determines the final geometry of the stent laser cut from a small tube. A second simulation examines the behavior of the prosthesis during surgery and over the 4 weeks following the operation. The results demonstrate that a compromise can be reached between a limited expansion prior the inflation of the expandable balloon and a significant expansion by creep of the polymer rings.

  4. Stent thrombosis with biodegradable polymer drug-eluting stents versus durable polymer sirolimus-eluting stents: an update meta-analysis.

    PubMed

    Zhu, Lin; Lv, Yi Ning; Wang, Li Yu

    2015-01-01

    Durable polymer sirolimus-eluting stents (DP-SES) are associated with a low risk of stent thrombosis; biodegradable polymer drug-eluting stents (BP-DES) were designed to reduce these risks. However, their benefits are still variable. We undertook a meta-analysis of randomized trials identified by systematic searches of Medline, Embase, and the Cochrane Database. Eleven studies (9,676 patients) with a mean follow-up of 22.6 months were included. Overall, compared with DP-SES, BP-DES significantly lowered the rate of definite or probable stent thrombosis (RR, 0.73; 95% CI, 0.55-0.97; p = 0.03; I(2) = 0.0%) due to a decreased risk of very late stent thrombosis (RR, 0.26; 95% CI, 0.11-0.63; p = 0.00; I(2) = 0.0%). However, BP-DES were associated with a comparable rate of early and late stent thrombosis. Meanwhile, BP-DES were associated with a broadly equivalent risk of target vessel revascularization (RR, 0.90; 95% CI, 0.78-1.03; p = 0.13; I(2) = 0.0%), cardiac death (RR, 0.89; 95% CI, 0.72-1.09; p = 0.24; I(2) = 0.0%), myocardial infarction (RR, 1.03; 95% CI, 0.84-1.26; p = 0.79; I(2) = 0.0%), and major adverse cardiac events (MACE; RR, 0.91; 95% CI, 0.83-1.0; p = 0.08; I(2) = 0.0%). Furthermore, angiographic data showed that in-stent and in-segment late luminal loss were similar between the two groups. Compared with DP-SES, BP-DES were associated with a lower rate of very late stent thrombosis and an equivalent risk of MACE. Larger randomized studies are needed to confirm this finding.

  5. Applications of memory alloy stent in vertebral fractures

    PubMed Central

    Yimin, Yang; Zhi, Zhang; ZhiWei, Ren; Wei, Ma; Jha, Rajiv Kumar

    2014-01-01

    Background The aim of this study was to evaluate the feasibility of treating vertebral compression fractures using an autonomously developed nitinol memory alloy vertebral stent. Material/Methods Thoracolumbar vertebral specimens from adult human cadavers were made into models of compression fractures. The models were divided into group A, which received percutaneous kyphoplasty (PKP), balloon dilation, and nitinol memory alloy vertebral stent implantation (PKP + nitinol stent group); group B, which received percutaneous vertebroplasty (PVP) and direct implantation of a nitinol memory alloy vertebral stent (PVP + nitinol stent group); and group C, which received PKP, balloon dilation, and bone cement vertebroplasty (PKP + polymethylmethacrylate (PMMA) group). Vertebral heights were measured before and after the surgery and the water bath incubation to compare the impact of the 3 different surgical approaches on reducing vertebral compression. Results The 3 surgical groups could all significantly restore the heights of compressed vertebral bodies. The vertebral heights of the PKP + nitinol stent group, PVP + nitinol stent group, and PKP + PMMA group were changed from the preoperative levels of (1.59±0.08) cm, (1.68±0.08) cm, and (1.66±0.11) cm to the postoperative levels of (2.00±0.09) cm, (1.87±0.04) cm, and (1.99±0.09) cm, respectively. After the water bath, the vertebral heights of each group were changed to (2.10±0.07) cm, (1.98±0.09) cm, and (2.00±0.10) cm, respectively. Pairwise comparison of the differences between the preoperative and postoperative vertebral heights showed that group A and group B differed significantly (P=0.000); group B and group C differed significantly (P=0.003); and group A and group C had no significant difference (P=0.172). Pairwise comparison of the differences in the vertebral heights before and after the water bath showed that group A and group C differed significantly (P=0.000); group B and group C differed significantly

  6. First-in-man use of polymer-free valsartan-eluting stents in small coronary vessels: a comparison to polymer-free rapamycin (2%)-eluting stents.

    PubMed

    Peters, Stefan; Behnisch, Boris; Heilmann, Torsten; Richter, Christian

    2009-06-01

    Orally administered angiotensin receptor antagonists administered after bare-metal stent implantation and even after drug-eluting stent implantation seem to lower in-stent restenosis rates.Whether valsartan-eluting stents are similarly effective was tested here in a first-in-man trial. The efficacy of a polymer-free drug-eluting stent coated with 300 mcg valsartan was compared to a coating with a 2% rapamycin solution in small (stent system (Translumina GmbH, Hechingen, Germany). Fifteen patients (eight males, mean age 64.4+/-7.7 years) were treated with YUKON Choice valsartan-eluting stents and 30 patients (24 males, mean age 65.7+/-8.4 years) received YUKON Choice rapamycin-eluting stents. Clopidogrel was given for six months in all patients. Within the first 30 days, no adverse events occurred in either group. Binary in-stent restenosis rate was 30.8% (four in 13 angiographic controls) in the valsartan-eluting stent group and 35.0% (eight in 20 angiographic controls) in the rapamycin-eluting YUKON Choice stent group. Mean late lumen loss was 0.78+/-0.53 mm and 0.79+/-0.58 mm, respectively. Target lesion and target vessel revascularisation rate was 26.6% and 25.0%, respectively. No restenoses in rapamycin-eluting YUKON Choice stents appeared in 12 patients with adjunct oral valsartan administration. If polymer-free YUKON Choice stents are used in small vessels, valsartan-eluting stents show an identical efficacy as rapamycin-loaded stents. In patients with rapamycin-eluting YUKON Choice stents it seems that the efficacy can be increased by oral valsartan administration.

  7. A new polymer-free drug-eluting stent with nanocarriers eluting sirolimus from stent-plus-balloon compared with bare-metal stent and with biolimus A9 eluting stent in porcine coronary arteries

    PubMed Central

    Galon, Micheli Z.; Gutierrez, Paulo S.; Sojitra, Prakash; Vyas, Ashwin; Doshi, Manish; Lemos, Pedro A.

    2015-01-01

    Background Permanent polymers in first generation drug-eluting stent (DES) have been imputed to be a possible cause of persistent inflammation, remodeling, malapposition and late stent thrombosis. We aim to describe the in vivo experimental result of a new polymer-free DES eluting sirolimus from stent-plus-balloon (Focus np stent, Envision Scientific) compared with a bare-metal stent (BMS) (Amazonia CroCo, Minvasys) and with a biolimus A9 eluting stent (Biomatrix, Biosensors). Methods In 10 juvenile pigs, 23 coronary stents were implanted in the coronary arteries (8 Amazonia CroCo, 8 Focus np, and 7 Biomatrix). At 28-day follow-up, optical coherence tomography (OCT) and histology were used to evaluate neointimal hyperplasia and healing response. Results According to OCT analysis, Focus np stents had a greater lumen area and less neointimal hyperplasia response than BMS and Biomatrix had. Histomorphometry results showed less neointimal hyperplasia in Focus np than in BMS. Histology showed a higher fibrin deposition in Biomatrix stent compared to Focus np and BMS. Conclusions The new polymer-free DES with sirolimus eluted from stent-plus-balloon demonstrated safety and reduced neointimal proliferation compared with the BMS and Biomatrix stents at 28-day follow-up in this porcine coronary model. This new polymer-free DES is promising and warrants further clinical studies. PMID:25984451

  8. Ultrathin, bioresorbable polymer sirolimus-eluting stents versus thin, durable polymer everolimus-eluting stents in patients undergoing coronary revascularisation (BIOFLOW V): a randomised trial.

    PubMed

    Kandzari, David E; Mauri, Laura; Koolen, Jacques J; Massaro, Joseph M; Doros, Gheorghe; Garcia-Garcia, Hector M; Bennett, Johan; Roguin, Ariel; Gharib, Elie G; Cutlip, Donald E; Waksman, Ron

    2017-08-25

    The development of coronary drug-eluting stents has included use of new metal alloys, changes in stent architecture, and use of bioresorbable polymers. Whether these advancements improve clinical safety and efficacy has not been shown in previous randomised trials. We aimed to examine the clinical outcomes of a bioresorbable polymer sirolimus-eluting stent compared with a durable polymer everolimus-eluting stent in a broad patient population undergoing percutaneous coronary intervention. BIOFLOW V was an international, randomised trial done in patients undergoing elective and urgent percutaneous coronary intervention in 90 hospitals in 13 countries (Australia, Belgium, Canada, Denmark, Germany, Hungary, Israel, the Netherlands, New Zealand, South Korea, Spain, Switzerland, and the USA). Eligible patients were those aged 18 years or older with ischaemic heart disease undergoing planned stent implantation in de-novo, native coronary lesions. Patients were randomly assigned (2:1) to either an ultrathin strut (60 μm) bioresorbable polymer sirolimus-eluting stent or to a durable polymer everolimus-eluting stent. Randomisation was via a central web-based data capture system (mixed blocks of 3 and 6), and stratified by study site. The primary endpoint was 12-month target lesion failure. The primary non-inferiority comparison combined these data from two additional randomised trials of bioresorbable polymer sirolimus-eluting stent and durable polymer everolimus-eluting stent with Bayesian methods. Analysis was by intention to treat. The trial is registered with ClinicalTrials.gov, number NCT02389946. Between May 8, 2015, and March 31, 2016, 4772 patients were recruited into the study. 1334 patients met inclusion criteria and were randomly assigned to treatment with bioresorbable polymer sirolimus-eluting stents (n=884) or durable polymer everolimus-eluting stents (n=450). 52 (6%) of 883 patients in the bioresorbable polymer sirolimus-eluting stent group and 41 (10%) of

  9. Comparison of endothelium-dependent and -independent vasomotor response after abluminal biodegradable polymer biolimus-eluting stent and persistent polymer everolimus-eluting stent implantation (COMPARE-IT).

    PubMed

    Puricel, Serban; Kallinikou, Zacharenia; Espinola, Jaqueline; Arroyo, Diego; Goy, Jean-Jacques; Stauffer, Jean-Christophe; Baeriswyl, Gérard; Smits, Pieter Cornelis; Cook, Stéphane; Togni, Mario

    2016-01-01

    Drug-eluting stents (DES) have been associated with local endothelial dysfunction in the segments proximal and distal to the stent (peristent segments) and increased thrombotic risk in long term follow-up. Little data exists on endothelial function post-implantation of new DES with biodegradable polymer. The aim of our study was to compare the local endothelial function assessed by exercise induced coronary vasomotion after implantation of a biolimus A9-eluting stent with biodegradable polymer (BES) with an everolimus-eluting stent with durable polymer (EES). Coronary vasomotion was evaluated with quantitative coronary angiography at rest and during supine bicycle exercise in nine patients with EES and thirteen patients with BES, 16 months after stent implantation. Mean luminal diameter of the stent, peristent segments, and of a control vessel were determined at rest, during exercise, and after the administration of nitroglycerine. The control vessel showed exercise-induced vasodilatation in both groups (EES: +6.4±5.5%, p=0.07; BES: +7.8±10.1%, p=0.07). Vasomotion in the stented vessel segment was abolished. There was exercise-induced vasoconstriction in both groups in the segments proximal (EES: -9.6±4.5%; p=0.03; BES: -4.3±5.4%, p=0.02) and distal to the stent (EES: -3.2±9.3%; p=0.41, BES -8.6±8.0%, p<0.01). Sublingual nitroglycerin was associated with maximal vasodilatation of the peristent segments in both groups. Alike DES with durable polymer, stents with a biodegradable polymer are associated with exercise-induced paradoxical coronary vasoconstriction of the peristent segments. This data suggests that endothelial dysfunction after DES implantation is not primarily caused by the durability of the polymer coating. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  10. Unconstrained Recovery Characterization of Shape-Memory Polymer Networks for Cardiovascular Applications

    PubMed Central

    Yakacki, Christopher M.; Shandas, Robin; Lanning, Craig; Rech, Bryan; Eckstein, Alex; Gall, Ken

    2009-01-01

    Shape-memory materials have been proposed in biomedical device design due to their ability to facilitate minimally invasive surgery and recover to a predetermined shape in-vivo. Use of the shape-memory effect in polymers is proposed for cardiovascular stent interventions to reduce the catheter size for delivery and offer highly controlled and tailored deployment at body temperature. Shape-memory polymer networks were synthesized via photopolymerization of tert-butyl acrylate and poly (ethylene glycol) dimethacrylate to provide precise control over the thermomechanical response of the system. The free recovery response of the polymer stents at body temperature was studied as a function of glass transition temperature (Tg), crosslink density, geometrical perforation, and deformation temperature, all of which can be independently controlled. Room temperature storage of the stents was shown to be highly dependent on Tg and crosslink density. The pressurized response of the stents is also demonstrated to depend on crosslink density. This polymer system exhibits a wide range of shape-memory and thermomechanical responses to adapt and meet specific needs of minimally invasive cardiovascular devices. PMID:17296222

  11. No country for old stents? Improving long-term patient outcomes with biodegradable polymer drug-eluting stents.

    PubMed

    Byrne, Robert A; Kastrati, Adnan

    2012-04-01

    Biodegradable polymer-coated drug-eluting stents (DESs) represent an attractive approach to improve vascular healing after coronary intervention. The proof-of-concept chain of investigation includes preclinical safety assessment, surrogate end point clinical efficacy studies and large-scale clinical outcome studies, in which noninferiority against benchmark devices is assessed at 12 months, with adjudication of hypothesized clinical advantage at long-term follow-up. The 4-year outcome data from large-scale trials such as the LEADERS study represents a final link in this process. Data from this trial show maintenance of noninferiority and an overall improvement in the composite of death, myocardial infarction and revascularization with biodegradable polymer DESs versus durable polymer sirolimus-eluting stents that is statistically significant and perhaps also clinically important (risk ratio: 0.81; 95% CI: 0.66-1.00; p-value for superiority = 0.05). Furthermore, although reductions in the incidence of stent thrombosis with biodegradable polymer stents at 4 years did not reach statistical significance, in keeping with the hypothesized mechanism of benefit, the observed risk differences seemed to be driven by a reduction in very late events beyond 1 year after intervention. These findings are backed up by those from a pooled analysis of the three largest biodegradable polymer DES randomized trials. With the availability of high-quality biodegradable polymer devices and the phasing out of earlier generation devices, the next 5 years will see increasing uptake of this therapy in routine practice. Whether improvements in outcomes with biodegradable polymer DESs can also be demonstrated against second-generation durable polymer stents is the subject of a number of ongoing clinical trials.

  12. Post polymerization cure shape memory polymers

    DOEpatents

    Wilson, Thomas S; Hearon, Michael Keith; Bearinger, Jane P

    2014-11-11

    This invention relates to chemical polymer compositions, methods of synthesis, and fabrication methods for devices regarding polymers capable of displaying shape memory behavior (SMPs) and which can first be polymerized to a linear or branched polymeric structure, having thermoplastic properties, subsequently processed into a device through processes typical of polymer melts, solutions, and dispersions and then crossed linked to a shape memory thermoset polymer retaining the processed shape.

  13. Post polymerization cure shape memory polymers

    DOEpatents

    Wilson, Thomas S.; Hearon, II, Michael Keith; Bearinger, Jane P.

    2017-01-10

    This invention relates to chemical polymer compositions, methods of synthesis, and fabrication methods for devices regarding polymers capable of displaying shape memory behavior (SMPs) and which can first be polymerized to a linear or branched polymeric structure, having thermoplastic properties, subsequently processed into a device through processes typical of polymer melts, solutions, and dispersions and then crossed linked to a shape memory thermoset polymer retaining the processed shape.

  14. Impact of polymer formulations on neointimal proliferation after zotarolimus-eluting stent with different polymers: insights from the RESOLUTE trial.

    PubMed

    Waseda, Katsuhisa; Ako, Junya; Yamasaki, Masao; Koizumi, Tomomi; Sakurai, Ryota; Hongo, Yoichiro; Koo, Bon-Kwon; Ormiston, John; Worthley, Stephen G; Whitbourn, Robert J; Walters, Darren L; Meredith, Ian T; Fitzgerald, Peter J; Honda, Yasuhiro

    2011-06-01

    Polymer formulation may affect the efficacy of drug-eluting stents. Resolute, Endeavor, and ZoMaxx are zotarolimus-eluting stents with different stent platforms and different polymer coatings and have been tested in clinical trials. The aim of this analysis was to compare the efficacy of zotarolimus-eluting stents with different polymers. Data were obtained from the first-in man trial or first randomized trials of each stent, The Clinical RESpOnse EvaLUation of the MedTronic Endeavor CR ABT-578 Eluting Coronary Stent System in De Novo Native Coronary Artery Lesions (RESOLUTE), Randomized Controlled Trial to Evaluate the Safety and Efficacy of the Medtronic AVE ABT-578 Eluting Driver Coronary Stent in De Novo Native Coronary Artery Lesions (ENDEAVOR II), and ZoMaxx I trials. Follow-up intravascular ultrasound analyses (8 to 9 months of follow-up) were possible in 353 patients (Resolute: 88, Endeavor: 98, ZoMaxx: 82, Driver: 85). Volume index (volume/stent length) was obtained for vessel, stent, lumen, peristent plaque, and neointima. Cross-sectional narrowing was defined as neointimal area divided by stent area (%). Neointima-free frame ratio was calculated as the number of frames without intravascular ultrasound-detectable neointima divided by the total number of frames within the stent. At baseline, vessel, lumen, and peristent plaque volume index were not significantly different among the 4 stent groups. At follow-up, percent neointimal obstruction was significantly lower in Resolute compared with Endeavor, ZoMaxx, and Driver (Resolute: 3.7±4.0, Endeavor: 17.5±10.1, ZoMaxx: 14.6±8.1, Driver: 29.4±17.2%; P<0.001). Greater maximum cross-sectional narrowing and higher neointima-free frame ratio, suggesting less neointimal coverage, were observed in Resolute compared with other stent groups. Multiple regression analysis confirmed that the biodurable polymer used in Resolute independently correlated with neointimal suppression among 3 zotarolimus-eluting stents

  15. Optimization of Cardiovascular Stent against Restenosis: Factorial Design-Based Statistical Analysis of Polymer Coating Conditions

    PubMed Central

    Acharya, Gayathri

    2012-01-01

    The objective of this study was to optimize the physicodynamic conditions of polymeric system as a coating substrate for drug eluting stents against restenosis. As Nitric Oxide (NO) has multifunctional activities, such as regulating blood flow and pressure, and influencing thrombus formation, a continuous and spatiotemporal delivery of NO loaded in the polymer based nanoparticles could be a viable option to reduce and prevent restenosis. To identify the most suitable carrier for S-Nitrosoglutathione (GSNO), a NO prodrug, stents were coated with various polymers, such as poly (lactic-co-glycolic acid) (PLGA), polyethylene glycol (PEG) and polycaprolactone (PCL), using solvent evaporation technique. Full factorial design was used to evaluate the effects of the formulation variables in polymer-based stent coatings on the GSNO release rate and weight loss rate. The least square regression model was used for data analysis in the optimization process. The polymer-coated stents were further assessed with Differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy analysis (FTIR), Scanning electron microscopy (SEM) images and platelet adhesion studies. Stents coated with PCL matrix displayed more sustained and controlled drug release profiles than those coated with PLGA and PEG. Stents coated with PCL matrix showed the least platelet adhesion rate. Subsequently, stents coated with PCL matrix were subjected to the further optimization processes for improvement of surface morphology and enhancement of the drug release duration. The results of this study demonstrated that PCL matrix containing GSNO is a promising system for stent surface coating against restenosis. PMID:22937015

  16. Shape memory polymer actuator and catheter

    SciTech Connect

    Maitland, Duncan J.; Lee, Abraham P.; Schumann, Daniel L.; Matthews, Dennis L.; Decker, Derek E.; Jungreis, Charles A.

    2007-11-06

    An actuator system is provided for acting upon a material in a vessel. The system includes an optical fiber and a shape memory polymer material operatively connected to the optical fiber. The shape memory polymer material is adapted to move from a first shape for moving through said vessel to a second shape where it can act upon said material.

  17. Shape memory polymer actuator and catheter

    SciTech Connect

    Maitland, Duncan J.; Lee, Abraham P.; Schumann, Daniel L.; Matthews, Dennis L.; Decker, Derek E.; Jungreis, Charles A.

    2004-05-25

    An actuator system is provided for acting upon a material in a vessel. The system includes an optical fiber and a shape memory polymer material operatively connected to the optical fiber. The shape memory polymer material is adapted to move from a first shape for moving through said vessel to a second shape where it can act upon said material.

  18. Fabrication of a Delaying Biodegradable Magnesium Alloy-Based Esophageal Stent via Coating Elastic Polymer

    PubMed Central

    Yuan, Tianwen; Yu, Jia; Cao, Jun; Gao, Fei; Zhu, Yueqi; Cheng, Yingsheng; Cui, Wenguo

    2016-01-01

    Esophageal stent implantation can relieve esophageal stenosis and obstructions in benign esophageal strictures, and magnesium alloy stents are a good candidate because of biodegradation and biological safety. However, biodegradable esophageal stents show a poor corrosion resistance and a quick loss of mechanical support in vivo. In this study, we chose the elastic and biodegradable mixed polymer of Poly(ε-caprolactone) (PCL) and poly(trimethylene carbonate) (PTMC) as the coated membrane on magnesium alloy stents for fabricating a fully biodegradable esophageal stent, which showed an ability to delay the degradation time and maintain mechanical performance in the long term. After 48 repeated compressions, the mechanical testing demonstrated that the PCL-PTMC-coated magnesium stents possess good flexibility and elasticity, and could provide enough support against lesion compression when used in vivo. According to the in vitro degradation evaluation, the PCL-PTMC membrane coated on magnesium was a good material combination for biodegradable stents. During the in vivo evaluation, the proliferation of the smooth muscle cells showed no signs of cell toxicity. Histological examination revealed the inflammation scores at four weeks in the magnesium-(PCL-PTMC) stent group were similar to those in the control group (p > 0.05). The α-smooth muscle actin layer in the media was thinner in the magnesium-(PCL-PTMC) stent group than in the control group (p < 0.05). Both the epithelial and smooth muscle cell layers were significantly thinner in the magnesium-(PCL-PTMC) stent group than in the control group. The stent insertion was feasible and provided reliable support for at least four weeks, without causing severe injury or collagen deposition. Thus, this stent provides a new stent for the treatment of benign esophageal stricture and a novel research path in the development of temporary stents in other cases of benign stricture. PMID:28773505

  19. Fabrication of a Delaying Biodegradable Magnesium Alloy-Based Esophageal Stent via Coating Elastic Polymer.

    PubMed

    Yuan, Tianwen; Yu, Jia; Cao, Jun; Gao, Fei; Zhu, Yueqi; Cheng, Yingsheng; Cui, Wenguo

    2016-05-17

    Esophageal stent implantation can relieve esophageal stenosis and obstructions in benign esophageal strictures, and magnesium alloy stents are a good candidate because of biodegradation and biological safety. However, biodegradable esophageal stents show a poor corrosion resistance and a quick loss of mechanical support in vivo. In this study, we chose the elastic and biodegradable mixed polymer of Poly(ε-caprolactone) (PCL) and poly(trimethylene carbonate) (PTMC) as the coated membrane on magnesium alloy stents for fabricating a fully biodegradable esophageal stent, which showed an ability to delay the degradation time and maintain mechanical performance in the long term. After 48 repeated compressions, the mechanical testing demonstrated that the PCL-PTMC-coated magnesium stents possess good flexibility and elasticity, and could provide enough support against lesion compression when used in vivo. According to the in vitro degradation evaluation, the PCL-PTMC membrane coated on magnesium was a good material combination for biodegradable stents. During the in vivo evaluation, the proliferation of the smooth muscle cells showed no signs of cell toxicity. Histological examination revealed the inflammation scores at four weeks in the magnesium-(PCL-PTMC) stent group were similar to those in the control group (p > 0.05). The α-smooth muscle actin layer in the media was thinner in the magnesium-(PCL-PTMC) stent group than in the control group (p < 0.05). Both the epithelial and smooth muscle cell layers were significantly thinner in the magnesium-(PCL-PTMC) stent group than in the control group. The stent insertion was feasible and provided reliable support for at least four weeks, without causing severe injury or collagen deposition. Thus, this stent provides a new stent for the treatment of benign esophageal stricture and a novel research path in the development of temporary stents in other cases of benign stricture.

  20. Randomized clinical trial comparing abluminal biodegradable polymer sirolimus-eluting stents with durable polymer sirolimus-eluting stents: Nine months angiographic and 5-year clinical outcomes.

    PubMed

    Zhang, Haijun; Wang, Xiangfei; Deng, Wei; Wang, Shenguo; Ge, Junbo; Toft, Egon

    2016-09-01

    The biodegradable polymer drug-eluting stents (DES) were developed to improve vascular healing. However, further data and longer-term follow-up are needed to confirm safety and efficacy of these stents. This randomized clinical trial aimed to compare safety and efficacy of 2 sirolimus-eluting stents (SES): Cordimax-a novel abluminal biodegradable polymer SES and Cypher Select-a durable polymer SES, at 9 months angiographic and 5-year clinical follow-up. We randomized 402 patients with coronary artery disease to percutaneous coronary intervention with Cordimax (n = 202) or Cypher select (n = 200). Angiographic follow-up was performed at 9 months after the index procedure and clinical follow-up annually up to 5 years. The primary endpoint was angiographic in-stent late luminal loss (LLL). Secondary endpoints included angiographic restenosis rate, target vessel revascularization (TVR), and major adverse cardiac events (MACEs; defined as cardiac death, myocardial infarction, or TVR) at 5-year follow-up. Cordimax was noninferior to Cypher select for in-stent LLL (0.25 ± 0.47 vs 0.18 ± 0.49 mm; P = 0.587) and in-stent mean diameter stenosis (22.19 ± 12.21% vs 19.89 ± 10.79%; P = 0.064) at 9 months angiographic follow-up. The MACE rates were not different at 1 year (5.9% vs 4.0%, P = 0.376); however, MACE rates from 2 to 5 years were lower in the Cordimax group (6.8% vs 13.1%; P = 0.039). Abluminal biodegradable polymer SES is noninferior to durable polymer SES at 9-month angiographic and 1-year clinical follow-up. However, MACE rates from 2 to 5 years were less in the abluminal biodegradable polymer group.

  1. Biodegradable-polymer drug-eluting stents vs. bare metal stents vs. durable-polymer drug-eluting stents: a systematic review and Bayesian approach network meta-analysis.

    PubMed

    Kang, Si-Hyuck; Park, Kyung Woo; Kang, Do-Yoon; Lim, Woo-Hyun; Park, Kyung Taek; Han, Jung-Kyu; Kang, Hyun-Jae; Koo, Bon-Kwon; Oh, Byung-Hee; Park, Young-Bae; Kandzari, David E; Cohen, David J; Hwang, Seung-Sik; Kim, Hyo-Soo

    2014-05-01

    The aim of this study was to compare the safety and efficacy of biodegradable-polymer (BP) drug-eluting stents (DES), bare metal stents (BMS), and durable-polymer DES in patients undergoing coronary revascularization, we performed a systematic review and network meta-analysis using a Bayesian framework. Study stents included BMS, paclitaxel-eluting (PES), sirolimus-eluting (SES), endeavor zotarolimus-eluting (ZES-E), cobalt-chromium everolimus-eluting (CoCr-EES), platinium-chromium everolimus-eluting (PtCr-EES), resolute zotarolimus-eluting (ZES-R), and BP biolimus-eluting stents (BP-BES). After a systematic electronic search, 113 trials with 90 584 patients were selected. The principal endpoint was definite or probable stent thrombosis (ST) defined according to the Academic Research Consortium within 1 year. Biodegradable polymer-biolimus-eluting stents [OR, 0.56; 95% credible interval (CrI), 0.33-0.90], SES (OR, 0.53; 95% CrI, 0.38-0.73), CoCr-EES (OR, 0.34; 95% CrI, 0.23-0.52), and PtCr-EES (OR, 0.31; 95% CrI, 0.10-0.90) were all superior to BMS in terms of definite or probable ST within 1 year. Cobalt-chromium everolimus-eluting stents demonstrated the lowest risk of ST of all stents at all times after stent implantation. Biodegradable polymer-biolimus-eluting stents was associated with a higher risk of definite or probable ST than CoCr-EES (OR, 1.72; 95% CrI, 1.04-2.98). All DES reduced the need for repeat revascularization, and all but PES reduced the risk of myocardial infarction compared with BMS. All DESs but PES and ZES-E were superior to BMS in terms of ST within 1 year. Cobalt-chromium everolimus-eluting stents was safer than any DES even including BP-BES. Our results suggest that not only the biodegradability of polymer, but the optimal combination of stent alloy, design, strut thickness, polymer, and drug all combined determine the safety of DES.

  2. Angioscopic assessment of arterial repair following biodegradable polymer-coated biolimus A9-eluting stent implantation. - Comparison with durable polymer-coated sirolimus-eluting stent-.

    PubMed

    Awata, Masaki; Uematsu, Masaaki; Sera, Fusako; Ishihara, Takayuki; Watanabe, Tetsuya; Fujita, Masashi; Onishi, Toshinari; Iida, Osamu; Ishida, Yoshio; Nanto, Shinsuke; Nagata, Seiki

    2011-01-01

    Second-generation drug-eluting stents (DES) are expected to show better arterial repair than older DES. We angioscopically compared the biodegradable polymer-coated biolimus A9-eluting stent (BES) and durable polymer-coated sirolimus-eluting stent (SES) to explore differences in arterial repair. Angioscopy was performed 9 ± 1 months after 15 BES and 16 SES were implanted initially in the native coronary artery. Heterogeneity of neointimal coverage (NIC) as well as the dominant NIC grade was examined. NIC was defined as: grade 0 = fully visible struts; grade 1 = struts bulging into the lumen, but covered; grade 2 = embedded, but translucent struts; grade 3 = invisible struts. Heterogeneity was judged when the NIC grade varied ≥ 1. In-stent late loss (0.06 ± 0.23 vs. 0.07 ± 0.18 mm, P = 0.80), and dominant NIC grade (1.5 ± 0.8 vs. 1.3 ± 0.7, P = 0.45) were similar for BES and SES. Within the stents, NIC was more heterogeneous in SES than in BES (P = 0.035). 80% of BES showed homogeneous NIC, while 56% of SES had heterogeneous NIC. BES showed limited late loss similar to that for SES. Nonetheless, the NIC with BES was more homogeneous than that with SES. Biodegradable polymer-coated BES may have an advantage in homogeneous NIC.

  3. Resistively heated shape memory polymer device

    DOEpatents

    Marion, III, John E.; Bearinger, Jane P.; Wilson, Thomas S.; Maitland, Duncan J.

    2016-10-25

    A resistively heated shape memory polymer device is made by providing a rod, sheet or substrate that includes a resistive medium. The rod, sheet or substrate is coated with a first shape memory polymer providing a coated intermediate unit. The coated intermediate unit is in turn coated with a conductive material providing a second intermediate unit. The second coated intermediate unit is in turn coated with an outer shape memory polymer. The rod, sheet or substrate is exposed and an electrical lead is attached to the rod, sheet or substrate. The conductive material is exposed and an electrical lead is attached to the conductive material.

  4. Long-Term Clinical Outcomes of a Biodegradable Polymer-Based Biolimus-Eluting Stent.

    PubMed

    Im, Eui; Kim, Gwang-Sil; Shin, Dong-Ho; Kim, Jung-Sun; Kim, Byeong-Keuk; Ko, Young-Guk; Choi, Donghoon; Jang, Yangsoo; Hong, Myeong-Ki

    2016-04-01

    To investigate the long-term clinical outcomes of biolimus-eluting stents with biodegradable polymers in real-world clinical practice. Long-term clinical outcomes of biolimus-eluting stents have not been clearly established. A total of 824 all-comer patients (971 lesions) treated with unrestricted implantation of a biolimus-eluting stent with a biodegradable polymer were prospectively enrolled. Patients were divided into complex (413 patients) versus noncomplex (411 patients) groups according to the complexity of coronary lesions. Long-term clinical outcomes for stent efficacy (target lesion revascularization) and safety (composite of cardiac death, target lesion-related myocardial infarction, and definite or probable stent thrombosis) were compared between the two groups during 5 years of follow-up. The complex group showed higher rates of decreased left ventricular ejection fraction, impaired renal function, previous history of myocardial infarction, and diabetes mellitus compared to the noncomplex group. In the overall population, the 5-year cumulative rate of target lesion revascularization was 4.8% (8.3% in the complex group vs 1.6% in the noncomplex group, P < 0.001). For stent safety, the 5-year cumulative rate for a composite of cardiac death, target lesion-related myocardial infarction, and stent thrombosis was 2.5% overall (3.9% in the complex group vs 1.1% in the noncomplex group, P = 0.010). Overall 5-year cumulative rate of stent thrombosis was 0.4% (0.5% in the complex vs 0.2% in the noncomplex group, P = 0.561) with no very late stent thrombosis (VLST). Biodegradable polymer-based biolimus-eluting stents showed favorable efficacy and safety in all-comer patients during 5 years of follow-up. © 2016, Wiley Periodicals, Inc.

  5. Randomized comparison of a polymer-free sirolimus-eluting stent versus a polymer-based paclitaxel-eluting stent in patients with diabetes mellitus: the LIPSIA Yukon trial.

    PubMed

    Desch, Steffen; Schloma, Denis; Möbius-Winkler, Sven; Erbs, Sandra; Gielen, Stephan; Linke, Axel; Yu, Jiangtao; Lauer, Bernward; Kleinertz, Klaus; Dänschel, Wilfried; Schuler, Gerhard; Thiele, Holger

    2011-04-01

    The objective of the study was to assess noninferiority of the polymer-free sirolimus-eluting Yukon Choice stent (Translumina GmbH, Hechingen, Germany) compared with the polymer-based Taxus Liberté stent (Boston Scientific, Natick, Massachusetts) with regard to the primary endpoint, in-stent late lumen loss, at 9 months in patients with diabetes mellitus. The Yukon Choice stent has been evaluated in several randomized controlled trials before, albeit to date, there has been no trial that exclusively enrolled patients with diabetes mellitus. Patients with diabetes mellitus undergoing percutaneous coronary intervention for clinically significant de novo coronary artery stenosis were randomized 1:1 to receive either the polymer-free sirolimus-eluting Yukon Choice stent or the polymer-based paclitaxel-eluting Taxus Liberté stent. A total of 240 patients were randomized. Quantitative coronary angiography was available for 79% of patients. Mean in-stent late lumen loss was 0.63 ± 0.62 mm for the Yukon Choice stent and 0.45 ± 0.60 mm for the Taxus Liberté stent. Based on the pre-specified margin, the Yukon Choice stent failed to show noninferiority for the primary endpoint. During follow-up, there were no significant differences between groups regarding death, myocardial infarction, stent thrombosis, target lesion revascularization, target vessel revascularization, or nontarget vessel revascularization. Compared with the Taxus Liberté stent, the polymer-free sirolimus-eluting Yukon Choice stent failed to show noninferiority with regard to the primary endpoint, in-stent late lumen loss, in patients with diabetes mellitus after 9-month follow-up. Both stents showed comparable clinical efficacy and safety. (Yukon Choice Versus Taxus Liberté in Diabetes Mellitus; NCT00368953). Copyright © 2011 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

  6. Biomedical engineering in design and application of nitinol stents with shape memory effect

    NASA Astrophysics Data System (ADS)

    Ryklina, E. P.; Khmelevskaya, I. Y.; Morozova, Tamara V.; Prokoshkin, S. D.

    1996-04-01

    Our studies in the field of endosurgery in collaboration with the physicians of the National Research Center of Surgery of the Academy of Medical Sciences are carried out beginning in 1983. These studies laid the foundation for the new direction of X-ray surgery--X-ray Nitinol stenting of vessels and tubular structures. X-ray nitinol stents are unique self-fixing shells based on the shape memory effect and superelasticity of nickel-titanium alloys self- reconstructed under human body temperature. Applied for stenting of arteries in cases of stenosis etc., bile ducts in cases of benign and malignant stenoses, digestive tract in cases of oesophageal cancer and cervical canal uterus in cases of postsurgical atresiss and strictures of uterine. The purpose of stenting is restoration of the shape of artery or tubular structure by a cylinder frame formation. The especially elaborated original method of stenting allows to avoid the traditional surgical operation, i.e. the stenting is performed without blood, narcosis and surgical knife. The stent to be implanted is transported into the affected zone through the puncture under the X-ray control. Clinical applications of X-ray endovascular stenting has been started in March 1984. During this period nearly 400 operations on stenting have been performed on femoral, iliac, brachio-cephalic, subclavian arteries, bile ducts, tracheas, digestive tract and cervical canal uterus.

  7. Preclinical Study of a Biodegradable Polymer-based Stent with Abluminal Sirolimus Release

    PubMed Central

    Takimura, Celso Kiyochi; Campos, Carlos Augusto Homem M.; Melo, Pedro Henrique Magualhães Craveiro; Campos, Julliana Carvalho; Gutierrez, Paulo Sampaio; Borges, Thiago Francisco Costa; Curado, Luciano; Morato, Spero Penha; Laurindo, Francisco Rafael Martins; Lemos, Pedro Alves

    2014-01-01

    Background Bioabsorbable polymer stents with drug elution only on the abluminal surface may be safer than durable polymer drug-eluting stents. Objective To report the experimental findings with the InspironTM stent - a bioabsorbable polymer-coated stent with sirolimus release from the abluminal surface only, recently approved for clinical use. Methods 45 stents were implanted in the coronary arteries of 15 pigs. On day 28 after implantation, angiographic, intracoronary ultrasonographic and histomorphological data were collected. Five groups were analyzed: Group I (nine bare-metal stents); Group II (nine coated with bioabsorbable polymer on the luminal and abluminal surfaces); Group III (eight stents coated with bioabsorbable polymer on the abluminal surface); Group IV (nine stents with bioabsorbable polymer and sirolimus on the luminal and abluminal surfaces); and Group V (ten stents with bioabsorbable polymer and sirolimus only on the abluminal surface). Results The following results were observed for Groups I, II, III, IV and V, respectively: percentage stenosis of 29 ± 20; 36 ± 14; 33 ± 19; 22 ± 13 and 26 ± 15 (p = 0.443); late lumen loss (in mm) of 1.02 ± 0.60; 1.24 ± 0.48; 1.11 ± 0.54; 0.72 ± 0.44 and 0.78 ± 0.39 (p = 0.253); neointimal area (in mm2) of 2.60 ± 1.99; 2.74 ± 1.51; 2.74 ± 1.30; 1.30 ± 1.14 and 0.97 ± 0.84 (p = 0.001; Groups IV and V versus Groups I, II and III); and percentage neointimal area of 35 ± 25; 38 ± 18; 39 ± 19; 19 ± 18 and 15 ± 12 (p = 0.001; Groups IV and V versus Groups I, II and III). Injury and inflammation scores were low and with no differences between the groups. Conclusion The InspironTM stent proved to be safe and was able to significantly inhibit the neointimal hyperplasia observed on day 28 after implantation in porcine coronary arteries. PMID:24759951

  8. Fabrication of a silver particle-integrated silicone polymer-covered metal stent against sludge and biofilm formation and stent-induced tissue inflammation

    PubMed Central

    Lee, Tae Hoon; Jang, Bong Seok; Jung, Min Kyo; Pack, Chan Gi; Choi, Jun-Ho; Park, Do Hyun

    2016-01-01

    To reduce tissue or tumor ingrowth, covered self-expandable metal stents (SEMSs) have been developed. The effectiveness of covered SEMSs may be attenuated by sludge or stone formation or by stent clogging due to the formation of biofilm on the covering membrane. In this study, we tested the hypothesis that a silicone membrane containing silver particles (Ag-P) would prevent sludge and biofilm formation on the covered SEMS. In vitro, the Ag-P-integrated silicone polymer-covered membrane exhibited sustained antibacterial activity, and there was no definite release of silver ions from the Ag-P-integrated silicone polymer membrane at any time point. Using a porcine stent model, in vivo analysis demonstrated that the Ag-P-integrated silicone polymer-covered SEMS reduced the thickness of the biofilm and the quantity of sludge formed, compared with a conventional silicone-covered SEMS. In vivo, the release of silver ions from an Ag-P-integrated silicone polymer-covered SEMS was not detected in porcine serum. The Ag-P-integrated silicone polymer-covered SEMS also resulted in significantly less stent-related bile duct and subepithelium tissue inflammation than a conventional silicone polymer-covered SEMS. Therefore, the Ag-P-integrated silicone polymer-covered SEMS reduced sludge and biofilm formation and stent-induced pathological changes in tissue. This novel SEMS may prolong the stent patency in clinical application. PMID:27739486

  9. 3D-Printed Multidrug-Eluting Stent from Graphene-Nanoplatelet-Doped Biodegradable Polymer Composite.

    PubMed

    Misra, Santosh K; Ostadhossein, Fatemeh; Babu, Ramya; Kus, Joseph; Tankasala, Divya; Sutrisno, Andre; Walsh, Kathleen A; Bromfield, Corinne R; Pan, Dipanjan

    2017-03-21

    Patients with percutaneous coronary intervention generally receive either bare metal stents or drug-eluting stents to restore the normal blood flow. However, due to the lack of stent production with an individual patient in mind, the same level of effectiveness may not be possible in treating two different clinical scenarios. This study introduces for the first time the feasibility of a patient-specific stenting process constructed from direct 3D segmentation of medical images using direct 3D printing of biodegradable polymer-graphene composite with dual drug incorporation. A biodegradable polymer-carbon composite is prepared doped with graphene nanoplatelets to achieve controlled release of combinatorics as anticoagulation and antirestenosis agents. This study develops a technology prototyped for personalized stenting. An in silico analysis is performed to optimize the stent design for printing and its prediction of sustainability under force exerted by coronary artery or blood flow. A holistic approach covering in silico to in situ-in vivo establishes the structural integrity of the polymer composite, its mechanical properties, drug loading and release control, prototyping, functional activity, safety, and feasibility of placement in coronary artery of swine.

  10. Medical applications of shape memory polymers

    NASA Technical Reports Server (NTRS)

    Sokolowski, Witold M.

    2005-01-01

    Shape memory polymers are described here and major advantages in some applications are identified over other medical materials such as shape memory alloys (SMA). A number of medical applications are anticipated for shape memory polymers. Some simple applications are already utilized in medical world, others are in examination process. Lately, several important applications are being considered for CHEM foams for self-deployable vascular and coronary devices. One of these potential applications, the endovascular treatment of aneurysm was experimentally investigated with encouraging results and is described in this paper as well.

  11. Medical applications of shape memory polymers

    NASA Technical Reports Server (NTRS)

    Sokolowski, Witold M.

    2005-01-01

    Shape memory polymers are described here and major advantages in some applications are identified over other medical materials such as shape memory alloys (SMA). A number of medical applications are anticipated for shape memory polymers. Some simple applications are already utilized in medical world, others are in examination process. Lately, several important applications are being considered for CHEM foams for self-deployable vascular and coronary devices. One of these potential applications, the endovascular treatment of aneurysm was experimentally investigated with encouraging results and is described in this paper as well.

  12. Thermal response of novel shape memory polymer-shape memory alloy hybrids

    NASA Astrophysics Data System (ADS)

    Rossiter, Jonathan; Takashima, Kazuto; Mukai, Toshiharu

    2014-03-01

    Shape memory polymers (SMP) and shape memory alloys (SMA) have both been proven important smart materials in their own fields. Shape memory polymers can be formed into complex three-dimensional structures and can undergo shape programming and large strain recovery. These are especially important for deployable structures including those for space applications and micro-structures such as stents. Shape memory alloys on the other hand are readily exploitable in a range of applications where simple, silent, light-weight and low-cost repeatable actuation is required. These include servos, valves and mobile robotic artificial muscles. Despite their differences, one important commonality between SMPs and SMAs is that they are both typically activated by thermal energy. Given this common characteristic it is important to consider how these two will behave when in close environmental proximity, and hence exposed to the same thermal stimulus, and when they are incorporated into a hybrid SMA-SMP structure. In this paper we propose and examine the operation of SMA-SMP hybrids. The relationship between the two temperatures Tg, the glass transition temperature of the polymer, and Ta, the nominal austenite to martensite transition temperature of the alloy is considered. We examine how the choice of these two temperatures affects the thermal response of the hybrid. Electrical stimulation of the SMA is also considered as a method not only of actuating the SMA but also of inducing heating in the surrounding polymer, with consequent effects on actuator behaviour. Likewise by varying the rate and degree of thermal stimulation of the SMA significantly different actuation and structural stiffness can be achieved. Novel SMP-SMA hybrid actuators and structures have many ready applications in deployable structures, robotics and tuneable engineering systems.

  13. Efficacy and safety of biodegradable polymer biolimus-eluting stents versus durable polymer drug-eluting stents: a meta-analysis.

    PubMed

    Ye, Yicong; Xie, Hongzhi; Zeng, Yong; Zhao, Xiliang; Tian, Zhuang; Zhang, Shuyang

    2013-01-01

    Drug-eluting stents (DES) with biodegradable polymers have been developed to address the risk of thrombosis associated with first-generation DES. We aimed to determine the efficacy and safety of biodegradable polymer biolimus-eluting stents (BES) versus durable polymer DES. Systematic database searches of MEDLINE (1950 to June 2013), EMBASE (1966 to June 2013), the Cochrane Central Register of Controlled Trials (Issue 6 of 12, June 2013), and a review of related literature were conducted. All randomized controlled trials comparing biodegradable polymer BES versus durable polymer DES were included. Eight randomized controlled trials investigating 11,015 patients undergoing percutaneous coronary interventions were included in the meta-analysis. The risk of major adverse cardiac events did not differ significantly between the patients treated with the biodegradable polymer BES and the durable polymer DES (Relative risk [RR], 0.970; 95% CI, 0.848-1.111; p = 0.662). However, biodegradable polymer BES was associated with reduced risk of very late ST compared with the durable polymer DES, while the risk of early or late ST was similar (RR for early or late ST, 1.167; 95% CI 0.755-1.802; p = 0.487; RR 0.273; 95% CI 0.115-0.652; p = 0.003; p for interaction = 0.003). In this meta-analysis of randomized controlled trials, treatments with biodegradable polymer BES did not significantly reduce the risk of major adverse cardiac events, but demonstrated a significantly lower risk of very late ST when compared to durable polymer DES. This conclusion requires confirmation by further studies with long-term follow-up. http://www.crd.york.ac.uk/PROSPERO/display_record.asp?ID=CRD42013004364#.UnM2lfmsj6J.

  14. Outcomes of Acute Myocardial Infarction Patients Implanted With Biodegradable Polymer Biolimus-Eluting Stents Versus New-Generation Durable Polymer Drug-Eluting Stents: A Retrospective Analysis.

    PubMed

    Choe, Jeong Cheon; Cha, Kwang Soo; Jang, Hye Yoon; Choi, Jong Hyun; Kim, Bo Won; Ahn, Jinhee; Park, Jin Sup; Lee, Hye Won; Oh, Jun-Hyok; Choi, Jung Hyun; Lee, Han Cheol; Hong, Taek Jong; Ahn, Youngkeun; Jeong, Myung Ho

    2017-09-01

    We compared outcomes between biodegradable polymer biolimus-eluting stent (BP-BES) and new-generation durable polymer drug-eluting stent (DP-DES) implantations in patients with acute myocardial infarction (MI). Among 13472 patients with acute MI in a nationwide registry, 557 (64.8%) were in the BP-BES and 303 (35.2%) in the new-generation DP-DES group following coronary reperfusion. The occurrence of major adverse cardiac events (MACE; death, MI, revascularization) and stent thrombosis was compared. Major adverse cardiac events occurred in 53 (6.2%) patients and showed similar rates between the BP-BES and new-generation DP-DES groups (all: 6.6% vs 5.9%, P = .652; propensity score [PS] matched: n = 380, 6.3% vs 5.3%, P = .623). Stent thrombosis did not differ between groups (all: 0.3% vs 0.4%, P = .892; PS matched: 0.5% vs 0.5%, P = 1.000). Major adverse cardiac event-free survival was comparable between groups (all: 93.4% vs 94.1%, log-rank P = .357; PS matched: 93.7% vs 94.7%, log-rank P = .445). Biodegradable polymer biolimus-eluting stent was not associated with MACE (all: hazard ratio [HR], 1.67; 95% confidence interval [CI], 0.75-3.74; P = 0.212; PS matched: HR, 1.05; 95% CI, 0.40-2.75; P = .915). In conclusion, in patients with acute MI, BP-BES was equivalent to the new-generation DP-DES in terms of outcomes.

  15. Zotarolimus-eluting durable-polymer-coated stent versus a biolimus-eluting biodegradable-polymer-coated stent in unselected patients undergoing percutaneous coronary intervention (SORT OUT VI): a randomised non-inferiority trial.

    PubMed

    Raungaard, Bent; Jensen, Lisette Okkels; Tilsted, Hans-Henrik; Christiansen, Evald Høj; Maeng, Michael; Terkelsen, Christian Juhl; Krusell, Lars Romer; Kaltoft, Anne; Kristensen, Steen Dalby; Bøtker, Hans Erik; Thuesen, Leif; Aarøe, Jens; Jensen, Svend Eggert; Villadsen, Anton Boel; Thayssen, Per; Veien, Karsten Tange; Hansen, Knud Nørregaard; Junker, Anders; Madsen, Morten; Ravkilde, Jan; Lassen, Jens Flensted

    2015-04-18

    New-generation drug-eluting coronary stents have reduced the risk of coronary events, especially in patients with complex disease or lesions. To what extent different stent platforms, polymers, and antiproliferative drugs affect outcomes, however, is unclear. We investigated the safety and efficacy of a third-generation stent by comparing a highly biocompatible durable-polymer-coated zotarolimus-eluting stent with a biodegradable-polymer-coated biolimus-eluting stent. This open-label, randomised, multicentre, non-inferiority trial was done at three sites across western Denmark. All patients who presented with stable coronary artery disease or acute coronary syndromes and at least one coronary artery lesion (more than 50% stenosis) from March, 2011, to August, 2012, were assessed for eligibility. Patients were randomly assigned in a 1:1 ratio to receive either the durable-polymer zotarolimus-eluting stent or the biodegradable-polymer biolimus-eluting stent. The primary endpoint was a composite of safety (cardiac death and myocardial infarction not clearly attributable to a non-target lesion) and efficacy (target-lesion revascularisation) at 12 months, analysed by intention to treat. The trial was powered to assess non-inferiority of durable-polymer zotarolimus-eluting stent compared with the biodegradable-polymer biolimus-eluting stent with a predetermined non-inferiority margin of 0·025. This trial is registered with ClinicalTrials.gov, number NCT01956448. Of 7103 screened, 1502 patients with 1883 lesions were assigned to receive the durable-polymer zotarolimus-eluting stent and 1497 patients with 1791 lesions to receive the biodegradable-polymer biolimus-eluting stent. 79 (5·3%) and 75 (5·0%) patients, respectively, met the primary endpoint (absolute risk difference 0·0025, upper limit of one-sided 95% CI 0·016%; p=0·004). The individual components of the primary endpoint did not differ significantly between stent types at 12 months. The durable-polymer

  16. Safety and efficacy of a novel abluminal groove-filled biodegradable polymer sirolimus-eluting stent.

    PubMed

    Zhu, Jinzhou; Liu, Huizhu; Cui, Haipo; Tang, Zhirong; Song, Chengli; Zhang, Ruiyan

    2017-03-01

    Late stent thrombosis (LST) following drug-eluting stent (DES) implantation in patients with coronary artery disease (CAD) is often associated with delayed vascular healing, resulting from vascular inflammation and hypersensitivity to durable polymers and drugs. Therefore, DES design, materials, and coatings have been technologically revolutionized. Herein, we designed a novel abluminal groove-filled biodegradable polymer sirolimus-eluting stent (AGF-BP-SES), with a sirolimus content of only about one-third of traditional DES. The mechanical performances of AGF-BP-SES during compression and expansion were investigated. The pharmacokinetic (PK) profile of sirolimus was studied in the swine model. The in vivo efficacy of AGF-BP-SES was compared with that of Xience PRIME(®) stent. The results showed that AGF-BP-SES exhibited mechanical properties similar to traditional DES, including the rebound ratio of radial contraction/direction, rebound ratio of axial contraction/direction, and inhomogeneity of compression/expansion. Despite utilizing a reduced dose of sirolimus, AGF-BP-SES delivered sirolimus to the coronary artery in a controlled and efficient manner. The stent maintained a safe and effective local drug concentration without local or systemic risks. In the swine model, histopathological indicators predicted safety and biocompatibility of AGF-BP-SES. In conclusion, AGF-BP-SES maintained similar mechanical properties as other stents while reducing the drug-loading capacity, and showed a favorable safety and efficacy profile of the targeted DES.

  17. A Wireless Pressure Sensor Integrated with a Biodegradable Polymer Stent for Biomedical Applications

    PubMed Central

    Park, Jongsung; Kim, Ji-Kwan; Patil, Swati J.; Park, Jun-Kyu; Park, SuA; Lee, Dong-Weon

    2016-01-01

    This paper describes the fabrication and characterization of a wireless pressure sensor for smart stent applications. The micromachined pressure sensor has an area of 3.13 × 3.16 mm2 and is fabricated with a photosensitive SU-8 polymer. The wireless pressure sensor comprises a resonant circuit and can be used without the use of an internal power source. The capacitance variations caused by changes in the intravascular pressure shift the resonance frequency of the sensor. This change can be detected using an external antenna, thus enabling the measurement of the pressure changes inside a tube with a simple external circuit. The wireless pressure sensor is capable of measuring pressure from 0 mmHg to 230 mmHg, with a sensitivity of 0.043 MHz/mmHg. The biocompatibility of the pressure sensor was evaluated using cardiac cells isolated from neonatal rat ventricular myocytes. After inserting a metal stent integrated with the pressure sensor into a cardiovascular vessel of an animal, medical systems such as X-ray were employed to consistently monitor the condition of the blood vessel. No abnormality was found in the animal blood vessel for approximately one month. Furthermore, a biodegradable polymer (polycaprolactone) stent was fabricated with a 3D printer. The polymer stent exhibits better sensitivity degradation of the pressure sensor compared to the metal stent. PMID:27271619

  18. A Wireless Pressure Sensor Integrated with a Biodegradable Polymer Stent for Biomedical Applications.

    PubMed

    Park, Jongsung; Kim, Ji-Kwan; Patil, Swati J; Park, Jun-Kyu; Park, SuA; Lee, Dong-Weon

    2016-06-02

    This paper describes the fabrication and characterization of a wireless pressure sensor for smart stent applications. The micromachined pressure sensor has an area of 3.13 × 3.16 mm² and is fabricated with a photosensitive SU-8 polymer. The wireless pressure sensor comprises a resonant circuit and can be used without the use of an internal power source. The capacitance variations caused by changes in the intravascular pressure shift the resonance frequency of the sensor. This change can be detected using an external antenna, thus enabling the measurement of the pressure changes inside a tube with a simple external circuit. The wireless pressure sensor is capable of measuring pressure from 0 mmHg to 230 mmHg, with a sensitivity of 0.043 MHz/mmHg. The biocompatibility of the pressure sensor was evaluated using cardiac cells isolated from neonatal rat ventricular myocytes. After inserting a metal stent integrated with the pressure sensor into a cardiovascular vessel of an animal, medical systems such as X-ray were employed to consistently monitor the condition of the blood vessel. No abnormality was found in the animal blood vessel for approximately one month. Furthermore, a biodegradable polymer (polycaprolactone) stent was fabricated with a 3D printer. The polymer stent exhibits better sensitivity degradation of the pressure sensor compared to the metal stent.

  19. Long-term coronary arterial response to biodegradable polymer biolimus-eluting stents in comparison with durable polymer sirolimus-eluting stents and bare-metal stents: five-year follow-up optical coherence tomography study.

    PubMed

    Kuramitsu, Shoichi; Sonoda, Shinjo; Yokoi, Hiroyoshi; Iwabuchi, Masashi; Nishizaki, Yuji; Shinozaki, Tomohiro; Domei, Takenori; Hyodo, Makoto; Inoue, Katsumi; Shirai, Shinichi; Ando, Kenji; Nobuyoshi, Masakiyo

    2014-11-01

    The long-term coronary arterial response of biodegradable polymer biolimus-eluting stents (BES) remains unclear. We sought to evaluate the coronary arterial response of biodegradable polymer BES at 5 years after stent implantation using optical coherence tomography (OCT) as compared with that of durable polymer sirolimus-eluting stents (SES) and bare-metal stents (BMS). Five-year follow-up OCT was performed in 30 patients with 33 stents (10 with 12 BES; 10 with 11 SES; 10 with 10 BMS). Quantitative parameters and qualitative characteristics of the neointima were evaluated. A total of 5178 struts (BES, n = 2056; SES, n = 1410; BMS, n = 1712) were analyzed. Uncovered struts were found in 15 out of 2055 struts in the BES (weighted estimate 0.01%, 95% confidence intervals [CI]: 0.00-0.33%) and 54 out of 1410 struts in the SES (0.11%, 95% CI: 0.00-3.33%) (odds ratio [OR] 0.12, 95% CI: 0.01-1.95, p = 0.13). None of 1712 struts were uncovered in the BMS. Cross-sectional qualitative analysis of neointimal tissue showed that the frequency of lipid-laden neointima tended to be lower in the BES (2.26%, 95% CI: 0.38-12.3%) compared with the SES (9.90%, 95% CI: 4.37-20.9%; OR 0.21, 95% CI 0.03-1.16, p = 0.07), and was similar to the BMS (2.23%, 95% CI: 0.54-8.74%; OR 0.98, 95% CI 0.13-7.14, p = 0.98). Biodegradable polymer BES shows a favorable coronary arterial response compared with SES, but different response with BMS at 5 years follow-up. The observed frequency of in-stent neoatherosclerosis within BES was similar to BMS and tended to be lower than SES. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  20. Comparison of the Absorbable Polymer Sirolimus-Eluting Stent (MiStent) to the Durable Polymer Everolimus-Eluting Stent (Xience) (from the DESSOLVE I/II and ISAR-TEST-4 Studies).

    PubMed

    Lansky, Alexandra J; Kastrati, Adnan; Edelman, Elazer R; Parise, Helen; Ng, Vivian G; Ormiston, John; Wijns, William; Byrne, Robert A

    2016-02-15

    We compared the outcomes of a novel, thin-strut, cobalt-chromium, absorbable, polymer sirolimus-eluting stent (APSES; MiStent) to the durable polymer cobalt-chromium everolimus-eluting stent (EES; Xience). A propensity-matched analysis was performed comparing data from the DES With Sirolimus and a Bioabsorbable Polymer for the Treatment of Patients With De Novo Lesions in the Native Coronary Arteries (DESSOLVE) I and II studies, evaluating the APSES to the EES arm of the Intracoronary Stenting and Angiographic Results: Test Efficacy of 3 Limus-Eluting Stents-4 study. Target lesion failure (TLF) and its components were evaluated at 12 months and annually to 3 years; 805 patients (APSES = 153; EES = 652) were included with propensity matching in 204 patients (APSES = 102; EES = 102). APSES compared with EES had lower TLF at 1 year (3.0% vs 8.0%, p = 0.12) driven by a difference in target lesion revascularization (TLR; 1% vs 6%, p = 0.05), with no difference in target vessel myocardial infarction (p = 0.56) or stent thrombosis (p = 0.31). At 3 years, TLF (5.0% vs 12.5%, p = 0.07) and TLR (2.0% vs 8.4%, p = 0.04) remained lower with APSES. By landmark analysis, there was no significant difference in TLF between 1 and 3 years (p = 0.36). In conclusion, in a propensity-matched analysis, the APSES demonstrated reduced clinically indicated TLR rates at 1 and 3 years compared with the durable polymer EES, with minimal accrual of events between 1 and 3 years.

  1. Electron Beam Crosslinked Polyurethane Shape Memory Polymers with Tunable Mechanical Properties.

    PubMed

    Hearon, Keith; Nash, Landon D; Volk, Brent L; Ware, Taylor; Lewicki, James P; Voit, Walter E; Wilson, Thomas S; Maitland, Duncan J

    2013-06-01

    Novel electron beam crosslinked polyurethane shape memory polymers with advanced processing capabilities and tunable thermomechanical properties have been synthesized and characterized. We demonstrate the ability to manipulate crosslink density in order to finely tune rubbery modulus, strain capacity, ultimate tensile strength, recovery stress, and glass transition temperature. This objective is accomplished for the first time in a low-molecular-weight polymer system through the precise engineering of thermoplastic resin precursors suitable for mass thermoplastic processing. Neurovascular stent prototypes were fabricated by dip-coating and laser machining to demonstrate processability.

  2. Electron Beam Crosslinked Polyurethane Shape Memory Polymers with Tunable Mechanical Properties

    PubMed Central

    Hearon, Keith; Nash, Landon D.; Volk, Brent L.; Ware, Taylor; Lewicki, James P.; Voit, Walter E.; Wilson, Thomas S.

    2014-01-01

    Novel electron beam crosslinked polyurethane shape memory polymers with advanced processing capabilities and tunable thermomechanical properties have been synthesized and characterized. We demonstrate the ability to manipulate crosslink density in order to finely tune rubbery modulus, strain capacity, ultimate tensile strength, recovery stress, and glass transition temperature. This objective is accomplished for the first time in a low-molecular-weight polymer system through the precise engineering of thermoplastic resin precursors suitable for mass thermoplastic processing. Neurovascular stent prototypes were fabricated by dip-coating and laser machining to demonstrate processability. PMID:25411531

  3. The Ultimaster Biodegradable-Polymer Sirolimus-Eluting Stent: An Updated Review of Clinical Evidence

    PubMed Central

    Chisari, Alberto; Pistritto, Anna Maria; Piccolo, Raffaele; La Manna, Alessio; Danzi, Gian Battista

    2016-01-01

    The Ultimaster coronary stent system (Terumo Corporation, Tokyo, Japan) represents a new iteration in drug-eluting stent (DES) technology that has recently received the Conformité Européenne (CE) mark approval for clinical use. The Ultimaster is a thin-strut, cobalt chromium, biodegradable-polymer, sirolimus-eluting coronary stent. The high elasticity of the biodegradable-polymer (PDLLA-PCL) and the abluminal gradient coating technology are additional novel features of this coronary device. The Ultimaster DES has undergone extensive clinical evaluation in two studies: The CENTURY I and II trials. Results from these two landmark studies suggested an excellent efficacy and safety profile of the Ultimaster DES across several lesion and patient subsets, with similar clinical outcomes to contemporary, new-generation DES. The aim of this review is to summarize the rationale behind this novel DES technology and to provide an update of available evidence about the clinical performance of the Ultimaster DES. PMID:27608017

  4. The Ultimaster Biodegradable-Polymer Sirolimus-Eluting Stent: An Updated Review of Clinical Evidence.

    PubMed

    Chisari, Alberto; Pistritto, Anna Maria; Piccolo, Raffaele; La Manna, Alessio; Danzi, Gian Battista

    2016-09-06

    The Ultimaster coronary stent system (Terumo Corporation, Tokyo, Japan) represents a new iteration in drug-eluting stent (DES) technology that has recently received the Conformité Européenne (CE) mark approval for clinical use. The Ultimaster is a thin-strut, cobalt chromium, biodegradable-polymer, sirolimus-eluting coronary stent. The high elasticity of the biodegradable-polymer (PDLLA-PCL) and the abluminal gradient coating technology are additional novel features of this coronary device. The Ultimaster DES has undergone extensive clinical evaluation in two studies: The CENTURY I and II trials. Results from these two landmark studies suggested an excellent efficacy and safety profile of the Ultimaster DES across several lesion and patient subsets, with similar clinical outcomes to contemporary, new-generation DES. The aim of this review is to summarize the rationale behind this novel DES technology and to provide an update of available evidence about the clinical performance of the Ultimaster DES.

  5. Ultrathin Strut Biodegradable Polymer Sirolimus-Eluting Stent Versus Durable-Polymer Everolimus-Eluting Stent for Percutaneous Coronary Revascularization: 2-Year Results of the BIOSCIENCE Trial.

    PubMed

    Zbinden, Rainer; Piccolo, Raffaele; Heg, Dik; Roffi, Marco; Kurz, David J; Muller, Olivier; Vuilliomenet, André; Cook, Stéphane; Weilenmann, Daniel; Kaiser, Christoph; Jamshidi, Peiman; Franzone, Anna; Eberli, Franz; Jüni, Peter; Windecker, Stephan; Pilgrim, Thomas

    2016-03-15

    No data are available on the long-term performance of ultrathin strut biodegradable polymer sirolimus-eluting stents (BP-SES). We reported 2-year clinical outcomes of the BIOSCIENCE (Ultrathin Strut Biodegradable Polymer Sirolimus-Eluting Stent Versus Durable Polymer Everolimus-Eluting Stent for Percutaneous Coronary Revascularisation) trial, which compared BP-SES with durable-polymer everolimus-eluting stents (DP-EES) in patients undergoing percutaneous coronary intervention. A total of 2119 patients with minimal exclusion criteria were assigned to treatment with BP-SES (n=1063) or DP-EES (n=1056). Follow-up at 2 years was available for 2048 patients (97%). The primary end point was target-lesion failure, a composite of cardiac death, target-vessel myocardial infarction, or clinically indicated target-lesion revascularization. At 2 years, target-lesion failure occurred in 107 patients (10.5%) in the BP-SES arm and 107 patients (10.4%) in the DP-EES arm (risk ratio [RR] 1.00, 95% CI 0.77-1.31, P=0.979). There were no significant differences between BP-SES and DP-EES with respect to cardiac death (RR 1.01, 95% CI 0.62-1.63, P=0.984), target-vessel myocardial infarction (RR 0.91, 95% CI 0.60-1.39, P=0.669), target-lesion revascularization (RR 1.17, 95% CI 0.81-1.71, P=0.403), and definite stent thrombosis (RR 1.38, 95% CI 0.56-3.44, P=0.485). There were 2 cases (0.2%) of definite very late stent thrombosis in the BP-SES arm and 4 cases (0.4%) in the DP-EES arm (P=0.423). In the prespecified subgroup of patients with ST-segment elevation myocardial infarction, BP-SES was associated with a lower risk of target-lesion failure compared with DP-EES (RR 0.48, 95% CI 0.23-0.99, P=0.043, Pinteraction=0.026). Comparable safety and efficacy profiles of BP-SES and DP-EES were maintained throughout 2 years of follow-up. URL: https://www.clinicaltrials.gov. Unique identifier: NCT01443104. © 2016 The Authors. Published on behalf of the American Heart Association, Inc., by

  6. Fabrication and characterization of shape memory polymers at small-scales

    NASA Astrophysics Data System (ADS)

    Wornyo, Edem

    The objective of this research is to thoroughly investigate the shape memory effect in polymers, characterize, and optimize these polymers for applications in information storage systems. Previous research effort in this field concentrated on shape memory metals for biomedical applications such as stents. Minimal work has been done on shape memory polymers; and the available work on shape memory polymers has not characterized the behaviors of this category of polymers fully. Copolymer shape memory materials based on diethylene glycol dimethacrylate (DEGDMA) crosslinker, and tert butyl acrylate (tBA) monomer are designed. The design encompasses a careful control of the backbone chemistry of the materials. Characterization methods such as dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC); and novel nanoscale techniques such as atomic force microscopy (AFM), and nanoindentation are applied to this system of materials. Designed experiments are conducted on the materials to optimize spin coating conditions for thin films. Furthermore, the recovery, a key for the use of these polymeric materials for information storage, is examined in detail with respect to temperature. In sum, the overarching objectives of the proposed research are to: (i) Design shape memory polymers based on polyethylene glycol dimethacrylate (PEGDMA) and diethylene glycol dimethacrylate (DEGDMA) crosslinkers, 2-hydroxyethyl methacrylate (HEMA) and tert-butyl acrylate monomer (tBA). (ii) Utilize dynamic mechanical analysis (DMA) to comprehend the thermomechanical properties of shape memory polymers based on DEGDMA and tBA. (iii) Utilize nanoindentation and atomic force microscopy (AFM) to understand the nanoscale behavior of these SMPs, and explore the strain storage and recovery of the polymers from a deformed state. (iv) Study spin coating conditions on thin film quality with designed experiments. (iv) Apply neural networks and genetic algorithms to optimize these systems.

  7. Stent selection in patients with myocardial infarction: drug eluting, biodegradable polymers or bare metal stents?

    PubMed

    Mieres, Juan; Rodríguez, Alfredo E

    2012-08-01

    Percutaneous coronary intervention (PCI) has been increasingly used in the last years during interventional procedures in patients with acute coronary syndromes (ACS) including ST elevation myocardial infarction (STEMI) and non-ST elevation myocardial infarction (NSTEMI). In patients with either STEMI, NSTEMI, high risk ACS with EKG changes or cardiac enzymes rises; PCI with bare metal stent (BMS) implantation has been associated with a significant improvement in clinical outcome. Therefore, BMS implantation during primary PCI in STEMI has become a standard of practice. With the introduction of drug eluting stents (DESs) in this decade, the use of these new devices instead of BMSs in patients with STEMI has emerged as a rational PCI alternative in this particular subgroup of patients. In spite of the unquestionable benefits of DESs in terms of reduction of restenosis and TVR, specific concerns have arisen with regard to their long-term safety. High incidence of very late stent thrombosis has been described with these devices, and special attention should be paid in patients with unstable coronary lesions, in which plaque composition and remodeling may play a main role in their safety and long-term outcome. Intraluminal thrombus caused by plaque rupture is the most frequent mechanism of STEMI, in which the necrotic core and thin fibrous cap play a major role. In this context, the use of first DESs designs may be futile or even unsafe because delayed healing may further contribute to plaque instability. Adjunctive invasive imaging tools can improve stent deployment and safety outcome in these lesions with intravascular findings of plaque instability. Recently, other players such as new dedicated antithrombotic BMS designs, including selfexpanding stents or drug-eluting coated balloons, are exploring their potential indications in patients with ACS and myocardial infarction. This paper reports and discusses new stent devices and adjunctive pharmacologic agents. It

  8. Guide wire extension for shape memory polymer occlusion removal devices

    DOEpatents

    Maitland, Duncan J.; Small, IV, Ward; Hartman, Jonathan

    2009-11-03

    A flexible extension for a shape memory polymer occlusion removal device. A shape memory polymer instrument is transported through a vessel via a catheter. A flexible elongated unit is operatively connected to the distal end of the shape memory polymer instrument to enhance maneuverability through tortuous paths en route to the occlusion.

  9. [Shape-memory polymers for biomedical engineering applications].

    PubMed

    Zhu, Guangming; Liu, Zhongrang

    2005-10-01

    The latest progress in shape-memory polymer for biomedical engineering applications was summarized in this paper. The mechanism responsible for shape memory effect was analyzed in reference to the polymer structure. Also introduced and reviewed were the characteristics of some shape-memory polymers (polyurethane polycaprolactone and polylactide) and their applications in medical engineering.

  10. Polymer-free Drug-Coated Coronary Stents in Patients at High Bleeding Risk.

    PubMed

    Urban, Philip; Meredith, Ian T; Abizaid, Alexandre; Pocock, Stuart J; Carrié, Didier; Naber, Christoph; Lipiecki, Janusz; Richardt, Gert; Iñiguez, Andres; Brunel, Philippe; Valdes-Chavarri, Mariano; Garot, Philippe; Talwar, Suneel; Berland, Jacques; Abdellaoui, Mohamed; Eberli, Franz; Oldroyd, Keith; Zambahari, Robaayah; Gregson, John; Greene, Samantha; Stoll, Hans-Peter; Morice, Marie-Claude

    2015-11-19

    Patients at high risk for bleeding who undergo percutaneous coronary intervention (PCI) often receive bare-metal stents followed by 1 month of dual antiplatelet therapy. We studied a polymer-free and carrier-free drug-coated stent that transfers umirolimus (also known as biolimus A9), a highly lipophilic sirolimus analogue, into the vessel wall over a period of 1 month. In a randomized, double-blind trial, we compared the drug-coated stent with a very similar bare-metal stent in patients with a high risk of bleeding who underwent PCI. All patients received 1 month of dual antiplatelet therapy. The primary safety end point, tested for both noninferiority and superiority, was a composite of cardiac death, myocardial infarction, or stent thrombosis. The primary efficacy end point was clinically driven target-lesion revascularization. We enrolled 2466 patients. At 390 days, the primary safety end point had occurred in 112 patients (9.4%) in the drug-coated-stent group and in 154 patients (12.9%) in the bare-metal-stent group (risk difference, -3.6 percentage points; 95% confidence interval [CI], -6.1 to -1.0; hazard ratio, 0.71; 95% CI, 0.56 to 0.91; P<0.001 for noninferiority and P=0.005 for superiority). During the same time period, clinically driven target-lesion revascularization was needed in 59 patients (5.1%) in the drug-coated-stent group and in 113 patients (9.8%) in the bare-metal-stent group (risk difference, -4.8 percentage points; 95% CI, -6.9 to -2.6; hazard ratio, 0.50; 95% CI, 0.37 to 0.69; P<0.001). Among patients at high risk for bleeding who underwent PCI, a polymer-free umirolimus-coated stent was superior to a bare-metal stent with respect to the primary safety and efficacy end points when used with a 1-month course of dual antiplatelet therapy. (Funded by Biosensors Europe; LEADERS FREE ClinicalTrials.gov number, NCT01623180.).

  11. Temperature and electrical memory of polymer fibers

    NASA Astrophysics Data System (ADS)

    Yuan, Jinkai; Zakri, Cécile; Grillard, Fabienne; Neri, Wilfrid; Poulin, Philippe

    2014-05-01

    We report in this work studies of the shape memory behavior of polymer fibers loaded with carbon nanotubes or graphene flakes. These materials exhibit enhanced shape memory properties with the generation of a giant stress upon shape recovery. In addition, they exhibit a surprising temperature memory with a peak of generated stress at a temperature nearly equal to the temperature of programming. This temperature memory is ascribed to the presence of dynamical heterogeneities and to the intrinsic broadness of the glass transition. We present recent experiments related to observables other than mechanical properties. In particular nanocomposite fibers exhibit variations of electrical conductivity with an accurate memory. Indeed, the rate of conductivity variations during temperature changes reaches a well defined maximum at a temperature equal to the temperature of programming. Such materials are promising for future actuators that couple dimensional changes with sensing electronic functionalities.

  12. Temperature and electrical memory of polymer fibers

    SciTech Connect

    Yuan, Jinkai; Zakri, Cécile; Grillard, Fabienne; Neri, Wilfrid; Poulin, Philippe

    2014-05-15

    We report in this work studies of the shape memory behavior of polymer fibers loaded with carbon nanotubes or graphene flakes. These materials exhibit enhanced shape memory properties with the generation of a giant stress upon shape recovery. In addition, they exhibit a surprising temperature memory with a peak of generated stress at a temperature nearly equal to the temperature of programming. This temperature memory is ascribed to the presence of dynamical heterogeneities and to the intrinsic broadness of the glass transition. We present recent experiments related to observables other than mechanical properties. In particular nanocomposite fibers exhibit variations of electrical conductivity with an accurate memory. Indeed, the rate of conductivity variations during temperature changes reaches a well defined maximum at a temperature equal to the temperature of programming. Such materials are promising for future actuators that couple dimensional changes with sensing electronic functionalities.

  13. Meta-Analysis of Randomized Clinical Trials Comparing Biodegradable Polymer Drug-Eluting Stent to Second-Generation Durable Polymer Drug-Eluting Stents.

    PubMed

    El-Hayek, Georges; Bangalore, Sripal; Casso Dominguez, Abel; Devireddy, Chandan; Jaber, Wissam; Kumar, Gautam; Mavromatis, Kreton; Tamis-Holland, Jacqueline; Samady, Habib

    2017-03-13

    The authors sought to perform a meta-analysis of randomized clinical trials (RCTs) comparing the safety and efficacy of biodegradable polymer drug-eluting stents (BP-DES) to second-generation durable polymer drug-eluting stents (DP-DES). Prior meta-analyses have established the superiority of BP-DES over bare-metal stents and first-generation DP-DES; however, their advantage compared with second-generation DP-DES remains controversial. The authors searched PubMed and Scopus databases for RCTs comparing BP-DES to the second-generation DP-DES. Outcomes included target vessel revascularization (TVR) as efficacy outcome and cardiac death, myocardial infarction (MI), and definite or probable stent thrombosis (ST) as safety outcomes. In addition, we performed landmark analysis for endpoints beyond 1 year of follow-up and a subgroup analysis based on the stent characteristics. The authors included 16 RCTs comprising 19,886 patients in the meta-analysis. At the longest available follow-up (mean duration 26 months), we observed no significant differences in TVR (p = 0.62), cardiac death (p = 0.46), MI (p = 0.98), or ST (risk ratio: 0.83, 95% confidence interval: 0.64 to 1.09; p = 0.19). Our landmark analysis showed that BP-DES were not associated with a reduction in the risk of very late ST (risk ratio: 0.87, 95% confidence interval: 0.49 to 1.53; p = 0.62). Similar outcomes were seen regardless of the eluting drug (biolimus vs. sirolimus), the stent platform (stainless steel vs. alloy), the kinetics of polymer degradation or drug release (<6 months vs. >6 months), the strut thickness of the BP-DES (thin <100 μm vs. thick >100 μm), or the DAPT duration (≥6 months vs. ≥12 months). BP-DES have similar safety and efficacy profiles to second-generation DP-DES. Published by Elsevier Inc.

  14. Efficacy and safety of a novel bioabsorbable polymer-coated, everolimus-eluting coronary stent: the EVOLVE II Randomized Trial.

    PubMed

    Kereiakes, Dean J; Meredith, Ian T; Windecker, Stephan; Lee Jobe, R; Mehta, Shamir R; Sarembock, Ian J; Feldman, Robert L; Stein, Bernardo; Dubois, Christophe; Grady, Timothy; Saito, Shigeru; Kimura, Takeshi; Christen, Thomas; Allocco, Dominic J; Dawkins, Keith D

    2015-04-01

    Drug eluting stents with durable polymers may be associated with hypersensitivity, delayed healing, and incomplete endothelialization, which may contribute to late/very late stent thrombosis and the need for prolonged dual antiplatelet therapy. Bioabsorbable polymers may facilitate stent healing, thus enhancing clinical safety. The SYNERGY stent is a thin-strut, platinum chromium metal alloy platform with an ultrathin bioabsorbable Poly(D,L-lactide-co-glycolide) abluminal everolimus-eluting polymer. We performed a multicenter, randomized controlled trial for regulatory approval to determine noninferiority of the SYNERGY stent to the durable polymer PROMUS Element Plus everolimus-eluting stent. Patients (n=1684) scheduled to undergo percutaneous coronary intervention for non-ST-segment-elevation acute coronary syndrome or stable coronary artery disease were randomized to receive either the SYNERGY stent or the PROMUS Element Plus stent. The primary end point of 12-month target lesion failure was observed in 6.7% of SYNERGY and 6.5% PROMUS Element Plus treated subjects by intention-to-treat (P=0.83 for difference; P=0.0005 for noninferiority), and 6.4% in both the groups by per-protocol analysis (P=0.0003 for noninferiority). Clinically indicated revascularization of the target lesion or definite/probable stent thrombosis were observed in 2.6% versus 1.7% (P=0.21) and 0.4% versus 0.6% (P=0.50) of SYNERGY versus PROMUS Element Plus-treated subjects, respectively. In this randomized trial, the SYNERGY bioabsorbable polymer everolimus-eluting stent was noninferior to the PROMUS Element Plus everolimus-eluting stent with respect to 1-year target lesion failure. These data support the relative safety and efficacy of SYNERGY in a broad range of patients undergoing percutaneous coronary intervention. URL: http://www.clinicaltrials.gov. Unique identifier: NCT01665053. © 2015 American Heart Association, Inc.

  15. Biodegradable Polymer Biolimus-Eluting Stents Versus Durable Polymer Everolimus-Eluting Stents in Patients With Coronary Artery Disease: Final 5-Year Report From the COMPARE II Trial (Abluminal Biodegradable Polymer Biolimus-Eluting Stent Versus Durable Polymer Everolimus-Eluting Stent).

    PubMed

    Vlachojannis, Georgios J; Smits, Pieter C; Hofma, Sjoerd H; Togni, Mario; Vázquez, Nicolás; Valdés, Mariano; Voudris, Vassilis; Slagboom, Ton; Goy, Jean-Jaques; den Heijer, Peter; van der Ent, Martin

    2017-06-26

    This analysis investigates the 5-year outcomes of the biodegradable polymer biolimus-eluting stent (BP-BES) and durable polymer everolimus-eluting stent (DP-EES) in an all-comers population undergoing percutaneous coronary intervention. Recent 1- and 3-year results from randomized trials have indicated similar safety and efficacy outcomes of BP-BES and DP-EES. Whether benefits of the biodegradable polymer device arise over longer follow-up is unknown. Moreover, in-depth, prospective, long-term follow-up data on metallic drug-eluting stents with durable or biodegradable polymers are scarce. The COMPARE II trial (Abluminal Biodegradable Polymer Biolimus-Eluting Stent Versus Durable Polymer Everolimus-Eluting Stent) was a prospective, randomized, multicenter, all-comers trial in which 2,707 patients were randomly allocated (2:1) to BP-BES or DP-EES. The pre-specified endpoint at 5 years was major adverse cardiac events, a composite of cardiac death, nonfatal myocardial infarction, or target vessel revascularization. Five-year follow-up was available in 2,657 patients (98%). At 5 years, major adverse cardiac events occurred in 310 patients (17.3%) in the BP-BES group and 142 patients (15.6%) in the DP-EES group (p = 0.26). The rate of the combined safety endpoint all-cause death or myocardial infarction was 15.0% in the BP-BES group versus 14.8% in the DP-EES group (p = 0.90), whereas the efficacy measure target vessel revascularization was 10.6% versus 9.0% (p = 0.18), respectively. Interestingly, definite stent thrombosis rates did not differ between groups (1.5% for BP-BES vs. 0.9% for DP-EES; p = 0.17). The 5-year analysis comparing biodegradable polymer-coated BES and the durable polymer-coated EES confirms the initial early- and mid-term results regarding similar safety and efficacy outcomes in this all-comers percutaneous coronary intervention population. Copyright © 2017 American College of Cardiology Foundation. Published by Elsevier Inc. All rights

  16. Comparison of long-term in-stent vascular response between abluminal groove-filled biodegradable polymer sirolimus-eluting stent and durable polymer everolimus-eluting stent: 3-year OCT follow-up from the TARGET I trial.

    PubMed

    Xu, Bo; Zhang, Yao-Jun; Sun, Zhong-Wei; Qiao, Shu-Bin; Chen, Shao-Liang; Zhang, Rui-Yan; Pan, Dao-Rong; Pang, Si; Zhang, Qi; Xu, Liang; Yang, Yue-Jin; Leon, Martin B; Gao, Run-Lin

    2015-12-01

    The study sought to compare long-term optical coherence tomography (OCT)-based in-stent vascular response between the abluminal groove-filled biodegradable polymer sirolimus-eluting stent (SES) and the durable polymer everolimus-eluting stent (EES) in the TARGET I trial. The TARGET I trial was a prospective, multicenter, randomized clinical trial which enrolled 458 patients with single de novo lesions treated by abluminal groove-filled biodegradable polymer SES and EES. A subset of 43 patients underwent angiography and OCT examinations at 3 years. All OCT images were analyzed at 0.4 mm intervals. A similar increase in angiographic late lumen loss was observed in SES and EES (from 0.05 ± 0.05 vs. 0.05 ± 0.05 mm [p = 0.84] at 9 months to 0.25 ± 0.37 vs. 0.26 ± 0.19 mm [p = 0.99] at 3 years, respectively), without significant differences at 3 years in mean neointimal thickness of stent struts (SES: 0.13 ± 0.02 mm vs. EES: 0.13 ± 0.02 mm, p = 0.80); mean percentage of covered struts (SES: 99.2 % vs. EES: 99.3 %, p = 0.53), or malapposed strut rates (SES: 0.08 % vs. EES: 0.06 %, p = 0.15). The OCT-based in-stent vascular response evaluation found similar vascular healing for the two studied devices, indicating that the luminal loss in EES from 9 months to 3 years cannot be imputed on its coated biocompatible polymer.

  17. Preclinical evaluation of a novel abluminal surface coated sirolimus eluting stent with biodegradable polymer matrix

    PubMed Central

    Doshi, Manish; Galloni, Marco; Vignolini, Christina; Vyas, Ashwin; Chevli, Bhavesh; Sheiban, Imad

    2015-01-01

    Background Second generation of drug eluting stents (DES) has attempted to improve safety using abluminal sirolimus drug delivery with biodegradable polymers matrix. The present preclinical study was designed to investigate the safety and efficacy profile of Abluminus™ stents (SES). This is a new coronary stent with sirolimus and biodegradable polymer matrix coated on abluminal stent and balloon surface. Methods SES were compared with two controls: bare metal stent (BMS) and BMS + polymer coated stents (PC). All devices (40 stents) were implanted in porcine coronary arteries with primary endpoint of endothelialization at 7 days and subsequent histological and morphometric evaluations at 7, 30 and 90 days. Results Early endothelialization at seven days was complete in all stents. Histology at 30 days revealed minimum inflammation in all groups and increased at 90 days in PC group while it was absent at 180 days. Thirty day morphometry showed significantly reduction of neointimal area in Abluminus™ (SES 0.96±0.48 mm2; BMS 1.83±0.34 mm2; PC 1.76±0.55 mm2; P<0.05); after 90 days neointimal area was 1.10±0.54 mm2 for SES; 1.92±0.36 mm2 for BMS; and 1.94±0.48 mm2 for PC; P<0.05). Neointimal thickness at 30 and 90 days respectively was 0.15±0.07 and 0.18±0.10 mm for SES, 0.57±0.08 and 0.61±0.09 mm for BMS and 0.52±0.09 and 0.59±0.08 mm, P<0.001 for PC group. Conclusions The most significant experimental evidence appears to be earlier endothelialization at 7 days for SES which led to safety of the device. Efficacy of the device was also observed by a reduced neointimal thickness and minimized inflammatory score at all follow-ups. Termination of antiplatelet at 30 days has not shown any further complications. Polymer thickness was almost in negligible amount at 180 days with no inflammation. PMID:26331109

  18. Comparison of abluminal biodegradable polymer biolimus-eluting stents and durable polymer everolimus-eluting stents in the treatment of coronary bifurcations.

    PubMed

    Costopoulos, Charis; Latib, Azeem; Naganuma, Toru; Sticchi, Alessandro; Ferrarello, Santo; Regazzoli, Damiano; Chieffo, Alaide; Figini, Filippo; Carlino, Mauro; Montorfano, Matteo; Naim, Charbel; Kawaguchi, Masanori; Gerasimou, Argyrios; Giannini, Francesco; Godino, Cosmo; Colombo, Antonio

    2014-05-01

    To compare biodegradable polymer biolimus-eluting (BES) with abluminal drug elution and durable polymer everolimus-eluting (EES) stents in the treatment of bifurcation lesions. The persistence of a polymer in drug-eluting stents (DES) following drug elution has been viewed as a possible culprit for restenosis. DES with biodegradable polymer may thus be associated with improved clinical outcomes, especially in high-risk lesions such as those at bifurcation sites. We performed a retrospective study of consecutive de novo bifurcation lesions treated with EES between October 2006 and October 2011 and BES between February 2008 and March 2012. Study endpoints included major adverse cardiac events (MACE) defined as all-cause death, myocardial infarction (MI), including peri-procedural MI, and target vessel revascularization (TVR) as well as target lesion revascularization (TLR) separately. We analyzed 236 bifurcation lesions treated with either BES (79 lesions in 69 patients) or EES (157 lesions in 154 patients). Patient and procedural characteristics were broadly similar between the two groups. Estimated MACE and TVR rates at 2-year follow-up were similar between the BES and EES groups (MACE = 13.6 ± 4.6% vs. 14.6 ± 3.2% (P = 0.871); TVR = 6.9 ± 3.5% vs. 8.0 ± 2.7% (P = 0.889). No significant differences were noted between the two groups following propensity-score matched analysis. There was no probable or definite stent thrombosis. BES use in the treatment of bifurcation lesions appears to be associated with good clinical outcomes, comparable to those seen with EES, at long-term follow-up. These results are hypothesis-generating and need to be validated with larger studies. Copyright © 2013 Wiley Periodicals, Inc.

  19. Safety and Efficacy of New Biodegradable Polymer-based Sirolimus-Eluting Stents in a Preclinical Model.

    PubMed

    Pérez de Prado, Armando; Pérez Martínez, Claudia; Cuellas Ramón, Carlos; Regueiro Purriños, Marta; López Benito, María; Gonzalo Orden, José Manuel; Rodríguez Altónaga, José Antonio; Estévez Loureiro, Rodrigo; Benito González, Tomás; Viñuela Baragaño, David; Molina Crisol, María; Amorós Aguilar, Marc; Pérez Serranos, Isabel; Vidal Parreu, Arnau; Benavides Montegordo, Ana; Duocastella Codina, Luis; Fernández Vázquez, Felipe

    2017-06-21

    New drug-eluting stents (DES) designed to overcome the limitations of existing devices should initially be tested in preclinical studies. Our objective was to analyze the safety and efficacy of new biodegradable polymer-based DES compared with bare-metal stents (BMS) and commercially available DES in a model of normal porcine coronary arteries. We randomly implanted 101 stents (BMS and biodegradable polymer-based sirolimus-eluting stents: 3 test stent iterations [BD1, BD2, and BD3], Orsiro, Biomime and Biomatrix) in the coronary arteries of 34 domestic pigs. Angiographic and histomorphometric studies were conducted 1 month (n = 83) and 3 months (n = 18) later. The stents were implanted at a stent/artery ratio of 1.31 ± 0.21, with no significant differences between groups. At 1 month, the new test stents (BD1, BD2 and BD3) showed less late loss and angiographic restenosis, as well as lower histologic restenosis and neointimal area (P < .0005), than the BMS. There were no differences in endothelialization, vascular injury, or inflammation between the new test stents and BMS, although the new stents showed higher fibrin deposition (P = .0006). At 3 months, all these differences disappeared, except for a lower neointimal area with the new BD1 stent (P = .027). No differences at any time point were observed between the new test stents and commercially available controls. In this preclinical model, the new biodegradable polymer-based DES studied showed less restenosis than BMS and no significant differences in safety or efficacy vs commercially available DES. Copyright © 2017 Sociedad Española de Cardiología. Published by Elsevier España, S.L.U. All rights reserved.

  20. Ultrathin strut biodegradable polymer sirolimus-eluting stent versus durable polymer everolimus-eluting stent for percutaneous coronary revascularisation (BIOSCIENCE): a randomised, single-blind, non-inferiority trial.

    PubMed

    Pilgrim, Thomas; Heg, Dik; Roffi, Marco; Tüller, David; Muller, Olivier; Vuilliomenet, André; Cook, Stéphane; Weilenmann, Daniel; Kaiser, Christoph; Jamshidi, Peiman; Fahrni, Therese; Moschovitis, Aris; Noble, Stéphane; Eberli, Franz R; Wenaweser, Peter; Jüni, Peter; Windecker, Stephan

    2014-12-13

    Refinements in stent design affecting strut thickness, surface polymer, and drug release have improved clinical outcomes of drug-eluting stents. We aimed to compare the safety and efficacy of a novel, ultrathin strut cobalt-chromium stent releasing sirolimus from a biodegradable polymer with a thin strut durable polymer everolimus-eluting stent. We did a randomised, single-blind, non-inferiority trial with minimum exclusion criteria at nine hospitals in Switzerland. We randomly assigned (1:1) patients aged 18 years or older with chronic stable coronary artery disease or acute coronary syndromes undergoing percutaneous coronary intervention to treatment with biodegradable polymer sirolimus-eluting stents or durable polymer everolimus-eluting stents. Randomisation was via a central web-based system and stratified by centre and presence of ST segment elevation myocardial infarction. Patients and outcome assessors were masked to treatment allocation, but treating physicians were not. The primary endpoint, target lesion failure, was a composite of cardiac death, target vessel myocardial infarction, and clinically-indicated target lesion revascularisation at 12 months. A margin of 3·5% was defined for non-inferiority of the biodegradable polymer sirolimus-eluting stent compared with the durable polymer everolimus-eluting stent. Analysis was by intention to treat. The trial is registered with ClinicalTrials.gov, number NCT01443104. Between Feb 24, 2012, and May 22, 2013, we randomly assigned 2119 patients with 3139 lesions to treatment with sirolimus-eluting stents (1063 patients, 1594 lesions) or everolimus-eluting stents (1056 patients, 1545 lesions). 407 (19%) patients presented with ST-segment elevation myocardial infarction. Target lesion failure with biodegradable polymer sirolimus-eluting stents (69 cases; 6·5%) was non-inferior to durable polymer everolimus-eluting stents (70 cases; 6·6%) at 12 months (absolute risk difference -0·14%, upper limit of one

  1. Light-induced shape-memory polymers

    NASA Astrophysics Data System (ADS)

    Lendlein, Andreas; Jiang, Hongyan; Jünger, Oliver; Langer, Robert

    2005-04-01

    Materials are said to show a shape-memory effect if they can be deformed and fixed into a temporary shape, and recover their original, permanent shape only on exposure to an external stimulus. Shape-memory polymers have received increasing attention because of their scientific and technological significance. In principle, a thermally induced shape-memory effect can be activated by an increase in temperature (also obtained by heating on exposure to an electrical current or light illumination). Several papers have described light-induced changes in the shape of polymers and gels, such as contraction, bending or volume changes. Here we report that polymers containing cinnamic groups can be deformed and fixed into pre-determined shapes-such as (but not exclusively) elongated films and tubes, arches or spirals-by ultraviolet light illumination. These new shapes are stable for long time periods, even when heated to 50°C, and they can recover their original shape at ambient temperatures when exposed to ultraviolet light of a different wavelength. The ability of polymers to form different pre-determined temporary shapes and subsequently recover their original shape at ambient temperatures by remote light activation could lead to a variety of potential medical and other applications.

  2. Light-induced shape-memory polymers.

    PubMed

    Lendlein, Andreas; Jiang, Hongyan; Jünger, Oliver; Langer, Robert

    2005-04-14

    Materials are said to show a shape-memory effect if they can be deformed and fixed into a temporary shape, and recover their original, permanent shape only on exposure to an external stimulus. Shape-memory polymers have received increasing attention because of their scientific and technological significance. In principle, a thermally induced shape-memory effect can be activated by an increase in temperature (also obtained by heating on exposure to an electrical current or light illumination). Several papers have described light-induced changes in the shape of polymers and gels, such as contraction, bending or volume changes. Here we report that polymers containing cinnamic groups can be deformed and fixed into pre-determined shapes--such as (but not exclusively) elongated films and tubes, arches or spirals--by ultraviolet light illumination. These new shapes are stable for long time periods, even when heated to 50 degrees C, and they can recover their original shape at ambient temperatures when exposed to ultraviolet light of a different wavelength. The ability of polymers to form different pre-determined temporary shapes and subsequently recover their original shape at ambient temperatures by remote light activation could lead to a variety of potential medical and other applications.

  3. High Performance Polymer Memory and Its Formation

    DTIC Science & Technology

    2007-04-26

    Std. Z39.18 Final Report to AFOSR High Performance Polymer Memory Device and Its Formation Fund No.: FA9550-04-1-0215 Prepared by Prof. Yang Yang...polystyrene (PS). The metal nanoparticles were prepared by the two-phase 10-5 (b) 10𔄁Polymer film 1a CC , 10, Glass 1 -2 -1 0 1 2 3 4 5 Bias (V) Fig. I...such as copper pthalocyanine (CuPc), 24 ൢ zinc pthalocyanine (ZnPc), 27󈧠 tetracene, 29 and pentacene 30 have been used as donors combined with

  4. Memory operation mechanism of fullerene-containing polymer memory

    SciTech Connect

    Nakajima, Anri Fujii, Daiki

    2015-03-09

    The memory operation mechanism in fullerene-containing nanocomposite gate insulators was investigated while varying the kind of fullerene in a polymer gate insulator. It was cleared what kind of traps and which positions in the nanocomposite the injected electrons or holes are stored in. The reason for the difference in the easiness of programming was clarified taking the role of the charging energy of an injected electron into account. The dependence of the carrier dynamics on the kind of fullerene molecule was investigated. A nonuniform distribution of injected carriers occurred after application of a large magnitude programming voltage due to the width distribution of the polystyrene barrier between adjacent fullerene molecules. Through the investigations, we demonstrated a nanocomposite gate with fullerene molecules having excellent retention characteristics and a programming capability. This will lead to the realization of practical organic memories with fullerene-containing polymer nanocomposites.

  5. Reliable femoral chronic total occlusion model using a thin biodegradable polymer coated copper stent in a porcine model.

    PubMed

    Kim, Nan Yeol; Lim, Kyung Seob; Jeong, Myung Ho; Bae, In Ho; Park, Jun-Kyu; Nah, Jae-Woon; Park, Dae Sung; Lee, So Youn; Jang, Eun Jae; Kim, Jong Min; Kim, Jung Ha; Kee, Hae Jin; Cho, Soo-Na; Sim, Doo Sun; Park, Keun-Ho; Hong, Young Joon; Oh, Sang-Gi; Kim, Sang-Hyung; Ahn, Youngkeun; Kang, Jung Chaee

    2015-04-01

    Chronic total occlusions (CTOs) are common in patients with peripheral arterial disease (PAD). This study aimed to examine the feasibility and reliability of a CTO induced by a thin biodegradable polymer (polyglycolic acid) coated copper stent in a porcine femoral artery. Novel thin biodegradable polymer coated copper stents (9 mm long) were crimped on an angioplasty balloon (4.5 mm diameter × 12 mm length) and inserted into the femoral artery. Histopathologic analysis was performed 35 days after stenting. In five of six stented femoral arteries, severe in-stent restenosis and total occlusion with collateral circulation were observed without adverse effects such as acute stent thrombosis, leg necrosis, or death at 5 weeks. Fibrous tissue deposition, small vascular channels, calcification, and inflammatory cells were observed in hematoxylin-eosin, Carstair's, and von Kossa tissue stains; these characteristics were similar to pathological findings associated with CTOs in humans. The neointima volume measured by micro-computed tomography was 93.9 ± 4.04 % in the stented femoral arteries. CTOs were reliably induced by novel thin biodegradable polymer coated copper stents in porcine femoral arteries. Successful induction of CTOs may provide a practical understanding of their formation and application of an interventional device for CTO treatment.

  6. Biolimus-eluting biodegradable polymer-coated stent versus durable polymer-coated sirolimus-eluting stent in unselected patients receiving percutaneous coronary intervention (SORT OUT V): a randomised non-inferiority trial.

    PubMed

    Christiansen, Evald Høj; Jensen, Lisette Okkels; Thayssen, Per; Tilsted, Hans-Henrik; Krusell, Lars Romer; Hansen, Knud Nørregaard; Kaltoft, Anne; Maeng, Michael; Kristensen, Steen Dalby; Bøtker, Hans Erik; Terkelsen, Christian Juhl; Villadsen, Anton Boel; Ravkilde, Jan; Aarøe, Jens; Madsen, Morten; Thuesen, Leif; Lassen, Jens Flensted

    2013-02-23

    Third-generation biodegradable polymer drug-eluting stents might reduce the risk of stent thrombosis compared with first-generation permanent polymer drug-eluting stents. We aimed to further investigate the effects of a biodegradable polymer biolimus-eluting stent compared with a durable polymer-coated sirolimus-eluting stent in a population-based setting. This randomised, multicentre, all-comer, non-inferiority trial was undertaken at three sites across western Denmark. Eligible patients were aged 18 years or older with chronic stable coronary artery disease or acute coronary syndromes, and at least one coronary artery lesion (>50% diameter stenosis). We randomly assigned patients (1:1) using an independently managed computer-generated allocation sequence to receive either a biolimus-eluting biodegradable polymer stent (Nobori, Terumo, Tokyo, Japan) or a sirolimus-eluting permanent polymer stent (Cypher Select Plus, Cordis, Johnson & Johnson, Warren, NJ, USA). The primary endpoint was a composite of safety (cardiac death, myocardial infarction, definite stent thrombosis) and efficacy (target vessel revascularisation) at 9 months, analysed by intention to treat (non-inferiority margin of 0·02). This trial is registered with ClinicalTrials.gov, number NCT01254981. From July, 2009, to January, 2011, we assigned 1229 patients (1532 lesions) to receive the biolimus-eluting stent and 1239 (1555 lesions) to receive the sirolimus-eluting stent. One patient was lost to follow-up because of emigration. Intention-to-treat analysis showed that 50 (4·1%) patients who were assigned the biolimus-eluting stent and 39 (3·1%) who were assigned the sirolimus-eluting stent met the primary endpoint (risk difference 0·9% [upper limit of one-sided 95% CI 2·1%]; p(non-inferiority)=0·06). Significantly more patients in the biolimus-eluting stent group had definite stent thrombosis at 12 months than did those in the sirolimus-eluting stent group (9 [0·7%] vs 2 [0·2%], risk

  7. One-year outcome of biolimus eluting stent with biodegradable polymer in all comers: the Italian Nobori Stent Prospective Registry.

    PubMed

    Godino, Cosmo; Parenti, Dennis Zavalloni; Regazzoli, Damiano; Rutigliano, David; Lucisano, Luigi; Viani, Giacomo Maria; Spartera, Marco; Chieffo, Alaide; Donahue, Michael; Cappelletti, Alberto; Locuratolo, Nicola; Parisi, Rosario; Fattori, Rossella; Presbitero, Patrizia; Margonato, Alberto; Briguori, Carlo; Sardella, Gennaro; Colombo, Antonio

    2014-11-15

    INSPIRE-1 (Italian Nobori Stent ProspectIve REgistry-1) was designed and conducted to assess clinical performance of Nobori biolimus A9-eluting stent (BES) implantation in an unrestricted "real-world" cohort of patients. Unrestricted consecutive high-risk patients treated with BES with biodegradable polymer (Nobori, Terumo, Tokyo, Japan) between February 2008 and July 2012 were prospectively enrolled in an independent multicenter registry and divided in two groups: complex and non complex lesions. 1066 patients (1589 lesions) treated with Nobori BES were analyzed. The majority of patients (57%) were treated for at least one complex lesion and presented a high-risk clinical profile (previous CABG 17.6%, diabetes mellitus 33.1%, chronic kidney disease 14.3%). Angiographic success rate was achieved in 96.2% cases. At 1 year, the primary endpoint, (composite of cardiac death, myocardial infarction, and clinically driven target vessel revascularization), occurred in 39 (4.0%) patients, and was higher in the complex lesions (5.2% vs. 2.5%, P = 0.032). Target lesion failure (TLF, secondary endpoint) occurred in 45 (4.6%) patients, and was more frequent in the complex lesions group (6.2% vs. 2.7%, P = 0.011), mainly due to a higher incidence of any target lesion revascularization (4.8% vs. 2.7%; P = 0.095). Definite and probable stent thrombosis (ST) rate was 0.6% and 0.5% respectively, with no difference between groups. In unrestricted daily practice, BESs were implanted predominantly in high risk patients with complex lesions. Despite this, the Nobori BES was associated with a relatively low rate of primary endpoint and TLF, with a higher risk in patients with complex lesions. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  8. Polymer-free amphilimus-eluting stent versus biodegradable polymer biolimus-eluting stent in patients with and without diabetes mellitus.

    PubMed

    Godino, Cosmo; Pivato, Carlo Andrea; Chiarito, Mauro; Donahue, Michael; Testa, Luca; Colantonio, Riccardo; Cappelletti, Alberto; Milazzo, Diego; Parisi, Rosario; Nicolino, Annamaria; Moshiri, Shahram; Aprigliano, Gianfranco; Palloshi, Altin; Zavalloni Parenti, Dennis; Rutigliano, David; Locuratolo, Nicola; Melillo, Francesco; Scotti, Andrea; Arrigoni, Luca; Montorfano, Matteo; Fattori, Rossella; Presbitero, Patrizia; Sardella, Gennaro; Bedogni, Francesco; Margonato, Alberto; Briguori, Carlo; Colombo, Antonio

    2017-10-15

    This study sought to compare clinical outcome of polymer-free amphilimus-eluting stent (PF-AES) versus biodegradable-polymer biolimus-eluting stent (BD-BES) in "all-comer" diabetes mellitus (DM) and non-DM patients who underwent percutaneous coronary intervention. The PF-AES has shown promising preliminary results in patients with DM. Data from 2 multicentre-national registries (the ASTUTE and the INSPIRE-1) were used to analyse 1776 patients stratified in non-DM and DM. A double 1:1 propensity-score matched analysis (PF-AES vs. BD-BES) was performed in each group to adjust for clinical and procedural characteristics. Primary stent-efficacy and stent-safety endpoints were 1-year target-lesion revascularization (TLR) and target-lesion failure (TLF, composed of cardiac-death, target-vessel myocardial infarction and any TLR). After propensity-score matching, 850 patients were stratified as non-DM (425 PF-AES/425 BD-BES) and 480 as DM patients (240 PF-AES/240 BD-BES). Both TLF (20 of 425 [5%] vs. 24 of 425 [6%]; Plog-rank=0.527) and TLR (9 of 425 [2%] vs. 18 of 425 [4%]; Plog-rank=0.079) were similar between PF-AES and BD-BES in non-DM patients. In DM, TLF (12 of 240 [5%] vs. 31 of 240 [13%]; Plog-rank=0.002) and TLR (9 of 240 [4%] vs. 21 of 240 [9%]; Plog-rank=0.019) were significantly lower in PF-AES compared to BD-BES. Upon multivariate analysis, the most powerful predictors of TLF were chronic kidney disease in non-DM (OR 4.24, 95% CI: 2.07-8.70, p<0.001) and stent type in DM patients (OR 2.76, 1.36-5.56, p=0.005). This matched-cohort study suggests that PF-AES has better safety and efficacy profile than BD-BES in patients with DM. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Development of multifunctional shape memory polymer foams

    NASA Astrophysics Data System (ADS)

    Song, Janice J.; Srivastava, Ijya; Naguib, Hani E.

    2015-05-01

    Shape memory polymers (SMP) are a class of stimuli-responsive materials which are able to respond to external stimulus such as temperature and deformation by changing their shape, and return to their original shape upon reversal or removal of the external stimulus. Although SMP materials have been studied extensively and have been used in a wide range of applications such as medicine, aerospace, and robotics, only few studies have looked at the potential of designing multifunctional SMP foams and blends. In this study, we investigate the feasibility of a design of SMP foam materials and blends. The actuator construct will contain a core SMP epoxy and blend of polylactic acid and polyurethane. The effects of the processing parameters of shape memory polymer (SMP) foams on the shape memory effect (SME) were investigated. The solid state foaming technique was employed to obtain the desired foamed cellular structure. One particular point of interest is to understand how the processing parameters affect the SMP and its glass transition temperature (Tg). By correctly tailoring these parameters it is possible to modify the SMP to have an improved shape memory effect SME.

  10. Mussel inspired coating of a biocompatible cyclodextrin based polymer onto CoCr vascular stents.

    PubMed

    Sobocinski, Jonathan; Laure, William; Taha, Mariam; Courcot, Elisabeth; Chai, Feng; Simon, Nicolas; Addad, Ahmed; Martel, Bernard; Haulon, Stephan; Woisel, Patrice; Blanchemain, Nicolas; Lyskawa, Joel

    2014-03-12

    During the past decade, drug-eluting stents (DES) have been widely used for the treatment of occlusive coronary artery diseases. They are supposed to reduce the incidence of early in-stent restenosis by the elution of highly hydrophobic antiproliferative drugs. Nevertheless, the absence of long-term activity of these devices is responsible for late acute thrombosis probably due to the delayed re-endothelialization of the arterial wall over the bare metallic stent struts. Thus, a new generation of DES with a sustained release of therapeutic agents is required to improve long-term results of these devices. In this article, we report an original functionalization of CoCr vascular devices with a hydrophilic, biocompatible and biodegradable cyclodextrins based polymer which acts as a reservoir for lipophilic drugs allowing the sustained release of antiproliferative drugs. In this setting, polydopamine (PDA), a strong adhesive biopolymer, was applied as a first coating layer onto the surface of the metallic CoCr device in order to promote the strong anchorage of a cyclodextrin polymer. This polymer was generated "in situ" from the methylated cyclodextrins and citric acid as a cross-linking agent through a polycondensation reaction. After optimization of the grafting process, the amount of cyclodextrin polymer coated onto the CoCr device was quantified by colorimetric titrations and the resulting film was characterized by scanning electron microscopy (SEM) investigations. The cytocompatibility of the resulting coated film was assessed by cell proliferation and vitality tests. Finally, the ability of this coated device to act as a drug-eluting system was evaluated with paclitaxel, a strong hydrophobic antiproliferative drug, a reference drug used in current vascular drug-eluting stents.

  11. Long-term clinical outcomes of biodegradable polymer biolimus-eluting stents versus durable polymer everolimus-eluting stents in patients with coronary artery disease: three-year follow-up of the COMPARE II (Abluminal biodegradable polymer biolimus-eluting stent versus durable polymer everolimus-eluting stent) trial.

    PubMed

    Vlachojannis, Georgios J; Smits, Pieter C; Hofma, Sjoerd H; Togni, Mario; Vázquez, Nicolás; Valdés, Mariano; Voudris, Vassilis; Puricel, Serban; Slagboom, Ton; Goy, Jean-Jacques; den Heijer, Peter; van der Ent, Martin

    2015-07-01

    The aim of this analysis was to compare the long-term safety and efficacy of the biodegradable polymer biolimus-eluting stent (BES) with that of the durable polymer everolimus-eluting stent (EES). The COMPARE II study was a prospective, randomised, multicentre, all-comers trial in which 2,707 patients were randomly allocated (2:1) to BES or EES. The pre-specified endpoint at three years was major adverse cardiac events (MACE), a composite of cardiac death, non-fatal myocardial infarction (MI), or target vessel revascularisation (TVR). Moreover, the combined endpoint all-cause death or MI was analysed as a safety, and TVR as an efficacy measure. Three-year follow-up was available in 2,683 patients (99.1%). At three years, MACE occurred in 213 patients (11.9%) in the BES group and in 101 patients (11.1 %) in the EES group (p=0.57). The rate of the combined safety endpoint all-cause death or MI was 9.3% in the BES group vs. 8.4% (p=0.52), while the efficacy measure TVR was 7.6% in BES vs. 6.5% (p=0.27). Interestingly, definite stent thrombosis rates did not differ between groups (1.2% for BES vs. 0.8%, p=0.33). At three-year follow-up, MACE as well as safety and efficacy measures including stent thrombosis were not statistically different between the biodegradable polymer-coated BES and the durable polymer-coated EES. ClinicalTrials.gov Identifier: NCT01233453.

  12. A novel polymer-free ciglitazone-coated vascular stent: in vivo and ex vivo analysis of stent endothelialization in a rabbit iliac artery model

    PubMed Central

    Otto, Sylvia; Jaeger, Kristin; Kolodgie, Frank D.; Muehlstaedt, Diana; Franz, Marcus; Bischoff, Sabine; Schubert, Harald; Figulla, Hans R.; Virmani, Renu; Poerner, Tudor C.

    2016-01-01

    Aim Peroxisome proliferator-activated receptor-gamma (PPARg) agonists have known pleiotropic cardiovascular effects with favourable properties in vascular remodeling, and specifically in suppression of vascular smooth muscle cell proliferation. A novel vascular stent coating using the PPARg ligand ciglitazone (CCS) was investigated regarding its effects on endothelialization after 7 and 28 days. Methods Microporous bare metal stents (BMS) were coated with ciglitazone by ultrasonic flux with a load of 255 μg ciglitazone/stent. SixteenNew Zealand white rabbits, fed a with high cholesterol diet, underwent stent implantation in both iliac arteries. Everolimus-eluting stents (EES) and BMS were comparators. Histology (CD 31 immunostaining, confocal and scanning electron microscopy, morphometry) was performed after 7 and 28 days and by OCT (optical coherence tomography) in vivo after 28 days. Results Microscopy showed comparable results with near complete endothelialization in CCS and BMS (%CD31 above stent struts after 7 days: 67.92±36.35 vs. 84.48±23.86; p = 0.55; endothel % above stent struts: 77.22±27.9 vs. 83.89±27.91; p = 0.78). EES were less endothelialized with minimal fibrin deposition, not found in BMS and CCS (% CD 31 above struts after 28 days, BMS: 100.0±0.0 vs. EES: 95.9±3.57 vs. CCS: 100.0±0.0; p = 0.0292). OCT revealed no uncovered struts in all stents after 28 days. Conclusions Polymer-free coating with ciglitazone, a PPARg agonist is feasible and stable over time. Our data prove unimpaired endothelial coverage of a ciglitazone-coated vascular stent system by histology and OCT. Thus, this PPARg agonist coating deserves further investigation to evaluate its potency on local neointimal suppression. PMID:27613845

  13. Fabrication of a novel polymer-free nanostructured drug-eluting coating for cardiovascular stents.

    PubMed

    Wang, Yao; Zhang, Wenli; Zhang, Jixi; Sun, Wei; Zhang, Ruiyan; Gu, Hongchen

    2013-10-23

    Angioplasty with stents is the most important method for the treatment of coronary artery disease (CAD). However, the drug-eluting stents (DES) that are widely used have the increased risks of inflammatory reactions and late stent thrombosis (LST) because of the persistence of the polymer coatings. To improve the biosafety, a novel polymer-free-composite drug-eluting coating composed of magnetic mesoporous silica nanoparticles (MMSNs) and carbon nanotubes (CNTs) was constructed using the electrophoretic deposition (EPD) method in this study. A crack-free two-layered coating with impressive network nanotopologies was successfully obtained by regulating the composition and structures. This nanostructured coating exhibits excellent mechanical flexibility and blood compatibility in vitro, and the drug-loading and release performance is satisfactory as well. The in vivo study shows that this composite coating has the obvious advantage of rapid endothelialization because of its unique 3D nanostructured topology in comparison with the commercial polymer-coated DES. This study aims to provide new ideas and reliable data to design novel functional coatings that could accelerate the re-endothelialization process and avoid inflammatory reactions, thus improving the in vivo biosafety of DES.

  14. Comparison of the SYNERGY with the PROMUS (XIENCE V) and bare metal and polymer-only Element control stents in porcine coronary arteries.

    PubMed

    Wilson, Gregory J; Huibregtse, Barbara A; Pennington, Douglas E; Dawkins, Keith D

    2012-06-20

    This study evaluated vascular compatibility of the novel platinum chromium alloy Element stent platform delivering abluminal everolimus from a poly-lactide-co-glycolide bioabsorbable polymer (SYNERGY stent), currently undergoing clinical trial, compared with the PROMUS (XIENCE V) and bare metal and polymer-only Element stents. Stents (n=161) were implanted one per coronary artery in 72 swine at a stent-to-artery ratio of 1.1:1. Similar numbers of each device group were explanted at each of 30, 90, 180, and 360 days (except no PROMUS (XIENCE V) stent at 360 days) for pathological analysis. There was no stent thrombosis, myocardial infarction, or strut fractures in any group. Vascular response was similar between the SYNERGY and PROMUS (XIENCE V) stents, with no thrombi and complete endothelialisation on both scanning electron microscopy and histology at 30, 90 and 180 days. There were no significant differences for the morphologic parameters of luminal thrombus, endothelial cell coverage, strut tissue coverage, inflammation, internal elastic lamina (IEL) disruption, external elastic lamina (EEL) disruption and medial smooth muscle cell loss across device groups or between time points, but there was mild but greater (p<0.0001) para-strut fibrin at 30 days for both drug-eluting stents (DES) compared with the bare and polymer-only controls; this difference completely dissipated by 90 days. Inflammation was predominantly minimal to mild for all device types. No morphometric parameters, including intimal thickness, stent profile-based area stenosis, and EEL area were significantly different when comparing the SYNERGY stent with the bare metal Element and polymer-only Element control stents at 90, 180 and 360 days. In this non-injured porcine coronary artery model, the bioabsorbable polymer SYNERGY stent demonstrated vascular compatibility equivalent to the PROMUS (XIENCE V) stent and to the bare metal and polymer-only Element stents.

  15. Cyclic behaviors of amorphous shape memory polymers.

    PubMed

    Yu, Kai; Li, Hao; McClung, Amber J W; Tandon, Gyaneshwar P; Baur, Jeffery W; Qi, H Jerry

    2016-04-07

    Cyclic loading conditions are commonly encountered in the applications of shape memory polymers (SMPs), where the cyclic characteristics of the materials determine their performance during the service life, such as deformation resistance, shape recovery speed and shape recovery ratio. Recent studies indicate that in addition to the physical damage or some other irreversible softening effects, the viscoelastic nature could also be another possible reason for the degraded cyclic behavior of SMPs. In this paper, we explore in detail the influence of the viscoelastic properties on the cyclic tension and shape memory (SM) behavior of an epoxy based amorphous thermosetting polymer. Cyclic experiments were conducted first, which show that although the epoxy material does not have any visible damage or irreversible softening effect during deformation, it still exhibits obvious degradation in the cyclic tension and SM behaviors. A linear multi-branched model is utilized to assist in the prediction and understanding of the mechanical responses of amorphous SMPs. Parametric studies based on the applied model suggest that the shape memory performance can be improved by adjusting programming and recovery conditions, such as lowering the loading rate, increasing the programming temperature, and reducing the holding time.

  16. Shape memory polymer therapeutic devices for stroke

    NASA Astrophysics Data System (ADS)

    Wilson, Thomas S.; Small, Ward, IV; Benett, William J.; Bearinger, Jane P.; Maitland, Duncan J.

    2005-11-01

    Shape memory polymers (SMPs) are attracting a great deal of interest in the scientific community for their use in applications ranging from light weight structures in space to micro-actuators in MEMS devices. These relatively new materials can be formed into a primary shape, reformed into a stable secondary shape, and then controllably actuated to recover their primary shape. The first part of this presentation will be a brief review of the types of polymeric structures which give rise to shape memory behavior in the context of new shape memory polymers with highly regular network structures recently developed at LLNL for biomedical devices. These new urethane SMPs have improved optical and physical properties relative to commercial SMPs, including improved clarity, high actuation force, and sharper actuation transition. In the second part of the presentation we discuss the development of SMP based devices for mechanically removing neurovascular occlusions which result in ischemic stroke. These devices are delivered to the site of the occlusion in compressed form, are pushed through the occlusion, actuated (usually optically) to take on an expanded conformation, and then used to dislodge and grip the thrombus while it is withdrawn through the catheter.

  17. Shape Memory Polymer Therapeutic Devices for Stroke

    SciTech Connect

    Wilson, T S; Small IV, W; Benett, W J; Bearinger, J P; Maitland, D J

    2005-10-11

    Shape memory polymers (SMPs) are attracting a great deal of interest in the scientific community for their use in applications ranging from light weight structures in space to micro-actuators in MEMS devices. These relatively new materials can be formed into a primary shape, reformed into a stable secondary shape, and then controllably actuated to recover their primary shape. The first part of this presentation will be a brief review of the types of polymeric structures which give rise to shape memory behavior in the context of new shape memory polymers with highly regular network structures recently developed at LLNL for biomedical devices. These new urethane SMPs have improved optical and physical properties relative to commercial SMPs, including improved clarity, high actuation force, and sharper actuation transition. In the second part of the presentation we discuss the development of SMP based devices for mechanically removing neurovascular occlusions which result in ischemic stroke. These devices are delivered to the site of the occlusion in compressed form, are pushed through the occlusion, actuated (usually optically) to take on an expanded conformation, and then used to dislodge and grip the thrombus while it is withdrawn through the catheter.

  18. Micro devices using shape memory polymer patches for mated connections

    DOEpatents

    Lee, Abraham P.; Fitch, Joseph P.

    2000-01-01

    A method and micro device for repositioning or retrieving miniature devices located in inaccessible areas, such as medical devices (e.g., stents, embolic coils, etc.) located in a blood vessel. The micro repositioning or retrieving device and method uses shape memory polymer (SMP) patches formed into mating geometries (e.g., a hoop and a hook) for re-attachment of the deposited medical device to a catheter or guidewire. For example, SMP or other material hoops are formed on the medical device to be deposited in a blood vessel, and SMP hooks are formed on the micro device attached to a guidewire, whereby the hooks on the micro device attach to the hoops on the medical device, or vice versa, enabling deposition, movement, re-deposit, or retrieval of the medical device. By changing the temperature of the SMP hooks, the hooks can be attached to or released from the hoops located on the medical device. An exemplary method for forming the hooks and hoops involves depositing a sacrificial thin film on a substrate, patterning and processing the thin film to form openings therethrough, depositing or bonding SMP materials in the openings so as to be attached to the substrate, and removing the sacrificial thin film.

  19. Five-year clinical follow-up of a randomized comparison of a polymer-free sirolimus-eluting stent versus a polymer-based paclitaxel-eluting stent in patients with diabetes mellitus (LIPSIA Yukon trial).

    PubMed

    Stiermaier, Thomas; Heinz, Anja; Schloma, Denis; Kleinertz, Klaus; Dänschel, Wilfried; Erbs, Sandra; Linke, Axel; Boudriot, Enno; Lauer, Bernward; Schuler, Gerhard; Thiele, Holger; Desch, Steffen

    2014-02-15

    The long-term performance of polymer-free stent systems in patients with diabetes mellitus has not been investigated extensively. This study reports long-term results of the LIPSIA Yukon trial which compared the polymer-free sirolimus-eluting Yukon Choice stent with the polymer-based paclitaxel-eluting Taxus Liberté stent in this subpopulation. At 9 months, the Yukon Choice stent failed to show non-inferiority in terms of the primary end point late lumen loss, while no significant difference in clinical outcome was detected. The LIPSIA Yukon trial randomized 240 patients with diabetes mellitus to a polymer-free sirolimus eluting stent (Yukon Choice, Translumina) versus a polymer-based paclitaxel-eluting stent (Taxus Liberté, Boston Scientific). Clinical follow-up was conducted with a standardized telephone follow-up and all events were centrally adjudicated. Follow-up was available for 98.3% of patients after a median of 5.0 years. The incidence of all-cause death (16.9% versus 14.0%, P = 0.67), respectively definite or presumed cardiovascular death (7.6% versus 8.8%, P = 0.94) were similar in the Yukon Choice and the Taxus Liberté group. There were no significant differences in the rates of myocardial infarction (9.3% versus 7.9%, P = 0.88), definite stent thrombosis (0.8% versus 0.9%, P = 1.0), target lesion revascularization (15.3% versus 15.8%, P = 1.0), target vessel revascularization (18.6% versus 23.7%, P = 0.44), non-target vessel revascularization (18.6% versus 26.3%, P = 0.21), and stroke (3.4% versus 4.4%, P = 0.96) between patients assigned to the Yukon Choice and the Taxus Liberté stent. At 5 years of follow-up, clinical outcome was similar between the polymer-free sirolimus-eluting Yukon Choice stent and the polymer-based paclitaxel-eluting Taxus Liberté stent. Copyright © 2013 Wiley Periodicals, Inc.

  20. Medical applications of shape memory polymers.

    PubMed

    Sokolowski, Witold; Metcalfe, Annick; Hayashi, Shunichi; Yahia, L'Hocine; Raymond, Jean

    2007-03-01

    Shape memory polymers (SMP) are lightweight, have a high strain/shape recovery ability, are easy to process, and required properties can be tailored for variety of applications. Recently a number of medical applications have been considered and investigated, especially for polyurethane-based SMP. SMP materials were found to be biocompatible, non-toxic and non-mutagenic. The glass transition temperature (T(g)) can be tailored for shape restoration/self-deployment of clinical devices when inserted in the human body. Newly developed SMP foams, together with cold hibernated elastic memory (CHEM) processing, further broaden their potential biomedical applications. Polyurethane-based SMP are described here and major advantages are identified over other medical materials. Some SMP applications are already used in a clinical setting, whereas others are still in development. Lately, several important applications are being considered for CHEM foams as self-deployable vascular and coronary devices. One example is the endovascular treatment of aneurysms.

  1. New stent surface materials: the impact of polymer-dependent interactions of human endothelial cells, smooth muscle cells, and platelets.

    PubMed

    Busch, Raila; Strohbach, Anne; Rethfeldt, Stefanie; Walz, Simon; Busch, Mathias; Petersen, Svea; Felix, Stephan; Sternberg, Katrin

    2014-02-01

    Despite the development of new coronary stent technologies, in-stent restenosis and stent thrombosis are still clinically relevant. Interactions of blood and tissue cells with the implanted material may represent an important cause of these side effects. We hypothesize material-dependent interaction of blood and tissue cells. The aim of this study is accordingly to investigate the impact of vascular endothelial cells, smooth muscle cells and platelets with various biodegradable polymers to identify a stent coating or platform material that demonstrates excellent endothelial-cell-supportive and non-thrombogenic properties. Human umbilical venous endothelial cells, human coronary arterial endothelial cells and human coronary arterial smooth muscle cells were cultivated on the surfaces of two established biostable polymers used for drug-eluting stents, namely poly(ethylene-co-vinylacetate) (PEVA) and poly(butyl methacrylate) (PBMA). We compared these polymers to new biodegradable polyesters poly(l-lactide) (PLLA), poly(3-hydroxybutyrate) (P(3HB)), poly(4-hydroxybutyrate) (P(4HB)) and a polymeric blend of PLLA/P(4HB) in a ratio of 78/22% (w/w). Biocompatibility tests were performed under static and dynamic conditions. Measurement of cell proliferation, viability, glycocalix width, eNOS and PECAM-1 mRNA expression revealed strong material dependency among the six polymer samples investigated. Only the polymeric blend of PLLA/P(4HB) achieved excellent endothelial markers of biocompatibility. Data show that PLLA and P(4HB) tend to a more thrombotic response, whereas the polymer blend is characterized by a lower thrombotic potential. These data demonstrate material-dependent endothelialization, smooth muscle cell growth and thrombogenicity. Although polymers such as PEVA and PBMA are already commonly used for vascular implants, they did not sufficiently meet the criteria for biocompatibility. The investigated biodegradable polymeric blend PLLA/P(4HB) evidently represents a

  2. Biodegradable Polymer-Based Sirolimus-Eluting Stents With Differing Elution and Absorption Kinetics: The PANDA III Trial.

    PubMed

    Xu, Bo; Gao, Runlin; Yang, Yuejin; Cao, Xuebin; Qin, Lei; Li, Yi; Li, Zhanquan; Li, Xueqi; Lin, Hailong; Guo, Yong; Ma, Yitong; Wang, Jian'an; Nie, Shaoping; Xu, Liang; Cao, Eric; Guan, Changdong; Stone, Gregg W

    2016-05-17

    Whether the rate of drug elution and polymer absorption affects clinical outcomes of biodegradable polymer-based drug-eluting stents (DES) is unknown. The widely used polylactide polymer-based Excel stent (JW Medical, Weihai, China) elutes sirolimus within 180 days, and the polylactide polymer is completely absorbed within 6 to 9 months. In contrast, the poly-lactide-co-glycolide polymer-based BuMA stent (Sino Medical, Tianjin, China) elutes sirolimus within 30 days, and the poly-lactide-co-glycolide polymer is completely absorbed within 3 months. Thus, both metallic DES elute sirolimus, isolating major differences to the polymer and elution kinetics. The goal of this study was to compare the safety and effectiveness between the BuMA sirolimus-eluting stent (SES) and Excel SES in an "all-comers" population. PANDA III was a multicenter trial with few exclusion criteria, powered for sequential noninferiority and superiority testing. The primary endpoint was 1-year target lesion failure (TLF), a composite of cardiac death, target vessel myocardial infarction, or ischemia-driven target lesion revascularization. Between December 2013 and August 2014, 2,348 patients were randomly assigned to treatment with BuMA (n = 1,174) or Excel SES (n = 1,174). The 1-year primary endpoint of TLF occurred in 6.4% of patients in each group (difference: 0.06%; 95% confidence interval: 1.93% to 2.04%; pnoninferiority = 0.0003; psuperiority = 0.95). There were no significant between-group differences in any of the secondary endpoints other than the incidence of definite/probable stent thrombosis, which occurred less frequently with the BuMA stent (0.5% vs. 1.3%; log-rank p = 0.048). The BuMA SES was demonstrated to be noninferior to the Excel SES for 1-year TLF, with a lower incidence of stent thrombosis. (Comparison of BuMA eG Based BioDegradable Polymer Stent With EXCEL Biodegradable Polymer Sirolimus-eluting Stent in "Real-World" Practice [PANDA-III]; NCT02017275). Copyright

  3. Very thin strut biodegradable polymer everolimus-eluting and sirolimus-eluting stents versus durable polymer zotarolimus-eluting stents in allcomers with coronary artery disease (BIO-RESORT): a three-arm, randomised, non-inferiority trial.

    PubMed

    von Birgelen, Clemens; Kok, Marlies M; van der Heijden, Liefke C; Danse, Peter W; Schotborgh, Carl E; Scholte, Martijn; Gin, R Melvyn Tjon Joe; Somi, Samer; van Houwelingen, K G; Stoel, M G; de Man, Frits H A F; Louwerenburg, J Hans W; Hartmann, Marc; Zocca, Paolo; Linssen, Gerard C M; van der Palen, Job; Doggen, Carine J M; Löwik, Marije M

    2016-11-26

    In patients with coronary artery disease, treated with durable polymer-coated drug-eluting stents, the life-long presence of the polymer might delay arterial healing. Novel very thin strut biodegradable polymer stents, which leave only a bare metal stent after polymer resorption, might improve long-term outcome. We investigated in allcomers the safety and efficacy of three stents eluting either everolimus, sirolimus, or zotarolimus, often clinically used but never compared, of which the biodegradable polymer everolimus-eluting stent was never before assessed in allcomers. The large-scale, investigator-initiated, multicentre, assessor and patient blinded, three-arm, randomised, BIO-RESORT non-inferiority trial was done at four clinical sites in the Netherlands. All-comer patients were aged 18 years or older, capable of providing informed consent, and required a percutaneous coronary intervention with drug-eluting stent implantation according to clinical guidelines or the operators' judgment. Exclusion criteria were: participation in another randomised drug or device study before reaching the primary endpoint of that study; planned surgery necessitating interruption of dual antiplatelet therapy within the first 6 months; known intolerance to components of the investigational product or medication required; uncertainty about the adherence to follow-up procedures or an assumed life expectancy of less than 1 year; or known pregnancy. Web-based computer-generated allocation sequences randomly assigned patients (1:1:1) to treatment with very thin strut biodegradable polymer everolimus-eluting or sirolimus-eluting stents (which differ substantially in type, amount, distribution, and resorption speed of their respective coating), or thin strut durable polymer zotarolimus-eluting stents. The primary endpoint was a composite of safety (cardiac death or target vessel-related myocardial infarction) and efficacy (target vessel revascularisation) at 12 months of follow up with a

  4. Porous inorganic—organic shape memory polymers

    PubMed Central

    Zhang, Dawei; Burkes, William L.; Schoener, Cody A.; Grunlan, Melissa A.

    2012-01-01

    Thermoresponsive shape memory polymers (SMPs) are a type of stimuli-sensitive materials that switch from a temporary shape back to their permanent shape upon exposure to heat. While the majority of SMPs have been fabricated in the solid form, porous SMP foams exhibit distinct properties and are better suited for certain applications, including some in the biomedical field. Like solid SMPs, SMP foams have been restricted to a limited group of organic polymer systems. In this study, we prepared inorganic–organic SMP foams based on the photochemical cure of a macromer comprised of inorganic polydimethylsiloxane (PDMS) segments and organic poly(ε-caprolactone) (PCL) segments, diacrylated PCL40-block-PDMS37-block-PCL40. To achieve tunable pore size with high interconnectivity, the SMP foams were prepared via a refined solvent-casting/particulate-leaching (SCPL) method. By varying design parameters such as degree of salt fusion, macromer concentration in the solvent and salt particle size, the SMP foams with excellent shape memory behavior and tunable pore size, pore morphology, and modulus were obtained. PMID:22956854

  5. Methods of Making and Using Shape Memory Polymer Composite Patches

    NASA Technical Reports Server (NTRS)

    Hood, Patrick J.

    2011-01-01

    A method of repairing a composite component having a damaged area including: laying a composite patch over the damaged area: activating the shape memory polymer resin to easily and quickly mold said patch to said damaged area; deactivating said shape memory polymer so that said composite patch retains the molded shape; and bonding said composite patch to said damaged part.

  6. Polymer-based paclitaxel-eluting coronary stents. Clinical results in de novo lesions.

    PubMed

    Chieffo, Alaide; Colombo, Antonio

    2004-03-01

    Drug-eluting stents (DES) represent one of the fastest-growing fields in interventional cardiology today. Paclitaxel (Taxol) is a potent antiproliferative agent that shifts the microtubule equilibrium toward assembly, favoring the formation of abnormally stable microtubules with blockage of the cell cycle in G2/M phases. A series of clinical trials (TAXUS I through VI) have been designed to test the safety and the efficacy of polymer- based paclitaxel-eluting stents (Taxus, Boston Scientific, Natick, MA, USA) at the dosage 1 microg/mm(2) in a variety of clinical settings. Except for TAXUS III and TAXUS V-ISR, in the TAXUS program de novo lesions have been evaluated. Two different release kinetics were evaluated: slow-release (SR) and moderate- release (MR) formulation. Very encouraging preliminary results also come from the "real world" data on Taxus SR stent collected in the "Web-based taxus Intercontinental obServational Data TransitiOnal registry prograM" (the WISDOM Registry) and in the "Real Life Polymer-Based Paclitaxel Registry" (the Real Life PBPaclitaxel Registry). The remarkable positive results obtained from the randomized trials offer the interventional cardiologist another effective option (besides the Cypher stent, Cordis a J & J, Warren, NJ, USA) to treat patients with a DES. This fact may certainly drive the competition and, ultimately, lower the cost. The final answer will probably come from the ongoing registries and prospective trials versus coronary artery bypass grafting (CABG), which will reveal the real impact of this new technology on everyday practice.

  7. High-Temperature Shape Memory Polymers

    NASA Technical Reports Server (NTRS)

    Yoonessi, Mitra; Weiss, Robert A.

    2012-01-01

    physical conformation changes when exposed to an external stimulus, such as a change in temperature. Such materials have a permanent shape, but can be reshaped above a critical temperature and fixed into a temporary shape when cooled under stress to below the critical temperature. When reheated above the critical temperature (Tc, also sometimes called the triggering or switching temperature), the materials revert to the permanent shape. The current innovation involves a chemically treated (sulfonated, carboxylated, phosphonated, or other polar function group), high-temperature, semicrystalline thermoplastic poly(ether ether ketone) (Tg .140 C, Tm = 340 C) mix containing organometallic complexes (Zn++, Li+, or other metal, ammonium, or phosphonium salts), or high-temperature ionic liquids (e.g. hexafluorosilicate salt with 1-propyl-3- methyl imidazolium, Tm = 210 C) to form a network where dipolar or ionic interactions between the polymer and the low-molecular-weight or inorganic compound forms a complex that provides a physical crosslink. Hereafter, these compounds will be referred to as "additives". The polymer is semicrystalline, and the high-melt-point crystals provide a temporary crosslink that acts as a permanent crosslink just so long as the melting temperature is not exceeded. In this example case, the melting point is .340 C, and the shape memory critical temperature is between 150 and 250 C. PEEK is an engineering thermoplastic with a high Young fs modulus, nominally 3.6 GPa. An important aspect of the invention is the control of the PEEK functionalization (in this example, the sulfonation degree), and the thermal properties (i.e. melting point) of the additive, which determines the switching temperature. Because the compound is thermoplastic, it can be formed into the "permanent" shape by conventional plastics processing operations. In addition, the compound may be covalently cross - linked after forming the permanent shape by S-PEEK by applying ionizing

  8. Memristive learning and memory functions in polyvinyl alcohol polymer memristors

    NASA Astrophysics Data System (ADS)

    Lei, Yan; Liu, Yi; Xia, Yidong; Gao, Xu; Xu, Bo; Wang, Suidong; Yin, Jiang; Liu, Zhiguo

    2014-07-01

    Polymer based memristive devices can offer simplicity in fabrication and at the same time promise functionalities for artificial neural applications. In this work, inherent learning and memory functions have been achieved in polymer memristive devices employing Polyvinyl Alcohol. The change in conduction in such polymer devices strongly depends on the pulse amplitude, duration and time interval. Through repetitive stimuli training, temporary short-term memory can transfer into consolidated long-term memory. These behaviors bear remarkable similarities to certain learning and memory functions of biological systems.

  9. A mechanistic model for drug release in PLGA biodegradable stent coatings coupled with polymer degradation and erosion.

    PubMed

    Zhu, Xiaoxiang; Braatz, Richard D

    2015-07-01

    Biodegradable poly(d,l-lactic-co-glycolic acid) (PLGA) coating for applications in drug-eluting stents has been receiving increasing interest as a result of its unique properties compared with biodurable polymers in delivering drug for reducing stents-related side effects. In this work, a mathematical model for describing the PLGA degradation and erosion and coupled drug release from PLGA stent coating is developed and validated. An analytical expression is derived for PLGA mass loss that predicts multiple experimental studies in the literature. An analytical model for the change of the number-average degree of polymerization [or molecular weight (MW)] is also derived. The drug transport model incorporates simultaneous drug diffusion through both the polymer solid and the liquid-filled pores in the coating, where an effective drug diffusivity model is derived taking into account factors including polymer MW change, stent coating porosity change, and drug partitioning between solid and aqueous phases. The model is used to describe in vitro sirolimus release from PLGA stent coating, and demonstrates the significance of simultaneous sirolimus release via diffusion through both polymer solid and pore space. The proposed model is compared to existing drug transport models, and the impact of model parameters, limitations and possible extensions of the model are also discussed.

  10. A Mechanistic Model for Drug Release in PLGA Biodegradable Stent Coatings Coupled with Polymer Degradation and Erosion

    PubMed Central

    Zhu, Xiaoxiang; Braatz, Richard D.

    2015-01-01

    Biodegradable poly(D,L-lactic-co-glycolic acid) (PLGA) coating for applications in drug-eluting stents has been receiving increasing interest as a result of its unique properties compared with biodurable polymers in delivering drug for reducing stents-related side effects. In this work, a mathematical model for describing the PLGA degradation and erosion and coupled drug release from PLGA stent coating is developed and validated. An analytical expression is derived for PLGA mass loss that predicts multiple experimental studies in the literature. An analytical model for the change of the number-average degree of polymerization (or molecular weight) is also derived. The drug transport model incorporates simultaneous drug diffusion through both the polymer solid and the liquid-filled pores in the coating, where an effective drug diffusivity model is derived taking into account factors including polymer molecular weight change, stent coating porosity change, and drug partitioning between solid and aqueous phases. The model is used to describe in vitro sirolimus release from PLGA stent coating, and demonstrates the significance of simultaneous sirolimus release via diffusion through both polymer solid and pore space. The proposed model is compared to existing drug transport models, and the impact of model parameters, limitations and possible extensions of the model are also discussed. PMID:25345656

  11. Novel high-throughput polymer biocompatibility screening designed for SAR (structure-activity relationship): application for evaluating polymer coatings for cardiovascular drug-eluting stents.

    PubMed

    Hezi-Yamit, Ayala; Sullivan, Carol; Wong, Jennifer; David, Laura; Chen, Mingfei; Cheng, Peiwen; Shumaker, David; Wilcox, Josiah; Udipi, Kishore

    2009-08-01

    The development of stents has been a major advancement over balloon angioplasty, improving vessel revascularization in obstructive coronary artery disease. The development of drug-eluting stents (DES) was the next breakthrough, designed to prevent the development of neointimal hyperplasia (restenosis) following percutaneous coronary interventions (PCI). Several DES are currently in various stages of clinical development; these DES use different stent platforms, different antiproliferative drugs and different polymeric coatings that carry the drugs and control their delivery kinetics. Following DES implantation, when the entire drug is released, the polymeric coating is still retained on the stent and can influence subsequent tissue response and vascular healing. Therefore, the biocompatibility of the polymeric coatings is an important component of DES safety and needs to be thoroughly evaluated. Here we describe the development of a high-throughput screening platform for the evaluation of polymer biocompatibility, assaying whether a polymeric coating triggers inflammation in vascular cells. The data generated by these assays provides a structure-activity relationship (SAR) that can guide polymer chemists in polymer design. We have also applied this methodology to evaluate the components of a novel polymer system (BioLinx polymer system) designed in-house. In addition, we assayed other polymeric coatings similar to those currently used on various DES. The results of this evaluation reveal a remarkable correlation between polymer hydrophobicity and its ability to provoke inflammatory response.

  12. Release mechanism utilizing shape memory polymer material

    DOEpatents

    Lee, Abraham P.; Northrup, M. Allen; Ciarlo, Dino R.; Krulevitch, Peter A.; Benett, William J.

    2000-01-01

    Microfabricated therapeutic actuators are fabricated using a shape memory polymer (SMP), a polyurethane-based material that undergoes a phase transformation at a specified temperature (Tg). At a temperature above temperature Tg material is soft and can be easily reshaped into another configuration. As the temperature is lowered below temperature Tg the new shape is fixed and locked in as long as the material stays below temperature Tg. Upon reheating the material to a temperature above Tg, the material will return to its original shape. By the use of such SMP material, SMP microtubing can be used as a release actuator for the delivery of embolic coils through catheters into aneurysms, for example. The microtubing can be manufactured in various sizes and the phase change temperature Tg is determinate for an intended temperature target and intended use.

  13. Antirestenotic effects of a novel polymer-coated d-24851 eluting stent. Experimental data in a rabbit iliac artery model.

    PubMed

    Lysitsas, Dimitrios N; Katsouras, Christos S; Papakostas, John C; Toumpoulis, Ioannis K; Angelidis, Charalampos; Bozidis, Petros; Thomas, Christopher G; Seferiadis, Konstantin; Psychoyios, Nikolaos; Frillingos, Stathis; Pavlidis, Nikolaos; Marinos, Euaggelos; Khaldi, Lubna; Sideris, Dimitris A; Michalis, Lampros K

    2007-01-01

    Experimental and clinical data suggest that stents eluting antiproliferative agents can be used for the prevention of in-stent restenosis. Here we investigate in vitro the antiproliferative and apoptotic effect of D-24851 and evaluate the safety and efficacy of D-24851-eluting polymer-coated stents in a rabbit restenosis model (n = 53). Uncoated stents (n = 6), poly (DL: -lactide-co-glycolide) (PLGA)-coated stents (n = 7), and PLGA-coated stents loaded with 0.08 +/- 0.0025 microM (31 +/- 1 mug; low dose; n = 7), 0.55 +/- 0.02 microM (216 +/- 8 mug; high dose; n = 6), and 4.55 +/- 0.1 microM (1774 +/- 39 mug; extreme dose; n = 5) of D-24851 were randomly implanted in New Zealand rabbit right iliac arteries and the animals were sacrificed after 28 days for histomorphometric analysis. For the assessment of endothelial regrowth in 90 days, 12 rabbits were subjected to PLGA-coated (n = 3), low-dose (n = 3), high-dose (n = 3), and extreme-dose (n = 3) stent implantation. In vitro studies revealed that D-24851 exerts its growth inhibitory effects via inhibition of proliferation and induction of apoptosis without increasing the expression of heat shock protein-70, a cytoprotective and antiapoptotic protein. Treatment with low-dose D-24851 stents was associated with a significant reduction in neointimal area and percentage stenosis only compared with bare metal stents (38% [P = 0.029] and 35% [P = 0.003] reduction, respectively). Suboptimal healing, however, was observed in all groups of D-24851-loaded stents in 90 days in comparison with PLGA-coated stents. We conclude that low-dose D-24851-eluting polymer-coated stents significantly inhibit neointimal hyperplasia at 28 days through inhibition of proliferation and enhancement of apoptosis. In view of the suboptimal re-endothelialization, longer-term studies are needed in order to establish whether the inhibition of intimal growth is maintained.

  14. Antirestenotic Effects of a Novel Polymer-Coated D-24851 Eluting Stent. Experimental Data in a Rabbit Iliac Artery Model

    SciTech Connect

    Lysitsas, Dimitrios N.; Katsouras, Christos S.; Papakostas, John C.; Toumpoulis, Ioannis K.; Angelidis, Charalampos; Bozidis, Petros; Thomas, Christopher G.; Seferiadis, Konstantin; Psychoyios, Nikolaos; Frillingos, Stathis; Pavlidis, Nikolaos; Marinos, Euaggelos; Khaldi, Lubna; Sideris, Dimitris A.; Michalis, Lampros K.

    2007-11-15

    Experimental and clinical data suggest that stents eluting antiproliferative agents can be used for the prevention of in-stent restenosis. Here we investigate in vitro the antiproliferative and apoptotic effect of D-24851 and evaluate the safety and efficacy of D-24851-eluting polymer-coated stents in a rabbit restenosis model (n = 53). Uncoated stents (n = 6), poly (dl-lactide-co-glycolide) (PLGA)-coated stents (n = 7), and PLGA-coated stents loaded with 0.08 {+-} 0.0025 {mu}M (31 {+-} 1 {mu}g; low dose; n = 7), 0.55 {+-} 0.02 {mu}M (216 {+-} 8 {mu}g; high dose; n = 6), and 4.55 {+-} 0.1 {mu}M (1774 {+-} 39 {mu}g; extreme dose; n = 5) of D-24851 were randomly implanted in New Zealand rabbit right iliac arteries and the animals were sacrificed after 28 days for histomorphometric analysis. For the assessment of endothelial regrowth in 90 days, 12 rabbits were subjected to PLGA-coated (n = 3), low-dose (n = 3), high-dose (n = 3), and extreme-dose (n = 3) stent implantation. In vitro studies revealed that D-24851 exerts its growth inhibitory effects via inhibition of proliferation and induction of apoptosis without increasing the expression of heat shock protein-70, a cytoprotective and antiapoptotic protein. Treatment with low-dose D-24851 stents was associated with a significant reduction in neointimal area and percentage stenosis only compared with bare metal stents (38% [P = 0.029] and 35% [P = 0.003] reduction, respectively). Suboptimal healing, however, was observed in all groups of D-24851-loaded stents in 90 days in comparison with PLGA-coated stents. We conclude that low-dose D-24851-eluting polymer-coated stents significantly inhibit neointimal hyperplasia at 28 days through inhibition of proliferation and enhancement of apoptosis. In view of the suboptimal re-endothelialization, longer-term studies are needed in order to establish whether the inhibition of intimal growth is maintained.

  15. Photopolymerized Thiol-Ene Systems as Shape Memory Polymers.

    PubMed

    Nair, Devatha P; Cramer, Neil B; Scott, Timothy F; Bowman, Christopher N; Shandas, Robin

    2010-09-03

    In this study we introduce the use of thiol-ene photopolymers as shape memory polymer systems. The thiol-ene polymer networks are compared to a commonly utilized acrylic shape memory polymer and shown to have significantly improved properties for two different thiol-ene based polymer formulations. Using thermomechanical and mechanical analysis, we demonstrate that thiol-ene based shape memory polymer systems have comparable thermomechanical properties while also exhibiting a number of advantageous properties due to the thiol-ene polymerization mechanism which results in the formation of a homogenous polymer network with low shrinkage stress and negligible oxygen inhibition. The resulting thiol-ene shape memory polymer systems are tough and flexible as compared to the acrylic counterparts. The polymers evaluated in this study were engineered to have a glass transition temperature between 30 and 40 °C, exhibited free strain recovery of greater than 96% and constrained stress recovery of 100%. The thiol-ene polymers exhibited excellent shape fixity and a rapid and distinct shape memory actuation response.

  16. Comparison of Durable-Polymer Zotarolimus-Eluting and Biodegradable-Polymer Biolimus-Eluting Coronary Stents in Patients With Coronary Artery Disease: 3-Year Clinical Outcomes in the Randomized SORT OUT VI Trial.

    PubMed

    Raungaard, Bent; Christiansen, Evald H; Bøtker, Hans Erik; Hansen, Henrik S; Ravkilde, Jan; Thuesen, Leif; Aarøe, Jens; Villadsen, Anton B; Terkelsen, Christian J; Krusell, Lars R; Maeng, Michael; Kristensen, Steen D; Veien, Karsten T; Hansen, Knud N; Junker, Anders; Madsen, Morten; Andersen, Søren L; Jensen, Svend E; Jensen, Lisette O

    2017-02-13

    The authors sought to compare the safety and efficacy of the biocompatible durable-polymer zotarolimus-eluting stent with the biodegradable-polymer biolimus-eluting stent in unselected coronary patients. Biodegradable-polymer biolimus-eluting stents are superior to first-generation durable-polymer drug-eluting stents in long-term randomized all-comer trials. Long-term data comparing them to second-generation durable-polymer drug-eluting stents are lacking. The study was a randomized, multicenter, all-comer, noninferiority trial in patients with chronic stable coronary artery disease or acute coronary syndromes and at least 1 coronary artery lesion requiring treatment with a drug-eluting stent. Endpoints included major adverse cardiac events (MACE), a composite of safety (cardiac death and myocardial infarction not clearly attributable to a non-target lesion) and efficacy (target lesion revascularization); the individual endpoints of MACE; all-cause mortality; any myocardial infarction; target vessel revascularization; and definite or probable stent thrombosis at 36 months. From March 2011 to August 2012, 2,999 patients were randomly assigned (1:1) to receive either the zotarolimus-eluting (1,502 patients) or the biolimus-eluting (1,497 patients) stent. At 3-year follow-up, MACE occurred in 128 (8.6%) patients assigned to the durable-polymer zotarolimus-eluting stent and in 144 (9.6%) assigned to the biodegradable-polymer biolimus-eluting stent (p = 0.36). Occurrence of cardiac death (2.7% vs. 3.4%), myocardial infarction not clearly attributable to a non-target lesion (2.7% vs. 2.5%), and target lesion revascularization (5.4% vs. 5.5%) did not differ significantly between the 2 groups. Definite very late stent thrombosis occurred in 6 (0.4%) patients assigned to the durable-polymer zotarolimus-eluting stent and in 10 (0.7%) assigned to the biodegradable-polymer biolimus-eluting stent (p = 0.33). At 3-year follow-up, the durable-polymer zotarolimus-eluting stent

  17. A Randomized Comparison of Biodegradable Polymer- and Permanent Polymer-coated Platinum Chromium Everolimus-ElutingCoronary Stents in China: The EVOLVE China Study.

    PubMed

    Han, YaLing; Liu, Haiwei; Yang, Yuejin; Zhang, Jian; Xu, Kai; Fu, Guosheng; Su, Xi; Jiang, Tiemin; Pang, Wenyue; Chen, Jiyan; Yuan, Zuyi; Li, Hui; Wang, Haichang; Hong, Tao; Liu, Huiliang; Sun, Fucheng; Allocco, Dominic J; Zhang, Mingdong; Dawkins, Keith D

    2017-07-25

    The EVOLVE China randomized study sought to evaluate clinical safety and effectiveness of the SYNERGY bioabsorbable polymer-coated everolimus-eluting stent (EES) for the treatment of patients with coronary heart disease in China. Eligible patients with de novo native coronary artery lesions were randomized (1:1) to receive the SYNERGY or PROMUS Element Plus (PE Plus) stents. The primary endpoint was in-stent late loss at 9 months. Secondary endpoints included death, MI, revascularization, and stent thrombosis through 12 months. A total of 412 subjects were randomized (205 SYNERGY; 207 PE Plus) at 14sites in China from October 2013 to July 2014. SYNERGY was non-inferior to PE Plus for the primary endpoint of 9-month in stent late loss: SYNERGY 0.20mm±0.33mm vs PE Plus 0.17mm± 0.38mm with an upper 1-sided 97.5% confidence interval of the difference (0.10 mm)significantly less than the non-inferiority margin (0.15mm;P<0.0008). Clinical adverse event rates were low and not significantly different between groups at 9 and 12 months (all P>0.05). In the EVOLVE China trial, the SYNERGY bioabsorbable polymer-coated EES was non-inferior to the PE Plus permanent polymer-coated EES for the primary endpoint of late loss at 9 months.

  18. Functional comparison between BuMA Supreme biodegradable polymer sirolimus-eluting and durable polymer zotarolimus-eluting coronary stents using Quantitative Flow Ratio: PIONEER QFR substudy.

    PubMed

    Asano, Taku; Katagiri, Yuki; Collet, Carlos; Tenekecioglu, Erhan; Miyazaki, Yosuke; Sotomi, Yohei; Amoroso, Giovanni; Aminian, Adel; Brugaletta, Salvatore; Vrolix, Mathias; Hernandez-Antolín, Rosana; van de Harst, Pim; Iñiguez, Andres; Janssens, Luc; Smits, Pieter; Wykrzykowska, Joanna J; Ribeiro, Vasco Gama; Periera, Helder; da Silva, Pedro Canas; Piek, Jan J; Reiber, Johan H C; von Birgelen, Clemens; Sabaté, Manel; Onuma, Yoshinobu; Serruys, Patrick W

    2017-10-10

    Quantitative Flow Ratio (QFR) based on 3-dimensional quantitative coronary angiography (3D-QCA) is a novel method to assess the physiological functionality after treatment with stents. The current study aimed to evaluate the difference in physiological functionality 9 months after implantation of a bioresorbable polymer-based sirolimus-eluting stent with an electrografting base layer (BuMA Supreme: B-SES) versus a durable polymer-based zotarolimus-eluting stent (Resolute: R-ZES). The current post-hoc analysis was performed in the PIONEER randomized trial (1:1 randomization to B-SES [83 patients/95 lesions] and R-ZES [87 patients/101 lesions]). QFR was measured in stented vessels in both arms at pre-procedural, post-procedural and 9-month angiography without pharmacologically induced hyperemia (contrast QFR). At 9 months, both the values of QFR distal to the stent (B-SES: 0.89±0.10 vs. 0.89±0.11, p=0.97) and the numbers of the vessels with QFR ≤0.8 were not significantly different between the two groups (11.0% vs. 12.8%, p=0.72), while the in-stent binary restenosis rate was also comparable (3.7% versus 3.5%, P=1.00). QFR gradient across the device (∆QFR) at 9 months was also similar between both groups (B-SES: 0.03±0.04 vs. 0.03±0.07, p=0.95). Quantitative flow assessment 9 months after stenting did not differ between B-SES and R-ZES, despite of a significant difference in in-stent late lumen loss.

  19. Stent thrombosis in patients with coronary artery disease treated with biodegradable polymer drug-eluting stents: an update meta-analysis.

    PubMed

    Zhang, Jing

    2014-01-01

    Delayed re-endothelialization may be the pathophysiological cause of stent thrombosis (ST). Biodegradable polymer drug-eluting stents (BP-DES) may reduce the risk of ST. The aim of this study was to evaluate the risk of ST in patients treated with BP-DES. Studies were retrieved from the PubMed, Cochrane Library, and EMBASE online databases. Twelve studies (15,155 patients) with long-term follow-up (≥ 12 months) were included. Compared with durable polymer drug-eluting stents (DP-DES), BP-DES did not significantly decrease the risk of definite and probable ST (RR, 0.89; 95% CI, 0.68 to 1.18; P = 0.425) and definite ST (RR, 0.92; 95% CI, 0.66 to 1.30; P = 0.648). Furthermore, there was no difference in the risk of late ST (RR, 1.17; 95% CI, 0.39 to 3.53; P = 0.780). However, the rate of early ST was slightly higher in the BP-DES group (RR, 1.60; 95% CI, 0.94 to 2.73; P = 0.084) than in the DP-DES group. A significant reduction in very late ST (> 12 months) was evident with the BP-DES group (RR, 0.27; 95% CI, 0.10 to 0.68; P = 0.006). Subgroup analysis showed that there was no difference in the rate of definite and probable ST between the BP-DES and first- or second-generation DES groups.Biodegradable polymer stents were associated with a significantly lower risk of very late ST. However, there was no difference in the risk of definite and probable ST between the two groups.

  20. Surface characterization of polymer-drug modified vascular stents and intraocular lenses

    NASA Astrophysics Data System (ADS)

    Elachchabi, Amin

    Two of the most important medical devices in clinical use today are endoluminal stents and intraocular lenses (IOLs). In both devices, surface and interfacial properties are of basic importance in the development and clinical performance of these devices. Drug eluting stents have revolutionized the world of interventional cardiology. Research reported here was devoted to the design and development of new drug eluting stents wherein the metallic backbone is completely embedded in a polymeric matrix used also as a drug reservoir. This design, using silicone-drug compositions can lead to higher drug payloads, less tissue damage during angioplasty balloon/stent expansion, and the novel capability of delivering multiple drugs. The adhesion of the polymeric coating to the metallic stent is essential and has not been adequately reported previously. The adhesion of polydimethylsiloxane (PDMS) coatings to a stainless steel stent substrate was shown to be enhanced by the application of mixtures of tetra-n-propyl silicate, tetrabutyltitanate, tetra-2-methoxyethoxysilane, and 3-(trimethoxysilyl)propyl methacrylate coupling agents. Additionally, the effect of drug loading on the stress/strain properties of the polymeric coating is of basic importance. The tensile strength and percent elongation of dexamethasone loaded PDMS films was shown to remain satisfactory for stent coatings at low concentrations (less than 1%) but decreased as the concentrations of dexamethasone in PDMS was increased to 5%. The release of multiple therapeutic agents from PDMS coatings to reduce in-stent restenosis has not been previously reported. The release profile of Paclitaxel, dexamethasone 21-acetate, and their combination from PDMS coatings was studied using high precision liquid chromatography (HPLC). Although dexamethasone release was reduced by paclitaxel, paclitaxel release was unaffected by combination with dexamethasone. Paclitaxel release from the polymeric matrices was shown to inhibit

  1. Polymer-based resistive memory materials and devices.

    PubMed

    Lin, Wen-Peng; Liu, Shu-Juan; Gong, Tao; Zhao, Qiang; Huang, Wei

    2014-01-01

    Due to the advantages of good scalability, flexibility, low cost, ease of processing, 3D-stacking capability, and large capacity for data storage, polymer-based resistive memories have been a promising alternative or supplementary devices to conventional inorganic semiconductor-based memory technology, and attracted significant scientific interest as a new and promising research field. In this review, we first introduced the general characteristics of the device structures and fabrication, memory effects, switching mechanisms, and effects of electrodes on memory properties associated with polymer-based resistive memory devices. Subsequently, the research progress concerning the use of single polymers or polymer composites as active materials for resistive memory devices has been summarized and discussed. In particular, we consider a rational approach to their design and discuss how to realize the excellent memory devices and understand the memory mechanisms. Finally, the current challenges and several possible future research directions in this field have also been discussed. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Improved safety and reduction in stent thrombosis associated with biodegradable polymer-based biolimus-eluting stents versus durable polymer-based sirolimus-eluting stents in patients with coronary artery disease: final 5-year report of the LEADERS (Limus Eluted From A Durable Versus ERodable Stent Coating) randomized, noninferiority trial.

    PubMed

    Serruys, Patrick W; Farooq, Vasim; Kalesan, Bindu; de Vries, Ton; Buszman, Pawel; Linke, Axel; Ischinger, Thomas; Klauss, Volker; Eberli, Franz; Wijns, William; Morice, Marie Claude; Di Mario, Carlo; Corti, Roberto; Antoni, Diethmar; Sohn, Hae Y; Eerdmans, Pedro; Rademaker-Havinga, Tessa; van Es, Gerrit-Anne; Meier, Bernhard; Jüni, Peter; Windecker, Stephan

    2013-08-01

    This study sought to report the final 5 years follow-up of the landmark LEADERS (Limus Eluted From A Durable Versus ERodable Stent Coating) trial. The LEADERS trial is the first randomized study to evaluate biodegradable polymer-based drug-eluting stents (DES) against durable polymer DES. The LEADERS trial was a 10-center, assessor-blind, noninferiority, "all-comers" trial (N = 1,707). All patients were centrally randomized to treatment with either biodegradable polymer biolimus-eluting stents (BES) (n = 857) or durable polymer sirolimus-eluting stents (SES) (n = 850). The primary endpoint was a composite of cardiac death, myocardial infarction (MI), or clinically indicated target vessel revascularization within 9 months. Secondary endpoints included extending the primary endpoint to 5 years and stent thrombosis (ST) (Academic Research Consortium definition). Analysis was by intention to treat. At 5 years, the BES was noninferior to SES for the primary endpoint (186 [22.3%] vs. 216 [26.1%], rate ratio [RR]: 0.83 [95% confidence interval (CI): 0.68 to 1.02], p for noninferiority <0.0001, p for superiority = 0.069). The BES was associated with a significant reduction in the more comprehensive patient-orientated composite endpoint of all-cause death, any MI, and all-cause revascularization (297 [35.1%] vs. 339 [40.4%], RR: 0.84 [95% CI: 0.71 to 0.98], p for superiority = 0.023). A significant reduction in very late definite ST from 1 to 5 years was evident with the BES (n = 5 [0.7%] vs. n = 19 [2.5%], RR: 0.26 [95% CI: 0.10 to 0.68], p = 0.003), corresponding to a significant reduction in ST-associated clinical events (primary endpoint) over the same time period (n = 3 of 749 vs. n = 14 of 738, RR: 0.20 [95% CI: 0.06 to 0.71], p = 0.005). The safety benefit of the biodegradable polymer BES, compared with the durable polymer SES, was related to a significant reduction in very late ST (>1 year) and associated composite clinical outcomes. (Limus Eluted From

  3. Hydrophilic surface modification of polymer vascular prostheses and metal endoluminal stents

    NASA Astrophysics Data System (ADS)

    Amery, Drew Powell

    1997-12-01

    Large diameter vascular replacements of GORE-TEXsp°ler or Dacronsp°ler are frequently used to replace damaged arteries. Poor long term patency of small diameter grafts, 6 millimeters or less, is attributed to platelet adhesion and the inability to regenerate a blood contacting surface of vascular endothelium. Metal endoluminal stents are vascular prostheses used to keep arterial lumens open following angioplasty. Complications for these implants include short term thrombogenicity and long term restenosis. This study was directed to the synthesis and characterization of more biocompatible surfaces for these devices. Gamma radiation induced-graft polymerization and radio frequency plasma activation was investigated to surface modify polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), expanded polytetrafluoroethylene (ePTFE), and 316 stainless steel. To mimic natural biocompatible tissue surfacesl a series of hydrophilic polymers were grafted onto PMMA, PET, and ePTFE. Hydrophilic graft polymers were derived from N-vinyl pyrrolidone (NVP), potassium sulfopropylacrylate (KSPA), and dimethylacrylamide, and were grafted copolymerized with several bioactive compounds in a two step modification process. Complex graft surfaces containing fibronectin (Fn), laminin (Lm), type IV collagen (IV), heparin sulfate (Hp), albumin (Alb), and a synthetic fibronectin like protein polymer (RGD) were prepared. For surface modification of endoluminal stents of 316 stainless and tantalum, a combination of RF plasma activation combined with gamma radiation induced grafting was studied. Plasma deposition of hydrophobic poly(hexane) primer layers with water plasma oxidation were examined for initial metal surface activation. Surfaces were characterized by gravimetric analysis, contact angle goniometry, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Auger depth proGling, optical microscopy (OM), and low voltage scanning electron

  4. Development of Multifunctional Shape Memory Polymer and Shape Memory Polymer Composites

    NASA Astrophysics Data System (ADS)

    Pulla, Sesha Spandana

    Shape memory polymers (SMPs) are an emerging class of active polymers that can be used on a wide range of reconfigurable structures and actuation devices. The present study comprehensively examines the unconstrained shape recovery abilities of an epoxy-based SMP. In doing so, epoxy based SMP is synthesized and thermo-mechanically characterized. Results show that the present SMP exhibits excellent shape recoveries under unconstraint conditions, for a range of fixing strains and temperatures. Additionally, the stress-strain behavior of the SMP is determined to be nonlinear, finite deformation at all regions. The strain energy based models have been used to capture the complicate stress-strain behavior and shape recovery process of the SMPs. Further SMP based composites are considered to obtain a smart material that is suitable for applications at both above and below the glass transition temperature of the polymer. A smart composite made of SMP and SMA would allow many design possibilities due to their controllable temperature-dependent mechanical properties. In this study, the shape memory composites (SMCs) are created by embedding SMA components (particles and fibers) into SMP matrices, which take advantage of the complementary properties of SMAs and SMPs. The SMA-particle and SMA-fiber reinforced SMP composites are designed through numerical simulations for different weight fractions of the SMA fillers were varied from 0-50%. Addition of SMA fillers significantly increased modulus across the temperature regimes while maintaining the large actuation strain. In addition to the simulations, SMA-Particle + SMP composites are synthesized and tested using DMA in compression. The obtained modulus results from the simulations for SMA-Particle + SMP composite is comparable with the experimentally determined results. However, since SMP matrix is not conductive these composites often require external stimuli such as external heaters which limit their applications. To

  5. Sutureless microvascular anastomosis assisted by an expandable shape-memory alloy stent.

    PubMed

    Saegusa, Noriko; Sarukawa, Shunji; Ohta, Kunihiro; Takamatsu, Kensuke; Watanabe, Mitsuhiro; Sugino, Takashi; Nakagawa, Masahiro; Akiyama, Yasuto; Kusuhara, Masatoshi; Kishi, Kazuo; Inoue, Keita

    2017-01-01

    Vascular anastomosis is the highlight of cardiovascular, transplant, and reconstructive surgery, which has long been performed by hand using a needle and suture. However, anastomotic thrombosis occurs in approximately 0.5-10% of cases, which can cause serious complications. To improve the surgical outcomes, attempts to develop devices for vascular anastomosis have been made, but they have had limitations in handling, cost, patency rate, and strength at the anastomotic site. Recently, indwelling metal stents have been greatly improved with precise laser metalwork through programming technology. In the present study, we designed a bare metal stent, Microstent, that was constructed by laser machining of a shape-memory alloy, NiTi. An end-to-end microvascular anastomosis was performed in SD rats by placing the Microstent at the anastomotic site and gluing the junction. The operation time for the anastomosis was significantly shortened using Microstent. Thrombus formation, patency rate, and blood vessel strength in the Microstent anastomosis were superior or comparable to hand-sewn anastomosis. The results demonstrated the safety and effectiveness, as well as the operability, of the new method, suggesting its great benefit for surgeons by simplifying the technique for microvascular anastomosis.

  6. AC Electric Field Activated Shape Memory Polymer Composite

    NASA Technical Reports Server (NTRS)

    Kang, Jin Ho; Siochi, Emilie J.; Penner, Ronald K.; Turner, Travis L.

    2011-01-01

    Shape memory materials have drawn interest for applications like intelligent medical devices, deployable space structures and morphing structures. Compared to other shape memory materials like shape memory alloys (SMAs) or shape memory ceramics (SMCs), shape memory polymers (SMPs) have high elastic deformation that is amenable to tailored of mechanical properties, have lower density, and are easily processed. However, SMPs have low recovery stress and long response times. A new shape memory thermosetting polymer nanocomposite (LaRC-SMPC) was synthesized with conductive fillers to enhance its thermo-mechanical characteristics. A new composition of shape memory thermosetting polymer nanocomposite (LaRC-SMPC) was synthesized with conductive functionalized graphene sheets (FGS) to enhance its thermo-mechanical characteristics. The elastic modulus of LaRC-SMPC is approximately 2.7 GPa at room temperature and 4.3 MPa above its glass transition temperature. Conductive FGSs-doped LaRC-SMPC exhibited higher conductivity compared to pristine LaRC SMP. Applying an electric field at between 0.1 Hz and 1 kHz induced faster heating to activate the LaRC-SMPC s shape memory effect relative to applying DC electric field or AC electric field at frequencies exceeding1 kHz.

  7. Shape memory polymer foams for endovascular therapies

    DOEpatents

    Wilson, Thomas S.; Maitland, Duncan J.

    2015-05-26

    A system for occluding a physical anomaly. One embodiment comprises a shape memory material body wherein the shape memory material body fits within the physical anomaly occluding the physical anomaly. The shape memory material body has a primary shape for occluding the physical anomaly and a secondary shape for being positioned in the physical anomaly.

  8. Shape memory polymer foams for endovascular therapies

    DOEpatents

    Wilson, Thomas S.; Maitland, Duncan J.

    2017-03-21

    A system for occluding a physical anomaly. One embodiment comprises a shape memory material body wherein the shape memory material body fits within the physical anomaly occluding the physical anomaly. The shape memory material body has a primary shape for occluding the physical anomaly and a secondary shape for being positioned in the physical anomaly.

  9. Shape memory polymer foams for endovascular therapies

    DOEpatents

    Wilson, Thomas S [Castro Valley, CA; Maitland, Duncan J [Pleasant Hill, CA

    2012-03-13

    A system for occluding a physical anomaly. One embodiment comprises a shape memory material body wherein the shape memory material body fits within the physical anomaly occluding the physical anomaly. The shape memory material body has a primary shape for occluding the physical anomaly and a secondary shape for being positioned in the physical anomaly.

  10. Biolimus-eluting stents with biodegradable polymer versus bare-metal stents in acute myocardial infarction: two-year clinical results of the COMFORTABLE AMI trial.

    PubMed

    Räber, Lorenz; Kelbæk, Henning; Taniwaki, Masanori; Ostojic, Miodrag; Heg, Dik; Baumbach, Andreas; von Birgelen, Clemens; Roffi, Marco; Tüller, David; Engstrøm, Thomas; Moschovitis, Aris; Pedrazzini, Giovanni; Wenaweser, Peter; Kornowski, Ran; Weber, Klaus; Lüscher, Thomas F; Matter, Christian M; Meier, Bernhard; Jüni, Peter; Windecker, Stephan

    2014-06-01

    This study sought to determine whether the 1-year differences in major adverse cardiac event between a stent eluting biolimus from a biodegradable polymer and bare-metal stents (BMSs) in the COMFORTABLE trial (Comparison of Biolimus Eluted From an Erodible Stent Coating With Bare Metal Stents in Acute ST-Elevation Myocardial Infarction) were sustained during long-term follow-up. A total of 1161 patients were randomly assigned to biolimus-eluting stent (BES) and BMS at 11 centers, and follow-up rates at 2 years were 96.3%. A subgroup of 103 patients underwent angiography at 13 months. At 2 years, differences in the primary end point of cardiac death, target-vessel myocardial infarction, and target lesion revascularization continued to diverge in favor of BES-treated patients (5.8%) compared with BMS-treated patients (11.9%; hazard ratio = 0.48; 95% confidence interval, 0.31-0.72; P < 0.001) with a significant risk reduction during the second year of follow-up (hazard ratio 1-2 years = 0.45; 95% confidence interval, 0.20-1.00; P = 0.049). Differences in the primary end point were driven by a reduction in target lesion revascularization (3.1% versus 8.2%; P < 0.001) and target-vessel reinfarction (1.3% versus 3.4%; P = 0.023). The composite of death, any reinfarction and revascularization (14.5% versus 19.3%; P = 0.03), and cardiac death or target-vessel myocardial infarction (4.2% versus 7.2%; P = 0.036) were less frequent among BES-treated patients compared with BMS-treated patients. The 13-month angiographic in-stent percent diameter stenosis amounted to 12.0 ± 7.2 in BES- and 39.6 ± 25.2 in BMS-treated lesions (P < 0.001). Among patients with ST-segment-elevation myocardial infarction undergoing primary percutaneous coronary intervention, BES continued to improve cardiovascular events compared with BMS beyond 1 year. http://www.clinicaltrials.gov. Unique identifier: NTC00962416. © 2014 American Heart Association, Inc.

  11. First-in-man randomized comparison of BuMA Supreme biodegradable polymer sirolimus-eluting versus durable polymer zotarolimus-eluting coronary stents: The PIONEER trial.

    PubMed

    von Birgelen, Clemens; Asano, Taku; Amoroso, Giovanni; Aminian, Adel; Brugaletta, Salvatore; Vrolix, Mathias; Hernandez-Antolín, Rosana; van de Harst, Pim; Iñiguez, Andres; Janssens, Luc; Smits, Pieter C; Wykrzykowska, Joanna J; Ribeiro, Vasco Gama; Periera, Helder; Canas da Silva, Pedro; Piek, Jan J; Onuma, Yoshinobu; Serruys, Patrick W; Sabaté, Manel

    2017-09-19

    A second iteration of a sirolimus-eluting stent (SES) that has a biodegradable PLGA-polymer coating with electrografting base layer on a thin-strut (80µm) cobalt-chromium platform (BuMA Supreme; SINOMED, Tianjin, China) has been developed. This first-in-man trial assessed the efficacy and safety of the novel device. This randomized, multi-center, single-blinded, non-inferiority trial compared BuMA Supreme SES versus contemporary durable polymer zotarolimus-eluting stents (ZES) in terms of angiographic in-stent late lumen loss (LLL) at 9-months follow-up as the primary endpoint. A total of 170 patients were randomly allocated to treatment with SES (n=83) or ZES (n=87). At 9-month angiographic follow-up, in-stent LLL was 0.29±0.33mm in SES and 0.14±0.37mm in ZES (Pnon-inferiority=0.45). The in-stent percent diameter stenosis and the binary restenosis rate of the two treatment arms were similar (19.2±12.0% vs. 16.1±12.6%, p=0.09, and 3.3% vs. 4.4%, P=1.00, respectively). At 12-month clinical follow-up, there was no difference between treatment arms with regard to a device-oriented composite clinical endpoint (4.9% vs. 5.7%; p=0.72). The PIONEER trial did not meet its primary endpoint in terms of in-stent LLL at 9-month follow-up. However, this result did not translate into any increase in restenosis rate or impairment in 12-month clinical outcomes.

  12. Randomized evaluation of two drug-eluting stents with identical metallic platform and biodegradable polymer but different agents (paclitaxel or sirolimus) compared against bare stents: 1-year results of the PAINT trial.

    PubMed

    Lemos, Pedro A; Moulin, Bruno; Perin, Marco A; Oliveira, Ludmilla A R R; Arruda, J Airton; Lima, Valter C; Lima, Antonio A G; Caramori, Paulo R A; Medeiros, Cesar R; Barbosa, Mauricio R; Brito, Fabio S; Ribeiro, Expedito E; Martinez, Eulógio E

    2009-11-01

    We tested two novel drug-eluting stents (DES), covered with a biodegradable-polymer carrier and releasing paclitaxel or sirolimus, which were compared against a bare metal stent (primary objective). The DES differed by the drug, but were identical otherwise, allowing to compare the anti-restenosis effects of sirolimus versus paclitaxel (secondary objective). The efficacy of novel DES with biodegradable polymers should be tested in the context of randomized trials, even when using drugs known to be effective, such as sirolimus and paclitaxel. Overall, 274 patients with de novo coronary lesions in native vessels scheduled for stent implantation were randomly assigned (2:2:1 ratio) for the paclitaxel (n = 111), sirolimus (n = 106), or bare metal stent (n = 57) groups. Angiographic follow-up was obtained at 9 months and major cardiac adverse events up to 12 months. Both paclitaxel and sirolimus stents reduced the 9-month in-stent late loss (0.54-0.44 mm, 0.32-0.43 mm, vs. 0.90-0.45 mm respectively), and 1-year risk of target vessel revascularization and combined major adverse cardiac events (P < 0.05 for both, in all comparisons), compared with controls. Sirolimus stents had lower late loss than paclitaxel stents (P < 0.01), but similar 1-year clinical outcomes. There were no differences in the risk of death, infarction, or stent thrombosis among the study groups. Both novel DES were effective in reducing neointimal hyperplasia and 1-year re-intervention, compared to bare metal stents. Our findings also suggest that sirolimus is more effective than paclitaxel in reducing angiographic neointima, although this effect was not associated with better clinical outcomes. Copyright 2009 Wiley-Liss, Inc.

  13. Combined, Independent Small Molecule Release and Shape Memory via Nanogel-Coated Thiourethane Polymer Networks

    PubMed Central

    Dailing, Eric A.; Nair, Devatha P.; Setterberg, Whitney K.; Kyburz, Kyle A.; Yang, Chun; D’Ovidio, Tyler; Anseth, Kristi S.; Stansbury, Jeffrey W.

    2015-01-01

    Drug releasing shape memory polymers (SMPs) were prepared from poly(thiourethane) networks that were coated with drug loaded nanogels through a UV initiated, surface mediated crosslinking reaction. Multifunctional thiol and isocyanate monomers were crosslinked through a step-growth mechanism to produce polymers with a homogeneous network structure that exhibited a sharp glass transition with 97% strain recovery and 96% shape fixity. Incorporating a small stoichiometric excess of thiol groups left pendant functionality for a surface coating reaction. Nanogels with diameter of approximately 10 nm bearing allyl and methacrylate groups were prepared separately via solution free radical polymerization. Coatings with thickness of 10–30 μm were formed via dip-coating and subsequent UV-initiated thiol-ene crosslinking between the SMP surface and the nanogel, and through inter-nanogel methacrylate homopolymerization. No significant change in mechanical properties or shape memory behavior was observed after the coating process, indicating that functional coatings can be integrated into an SMP without altering its original performance. Drug bioactivity was confirmed via in vitro culturing of human mesenchymal stem cells with SMPs coated with dexamethasone-loaded nanogels. This article offers a new strategy to independently tune multiple functions on a single polymeric device, and has broad application toward implantable, minimally invasive medical devices such as vascular stents and ocular shunts, where local drug release can greatly prolong device function. PMID:27066114

  14. Angioscopy study from a large patient population comparing sirolimus-eluting stent with biodegradable versus durable polymer.

    PubMed

    Chen, Shao-Liang; Xu, Tian; Zhang, Jun-Jie; Ye, Fei; Hu, Zuo-Ying; Tian, Nai-Liang; Zhang, Yao-Jun; Kotani, Junichi; Zhang, Jun-Xia

    2012-09-01

    This study aimed to compare the neointimal coverage (NIC), subclinical thrombus, color of plaque underneath the stent at 9-month after implantation of sirolimus-eluting stent (SES) either with durable or with biodegradable polymer (BDPM). A total of 175 patients were assigned as Cypher (n = 81, 97 stents with durable polymer) and Excel (n = 94, 112 stents with BDPM) stent at 9-month after indexed procedure. NIC was classified from grade 0-3. Color of plaque was divided into white, light-yellow, yellow, and dark yellow. Thrombus was diagnosed as white or red material with cotton-like or ragged appearance. Incomplete NIC (grade 0/1) circled by a blush was termed by "inflaming." There were significant differences in unstable angina (90.5 vs. 52.4%, P = 0.015), previous myocardial infarction (33.3 vs. 4.0%, P = 0.045) and left ventricular eject fraction (55.2 ± 7.8 vs. 62.6 ± 6.3%, P = 0.021) between the Excel and Cypher groups. The minimal- and maximal-NIC grades in the Cypher group were 0.67 ± 0.58 and 2.29 ± 0.46, respectively, when compared with 1.45 ± 0.67 (P < 0.001) and 2.64 ± 0.49 (P = 0.023) in the Excel group. The percentage of yellow plaque, thrombus, "inflaming" and NIC grade of 0 in the Excel and Cypher groups, respectively, were as follows: 8.0 vs. 26.8% (P = 0.031), 9.8 vs. 32.9% (P = 0.024), 8.0 vs. 38.1% (P = 0.017), and 38.1 vs. 0% (P < 0.001). Of the stents with "inflaming," 63.6% had thrombus when compared with 20.1% of the non-erosion stents (P < 0.001). Overlapping segments had the lowest NIC grades and more "inflaming" demonstrating a significant difference between Cypher vs. Excel stents. NIC grade was positively correlated with thrombus. SES with BDPM has improved NIC resulting in less yellow plaque, thrombus, and "inflaming." Overlapping segments had the lowest NIC grade and more "inflaming." Copyright © 2011 Wiley Periodicals, Inc.

  15. Controlled architecture for improved macromolecular memory within polymer networks.

    PubMed

    DiPasquale, Stephen A; Byrne, Mark E

    2016-08-01

    This brief review analyzes recent developments in the field of living/controlled polymerization and the potential of this technique for creating imprinted polymers with highly structured architecture with macromolecular memory. As a result, it is possible to engineer polymers at the molecular level with increased homogeneity relating to enhanced template binding and transport. Only recently has living/controlled polymerization been exploited to decrease heterogeneity and substantially improve the efficiency of the imprinting process for both highly and weakly crosslinked imprinted polymers. Living polymerization can be utilized to create imprinted networks that are vastly more efficient than similar polymers produced using conventional free radical polymerization, and these improvements increase the role that macromolecular memory can play in the design and engineering of new drug delivery and sensing platforms.

  16. Polymer-free sirolimus-eluting stents in a large-scale all-comers population

    PubMed Central

    Krackhardt, Florian; Kočka, Viktor; Waliszewski, Matthias W.; Utech, Andreas; Lustermann, Meik; Hudec, Martin; Studenčan, Martin; Schwefer, Markus; Yu, Jiangtao; Jeong, Myung Ho; Ahn, Taehoon; Wan Ahmad, Wan Azman; Boxberger, Michael; Schneider, André; Leschke, Matthias

    2017-01-01

    Objective The objective of this study was to assess the safety and efficacy of a polymer-free sirolimus coated, ultrathin strut drug-eluting stent (PF-SES) in an unselected patient population with a focus on acute coronary syndrome (ACS). Furthermore, stable coronary artery disease (CAD) with short (≤6 months) versus long (>6 months) dual antiplatelet therapy (DAPT) were also studied. Methods Patients who received PF-SES were investigated in an unselected large-scale international, single-armed, multicenter, ‘all comers’ observational study. The primary endpoint was the 9-month target lesion revascularisation (TLR) rate, whereas secondary endpoints included the 9-month major adverse cardiac events (MACE) and procedural success rates. A priori defined subgroups such as patients with ACS, diabetes, lesion subsets and procedural characteristics relative to DAPT were investigated. Results A total of 2877 patients of whom 1084 had ACS were treated with PF-SES (1.31±0.75 stents per patient). At 9 months, the accumulated overall TLR rate was 2.3% (58/2513). There was no significant difference between ACS and stable CAD (2.6% vs 2.1%, p=0.389). However, the overall MACE rate was 4.3% (108/2513) with a higher rate in patients with ACS when compared with the stable CAD subgroup (6.1%, 58/947 vs 3.2%, 50/1566, p<0.001). Conclusions PF-SES angioplasty is safe and effective in the daily clinical routine with low rates of TLR and MACE in an unselected patient population. Our data are in agreement with prior clinical findings that extended DAPT duration beyond 6 months do not improve clinical outcomes in patients with stable CAD (ClinicalTrials.gov Identifier NCT02629575). Trial registration number NCT02629575. PMID:28761678

  17. Polymer-free sirolimus-eluting stents in a large-scale all-comers population.

    PubMed

    Krackhardt, Florian; Kočka, Viktor; Waliszewski, Matthias W; Utech, Andreas; Lustermann, Meik; Hudec, Martin; Studenčan, Martin; Schwefer, Markus; Yu, Jiangtao; Jeong, Myung Ho; Ahn, Taehoon; Wan Ahmad, Wan Azman; Boxberger, Michael; Schneider, André; Leschke, Matthias

    2017-01-01

    The objective of this study was to assess the safety and efficacy of a polymer-free sirolimus coated, ultrathin strut drug-eluting stent (PF-SES) in an unselected patient population with a focus on acute coronary syndrome (ACS). Furthermore, stable coronary artery disease (CAD) with short (≤6 months) versus long (>6 months) dual antiplatelet therapy (DAPT) were also studied. Patients who received PF-SES were investigated in an unselected large-scale international, single-armed, multicenter, 'all comers' observational study. The primary endpoint was the 9-month target lesion revascularisation (TLR) rate, whereas secondary endpoints included the 9-month major adverse cardiac events (MACE) and procedural success rates. A priori defined subgroups such as patients with ACS, diabetes, lesion subsets and procedural characteristics relative to DAPT were investigated. A total of 2877 patients of whom 1084 had ACS were treated with PF-SES (1.31±0.75 stents per patient). At 9 months, the accumulated overall TLR rate was 2.3% (58/2513). There was no significant difference between ACS and stable CAD (2.6% vs 2.1%, p=0.389). However, the overall MACE rate was 4.3% (108/2513) with a higher rate in patients with ACS when compared with the stable CAD subgroup (6.1%, 58/947 vs 3.2%, 50/1566, p<0.001). PF-SES angioplasty is safe and effective in the daily clinical routine with low rates of TLR and MACE in an unselected patient population. Our data are in agreement with prior clinical findings that extended DAPT duration beyond 6 months do not improve clinical outcomes in patients with stable CAD (ClinicalTrials.gov Identifier NCT02629575). NCT02629575.

  18. Residual stresses in injection molded shape memory polymer parts

    NASA Astrophysics Data System (ADS)

    Katmer, Sukran; Esen, Huseyin; Karatas, Cetin

    2016-03-01

    Shape memory polymers (SMPs) are materials which have shape memory effect (SME). SME is a property which has the ability to change shape when induced by a stimulator such as temperature, moisture, pH, electric current, magnetic field, light, etc. A process, known as programming, is applied to SMP parts in order to alter them from their permanent shape to their temporary shape. In this study we investigated effects of injection molding and programming processes on residual stresses in molded thermoplastic polyurethane shape memory polymer, experimentally. The residual stresses were measured by layer removal method. The study shows that injection molding and programming process conditions have significantly influence on residual stresses in molded shape memory polyurethane parts.

  19. Shape-memory polymer foam device for treating aneurysms

    DOEpatents

    Ortega, Jason M.; Benett, William J.; Small, Ward; Wilson, Thomas S.; Maitland, Duncan J; Hartman, Jonathan

    2017-05-30

    A system for treating an aneurysm in a blood vessel or vein, wherein the aneurysm has a dome, an interior, and a neck. The system includes a shape memory polymer foam in the interior of the aneurysm between the dome and the neck. The shape memory polymer foam has pores that include a first multiplicity of pores having a first pore size and a second multiplicity of pores having a second pore size. The second pore size is larger than said first pore size. The first multiplicity of pores are located in the neck of the aneurysm. The second multiplicity of pores are located in the dome of the aneurysm.

  20. Tissue response to poly(L-lactic acid)-based blend with phospholipid polymer for biodegradable cardiovascular stents.

    PubMed

    Kim, Hyung Il; Ishihara, Kazuhiko; Lee, Seungbok; Seo, Ji-Hun; Kim, Hye Young; Suh, Dongwhan; Kim, Min Uk; Konno, Tomohiro; Takai, Madoka; Seo, Jeong-Sun

    2011-03-01

    A temporary cardiovascular stent device by bioabsorbable materials might reduce late stent thrombosis. A water-soluble amphiphilic phospholipid polymer bearing phosphorylcholine groups (PMB30W) was blended with a high-molecular-weight poly(l-lactic acid) (PLLA) to reduce unfavorable tissue responses at the surface. The PLLA implants and the polymer blend (PLLA/PMB30W) implants were inserted into subcutaneous tissues of rats, the infrarenal aorta of rats, and the internal carotid arteries of rabbits. After 6 months subcutaneous implantation, the PLLA/PMB30W maintained high density of phosphorylcholine groups on the surface without a significant bioabsorption. After intravascular implantation, the cross-sectional areas of polymer tubing with diameters less than 1.6 mm were histomorphometrically measured. Compared to the PLLA tubing, the PLLA/PMB30W tubing significantly reduced the thrombus formation during 30 d of implantation. Human peripheral blood mononuclear cells were cultured on the PLLA and the PLLA/PMB30W to compare inflammatory reactions. Enzyme-linked immunosorbent assay quantified substantially decreased proinflammatory cytokines in the case of the PLLA/PMB30W. They were almost the same level as the negative controls. Thus, we conclude that the phosphorylcholine groups could reduce tissue responses significantly both in vivo and in vitro, and the PLLA/PMB30W is a promising material for preparing temporary cardiovascular stent devices. Copyright © 2010 Elsevier Ltd. All rights reserved.

  1. Five-year clinical outcomes of a polymer-free sirolimus-eluting stent versus a permanent polymer paclitaxel-eluting stent: final results of the intracoronary stenting and angiographic restenosis - test equivalence between two drug-eluting stents (ISAR-TEST) trial.

    PubMed

    King, Lamin; Byrne, Robert A; Mehilli, Julinda; Schömig, Albert; Kastrati, Adnan; Pache, Jurgen

    2013-01-01

    Limited evidence exists regarding the long-term performance of polymer-free (PF) drug-eluting stents (DES) in comparison to permanent polymer DES. This study investigated the 5-year efficacy and safety of a PF sirolimus-eluting stent (PF-SES) versus a permanent polymer paclitaxel-eluting stent (PES) in the setting of the Intracoronary Stenting and Angiographic Restenosis-Test Equivalence Between Two Drug-Eluting Stents (ISAR-TEST) randomized trial. A total of 450 patients undergoing percutaneous coronary intervention were randomized to receive either PF-SES (Yukon, Translumina; n = 225) or PES (Taxus, Boston Scientific; n = 225). Clinical follow-up was performed to 5 years after enrollment. The endpoints were major adverse cardiac events (MACE), target lesion revascularization (TLR), the composite of death or any myocardial infarction (MI) and stent thrombosis (ST). The incidence of MACE at 5 years was 27.3% (57 patients) in the PF-SES group and 31.7% (65 patients) in the PES group [hazard ratio (HR) = 0.87 [95% confidence interval (95% CI) = 0.61-1.24]; P = 0.40]. The combined incidence of death or MI was 16.6% (34 patients) in the PF-SES group and 20.0% (39 patients) in the PES group (HR = 0.86 [95% CI = 0.54-1.36]; P = 0.52). The incidence of TLR was 16.5% (34 patients) in the PF-SES group and 16.4% (33 patients) in the PES group (HR = 1.03 [95% CI = 0.64-1.66]; P = 0.89). ST occurred in 0.5% (one patient) in the PF-SES group and 1.6% (three patients) in the PES group (HR = 0.33 [95% CI = 0.03-3.14]; P = 0.32). Overall there was no significant difference in clinical outcomes between PF-SES and PES to 5 years. Extended follow-up supports the durability of efficacy and safety of PF-SES. Copyright © 2012 Wiley Periodicals, Inc.

  2. Improving of Mechanical and Shape-Memory Properties in Hyperbranched Epoxy Shape-Memory Polymers

    NASA Astrophysics Data System (ADS)

    Santiago, David; Fabregat-Sanjuan, Albert; Ferrando, Francesc; De la Flor, Silvia

    2016-09-01

    A series of shape-memory epoxy polymers were synthesized using an aliphatic amine and two different commercial hyperbranched poly(ethyleneimine)s with different molecular weights as crosslinking agents. Thermal, mechanical, and shape-memory properties in materials modified with different hyperbranched polymers were analyzed and compared in order to establish the effect of the structure and the molecular weight of the hyperbranched polymers used. The presence of hyperbranched polymers led to more heterogeneous networks, and the crosslinking densities of which increase as the hyperbranched polymer content increases. The transition temperatures can be tailored from 56 to 117 °C depending on the molecular weight and content of the hyperbranched polymer. The mechanical properties showed excellent values in all formulations at room temperature and, specially, at T_{{g}}^{{E^' with stress at break as high as 15 MPa and strain at break as high as 60 %. The shape-memory performances revealed recovery ratios around 95 %, fixity ratios around 97 %, and shape-recovery velocities as high as 22 %/min. The results obtained in this study reveal that hyperbranched polymers with different molecular weights can be used to enhance the thermal and mechanical properties of epoxy-based SMPs while keeping excellent shape-memory properties.

  3. Acute Thrombogenicity of a Durable Polymer Everolimus-Eluting Stent Relative to Contemporary Drug-Eluting Stents With Biodegradable Polymer Coatings Assessed Ex Vivo in a Swine Shunt Model.

    PubMed

    Otsuka, Fumiyuki; Cheng, Qi; Yahagi, Kazuyuki; Acampado, Eduardo; Sheehy, Alexander; Yazdani, Saami K; Sakakura, Kenichi; Euller, Kristina; Perkins, Laura E L; Kolodgie, Frank D; Virmani, Renu; Joner, Michael

    2015-08-17

    This study sought to evaluate whether the permanent fluoropolymer-coated Xience Xpedition everolimus-eluting stent (Xience-EES) exhibits lower acute thrombogenicity compared with contemporary drug-eluting stents (DES) with biodegradable polymer coatings in an acute swine shunt model. Previous pre-clinical and clinical experience suggests that several factors may influence the predisposition for acute thrombus formation of polymer-coated DES, including stent design and the polymer coating technology. It remains unclear whether relevant differences exist with respect to acute thrombogenicity, particularly between current commercial stent designs using permanent polymers and those using biodegradable polymers. An ex vivo carotid to jugular arteriovenous porcine shunt model involving a test circuit of 3 in-line stents, was used to test acute thrombogenicity, where Xience-EES (n = 24) was compared with 4 CE-marked DES with biodegradable polymer coatings (BioMatrix Flex, Synergy, Nobori, and Orsiro [n = 6 each]). After 1 h of circulation, platelet aggregation in whole mount stents was evaluated by confocal microscopy with immunofluorescent staining against dual platelet markers (CD61/CD42b) along with scanning electron microscopy. Xience-EES showed the least percentage of thrombus-occupied area as compared with the biodegradable polymer-coated DES, with a significant difference compared with BioMatrix Flex and Synergy (mean differences: [BioMatrix Flex: 15.54, 95% confidence interval [CI]: 11.34 to 19.75, p < 0.001; Synergy: 8.64, 95% CI: 4.43 to 12.84, p < 0.001; Nobori: 4.22, 95% CI: -0.06 to 8.49, p = 0.055; Orsiro: 2.95, 95% CI: -1.26 to 7.15, p = 0.286). The number of cell nuclei on strut surfaces was also the least in Xience-EES, with a significant difference relative to BioMatrix Flex, Nobori, and Orsiro (mean ratios: BioMatrix Flex: 4.73, 95% CI: 2.46 to 9.08, p < 0.001; Synergy: 1.44, 95% CI: 0.75 to 2.76, p = 0.51; Nobori: 5.97, 95% CI: 3.11 to 11.44, p < 0

  4. Final 3-Year Outcome of a Randomized Trial Comparing Second-Generation Drug-Eluting Stents Using Either Biodegradable Polymer or Durable Polymer: NOBORI Biolimus-Eluting Versus XIENCE/PROMUS Everolimus-Eluting Stent Trial.

    PubMed

    Natsuaki, Masahiro; Kozuma, Ken; Morimoto, Takeshi; Kadota, Kazushige; Muramatsu, Toshiya; Nakagawa, Yoshihisa; Akasaka, Takashi; Igarashi, Keiichi; Tanabe, Kengo; Morino, Yoshihiro; Ishikawa, Tetsuya; Nishikawa, Hideo; Awata, Masaki; Abe, Mitsuru; Okada, Hisayuki; Takatsu, Yoshiki; Ogata, Nobuhiko; Kimura, Kazuo; Urasawa, Kazushi; Tarutani, Yasuhiro; Shiode, Nobuo; Kimura, Takeshi

    2015-10-01

    There is a paucity of data reporting the clinical outcomes of biodegradable polymer biolimus-eluting stent (BP-BES) compared with durable polymer everolimus-eluting stent (DP-EES) beyond 1 year after stent implantation when the polymer is fully degraded. The NOBORI Biolimus-Eluting Versus XIENCE/PROMUS Everolimus-Eluting Stent Trial (NEXT) is a prospective, multicenter, randomized, open-label, noninferiority trial comparing BP-BES with DP-EES in patients scheduled for percutaneous coronary intervention using drug-eluting stent (DES) without any exclusion criteria among 98 participating centers in Japan. The trial was designed to evaluate noninferiority of BP-BES relative to DP-EES in terms of any target-lesion revascularization at 1 year and death or myocardial infarction at 3 years. Between May and October 2011, 3235 patients were randomly assigned to receive either BP-BES (1617 patients) or DP-EES (1618 patients). Complete 3-year follow-up was achieved in 97.6% of patients. At 3 years, the primary safety end point of death or myocardial infarction occurred in 159 patients (9.9%) in the BP-BES group and in 166 patients (10.3%) in the DP-EES group, demonstrating noninferiority of BP-BES relative to DP-EES (P noninferiority<0.0001 and P superiority=0.7). Cumulative incidence of target-lesion revascularization was not significantly different between the 2 groups (7.4% versus 7.1%; P=0.8). By a landmark analysis at 1 year, the cumulative incidences of death or myocardial infarction and target-lesion revascularization were also not significantly different between the 2 groups (4.6% versus 5.2%; P=0.46 and 3.3% versus 2.7%; P=0.39, respectively). Safety and efficacy outcomes of BP-BES were non inferior to those of DP-EES 3 years after stent implantation. URL: http://www.clinicaltrials.gov. Unique identifier: NCT01303640. © 2015 American Heart Association, Inc.

  5. Three-Year Clinical Outcomes of a Polymer-Free Paclitaxel-Eluting Microporous Stent in Real-World Practice: Final Results of the Safety and Efficacy Registry of the Yinyi Stent (SERY-I)

    PubMed Central

    Zhu, Jinzhou; Zhang, Qi; Chen, Lianglong; Zhang, Chenyun; Zhou, Xuchen; Yuan, Yong; Zhang, Ruiyan

    2017-01-01

    Background The safety and efficacy of a China-made polymer-free paclitaxel-eluting microporous stent (Yinyi) at 1-year has been previously reported. However, limited evidence exists regarding the long-term performance of this novel drug-eluting stent (DES). This study investigated the 3-year efficacy and safety of the Yinyi stent in the setting of safety and efficacy registry of the Yinyi stent (SERY-I) clinical trial. Methods Between June 2008 and August 2009, a total of 1045 patients undergoing percutaneous coronary intervention (PCI) were implanted with ≥ 1 Yinyi stents at 27 medical centers in mainland China. Thereafter, clinical follow-up was performed for a period of 3 years after enrollment. The primary endpoint was the cumulative rate of composite major adverse cardiac events (MACE) including target lesion revascularization (TLR), the combined incidence of cardiac death, and non-fatal myocardial infarction; the second endpoint was the incidence of stent thrombosis. Results Overall, 1376 lesions were treated successfully with 1713 Yinyi stents, and 1019 (98.7%) patients received dual antiplatelet therapy for at least 12 months. At 3 years, a total of 13 (1.33%) patients had suffered cardiac death. The incidence of non-fatal myocardial infarction and TLR was 9 (0.92%) and 58 (5.92%) among the patients. Stent thrombosis occurred in 13 (1.33%) patients, and the rate of Academic Research Consortium (ARC) definite or probable stent thrombosis was 0.82%. Conclusions Given the limitations that SERY-I was a single arm, nonrandomized study and only telephone follow-up was performed without angiographic analysis, the safety and efficacy of Yinyi stent observed in this extended follow-up Registry needs further verification. PMID:28115804

  6. Clinical outcomes according to diabetic status in patients treated with biodegradable polymer sirolimus-eluting stents versus durable polymer everolimus-eluting stents: prespecified subgroup analysis of the BIOSCIENCE trial.

    PubMed

    Franzone, Anna; Pilgrim, Thomas; Heg, Dik; Roffi, Marco; Tüller, David; Vuilliomenet, André; Muller, Olivier; Cook, Stéphane; Weilenmann, Daniel; Kaiser, Christoph; Jamshidi, Peiman; Räber, Lorenz; Stortecky, Stefan; Wenaweser, Peter; Jüni, Peter; Windecker, Stephan

    2015-06-01

    Ultrathin strut biodegradable polymer sirolimus-eluting stents (BP-SES) proved noninferior to durable polymer everolimus-eluting stents (DP-EES) for a composite clinical end point in a population with minimal exclusion criteria. We performed a prespecified subgroup analysis of the Ultrathin Strut Biodegradable Polymer Sirolimus-Eluting Stent Versus Durable Polymer Everolimus-Eluting Stent for Percutaneous Coronary Revascularisation (BIOSCIENCE) trial to compare the performance of BP-SES and DP-EES in patients with diabetes mellitus. BIOSCIENCE trial was an investigator-initiated, single-blind, multicentre, randomized, noninferiority trial comparing BP-SES versus DP-EES. The primary end point, target lesion failure, was a composite of cardiac death, target-vessel myocardial infarction, and clinically indicated target lesion revascularization within 12 months. Among a total of 2119 patients enrolled between February 2012 and May 2013, 486 (22.9%) had diabetes mellitus. Overall diabetic patients experienced a significantly higher risk of target lesion failure compared with patients without diabetes mellitus (10.1% versus 5.7%; hazard ratio [HR], 1.80; 95% confidence interval [CI], 1.27-2.56; P=0.001). At 1 year, there were no differences between BP-SES versus DP-EES in terms of the primary end point in both diabetic (10.9% versus 9.3%; HR, 1.19; 95% CI, 0.67-2.10; P=0.56) and nondiabetic patients (5.3% versus 6.0%; HR, 0.88; 95% CI, 0.58-1.33; P=0.55). Similarly, no significant differences in the risk of definite or probable stent thrombosis were recorded according to treatment arm in both study groups (4.0% versus 3.1%; HR, 1.30; 95% CI, 0.49-3.41; P=0.60 for diabetic patients and 2.4% versus 3.4%; HR, 0.70; 95% CI, 0.39-1.25; P=0.23, in nondiabetics). In the prespecified subgroup analysis of the BIOSCIENCE trial, clinical outcomes among diabetic patients treated with BP-SES or DP-EES were comparable at 1 year. URL: http://www.clinicaltrials.gov. Unique identifier

  7. Shape memory polymers with high and low temperature resistant properties

    PubMed Central

    Xiao, Xinli; Kong, Deyan; Qiu, Xueying; Zhang, Wenbo; Liu, Yanju; Zhang, Shen; Zhang, Fenghua; Hu, Yang; Leng, Jinsong

    2015-01-01

    High temperature shape memory polymers that can withstand the harsh temperatures for durable applications are synthesized, and the aromatic polyimide chains with flexible linkages within the backbone act as reversible phase. High molecular weight (Mn) is demanded to form physical crosslinks as fixed phase of thermoplastic shape memory polyimide, and the relationship between Mn and glass transition temperature (Tg) is explored. Thermoset shape memory polyimide shows higher Tg and storage modulus, better shape fixity than thermoplastic counterpart due to the low-density covalent crosslinking, and the influence of crosslinking on physical properties are studied. The mechanism of high temperature shape memory effects based on chain flexibility, molecular weight and crosslink density is proposed. Exposure to thermal cycling from +150 °C to −150 °C for 200 h produces negligible effect on the properties of the shape memory polyimide, and the possible mechanism of high and low temperature resistant property is discussed. PMID:26382318

  8. Shape memory polymers with high and low temperature resistant properties.

    PubMed

    Xiao, Xinli; Kong, Deyan; Qiu, Xueying; Zhang, Wenbo; Liu, Yanju; Zhang, Shen; Zhang, Fenghua; Hu, Yang; Leng, Jinsong

    2015-09-18

    High temperature shape memory polymers that can withstand the harsh temperatures for durable applications are synthesized, and the aromatic polyimide chains with flexible linkages within the backbone act as reversible phase. High molecular weight (Mn) is demanded to form physical crosslinks as fixed phase of thermoplastic shape memory polyimide, and the relationship between Mn and glass transition temperature (Tg) is explored. Thermoset shape memory polyimide shows higher Tg and storage modulus, better shape fixity than thermoplastic counterpart due to the low-density covalent crosslinking, and the influence of crosslinking on physical properties are studied. The mechanism of high temperature shape memory effects based on chain flexibility, molecular weight and crosslink density is proposed. Exposure to thermal cycling from +150 °C to -150 °C for 200 h produces negligible effect on the properties of the shape memory polyimide, and the possible mechanism of high and low temperature resistant property is discussed.

  9. Shape memory polymers with high and low temperature resistant properties

    NASA Astrophysics Data System (ADS)

    Xiao, Xinli; Kong, Deyan; Qiu, Xueying; Zhang, Wenbo; Liu, Yanju; Zhang, Shen; Zhang, Fenghua; Hu, Yang; Leng, Jinsong

    2015-09-01

    High temperature shape memory polymers that can withstand the harsh temperatures for durable applications are synthesized, and the aromatic polyimide chains with flexible linkages within the backbone act as reversible phase. High molecular weight (Mn) is demanded to form physical crosslinks as fixed phase of thermoplastic shape memory polyimide, and the relationship between Mn and glass transition temperature (Tg) is explored. Thermoset shape memory polyimide shows higher Tg and storage modulus, better shape fixity than thermoplastic counterpart due to the low-density covalent crosslinking, and the influence of crosslinking on physical properties are studied. The mechanism of high temperature shape memory effects based on chain flexibility, molecular weight and crosslink density is proposed. Exposure to thermal cycling from +150 °C to -150 °C for 200 h produces negligible effect on the properties of the shape memory polyimide, and the possible mechanism of high and low temperature resistant property is discussed.

  10. Long-term outcomes of biodegradable polymer versus durable polymer drug-eluting stents in patients with diabetes a pooled analysis of individual patient data from 3 randomized trials.

    PubMed

    de Waha, Antoinette; Stefanini, Giulio G; King, Lamin A; Byrne, Robert A; Serruys, Patrick W; Kufner, Sebastian; Meier, Bernhard; Jüni, Peter; Kastrati, Adnan; Windecker, Stephan

    2013-10-15

    There is ongoing debate on the optimal drug-eluting stent (DES) in diabetic patients with coronary artery disease. Biodegradable polymer drug-eluting stents (BP-DES) may potentially improve clinical outcomes in these high-risk patients. We sought to compare long-term outcomes in patients with diabetes treated with biodegradable polymer DES vs. durable polymer sirolimus-eluting stents (SES). We pooled individual patient-level data from 3 randomized clinical trials (ISAR-TEST 3, ISAR-TEST 4 and LEADERS) comparing biodegradable polymer DES with durable polymer SES. Clinical outcomes out to 4 years were assessed. The primary end point was the composite of cardiac death, myocardial infarction and target-lesion revascularization. Secondary end points were target lesion revascularization and definite or probable stent thrombosis. Of 1094 patients with diabetes included in the present analysis, 657 received biodegradable polymer DES and 437 durable polymer SES. At 4 years, the incidence of the primary end point was similar with BP-DES versus SES (hazard ratio = 0.95, 95% CI = 0.74-1.21, P = 0.67). Target lesion revascularization was also comparable between the groups (hazard ratio = 0.89, 95% CI = 0.65-1.22, P = 0.47). Definite or probable stent thrombosis was significantly reduced among patients treated with BP-DES (hazard ratio = 0.52, 95% CI = 0.28-0.96, P = 0.04), a difference driven by significantly lower stent thrombosis rates with BP-DES between 1 and 4 years (hazard ratio = 0.15, 95% CI = 0.03-0.70, P = 0.02). In patients with diabetes, biodegradable polymer DES, compared to durable polymer SES, were associated with comparable overall clinical outcomes during follow-up to 4 years. Rates of stent thrombosis were significantly lower with BP-DES. © 2013.

  11. 2-Year Outcomes of High Bleeding Risk Patients After Polymer-Free Drug-Coated Stents.

    PubMed

    Garot, Philippe; Morice, Marie-Claude; Tresukosol, Damras; Pocock, Stuart J; Meredith, Ian T; Abizaid, Alexandre; Carrié, Didier; Naber, Christoph; Iñiguez, Andres; Talwar, Suneel; Menown, Ian B A; Christiansen, Evald H; Gregson, John; Copt, Samuel; Hovasse, Thomas; Lurz, Philipp; Maillard, Luc; Krackhardt, Florian; Ong, Paul; Byrne, Jonathan; Redwood, Simon; Windhövel, Ute; Greene, Samantha; Stoll, Hans-Peter; Urban, Philip

    2017-01-17

    A 1-year follow-up, polymer-free metallic stent coated with biolimus-A9 followed by 1-month dual antiplatelet therapy is safer and more effective than a bare-metal stent (BMS) for patients with high risk of bleeding. This study analyzed 2-year outcomes to determine whether these benefits are maintained. In a prospective, multicenter, double-blind trial, we randomized 2,466 high bleeding risk patients to receive a drug-coated stent (DCS) or a BMS followed by 1-month dual antiplatelet therapy. The primary safety endpoint was a composite of cardiac death, myocardial infarction, or stent thrombosis. The primary efficacy endpoint was clinically driven target lesion revascularization. At 2 years, the primary safety endpoint had occurred in 147 DCS and 180 BMS patients (15.3%) (hazard ratio: 0.80; 95% confidence interval: 0.64 to 0.99; p = 0.039). Clinically driven target lesion revascularization occurred for 77 DCS and 136 BMS patients (12.0%) (hazard ratio: 0.54; 95% confidence interval: 0.41 to 0.72; p < 0.0001). Major bleeding occurred in 8.9% of DCS and 9.2% of BMS patients (p = 0.95), and a coronary thrombotic event (myocardial infarction and/or stent thrombosis) occurred in 8.2% of DCS and 10.6% of BMS patients (p = 0.045). One-year mortality was 27.1% for a major bleed and 26.3% for a thrombotic event. At 2 years, multivariate correlates of major bleeding were age >75 years, anemia, raised plasma creatinine, and planned long-term anticoagulation. Correlates of the primary safety endpoint were age, anemia, congestive heart failure, multivessel disease, number of stents implanted, and use of a BMS rather than a DCS. Safety and efficacy benefits of DCS over BMS were maintained for 2 years in high bleeding risk patients. Rates of major bleeding and coronary thrombotic events were no different and were associated with a substantial and comparable mortality risk. (A Prospective Randomized Comparison of the BioFreedom Biolimus A9 Drug Coated Stent Versus the

  12. Biolimus-eluting versus everolimus-eluting stents in coronary artery disease: a pooled analysis from the NEXT (NOBORI biolimus-eluting versus XIENCE/PROMUS everolimus-eluting stent) and COMPARE II (Abluminal biodegradable polymer biolimus-eluting stent versus durable polymer everolimus-eluting stent) randomised trials.

    PubMed

    Vlachojannis, Georgios J; Puricel, Serban; Natsuaki, Masahiro; Morimoto, Takeshi; Smits, Pieter C; Kimura, Takeshi

    2017-03-20

    This study sought to investigate the safety and efficacy of a biolimus-eluting stent with biodegradable polymer (BP-BES) (Nobori; Terumo Corp.) compared to an everolimus-eluting stent with durable polymer (DP-EES) (XIENCE V or Prime; Abbott Vascular, or PROMUS; Boston Scientific). The all-comers NEXT and COMPARE II clinical trials randomly assigned 5,942 patients to BP-BES (N=3,412) or DP-EES (N=2,530). We conducted a patient level pooled analysis at three-year follow-up with specified study endpoints: definite stent thrombosis (ST), the combined safety endpoint cardiac death or target vessel myocardial infarction (TV-MI), and the efficacy endpoint target lesion revascularisation (TLR). At three-year follow-up, all endpoints, namely definite stent thrombosis (BP-BES 0.8% vs. 0.4%, p=0.20), death or TV-MI (BP-BES 7.8% vs. 6.7%, p=0.07), as well as TLR (BP-BES 6.4% vs. 6.4%, p=0.78) were similar between groups. Interestingly, unadjusted (BP-BES 5.6% vs. 4.5%, p=0.02) and adjusted (HR 1.36; 1.01-1.82, p=0.04) TV-MI rates were higher in the BP-BES group than in the DP-EES group. In this large-scale patient level pooled analysis of the NEXT and COMPARE II randomised trials, the use of BP-BES compared with DP-EES resulted in similar outcomes, but with an observed higher rate of TV-MI in the BP-BES group.

  13. Blocked Shape Memory Effect in Negative Poisson's Ratio Polymer Metamaterials.

    PubMed

    Boba, Katarzyna; Bianchi, Matteo; McCombe, Greg; Gatt, Ruben; Griffin, Anselm C; Richardson, Robert M; Scarpa, Fabrizio; Hamerton, Ian; Grima, Joseph N

    2016-08-10

    We describe a new class of negative Poisson's ratio (NPR) open cell PU-PE foams produced by blocking the shape memory effect in the polymer. Contrary to classical NPR open cell thermoset and thermoplastic foams that return to their auxetic phase after reheating (and therefore limit their use in technological applications), this new class of cellular solids has a permanent negative Poisson's ratio behavior, generated through multiple shape memory (mSM) treatments that lead to a fixity of the topology of the cell foam. The mSM-NPR foams have Poisson's ratio values similar to the auxetic foams prior their return to the conventional phase, but compressive stress-strain curves similar to the ones of conventional foams. The results show that by manipulating the shape memory effect in polymer microstructures it is possible to obtain new classes of materials with unusual deformation mechanisms.

  14. Sustained clinical safety and efficacy of a biodegradable-polymer coated sirolimus-eluting stent in "real-world" practice: three-year outcomes of the CREATE (Multi-Center Registry of EXCEL Biodegradable Polymer Drug Eluting Stents) study.

    PubMed

    Han, Yaling; Jing, Quanmin; Li, Yi; Yang, Lixia; Liu, Huiliang; Shang, Xiaoming; Jiang, Tiemin; Li, Zhanquan; Zhang, Hua; Yan, Gaoliang

    2012-02-01

    The CREATE is a post-marketing surveillance multicenter registry that demonstrated satisfactory angiographic and clinical (at 18 months) outcomes of a biodegradable polymer based sirolimus-eluting stent (EXCEL, JW Medical System, Weihai, China) for the treatment of patients in routine clinical practice. To evaluate the three-year clinical safety and efficacy outcomes in patients enrolled in the CREATE study. A total of 2077 all comers have been enrolled in the CREATE study at 59 centers from four countries. Recommended antiplatelet regimen was clopidogrel and aspirin for six months followed by chronic aspirin therapy. The prespecified primary outcome was the rate of major adverse cardiac events (MACE) at 12, 18, and 36 months. Clinical follow-up was completed in 2025 (97.5%) patients at three years. The average duration of clopidogrel treatment was 199.8 ± 52.7 days and 80.5% of discharged patients discontinued clopidogrel at six months. The cumulative rate of MACE was 4.5% and the rate of stent thrombosis was 1.53% at three years. At six months to three years, prolonged clopidogrel therapy (>6 months) was not beneficial in reducing cumulative hazards of MACE (3.4% vs. 3.1%, log rank P = 0.725) or stent thrombosis (1.5% vs. 0.6%, log rank P = 0.053). This study demonstrates sustained three-year clinical safety and efficacy of biodegradable polymer-based sirolimus-eluting stents when used with six months of dual antiplatelet therapy in a "real-world" setting. Copyright © 2011 Wiley Periodicals, Inc.

  15. Environmental memory of polymer networks under stress.

    PubMed

    Quitmann, Dominik; Gushterov, Nikola; Sadowski, Gabriele; Katzenberg, Frank; Tiller, Joerg C

    2014-06-04

    Generally reversible stimuli-responsive materials do not memorize the stimulus. In this study we describe an example in which stretched and constrained semi-crystalline polymer networks respond to solvent gases with stress and simultaneously memorize the concentration and the chemical nature of the solvent itself in their microstructure. This written solvent signature can even be deleted by temperature.

  16. Polymer-based, paclitaxel-eluting TAXUS Liberté stent in de novo lesions: the pivotal TAXUS ATLAS trial.

    PubMed

    Turco, Mark A; Ormiston, John A; Popma, Jeffrey J; Mandinov, Lazar; O'Shaughnessy, Charles D; Mann, Tift; McGarry, Thomas F; Wu, Chiung-Jen; Chan, Charles; Webster, Mark W I; Hall, Jack J; Mishkel, Gregory J; Cannon, Louis A; Baim, Donald S; Koglin, Joerg

    2007-04-24

    The goal of this research was to assess non-inferiority of the next-generation TAXUS Liberté stent (Boston Scientific Corp., Natick, Massachusetts) versus the TAXUS Express stent (Boston Scientific Corp.). The introduction of drug-eluting stents (DES) has shifted clinical practice towards more complex lesion subsets, prompting the need for more deliverable DES. TAXUS Liberté was designed to combine the established polymer-based, paclitaxel-elution TAXUS technology with the more advanced Liberté stent platform. The TAXUS ATLAS study is a global, prospective, single-arm trial evaluating outcomes in de novo coronary lesions visually estimated to be 10 to 28 mm in length in vessels 2.5 to 4.0 mm in diameter. The control group is an entry-criteria-matched population of TAXUS Express patients from the TAXUS IV and V trials. The primary end point is non-inferiority of TAXUS Liberté versus TAXUS Express for 9-month target vessel revascularization. Despite similar inclusion criteria, quantitative coronary angiography-determined baseline lesion characteristics were significantly more complex for TAXUS Liberté than TAXUS Express. The primary non-inferiority end point was met with the 1-sided 95% confidence bound of 2.98% less than the pre-specified non-inferiority margin of 3% (p = 0.0487). Despite the treatment of more complex lesions with TAXUS Liberté, the primary end point was met, demonstrating that TAXUS Liberté is non-inferior to TAXUS Express. The successful transfer of the proven TAXUS technology to the more advanced TAXUS Liberté platform was demonstrated. (TAXUS ATLAS: TAXUS Liberté-SR Stent for the Treatment of De Novo Coronary Artery Lesions; http://www.clinicaltrials.gov/ct/show/NCT00371709?order=1; NCT00371709).

  17. Clinical outcomes of real-world patients treated with an amphilimus polymer-free stent versus new generation everolimus-eluting stents.

    PubMed

    Panoulas, Vasileios F; Latib, Azeem; Naim, Charbel; Sato, Katsumasa; Ielasi, Alfonso; Tespili, Maurizio; Godino, Cosmo; Testa, Luca; Bedogni, Francesco; Colombo, Antonio

    2015-12-01

    To compare the 1-year clinical outcomes after implantation of the amphilimus, polymer-free stent (Cre8) versus new generation everolimus-eluting stents (EESs) in a real-world patient registry. A total of 187 consecutive patients treated with Cre8 between January 2011 and August 2013 in four Italian centers were included. These were propensity matched with 150 patients treated with new generation EES during the same period. Primary outcome was 1-year major adverse cardiovascular events (MACE), defined as all-cause death, myocardial infarction, and target vessel revascularization. Both groups had similar baseline characteristics, including diabetes (28% Cre8 vs. 27.3% EES, P = 0.972) and previous percutaneous coronary intervention (56% Cre8 vs. 58% EES, P = 0.726). There was a higher prevalence of B2/C lesions in the EES group (70.1% vs. 83.8%, P < 0.001). Total stent length per patient was similar. There were no significant differences in 1-year estimated MACE (7.4% Cre8 vs. 10.2% EES, P = 0.261), all-cause mortality (1.3% Cre8 vs. 1.4% EES, P = 0.823), target vessel revascularization (5.2% Cre8 vs. 8.8% EES, P = 0.169), and target lesion revascularization (3% Cre8 vs. 7.4% EES, P = 0.108) between the two groups. When adjusting for differences in baseline lesion characteristics, hazard ratio(Cre8/EES) for MACE was not significantly different between the two groups (0.75, 95% confidence interval 0.37-1.53, P(noninferiority) = 0.001, P(superiority) = 0.432). In patients with diabetes (Cre8, n = 42; EEE, n = 41), 1-year target lesion revascularization was 2.5% in the Cre8 group versus 14.6% in the EES group (P = 0.056). In a "real-world" patient registry, the Cre8 stent is associated with noninferior 1-year MACE rates compared with that of new generation EES. Trends of superior efficacy in patients with diabetes treated with Cre8 require further investigation. © 2015 Wiley Periodicals, Inc.

  18. In vitro study of drug-eluting stent coatings based on poly(L-lactide) incorporating cyclosporine A - drug release, polymer degradation and mechanical integrity.

    PubMed

    Sternberg, Katrin; Kramer, Sven; Nischan, Claudia; Grabow, Niels; Langer, Thomas; Hennighausen, Gerhard; Schmitz, Klaus-Peter

    2007-07-01

    In this study, absorbable polymer stent coatings for localized drug delivery based on poly(L-lactide) (PLLA) and cyclosporine A (CsA) were developed and tested in vitro. Metallic stents were coated with different compositions of PLLA/CsA (70/30, 60/40, 50/50% w/w) and beta-sterilized. The specimens were used to assess the drug release kinetics with HPLC. Sterilization influenced polymer degradation was measured with GPC. Mechanical integrity of the stent coatings was studied with SEM. The interconnection of the coated stents with a balloon-catheter was characterized by the measurement of stent dislodgment force. A migration assay was used to determine the inhibitory effect of the model drug CsA on smooth muscle cell (SMC) migration. The release of CsA was established over time periods up to 24 days in sodium chloride solution and in porcine blood plasma. An inhibition of SMC migration (max. 26-33%) was found for CsA concentrations of 4 x 10(-5) to 4 x 10(-7) mol/l. Marked molecular weight reduction (70-80%) of the PLLA matrix occurred after beta-sterilization. We also observed a substantial decrease of in vitro degradation time. The maintenance of the mechanical integrity of the polymer coating during crimping and dilation of the specimens could be verified, and a sufficient stent dislodgment force of 0.8-0.9 N was measured.

  19. Sirolimus-eluting, bioabsorbable polymer-coated constant stent (Cura) in acute ST-elevation myocardial infarction: a clinical and angiographic study (CURAMI Registry).

    PubMed

    Lee, Chi-Hang; Lim, Jimmy; Low, Adrian; Zhang, Xiao-Ling; Kyaing, Than-Than; Chan, Mark Y; Wong, Hwee-Bee; Lim, Yean-Teng; Tan, Huay-Cheem

    2007-04-01

    There are safety concerns over the current polymer-based drug-eluting stents (DES) on the possible delayed healing process and adverse reactions to the polymer when drug elution is completed. Cura (Orbus Neich) is a sirolimus-eluting, bioabsorbable, polymer-coated constant stent. From March 1 to June 30, 2005, Cura stent implantation was instituted as the default strategy for percutaneous coronary intervention in 49 consecutive ST-Elevation Myocardial Infarction (STEMI) patients (male 86%; average age 55 +/- 10 years; diabetes 31%). The angiographic success rate was 100%. In-hospital adverse events consisted of 1 in-hospital death (2% heart failure). A total of 27 patients (56%) underwent 8-month angiographic follow up. Binary restenosis occurred in 6 patients (22%), and late loss was 0.74 +/- 0.89 mm. At 9-month follow up, a total of 5 patients had 6 major adverse events (1 death, 1 reinfarction, and 4 target lesion revascularizations). There was no incidence of stent thrombosis. Cura stent implantation appears to be feasible and safe in the treatment of STEMI. However, the binary restenosis rate and late loss at angiographic follow up were similar to that of bare-metal stents, and therefore compare unfavorably with other proven benchmark DES.

  20. Experience with Biodegradable Polymer Coated Sirolimus-Eluting Coronary Stent System in “Real-Life” Percutaneous Coronary Intervention: 24-Month Data from the Manipal-S Registry

    PubMed Central

    Shetty, Ranjan; Vivek, G.; Thakkar, Ashok; Mishra, Supriya Sunder; Joseph, Vivek; Devraj, Mithun Gopal; Tumkur, Anil; Pai, Umesh

    2013-01-01

    Introduction: Despite the undeniable clinical efficacy of drug-eluting stents with durable polymers, concerns regarding their long-term safety have been raised, especially in more complex subsets. The Manipal-S Registry was designed to evaluate the safety and effectiveness of the biodegradable polymer coated Supralimus® Sirolimus-Eluting Coronary Stent for the treatment of coronary artery disease, across a wide range of patients who are treated in real-life clinical practice. Methods: All the consecutive 116 patients who underwent single-vessel or multiple vessel percutaneous coronary interventions with the use of Supralimus® sirolimus-eluting stents between September 2009 and December 2010, were included in this study. Patients were clinically followed-up at 1, 9, 12 and 24 months post-procedure. All clinical, procedural, and follow-up information were collected and analysed. Results: In total 116 patients, 126 lesions were implanted with 144 stents which had an average stent length of 25.8±8.0 mm. The incidences of any major adverse cardiac and cerebral events at 1, 9, 12 and 24 months were 0, 5 (4.3%), 8 (6.9%), and 10 (8.6%) respectively. Conclusion: These 24-month results clearly provide evidence for safety and effectiveness of the Supralimus® Sirolimus-eluting coronary stent system with the biodegradable polymer in real-life patients, even in those with acute myocardial infarctions. PMID:24179909

  1. A Nuclear Magnetic Resonance Spectroscopy as a Method for Evaluation of In Vivo Poly-l-Lactide Biodegradation Kinetics From Stent-Polymer Matrices: An Experimental Study Utilizing Porcine Model of In-Stent Restenosis.

    PubMed

    Orlik, Bartłomiej; Buszman, Piotr P; Krauze, Agata; Gąsior, Paweł; Desperak, Piotr; Pająk, Jacek; Kasperczyk, Janusz; Janas, Adam; Jelonek, Michał; Handzlik-Orlik, Gabriela; Buszman, Paweł E; Milewski, Krzysztof

    2016-01-01

    We aimed to comprehensively evaluate poly-lactide polymer degradation and sirolimus release kinetics from a drug-eluting stent matrix in the in vivo setting using a nuclear magnetic resonance (NMR) method. In 22 domestic swine, 18 biodegradable polymer-only coated stents (BPSs) and 36 biodegradable polymer-coated sirolimus-eluting stents (BP-SES) were implanted in coronary arteries with 115% overstretch. The animals were sacrificed at 1, 3, 7, 14, 28, and 56 days following baseline procedures. Vessel segments with BPS were harvested to evaluate polymer degradation with a NMR method, whereas BP-SES to analyze sirolimus tissue uptake and retention. Additionally, 8 BP-SES were implanted for histological analysis for 90 days of follow-up. The NMR showed a gradual absorption of the polymer over the 6 consecutive time points, from 5.48 µg of the polymer on the stent at 1-day follow-up, through 4.33 µg at 3 days, 3.16 µg at 7 days, 2.42 µg at 14 days, 1.92 µg at 28 days to 1.24 µg in the last day of the study. The curve of polymer degradation corresponds well with the pharmacokinetic profile of sirolimus eluted from its surface and measured at identical time points. In histopathology, at 90 days, complete healing and biocompatibility were reported. The utilization of NMR method for BP absorption kinetics evaluation is a useful tool, which may be widely adopted to test other biodegradable implants. Further, it may substantially improve their safety and efficacy by facilitating programmed polymer and drugs elution. © The Author(s) 2015.

  2. Can Platforms Affect the Safety and Efficacy of Drug-Eluting Stents in the Era of Biodegradable Polymers?: A Meta-Analysis of 34,850 Randomized Individuals

    PubMed Central

    Zhang, Ming-Duo; Li, Xin-He; Nie, Mao-Xiao; Feng, Ting-Ting; Zhao, Xin; Wang, Lu-Ya; Zhao, Quan-Ming

    2016-01-01

    Objective In the era of bare metal stents (BMSs), alloys have been considered to be better materials for stent design than stainless steel. In the era of biodegradable polymer drug-eluting stents (BP-DESs), the safety and efficacy of BP-DESs with different metal platforms (stainless steel or alloys) have not yet been reported, although their polymers are eventually absorbed, and only the metal platforms remain in the body. This study sought to determine the clinical safety and efficacy of BP-DESs with different platforms compared with other stents (other DESs and BMSs). Methods PubMed, Embase and Clinical Trials.gov were searched for randomized controlled trials (RCTs) that compared BP-DESs with other stents. After performing pooled analysis of BP-DESs and other stents, we performed a subgroup analysis using two classification methods: stent platform and follow-up time. The study characteristics, patient characteristics and clinical outcomes were abstracted. Results Forty RCTs (49 studies) comprising 34,850 patients were included. Biodegradable polymer stainless drug-eluting stents (BP-stainless DESs) were superior to the other stents [mainly stainless drug-eluting stents (DESs)] in terms of pooled definite/probable stent thrombosis (ST) (OR [95% CI] = 0.76[0.61–0.95], p = 0.02), long-term definite/probable ST (OR [95% CI] = 0.73[0.57–0.94], p = 0.01), very late definite/probable ST (OR [95% CI] = 0.56[0.33–0.93], p = 0.03) and long-term definite ST. BP-stainless DESs had lower rates of pooled, mid-term and long-term target vessel revascularization (TVR) and target lesion revascularization (TLR) than the other stainless DESs and BMSs. Furthermore, BP-stainless DESs were associated with lower rates of long-term death than other stainless DESs and lower rates of mid-term myocardial infarction than BMSs. However, only the mid-term and long-term TVR rates were superior in BP-alloy DESs compared with the other stents. Conclusion Our results indirectly suggest that

  3. Biodegradable, elastic shape-memory polymers for potential biomedical applications.

    PubMed

    Lendlein, Andreas; Langer, Robert

    2002-05-31

    The introduction of biodegradable implant materials as well as minimally invasive surgical procedures in medicine has substantially improved health care within the past few decades. This report describes a group of degradable thermoplastic polymers that are able to change their shape after an increase in temperature. Their shape-memory capability enables bulky implants to be placed in the body through small incisions or to perform complex mechanical deformations automatically. A smart degradable suture was created to illustrate the potential of these shape-memory thermoplastics in biomedical applications.

  4. Biomedical Applications of Thermally Activated Shape Memory Polymers

    SciTech Connect

    Small IV, W; Singhal, P; Wilson, T S; Maitland, D J

    2009-04-10

    Shape memory polymers (SMPs) are smart materials that can remember a primary shape and can return to this primary shape from a deformed secondary shape when given an appropriate stimulus. This property allows them to be delivered in a compact form via minimally invasive surgeries in humans, and deployed to achieve complex final shapes. Here we review the various biomedical applications of SMPs and the challenges they face with respect to actuation and biocompatibility. While shape memory behavior has been demonstrated with heat, light and chemical environment, here we focus our discussion on thermally stimulated SMPs.

  5. Secreted Matrix Metalloproteinase-9 of Proliferating Smooth Muscle Cells as a Trigger for Drug Release from Stent Surface Polymers in Coronary Arteries.

    PubMed

    Gliesche, Daniel G; Hussner, Janine; Witzigmann, Dominik; Porta, Fabiola; Glatter, Timo; Schmidt, Alexander; Huwyler, Jörg; Meyer Zu Schwabedissen, Henriette E

    2016-07-05

    Cardiovascular diseases are the leading causes of death in industrialized countries. Atherosclerotic coronary arteries are commonly treated with percutaneous transluminal coronary intervention followed by stent deployment. This treatment has significantly improved the clinical outcome. However, triggered vascular smooth muscle cell (SMC) proliferation leads to in-stent restenosis in bare metal stents. In addition, stent thrombosis is a severe side effect of drug eluting stents due to inhibition of endothelialization. The aim of this study was to develop and test a stent surface polymer, where cytotoxic drugs are covalently conjugated to the surface and released by proteases selectively secreted by proliferating smooth muscle cells. Resting and proliferating human coronary artery smooth muscle cells (HCASMC) and endothelial cells (HCAEC) were screened to identify an enzyme exclusively released by proliferating HCASMC. Expression analyses and enzyme activity assays verified selective and exclusive activity of the matrix metalloproteinase-9 (MMP-9) in proliferating HCASMC. The principle of drug release exclusively triggered by proliferating HCASMC was tested using the biodegradable stent surface polymer poly-l-lactic acid (PLLA) and the MMP-9 cleavable peptide linkers named SRL and AVR. The specific peptide cleavage by MMP-9 was verified by attachment of the model compound fluorescein. Fluorescein release was observed in the presence of MMP-9 secreting HCASMC but not of proliferating HCAEC. Our findings suggest that cytotoxic drug conjugated polymers can be designed to selectively release the attached compound triggered by MMP-9 secreting smooth muscle cells. This novel concept may be beneficial for stent endothelialization thereby reducing the risk of restenosis and thrombosis.

  6. Fabrication of nylon/fullerene polymer memory

    NASA Astrophysics Data System (ADS)

    Jayan, Manuvel; Davis, Rosemary; Karthik, M. P.; Devika, K.; Kumar, G. Vijay; Sriraj, B.; Predeep, P.

    2017-06-01

    Two terminal Organic memories in passive matrix array form with device structure, Al/Nylon/ (Nylon+C60)/Nylon/ Al are fabricated. The current-voltage measurements showed hysteresis and the devices are thoroughly characterized for write-read-erase-read cycles. The control over the dispersion concentration, capacity of fullerene to readily accept electrons and the constant diameter of fullerene made possible uniform device fabrication with reproducible results. Scanning electron micrographs indicated that the device thickness remained uniform in the range of 19 micrometers.

  7. Adaptive repair device concept with shape memory polymer

    NASA Astrophysics Data System (ADS)

    Zhao, Wei; Liu, Liwu; Lan, Xin; Su, Bo; Leng, Jinsong; Liu, Yanju

    2017-02-01

    Shape memory polymer (SMP) is a new kind of intelligent polymer, which can be activated by an external stimulus to change and subsequently recover its original shape. Due to this shape memory effect, SMP can be used in a wide range of engineering and biomedical applications. This paper details an application of SMP on manufacturing of a fracture fixation. The basic properties were characterized by dynamic mechanical analysis, and the stress relaxation and fatigue were established. An SMP-based fracture fixator was designed, analyzed, and optimized. Finally, the fixator was fabricated and the fixed effects were verified by experiment in vitro. The performance of the SMP-based fixator was excellent and proved to be a potential replacement for the traditional fracture fixator.

  8. Ultra-flexible nonvolatile memory based on donor-acceptor diketopyrrolopyrrole polymer blends

    PubMed Central

    Zhou, Ye; Han, Su-Ting; Yan, Yan; Zhou, Li; Huang, Long-Biao; Zhuang, Jiaqing; Sonar, Prashant; Roy, V. A. L.

    2015-01-01

    Flexible memory cell array based on high mobility donor-acceptor diketopyrrolopyrrole polymer has been demonstrated. The memory cell exhibits low read voltage, high cell-to-cell uniformity and good mechanical flexibility, and has reliable retention and endurance memory performance. The electrical properties of the memory devices are systematically investigated and modeled. Our results suggest that the polymer blends provide an important step towards high-density flexible nonvolatile memory devices. PMID:26029856

  9. Shape memory polymer network with thermally distinct elasticity and plasticity

    PubMed Central

    Zhao, Qian; Zou, Weike; Luo, Yingwu; Xie, Tao

    2016-01-01

    Stimuli-responsive materials with sophisticated yet controllable shape-changing behaviors are highly desirable for real-world device applications. Among various shape-changing materials, the elastic nature of shape memory polymers allows fixation of temporary shapes that can recover on demand, whereas polymers with exchangeable bonds can undergo permanent shape change via plasticity. We integrate the elasticity and plasticity into a single polymer network. Rational molecular design allows these two opposite behaviors to be realized at different temperature ranges without any overlap. By exploring the cumulative nature of the plasticity, we demonstrate easy manipulation of highly complex shapes that is otherwise extremely challenging. The dynamic shape-changing behavior paves a new way for fabricating geometrically complex multifunctional devices. PMID:26824077

  10. Shape memory polymers based on uniform aliphatic urethane networks

    SciTech Connect

    Wilson, T S; Bearinger, J P; Herberg, J L; Marion III, J E; Wright, W J; Evans, C L; Maitland, D J

    2007-01-19

    Aliphatic urethane polymers have been synthesized and characterized, using monomers with high molecular symmetry, in order to form amorphous networks with very uniform supermolecular structures which can be used as photo-thermally actuable shape memory polymers (SMPs). The monomers used include hexamethylene diisocyanate (HDI), trimethylhexamethylenediamine (TMHDI), N,N,N{prime},N{prime}-tetrakis(hydroxypropyl)ethylenediamine (HPED), triethanolamine (TEA), and 1,3-butanediol (BD). The new polymers were characterized by solvent extraction, NMR, XPS, UV/VIS, DSC, DMTA, and tensile testing. The resulting polymers were found to be single phase amorphous networks with very high gel fraction, excellent optical clarity, and extremely sharp single glass transitions in the range of 34 to 153 C. Thermomechanical testing of these materials confirms their excellent shape memory behavior, high recovery force, and low mechanical hysteresis (especially on multiple cycles), effectively behaving as ideal elastomers above T{sub g}. We believe these materials represent a new and potentially important class of SMPs, and should be especially useful in applications such as biomedical microdevices.

  11. Capacitance-voltage measurement in memory devices using ferroelectric polymer

    NASA Astrophysics Data System (ADS)

    Nguyen, Chien A.; Lee, Pooi See

    2006-01-01

    Application of thin polymer film as storing mean for non-volatile memory devices is investigated. Capacitance-voltage (C-V) measurement of metal-ferroelectric-metal device using ferroelectric copolymer P(VDF-TrFE) as dielectric layer shows stable 'butter-fly' curve. The two peaks in C-V measurement corresponding to the largest capacitance are coincidental at the coercive voltages that give rise to zero polarization in the polarization hysteresis measurement. By comparing data of C-V and P-E measurement, a correlation between two types of hysteresis is established in which it reveals simultaneous electrical processes occurring inside the device. These processes are caused by the response of irreversible and reversible polarization to the applied electric field that can be used to present a memory window. The memory effect of ferroelectric copolymer is further demonstrated for fabricating polymeric non-volatile memory devices using metal-ferroelectric-insulator-semiconductor structure (MFIS). By applying different sweeping voltages at the gate, bidirectional flat-band voltage shift is observed in the ferroelectric capacitor. The asymmetrical shift after negative sweeping is resulted from charge accumulation at the surface of Si substrate caused by the dipole direction in the polymer layer. The effect is reversed for positive voltage sweeping.

  12. A new stent graft. With thin walled controlled micropored polymer covering.

    PubMed

    Nishi, S; Nakayama, Y; Ueda, H; Ishikawa, M; Matsuda, T

    2000-11-30

    The use of stents improves the result after balloon coronary angioplasty. Restenosis due to neointimal hyperplasia and proliferation of smooth muscle cells are, however, a concern. In the present report, we studied the prevention of restenosis to allow endothelial cell migration and growth to proceed through micropores using our developed stent graft with micropored segmented polyurethane (SPU) thin film in a normal beagle model. Our developed stent graft was made from Palmaz stent and micropored SPU thin film. The SPU film was arranged into four different micropore densities around the circumference: no micropores, arrangement 4; micropores of 30mum in diameter with an orderly distance of 250mum; (arrangement 1), 500mum; (arrangement 2) and 125mum (arrangement 3) between the neighboring two pores. Micropores were made using the Excimer laser ablation technique. The Palmaz stent was wrapped with micropored film, sutured, and glued with DMF (dimethyl formamide) under aid of a microscope. These stents were placed in the common carotid arteries of beagles (n = 5). They were sacrificed at 1 month, and a histological study and scanning electron microscopy study were performed for evaluation of endoluminal endothelialization. In 10 arteries applied with stent grafts, there was no severe stenosis although it did occur to some extent. All stented arteries were patent. Endothelial cell migration and growth through micropores were observed histologically on micropored SPU thin film in this model, which did not affect the intraluminal diameter. In most non-porous regions, significant thrombi were found between the SPU film and the neointimal layer. On the other hand, in the porous region, little thrombosis was observed except in the lowest density region. In 125mum of distance between two neighboring pores, the neointimal layer was the thinnest, which was suitable for wide intraluminal space after placement of a stent graft. Endothelial cell migration and growth through

  13. Primary endpoint results of the EVOLVE trial: a randomized evaluation of a novel bioabsorbable polymer-coated, everolimus-eluting coronary stent.

    PubMed

    Meredith, Ian T; Verheye, Stefan; Dubois, Christophe L; Dens, Joseph; Fajadet, Jean; Carrié, Didier; Walsh, Simon; Oldroyd, Keith G; Varenne, Olivier; El-Jack, Seif; Moreno, Raul; Joshi, Anita A; Allocco, Dominic J; Dawkins, Keith D

    2012-04-10

    This study sought to compare the safety and efficacy of 2 dose formulations of SYNERGY, a novel bioabsorbable polymer everolimus-eluting stent (EES) (Boston Scientific Corp., Natick, Massachusetts) compared with the durable polymer PROMUS Element EES (Boston Scientific Corp.). Durable polymer coatings on drug-eluting stents have been associated with chronic inflammation and impaired healing. Bioabsorbable polymer-coated drug-delivery systems may reduce the risk of late adverse events, including stent thrombosis, and thus the need for prolonged dual-antiplatelet therapy. A total of 291 patients with a de novo lesion ≤28 mm in length, in a coronary artery of ≥2.25 to ≤3.5 mm diameter, were enrolled in the EVOLVE study, a prospective, randomized, single-blind, noninferiority trial. Patients were randomly assigned in a 1:1:1 ratio to PROMUS Element, SYNERGY, or SYNERGY half dose. The primary clinical endpoint was the 30-day rate of target lesion failure, defined as cardiac death or myocardial infarction related to the target vessel, or target lesion revascularization. The primary angiographic endpoint was 6-month in-stent late loss measured by quantitative coronary angiography. The 30-day primary clinical endpoint of target lesion failure occurred in 0%, 1.1%, and 3.1% of patients in the PROMUS Element, SYNERGY, and SYNERGY half dose groups, respectively. The 6-month in-stent late loss was 0.15 ± 0.34 mm for PROMUS Element, 0.10 ± 0.25 mm for SYNERGY, and 0.13 ± 0.26 mm for SYNERGY half dose (SYNERGY, difference -0.06, upper 95.2% confidence limit: 0.02, p for noninferiority <0.001; SYNERGY half dose, difference -0.03, upper 95.2% confidence limit: 0.05, p for noninferiority <0.001). Clinical event rates remained low and comparable between groups, with no stent thromboses in any group at 6 months. The EVOLVE trial confirms the effective delivery of everolimus by a unique directional bioabsorbable polymer system utilizing the SYNERGY stent. (A Prospective

  14. A randomized, open-label clinical trial using optical coherence tomography to compare two sirolimus-eluting stents, one with a biodegradable polymer and the other with a permanent polymer.

    PubMed

    Tian, Feng; Chen, Yundai; Liu, Changfu; Jin, Qinhua; Chen, Lian; Sun, Zhijun; Liu, Hongbin; Guo, Jun; Gai, Luyue

    2013-04-01

    Intimal hyperplasia appears to differ after implanting a drug-eluting stent (DES) with a biodegradable or a permanent polymer. The aim of the present study was to compare biodegradable with permanent polymer DES, since the available data are limited. One hundred patients with de novo coronary artery stenosis were included in this study. The patients were classified into 2 groups: DES with a biodegradable polymer (n=50) and DES with a permanent polymer (n=50). Optical coherence tomography (OCT) examination was performed before and after stent implantation. A follow‑up OCT, performed 1 year after stent implantation, compared the morphologies of intimal hyperplasia in the 2 groups. The frequencies of uncovered stent struts (2.27 vs. 1.87%, P=0.145) and stent strut malapposition (1.9 vs. 2.02%, P=0.655) upon the first-year follow-up were not significantly different. Average neointimal thickness was lower in the biodegradable compared with the permanent polymer group (106.12±80.65 vs. 181.20±146.96 µm, P<0.001). The frequencies of neointimal thickness <100 µm were significantly higher in the biodegradable compared with the permanent polymer group (62.1 vs. 35.9%, P<0.001). The average intimal thickness was also lower in the biodegradable compared with the permanent polymer group (57.7±24.6 vs. 67.6±22.4 µm, P<0.001). In conclusion, biodegradable polymer DES resulted in significantly lower intimal hyperplasia and had well-proportioned intimal coverage compared with permanent polymer DES.

  15. Tunable thiol-epoxy shape memory polymer foams

    NASA Astrophysics Data System (ADS)

    Ellson, Gregory; Di Prima, Matthew; Ware, Taylor; Tang, Xiling; Voit, Walter

    2015-05-01

    Shape memory polymers (SMPs) are uniquely suited to a number of applications due to their shape storage and recovery abilities and the wide range of available chemistries. However, many of the desired performance properties are tied to the polymer chemistry which can make optimization difficult. The use of foaming techniques is one way to tune mechanical response of an SMP without changing the polymer chemistry. In this work, a novel thiol-epoxy SMP was foamed using glass microspheres (40 and 50% by volume Q-Cel 6019), using expandable polymer microspheres (1% 930 DU 120), and by a chemical blowing agent (1% XOP-341). Each approach created SMP foam with a differing density and microstructure from the others. Thermal and thermomechanical analysis was performed to observe the behavioral difference between the foaming techniques and to confirm that the glass transition (Tg) was relatively unchanged near 50 °C while the glassy modulus varied from 19.1 to 345 MPa and the rubbery modulus varied from 0.04 to 2.2 MPa. The compressive behavior of the foams was characterized through static compression testing at different temperatures, and cyclic compression testing at Tg. Constrained shape recovery testing showed a range of peak recovery stress from 5 MPa for the syntactic Q-Cel foams to ˜0.1 MPa for the chemically blown XOP-341 foam. These results showed that multiple foaming approaches can be used with a novel SMP to vary the mechanical response independent of Tg and polymer chemistry.

  16. Simulations of Self-Expanding Braided Stent Using Macroscopic Model of NiTi Shape Memory Alloys Covering R-Phase

    NASA Astrophysics Data System (ADS)

    Frost, M.; Sedlák, P.; Kruisová, A.; Landa, M.

    2014-07-01

    Self-expanding stents or stentgrafts made from Nitinol superelastic alloy are widely used for a less invasive treatment of disease-induced localized flow constriction in the cardiovascular system. The therapy is based on insertion of a stent into a blood vessel to maintain the inner diameter of the vessel; it provides highly effective results at minimal cost and with reduced hospital stays. However, since stent is an external mechanical healing tool implemented into human body for quite a long time, information on the mechanical performance of it is of fundamental importance with respect to patient's safety and comfort. Advantageously, computational structural analysis can provide valuable information on the response of the product in an environment where in vivo experimentation is extremely expensive or impossible. With this motivation, a numerical model of a particular braided self-expanding stent was developed. As a reasonable approximation substantially reducing computational demands, the stent was considered to be composed of a set of helical springs with specific constrains reflecting geometry of the structure. An advanced constitutive model for NiTi-based shape memory alloys including R-phase transition was employed in analysis. Comparison to measurements shows a very good match between the numerical solution and experimental results. Relation between diameter of the stent and uniform radial pressure on its surface is estimated. Information about internal phase and stress state of the material during compression loading provided by the model is used to estimate fatigue properties of the stent during cyclic loading.

  17. Strategic design and fabrication of acrylic shape memory polymers

    NASA Astrophysics Data System (ADS)

    Park, Ju Hyuk; Kim, Hansu; Ryoun Youn, Jae; Song, Young Seok

    2017-08-01

    Modulation of thermomechanics nature is a critical issue for an optimized use of shape memory polymers (SMPs). In this study, a strategic approach was proposed to control the transition temperature of SMPs. Free radical vinyl polymerization was employed for tailoring and preparing acrylic SMPs. Transition temperatures of the shape memory tri-copolymers were tuned by changing the composition of monomers. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy analyses were carried out to evaluate the chemical structures and compositions of the synthesized SMPs. The thermomechanical properties and shape memory performance of the SMPs were also examined by performing dynamic mechanical thermal analysis. Numerical simulation based on a finite element method provided consistent results with experimental cyclic shape memory tests of the specimens. Transient shape recovery tests were conducted and optical transparence of the samples was identified. We envision that the materials proposed in this study can help develop a new type of shape-memory devices in biomedical and aerospace engineering applications.

  18. Multiple-shape memory polymers from benzoxazine-urethane copolymers

    NASA Astrophysics Data System (ADS)

    Prathumrat, Peerawat; Tiptipakorn, Sunan; Rimdusit, Sarawut

    2017-06-01

    In this research, multiple-shape memory polymers were prepared from benzoxazine (BA-a) resin and a urethane prepolymer (PU). The effects of BA-a resin content on the thermal, mechanical and multiple-shape memory properties were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis, dynamic mechanical analysis, a flexural test and a multiple-shape memory test. The results revealed that the suitable curing conversions of BA-a:PU resin mixtures affect the shape memory behaviors. The BA-a/PU copolymers demonstrated an increase in flexural strength and flexural modulus at various deformation temperatures with an increase in the BA-a mass ratio from 55%-80%, whereas the thermal properties of these binary systems, i.e. glass transition temperature (T g), degradation temperature (T d) and char yield, were also found to increase with an increase in BA-a content. In addition, the two-step bending test was carried out using a universal testing machine to evaluate the multiple-shape memory properties. The results revealed that the BA-a/PU samples exhibited high values of shape fixity (70%-96% for the first temporary shape and 83%-99% for the second temporary shape) and shape recovery (88%-96% for the first temporary shape and 97%-99% for the original shape).

  19. Polymer-ultrathin graphite sheet-polymer composite structured flexible nonvolatile bistable organic memory devices

    NASA Astrophysics Data System (ADS)

    Ick Son, Dong; Shim, Jae Ho; Park, Dong Hee; Jung, Jae Hun; Lee, Jung Min; Park, Won Il; Kim, Tae Whan; Choi, Won Kook

    2011-07-01

    We present data, which were obtained before bending and after bending, for the electrical bistabilities, memory stabilities, and memory mechanisms of three-layer structured flexible bistable organic memory (BOM) devices, which were fabricated utilizing the ultrathin graphite sheets (UGS) sandwiched between insulating poly(methylmethacrylate) (PMMA) polymer layers. The UGS were formed by transferring UGS (about 30 layers) and using a simple spin-coating technique. Transmission electron microscopy (TEM) measurements were performed to investigate the microstructural properties of the PMMA/UGS/PMMA films. Current-voltage (I-V) measurements were carried out to investigate the electrical properties of the BOM devices containing the UGS embedded in the PMMA polymer. Current-time (I-t) and current-cycle measurements under flat and bent conditions were performed to investigate the memory stabilities of the BOM devices. The memory characteristics of the BOM maintained similar device efficiencies after bending and were stable during repeated bendings of the BOM devices. The mechanisms for these characteristics of the fabricated BOM are described on the basis of the I-V results.

  20. Thiol-vinyl systems as shape memory polymers and novel two-stage reactive polymer systems

    NASA Astrophysics Data System (ADS)

    Nair, Devatha P.

    2011-12-01

    The focus of this research was to formulate, characterize and tailor the reaction methodologies and material properties of thiol-vinyl systems to develop novel polymer platforms for a range of engineering applications. Thiol-ene photopolymers were demonstrated to exhibit several advantageous characteristics for shape memory polymer systems for a range of biomedical applications. The thiol-ene shape memory polymer systems were tough and flexible as compared to the acrylic control systems with glass transition temperatures between 30 and 40 °C; ideal for actuation at body temperature. The thiol-ene polymers also exhibited excellent shape fixity and a rapid and distinct shape memory actuation response along with free strain recoveries of greater than 96% and constrained stress recoveries of 100%. Additionally, two-stage reactive thiol-acrylate systems were engineered as a polymer platform technology enabling two independent sets of polymer processing and material properties. There are distinct advantages to designing polymer systems that afford two distinct sets of material properties -- an intermediate polymer that would enable optimum handling and processing of the material (stage 1), while maintaining the ability to tune in different, final properties that enable the optimal functioning of the polymeric material (stage 2). To demonstrate the range of applicability of the two-stage reactive systems, three specific applications were demonstrated; shape memory polymers, lithographic impression materials, and optical materials. The thiol-acrylate reactions exhibit a wide range of application versatility due to the range of available thiol and acrylate monomers as well as reaction mechanisms such as Michael Addition reactions and free radical polymerizations. By designing a series of non-stoichiometeric thiol-acrylate systems, a polymer network is initially formed via a base catalyzed 'click' Michael addition reaction. This self-limiting reaction results in a Stage 1

  1. Visible Light-Induced Plasticity of Shape Memory Polymers.

    PubMed

    Ji, Shaobo; Fan, Fuqiang; Sun, Chenxing; Yu, Ying; Xu, Huaping

    2017-09-27

    Plasticity of thermoset polymers has been realized by introducing exchangeable bonds, and the plasticity is mostly triggered via heat or UV light. Visible light is a relatively mild trigger that has not been used to induce plasticity in polymer materials. Herein, thermoset polyurethanes (PUs) containing diselenide bonds are fabricated that possess visible light-induced plasticity along with shape memory behavior. A series of PUs with different diselenide bond contents were tested and their shape memory properties and plasticity varied. With a higher diselenide bond content, both shape memory and light-induced plasticity are achieved. By combining these two properties, reshaping the permanent shapes of the PUs is easier. Compared with heat or UV light, visible light has the advantage of spatial control. For instance, a pattern of visible light was introduced by a commercial projector to demonstrate facile reshaping of the materials. Because visible light can be introduced via various methods, PUs with visible light-induced plasticity have great potential applications.

  2. Inductively Heated Shape Memory Polymer for the Magnetic Actuation of Medical Devices

    SciTech Connect

    Buckley, P; Mckinley, G; Wilson, T; Small, W; Benett, W; Bearinger, J; McElfresh, M; Maitland, D

    2005-09-06

    Presently there is interest in making medical devices such as expandable stents and intravascular microactuators from shape memory polymer (SMP). One of the key challenges in realizing SMP medical devices is the implementation of a safe and effective method of thermally actuating various device geometries in vivo. A novel scheme of actuation by Curie-thermoregulated inductive heating is presented. Prototype medical devices made from SMP loaded with Nickel Zinc ferrite ferromagnetic particles were actuated in air by applying an alternating magnetic field to induce heating. Dynamic mechanical thermal analysis was performed on both the particle-loaded and neat SMP materials to assess the impact of the ferrite particles on the mechanical properties of the samples. Calorimetry was used to quantify the rate of heat generation as a function of particle size and volumetric loading of ferrite particles in the SMP. These tests demonstrated the feasibility of SMP actuation by inductive heating. Rapid and uniform heating was achieved in complex device geometries and particle loading up to 10% volume content did not interfere with the shape recovery of the SMP.

  3. Inductively heated shape memory polymer for the magnetic actuation of medical devices.

    PubMed

    Buckley, Patrick R; McKinley, Gareth H; Wilson, Thomas S; Small, Ward; Benett, William J; Bearinger, Jane P; McElfresh, Michael W; Maitland, Duncan J

    2006-10-01

    Presently, there is interest in making medical devices such as expandable stents and intravascular microactuators from shape memory polymer (SMP). One of the key challenges in realizing SMP medical devices is the implementation of a safe and effective method of thermally actuating various device geometries in vivo. A novel scheme of actuation by Curie-thermoregulated inductive heating is presented. Prototype medical devices made from SMP loaded with nickel zinc ferrite ferromagnetic particles were actuated in air by applying an alternating magnetic field to induce heating. Dynamic mechanical thermal analysis was performed on both the particle-loaded and neat SMP materials to assess the impact of the ferrite particles on the mechanical properties of the samples. Calorimetry was used to quantify the rate of heat generation as a function of particle size and volumetric loading of ferrite particles in the SMP. These tests demonstrated the feasibility of SMP actuation by inductive heating. Rapid and uniform heating was achieved in complex device geometries and particle loading up to 10% volume content did not interfere with the shape recovery of the SMP.

  4. Photonic Shape Memory Polymer with Stable Multiple Colors

    PubMed Central

    2017-01-01

    A photonic shape memory polymer film that shows large color response (∼155 nm) in a wide temperature range has been fabricated from a semi-interpenetrating network of a cholesteric polymer and poly(benzyl acrylate). The large color response is achieved by mechanical embossing of the photonic film above its broad glass transition temperature. The embossed film, as it recovers to its original shape on heating through the broad thermal transition, exhibits multiple structural colors ranging from blue to orange. The relaxation behavior of the embossed film can be fully described using a Kelvin–Voigt model, which reveals that the influence of temperature on the generation of colors is much stronger than that of time, thereby producing stable multiple colors. PMID:28840717

  5. Infrared thermographic analysis of shape memory polymer during cyclic loading

    NASA Astrophysics Data System (ADS)

    Staszczak, Maria; Pieczyska, Elżbieta A.; Maj, Michał; Kukla, Dominik; Tobushi, Hisaaki

    2016-12-01

    In this paper we present the effects of thermomechanical couplings occurring in polyurethane shape memory polymer subjected to cyclic tensile loadings conducted at various strain rates. Stress-strain characteristics were elaborated using a quasistatic testing machine, whereas the specimen temperature changes accompanying the deformation process were obtained with an infrared camera. We demonstrate a tight correlation between the mechanical and thermal results within the initial loading stage. The polymer thermomechanical behaviour in four subsequent loading-unloading cycles and the influence of the strain rate on the stress and the related temperature changes were also examined. In the range of elastic deformation the specimen temperature drops below the initial level due to thermoelastic effect whereas at the higher strains the temperature always increased, due to the dissipative deformation mechanisms. The difference in the characteristics of the specimen temperature has been applied to determine a limit of the polymer reversible deformation and analyzed for various strain rates. It was shown that at the higher strain rates higher values of the stress and temperature changes are obtained, which are related to higher values of the polymer yield points. During the cyclic loading a significant difference between the first and the second cycle was observed. The subsequent loading-unloading cycles demonstrated similar sharply shaped stress and temperature profiles and gradually decrease in values.

  6. Morphological and mechanical analysis of electrospun shape memory polymer fibers

    NASA Astrophysics Data System (ADS)

    Budun, Sinem; İşgören, Erkan; Erdem, Ramazan; Yüksek, Metin

    2016-09-01

    Shape memory block co-polymer Polyurethane (PU) fibers were fabricated by electrospinning technique. Four different solution concentrations (5 wt.%, 10 wt.%, 15 wt.% and 20 wt.%) were prepared by using Tetrahydrofuran (THF)/N,N-dimethylformamide (DMF) (50:50, v/v) as solvents, and three different voltages (30 kV, 35 kV and 38.9 kV) were determined for the electrospinning process. Solution properties were explored in terms of viscosity and electrical conductivity. It was observed that as the polymer concentration increased in the solution, the conductivity declined. Morphological characteristics of the obtained fibers were analyzed through Scanning Electron Microscopy (SEM) measurements. Findings indicated that fiber morphology varied especially with polymer concentration and applied voltage. Obtained fiber diameter ranged from 112 ± 34 nm to 2046 ± 654 nm, respectively. DSC analysis presented that chain orientation of the polymer increased after electrospinning process. Shape fixity and shape recovery calculations were realized. The best shape fixity value (92 ± 4%) was obtained for Y10K30 and the highest shape recovery measurement (130 ± 4%) was belonged to Y15K39. Mechanical properties of the electrospun webs were also investigated in both machine and transverse directions. Tensile and elongation values were also affected from fiber diameter distribution and morphological characteristics of the electrospun webs.

  7. Fiber laser micromachining of thin NiTi tubes for shape memory vascular stents

    NASA Astrophysics Data System (ADS)

    Liu, Lei; Li, Dong Bo; Tong, Yi Fei; Zhu, Yu Fu

    2016-07-01

    Nickel titanium (NiTi) alloy has widely been used in the vascular stent manufacturing due to its excellent properties. Neodymium-doped yttrium aluminum garnet (Nd:YAG) laser is commonly used for the preparation of metal vascular stents. Recently, fiber lasers have been used for stent profiling for better cutting quality. To investigate the cutting-kerf characters of NiTi vascular stents fabricated by fiber laser cutting, laser cutting experiments with thin NiTi tubes were conducted in this study, while NiTi sheets were used in other fiber laser cutting studies. Different with striation topography, new topographies such as layer topography and topography mixed with layers and striations were observed, and the underlying reason for new topographies was also discussed. Comparative research on different topographies was conducted through analyzing the surface roughness, kerf width, heat-affected zone (HAZ) and dross formation. Laser cutting process parameters have a comprehensive influence on the cutting quality; in this study, the process parameters' influences on the cutting quality were studied from the view of power density along the cutting direction. The present research provides a guideline for improving the cutting quality of NiTi vascular stents.

  8. Laser-activated shape memory polymer intravascular thrombectomy device

    NASA Astrophysics Data System (ADS)

    Small, Ward, IV; Wilson, Thomas S.; Benett, William J.; Loge, Jeffrey M.; Maitland, Duncan J.

    2005-10-01

    A blood clot (thrombus) that becomes lodged in the arterial network supplying the brain can cause an ischemic stroke, depriving the brain of oxygen and often resulting in permanent disability. As an alternative to conventional clot-dissolving drug treatment, we are developing an intravascular laser-activated therapeutic device using shape memory polymer (SMP) to mechanically retrieve the thrombus and restore blood flow to the brain. Thermal imaging and computer simulation were used to characterize the optical and photothermal behavior of the SMP microactuator. Deployment of the SMP device in an in vitro thrombotic vascular occlusion model demonstrated the clinical treatment concept.

  9. Outcomes of biodegradable polymer sirolimus-eluting PROLIM stent in patients with coronary artery disease. Results of 12-month follow-up of prospective registry.

    PubMed

    Roleder, Tomasz; Smolka, Grzegorz; Podolecka, Ewa; Chudek, Jolanta; Dworowy, Sebastian; Żelazowska, Katarzyna; Wojakowski, Wojciech; Ochała, Andrzej

    Data from clinical trials suggested that biodegradable-polymer-based drug-eluting stents (DES) might improve long-term clinical outcomes. PROLIM (Balton, Warsaw, Poland) DES is based on a stainless steel platform with a closed cell design releasing sirolimus from biodegradable copolymer (lactic and glycolic acid) in eight weeks. In the present study the safety and the efficacy of a PROLIM stent was assessed in patients with de novo coronary lesions in 12-month clinical follow-up. It was a single-centre, observational, prospective registry to assess the safety and efficacy of a PROLIM stent implantation in all consecutive patients with de novo coronary artery lesions treated with percutaneous coronary intervention (PCI). The primary study endpoint was a composite safety (cardiac death, non-fatal myocardial infarction), and the second study endpoint was the efficacy of PROLIM implantation-clinically driven target vessel revascularisation (TVR) assessed at 12-month follow-up. One hundred patients were enrolled into the study and 118 PROLIM stents were implanted. Thirty-two (32%) patients had diabetes, 46 (46%) patients were prior PCI, and 17 (17%) patients had coronary artery bypass grafting. 67% of stented lesions were complex ones (B2/C) and 17% were bifurcations. During the 12-month follow-up primary study endpoints occurred in five (5%) patients. Two (2%) cardiac deaths were reported and three (3%) TVRs were performed, of which one was related to in-PROLIM stent restenosis. PCI with biodegradable-polymer PROLIM DES seems to be safe and effective in 12-month follow-up. A larger trial is warranted to assess clinical outcomes post PROLIM stent implantation.

  10. Clinical outcomes of biodegradable polymer drug-eluting stents for percutaneous coronary intervention: an updated meta-analysis of randomized controlled trials.

    PubMed

    Kwong, Joey S W; Yu, Cheuk-Man

    2014-07-01

    Biodegradable polymer drug-eluting stents (DES) are innovative concepts in the era of percutaneous coronary intervention. We systematically reviewed the latest randomized evidence on the efficacy and safety of biodegradable polymer DES as compared to durable polymer DES. MEDLINE, Embase, and the Cochrane database were searched in August 2013 for eligible randomized controlled trials (RCTs) comparing biodegradable polymer DES with durable polymer DES. Clinical outcomes of interest were mortality, myocardial infarction (MI), target lesion revascularization (TLR), target vessel revascularization (TVR), and stent thrombosis. A total of 20 RCTs randomizing 20 021 participants were included, of whom 11 045 were allocated to biodegradable polymer DES and 8976 to durable polymer DES. Treatment of biodegradable polymer DES was not associated with a significant reduction of any of the clinical outcomes (all-cause mortality, odds ratio [OR]: 0.94, 95% confidence interval [CI]: 0.80 to 1.10, P = 0.42; cardiovascular mortality, OR: 0.97, 95% CI: 0.79 to 1.19, P = 0.74; MI, OR: 1.07, 95% CI: 0.91 to 1.26, P = 0.41; TLR, OR: 0.87, 95% CI: 0.69 to 1.08, P = 0.20; TVR, OR: 1.05, 95% CI: 0.85 to 1.28, P = 0.67; definite/probable stent thrombosis, OR: 0.80, 95% CI: 0.59 to 1.07, P = 0.14). Current randomized data indicate that clinical efficacy and safety profiles of biodegradable polymer DES are comparable to those of durable polymer DES. Findings from large-scale studies with rigorous methodology and long follow-up duration are needed.

  11. Characterization of Nonlinear Rate Dependent Response of Shape Memory Polymers

    NASA Technical Reports Server (NTRS)

    Volk, Brent; Lagoudas, Dimitris C.; Chen, Yi-Chao; Whitley, Karen S.

    2007-01-01

    Shape Memory Polymers (SMPs) are a class of polymers, which can undergo deformation in a flexible state at elevated temperatures, and when cooled below the glass transition temperature, while retaining their deformed shape, will enter and remain in a rigid state. Upon heating above the glass transition temperature, the shape memory polymer will return to its original, unaltered shape. SMPs have been reported to recover strains of over 400%. It is important to understand the stress and strain recovery behavior of SMPs to better develop constitutive models which predict material behavior. Initial modeling efforts did not account for large deformations beyond 25% strain. However, a model under current development is capable of describing large deformations of the material. This model considers the coexisting active (rubber) and frozen (glass) phases of the polymer, as well as the transitions between the material phases. The constitutive equations at the continuum level are established with internal state variables to describe the microstructural changes associated with the phase transitions. For small deformations, the model reduces to a linear model that agrees with those reported in the literature. Thermomechanical characterization is necessary for the development, calibration, and validation of a constitutive model. The experimental data reported in this paper will assist in model development by providing a better understanding of the stress and strain recovery behavior of the material. This paper presents the testing techniques used to characterize the thermomechanical material properties of a shape memory polymer (SMP) and also presents the resulting data. An innovative visual-photographic apparatus, known as a Vision Image Correlation (VIC) system was used to measure the strain. The details of this technique will also be presented in this paper. A series of tensile tests were performed on specimens such that strain levels of 10, 25, 50, and 100% were applied to

  12. Metallic Limus-Eluting Stents Abluminally Coated with Biodegradable Polymers: Angiographic and Clinical Comparison of a Novel Ultra-Thin Sirolimus Stent Versus Biolimus Stent in the DESTINY Randomized Trial.

    PubMed

    Lemos, Pedro A; Abizaid, Alexandre A C; Meireles, George C; Sarmento-Leite, Rogério; Prudente, Mauricio; Cantarelli, Marcelo; Dourado, Adriano D; Mariani, Jose; Perin, Marco A; Costantini, Costantino; Costa, Ricardo A; Costa, José Ribamar; Chamie, Daniel; Campos, Carlos A; Ribeiro, Expedito

    2015-12-01

    To evaluate the outcomes of patients treated with a new drug-eluting stent formulation with low doses of sirolimus, built in an ultra-thin-strut platform coated with biodegradable abluminal coating. This study is a randomized trial that tested the main hypothesis that the angiographic late lumen loss of the novel sirolimus-eluting stent is noninferior compared with commercially available biolimus-eluting stent. A final study population comprising 170 patients with one or two de novo lesions was randomized in the ratio 2:1 for sirolimus-eluting stent or biolimus-eluting stent, respectively. The primary endpoint was 9-month angiographic in-stent late lumen loss. Adverse clinical events were prospectively collected for 1 year. After 9 months, the novel sirolimus-eluting stent was shown noninferior compared with the biolimus stent for the primary endpoint (angiographic in-stent late lumen loss: 0.20 ± 0.29 mm vs. 0.15 ± 0.20 mm, respectively; P value for noninferiority <0.001). The 1-year incidence of death, myocardial infarction, repeat revascularization, and stent thrombosis remained low and not significantly different between the groups. The present randomized trial demonstrates that the tested novel sirolimus-eluting stent was angiographically noninferior in comparison with a last-generation biolimus-eluting stent. © 2015 John Wiley & Sons Ltd.

  13. Shape memory polymer hexachiral auxetic structures with tunable stiffness

    NASA Astrophysics Data System (ADS)

    Rossiter, Jonathan; Takashima, Kazuto; Scarpa, Fabrizio; Walters, Peter; Mukai, Toshiharu

    2014-04-01

    Planar auxetic structures have the potential to impact on a wide range of applications from deployable and morphing structures to space-filling composite and medical treatments. The ability to fabricate auxetics from smart materials greatly enhances this facility by building in controllable actuation and deployment. A smart auxetic device can be compressed and fixed into a storage state. When deployment is required the device can be appropriately stimulated and the stored elastic energy is released, resulting in a marked structural expansion. Instead of using a conventional external actuator to drive deployment the material is made to undergo phase transition where one stimulus (e.g. heat) initiates a mechanical response. Here we show how smart material auxetics can be realized using a thermally responsive shape memory polymer composites. We show how a shape memory polymer auxetic hexachiral structure can be tailored to provide a tunable stiffness response in its fully deployed state by varying the angle of inter-hub connections, and yet is still able to undergo thermally stimulated deployment.

  14. Multimaterial 4D Printing with Tailorable Shape Memory Polymers.

    PubMed

    Ge, Qi; Sakhaei, Amir Hosein; Lee, Howon; Dunn, Conner K; Fang, Nicholas X; Dunn, Martin L

    2016-08-08

    We present a new 4D printing approach that can create high resolution (up to a few microns), multimaterial shape memory polymer (SMP) architectures. The approach is based on high resolution projection microstereolithography (PμSL) and uses a family of photo-curable methacrylate based copolymer networks. We designed the constituents and compositions to exhibit desired thermomechanical behavior (including rubbery modulus, glass transition temperature and failure strain which is more than 300% and larger than any existing printable materials) to enable controlled shape memory behavior. We used a high resolution, high contrast digital micro display to ensure high resolution of photo-curing methacrylate based SMPs that requires higher exposure energy than more common acrylate based polymers. An automated material exchange process enables the manufacture of 3D composite architectures from multiple photo-curable SMPs. In order to understand the behavior of the 3D composite microarchitectures, we carry out high fidelity computational simulations of their complex nonlinear, time-dependent behavior and study important design considerations including local deformation, shape fixity and free recovery rate. Simulations are in good agreement with experiments for a series of single and multimaterial components and can be used to facilitate the design of SMP 3D structures.

  15. Multimaterial 4D Printing with Tailorable Shape Memory Polymers

    PubMed Central

    Ge, Qi; Sakhaei, Amir Hosein; Lee, Howon; Dunn, Conner K.; Fang, Nicholas X.; Dunn, Martin L.

    2016-01-01

    We present a new 4D printing approach that can create high resolution (up to a few microns), multimaterial shape memory polymer (SMP) architectures. The approach is based on high resolution projection microstereolithography (PμSL) and uses a family of photo-curable methacrylate based copolymer networks. We designed the constituents and compositions to exhibit desired thermomechanical behavior (including rubbery modulus, glass transition temperature and failure strain which is more than 300% and larger than any existing printable materials) to enable controlled shape memory behavior. We used a high resolution, high contrast digital micro display to ensure high resolution of photo-curing methacrylate based SMPs that requires higher exposure energy than more common acrylate based polymers. An automated material exchange process enables the manufacture of 3D composite architectures from multiple photo-curable SMPs. In order to understand the behavior of the 3D composite microarchitectures, we carry out high fidelity computational simulations of their complex nonlinear, time-dependent behavior and study important design considerations including local deformation, shape fixity and free recovery rate. Simulations are in good agreement with experiments for a series of single and multimaterial components and can be used to facilitate the design of SMP 3D structures. PMID:27499417

  16. Multimaterial 4D Printing with Tailorable Shape Memory Polymers

    NASA Astrophysics Data System (ADS)

    Ge, Qi; Sakhaei, Amir Hosein; Lee, Howon; Dunn, Conner K.; Fang, Nicholas X.; Dunn, Martin L.

    2016-08-01

    We present a new 4D printing approach that can create high resolution (up to a few microns), multimaterial shape memory polymer (SMP) architectures. The approach is based on high resolution projection microstereolithography (PμSL) and uses a family of photo-curable methacrylate based copolymer networks. We designed the constituents and compositions to exhibit desired thermomechanical behavior (including rubbery modulus, glass transition temperature and failure strain which is more than 300% and larger than any existing printable materials) to enable controlled shape memory behavior. We used a high resolution, high contrast digital micro display to ensure high resolution of photo-curing methacrylate based SMPs that requires higher exposure energy than more common acrylate based polymers. An automated material exchange process enables the manufacture of 3D composite architectures from multiple photo-curable SMPs. In order to understand the behavior of the 3D composite microarchitectures, we carry out high fidelity computational simulations of their complex nonlinear, time-dependent behavior and study important design considerations including local deformation, shape fixity and free recovery rate. Simulations are in good agreement with experiments for a series of single and multimaterial components and can be used to facilitate the design of SMP 3D structures.

  17. Variable stiffness property study on shape memory polymer composite tube

    NASA Astrophysics Data System (ADS)

    Chen, Yijin; Sun, Jian; Liu, Yanju; Leng, Jinsong

    2012-09-01

    As a typical smart material, shape memory polymers (SMPs) have the capability of variable stiffness in response to external stimuli, such as heat, electricity, magnetism and solvents. In this research, a shape memory polymer composite (SMPC) tube composed of multi-layered filament wound structures is investigated. The SMPC tube possesses considerable flexibility under high temperature and rigidity under low temperature. Significant changes in effective engineering modulus can be achieved through regulating the environment temperature. Based on the classical laminated-plate theory and Sun’s thick laminate analysis, a 3D theory method is used to study the effective engineering modulus and modulus ratio of the SMPC tube. The tensile test is conducted on the SMPC tube to verify the accuracy of the theoretical method. In addition, the effective engineering modulus and modulus ratio are discussed under different fiber-winding angles and fiber volume fractions of the SMPC tube. The presented analysis provides meaningful guidance to assist the design and manufacture of SMPC tubes in morphing skin applications.

  18. Post-Polymerization Crosslinked Polyurethane Shape-Memory Polymers.

    PubMed

    Hearon, K; Gall, K; Ware, T; Maitland, D J; Bearinger, J P; Wilson, T S

    2011-07-01

    Novel urethane shape-memory polymers (SMPs) of significant industrial relevance have been synthesized and characterized. Chemically crosslinked SMPs have traditionally been made in a one-step polymerization of monomers and crosslinking agents. However, these new post-polymerization crosslinked SMPs can be processed into complex shapes by thermoplastic manufacturing methods and later crosslinked by heat exposure or by electron beam irradiation. Several series of linear, olefinic urethane polymers were made from 2-butene-1,4-diol, other saturated diols, and various aliphatic diisocyanates. These thermoplastics were melt-processed into desired geometries and thermally crosslinked at 200°C or radiation crosslinked at 50 kGy. The SMPs were characterized by solvent swelling and extraction, differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), tensile testing, and qualitative shape-recovery analysis. Swelling and DMA results provided concrete evidence of chemical crosslinking, and further characterization revealed that the urethanes had outstanding mechanical properties. Key properties include tailorable transitions between 25 and 80°C, tailorable rubbery moduli between 0.2 and 4.2 MPa, recoverable strains approaching 100%, failure strains of over 500% at T(g), and qualitative shape-recovery times of less than 12 seconds at body temperature (37°C). Because of its outstanding thermo-mechanical properties, one polyurethane was selected for implementation in the design of a complex medical device. These post-polymerization crosslinked urethane SMPs are an industrially relevant class of highly processable shape-memory materials.

  19. Post-Polymerization Crosslinked Polyurethane Shape-Memory Polymers

    PubMed Central

    Hearon, K.; Gall, K.; Ware, T.; Maitland, D. J.; Bearinger, J. P.; Wilson, T. S.

    2011-01-01

    Novel urethane shape-memory polymers (SMPs) of significant industrial relevance have been synthesized and characterized. Chemically crosslinked SMPs have traditionally been made in a one-step polymerization of monomers and crosslinking agents. However, these new post-polymerization crosslinked SMPs can be processed into complex shapes by thermoplastic manufacturing methods and later crosslinked by heat exposure or by electron beam irradiation. Several series of linear, olefinic urethane polymers were made from 2-butene-1,4-diol, other saturated diols, and various aliphatic diisocyanates. These thermoplastics were melt-processed into desired geometries and thermally crosslinked at 200°C or radiation crosslinked at 50 kGy. The SMPs were characterized by solvent swelling and extraction, differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), tensile testing, and qualitative shape-recovery analysis. Swelling and DMA results provided concrete evidence of chemical crosslinking, and further characterization revealed that the urethanes had outstanding mechanical properties. Key properties include tailorable transitions between 25 and 80°C, tailorable rubbery moduli between 0.2 and 4.2 MPa, recoverable strains approaching 100%, failure strains of over 500% at Tg, and qualitative shape-recovery times of less than 12 seconds at body temperature (37°C). Because of its outstanding thermo-mechanical properties, one polyurethane was selected for implementation in the design of a complex medical device. These post-polymerization crosslinked urethane SMPs are an industrially relevant class of highly processable shape-memory materials. PMID:21572577

  20. Thermally driven microfluidic pumping via reversible shape memory polymers

    NASA Astrophysics Data System (ADS)

    Robertson, J. M.; Rodriguez, R. X.; Holmes, L. R., Jr.; Mather, P. T.; Wetzel, E. D.

    2016-08-01

    The need exists for autonomous microfluidic pumping systems that utilize environmental cues to transport fluid within a network of channels for such purposes as heat distribution, self-healing, or optical reconfiguration. Here, we report on reversible thermally driven microfluidic pumping enabled by two-way shape memory polymers. After developing a suitable shape memory polymer (SMP) through variation in the crosslink density, thin and flexible microfluidic devices were constructed by lamination of plastic films with channels defined by laser-cutting of double-sided adhesive film. SMP blisters integrated into the devices provide thermally driven pumping, while opposing elastic blisters are used to generate backpressure for reversible operation. Thermal cycling of the device was found to drive reversible fluid flow: upon heating to 60 °C, the SMP rapidly contracted to fill the surface channels with a transparent fluid, and upon cooling to 8 °C the flow reversed and the channel re-filled with black ink. Combined with a metallized backing layer, this device results in refection of incident light at high temperatures and absorption of light (at the portions covered with channels) at low temperatures. We discuss power-free, autonomous applications ranging from thermal regulation of structures to thermal indication via color change.

  1. Shape memory-based tunable resistivity of polymer composites

    NASA Astrophysics Data System (ADS)

    Luo, Hongsheng; Zhou, Xingdong; Ma, Yuanyuan; Yi, Guobin; Cheng, Xiaoling; Zhu, Yong; Zu, Xihong; Zhang, Nanjun; Huang, Binghao; Yu, Lifang

    2016-02-01

    A conductive composite in bi-layer structure was fabricated by embedding hybrid nanofillers, namely carbon nanotubes (CNTs) and silver nanoparticles (AgNPs), into a shape memory polyurethane (SMPU). The CNT/AgNP-SMPU composites exhibited a novel tunable conductivity which could be facially tailored in wide range via the compositions or a specifically designed thermo-mechanical shape memory programming. The morphologies of the conductive fillers and the composites were investigated by scanning electron microscope (SEM). The mechanical and thermal measurements were performed by tensile tests and differential scanning calorimetry (DSC). By virtue of a specifically explored shape memory programming, the composites were stretched and fixed into different temporary states. The electrical resistivity (Rs) varied accordingly, which was able to be stabilized along with the shape fixing. Theoretical prediction based upon the tunneling model was performed. The Rs-strain curves of the composites with different compositions were well fitted. Furthermore, the relative resistivity and the Gauge factor along with the elongation were calculated. The influence of the compositions on the strain-dependent Rs was disclosed. The findings provided a new avenue to tailor the conductivity of the polymeric nano-composites by combining the composition method and a thermo-mechanical programming, which may greatly benefit the application of intelligent polymers in flexible electronics and sensors fields.

  2. Safety and efficacy of biolimus-eluting stent with biodegradable polymer: insights from EINSTEIN (Evaluation of Next-generation drug-eluting STEnt IN patients with coronary artery disease) Registry

    PubMed Central

    de Souza, Cristiano Freitas; Mouallem, Anwar Mohamed El; de Brito, Fábio Sândoli; Abizaid, Alexandre Antônio Cunha; Almeida, Breno Oliveira; Almeida, Amanda Gonçalves; Nascimento, Teresa Cristina Dias Cunha; Perin, Marco Antonio; Caixeta, Adriano

    2013-01-01

    ABSTRACT Objective: To evaluate the incidence of major adverse cardiac events (cardiac death, or acute myocardial infarct, or target vessel revascularization) at one year in “real world” patients. Methods: The EINSTEIN registry is an observational, prospective, single center study that consecutively included 103 patients (152 lesions) treated with the Biomatrix™ stent, a biolimus A9-eluting stent with biodegradable polymer. Results: The mean age was 65.0±12.4 years; male gender represented 83.5% of the patients; and 37.9% of them were diabetic. At one-year, major adverse cardiac events occurred in 11.7% of the patients, including 2.9% of cardiac death, 4.9% of with non ST- segment elevation acute myocardial infarction, and 3.9% of target vessel revascularization. Stent thrombosis occurred in only 1% (1 patient) at one-yearfollow-up. Conclusion: The present Registry suggests that new generation biolimus A9 drug-eluting stents are safe and effective in a “real world”, all-comers patients, showing low rates of major cardiac adverse events on long-term follow-up. PMID:24136763

  3. The real world experience of the biodegradable polymer-coated sirolimus-eluting coronary stent system: Results From an "All-Comers" Clinical Experience.

    PubMed

    Rajasekhar, D; Vanajakshamma, V; Shashank, C; Srinivasakumar, M L; Sivasankara, C

    2016-09-01

    This INDOLIMUS Registry sought to evaluate the safety and efficacy of the biodegradable polymer coated Indolimus(®) sirolimus-eluting coronary stent for the treatment of coronary artery disease across a wide range of patients treated in routine clinical practice, including those with high-risk characteristics and complex lesions. First-generation drug-eluting stents utilize nonbiodegradable polymeric coatings, whose persistent presence in the arterial wall may negatively affect long-term outcomes. It has been hypothesized that persistent presence of polymer may compromise the safety of drug-eluting stents, and that therefore biodegradable polymer coatings might reduce late adverse events in an unselected patient population. All 530 consecutive unselected patients (415 males and 115 females) included who underwent percutaneous coronary intervention at the Sri Venkateswara Institute of Medical Sciences, Tirupati, India between August 2012 and March 2013, with an in-hospital, at 30-days and at 6-months follow-up. Retrospective analysis of those data had been done. A total of 617 lesions were treated in 530 enrolled patients (mean age 54.9 ± 10.8 years) with average stent length of 18.8 ± 6.0 mm. An average of 1.18 stents was implanted per patient. The patients' characteristics are noted as having 169 (31.9%) patients of diabetics and 215 (40.6%) hypertension. Smoking, alcoholism and tobacco chewing were found in 273 (51.5%), 130 (24.5%) and 17 (3.2%), respectively. The indications for intervention were unstable angina in 77 (14.5%) and previous myocardial infarction in 56 (10.6%) of the patients. Lesions were of type B2 in 264 (42.7%) and type C in 127 (20.6%). Stent delivery was successful in all cases and in-hospital, 30-days and 6-months follow-up of all 530 patients was obtained. The incidence of any major adverse cardiac events at in-hospital, at 30-days and at 6-months were 5 (0.94%), 8 (1.52%), and 18 (3.40%), respectively. Long term follow-up of

  4. Particulate Release From Nanoparticle-Loaded Shape Memory Polymer Foams.

    PubMed

    Nathan, Adam L; Fletcher, Grace K; Monroe, Mary Beth B; Hwang, Wonjun; Herting, Scott M; Hasan, Sayyeda M; Keller, Brandis K; Maitland, Duncan J

    2017-03-01

    Highly porous, open-celled shape memory polymer (SMP) foams are being developed for a number of vascular occlusion devices. Applications include abdominal aortic and neurovascular aneurysm or peripheral vascular occlusion. A major concern with implanting these high surface area materials in the vasculature is the potential to generate unacceptable particulate burden, in terms of number, size, and composition. This study demonstrates that particulate numbers and sizes in SMP foams are in compliance with limits stated by the most relevant standard and guidance documents. Particulates were quantified in SMP foams as made, postreticulation, and after incorporating nanoparticles intended to increase material toughness and improve radiopacity. When concentrated particulate treatments were administered to fibroblasts, they exhibited high cell viability (100%). These results demonstrate that the SMP foams do not induce an unacceptable level of risk to potential vascular occlusion devices due to particulate generation.

  5. Shape memory polymers: three-dimensional isotropic modeling

    NASA Astrophysics Data System (ADS)

    Balogun, Olaniyi; Mo, Changki

    2014-04-01

    This paper presents a comprehensive three-dimensional isotropic numerical simulation for a thermo-mechanical constitutive model of shape memory polymers (SMPs). In order to predict the thermo-mechanical behavior of SMPs, a one-dimensional rheological thermo-mechanical constitutive model is adopted, translated into a three-dimensional form and a time discrete form of the three-dimensional model is then presented. Numerical simulation of this model was developed using the UMAT subroutine capabilities of the finite element software ABAQUS. Evolution of the analysis was conducted by making use of the backward difference scheme, which was applied to all quantities within the model, including the material properties. A comparison of the numerical simulation results was carried out with the available experimental data. Numerical simulation results clearly exhibit the thermo-mechanical properties of the material which include shape fixity, shape recovery, and recovery stress. Finally, a prediction for the transverse and shear directions of the material is presented.

  6. A Kirigami shape memory polymer honeycomb concept for deployment

    NASA Astrophysics Data System (ADS)

    Neville, Robin M.; Chen, Jianguo; Guo, Xiaogang; Zhang, Fenghua; Wang, Wenxin; Dobah, Yousef; Scarpa, Fabrizio; Leng, Jinsong; Peng, Hua-Xin

    2017-05-01

    We present a shape memory polymer (SMP) honeycomb with tuneable and shape morphing mechanical characteristics. Kirigami (Origami with cutting allowed) techniques have been used to design and manufacture the honeycomb. The cellular structure described in this work has styrene SMP hinges that create the shape change and the deployment actuation. To create a large volumetric deployment, the Kirigami open honeycomb configuration has been designed by setting an initial three-dimensional re-entrant auxetic (negative Poisson’s ratio) configuration, while the final honeycomb shape assume a convex (positive Poisson’s ratio) layout. A model was developed to predict the shape change of the structure, and compared to experimental results from a demonstrator honeycomb deployment test.

  7. Advancing reversible shape memory by tuning the polymer network architecture

    DOE PAGES

    Li, Qiaoxi; Zhou, Jing; Vatankhah-Varnoosfaderani, Mohammad; ...

    2016-02-02

    Because of counteraction of a chemical network and a crystalline scaffold, semicrystalline polymer networks exhibit a peculiar behavior—reversible shape memory (RSM), which occurs naturally without applying any external force and particular structural design. There are three RSM properties: (i) range of reversible strain, (ii) rate of strain recovery, and (iii) decay of reversibility with time, which can be improved by tuning the architecture of the polymer network. Different types of poly(octylene adipate) networks were synthesized, allowing for control of cross-link density and network topology, including randomly cross-linked network by free-radical polymerization, thiol–ene clicked network with enhanced mesh uniformity, and loosemore » network with deliberately incorporated dangling chains. It is shown that the RSM properties are controlled by average cross-link density and crystal size, whereas topology of a network greatly affects its extensibility. In conclusion, we have achieved 80% maximum reversible range, 15% minimal decrease in reversibility, and fast strain recovery rate up to 0.05 K–1, i.e., ca. 5% per 10 s at a cooling rate of 5 K/min.« less

  8. Advancing reversible shape memory by tuning the polymer network architecture

    SciTech Connect

    Li, Qiaoxi; Zhou, Jing; Vatankhah-Varnoosfaderani, Mohammad; Nykypanchuk, Dmytro; Gang, Oleg; Sheiko, Sergei S.

    2016-02-02

    Because of counteraction of a chemical network and a crystalline scaffold, semicrystalline polymer networks exhibit a peculiar behavior—reversible shape memory (RSM), which occurs naturally without applying any external force and particular structural design. There are three RSM properties: (i) range of reversible strain, (ii) rate of strain recovery, and (iii) decay of reversibility with time, which can be improved by tuning the architecture of the polymer network. Different types of poly(octylene adipate) networks were synthesized, allowing for control of cross-link density and network topology, including randomly cross-linked network by free-radical polymerization, thiol–ene clicked network with enhanced mesh uniformity, and loose network with deliberately incorporated dangling chains. It is shown that the RSM properties are controlled by average cross-link density and crystal size, whereas topology of a network greatly affects its extensibility. In conclusion, we have achieved 80% maximum reversible range, 15% minimal decrease in reversibility, and fast strain recovery rate up to 0.05 K–1, i.e., ca. 5% per 10 s at a cooling rate of 5 K/min.

  9. Smart medical stocking using memory polymer for chronic venous disorders.

    PubMed

    Kumar, Bipin; Hu, Jinlian; Pan, Ning

    2016-01-01

    Proper level of pressure or compression generated by medical stocking or hosiery is the key element for successful treatment or management of chronic venous disorders such as oedema, leg ulcers, etc. However achieving the recommended compression level and, more importantly, sustaining it using stockings has been a major challenge to the health practitioners supervising the treatment. This work aims to investigate and design a smart compression stocking using shape-memory polymer that allows externally controlling the pressure level in the wrapped position on the leg. Based on thermodynamical rubber theories, we first derived several criteria that have to be satisfied simultaneously in order to achieve the controlled pressure adjustment using external heat stimuli. We then presented a case where such a stocking is developed using a blend yarn consists of selected shape-memory polyurethane and nylon filaments. Extensive experimental work has also been conducted to demonstrate the feasibility and explore the influencing factors involved. Copyright © 2015 Elsevier Ltd. All rights reserved.

  10. On a novel self-regulating shape memory polymer composite

    NASA Astrophysics Data System (ADS)

    Gao, Fei; Son, Seyul; Park, Kyungmook; Biggs, David; Andrews, Courtney; Mockensturm, Eric M.; Goulbourne, Nakhiah C.

    2011-04-01

    Polyurethane shape memory polymers (PU-SMPs) are active materials that can be transformed into complex shapes with the ability to recover their original shape even after undergoing large deformations. Because of their light weight, large recoverability, low cost, and high compliance, SMPs can be potentially employed as actuators, MEMS devices, temperature sensors, and damping elements to name a few. One of the key challenges in implementing SMPs is the response time which is limited by the method of heating and cooling and the material. Unlike shape memory alloys, SMPs can be activated by multiple stimuli including lasers, resistive heating, electric fields, and magnetic fields. While these methods may provide an efficient way of heating the SMP, they rely on the slow process of passive conduction for cooling. In this paper, a self regulating SMP (SR-SMP) composite is introduced, whereby a novel heating and cooling system consisting of embedded silica capillary tubes in the SMP (DiAPLEX® MP4510: SMP Technologies, Inc.) has been developed. The tubes are used to pump hot/cold fluid through the SMP membrane and hence provide a local temperature source. In order to show the effectiveness and efficiency of the mechanism, the thermomechanical response of the SR-SMP is compared experimentally to a SMP with "conventional" i.e. global heating and cooling mechanisms. It is shown that the SR-SMP has a faster thermomechanical response. It has been demonstrated previously that soft SMPs can be controlled by an electric field while in the rubbery phase, thus taking advantage of the Maxwell stress or electrostatic stress effect. Thermomechanical characterization of PU-SMPs is described for different weight percentages of resin (Diphenylmethane-4, 4'-diisocyanate) and hardener (1,4-Butanediol). Varying the percent hardener reduced the effective cross-link density of the polymer and hence the thermomechanical properties. The electromechanical response of pure SMP and SR-SMP is

  11. A clinical evaluation of the ProNOVA XR polymer-free sirolimus eluting coronary stent system in the treatment of patients with de novo coronary artery lesions (EURONOVA XR I study)☆

    PubMed Central

    Legutko, Jacek; Zasada, Wojciech; Kałuża, Grzegorz L.; Heba, Grzegorz; Rzeszutko, Lukasz; Jakala, Jacek; Dragan, Jacek; Klecha, Artur; Giszterowicz, Dawid; Dobrowolski, Wojciech; Partyka, Łukasz; Jayaraman, Swaminathan; Dudek, Dariusz

    2013-01-01

    Aims Evaluation of safety and efficacy of ProNOVA XR, a new generation of polymer-free sirolimus eluting stents (SES), utilizing a pharmaceutical excipient for timed release of sirolimus from the XR platform. Methods and results Safety and efficacy of ProNOVA XR coronary stent system was examined in EURONOVA prospective, single arm, multi-center registry of 50 patients with de novo native coronary lesions up to 28 mm in length in arteries between 2.25 and 4 mm. At 6-month, in-stent late lumen loss by QCA was 0.45 ± 0.41 mm and in-stent neointimal volume obstruction in the IVUS sub-study was 14 ± 11%. One-year clinical follow-up revealed a favorable safety profile, with 2% of in-hospital MACE and 6.4% of MACE from hospital discharge up to 12 months (including 1 cardiac death >30 days after stent implantation and 2 TLRs). According to the ARC definition, there was no definite or probable stent thrombosis and 1 possible stent thrombosis (2%) up to 12 months of clinical follow-up. Conclusions In this preliminary evaluation, ProNOVA XR polymer-free sirolimus eluting stent system appeared safe with an early promise of adequate effectiveness in the treatment of de novo coronary lesions in up to 12 months of clinical, angiographic and IVUS follow-up. PMID:23992999

  12. Incidence of adverse cardiac events 5 years after polymer-free sirolimus eluting stent implantation: Results from the prospective Bad Berka Yukon Choice™ registry.

    PubMed

    Ohlow, Marc-Alexander; von Korn, Hubertus; Gunkel, Oliver; Farah, Ahmed; Fuhrmann, Joerg T; Lauer, Bernward

    2014-12-01

    Drug-eluting stents (DES) constitute a major achievement in preventing re-stenosis, concerns remain regarding the increased inflammatory responses associated with the polymers used. This analysis focuses on outcomes in patients receiving the polymer-free sirolimus-eluting stent system YUKON-Choice (Yukon-DES, Translumina, Germany). From 01/2006-09/2008 all patients receiving Yukon-DES (≥2.5 mm diameter) were prospectively enrolled in our registry. The primary endpoint was long-term major adverse cardiac events (MACE). 701 patients were included in our registry. Mean age was 65.7 ± 10 years (73% male gender, 35.5% diabetes, and 32.2% acute coronary syndrome). 76% of the lesions were of Type B2/C. Lesion length was 24.6 ± 5.2 mm and mean stent diameter was 2.8 ± 0.4 mm. A total of 511 pts (72%) underwent 6-months angiographic follow-up, target vessel revascularization was noted in 23.5%. At 5 years clinical outcomes were: cardiac death 5.8%; myocardial infarction 3.4%; and TVR 24.6%. The incidence of MACE differed significantly between "on-label" and "off-label" indications (14.8% vs. 40.8% MACE; P < 0.001). Incidence of definitive/probable stent thrombosis (ST) was 1.14% (8/701); very late (>1 year) ST occurred in 0.29%. Our data suggests that the implantation of the sirolimus-coated polymer-free YUKON-DES is safe and feasible with a very low incidence of ST in this real world patient cohort with high percentage of diabetes and small vessels. © 2013 Wiley Periodicals, Inc.

  13. A new generation of biodegradable polymer-coated sirolimus-eluting stents for the treatment of coronary artery disease: final 5-year clinical outcomes from the CREATE study.

    PubMed

    Han, Ya-Ling; Zhang, Lei; Yang, Li-Xia; Liu, Hui-Liang; Qu, Peng; Li, Wei-Min; Jiang, Tie-Min; Li, Shu-Mei; Jing, Quan-Min; Zhang, Quan-Yu; Xu, Bo; Li, Yi; Gao, Run-Lin

    2012-11-22

    The aim of the present study was to evaluate the five-year safety and efficacy of a biodegradable polymer-coated sirolimus-eluting stent with six months dual antiplatelet therapy in daily practice. Two thousand and seventy-seven daily practice patients, exclusively treated with biodegradable polymer-coated sirolimus-eluting stents (EXCEL; JW Medical Systems, Weihai, China), were prospectively enrolled in the multicentre CREATE study. Clinical follow-up was completed in 1,982 patients (95.4%) at five-year follow-up. The rates of cardiac death, non-fatal myocardial infarction (MI), target lesion revascularisation and overall major adverse cardiac events (MACE) at five-year follow-up were 3.0%, 1.5%, 3.7% and 7.4%, respectively. The rates of definite or probable stent thrombosis (ST) at five years and definite ST from one to five years were 1.1% and 0.3%, respectively. Heart failure (hazard ratio [HR]: 3.324, 95% confidence interval [CI]: 1.729-6.391, p<0.001) and prior MI (HR: 2.664, 95% CI: 1.358-5.227, p=0.004) were independent predictors of ST. Landmark analysis of a propensity score matched patient cohort showed that patients with or without clopidogrel treatment after six months had similar clinical outcomes. The present study demonstrates satisfactory and sustained five-year clinical safety and efficacy profiles as evidenced by the low rates of MACE and ST for the EXCEL, a biodegradable polymer-based sirolimus-eluting stent, when patients were treated with six months dual antiplatelet therapy in daily practice.

  14. Extraluminal distraction enterogenesis using shape-memory polymer.

    PubMed

    Fisher, Jeremy G; Sparks, Eric A; Khan, Faraz A; Dionigi, Beatrice; Wu, Hao; Brazzo, Joseph; Fauza, Dario; Modi, Biren; Safranski, David L; Jaksic, Tom

    2015-06-01

    Although a few techniques for lengthening intestine by mechanical stretch have been described, they are relatively complex, and the majority involve placement of an intraluminal device. Ideally, techniques applicable to humans would be easy to perform and extraluminal to avoid the potential for mucosal injury. This study of distraction enterogenesis used an extraluminal, radially self-expanding shape-memory polymer cylinder and a simple operative approach to both elongate intestine and grow new tissue. Young Sprague Dawley rats (250-350 g) underwent Roux-en-Y isolation of a small intestinal limb and were divided in three groups: no further manipulation (Control 1, C1); placement of a nonexpanding device (Control 2, C2); or placement of a radially expanding device by the limb (Experimental, Exp). For C2 and Exp animals, the blind end of the limb was wrapped around the radially expanding cylindrical device with the limb-end sutured back to the limb-side. Bowel length was measured at operation and at necropsy (14 days) both in-situ and ex-vivo under standard tension (6g weight). Change in length is shown as mean ± standard deviation. A blinded gastrointestinal pathologist reviewed histology and recorded multiple measures of intestinal adaptation. The DNA to protein ratio was quantified as a surrogate for cellular proliferation. Changes in length, histologic measures, and DNA:protein were compared using analysis of variance, with significance set at P<0.05. The length of the Roux limb in situ increased significantly in Exp animals (n=8, 29.0 ± 5.8mm) compared with C1 animals (n=5, -11.2 ± 9.0mm, P<0.01). The length of the Roux limb ex vivo under standard tension increased in the Exp group (25.8 ± 4.2mm) compared with the C2 group (n=6, -4.3 ± 6.0, P<0.01). There were no differences in histologic measures of bowel adaptation between the groups, namely villous height and width, crypt depth, crypt density, and crypt fission rate (all P ≥ 0.08). Muscularis mucosal

  15. Optimal stent design for drug delivery.

    PubMed

    Rogers, Campbell D K

    2004-01-01

    The efficacy and safety of drug-eluting coronary stents might differ depending on the pharmacologic agents and stent delivery systems used. Recent research has focused on the various constituents of drug-delivery stents, including the stent backbone, materials used as drug-delivery vehicles, and the physicochemical properties of the pharmacotherapeutic agents themselves. Metal stents coated with an outer layer of polymer (bioabsorbable or non-bioabsorbable) can be drug-loaded, thus providing more controlled and sustained drug delivery and allowing more optimal drug-tissue interactions. Among the next generation of drug-eluting stents will be a stent that uses the non-bioabsorbable polymer phosphorylcholine to release the sirolimus analogue ABT-578; another stent will use a highly deliverable cobalt-chromium metal alloy stent platform and, for the first time, a bioabsorbable polymeric coating (thin-film polylactic acid) for drug encapsulation and release.

  16. Surface modification of a polyhedral oligomeric silsesquioxane poly(carbonate-urea) urethane (POSS-PCU) nanocomposite polymer as a stent coating for enhanced capture of endothelial progenitor cells

    PubMed Central

    Tan, Aaron; Farhatnia, Yasmin; Goh, Debbie; G, Natasha; de Mel, Achala; Lim, Jing; Teoh, Swee-Hin; Malkovskiy, Andrey V; Chawla, Reema; Rajadas, Jayakumar; Cousins, Brian G; Hamblin, Michael R; Alavijeh, Mohammad S; Seifalian, Alexander M

    2013-01-01

    An unmet need exists for the development of next-generation multifunctional nanocomposite materials for biomedical applications, particularly in the field of cardiovascular regenerative biology. Herein, we describe the preparation and characterization of a novel polyhedral oligomeric silsesquioxane poly(carbonate-urea) urethane (POSS-PCU) nanocomposite polymer with covalently attached anti-CD34 antibodies to enhance capture of circulating endothelial progenitor cells (EPC). This material may be used as a new coating for bare metal stents used after balloon angioplasty to improve re-endothelialization. Biophysical characterization techniques were used to assess POSS-PCU and its subsequent functionalization with anti-CD34 antibodies. Results indicated successful covalent attachment of anti-CD34 antibodies on the surface of POSS-PCU leading to an increased propensity for EPC capture, whilst maintaining in vitro biocompatibility and hemocompatibility. POSS-PCU has already been used in 3 first-in-man studies, as a bypass graft, lacrimal duct and a bioartificial trachea. We therefore postulate that its superior biocompatibility and unique biophysical properties would render it an ideal candidate for coating medical devices, with stents as a prime example. Taken together, anti-CD34 functionalized POSS-PCU could form the basis of a nano-inspired polymer platform for the next generation stent coatings. PMID:24706135

  17. Biodegradable polymer drug-eluting stents reduce the risk of stent thrombosis at 4 years in patients undergoing percutaneous coronary intervention: a pooled analysis of individual patient data from the ISAR-TEST 3, ISAR-TEST 4, and LEADERS randomized trials.

    PubMed

    Stefanini, Giulio G; Byrne, Robert A; Serruys, Patrick W; de Waha, Antoinette; Meier, Bernhard; Massberg, Steffen; Jüni, Peter; Schömig, Albert; Windecker, Stephan; Kastrati, Adnan

    2012-05-01

    The efficacy of durable polymer drug-eluting stents (DES) is delivered at the expense of delayed healing of the stented vessel. Biodegradable polymer DES aim to avoid this shortcoming and may potentially improve long-term clinical outcomes, with benefit expected to accrue over time. We sought to compare long-term outcomes in patients treated with biodegradable polymer DES vs. durable polymer sirolimus-eluting stents (SES). We pooled individual patient data from three large-scale multicentre randomized clinical trials (ISAR-TEST 3, ISAR-TEST 4, and LEADERS) comparing biodegradable polymer DES with durable polymer SES and assessed clinical outcomes during follow-up through 4 years. The efficacy endpoint of interest was target lesion revascularization and the safety endpoint of interest was definite stent thrombosis. Out of 4062 patients included in the present analysis, 2358 were randomly assigned to treatment with biodegradable polymer DES (sirolimus-eluting, n= 1501; biolimus-eluting, n= 857) and 1704 patients to durable polymer SES. No heterogeneity across the trials was observed in analyses of the primary and secondary endpoints. At 4 years, the risk of target lesion revascularization was significantly lower among patients treated with biodegradable polymer DES vs. durable polymer SES (hazard ratio 0.82, 95% CI 0.68-0.98, P= 0.029). In addition, the risk of stent thrombosis was significantly reduced with biodegradable polymer DES vs. durable polymer SES (hazard ratio 0.56, 95% CI 0.35-0.90, P= 0.015), driven by a lower risk of very late stent thrombosis (hazard ratio 0.22, 95% CI 0.08-0.61, P= 0.004). In keeping with this, in landmark analysis between 1 and 4 years, the incidence of myocardial infarction was lower for patients treated with biodegradable polymer DES vs. durable polymer SES (hazard ratio 0.59, 95% CI 0.73-0.95, P= 0.031). Biodegradable polymer DES improve safety and efficacy compared with durable polymer SES during long-term follow-up to 4 years.

  18. Highly flexible silver nanowire electrodes for shape-memory polymer light-emitting diodes.

    PubMed

    Yu, Zhibin; Zhang, Qingwu; Li, Lu; Chen, Qi; Niu, Xiaofan; Liu, Jun; Pei, Qibing

    2011-02-01

    Shape-memory polymer light-emitting diodes (PLEDs) using a new silver nanowire/polymer electrode are reported. The electrode can be stretched by up to 16% with only a small increase in sheet resistance. Large deformation shape change and recovery of the PLEDs to various bistable curvatures result in minimal loss of electroluminescence performance.

  19. Self-Deploying Trusses Containing Shape-Memory Polymers

    NASA Technical Reports Server (NTRS)

    Schueler, Robert M.

    2008-01-01

    Composite truss structures are being developed that can be compacted for stowage and later deploy themselves to full size and shape. In the target applications, these smart structures will precisely self-deploy and support a large, lightweight space-based antenna. Self-deploying trusses offer a simple, light, and affordable alternative to articulated mechanisms or inflatable structures. The trusses may also be useful in such terrestrial applications as variable-geometry aircraft components or shelters that can be compacted, transported, and deployed quickly in hostile environments. The truss technology uses high-performance shape-memory-polymer (SMP) thermoset resin reinforced with fibers to form a helical composite structure. At normal operating temperatures, the truss material has the structural properties of a conventional composite. This enables truss designs with required torsion, bending, and compression stiffness. However, when heated to its designed glass transition temperature (Tg), the SMP matrix acquires the flexibility of an elastomer. In this state, the truss can be compressed telescopically to a configuration encompassing a fraction of its original volume. When cooled below Tg, the SMP reverts to a rigid state and holds the truss in the stowed configuration without external constraint. Heating the materials above Tg activates truss deployment as the composite material releases strain energy, driving the truss to its original memorized configuration without the need for further actuation. Laboratory prototype trusses have demonstrated repeatable self-deployment cycles following linear compaction exceeding an 11:1 ratio (see figure).

  20. A Processable Shape Memory Polymer System for Biomedical Applications.

    PubMed

    Hearon, Keith; Wierzbicki, Mark A; Nash, Landon D; Landsman, Todd L; Laramy, Christine; Lonnecker, Alexander T; Gibbons, Michael C; Ur, Sarah; Cardinal, Kristen O; Wilson, Thomas S; Wooley, Karen L; Maitland, Duncan J

    2015-06-24

    Polyurethane shape memory polymers (SMPs) with tunable thermomechanical properties and advanced processing capabilities are synthesized, characterized, and implemented in the design of a microactuator medical device prototype. The ability to manipulate glass transition temperature (Tg ) and crosslink density in low-molecular weight aliphatic thermoplastic polyurethane SMPs is demonstrated using a synthetic approach that employs UV catalyzed thiol-ene "click" reactions to achieve postpolymerization crosslinking. Polyurethanes containing varying C=C functionalization are synthesized, solution blended with polythiol crosslinking agents and photoinitiator and subjected to UV irradiation, and the effects of number of synthetic parameters on crosslink density are reported. Thermomechanical properties are highly tunable, including glass transitions tailorable between 30 and 105 °C and rubbery moduli tailorable between 0.4 and 20 MPa. This new SMP system exhibits high toughness for many formulations, especially in the case of low crosslink density materials, for which toughness exceeds 90 MJ m(-3) at select straining temperatures. To demonstrate the advanced processing capability and synthetic versatility of this new SMP system, a laser-actuated SMP microgripper device for minimally invasive delivery of endovascular devices is fabricated, shown to exhibit an average gripping force of 1.43 ± 0.37 N and successfully deployed in an in vitro experimental setup under simulated physiological conditions. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Virtual Treatment of Basilar Aneurysms Using Shape Memory Polymer Foam

    PubMed Central

    Ortega, J.M.; Hartman, J.; Rodriguez, J.N.; Maitland, D.J.

    2013-01-01

    Numerical simulations are performed on patient-specific basilar aneurysms that are treated with shape memory polymer (SMP) foam. In order to assess the post-treatment hemodynamics, two modeling approaches are employed. In the first, the foam geometry is obtained from a micro-CT scan and the pulsatile blood flow within the foam is simulated for both Newtonian and non-Newtonian viscosity models. In the second, the foam is represented as a porous media continuum, which has permeability properties that are determined by computing the pressure gradient through the foam geometry over a range of flow speeds comparable to those of in vivo conditions. Virtual angiography and additional post-processing demonstrate that the SMP foam significantly reduces the blood flow speed within the treated aneurysms, while eliminating the high-frequency velocity fluctuations that are present within the pre-treatment aneurysms. An estimation of the initial locations of thrombus formation throughout the SMP foam is obtained by means of a low fidelity thrombosis model that is based upon the residence time and shear rate of blood. The Newtonian viscosity model and the porous media model capture similar qualitative trends, though both yield a smaller volume of thrombus within the SMP foam. PMID:23329002

  2. Virtual Treatment of Basilar Aneurysms Using Shape Memory Polymer Foam

    NASA Astrophysics Data System (ADS)

    Ortega, J. M.; Hartman, J.; Rodriguez, J. N.; Maitland, D. J.

    2012-11-01

    Numerical simulations are performed on patient-specific basilar aneurysms that are treated with shape memory polymer (SMP) foam. In order to assess the post-treatment hemodynamics, two modeling approaches are employed. In the first, the foam geometry is obtained from a micro-CT scan and the pulsatile blood flow within the foam is simulated for both Newtonian and non-Newtonian viscosity models. In the second, the foam is represented as a porous media continuum, which has permeability properties that are determined by computing the pressure gradient through the foam geometry over a range of flow speeds comparable to those of in vivo conditions. Virtual angiography and additional post-processing demonstrate that the SMP foam significantly reduces the blood flow speed within the treated aneurysms, while eliminating the high-frequency velocity fluctuations that are present prior to treatment. A prediction of the initial locations of thrombus formation throughout the SMP foam is obtained by means of a low fidelity thrombosis model that is based upon the residence time and shear rate of blood. The two modeling approaches capture similar qualitative trends for the initial locations of thrombus within the SMP foam.

  3. Method for loading shape memory polymer gripper mechanisms

    DOEpatents

    Lee, Abraham P.; Benett, William J.; Schumann, Daniel L.; Krulevitch, Peter A.; Fitch, Joseph P.

    2002-01-01

    A method and apparatus for loading deposit material, such as an embolic coil, into a shape memory polymer (SMP) gripping/release mechanism. The apparatus enables the application of uniform pressure to secure a grip by the SMP mechanism on the deposit material via differential pressure between, for example, vacuum within the SMP mechanism and hydrostatic water pressure on the exterior of the SMP mechanism. The SMP tubing material of the mechanism is heated to above the glass transformation temperature (Tg) while reshaping, and subsequently cooled to below Tg to freeze the shape. The heating and/or cooling may, for example, be provided by the same water applied for pressurization or the heating can be applied by optical fibers packaged to the SMP mechanism for directing a laser beam, for example, thereunto. At a point of use, the deposit material is released from the SMP mechanism by reheating the SMP material to above the temperature Tg whereby it returns to its initial shape. The reheating of the SMP material may be carried out by injecting heated fluid (water) through an associated catheter or by optical fibers and an associated beam of laser light, for example.

  4. 3D Printing of Shape Memory Polymers for Flexible Electronic Devices.

    PubMed

    Zarek, Matt; Layani, Michael; Cooperstein, Ido; Sachyani, Ela; Cohn, Daniel; Magdassi, Shlomo

    2016-06-01

    The formation of 3D objects composed of shape memory polymers for flexible electronics is described. Layer-by-layer photopolymerization of methacrylated semicrystalline molten macromonomers by a 3D digital light processing printer enables rapid fabrication of complex objects and imparts shape memory functionality for electrical circuits.

  5. Chromogenic Photonic Crystals Enabled by Novel Vapor-Responsive Shape-Memory Polymers.

    PubMed

    Fang, Yin; Ni, Yongliang; Choi, Baeck; Leo, Sin-Yen; Gao, Jian; Ge, Beverly; Taylor, Curtis; Basile, Vito; Jiang, Peng

    2015-06-24

    A new type of shape-memory polymer (SMP) is developed by integrating scientific principles drawn from two disparate fields: the fast-growing photonic crystal and SMP technologies. This new SMP enables room-temperature operation for the entire shape-memory cycle and instantaneous shape recovery triggered by exposure to a variety of organic vapors.

  6. Light-triggered self-healing and shape-memory polymers.

    PubMed

    Habault, Damien; Zhang, Hongji; Zhao, Yue

    2013-09-07

    In this review, we highlight the recent progress made in light-controlled self-healing and shape memory polymers. We analyse the materials design, underlying mechanisms and chemistries involved in the different methods developed for these two types of emerging photoresponsive materials. We show that these two seemingly different groups of functional materials are linked by a number of common approaches enabling their optical control, particularly the approaches based on the photothermal effect and photochemical reactions of photoswitching groups incorporated in polymer structures. Possible future developments and perspectives of using light as a unique trigger for polymer self-healing and shape-memory are also discussed.

  7. Optical reconfiguration by anisotropic diffraction in holographic polymer-dispersed liquid crystal memory.

    PubMed

    Ogiwara, Akifumi; Watanabe, Minoru

    2012-07-20

    Holographic polymer dispersed liquid crystal (HPDLC) memory is fabricated by a photoinduced phase separation comprised of polymer and liquid crystal (LC) phases using laser light interference exposures. The anisotropic diffraction induced by the alignment of LC in the periodic structure of the HPDLC memory is applied to reconstruct the configuration contexts for the optically reconfigurable gate arrays. Optical reconfiguration for various circuits under parallel programmability is implemented by switching the polarization state of incident light on the HPDLC memory using a spatial light modulator.

  8. Reconfigurable photonic crystals enabled by pressure-responsive shape-memory polymers.

    PubMed

    Fang, Yin; Ni, Yongliang; Leo, Sin-Yen; Taylor, Curtis; Basile, Vito; Jiang, Peng

    2015-06-15

    Smart shape-memory polymers can memorize and recover their permanent shape in response to an external stimulus (for example, heat). They have been extensively exploited for a wide spectrum of applications ranging from biomedical devices to aerospace morphing structures. However, most of the existing shape-memory polymers are thermoresponsive and their performance is hindered by heat-demanding programming and recovery steps. Although pressure is an easily adjustable process variable such as temperature, pressure-responsive shape-memory polymers are largely unexplored. Here we report a series of shape-memory polymers that enable unusual 'cold' programming and instantaneous shape recovery triggered by applying a contact pressure at ambient conditions. Moreover, the interdisciplinary integration of scientific principles drawn from two disparate fields--the fast-growing photonic crystal and shape-memory polymer technologies--enables fabrication of reconfigurable photonic crystals and simultaneously provides a simple and sensitive optical technique for investigating the intriguing shape-memory effects at nanoscale.

  9. Reconfigurable photonic crystals enabled by pressure-responsive shape-memory polymers

    PubMed Central

    Fang, Yin; Ni, Yongliang; Leo, Sin-Yen; Taylor, Curtis; Basile, Vito; Jiang, Peng

    2015-01-01

    Smart shape-memory polymers can memorize and recover their permanent shape in response to an external stimulus (for example, heat). They have been extensively exploited for a wide spectrum of applications ranging from biomedical devices to aerospace morphing structures. However, most of the existing shape-memory polymers are thermoresponsive and their performance is hindered by heat-demanding programming and recovery steps. Although pressure is an easily adjustable process variable such as temperature, pressure-responsive shape-memory polymers are largely unexplored. Here we report a series of shape-memory polymers that enable unusual ‘cold' programming and instantaneous shape recovery triggered by applying a contact pressure at ambient conditions. Moreover, the interdisciplinary integration of scientific principles drawn from two disparate fields—the fast-growing photonic crystal and shape-memory polymer technologies—enables fabrication of reconfigurable photonic crystals and simultaneously provides a simple and sensitive optical technique for investigating the intriguing shape-memory effects at nanoscale. PMID:26074349

  10. Dose-dependent vascular response following delivery of sirolimus via fast releasing, biodegradable polymer stent matrix: an experimental study in the porcine coronary model of restenosis.

    PubMed

    Buszman, Piotr P; Orlik, Bartłomiej; Pająk, Jacek; Jelonek, Michał; Krauze, Agata; Janas, Adam; Legutko, Jacek; Wojakowski, Wojciech; Buszman, Paweł E; Milewski, Krzysztof

    2015-01-01

    Fast releasing, rapamycin-eluting stents, although safe, showed inferior results with regard to inhibition of restenosis. Therefore, we report vascular effects of a novel, biodegradable polymer stent matrix with elevated sirolimus dose and fast release kinetics (ed-frSES, Alex, Balton) in the porcine coronary in-stent restenosis model. A total of 19 stents were implanted with 120% overstretch in the coronary arteries of seven domestic pigs: seven ed-frSES with 1.3 μg/mm2 of sirolimus, eight frSES with 1 μg/mm2 of sirolimus, and eight bare metal stents (BMS). For the following 28 days, coronary angiography was performed, animals were sacrificed, and the stented segments harvested for histopathological evaluation. In angiography at 28 days the late lumen loss was lowest in the elevated dose sirolimus eluting stent (SES) (ed-frSES: 0.20 ± 0.2 vs. frSES: 0.80 ± 0.5 vs. BMS: 0.96 ± 0.5 mm, p < 0.01). This was confirmed in the morphometric evaluation in histopathology as represented by a significant and dose-dependent decrease in the percentage area of stenosis (ed-frSES: 22.4 ± 12.7% vs. frSES: 35 ± 10.7% vs. BMS: 47.5 ± 12.5%, p < 0.01). There was no peri-strut inflammation in any of the groups. However, the endothelialisation score was numerically not meaningfully decreased in ed-frSES (ed-frSES: 2.93 vs. frSES: 3. vs. BMS: 3, p = 0.05). Signs of fibrin were also noted in ed-frSES (ed-frSES: 0.4 vs. frSES: 0 vs. BMS: 0, p = 0.05). Sirolimus dose-dependent vascular response was reported. The elevated dose, fast releasing SES shows satisfactory vascular healing, similar to regular dose, fast release SES, with improved efficacy in restenosis inhibition.

  11. Self-assembly of Nanopatterns on Shape Memory Polymer Substrates

    NASA Astrophysics Data System (ADS)

    Chen, Zhongbi

    Periodic surface nanostructures provide unique acoustic, electronic, optical and mechanical properties, with potential applications to metamaterials, sensors, catalysis, medicine, etc. However, assembling nanometer scale constituents into engineering scale components or devices poses tremendous challenges such as cost reduction and scalability. In this work, we will introduce a novel directed self-assembly method that has the potential to address these challenges by forming unidirectional micro- and nano-wrinkles on engineering scale polymer substrates. The approach utilizes a smart material, shape memory polymer (SMP), as the substrate in a bi-layer thin-film/substrate system. With a specially-designed programming scheme, the SMP substrate can retract in one direction while expand in the perpendicular direction in a heating process. Consequently, the thin film corrugates and the wrinkling patterns are aligned. A parametric study that investigates how the system parameters influence the surface topology will be presented. Besides wrinkles, surface defects that occurred concurrently were also observed. We will present a progressive damage scheme and a microdomain-based model to understand and possibly help preventing the formation of defects. In addition, this work will also address our efforts in shrinking the wrinkle feature size from several microns to the tens of nanometer range. Two methods, through which the minimum wrinkle wavelength was reduced from one micron to 300 nm and further down to 35 nm will be elaborated. Such aligned wrinkles whose wavelength spanning two orders of magnitude from as small as 35 nm to as large as 5 mum will open up avenues for numerous exciting applications. The application of using the self-assembled wrinkled surface as the back-reflector in solar cells to improve the power conversion efficiency will be discussed as a case study. The long-term stability of the wrinkle topology, which is essential to efficiency boost will be

  12. Six-month IVUS and two-year clinical outcomes in the EVOLVE FHU trial: a randomised evaluation of a novel bioabsorbable polymer-coated, everolimus-eluting stent.

    PubMed

    Meredith, Ian T; Verheye, Stefan; Weissman, Neil J; Barragan, Paul; Scott, Douglas; Valdés Chávarri, Mariano; West, Nick E J; Kelbæk, Henning; Whitbourn, Robert; Walters, Darren L; Kubica, Jacek; Thuesen, Leif; Masotti, Monica; Banning, Adrian; Sjögren, Iwar; Stables, Rod H; Allocco, Dominic J; Dawkins, Keith D

    2013-07-01

    The EVOLVE FHU trial demonstrated non-inferiority of six-month late loss with two dose formulations of SYNERGY, a novel bioabsorbable polymer everolimus-eluting stent (EES) compared with the durable polymer PROMUS Element (PE) EES. The current analysis describes the six-month IVUS and clinical results through two years from the EVOLVE FHU trial. EVOLVE recruited 291 patients from 29 centres. At six months, IVUS-assessed in-stent net volume obstruction was 3.40 ± 5.06% for PROMUS Element (PE) vs. 2.68 ± 4.60% for SYNERGY (p=0.34) and 3.09 ± 4.29% for SYNERGY ½ dose (p=0.68 vs. PE). There were no significant differences between groups for any other measured IVUS parameter including resolved, persistent, and late-acquired incomplete stent apposition (ISA). At two years, target lesion failure (TLF) was 6.1% for PE vs. 5.5% for SYNERGY (p=0.87) and 5.2% for SYNERGY ½ dose (p=0.81). There were no significant differences between groups for cardiac death, repeat revascularisation, MI or stent thrombosis through two years. At six months, everolimus delivered from an ultrathin bioabsorbable abluminal polymer resulted in equivalent net volume obstruction and ISA compared with a permanent polymer EES. There were no significant differences between PE and either SYNERGY stent for any major cardiac endpoint through two years. Clinical trials number: NCT01135225.

  13. Six-month IVUS and two-year clinical outcomes in the EVOLVE FHU trial: a randomised evaluation of a novel bioabsorbable polymer-coated, everolimus-eluting stent.

    PubMed

    Meredith, Ian T; Verheye, Stefan; Weissman, Neil J; Barragan, Paul; Scott, Douglas; Chávarri, Mariano Valdés; West, Nick E J; Kelbæk, Henning; Whitbourn, Robert; Walters, Darren L; Kubica, Jacek; Thuesen, Leif; Masotti, Monica; Banning, Adrian; Sjögren, Iwar; Stables, Rod H; Allocco, Dominic J; Dawkins, Keith D

    2013-05-22

    Aims: The EVOLVE FHU trial demonstrated non-inferiority of six-month late loss with two dose formulations of SYNERGY, a novel bioabsorbable polymer everolimus-eluting stent (EES) compared with the durable polymer PROMUS Element (PE) EES. The current analysis describes the six-month IVUS and clinical results through two years from the EVOLVE FHU trial. Methods and results: EVOLVE recruited 291 patients from 29 centres. At six months, IVUS-assessed in-stent net volume obstruction was 3.40±5.06% for PROMUS Element (PE) vs. 2.68±4.60% for SYNERGY (p=0.34) and 3.09±4.29% for SYNERGY ½ dose (p=0.68 vs. PE). There were no significant differences between groups for any other measured IVUS parameter including resolved, persistent, and late-acquired incomplete stent apposition (ISA). At two years, target lesion failure (TLF) was 6.1% for PE vs. 5.5% for SYNERGY (p=0.87) and 5.2% for SYNERGY ½ dose (p=0.81). There were no significant differences between groups for cardiac death, repeat revascularisation, MI or stent thrombosis through two years. Conclusions: At six months, everolimus delivered from an ultrathin bioabsorbable abluminal polymer resulted in equivalent net volume obstruction and ISA compared with a permanent polymer EES. There were no significant differences between PE and either SYNERGY stent for any major cardiac endpoint through two years. Clinical trials number: NCT01135225.

  14. Advances in stent drug delivery: the future is in bioabsorbable stents.

    PubMed

    Wykrzykowska, Joanna J; Onuma, Yoshinobu; Serruys, Patrick W

    2009-02-01

    This expert opinion review offers a perspective on the future developments in drug-eluting stent design. Initial efforts were focused on reduction of in-stent restenosis, which the drug-eluting stents addressed effectively. Current concerns are predominantly with regard to risk of stent thrombosis and delayed endothelialization. All three components of the stent have been modified to achieve the goal of endothelialization and vessel healing: drug, polymer and the platform. We review different approaches to reduce this risk from design of different drug combinations, through less traumatic metallic stent platforms, via biodegradable polymers and, finally, fully biodegradable stents. It seems at this time that fully biodegradable solutions to stenting hold the greatest promise, but larger long-term studies are needed to evaluate fully their safety and efficacy in 'all-comer' patient populations. At the time of this review, design of a safe drug-eluting stent still remains a challenge.

  15. First-in-man study evaluating the safety and efficacy of a second generation biodegradable polymer sirolimus-eluting stent in the treatment of patients with de novo coronary lesions: clinical, Angiographic, and OCT outcomes of CREDIT-1.

    PubMed

    Wang, Geng; Sun, Zhongwei; Jin, Quanmin; Xu, Kai; Li, Yi; Wang, Xiaozeng; Ma, Yingyan; Liu, Haiwei; Zhao, Xin; Wang, Bin; Deng, Jie; Guan, Shaoyi; Ge, Meiling; Wang, Xiaoyan; Xu, Bo; Han, Yaling

    2015-03-01

    To evaluate the preliminary safety and efficacy of the EXCEL II stent system. Although the first biodegradable polymer drug-eluting stent (BP-DES), EXCEL, was launched nearly a decade ago, in-stent restenosis and stent thrombosis remain pertinent clinical problems in practice. A new cobalt-chromium BP-DES EXCEL II has been developed with the aim of improving stent safety and efficacy. Forty-five patients with single de novo native coronary lesions were enrolled and randomized to two groups in a 2:1 ratio, the 4-month follow-up group (n = 30) and the 12-month follow-up group (n = 15). All patients underwent percutaneous coronary intervention (PCI) with the EXCEL II stent system. Quantitative coronary angiography (QCA) and optical coherence tomography (OCT) were used to assess coronary vasculature at the designated 4- or 12-month follow-up. The primary outcome was major adverse cardiac events (MACE) at 30 days post-PCI. No MACE, thrombotic events, or target lesion failure was found in the 45 patients during the 12-month follow-up. There was no significant difference (P > 0.05) between the two groups in terms of in-stent and in-segment late lumen loss (LLL). No in-stent and in-segment restenosis was found in either group. At follow-up, the ratio of >10% uncovered struts per lesion was 26.67% in the 4-month group and 0% in the 12-month group (P < 0.05). Neointimal coverage in the 12-month group was significantly better than in the 4-month group (98.58% vs. 93.51%, P < 0.01). This first-in-man study demonstrates promising feasibility, safety, and efficacy of EXCEL II stents. These stents were found to have rapid endothelialization and low LLL rates at 4 and 12 months after implantation. © 2015 Wiley Periodicals, Inc.

  16. Durability of carbon fiber reinforced shape memory polymer composites in space

    NASA Astrophysics Data System (ADS)

    Jang, Joon Hyeok; Hong, Seok Bin; Ahn, Yong San; Kim, Jin-Gyun; Nam, Yong-Youn; Lee, Geun Ho; Yu, Woong-Ryeol

    2016-04-01

    Shape memory polymer (SMP) is one of smart polymers which exhibit shape memory effect upon external stimuli. Recently, shape memory polymer composites (SMPCs) have been considered for space structure instead of shape memory alloys due to their deformability, lightweight and large recovery ratio, requiring characterization of their mechanical properties against harsh space environment and further prediction of the durability of SMPCs in space. As such, the durability of carbon fiber reinforced shape memory polymer composites (CF-SMPCs) was investigated using accelerated testing method based on short-term testing of CF-SMPCs in harsh condition. CF-SMPCs were prepared using woven carbon fabrics and a thermoset SMP via vacuum assisted resin transfer molding process. Bending tests with constant strain rate of CF-SMPCs were conducted using universal tensile machine (UTM) and Storage modulus test were conducted using dynamic mechanical thermal analysis (DMTA). Using the results, a master curve based on time-temperature superposition principle was then constructed, through which the mechanical properties of CF-SMPCs at harsh temperature were predicted. CF-SMPCs would be exposed to simulated space environments under ultra-violet radiations at various temperatures. The mechanical properties including flexural and tensile strength and shape memory properties of SMPCs would be measured using UTM before and after such exposures for comparison. Finally, the durability of SMPCs in space would be assessed by developing a degradation model of SMPC.

  17. Flexible Nonvolatile Polymer Memory Array on Plastic Substrate via Initiated Chemical Vapor Deposition.

    PubMed

    Jang, Byung Chul; Seong, Hyejeong; Kim, Sung Kyu; Kim, Jong Yun; Koo, Beom Jun; Choi, Junhwan; Yang, Sang Yoon; Im, Sung Gap; Choi, Sung-Yool

    2016-05-25

    Resistive random access memory based on polymer thin films has been developed as a promising flexible nonvolatile memory for flexible electronic systems. Memory plays an important role in all modern electronic systems for data storage, processing, and communication; thus, the development of flexible memory is essential for the realization of flexible electronics. However, the existing solution-processed, polymer-based RRAMs have exhibited serious drawbacks in terms of the uniformity, electrical stability, and long-term stability of the polymer thin films. Here, we present poly(1,3,5-trimethyl-1,3,5-trivinyl cyclotrisiloxane) (pV3D3)-based RRAM arrays fabricated via the solvent-free technique called initiated chemical vapor deposition (iCVD) process for flexible memory application. Because of the outstanding chemical stability of pV3D3 films, the pV3D3-RRAM arrays can be fabricated by a conventional photolithography process. The pV3D3-RRAM on flexible substrates showed unipolar resistive switching memory with an on/off ratio of over 10(7), stable retention time for 10(5) s, excellent cycling endurance over 10(5) cycles, and robust immunity to mechanical stress. In addition, pV3D3-RRAMs showed good uniformity in terms of device-to-device distribution. The pV3D3-RRAM will pave the way for development of next-generation flexible nonvolatile memory devices.

  18. Tailored (meth)acrylate shape-memory polymer networks for ophthalmic applications.

    PubMed

    Song, Li; Hu, Wang; Wang, Guojie; Niu, Guoguang; Zhang, Hongbin; Cao, Hui; Wang, Kaijie; Yang, Huai; Zhu, Siquan

    2010-10-08

    The unique features of shape-memory polymers enables their use in minimally invasive surgical procedures with a compact starting material switching over to a voluminous structure in vivo. In this work, a series of transparent, thermoset (meth)acrylate shape-memory polymer networks with tailored thermomechanics have been synthesized and evaluated. Fundamental trends were established for the effect of the crosslinker content and crosslinker molecular weight on glass transition temperature, rubbery modulus and shape-recovery behavior, and the results are intended to help with future shape-memory device design. The prepared (meth)acrylate networks with high transparency and favorable biocompatibility are presented as a promising shape-memory ophthalmic biomaterial.

  19. Initiation of shape-memory effect by inductive heating of magnetic nanoparticles in thermoplastic polymers

    PubMed Central

    Mohr, R.; Kratz, K.; Weigel, T.; Lucka-Gabor, M.; Moneke, M.; Lendlein, A.

    2006-01-01

    In shape-memory polymers, changes in shape are mostly induced by heating, and exceeding a specific switching temperature, Tswitch. If polymers cannot be warmed up by heat transfer using a hot liquid or gaseous medium, noncontact triggering will be required. In this article, the magnetically induced shape-memory effect of composites from magnetic nanoparticles and thermoplastic shape-memory polymers is introduced. A polyetherurethane (TFX) and a biodegradable multiblock copolymer (PDC) with poly(p-dioxanone) as hard segment and poly(ε-caprolactone) as soft segment were investigated as matrix component. Nanoparticles consisting of an iron(III)oxide core in a silica matrix could be processed into both polymers. A homogeneous particle distribution in TFX could be shown. Compounds have suitable elastic and thermal properties for the shape-memory functionalization. Temporary shapes of TFX compounds were obtained by elongating at increased temperature and subsequent cooling under constant stress. Cold-drawing of PDC compounds at 25°C resulted in temporary fixation of the mechanical deformation by 50–60%. The shape-memory effect of both composite systems could be induced by inductive heating in an alternating magnetic field (f = 258 kHz; H = 30 kA·m−1). The maximum temperatures achievable by inductive heating in a specific magnetic field depend on sample geometry and nanoparticle content. Shape recovery rates of composites resulting from magnetic triggering are comparable to those obtained by increasing the environmental temperature. PMID:16537442

  20. Fabrication and characterization of a foamed polylactic acid (PLA)/ thermoplastic polyurethane (TPU) shape memory polymer (SMP) blend for biomedical and clinical applications

    NASA Astrophysics Data System (ADS)

    Song, Janice J.; Srivastava, Ijya; Kowalski, Jennifer; Naguib, Hani E.

    2014-03-01

    Shape memory polymers (SMP) are a class of stimuli-responsive materials that are able to respond to external stimulus such as heat by altering their shape. Bio-compatible SMPs have a number of advantages over static materials and are being studied extensively for biomedical and clinical applications (such as tissue stents and scaffolds). A previous study has demonstrated that the bio-compatible polymer blend of polylactic acid (PLA)/ thermoplastic polyurethane (TPU) (50/50 and 70/30) exhibit good shape memory properties. In this study, the mechanical and thermo-mechanical (shape memory) properties of TPU/PLA SMP blends were characterized; the compositions studied were 80/20, 65/35, and 50/50 TPU/PLA. In addition, porous TPU/PLA SMP blends were fabricated with a gas-foaming technique; and the morphology of the porous structure of these SMPs foams were characterized with scanning electron microscopy (SEM). The TPU/PLA bio-compatible SMP blend was fabricated with melt-blending and compression molding. The glass transition temperature (Tg) of the SMP blends was determined with a differential scanning calorimeter (DSC). The mechanical properties studied were the stress-strain behavior, tensile strength, and elastic modulus; and the thermomechanical (or shape memory) properties studied were the shape fixity rate (Rf), shape recovery rate (Rr), response time, and the effect of recovery temperature on Rr. The porous 80/20 PLA/TPU SMP blend was found to have the highest tensile strength, toughness and percentage extension, as well as the lowest density and uniform pore structure in the micron and submicron scale. The porous 80/20 TPU/PLA SMP blend may be further developed for specific biomedical and clinical applications where a combination of tensile strength, toughness, and low density are required.

  1. Randomized Multicenter Trial Investigating Angiographic Outcomes of Hybrid Sirolimus-Eluting Stents With Biodegradable Polymer Compared With Everolimus-Eluting Stents With Durable Polymer in Chronic Total Occlusions: The PRISON IV Trial.

    PubMed

    Teeuwen, Koen; van der Schaaf, René J; Adriaenssens, Tom; Koolen, Jacques J; Smits, Pieter C; Henriques, José P S; Vermeersch, Paul H M J; Tjon Joe Gin, R Melvyn; Schölzel, Bastiaan E; Kelder, Johannes C; Tijssen, Jan G P; Agostoni, Pierfrancesco; Suttorp, Maarten J

    2017-01-23

    The aim of this study was to investigate the efficacy and safety of the hybrid ultrathin-strut sirolimus-eluting stent (SES) with biodegradable polymer compared with the thin-strut everolimus-eluting stent (EES) with durable polymer in successfully recanalized chronic total occlusions (CTOs). The introduction of drug-eluting stents revolutionized the treatment of CTOs. However, limited data are available on new-generation drug-eluting stents with biodegradable polymer in CTOs. In this multicenter trial, patients were randomized, after successful CTO recanalization, to either SES or EES. The primary noninferiority endpoint was in-segment late lumen loss (noninferiority margin 0.2 mm). Secondary endpoints included in-stent late lumen loss and clinical endpoints. Overall, 330 patients were included. At 9 months, angiography was available in 281 patients (85%). Duration of occlusion ≥3 months was 92.5%, with mean stent length of 52.4 ± 28.1 mm versus 52.3 ± 26.5 mm in the SES and EES groups. The primary noninferiority endpoint, in-segment late lumen loss, was not met for SES versus EES (0.13 ± 0.63 mm vs. 0.02 ± 0.47 mm; p = 0.08, 2-sided; difference 0.11 mm; 95% confidence interval: -0.01 to 0.25 mm; pnoninferiority = 0.11, 1-sided). In-stent late lumen loss was comparable between SES and EES (0.12 ± 0.59 mm vs. 0.07 ± 0.46 mm; p = 0.52). The incidence of in-stent and in-segment binary restenosis was significantly higher with SES compared with EES (8.0% vs. 2.1%; p = 0.028), with comparable rates of reocclusions (2.2% vs. 1.4%; p = 0.68). Clinically indicated target lesion and target vessel revascularization (9.2% vs. 4.0% [p = 0.08] and 9.2% vs. 6.0% [p = 0.33]), target vessel failure (9.9% vs. 6.6%; p = 0.35), and definite or probable stent thrombosis (0.7% vs. 0.7%; p = 1.00) were comparable between the SES and EES groups. This randomized trial failed to show noninferiority of hybrid SES relative to EES in terms of in-segment late lumen loss

  2. Processing and Characterization of Shape Memory Polymer Nanocomposites (Preprint)

    DTIC Science & Technology

    2006-02-01

    Group on Polymer Nanocomposites- PNC- Tech, http://www.imi.cnrc-nrc.gc.ca/ english /Default.htm. 2. Zhu, J ., et al ., “Reinforcing Epoxy Polymer Composites...through Covalent Integration of Functionalized Nanotubes”, Advanced Functional Materials, No. 7, 2004, pp.643-648. 3. Zeng, J ., et al , “Processing...Barrera, V., “A Study on Nanofiber-Reinforced Thermoplastic Composites (II): Investigation of the mixing Rheology and Conduction Properties

  3. Photo-Responsive Shape-Memory and Shape-Changing Liquid-Crystal Polymer Networks

    PubMed Central

    Iqbal, Danish; Samiullah, Muhammad Haris

    2013-01-01

    “Surrounding matters” is a phrase that has become more significant in recent times when discussing polymeric materials. Although regular polymers do respond to external stimuli like softening of material at higher temperatures, that response is gradual and linear in nature. Smart polymers (SPs) or stimuli-responsive polymers (SRPs) behave differently to those external stimuli, as their behavior is more rapid and nonlinear in nature and even a small magnitude of external stimulus can cause noticeable changes in their shape, size, color or conductivity. Of these SRPs, two types of SPs with the ability to actively change can be differentiated: shape-memory polymers and shape-changing polymers. The uniqueness of these materials lies not only in the fast macroscopic changes occurring in their structure but also in that some of these shape changes are reversible. This paper presents a brief review of current progress in the area of light activated shape-memory polymers and shape-changing polymers and their possible field of applications. PMID:28809298

  4. Photo-enhanced polymer memory device based on polyimide containing spiropyran

    NASA Astrophysics Data System (ADS)

    Seok, Woong Chul; Son, Seok Ho; An, Tae Kyu; Kim, Se Hyun; Lee, Seung Woo

    2016-07-01

    This paper reports the synthesis of a new polyimide (PI) containing a spiropyran moiety in the side chain and its applications to the switchable polymer memory before and after UV exposure. UV exposure allows memory using spiropyran-based PI as an active layer with a higher current and lower switching-ON voltage compared to the unexposed device due to the structural changes in the spiropyran moiety after UV exposure. In addition, this study examined the effects of UV exposure on the performance of the memory containing spiropyran-based PI using the UV-Vis absorption spectra and space-charge limited conduction (SCLC) model. [Figure not available: see fulltext.

  5. A molecular dynamics investigation of the deformation mechanism and shape memory effect of epoxy shape memory polymers

    NASA Astrophysics Data System (ADS)

    Yang, Hua; Wang, ZhengDao; Guo, YaFang; Shi, XingHua

    2016-03-01

    Following deformation, thermally induced shape memory polymers (SMPs) have the ability to recover their original shape with a change in temperature. In this work, the thermomechanical properties and shape memory behaviors of three types of epoxy SMPs with varying curing agent contents were investigated using a molecular dynamics (MD) method. The mechanical properties under uniaxial tension at different temperatures were obtained, and the simulation results compared reasonably with experimental data. In addition, in a thermomechanical cycle, ideal shape memory effects for the three types of SMPs were revealed through the shape frozen and shape recovery responses at low and high temperatures, respectively, indicating that the recovery time is strongly influenced by the ratio of E-51 to 4,4'-Methylenedianiline.

  6. Investigation of interfacial shear stresses, shape fixity, and actuation strain in composites incorporating shape memory polymers and shape memory alloys

    NASA Astrophysics Data System (ADS)

    Park, Jungkyu; Headings, Leon; Dapino, Marcelo; Baur, Jeffery; Tandon, Gyaneshwar

    2015-03-01

    Shape memory composites (SMCs) based on shape memory alloys (SMAs) and shape memory polymers (SMPs) allow many design possibilities due to their controllable temperature-dependent mechanical properties. The complementary characteristics of SMAs and SMPs can be utilized in systems with shape recovery created by the SMA and shape fixity provided by the SMP. In this research, three SMC operating regimes are identified and the behavior of SMC structures is analyzed by focusing on composite shape fixity and interfacial stresses. Analytical models show that SMPs can be used to adequately fix the shape of SMA actuators and springs. COMSOL finite element simulations are in agreement with analytical expressions for shape fixity and interfacial stresses. Analytical models are developed for an end-coupled linear SMP-SMA two-way actuator and the predicted strain is shown to be in good agreement with experimental test results.

  7. Electrochromic conductive polymer fuses for hybrid organic/inorganic semiconductor memories

    NASA Astrophysics Data System (ADS)

    Möller, Sven; Forrest, Stephen R.; Perlov, Craig; Jackson, Warren; Taussig, Carl

    2003-12-01

    We demonstrate a nonvolatile, write-once-read-many-times (WORM) memory device employing a hybrid organic/inorganic semiconductor architecture consisting of thin film p-i-n silicon diode on a stainless steel substrate integrated in series with a conductive polymer fuse. The nonlinearity of the silicon diodes enables a passive matrix memory architecture, while the conductive polyethylenedioxythiophene:polystyrene sulfonic acid polymer serves as a reliable switch with fuse-like behavior for data storage. The polymer can be switched at ˜2 μs, resulting in a permanent decrease of conductivity of the memory pixel by up to a factor of 103. The switching mechanism is primarily due to a current and thermally dependent redox reaction in the polymer, limited by the double injection of both holes and electrons. The switched device performance does not degrade after many thousand read cycles in ambient at room temperature. Our results suggest that low cost, organic/inorganic WORM memories are feasible for light weight, high density, robust, and fast archival storage applications.

  8. Drug-releasing shape-memory polymers - the role of morphology, processing effects, and matrix degradation.

    PubMed

    Wischke, Christian; Behl, Marc; Lendlein, Andreas

    2013-09-01

    Shape-memory polymers (SMPs) have gained interest for temporary drug-release systems that should be anchored in the body by self-sufficient active movements of the polymeric matrix. Based on the so far published scientific literature, this review highlights three aspects that require particular attention when combining SMPs with drug molecules: i) the defined polymer morphology as required for the shape-memory function, ii) the strong effects that processing conditions such as drug-loading methodologies can have on the drug-release pattern from SMPs, and iii) the independent control of drug release and degradation by their timely separation. The combination of SMPs with a drug-release functionality leads to multifunctional carriers that are an interesting technology for pharmaceutical sciences and can be further expanded by new materials such as thermoplastic SMPs or temperature-memory polymers. Experimental studies should include relevant molecules as (model) drugs and provide a thermomechanical characterization also in an aqueous environment, report on the potential effect of drug type and loading levels on the shape-memory functionality, and explore the potential correlation of polymer degradation and drug release.

  9. Fast Triggering of Shape Memory Polymers using an Embedded Carbon Nanotube Sponge Network.

    PubMed

    Zhou, Guoxiang; Zhang, Heng; Xu, Shuping; Gui, Xuchun; Wei, Hongqiu; Leng, Jinsong; Koratkar, Nikhil; Zhong, Jing

    2016-04-07

    In this work, a 3-D porous carbon nanotube sponge (CNTS) was embedded within a shape memory polymer (SMPs) matrix. We demonstrate complete infiltration and filling of the SMPs into the CNTS by capillary force without any damage to the CNTS structure. With only ~0.2 wt% carbon nanotube loading, the glass transition temperature is increased by ~20 °C, indicating strong interaction between CNTS and the SMPs matrix. Further, we find that the uniform distribution of the carbon nanotubes in the nanocomposite results in high electrical conductivity, and thus highly effective electricity triggering capability. The carbon nanotube sponge shape memory polymer (CNTS/SMPs) nanocomposite could be triggered within ~10 seconds by the application of ~10 volts. Results from finite element simulations showed good agreement with the experimental results, and indicated that for our system the interface thermal energy loss does not have a significant effect on the heating rate of the polymer matrix.

  10. Comparison of 3 biodegradable polymer and durable polymer-based drug-eluting stents in all-comers (BIO-RESORT): rationale and study design of the randomized TWENTE III multicenter trial.

    PubMed

    Lam, Ming Kai; Sen, Hanim; Tandjung, Kenneth; van Houwelingen, K Gert; de Vries, Arie G; Danse, Peter W; Schotborgh, Carl E; Scholte, Martijn; Löwik, Marije M; Linssen, Gerard C M; Ijzerman, Maarten J; van der Palen, Job; Doggen, Carine J M; von Birgelen, Clemens

    2014-04-01

    To evaluate the safety and efficacy of 2 novel drug-eluting stents (DES) with biodegradable polymer-based coatings versus a durable coating DES. BIO-RESORT is an investigator-initiated, prospective, patient-blinded, randomized multicenter trial in 3540 Dutch all-comers with various clinical syndromes, requiring percutaneous coronary interventions (PCI) with DES implantation. Randomization (stratified for diabetes mellitus) is being performed in a 1:1:1 ratio between ORSIRO sirolimus-eluting stent with circumferential biodegradable coating, SYNERGY everolimus-eluting stent with abluminal biodegradable coating, and RESOLUTE INTEGRITY zotarolimus-eluting stent with durable coating. The primary endpoint is the incidence of the composite endpoint target vessel failure at 1 year, consisting of cardiac death, target vessel-related myocardial infarction, or clinically driven target vessel revascularization. Power calculation assumes a target vessel failure rate of 8.5% with a 3.5% non-inferiority margin, giving the study a power of 85% (α level .025 adjusted for multiple testing). The impact of diabetes mellitus on post-PCI outcome will be evaluated. The first patient was enrolled on December 21, 2012. BIO-RESORT is a large, prospective, randomized, multicenter trial with three arms, comparing two DES with biodegradable coatings versus a reference DES with a durable coating in 3540 all-comers. The trial will provide novel insights into the clinical outcome of modern DES and will address the impact of known and so far undetected diabetes mellitus on post-PCI outcome. Copyright © 2014 The Authors. Published by Mosby, Inc. All rights reserved.

  11. Shape memory polymer nanofibers and their composites: electrospinning, structure, performance and applications

    NASA Astrophysics Data System (ADS)

    Zhang, Fenghua; Zhang, Zhichun; Zhou, Tianyang; Liu, Yanju; Leng, Jinsong

    2015-10-01

    Shape memory polymers (SMPs) have been defined as a kind of smart materials under great investigation from academic research to industry applications. Research on SMPs and their composites, now incorporates a growing focus on nanofibers which offers new structures in microscopic level and the potential of enhanced performance of SMPs. This paper presents a comprehensive review of the development of shape memory polymer nanofibers and their composites, including the introduction of electrospinning technology, the morphology and structures of nanofibers (non-woven fibers, oriented fibers, core/shell fibers and functional particles added in the fibers), shape memory performance (thermal and mechanical properties, stimulus responsive behavior, multiple and two-way shape changing performance), as well as their potential applications in the fields of biomedical and tissue engineering.

  12. Experimental and modelling studies of the shape memory properties of amorphous polymer network composites

    NASA Astrophysics Data System (ADS)

    Arrieta, J. S.; Diani, J.; Gilormini, P.

    2014-09-01

    Shape memory polymer composites (SMPCs) have become an important way to leverage improvements in the development of applications featuring shape memory polymers (SMPs). In this study, an amorphous SMP matrix has been filled with different types of reinforcements. An experimental set of results is presented and then compared to three-dimensional (3D) finite-element simulations. Thermomechanical shape memory cycles were performed in uniaxial tension. The fillers effect was studied in stress-free and constrained-strain recoveries. Experimental observations indicate complete shape recovery and put in evidence the increased sensitivity of constrained length stress recoveries to the heating ramp on the tested composites. The simulations reproduced a simplified periodic reinforced composite and used a model for the matrix material that has been previously tested on regular SMPs. The latter combines viscoelasticity at finite strain and time-temperature superposition. The simulations easily allow representation of the recovery properties of a reinforced SMP.

  13. Controlled wettability based on reversible micro-cracking on a shape memory polymer surface.

    PubMed

    Han, Yu; Liu, Yuxuan; Wang, Wenxin; Leng, Jinsong; Jin, Peng

    2016-03-14

    Wettability modification on a polymer surface is of immense importance for flexible electronics and biomedical applications. Herein, controlled wettability of a styrene-based shape memory polymer has been realized by introducing micro-cracks on the polymer surface for the first time. The cracks were purposely prepared by thin metal film constrained deformation on the polymer. After the removal of the metallic film, wettability was dramatically enhanced by showing a remarkable reduction in the contact angle with water droplets from 85° to 25°. Subsequent systematic characterization techniques like XPS and SEM revealed that such observation could be attributed to the increased density of hydrophilic groups and the roughened surface. In addition, by controlling the temperature for annealing the treated polymer, the surface could be switched reversely to water-repellent. Therefore, this paper offers a smart tactic to manipulate the surface wettability of a shape memory polymer freely. The features of the controlled wettability surface such as high tenability, high stability and easy fabrication are promising for microfluidic switching and molecule/cell capture-release.

  14. Clinical outcomes in 995 unselected real-world patients treated with an ultrathin biodegradable polymer-coated sirolimus-eluting stent: 12-month results from the FLEX Registry

    PubMed Central

    Lemos, Pedro A; Chandwani, Prakash; Saxena, Sudheer; Ramachandran, Padma Kumar; Abhyankar, Atul; Campos, Carlos M; Marchini, Julio Flavio; Galon, Micheli Zanotti; Verma, Puneet; Sandhu, Manjinder Singh; Parikh, Nikhil; Bhupali, Ashok; Jain, Sharad; Prajapati, Jayesh

    2016-01-01

    Objectives To evaluate, in the FLEX Registry, clinical outcomes of an ultrathin (60 µm) biodegradable polymer-coated Supraflex sirolimus-eluting stent (SES) for the treatment of coronary artery disease. Additionally, to determine the vascular response to the Supraflex SES through optical coherence tomography (OCT) analysis. Setting Multicentre, single-arm, all-comers, observational registry of patients who were treated with the Supraflex SES, between July 2013 and May 2014, at nine different centres in India. Participants 995 patients (1242 lesions) who were treated with the Supraflex SES, between July 2013 and May 2014, at nine different centres in India. A total of 47 participants underwent OCT analysis at 6 months’ follow-up. Interventions Percutaneous coronary intervention with Supraflex SES, Primary and secondary outcome measures The primary endpoint—the rate of major adverse cardiac events (defined as a composite of cardiac death, myocardial infarction (MI), target lesion revascularisation (TLR))—was analysed during 12 months. Results At 12 months, the primary endpoint occurred in 36 (3.7%) of 980 patients, consisting of 18 (1.8%) cardiac deaths, 16 (1.6%) MI, 7 (0.7%) TLR and 2 (0.2%) cases of non-target lesion target vessel revascularization. In a subset of 47 patients, 1227 cross-sections (9309 struts) were analysed at 6 months by OCT. Overall, a high percentage of struts was covered (98.1%), with a mean neointimal thickness of 0.13±0.06 µm. Conclusions The FLEX Registry evaluated clinical outcomes in real-world and more complex cohorts and thus provides evidence that the Supraflex SEX can be used safely and routinely in a broader percutaneous coronary intervention population. Also, the Supraflex SES showed high percentage of stent strut coverage and good stent apposition during OCT follow-up. PMID:26888727

  15. A polymer/semiconductor write-once read-many-times memory.

    PubMed

    Möller, Sven; Perlov, Craig; Jackson, Warren; Taussig, Carl; Forrest, Stephen R

    2003-11-13

    Organic devices promise to revolutionize the extent of, and access to, electronics by providing extremely inexpensive, lightweight and capable ubiquitous components that are printed onto plastic, glass or metal foils. One key component of an electronic circuit that has thus far received surprisingly little attention is an organic electronic memory. Here we report an architecture for a write-once read-many-times (WORM) memory, based on the hybrid integration of an electrochromic polymer with a thin-film silicon diode deposited onto a flexible metal foil substrate. WORM memories are desirable for ultralow-cost permanent storage of digital images, eliminating the need for slow, bulky and expensive mechanical drives used in conventional magnetic and optical memories. Our results indicate that the hybrid organic/inorganic memory device is a reliable means for achieving rapid, large-scale archival data storage. The WORM memory pixel exploits a mechanism of current-controlled, thermally activated un-doping of a two-component electrochromic conducting polymer.

  16. Direct observation of localized conduction pathways in photocross-linkable polymer memory

    NASA Astrophysics Data System (ADS)

    Kwan, Wei Lek; Lei, Bao; Shao, Yue; Prikhodko, Sergey V.; Bodzin, Noah; Yang, Yang

    2009-06-01

    Resistive switching in photocross-linkable polymer memory devices was found to occur in localized areas of the device. In order to elucidate the reason behind the switching, we used focused ion-beam to prepare a cross-section of the device. It was found that after the device was switched to the high conductive state, in certain parts of the device, the electrodes were only about 5 nm apart. This was probably caused by a combination of high electric field and metal injection into the polymer film. Gold injection into the polymer film by locally enhanced electric field was confirmed by transmission electron microscope-energy dispersive x-ray analysis. This model was in agreement with both the temperature dependent and transient behavior of our device. We conclude that the non-uniformities at the nanoscale interface of the electrode dominated the device characteristics while the polymer played only a secondary role.

  17. Nonvolatile Transistor Memory with Self-Assembled Semiconducting Polymer Nanodomain Floating Gates.

    PubMed

    Wang, Wei; Kim, Kang Lib; Cho, Suk Man; Lee, Ju Han; Park, Cheolmin

    2016-12-14

    Organic field effect transistor based nonvolatile memory (OFET-NVM) with semiconducting nanofloating gates offers additional benefits over OFET-NVMs with conventional metallic floating gates due to the facile controllability of charge storage based on the energetic structure of the floating gate. In particular, an all-in-one tunneling and floating-gate layer in which the semiconducting polymer nanodomains are self-assembled in the dielectric tunneling layer is promising. In this study, we utilize crystals of a p-type semiconducting polymer in which the crystalline lamellae of the polymer are spontaneously developed and embedded in the tunneling matrix as the nanofloating gate. The widths and lengths of the polymer nanodomains are approximately 20 nm and a few hundred nanometers, respectively. An OFET-NVM containing the crystalline nanofloating gates exhibits memory performance with a large memory window of 10 V, programming/erasing switching endurance for over 500 cycles, and a long retention time of 5000 s. Moreover, the device performance is improved by comixing with an n-type semiconductor; thus, the solution-processed p- and n-type double floating gates capable of storing both holes and electrons allow for the multilevel operation of our OFET-NVM. Four highly reliable levels (two bits per cell) of charge trapping and detrapping are achieved using this OFET-NVM by accurately choosing the programming/erasing voltages.

  18. Estimation of aneurysm wall stresses created by treatment with a shape memory polymer foam device.

    PubMed

    Hwang, Wonjun; Volk, Brent L; Akberali, Farida; Singhal, Pooja; Criscione, John C; Maitland, Duncan J

    2012-05-01

    In this study, compliant latex thin-walled aneurysm models are fabricated to investigate the effects of expansion of shape memory polymer foam. A simplified cylindrical model is selected for the in-vitro aneurysm, which is a simplification of a real, saccular aneurysm. The studies are performed by crimping shape memory polymer foams, originally 6 and 8 mm in diameter, and monitoring the resulting deformation when deployed into 4-mm-diameter thin-walled latex tubes. The deformations of the latex tubes are used as inputs to physical, analytical, and computational models to estimate the circumferential stresses. Using the results of the stress analysis in the latex aneurysm model, a computational model of the human aneurysm is developed by changing the geometry and material properties. The model is then used to predict the stresses that would develop in a human aneurysm. The experimental, simulation, and analytical results suggest that shape memory polymer foams have potential of being a safe treatment for intracranial saccular aneurysms. In particular, this work suggests oversized shape memory foams may be used to better fill the entire aneurysm cavity while generating stresses below the aneurysm wall breaking stresses.

  19. Estimation of aneurysm wall stresses created by treatment with a shape memory polymer foam device

    PubMed Central

    Hwang, Wonjun; Volk, Brent L.; Akberali, Farida; Singhal, Pooja; Criscione, John C.

    2012-01-01

    In this study, compliant latex thin-walled aneurysm models are fabricated to investigate the effects of expansion of shape memory polymer foam. A simplified cylindrical model is selected for the in-vitro aneurysm, which is a simplification of a real, saccular aneurysm. The studies are performed by crimping shape memory polymer foams, originally 6 and 8 mm in diameter, and monitoring the resulting deformation when deployed into 4-mm-diameter thin-walled latex tubes. The deformations of the latex tubes are used as inputs to physical, analytical, and computational models to estimate the circumferential stresses. Using the results of the stress analysis in the latex aneurysm model, a computational model of the human aneurysm is developed by changing the geometry and material properties. The model is then used to predict the stresses that would develop in a human aneurysm. The experimental, simulation, and analytical results suggest that shape memory polymer foams have potential of being a safe treatment for intracranial saccular aneurysms. In particular, this work suggests oversized shape memory foams may be used to better fill the entire aneurysm cavity while generating stresses below the aneurysm wall breaking stresses. PMID:21901546

  20. Reversible Shape Memory Polymers and Composites: Synthesis, Modeling and Design

    DTIC Science & Technology

    2013-03-01

    Letter, 100, 161908. Photo-origami uses the dynamic control of the molecular architecture of a polymer by a combination of mechanical and non...biological tissue engineering constructs. The fields are essentially actuators, embedded in the material at molecular resolution. Here we...origami.html. It is also featured as one of the APL’s 50th Anniversary Collection: Editor’s Picks of Most Recent Publications. (Left) a) Molecular

  1. Porous TiO₂ surface formed on nickel-titanium alloy by plasma electrolytic oxidation: a prospective polymer-free reservoir for drug eluting stent applications.

    PubMed

    Huan, Zhiguang; Fratila-Apachitei, Lidy E; Apachitei, Iulian; Duszczyk, Jurek

    2013-07-01

    In this study, a porous oxide layer was formed on the surface of nickel-titanium alloy (NiTi) by plasma electrolytic oxidation (PEO) with the aim to produce a polymer-free drug carrier for drug eluting stent (DES) applications. The oxidation was performed galvanostatically in concentrated phosphoric acid electrolyte at low temperature. It was found that the response of NiTi substrate during the PEO process was different from that of bulk Ti, since the presence of large amount of Ni delayed the initial formation of a compact oxide layer that is essential for the PEO to take place. Under optimized PEO conditions, the resultant surface showed porosity, pore density and oxide layer thickness of 14.11%, 2.40 × 10⁵ pores/mm² and 0.8 μm, respectively. It was additionally noted that surface roughness after PEO did not significantly increase as compared with that of original NiTi substrate and the EDS analyses revealed a decrease in Ni/Ti ratio on the surface after PEO. The cross-section morphology showed no discontinuity between the PEO layer and the NiTi substrate. Furthermore, wettability and surface free energy of the NiTi substrate increased significantly after PEO treatment. The PEO process could be successfully translated to NiTi stent configuration proving for the first time its feasibility for such a medical device and offering potential for development of alternative, polymer-free drug carriers for NiTi DES.

  2. High Cycle-life Shape Memory Polymer at High Temperature

    PubMed Central

    Kong, Deyan; Xiao, Xinli

    2016-01-01

    High cycle-life is important for shape memory materials exposed to numerous cycles, and here we report shape memory polyimide that maintained both high shape fixity (Rf) and shape recovery (Rr) during the more than 1000 bending cycles tested. Its critical stress is 2.78 MPa at 250 °C, and the shape recovery process can produce stored energy of 0.218 J g−1 at the efficiency of 31.3%. Its high Rf is determined by the large difference in storage modulus at rubbery and glassy states, while the high Rr mainly originates from its permanent phase composed of strong π-π interactions and massive chain entanglements. Both difference in storage modulus and overall permanent phase were preserved during the bending deformation cycles, and thus high Rf and Rr were observed in every cycle and the high cycle-life will expand application areas of SMPs enormously. PMID:27641148

  3. High Cycle-life Shape Memory Polymer at High Temperature

    NASA Astrophysics Data System (ADS)

    Kong, Deyan; Xiao, Xinli

    2016-09-01

    High cycle-life is important for shape memory materials exposed to numerous cycles, and here we report shape memory polyimide that maintained both high shape fixity (Rf) and shape recovery (Rr) during the more than 1000 bending cycles tested. Its critical stress is 2.78 MPa at 250 °C, and the shape recovery process can produce stored energy of 0.218 J g‑1 at the efficiency of 31.3%. Its high Rf is determined by the large difference in storage modulus at rubbery and glassy states, while the high Rr mainly originates from its permanent phase composed of strong π-π interactions and massive chain entanglements. Both difference in storage modulus and overall permanent phase were preserved during the bending deformation cycles, and thus high Rf and Rr were observed in every cycle and the high cycle-life will expand application areas of SMPs enormously.

  4. Anionic surfactant with hydrophobic and hydrophilic chains for nanoparticle dispersion and shape memory polymer nanocomposites.

    PubMed

    Iijima, Motoyuki; Kobayakawa, Murino; Yamazaki, Miwa; Ohta, Yasuhiro; Kamiya, Hidehiro

    2009-11-18

    An anionic surfactant comprising a hydrophilic poly(ethylene glycol) (PEG) chain, hydrophobic alkyl chain, and polymerizable vinyl group was synthesized as a capping agent of nanoparticles. TiO(2) nanoparticles modified by this surfactant were completely dispersible in various organic solvents with a wide range of polarities, such as nitriles, alcohols, ketones, and acetates. Furthermore, these particles were found to be dispersible in various polymers with different properties, such as thermosetting epoxy resins and radical polymerized poly(methylmethacrylate) (PMMA). A polymer composite of surface-modified TiO(2) nanoparticles in epoxy resins prepared by using the developed surfactant also possessed temperature-induced shape memory properties.

  5. Characterization of origami shape memory metamaterials (SMMM) made of bio-polymer blends

    NASA Astrophysics Data System (ADS)

    Kshad, Mohamed Ali E.; Naguib, Hani E.

    2016-04-01

    Shape memory materials (SMMs) are materials that can return to their virgin state and release mechanically induced strains by external stimuli. Shape memory polymers (SMPs) are a class of SMMs that show a high shape recoverability and which have attractive potential for structural applications. In this paper, we experimentally study the shape memory effect of origami based metamaterials. The main focus is on the Muira origami metamaterials. The fabrication technique used to produce origami structure is direct molding where all the geometrical features are molded from thermally virgin polymers without post folding of flat sheets. The study shows experimental investigations of shape memory metamaterials (SMMMs) made of SMPs that can be used in different applications such as medicine, robotics, and lightweight structures. The origami structure made from SMP blends, activated with uniform heating. The effect of blend composition on the shape memory behavior was studied. Also the influence of the thermomechanical and the viscoelastic properties of origami unit cell on the activation process have been discussed, and stress relaxation and shape recovery were investigated. Activation process of the unit cell has been demonstrated.

  6. Direct Writing of Three-Dimensional Macroporous Photonic Crystals on Pressure-Responsive Shape Memory Polymers.

    PubMed

    Fang, Yin; Ni, Yongliang; Leo, Sin-Yen; Wang, Bingchen; Basile, Vito; Taylor, Curtis; Jiang, Peng

    2015-10-28

    Here we report a single-step direct writing technology for making three-dimensional (3D) macroporous photonic crystal patterns on a new type of pressure-responsive shape memory polymer (SMP). This approach integrates two disparate fields that do not typically intersect: the well-established templating nanofabrication and shape memory materials. Periodic arrays of polymer macropores templated from self-assembled colloidal crystals are squeezed into disordered arrays in an unusual shape memory "cold" programming process. The recovery of the original macroporous photonic crystal lattices can be triggered by direct writing at ambient conditions using both macroscopic and nanoscopic tools, like a pencil or a nanoindenter. Interestingly, this shape memory disorder-order transition is reversible and the photonic crystal patterns can be erased and regenerated hundreds of times, promising the making of reconfigurable/rewritable nanooptical devices. Quantitative insights into the shape memory recovery of collapsed macropores induced by the lateral shear stresses in direct writing are gained through fundamental investigations on important process parameters, including the tip material, the critical pressure and writing speed for triggering the recovery of the deformed macropores, and the minimal feature size that can be directly written on the SMP membranes. Besides straightforward applications in photonic crystal devices, these smart mechanochromic SMPs that are sensitive to various mechanical stresses could render important technological applications ranging from chromogenic stress and impact sensors to rewritable high-density optical data storage media.

  7. Influence of Holding Time on Shape Recovery in a Polyurethane Shape-Memory Polymer

    NASA Astrophysics Data System (ADS)

    Santiago, David; Ferrando, Francesc; De la Flor, Silvia

    2014-07-01

    Shape-memory polymers have attracted a lot of interest in recent years. A shape-memory polymer can be deformed and fixed into a temporary shape and subsequently made to recover its original shape when a suitable stimulus is applied. This is accomplished by means of a thermomechanical cycle called programming. Programming can be performed in a stress- or strain-controlled mode. The thermomechanical conditions of the programming affect shape-memory properties differently in each programming mode. One of the parameters which significantly affects shape-memory properties in a stress-controlled procedure is stress-holding time ( t H) at high temperature. This paper studies how stress-holding time affects the most significant shape-memory properties under successive thermomechanical cycles. The experiments were conducted using two different programming temperatures in the vicinity of the T g. The shape-recovery ratio decreased dramatically with cycling even when the holding time was just a few seconds, however, the impact of the stress-holding time depends on the temperature at which it has been applied. Shape-fixity ratio and switching temperature were also studied, but stress-holding time and successive cycles do not seem to affect either of these factors.

  8. Preparation and characterization of shape memory composite foams with interpenetrating polymer networks

    NASA Astrophysics Data System (ADS)

    Yao, Yongtao; Zhou, Tianyang; Yang, Cheng; Liu, Yanju; Leng, Jinsong

    2016-03-01

    The present study reports a feasible approach of fabricating shape memory composite foams with an interpenetrating polymer network (IPN) based on polyurethane (PU) and shape memory epoxy resin (SMER) via a simultaneous polymerization technique. The PU component is capable of constructing a foam structure and the SMER is grafted on the PU network to offer its shape memory property in the final IPN foams. A series of IPN foams without phase separation were produced due to good compatibility and a tight chemical interaction between PU and SMER components. The relationships of the geometry of the foam cell were investigated via varying compositions of PU and SMER. The physical property and shape memory property were also evaluated. The stimulus temperature of IPN shape memory composite foams, glass temperature (Tg), could be tunable by varying the constituents and Tg of PU and SMER. The mechanism of the shape memory effect of IPN foams has been proposed. The shape memory composite foam with IPN developed in this study has the potential to extend its application field.

  9. Long-term efficacy and safety of biodegradable-polymer biolimus-eluting stents: main results of the Basel Stent Kosten-Effektivitäts Trial-PROspective Validation Examination II (BASKET-PROVE II), a randomized, controlled noninferiority 2-year outcome trial.

    PubMed

    Kaiser, Christoph; Galatius, Soeren; Jeger, Raban; Gilgen, Nicole; Skov Jensen, Jan; Naber, Christoph; Alber, Hannes; Wanitschek, Maria; Eberli, Franz; Kurz, David J; Pedrazzini, Giovanni; Moccetti, Tiziano; Rickli, Hans; Weilenmann, Daniel; Vuillomenet, André; Steiner, Martin; Von Felten, Stefanie; Vogt, Deborah R; Wadt Hansen, Kim; Rickenbacher, Peter; Conen, David; Müller, Christian; Buser, Peter; Hoffmann, Andreas; Pfisterer, Matthias

    2015-01-06

    Biodegradable-polymer drug-eluting stents (BP-DES) were developed to be as effective as second-generation durable-polymer drug-eluting stents (DP-DES) and as safe >1 year as bare-metal stents (BMS). Thus, very late stent thrombosis (VLST) attributable to durable polymers should no longer appear. To address these early and late aspects, 2291 patients presenting with acute or stable coronary disease needing stents ≥3.0 mm in diameter between April 2010 and May 2012 were randomly assigned to biolimus-A9-eluting BP-DES, second-generation everolimus-eluting DP-DES, or thin-strut silicon-carbide-coated BMS in 8 European centers. All patients were treated with aspirin and risk-adjusted doses of prasugrel. The primary end point was combined cardiac death, myocardial infarction, and clinically indicated target-vessel revascularization within 2 years. The combined secondary safety end point was a composite of VLST, myocardial infarction, and cardiac death. The cumulative incidence of the primary end point was 7.6% with BP-DES, 6.8% with DP-DES, and 12.7% with BMS. By intention-to-treat BP-DES were noninferior (predefined margin, 3.80%) compared with DP-DES (absolute risk difference, 0.78%; -1.93% to 3.50%; P for noninferiority 0.042; per protocol P=0.09) and superior to BMS (absolute risk difference, -5.16; -8.32 to -2.01; P=0.0011). The 3 stent groups did not differ in the combined safety end point, with no decrease in events >1 year, particularly VLST with BP-DES. In large vessel stenting, BP-DES appeared barely noninferior compared with DP-DES and more effective than thin-strut BMS, but without evidence for better safety nor lower VLST rates >1 year. Findings challenge the concept that durable polymers are key in VLST formation. http://www.clinicaltrials.gov. Unique identifier: NCT01166685. © 2014 American Heart Association, Inc.

  10. Micro-vascular shape-memory polymer actuators with complex geometries obtained by laser stereolithography

    NASA Astrophysics Data System (ADS)

    Díaz Lantada, Andrés; de Blas Romero, Adrián; Chacón Tanarro, Enrique

    2016-06-01

    In our work we present the complete development process of geometrically complex micro-vascular shape-memory polymer actuators. The complex geometries and three-dimensional networks are designed by means of computer aided design resources. Manufacture is accomplished, in a single step, by means of laser stereolithography, directly from the computer-aided design files with the three dimensional geometries of the different actuators under development. To our knowledge, laser stereolithography is applied here for the first time to the development of shape memory polymer devices with complex geometries and inner micro-vasculatures for their activation using a thermal fluid. Final testing of the developed actuators helps to validate the approach and to put forward some present challenges.

  11. Thermoreversibly crosslinked poly(ε-caprolactone) as recyclable shape-memory polymer network.

    PubMed

    Defize, Thomas; Riva, Raphaël; Raquez, Jean-Marie; Dubois, Philippe; Jérôme, Christine; Alexandre, Michaël

    2011-08-17

    A new concept to build shape memory polymers (SMP) combining outstanding fixity and recovery ratios (both above 99% after only one training cycle) typical of chemically crosslinked SMPs with reprocessability restricted to physically crosslinked SMPs is demonstrated by covalently bonding, through thermoreversible Diels-Alder (DA) adducts, star-shaped poly(ε-caprolactones) (PCL) end-functionalized by furan and maleimide moieties. A PCL network is easily prepared by melt-blending complementary end-functional star polymers in retro DA regime, then by curing at lower temperature to favour the DA cycloaddition. Such covalent network can be reprocessed when heated again at the retro DA temperature. The resulting SMP shows still excellent shape memory properties attesting for its good recyclability. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Shape Memory Polymers from Blends of Elastomers and Crystalline Small Molecules

    NASA Astrophysics Data System (ADS)

    Cavicchi, Kevin; Brostowitz, Nicole; Hukill, Brent; Fairbairn, Heather

    2015-03-01

    This talk will present work on the fabrication of shape memory polymers (SMPs) by swelling natural with molten fatty acids. By this method a SMPs with excellent shape fixity and recovery can be obtained during free recovery after uniaxial deformation to 100% strain. Experiments to measure the shape memory properties under both stress and strain controlled conditions will be reported and compared. This fabrication method offers a number of advantages for preparing SMPs. First, it utilizes natural rubber as the base material for the SMP, which capitalizes on a high performance, commodity elastomer. Second, by blending a commercial polymer with a small molecule additive no additional chemistry is needed for the preparation of the SMP. Third, this route inverts the typically processing steps by crosslinking the permanent network prior to formation of the physically crosslinked reversible network. This offers a means to potentially generate a SMP from any preformed elastomeric article.

  13. Ultra Low Density Shape Memory Polymer Foams With Tunable Physicochemical Properties for Treatment of intracranial Aneurysms

    SciTech Connect

    Singhal, Pooja

    2013-12-01

    Shape memory polymers (SMPs) are a rapidly emerging class of smart materials that can be stored in a deformed temporary shape, and can actively return to their original shape upon application of an external stimulus such as heat, pH or light. This behavior is particularly advantageous for minimally invasive biomedical applications comprising embolic/regenerative scaffolds, as it enables a transcatheter delivery of the device to the target site. The focus of this work was to exploit this shape memory behavior of polyurethanes, and develop an efficient embolic SMP foam device for the treatment of intracranial aneurysms.In summary, this work reports a novel family of ultra low density polymer foams which can be delivered via a minimally invasive surgery to the aneurysm site, actuated in a controlled manner to efficiently embolize the aneurysm while promoting physiological fluid/blood flow through the reticulated/open porous structure, and eventually biodegrade leading to complete healing of the vasculature.

  14. Damage healing ability of a shape-memory-polymer-based particulate composite with small thermoplastic contents

    NASA Astrophysics Data System (ADS)

    Nji, Jones; Li, Guoqiang

    2012-02-01

    The purpose of this study is to investigate the potential of a shape-memory-polymer (SMP)-based particulate composite to heal structural-length scale damage with small thermoplastic additive contents through a close-then-heal (CTH) self-healing scheme that was introduced in a previous study (Li and Uppu 2010 Comput. Sci. Technol. 70 1419-27). The idea is to achieve reasonable healing efficiencies with minimal sacrifice in structural load capacity. By first closing cracks, the gap between two crack surfaces is narrowed and a lesser amount of thermoplastic particles is required to achieve healing. The particulate composite was fabricated by dispersing copolyester thermoplastic particles in a shape memory polymer matrix. It is found that, for small thermoplastic contents of less than 10%, the CTH scheme followed in this study heals structural-length scale damage in the SMP particulate composite to a meaningful extent and with less sacrifice of structural capacity.

  15. Polymer ferroelectric field-effect memory device with SnO channel layer exhibits record hole mobility

    NASA Astrophysics Data System (ADS)

    Caraveo-Frescas, J. A.; Khan, M. A.; Alshareef, H. N.

    2014-06-01

    Here we report for the first time a hybrid p-channel polymer ferroelectric field-effect transistor memory device with record mobility. The memory device, fabricated at 200°C on both plastic polyimide and glass substrates, uses ferroelectric polymer P(VDF-TrFE) as the gate dielectric and transparent p-type oxide (SnO) as the active channel layer. A record mobility of 3.3 cm2V-1s-1, large memory window (~16 V), low read voltages (~-1 V), and excellent retention characteristics up to 5000 sec have been achieved. The mobility achieved in our devices is over 10 times higher than previously reported polymer ferroelectric field-effect transistor memory with p-type channel. This demonstration opens the door for the development of non-volatile memory devices based on dual channel for emerging transparent and flexible electronic devices.

  16. First-in-man randomised comparison of a novel sirolimus-eluting stent with abluminal biodegradable polymer and thin-strut cobalt-chromium alloy: INSPIRON-I trial.

    PubMed

    Ribeiro, Expedito E; Campos, Carlos M; Ribeiro, Henrique B; Lopes, Augusto C; Esper, Rodrigo B; Meirelles, George X; Perin, Marco A; Abizaid, Alexandre; Lemos, Pedro A

    2014-01-01

    The INSPIRON-I trial is a first-in-man evaluation of the safety and efficacy of the Inspiron drug-eluting stent, a sirolimus-eluting stent with abluminal biodegradable polymer coating and thin cobalt-chromium alloy. This is a randomised, multicentre comparison between Inspiron and a stent with the same metallic structure but without polymer coating or drug elution (Cronus). The primary objective was to evaluate the in-segment late loss (LLL) at six months. Secondary endpoints included percent in-stent obstruction as measured by intravascular ultrasound (IVUS) at six months and major adverse cardiac events (MACE). Fifty-eight patients were enrolled (60 lesions), 39 for Inspiron and 19 for Cronus. Baseline clinical and angiographic characteristics of both groups were similar. At six months, the in-segment LLL was reduced in the Inspiron group compared to the control group (0.19±0.16 mm vs. 0.58±0.4 mm, respectively; p<0.001), as well as the percent neointimal obstruction (7.8±7.1% vs. 26.5±11.4%; p<0.001). At two-year follow-up, incidence of MACE was similar between groups (7.9 vs. 21.1%, respectively; p=0.20), with lower target lesion revascularisation for Inspiron (0 vs. 21.1%, respectively; p=0.01) and no stent thrombosis. Sirolimus eluted from an abluminal biodegradable polymer on a cobalt-chromium alloy proved effective in reducing restenosis at six months.

  17. Thermoplastic High Strain Multishape Memory Polymer: Side-Chain Polynorbornene with Columnar Liquid Crystalline Phase.

    PubMed

    Zhao, Ruiying; Zhao, Tipeng; Jiang, Xuqiang; Liu, Xin; Shi, Dong; Liu, Chenyang; Yang, Shuang; Chen, Er-Qiang

    2017-03-01

    A thermoplastic high strain multishape memory polymer can be fabricated using a hemiphasmid side-chain polynorbornene (P1) with hexagonal columnar liquid crystalline (ΦH ) phase. Without any chemical crosslinks, P1 can memorize multiple temporary shapes with high strain and exhibit excellent shape fixity and shape recovery. As the building blocks of ΦH , the multichain columns in P1 act as robust physical crosslinks. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. A preliminary study on anti-irradiation performance of epoxy shape memory polymer

    NASA Astrophysics Data System (ADS)

    Wu, Xuelian; Liu, Yanju; Leng, Jinsong

    2009-07-01

    As a new class of smart material, shape memory polymer (SMP) receives more and more attention. In this paper, in addition to the fabrication of a new type of epoxy SMP, the thermo-mechanical properties of the polymer with/without gamma irradiation were investigated and compared systematically. The radiation source is Co-60 and the total dosage of radiation is 1×104Gy. Changes of network structures of the polymer were investigated by Fourier Transform Infrared (FTIR) spectroscopy. The influence of gamma irradiation on thermo and mechanical properties of the polymer were investigated by Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analysis (DMA) and tensile test, respectively. Furthermore, shape recovery behaviors of the polymer before/after the irradiation were compared too. Results show that the epoxy SMP possesses good chemical stability, glass transition temperature (Tg) determined by DSC decreased by 7°C after the irradiation. The gamma radiation has a slight influence on storage modulus, loss modulus and tan delta, respectively. No considerable change was found both in tensile strength and elongation at break after the gamma radiation. Finally, the shape recovery ratio of the polymer is near 100% with and without the gamma irradiation. Based on the above results, it can be demonstrated that the epoxy SMP prepared in the study possesses not only good thermo-mechanical properties but unique anti irradiation performance. The epoxy SMP shows potential for application of aerospace fields.

  19. High performance shape memory polymer networks based on rigid nanoparticle cores

    PubMed Central

    Song, Jie

    2010-01-01

    Smart materials that can respond to external stimuli are of widespread interest in biomedical science. Thermal-responsive shape memory polymers, a class of intelligent materials that can be fixed at a temporary shape below their transition temperature (Ttrans) and thermally triggered to resume their original shapes on demand, hold great potential as minimally invasive self-fitting tissue scaffolds or implants. The intrinsic mechanism for shape memory behavior of polymers is the freezing and activation of the long-range motion of polymer chain segments below and above Ttrans, respectively. Both Ttrans and the extent of polymer chain participation in effective elastic deformation and recovery are determined by the network composition and structure, which are also defining factors for their mechanical properties, degradability, and bioactivities. Such complexity has made it extremely challenging to achieve the ideal combination of a Ttrans slightly above physiological temperature, rapid and complete recovery, and suitable mechanical and biological properties for clinical applications. Here we report a shape memory polymer network constructed from a polyhedral oligomeric silsesquioxane nanoparticle core functionalized with eight polyester arms. The cross-linked networks comprising this macromer possessed a gigapascal-storage modulus at body temperature and a Ttrans between 42 and 48 °C. The materials could stably hold their temporary shapes for > 1 year at room temperature and achieve full shape recovery ≤ 51 °C in a matter of seconds. Their versatile structures allowed for tunable biodegradability and biofunctionalizability. These materials have tremendous promise for tissue engineering applications. PMID:20375285

  20. Towards Low-Cost Effective and Homogeneous Thermal Activation of Shape Memory Polymers

    PubMed Central

    Lantada, Andrés Díaz; Rebollo, María Ángeles Santamaría

    2013-01-01

    A typical limitation of intelligent devices based on the use of shape-memory polymers as actuators is linked to the widespread use of distributed heating resistors, via Joule effect, as activation method, which involves several relevant issues needing attention, such as: (a) Final device size is importantly increased due to the additional space required for the resistances; (b) the use of resistances limits materials’ strength and the obtained devices are normally weaker; (c) the activation process through heating resistances is not homogeneous, thus leading to important temperature differences among the polymeric structure and to undesirable thermal gradients and stresses, also limiting the application fields of shape-memory polymers. In our present work we describe interesting activation alternatives, based on coating shape-memory polymers with different kinds of conductive materials, including textiles, conductive threads and conductive paint, which stand out for their easy, rapid and very cheap implementation. Distributed heating and homogeneous activation can be achieved in several of the alternatives studied and the technical results are comparable to those obtained by using advanced shape-memory nanocomposites, which have to deal with complex synthesis, processing and security aspects. Different combinations of shape memory epoxy resin with several coating electrotextiles, conductive films and paints are prepared, simulated with the help of thermal finite element method based resources and characterized using infrared thermography for validating the simulations and overall design process. A final application linked to an active catheter pincer is detailed and the advantages of using distributed heating instead of conventional resistors are discussed. PMID:28788401

  1. Opto-electronic characterization of electron traps upon forming polymer oxide memory diodes

    NASA Astrophysics Data System (ADS)

    Chen, Qian; Bory, Benjamin F.; Kiazadeh, Asal; Rocha, Paulo R. F.; Gomes, Henrique L.; Verbakel, Frank; De Leeuw, Dago M.; Meskers, Stefan C. J.

    2011-08-01

    Metal-insulator-polymer diodes where the insulator is a thin oxide (Al2O3) layer are electroformed by applying a high bias. The initial stage is reversible and involves trapping of electrons near the oxide/polymer interface. The rate of charge trapping is limited by electron transport through the polymer. Detrapping of charge stored can be accomplished by illuminating with light under short-circuit conditions. The amount of stored charge is determined from the optically induced discharging current transient as a function of applied voltage and oxide thickness. When the charge density exceeds 8 × 1017/m2, an irreversible soft breakdown transition occurs to a non-volatile memory diode.

  2. Shape-Memory Polymers Based on Fatty Acid-Filled Elastomeric Ionomers

    NASA Astrophysics Data System (ADS)

    Izzo, Elise; Weiss, Robert

    2009-03-01

    Shape memory polymers (SMPs) have applications as medical devices, actuators, sensors, artificial muscles, switches, smart textiles, and self-deployable structures. All previous design of SMPs has involved synthesizing new polymers or modifying existing polymers. This paper describes a new type of SMP based on blends of an elastomeric ionomer and low molar mass fatty acids or their salts (FAS). Shape memory elastomers were prepared from mixtures of a sulfonated EPDM ionomer and various amounts of a FAS (e.g., zinc stearate, zinc oleate, and various aliphalic acids). Nanophase separation of the metal sulfonate groups provided the ``permanent'' crosslinks, while sub-microscopic crystals of the low molecular weight FAS provided a physical crosslink needed for the temporary shape. The material was deformed above the melting point of the FAS and the new shape was fixed by cooling the material while under stress to below the melting point of the FAS. Polar interactions between the ionomer and the FAS stabilized the dispersion of the FAS in the polymer and provided the continuity between the phases that allowed the crystals of the FAS to provide a second network of physical crosslinks. The temporary shape was erased and the material returned to the primary shape by heating above the melting point of the FAS.

  3. Thermally responsive polymer systems for self-healing, reversible adhesion and shape memory applications

    NASA Astrophysics Data System (ADS)

    Luo, Xiaofan

    Responsive polymers are "smart" materials that are capable of performing prescribed, dynamic functions under an applied stimulus. In this dissertation, we explore several novel design strategies to develop thermally responsive polymers and polymer composites for self-healing, reversible adhesion and shape memory applications. In the first case described in Chapters 2 and 3, a thermally triggered self-healing material was prepared by blending a high-temperature epoxy resin with a thermoplastic polymer, poly(epsilon-caprolactone) (PCL). The initially miscible system undergoes polymerization induced phase separation (PIPS) during the curing of epoxy and yields a variety of compositionally dependent morphologies. At a particular PCL loading, the cured blend displays a "bricks-and-mortar" morphology in which epoxy exists as interconnected spheres ("bricks") within a continuous PCL matrix ("mortar"). A heat induced "bleeding" phenomenon was observed in the form of spontaneous wetting of all free surfaces by the molten PCL, and is attributed to the volumetric thermal expansion of PCL above its melting point in excess of epoxy brick expansion, which we term differential expansive bleeding (DEB). This DEB is capable of healing damage such as cracks. In controlled self-healing experiments, heating of a cracked specimen led to PCL bleeding from the bulk that yields a liquid layer bridging the crack gap. Upon cooling, a "scar" composed of PCL crystals was formed at the site of the crack, restoring a significant portion of mechanical strength. We further utilized DEB to enable strong and thermally-reversible adhesion of the material to itself and to metallic substrates, without any requirement for macroscopic softening or flow. After that, Chapters 4--6 present a novel composite strategy for the design and fabrication of shape memory polymer composites. The basic approach involves physically combining two or more functional components into an interpenetrating fiber

  4. Investigation of buckling behavior of carbon nanotube/shape memory polymer composite shell

    NASA Astrophysics Data System (ADS)

    Shi, Guanghui; Yang, Qingsheng; Zhang, Qiang

    2012-04-01

    Shape memory polymer(SMP) is a class of smart materials used in intelligent biomedical devices and industrial application as sensors or actuators for their ability to change shape under a predetermined stimulus. Carbon nanotube (CNT)/shape memory polymer (SMP) composites demonstrate good mechanical properties and shape memory effect. In this work, a model of CNT/SMP composite shell with a vaulted cross-section was established. This composite shell structure could further elevate the recovery stress of CNT/SMP composites. The folding properties of CNT/SMP composite shell structure were analyzed by finite element method and the influence of structural parameters on the buckling behavior of the shell was studied using the energy conservation principle. The results indicate that vaulted cross-section shell had unique mechanical properties. The structural parameters, such as the vaulted radius and the total length have a great impact on buckling moment of the shell. This shell structure is expected to achieve effective control of buckling and deploying process, relying on the special shape memory property of SMP and high elastic modulus CNTs. Moreover, it could also largely avoid the vibration problem during the deploying process.

  5. Investigation of buckling behavior of carbon nanotube/shape memory polymer composite shell

    NASA Astrophysics Data System (ADS)

    Shi, Guanghui; Yang, Qingsheng; Zhang, Qiang

    2011-11-01

    Shape memory polymer(SMP) is a class of smart materials used in intelligent biomedical devices and industrial application as sensors or actuators for their ability to change shape under a predetermined stimulus. Carbon nanotube (CNT)/shape memory polymer (SMP) composites demonstrate good mechanical properties and shape memory effect. In this work, a model of CNT/SMP composite shell with a vaulted cross-section was established. This composite shell structure could further elevate the recovery stress of CNT/SMP composites. The folding properties of CNT/SMP composite shell structure were analyzed by finite element method and the influence of structural parameters on the buckling behavior of the shell was studied using the energy conservation principle. The results indicate that vaulted cross-section shell had unique mechanical properties. The structural parameters, such as the vaulted radius and the total length have a great impact on buckling moment of the shell. This shell structure is expected to achieve effective control of buckling and deploying process, relying on the special shape memory property of SMP and high elastic modulus CNTs. Moreover, it could also largely avoid the vibration problem during the deploying process.

  6. Parametric analysis and temperature effect of deployable hinged shells using shape memory polymers

    NASA Astrophysics Data System (ADS)

    Tao, Ran; Yang, Qing-Sheng; He, Xiao-Qiao; Liew, Kim-Meow

    2016-11-01

    Shape memory polymers (SMPs) are a class of intelligent materials, which are defined by their capacity to store a temporary shape and recover an original shape. In this work, the shape memory effect of SMP deployable hinged shell is simulated by using compiled user defined material subroutine (UMAT) subroutine of ABAQUS. Variations of bending moment and strain energy of the hinged shells with different temperatures and structural parameters in the loading process are given. The effects of the parameters and temperature on the nonlinear deformation process are emphasized. The entire thermodynamic cycle of SMP deployable hinged shell includes loading at high temperature, load carrying with cooling, unloading at low temperature and recovering the original shape with heating. The results show that the complicated thermo-mechanical deformation and shape memory effect of SMP deployable hinge are influenced by the structural parameters and temperature. The design ability of SMP smart hinged structures in practical application is prospected.

  7. [Absorbable coronary stents. New promising technology].

    PubMed

    Erbel, Raimund; Böse, Dirk; Haude, Michael; Kordish, Igor; Churzidze, Sofia; Malyar, Nasser; Konorza, Thomas; Sack, Stefan

    2007-06-01

    Coronary stent implantation started in Germany 20 years ago. In the beginning, the progress was very slow and accelerated 10 years later. Meanwhile, coronary stent implantation is a standard procedure in interventional cardiology. From the beginning of permanent stent implantation, research started to provide temporary stenting of coronary arteries, first with catheter-based systems, later with stent-alone technology. Stents were produced from polymers or metal. The first polymer stent implantation failed except the Igaki-Tamai stent in Japan. Newly developed absorbable polymer stents seem to be very promising, as intravascular ultrasound (IVUS) and optical coherence tomography have demonstrated. Temporary metal stents were developed based on iron and magnesium. Currently, the iron stent is tested in peripheral arteries. The absorbable magnesium stent (Biotronik, Berlin, Germany) was tested in peripheral arteries below the knee and meanwhile in the multicenter international PROGRESS-AMS (Clinical Performance and Angiographic Results of Coronary Stenting with Absorbable Metal Stents) study. The first magnesium stent implantation was performed on July 30, 2004 after extended experimental testing in Essen. The magnesium stent behaved like a bare-metal stent with low recoil of 5-7%. The stent struts were absorbed when tested with IVUS. Stent struts were not visible by fluoroscopy or computed tomography (CT) as well as magnetic resonance imaging (MRI). That means, that the magnesium stent is invisible and therefore CT and MRI can be used for imaging of interventions. Only using micro-CT the stent struts were visible. The absorption process could be demonstrated in a patient 18 days after implantation due to suspected acute coronary syndrome, which was excluded. IVUS showed a nice open lumen. Stent struts were no longer visible, but replaced by tissue indicating the previous stent location. Coronary angiography after 4 months showed an ischemia-driven target lesion

  8. Four-year clinical follow-up of the first-in-man randomized comparison of a novel sirolimus eluting stent with abluminal biodegradable polymer and ultra-thin strut cobalt-chromium alloy: the INSPIRON-I trial

    PubMed Central

    Oliveira, Marcos Danillo Peixoto; Ribeiro, Expedito E.; Campos, Carlos M.; Ribeiro, Henrique B.; Faillace, Bruno L. R.; Lopes, Augusto C.; Esper, Rodrigo B.; Meirelles, George X.; Perin, Marco A.; Abizaid, Alexandre

    2015-01-01

    Background The Inspiron™ sirolimus-eluting stent (SES) is a low-dose, ultra-thin-strut cobalt-chromium stent abluminally coated with biodegradable polymers (BP). Previous results from the INSPIRON-I trial, a first-in-man study, have proven the efficacy of the novel stent in reducing neointimal proliferation. The present report aims at evaluating the long-term clinical outcomes of patients enrolled into the INSPIRON-I trial (Clinical Trials Gov. identifier: NCT01093391). Methods A total of 57 patients (60 lesions) were randomly allocated in a 2:1 ratio to treatment with the Inspiron™ SES vs. its equivalent Cronus™ bare metal stent (BMS, both by Scitech Medical™, Aparecida de Goiânia, Goiás, Brazil), in four tertiary centers. The primary endpoint of the present analysis was the occurrence of major adverse cardiac events (MACE) [death, myocardial infarction (MI), target vessel revascularization (TVR) and/or target lesion revascularization (TLR)] at 4 years. Results Baseline clinical and angiographic characteristics of both groups were similar. After 4 years, the primary endpoint occurred in 7.9% vs. 23.5% of patients in Inspiron and control groups respectively (P=0.11). The rate of death/MI was similar between the groups, but there was a significant decrease in the risk of repeat revascularization in the Inspiron group compared to the control arm TLR (0.0% vs. 23.5% respectively, P=0.02). There were no stent thromboses in the study population. Conclusions The novel Inspiron™ SES showed a sustained safe and effective clinical profile after 4-year of follow-up, with very low adverse events and null stent thrombosis (ST) occurrence. PMID:26331110

  9. Thermo-mechanical modeling of semi-crystalline thermoplastic shape memory polymer under large strain

    NASA Astrophysics Data System (ADS)

    Bouaziz, R.; Roger, F.; Prashantha, K.

    2017-05-01

    In this work, a constitutive mechanical model is proposed to describe the thermo-mechanical cycle of a semi-crystalline shape memory polyurethane which is able to recover its initial shape after applying more than 100% strain during a shape memory cycle. To explore this performance, experimental tests were conducted to determine the cyclic thermo-mechanical behavior of a polymer submitted to five shape memory cycles. Indeed, uniaxial tensile tests at small strain rates were performed at 60 °C in order to analyze its hyper-elastic response. At the end of the previous tensile loading, relaxation tests were carried out to determine the viscoelastic behavior during the shape memory cycle. The shape memory effect was investigated by means of free and constrained recovery experiments. These experimental results are used to identify the parameters of the constitutive model by means of curve-fitting algorithm employing least-squares optimization approach. The proposed model is then implemented in the finite element software Comsol Multiphysics© and predicts quite well an in-plane strained cylindrical ring.

  10. Biocompatible electrically conductive nanofibers from inorganic-organic shape memory polymers.

    PubMed

    Kai, Dan; Tan, Mein Jin; Prabhakaran, Molamma P; Chan, Benjamin Qi Yu; Liow, Sing Shy; Ramakrishna, Seeram; Loh, Xian Jun

    2016-12-01

    A porous shape memory scaffold with both biomimetic structures and electrical conductivity properties is highly promising for nerve tissue engineering applications. In this study, a new shape memory polyurethane polymer which consists of inorganic polydimethylsiloxane (PDMS) segments with organic poly(ε-caprolactone) (PCL) segments was synthesized. Based on this poly(PCL/PDMS urethane), a series of electrically conductive nanofibers were electrospun by incorporating different amounts of carbon-black. Our results showed that after adding carbon black into nanofibers, the fiber diameters increased from 399±76 to 619±138nm, the crystallinity decreased from 33 to 25% and the resistivity reduced from 3.6 GΩ/mm to 1.8 kΩ/mm. Carbon black did not significantly influence the shape memory properties of the resulting nanofibers, and all the composite nanofibers exhibited decent shape recovery ratios of >90% and shape fixity ratios of >82% even after 5 thermo-mechanical cycles. PC12 cells were cultured on the shape memory nanofibers and the composite scaffolds showed good biocompatibility by promoting cell-cell interactions. Our study demonstrated that the poly(PCL/PDMS urethane)/carbon-black nanofibers with shape memory properties could be potentially used as smart 4-dimensional (4D) scaffolds for nerve tissue regeneration. Copyright © 2016 Elsevier B.V. All rights reserved.

  11. A New Strategy to Prepare Polymer-based Shape Memory Elastomers.

    PubMed

    Song, Shijie; Feng, Jiachun; Wu, Peiyi

    2011-10-04

    A new strategy that utilizes the microphase separation of block copolymer and phase transition of small molecules for preparing polymer-based shape memory elastomer has been proposed. According to this strategy, a novel kind of shape memory elastomer comprising styrene-b-(ethylene-co-butylene)-b-styrene (SEBS) and paraffin has been prepared. Because paraffins are midblock-selective molecules for SEBS, they will preferentially enter and swell EB blocks supporting paraffins as an excellent switch phase for shape memory effect. Microstructures of SEBS/paraffin composites have been characterized by transmission electron microscopy, polarized light microscopy, and differential scanning calorimetry. The composites demonstrate various phase morphologies with regard to different paraffin loading. It has been found that under low paraffin loading, all the paraffins precisely embed in and swell EB-rich domains. While under higher loading, part of the paraffins become free and a larger-scaled phase separation has been observed. However, within wide paraffin loadings, all composites show good shape fixing, shape recovery performances, and improved tensile properties. Compared to the reported methods for shape memory elastomers preparation, this method not only simplifies the fabrication procedure from raw materials to processing but also offers a controllable approach for the optimization of shape memory properties as well as balancing the rigidity and softness of the material.

  12. Crosslinkable high k polymer dielectrics for low voltage organic field-effect transistor memories (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Wu, Hung-Chin; Hung, Chih-Chien; Chiu, Yu-Cheng; Tung, Shih-Huang; Chen, Wen-Chang

    2016-09-01

    High Performance organic field-effect transistor (OFET) memory devices were successfully prepared using new dielectric materials, poly(N-(hydroxymethyl)acrylamide-co-5 -(9-(5-(diethylamino)pentyl)-2-(4-vinylphenyl)-9H-fluorene (P(NMA-co-F6NSt)), which contained chemical cross-linkable segment (NMA) and hole trapping building block (F6NSt). The high k characteristics of P(NMA-co-F6NSt)) led to a low voltage operation, a small power consumption, and a good digital information storage capacity. Such P(NMA-co-F6NSt) dielectrics in OFET memories with variant NMA/F6NSt molar ratios (100/0 (P1), 95/5 (P2), 80/20 (P3), and 67/33 (P4)) showed excellent insulating properties and good charge storage performance under a low operating voltage below ±5V, due to the tightly network structures after crosslinking and well-dispersed trapping cites (i.e. fluorene moieties). P3-based memory device, in particular, exhibited largest memory window of 4.13 V among the studied polymers, and possessed stable data retention stability over 104 s with a high on/off current ratio (i.e. 104) and good endurance characteristics of more than 200 write-read-write-erase (WRER) cycles. The above results suggested that a high-performance OFET memory device could be facilely achieved using the novel synthesized high-k copolymers.

  13. Design and verification of a shape memory polymer peripheral occlusion device.

    PubMed

    Landsman, Todd L; Bush, Ruth L; Glowczwski, Alan; Horn, John; Jessen, Staci L; Ungchusri, Ethan; Diguette, Katelin; Smith, Harrison R; Hasan, Sayyeda M; Nash, Daniel; Clubb, Fred J; Maitland, Duncan J

    2016-10-01

    Shape memory polymer foams have been previously investigated for their safety and efficacy in treating a porcine aneurysm model. Their biocompatibility, rapid thrombus formation, and ability for endovascular catheter-based delivery to a variety of vascular beds makes these foams ideal candidates for use in numerous embolic applications, particularly within the peripheral vasculature. This study sought to investigate the material properties, safety, and efficacy of a shape memory polymer peripheral embolization device in vitro. The material characteristics of the device were analyzed to show tunability of the glass transition temperature (Tg) and the expansion rate of the polymer to ensure adequate time to deliver the device through a catheter prior to excessive foam expansion. Mechanical analysis and flow migration studies were performed to ensure minimal risk of vessel perforation and undesired thromboembolism upon device deployment. The efficacy of the device was verified by performing blood flow studies that established affinity for thrombus formation and blood penetration throughout the foam and by delivery of the device in an ultrasound phantom that demonstrated flow stagnation and diversion of flow to collateral pathways. Copyright © 2016 Elsevier Ltd. All rights reserved.

  14. Design and Verification of a Shape Memory Polymer Peripheral Occlusion Device

    PubMed Central

    Landsman, Todd L.; Bush, Ruth L.; Glowczwski, Alan; Horn, John; Jessen, Staci L.; Ungchusri, Ethan; Diguette, Katelin; Smith, Harrison R.; Hasan, Sayyeda M.; Nash, Daniel; Clubb, Fred J.; Maitland, Duncan J.

    2017-01-01

    Shape memory polymer foams have been previously investigated for their safety and efficacy in treating a porcine aneurysm model. Their biocompatibility, rapid thrombus formation, and ability for endovascular catheter-based delivery to a variety of vascular beds makes these foams ideal candidates for use in numerous embolic applications, particularly within the peripheral vasculature. This study sought to investigate the material properties, safety, and efficacy of a shape memory polymer peripheral embolization device in vitro. The material characteristics of the device were analyzed to show tunability of the glass transition temperature (Tg) and the expansion rate of the polymer to ensure adequate time to deliver the device through a catheter prior to excessive foam expansion. Mechanical analysis and flow migration studies were performed to ensure minimal risk of vessel perforation and undesired thromboembolism upon device deployment. The efficacy of the device was verified by performing blood flow studies that established affinity for thrombus formation and blood penetration throughout the foam and by delivery of the device in an ultrasound phantom that demonstrated flow stagnation and diversion of flow to collateral pathways. PMID:27419615

  15. Fast Triggering of Shape Memory Polymers using an Embedded Carbon Nanotube Sponge Network

    PubMed Central

    Zhou, Guoxiang; Zhang, Heng; Xu, Shuping; Gui, Xuchun; Wei, Hongqiu; Leng, Jinsong; Koratkar, Nikhil; Zhong, Jing

    2016-01-01

    In this work, a 3-D porous carbon nanotube sponge (CNTS) was embedded within a shape memory polymer (SMPs) matrix. We demonstrate complete infiltration and filling of the SMPs into the CNTS by capillary force without any damage to the CNTS structure. With only ~0.2 wt% carbon nanotube loading, the glass transition temperature is increased by ~20 °C, indicating strong interaction between CNTS and the SMPs matrix. Further, we find that the uniform distribution of the carbon nanotubes in the nanocomposite results in high electrical conductivity, and thus highly effective electricity triggering capability. The carbon nanotube sponge shape memory polymer (CNTS/SMPs) nanocomposite could be triggered within ~10 seconds by the application of ~10 volts. Results from finite element simulations showed good agreement with the experimental results, and indicated that for our system the interface thermal energy loss does not have a significant effect on the heating rate of the polymer matrix. PMID:27052451

  16. New design strategy for reversible plasticity shape memory polymers with deformable glassy aggregates.

    PubMed

    Lin, Tengfei; Tang, Zhenghai; Guo, Baochun

    2014-12-10

    Reversible plasticity shape memory (RPSM) is a new concept in the study of shape memory performance behavior and describes a phenomenon in which shape memory polymers (SMPs) can undergo a large plastic deformation at room temperature and subsequently recover their original shape upon heating. To date, RPSM behavior has been demonstrated in only a few polymers. In the present study, we implement a new design strategy, in which deformable glassy hindered phenol (AO-80) aggregates are incorporated into an amorphous network of epoxidized natural rubber (ENR) cured with zinc diacrylate (ZDA), in order to achieve RPSM properties. We propose that AO-80 continuously tunes the glass transition temperature (Tg) and improves the chain mobility of the SMP, providing traction and anchoring the ENR chains by intermolecular hydrogen bonding interactions. The RPSM behavior of the amorphous SMPs is characterized, and the results demonstrate good fixity at large deformations (up to 300%) and excellent recovery upon heating. Large energy storage capacities at Td in these RPSM materials are demonstrated compared with those achieved at elevated temperature in traditional SMPs. Interestingly, the further revealed self-healing properties of these materials are closely related to their RPSM behavior.

  17. Intelligent structures based on the improved activation of shape memory polymers using Peltier cells

    NASA Astrophysics Data System (ADS)

    Díaz Lantada, Andrés; Lafont Morgado, Pilar; Muñoz Sanz, José Luis; Muñoz García, Julio; Munoz-Guijosa, Juan Manuel; Echávarri Otero, Javier

    2010-05-01

    This study is focused on obtaining intelligent structures manufactured from shape memory polymers possessing the ability to change their geometry in successive or 'step-by-step' actions. This objective has been reached by changing the conventionally used shape memory activation systems (heating resistance, laser or induction heating). The solution set out consists in using Peltier cells as a heating system capable of heating (and activating) a specific zone of the device in the first activation, while the opposite zone keeps its original geometry. By carefully reversing the polarity of the electrical supply to the Peltier cell, in the second activation, the as yet unchanged zone is activated while the already changed zone in the first activation remains unaltered. We have described the criteria for the selection, calibration and design of this alternative heating (activation) system based on the thermoelectric effect, together with the development of different 'proof of concept' prototypes that have enabled us to validate the concepts put forward, as well as suggest future improvements for 'intelligent' shape memory polymer-based devices.

  18. [Pyeloureteral stenting using nitinol stents].

    PubMed

    Guliev, B G; Zagazezhev, A M

    2016-11-01

    To test the effectiveness of nitinol stents in restoring patency of pyeloureteral segment (PUS). Endoureteral nitinol stents were used in 54 patients. The indications for stenting were recurrent strictures of upper urinary tract and ureteral tumor obstruction in 34 and 20 patients, respectively. In 9 (16.6%) of them, including 4 women and 5 men aged 28-65 years, stenting was performed for extensive recurrent PUS strictures. In 8 patients extensive strictures resulted from various surgical interventions on the PUS. In 2 patients, PUS narrowing was caused by open pyelolithotomy, in 6 patients by pyeloplasty, both open (4) and laparoscopic (2). A female patient with solitary right kidney and Bourneville - Pringle disease of the PUS received two metal prostheses. In all cases, nitinol stents were adequately installed in PUS. Hematuria was observed in 1 patient. During the follow-up period of 8 to 60 months, the results of stenting were considered good in 6 (66.7%) and satisfactory in 2 (22.2%) patients. At month 10, 1 (11.1%) patient developed the stent obstruction by proliferative tissue and underwent ureteroscopy with recanalization of the nitinol stent. The patient with Bourneville - Pringle disease was found to have a stone formed in the renal pelvic end of the endoprosthesis; she underwent percutaneous nephrolithotripsy. In another patient a lower calyceal stone migrated and wedged into the proximal end of the stent. The stone was extracted using percutaneous nephroscopy. Pyeloureteral stenting is an effective method to restore patency of the PUS in patients with extensive recurrent strictures. For adequate functioning of the stents, they need to be of optimal length and correctly installed.

  19. Five-year outcomes of ST-elevation myocardial infarction versus non-ST-elevation acute coronary syndrome treated with biodegradable polymer-coated sirolimus-eluting stents: Insights from the CREATE trial.

    PubMed

    Liu, Hui-Liang; Jin, Zhi-Geng; Yang, Sheng-Li; Han, Wei; Jing, Quan-Min; Zhang, Lei; Luo, Jian-Ping; Ma, Dong-Xing; Liu, Ying; Yang, Li-Xia; Jiang, Tie-Min; Qu, Peng; Li, Wei-Min; Li, Shu-Mei; Xu, Bo; Gao, Run-Lin; Han, Ya-Ling

    2017-01-01

    Long-term outcome of drug-eluting stents (DES) for ST-elevation myocardial infarction (STEMI) versus non-ST-elevation acute coronary syndrome (NSTE-ACS) remains unclear. This study sought to compare the long-term outcomes of biodegradable polymer-coated DES in patients with STEMI versus NSTE-ACS. We explored a post hoc analysis of the 5-year outcome of the CREATE trial in the subgroup of patients with STEMI (n=318) versus NSTE-ACS (n=1223) who were implanted with biodegradable polymer-coated DES. The primary outcome was the rate of major adverse cardiac events (MACE) at 5 years. Clopidogrel and aspirin for 6 months followed by chronic aspirin therapy were recommended. STEMI patients showed a trend of increase in MACE (8.7% vs. 6.8%, log rank p=0.289) compared to NSTE-ACS patients at 5 years, and a greater risk of cardiac death (5.4% vs. 2.1%, log rank p=0.003), mainly driven by the higher cardiac death rate within the first month after stent placement (log rank p=0.003) and the last year of follow-up (log rank p=0.001). No significant difference in stent thrombosis was found between them (3.1% vs. 2.5%, log rank p=0.653). Prolonged clopidogrel therapy (>6 months) showed no effect on risk of MACE or stent thrombosis between the two groups (both p for interaction >0.1). STEMI patients have a higher risk of cardiac mortality compared with NSTE-ACS patients after biodegradable polymer-coated DES placement, primarily attribute to more cardiac deaths that happened within the first month after the event and the last year of follow-up. Copyright © 2016 Japanese College of Cardiology. Published by Elsevier Ltd. All rights reserved.

  20. Ordered arrays of a defect-modified ferroelectric polymer for non-volatile memory with minimized energy consumption

    NASA Astrophysics Data System (ADS)

    Chen, Xiang-Zhong; Chen, Xin; Guo, Xu; Cui, Yu-Shuang; Shen, Qun-Dong; Ge, Hai-Xiong

    2014-10-01

    Ferroelectric polymers are among the most promising materials for flexible electronic devices. Highly ordered arrays of the defect-modified ferroelectric polymer P(VDF-TrFE-CFE) (poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene)) are fabricated by nanoimprint lithography for nonvolatile memory application. The defective CFE units reduce the coercive field to one-fifth of that of the un-modified P(VDF-TrFE), which can help minimize the energy consumption and extend the lifespan of the device. The nanoimprint process leads to preferable orientation of polymer chains and delicately controlled distribution of the defects, and thus a bi-stable polarization that makes the memory nonvolatile, as revealed by the pulsed polarization experiment.Ferroelectric polymers are among the most promising materials for flexible electronic devices. Highly ordered arrays of the defect-modified ferroelectric polymer P(VDF-TrFE-CFE) (poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene)) are fabricated by nanoimprint lithography for nonvolatile memory application. The defective CFE units reduce the coercive field to one-fifth of that of the un-modified P(VDF-TrFE), which can help minimize the energy consumption and extend the lifespan of the device. The nanoimprint process leads to preferable orientation of polymer chains and delicately controlled distribution of the defects, and thus a bi-stable polarization that makes the memory nonvolatile, as revealed by the pulsed polarization experiment. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr03866e

  1. Shape-memory polymers as a technology platform for biomedical applications.

    PubMed

    Lendlein, Andreas; Behl, Marc; Hiebl, Bernhard; Wischke, Christian

    2010-05-01

    Polymeric materials are clinically required for medical devices, as well as controlled drug delivery systems. Depending on the application, the polymer has to provide suitable functionalities, for example, mechanical functions or the capability to actively move, so that an implant can be inserted in a compact shape through key-hole incisions and unfold to its functional shape in the body. Shape-memory polymers, as described herein regarding their general principle, compositions and architectures, have developed to a technology platform that allows the tailored design of such multifunctionality. In this way, defined movements of implants triggered either directly or indirectly, tailored mechanical properties, capability for sterilization, biodegradability, biocompatibility and controlled drug release can be realized. This comprehensive review of the scientific and patent literature illustrates that this technology enables the development of novel medical devices that will be clinically evaluated in the near future.

  2. New design of shape memory polymers based on natural rubber crosslinked via oxa-Michael reaction.

    PubMed

    Lin, Tengfei; Ma, Siwei; Lu, Yang; Guo, Baochun

    2014-04-23

    Shape memory polymers (SMPs) based on natural rubber were fabricated by crosslinking epoxidized natural rubber with zinc diacrylate (ZDA) using the oxa-Michael reaction. These SMPs possessed excellent shape fixity and recovery. The glass transition largely accounted for the fixing of the SMPs temporary shape. Increasing the ZDA content allowed the trigger temperature (20-46 °C) and recovery time (14-33 s) of the SMPs to be continuously tuned. Nanosized silica (nanosilica) was incorporated into the neat polymers to further increase the flexibility and tune the recovery stress. The nanosilica-SMPs exhibited exceptionally high strength in a rubbery state (>20 MPa). The nanosilica-SMPs exhibited high transparency, making them suitable in visible heat-shrinkable tubes.

  3. Swelling effect actuation of shape-memory polymer: mechanism and demonstration

    NASA Astrophysics Data System (ADS)

    Lu, Haibao; Leng, Jinsong; Liu, Yanju; Du, Shanyi

    2009-03-01

    Recently, there is increasing interest in triggering shape recovery of shape-memory polymers (SMPs) by novel inductive effect. In this paper, many hard works have been carried out to make SMP induced while along with swelling effect. Based on the Free-volume theory, Rubber Elasticity Theory and Mooney-Rivlin Equation, it is theoretically and experimentally demonstrated the feasibility of SMP activated by swelling effect. The mechanism behind it is solvent acting as plasticizer, to reduce the glass transition temperature (Tg) and melting temperature (Tm) of polymers, make them softer and more flexible, facilitating the diffusion of the molecules to polymer chains, and then separating them. In addition to this physical action, the intermolecular interactions among the chains are weakened, because interactions are hindered at the points where the plasticizer is located. Finally, the Dynamic mechanical analysis (DMA), FTIR study and glass transition temperature measurement tests were used to exemplify the feasibility of SMP driven by swelling effect. And it is qualitatively identified the role of swelling effect playing in influencing the transition temperature. Swelling effect occurs due to the interaction between macromolecules and solvent molecules, leading to free volume of polymeric chains increasing (namely the flexibility of polymer chains increasing), resulting in the Tg decreasing. All above mentioned investigation can be used to confirm that the shape recovery is induced by swelling effect. This actuation almost is applicable for all the SMP and SMP composite, as the swelling theory is almost applicable for all the polymeric materials.

  4. Coating of poly(p-xylylene) by PLA-PEO-PLA triblock copolymers with excellent polymer-polymer adhesion for stent applications.

    PubMed

    Hanefeld, Phillip; Westedt, Ullrich; Wombacher, Ralf; Kissel, Thomas; Schaper, Andreas; Wendorff, Joachim H; Greiner, Andreas

    2006-07-01

    Poly(p-xylylene) (PPX) was deposited by chemical vapor deposition (CVD) on stainless steel substrates. These PPX films were coated by solution casting of poly(lactide)-poly(ethylene oxide)-poly(lactide) triblock copolymers (PLA-PEO-PLA) loaded with 14C-labeled paclitaxel. Adhesion of PLA-PEO-PLA on PPX substrate coatings was measured using the blister test method. Excellent adhesion of the block copolymers on PPX substrates was found. Stress behavior and film integrity of PLA-PEO-PLA was compared to pure PLA on unexpanded and expanded stent bodies and was found to be superior for the block copolymers. The release of paclitaxel from the biodegradable coatings was studied under physiological conditions using the scintillation counter method. Burst release of paclitaxel was observed from PLA-PEO-PLA layers regardless of composition, but an increase in paclitaxel loading was observed with increasing content of PEO.

  5. Reticulation of low density shape memory polymer foam with an in vivo demonstration of vascular occlusion

    SciTech Connect

    Rodriguez, Jennifer N.; Miller, Matthew W.; Boyle, Anthony; Horn, John; Yang, Cheng-Kang; Wilson, Thomas S.; Ortega, Jason M.; Small, Ward; Nash, Landon; Skoog, Hunter; Maitland, Duncan J.

    2014-08-11

    Recently, predominantly closed-cell low density shape memory polymer (SMP) foam was reported to be an effective aneurysm filling device in a porcine model (Rodriguez et al., Journal of Biomedical Materials Research Part A 2013: (http://dx.doi.org/10.1002/jbm.a.34782)). Because healing involves blood clotting and cell migration throughout the foam volume, a more open-cell structure may further enhance the healing response. This research sought to develop a non-destructive reticulation process for this SMP foam to disrupt the membranes between pore cells. Non-destructive mechanical reticulation was achieved using a gravity-driven floating nitinol pin array coupled with vibratory agitation of the foam and supplemental chemical etching. Lastly, reticulation resulted in a reduced elastic modulus and increased permeability, but did not impede the shape memory behavior. Reticulated foams were capable of achieving rapid vascular occlusion in an in vivo porcine model.

  6. Reticulation of low density shape memory polymer foam with an in vivo demonstration of vascular occlusion

    DOE PAGES

    Rodriguez, Jennifer N.; Miller, Matthew W.; Boyle, Anthony; ...

    2014-08-11

    Recently, predominantly closed-cell low density shape memory polymer (SMP) foam was reported to be an effective aneurysm filling device in a porcine model (Rodriguez et al., Journal of Biomedical Materials Research Part A 2013: (http://dx.doi.org/10.1002/jbm.a.34782)). Because healing involves blood clotting and cell migration throughout the foam volume, a more open-cell structure may further enhance the healing response. This research sought to develop a non-destructive reticulation process for this SMP foam to disrupt the membranes between pore cells. Non-destructive mechanical reticulation was achieved using a gravity-driven floating nitinol pin array coupled with vibratory agitation of the foam and supplemental chemical etching.more » Lastly, reticulation resulted in a reduced elastic modulus and increased permeability, but did not impede the shape memory behavior. Reticulated foams were capable of achieving rapid vascular occlusion in an in vivo porcine model.« less

  7. Reticulation of low density shape memory polymer foam with an in vivo demonstration of vascular occlusion

    PubMed Central

    Rodriguez, Jennifer N.; Miller, Matthew W.; Boyle, Anthony; Horn, John; Yang, Cheng-Kang; Wilson, Thomas S.; Ortega, Jason M.; Small, Ward; Nash, Landon; Skoog, Hunter; Maitland, Duncan J.

    2014-01-01

    Predominantly closed-cell low density shape memory polymer (SMP) foam was recently reported to be an effective aneurysm filling device in a porcine model (Rodriguez et al., Journal of Biomedical Materials Research Part A 2013: (http://dx.doi.org/10.1002/jbm.a.34782)). Because healing involves blood clotting and cell migration throughout the foam volume, a more open-cell structure may further enhance the healing response. This research sought to develop a non-destructive reticulation process for this SMP foam to disrupt the membranes between pore cells. Non-destructive mechanical reticulation was achieved using a gravity-driven floating nitinol pin array coupled with vibratory agitation of the foam and supplemental chemical etching. Reticulation resulted in a reduced elastic modulus and increased permeability, but did not impede shape memory behavior. Reticulated foams were capable of achieving rapid vascular occlusion in an in vivo porcine model. PMID:25222869

  8. Reticulation of low density shape memory polymer foam with an in vivo demonstration of vascular occlusion.

    PubMed

    Rodriguez, Jennifer N; Miller, Matthew W; Boyle, Anthony; Horn, John; Yang, Cheng-Kang; Wilson, Thomas S; Ortega, Jason M; Small, Ward; Nash, Landon; Skoog, Hunter; Maitland, Duncan J

    2014-12-01

    Predominantly closed-cell low density shape memory polymer (SMP) foam was recently reported to be an effective aneurysm filling device in a porcine model (Rodriguez et al., Journal of Biomedical Materials Research Part A 2013: (http://dx.doi.org/10.1002/jbm.a.34782)). Because healing involves blood clotting and cell migration throughout the foam volume, a more open-cell structure may further enhance the healing response. This research sought to develop a non-destructive reticulation process for this SMP foam to disrupt the membranes between pore cells. Non-destructive mechanical reticulation was achieved using a gravity-driven floating nitinol pin array coupled with vibratory agitation of the foam and supplemental chemical etching. Reticulation resulted in a reduced elastic modulus and increased permeability, but did not impede the shape memory behavior. Reticulated foams were capable of achieving rapid vascular occlusion in an in vivo porcine model. Copyright © 2014 Elsevier Ltd. All rights reserved.

  9. Effects of interface treatment on the fatigue behaviour of shape memory alloy reinforced polymer composites

    NASA Astrophysics Data System (ADS)

    Hiremath, S. R.; Harish, K.; Vasireddi, Ramakrishna; Benal, M. M.; Mahapatra, D. R.

    2015-04-01

    Interfacial properties of Shape Memory Alloy (SMA) reinforced polymer matrix composites can be enhanced by improving the interfacial bonding. This paper focuses on studying the interfacial stresses developed in the SMAepoxy interface due to various laser shot penning conditions. Fiber-pull test-setup is designed to understand the role of mechanical bias stress cycling and thermal actuation cycling. Phase transformation is tracked over mechanical and thermal fatigue cycles. A micromechanics based model developed earlier based on shear lag in SMA and energy based consistent homogenization is extended here to incorporate the stress-temperature phase diagram parameters for modeling fatigue.

  10. Feasibility study of polyurethane shape-memory polymer actuators for pressure bandage application

    PubMed Central

    Ahmad, Manzoor; Luo, Jikui; Miraftab, Mohsen

    2012-01-01

    The feasibility of laboratory-synthesized polyurethane-based shape-memory polymer (SMPU) actuators has been investigated for possible application in medical pressure bandages where gradient pressure is required between the ankle and the knee for treatment of leg ulcers. In this study, using heat as the stimulant, SMPU strip actuators have been subjected to gradual and cyclic stresses; their recovery force, reproducibility and reusability have been monitored with respect to changes in temperature and circumference of a model leg, and the stress relaxation at various temperatures has been investigated. The findings suggest that SMPU actuators can be used for the development of the next generation of pressure bandages. PMID:27877473

  11. Feasibility study of polyurethane shape-memory polymer actuators for pressure bandage application.

    PubMed

    Ahmad, Manzoor; Luo, Jikui; Miraftab, Mohsen

    2012-02-01

    The feasibility of laboratory-synthesized polyurethane-based shape-memory polymer (SMPU) actuators has been investigated for possible application in medical pressure bandages where gradient pressure is required between the ankle and the knee for treatment of leg ulcers. In this study, using heat as the stimulant, SMPU strip actuators have been subjected to gradual and cyclic stresses; their recovery force, reproducibility and reusability have been monitored with respect to changes in temperature and circumference of a model leg, and the stress relaxation at various temperatures has been investigated. The findings suggest that SMPU actuators can be used for the development of the next generation of pressure bandages.

  12. Three-Dimensional Flexible Electronics Enabled by Shape Memory Polymer Substrates for Responsive Neural Interfaces.

    PubMed

    Ware, Taylor; Simon, Dustin; Hearon, Keith; Liu, Clive; Shah, Sagar; Reeder, Jonathan; Khodaparast, Navid; Kilgard, Michael P; Maitland, Duncan J; Rennaker, Robert L; Voit, Walter E

    2012-12-01

    Planar electronics processing methods have enabled neural interfaces to become more precise and deliver more information. However, this processing paradigm is inherently 2D and rigid. The resulting mechanical and geometrical mismatch at the biotic-abiotic interface can elicit an immune response that prevents effective stimulation. In this work, a thiol-ene/acrylate shape memory polymer is utilized to create 3D softening substrates for stimulation electrodes. This substrate system is shown to soften in vivo from more than 600 to 6 MPa. A nerve cuff electrode that coils around the vagus nerve in a rat and that drives neural activity is demonstrated.

  13. Feasibility study of polyurethane shape-memory polymer actuators for pressure bandage application

    NASA Astrophysics Data System (ADS)

    Ahmad, Manzoor; Luo, Jikui; Miraftab, Mohsen

    2012-02-01

    The feasibility of laboratory-synthesized polyurethane-based shape-memory polymer (SMPU) actuators has been investigated for possible application in medical pressure bandages where gradient pressure is required between the ankle and the knee for treatment of leg ulcers. In this study, using heat as the stimulant, SMPU strip actuators have been subjected to gradual and cyclic stresses; their recovery force, reproducibility and reusability have been monitored with respect to changes in temperature and circumference of a model leg, and the stress relaxation at various temperatures has been investigated. The findings suggest that SMPU actuators can be used for the development of the next generation of pressure bandages.

  14. Three-Dimensional Flexible Electronics Enabled by Shape Memory Polymer Substrates for Responsive Neural Interfaces

    PubMed Central

    Ware, Taylor; Simon, Dustin; Hearon, Keith; Liu, Clive; Shah, Sagar; Reeder, Jonathan; Khodaparast, Navid; Kilgard, Michael P.; Maitland, Duncan J.; Rennaker, Robert L.; Voit, Walter E.

    2014-01-01

    Planar electronics processing methods have enabled neural interfaces to become more precise and deliver more information. However, this processing paradigm is inherently 2D and rigid. The resulting mechanical and geometrical mismatch at the biotic–abiotic interface can elicit an immune response that prevents effective stimulation. In this work, a thiol–ene/acrylate shape memory polymer is utilized to create 3D softening substrates for stimulation electrodes. This substrate system is shown to soften in vivo from more than 600 to 6 MPa. A nerve cuff electrode that coils around the vagus nerve in a rat and that drives neural activity is demonstrated. PMID:25530708

  15. Femtosecond-laser direct writing in polymers and potential applications in microfluidics and memory devices

    NASA Astrophysics Data System (ADS)

    Kallepalli, Lakshmi Narayana Deepak; Soma, Venugopal Rao; Desai, Narayana Rao

    2012-07-01

    We have investigated femtosecond-laser-induced microstructures (on the surface and within the bulk), gratings, and craters in four different polymers: polymethyl methacrylate, polydimethylsiloxane, polystyrene, and polyvinyl alcohol. The structures were achieved using a Ti:sapphire laser delivering 100-fs pulses at 800 nm with a repetition rate of 1 kHz and a maximum pulse energy of 1 mJ. Local chemical modifications leading to the formation of optical centers and peroxide radicals were studied using ultraviolet-visible absorption and emission, confocal micro-Raman and electron spin resonance spectroscopic techniques. Potential applications of these structures in microfluidics, waveguides, and memory-based devices are demonstrated.

  16. Isothermal recovery response and constitutive model of thermoset shape memory polymers

    NASA Astrophysics Data System (ADS)

    Tan, Huifeng; Zhou, Tao; Liu, Yuyan; Lan, Lan

    2012-04-01

    Deformation recovery capability is one of the important indexes to examination shape memory effect of the shape memory polymers (SMPs). And the shape memory characteristic of SMPs is closely related to different phase states and mechanical properties above and below the glass transition temperature (Tg). In this paper, we investigated the strain recovery response of a thermoset shape memory epoxy resin modified by polyurethane (PU) through uniaxial compression experiments under various isothermal conditions and strain rates and developed a "three-phase" constitutive model based on phase transition concept, which including stationary phase, active phase and frozen phase. This model established the mutual transformation relationships between frozen phase and active phase of SMPs by introducing temperature switch function, which presents the stain storage and release process of SMPs under loading and changing temperature environment. Besides, the proposed model represents the SMPs deformation process of viscous hysteresis response by employing the rheological elements description of the three phases. The numerical results agree very well with experiment results of stress-strain response curve of isothermal compression/unloading test, which validated this model can predict the finite deformation behavior of SMPs.

  17. Theoretical and experimental investigation of the shape memory properties of an ionic polymer-metal composite

    NASA Astrophysics Data System (ADS)

    Shen, Qi; Palmre, Viljar; Kim, Kwang J.; Oh, Il-Kwon

    2017-04-01

    An ionic polymer-metal composite (IPMC) is typically based on a Nafion membrane with electrode plating on both sides and has a promising potential for biomimetic robotics, biomedical devices and human affinity applications. In this paper, the shape memory properties of IPMC were theoretically and experimentally studied. We presented the multiple shape memory properties of a Nafion cylinder. A physics based model of the IPMC was proposed. The free energy density theory was utilized to analyze the shape properties of the IPMC. To verify the model, IPMC samples with Nafion as the base membrane were prepared and experiments were conducted. A simulation of the model was performed and the results were compared with the experimental data. It was successfully demonstrated that the theoretical model can well explain the shape memory properties of the IPMC. The results showed that the reheat glass transition temperature of the IPMC is lower than the programming temperature. It was also found that the back-relaxation of the IPMC decreases as the programming temperature increases. The current study may be useful in order to better understand the shape memory effect of IPMC.

  18. Isothermal recovery response and constitutive model of thermoset shape memory polymers

    NASA Astrophysics Data System (ADS)

    Tan, Huifeng; Zhou, Tao; Liu, Yuyan; Lan, Lan

    2011-11-01

    Deformation recovery capability is one of the important indexes to examination shape memory effect of the shape memory polymers (SMPs). And the shape memory characteristic of SMPs is closely related to different phase states and mechanical properties above and below the glass transition temperature (Tg). In this paper, we investigated the strain recovery response of a thermoset shape memory epoxy resin modified by polyurethane (PU) through uniaxial compression experiments under various isothermal conditions and strain rates and developed a "three-phase" constitutive model based on phase transition concept, which including stationary phase, active phase and frozen phase. This model established the mutual transformation relationships between frozen phase and active phase of SMPs by introducing temperature switch function, which presents the stain storage and release process of SMPs under loading and changing temperature environment. Besides, the proposed model represents the SMPs deformation process of viscous hysteresis response by employing the rheological elements description of the three phases. The numerical results agree very well with experiment results of stress-strain response curve of isothermal compression/unloading test, which validated this model can predict the finite deformation behavior of SMPs.

  19. Reconfigurable Photonic Crystals Enabled by Multistimuli-Responsive Shape Memory Polymers Possessing Room Temperature Shape Processability.

    PubMed

    Fang, Yin; Leo, Sin-Yen; Ni, Yongliang; Wang, Junyu; Wang, Bingchen; Yu, Long; Dong, Zhe; Dai, Yuqiong; Basile, Vito; Taylor, Curtis; Jiang, Peng

    2017-02-15

    Traditional shape memory polymers (SMPs) are mostly thermoresponsive, and their applications in nano-optics are hindered by heat-demanding programming and recovery processes. By integrating a polyurethane-based shape memory copolymer with templating nanofabrication, reconfigurable/rewritable macroporous photonic crystals have been demonstrated. This SMP coupled with the unique macroporous structure enables unusual all-room-temperature shape memory cycles. "Cold" programming involving microscopic order-disorder transitions of the templated macropores is achieved by mechanically deforming the macroporous SMP membranes. The rapid recovery of the permanent, highly ordered photonic crystal structure from the temporary, disordered configuration can be triggered by multiple stimuli including a large variety of vapors and solvents, heat, and microwave radiation. Importantly, the striking chromogenic effects associated with these athermal and thermal processes render a sensitive and noninvasive optical methodology for quantitatively characterizing the intriguing nanoscopic shape memory effects. Some critical parameters/mechanisms that could significantly affect the final performance of SMP-based reconfigurable photonic crystals including strain recovery ratio, dynamics and reversibility of shape recovery, as well as capillary condensation of vapors in macropores, which play a crucial role in vapor-triggered recovery, can be evaluated using this new optical technology.

  20. Post-sialendoscopy ductoplasty by salivary duct stent placements.

    PubMed

    Su, Chin-Hui; Lee, Kuo-Sheng; Tseng, Te-Ming; Hung, Shih-Han

    2016-01-01

    With damage to a duct or papilla after sialendoscopy, a stent may be necessary to prevent re-stenosis and for maintaining the salivary duct open after complete sialendoscopy. However factors affecting outcomes and complications after stent placement remain unclear. This study aimed to report preliminary experiences in salivary duct stent placement after sialendoscopy. Data from 35 procedures in 33 patients who received sialendoscopy with salivary duct stent placements at Mackay Memorial Hospital between October 2013 and June 2014 were recorded and compared for clinical data, as well as procedural techniques, findings, and outcomes. In the 35 stent placement procedures, the hypospadias silastic stent tubes were used in 27 and the Fr. 5 pediatric feeding tubes were used in the remaining eight. When the hypospadias silastic stent tubes were used for stenting, the stent obstruction and irritation rates were higher compared to those who used the Fr. 5 pediatric feeding tube (100 vs. 0 % and 67 vs. 33 %, respectively). None of the stents secured by a 5-0 nylon suture were complicated by dislocation but when the stents were secured by 6-0 nylon sutures, the dislocation rate went as high as 47.4 %. The duration needed for salivary duct stent placement might be potentially shortened to only 2 weeks. If a salivary duct stent is intended to be placed for a certain period before its scheduled removal, a suture strength equivalent or stronger than the 5-0 nylon suture should be considered for stent fixation.

  1. On the Takayanagi principle for the shape memory effect and thermomechanical behaviors in polymers with multi-phases

    NASA Astrophysics Data System (ADS)

    Lu, Haibao; Yu, Kai; Huang, Wei Min; Leng, Jinsong

    2016-12-01

    We present an explicit model to study the mechanics and physics of the shape memory effect (SME) in polymers based on the Takayanagi principle. The molecular structural characteristics and elastic behavior of shape memory polymers (SMPs) with multi-phases are investigated in terms of the thermomechanical properties of the individual components, of which the contributions are combined by using Takayanagi’s series-parallel model and parallel-series model, respectively. After that, Boltzmann superposition principle is employed to couple the multi-SME, elastic modulus parameter (E) and temperature parameter (T) in SMPs. Furthermore, the extended Takayanagi model is proposed to separate the plasticizing effect and physical swelling effect on the thermo-/chemo-responsive SME in polymers and then compared with the available experimental data reported in the literature. This study is expected to provide a powerful simulation tool for modeling and experimental substantiation of the mechanics and working mechanism of SME in polymers.

  2. Efficacy and safety of a biodegradable polymer Cobalt-Chromium sirolimus-eluting stent (EXCEL2) in treating de novo coronary artery disease: A pooled analysis of the CREDIT II and CREDIT III trials.

    PubMed

    Wang, Geng; Wang, Heyang; Xu, Bo; Yang, Yuejin; Yang, Zhiming; Li, Hui; Zhang, Zheng; Wang, Haichang; Yang, Lixia; Han, Yaling

    2017-03-01

    The safety and efficacy of the second-generation biodegradable polymer Cobalt-Chromium sirolimus-eluting stent (EXCEL2) in daily clinical practice remains unknown. Additionally, to meet the China Food and Drug Administration requirements, we conducted an objective performance criterion study from the CREDIT II and CREDIT III trials. CREDIT II was a randomized trial comparing the EXCEL2 versus EXCEL stent in patients with up to 2 de novo coronary lesions. CREDIT III was a prospective, single-arm study evaluating the efficacy and safety of EXCEL2 in broad types of de novo coronary artery lesions. This pooled analysis included patients in the CREDIT III and EXCEL2 arm of the CREDIT II trial. The primary outcome was 12-month target lesion failure (TLF), a composite of cardiac death, target vessel myocardial infarction (TV-MI), and clinical indicated target lesion revascularization (CI-TLR). The patient-oriented composite endpoint (PoCE) of all-cause death, all MI, or any revascularization was also analyzed. A total of 833 patients were included, consisting of 625 in the CREDIT III trial and 208 in the EXCEL2 arm of the CREDIT II trial. Twelve-month TLF occurred in 6.1% patients, cardiac death in 0.4%, TV-MI in 5%, and CI-TLR in 1.1%. Additionally, 64 (7.7%) PoCE and 3 probable late stent thromboses (0.4%) were recorded. EXCEL2 stent met the objective performance criterion on efficacy and safety with a low level of 12-month TLF as well as stent thrombosis when treating patients with de novo coronary lesions. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  3. Coating bioabsorption and chronic bare metal scaffolding versus fully bioabsorbable stent.

    PubMed

    Waksman, Ron; Pakala, Rajbabu

    2009-12-15

    Advances in coronary stent technology, including refinement of the stent alloy, strut thickness, stent geometry, passive coating, and drug elution, have dramatically enhanced the safety and efficacy of percutaneous coronary intervention (PCI) with stenting. Stents are currently used in over 90% of coronary interventions and the use of drug-eluting stents (DES) has been disseminated to more complex lesion subsets such as total occlusions, long lesions, bifurcation lesions, and for patients with acute myocardial infarction. DES continue to demonstrate reduction in restenosis and the need for repeat revascularisation but are associated with delayed healing and re-endothelialisation, which have led to an increased rates of late stent thrombosis, dependency on prolonged dual antiplatelet therapy, impaired in-vessel reactivity, and chronic inflammation. As scientists and clinicians better understand the mechanism for late restenosis and stent thrombosis, a variety of solutions in regard to stent technology have been proposed, including stent coating, polymer bioabsorption, and fully biodegradable stents. Bare metal stents were improved by the reduction of strut thickness, changes in stent geometry, and the addition of passive coating, which lead to improvements in efficacy and reduction of restenosis. In addition, there is continued improvement in the polymer technology for DES, including new biocompatible, thinner durable polymers, and bioabsorbable polymers that completely bioabsorb within 3-12 months after stent implantation. These features potentially minimise the chronic inflammatory response and late stent thrombosis. Finally, fully bioabsorbable stents, both polymeric and metallic, continue to be developed in order to eliminate any late stenting effects and potentially may enable complete vessel restoration. This manuscript will discuss the wide variety of new stent technologies and compare and contrast durable metallic and polymeric stents to current

  4. Clinical Events and Patient-Reported Chest Pain in All-Comers Treated With Resolute Integrity and Promus Element Stents: 2-Year Follow-Up of the DUTCH PEERS (DUrable Polymer-Based STent CHallenge of Promus ElemEnt Versus ReSolute Integrity) Randomized Trial (TWENTE II).

    PubMed

    Sen, Hanim; Lam, Ming Kai; Löwik, Marije M; Danse, Peter W; Jessurun, Gillian A J; van Houwelingen, K Gert; Anthonio, Rutger L; Tjon Joe Gin, R Melvyn; Hautvast, Raymond W M; Louwerenburg, J Hans W; de Man, Frits H A F; Stoel, Martin G; van der Heijden, Liefke C; Linssen, Gerard C M; IJzerman, Maarten J; Tandjung, Kenneth; Doggen, Carine J M; von Birgelen, Clemens

    2015-06-01

    This study assessed clinical events and patient-reported chest pain 2 years after treatment of all-comers with Resolute Integrity zotarolimus-eluting stents (Medtronic Vascular, Santa Rosa, California) and Promus Element everolimus-eluting stents (Boston Scientific, Natick, Massachusetts). For both drug-eluting stents (DES), no all-comer outcome data from >12 months of follow-up have been published. Although there is increasing interest in patient-reported chest pain following stenting, data with novel DES are scarce. The DUTCH PEERS multicenter trial (TWENTE II) (DUrable Polymer-Based STent CHallenge of Promus ElemEnt Versus ReSolute Integrity) Randomized Trial [TWENTE II]) randomized 1,811 all-comer patients to treatment with 1 type of DES. Monitoring and event adjudication were performed by independent contract research organizations. The 2-year follow-up of 1,810 patients (99.9%) was available. The primary composite endpoint target vessel failure occurred in 8.6% and 7.8% of patients treated with zotarolimus- and everolimus-eluting stents, respectively (p = 0.55). Rates of components of target vessel failure were: cardiac death (2.4% vs. 1.9%, p = 0.42); target vessel-related myocardial infarction (2.4% vs. 1.8%, p = 0.33); clinically-indicated target vessel revascularization (4.6% vs. 4.9%, p = 0.83). At 1- and 2-year follow-up, >80% of patients were free from chest pain (no between-stent difference). In addition, >87% of patients were either free from chest pain or experienced pain only at maximal physical exertion, but not during normal daily activities. Patients with chest pain after 12 months at no more than moderate physical effort had a higher risk of target vessel revascularization during the following year (hazard ratio: 1.89 [95% confidence interval: 1.05 to 3.39], p = 0.03). During the second year of follow-up, the incidence of adverse clinical endpoints remained similar and low for both DES. The vast majority of patients were free from chest pain

  5. Early Clinical Experience with a Polymer-Free Biolimus A9 Drug-Coated Stent in DES-Type Patients Who Are Poor Candidates for Prolonged Dual Anti-Platelet Therapy

    PubMed Central

    Kinnaird, Tim; Butt, Mehmood; Abdul, Fairoz; Yazji, Khaled; Hailan, Ahmed; Gallagher, Sean; Ossei-Gerning, Nicholas; Chase, Alexander; Choudhury, Anirban; Smith, David; Anderson, Richard

    2016-01-01

    Introduction Prolonged dual anti-platelet therapy (DAPT) may cause excess bleeding in certain patients. The biolimus-A9 drug-coated stent (BA9-DCS) has a rapid drug-elution profile allowing shortened DAPT. Data were gathered on the early experience implanting this stent in drug-eluting stent eligible patients deemed to be at high risk of bleeding. Background and Methods The demographics, procedural data and clinical outcomes were gathered prospectively for 249 patients treated with a BA9-DCS stent at 2 UK centres, and compared to a cohort of patients treated in the same period with drug-eluting stents (PCI-DES). Results Operator-defined BA9-DCS indications included warfarin therapy, age, and anaemia. Patients receiving a BA9-DCS were older (71.6±11.8 vs. 64.8±11.6yrs, p<0.001), more often female (38.2 vs. 26.8%, P<0.001), and more likely to have comorbidity including chronic kidney disease or poor LV function than PCI-DES patients. The baseline Mehran bleed risk score was also significantly higher in the BA9-DCS group (19.4±8.7 vs. 13.1±5.8, p<0.001). Of the BA9-DCS cohort, 95.5% of patients demonstrated disease fitting NICE criteria for DES placement. The number of lesions treated (1.81±1.1 vs. 1.58±0.92, p = 0.003), total lesion length (32.1±21.7 vs. 26.1±17.6mm, p<0.001), number of stents used (1.93±1.11 vs. 1.65±1.4, p = 0.007) and total stent length (37.5±20.8 vs. 32.4±20.3, p<0.01) were greater for BA9-DCS patients. DAPT was prescribed for 3.3±3.9 months for BA9-DCS patients and 11.3±2.4 months for PCI-DES patients (p<0.001). At follow up of 392±124 days despite the abbreviated DAPT course stent related event were infrequent with ischemia-driven restenosis PCI (2.8 vs. 3.4%, p = 0.838), and stent thrombosis (1.6 vs. 2.1%, p = 0.265) rates similar between the BA9-DCS ad PCI-DES groups. After propensity scoring all clinical end-points were similar between both cohorts. Conclusions This early experience using polymer-free BA9 drug-coated stents in

  6. New Scalable Approach toward Shape Memory Polymer Composites via "Spring-Buckle" Microstructure Design.

    PubMed

    Wu, Xiaodong; Han, Yangyang; Zhou, Zehang; Zhang, Xinxing; Lu, Canhui

    2017-04-19

    Shape memory polymers (SMPs) have attracted tremendous research interest since their discovery. However, most advances in research of SMPs are based on molecular designs, i.e., "bottom-up" strategies. Due to the viscoelasticity of polymers, slow and incomplete shape variations are inevitable for most existing SMPs. Here, we propose a simple and scalable approach to design and fabricate SMP composites (SMPCs) based on a "spring-buckle" microstructure design. Specifically, a highly elastic "spring" is employed as a basic skeleton for the SMPCs, onto which self-adhesive and stimuli-responsive "buckles" are installed as reversible switch units. The resultant SMPCs with such "spring-buckle" microstructure enable quick programming at ambient temperature and ultrafast (2-3 s) and nearly complete (∼100%) shape recovery triggered by organic solvents, benefiting from a unique capillary effect. This structural approach provides a novel design philosophy for shape memory materials and opens up new opportunities for their applications in sensor, actuator, aerospace, and other applications.

  7. Vascular dynamics of a shape memory polymer foam aneurysm treatment technique.

    PubMed

    Ortega, Jason; Maitland, Duncan; Wilson, Tom; Tsai, William; Savaş, Omer; Saloner, David

    2007-11-01

    The vascular dynamics of a shape memory polymer foam aneurysm treatment technique are assessed through the simulated treatment of a generic basilar aneurysm using coupled fluid dynamics and heat transfer calculations. The shape memory polymer foam, which expands to fill the aneurysm when heated, is modeled at three discrete stages of the treatment procedure. To estimate an upper bound for the maximum amount of thermal damage due to foam heating, a steady velocity is specified through the basilar artery, corresponding to a minimum physiological flow velocity over a cardiac cycle. During expansion, the foam alters the flow patterns within the aneurysm by shielding the aneurysm dome from a confined jet that issues from the basilar artery. The time scales for thermal damage to the artery walls and surrounding blood flow are computed from the temperature field. The flow through the post-treatment bifurcation is comprised of two counter-rotating vortex tubes that are located beneath the aneurysm neck and extend downstream into the outlet arteries. Beneath the aneurysm neck, a marked increase in the wall shear stress is observed due to the close proximity of the counter-rotating vortex tubes to the artery wall.

  8. Preparation and characterization of shape memory polymer scaffolds via solvent casting/particulate leaching.

    PubMed

    De Nardo, Luigi; Bertoldi, Serena; Cigada, Alberto; Tanzi, Maria Cristina; Haugen, Håvard Jostein; Farè, Silvia

    2012-09-27

    Porous Shape Memory Polymers (SMPs) are ideal candidates for the fabrication of defect fillers, able to support tissue regeneration via minimally invasive approaches. In this regard, control of pore size, shape and interconnection is required to achieve adequate nutrient transport and cell ingrowth. Here, we assessed the feasibility of the preparation of SMP porous structures and characterized their chemico-physical properties and in vitro cell response. SMP scaffolds were obtained via solvent casting/particulate leaching of gelatin microspheres, prepared via oil/water emulsion. A solution of commercial polyether-urethane (MM-4520, Mitsubishi Heavy Industries) was cast on compacted microspheres and leached-off after polymer solvent evaporation. The obtained structures were characterized in terms of morphology (SEM and micro-CT), thermo-mechanical properties (DMTA), shape recovery behavior in compression mode, and in vitro cytocompatibility (MG63 Osteoblast-like cell line). The fabrication process enabled easy control of scaffold morphology, pore size, and pore shape by varying the gelatin microsphere morphology. Homogeneous spherical and interconnected pores have been achieved together with the preservation of shape memory ability, with recovery rate up to 90%. Regardless of pore dimensions, MG63 cells were observed adhering and spreading onto the inner surface of the scaffolds obtained for up to seven days of static in vitro tests. A new class of SMP porous structures has been obtained and tested in vitro: according to these preliminary results reported, SMP scaffolds can be further exploited in the design of a new class of implantable devices.

  9. Analysis of the finite deformation response of shape memory polymers: I. Thermomechanical characterization

    NASA Astrophysics Data System (ADS)

    Volk, Brent L.; Lagoudas, Dimitris C.; Chen, Yi-Chao; Whitley, Karen S.

    2010-07-01

    This study presents the analysis of the finite deformation response of a shape memory polymer (SMP). This two-part paper addresses the thermomechanical characterization of SMPs, the derivation of material parameters for a finite deformation phenomenological model, the numerical implementation of such a model, and the predictions from the model with comparisons to experimental data. Part I of this work presents the thermomechanical characterization of the material behavior of a shape memory polymer. In this experimental investigation, the vision image correlation system, a visual-photographic apparatus, was used to measure displacements in the gauge area. A series of tensile tests, which included nominal values of the extension of 10%, 25%, 50%, and 100%, were performed on SMP specimens. The effects on the free recovery behavior of increasing the value of the applied deformation and temperature rate were considered. The stress-extension relationship was observed to be nonlinear for increasing values of the extension, and the shape recovery was observed to occur at higher temperatures upon increasing the temperature rate. The experimental results, aided by the advanced experimental apparatus, present components of the material behavior which are critical for the development and calibration of models to describe the response of SMPs.

  10. Sequential Self-Folding Structures by 3D Printed Digital Shape Memory Polymers

    NASA Astrophysics Data System (ADS)

    Mao, Yiqi; Yu, Kai; Isakov, Michael S.; Wu, Jiangtao; Dunn, Martin L.; Jerry Qi, H.

    2015-09-01

    Folding is ubiquitous in nature with examples ranging from the formation of cellular components to winged insects. It finds technological applications including packaging of solar cells and space structures, deployable biomedical devices, and self-assembling robots and airbags. Here we demonstrate sequential self-folding structures realized by thermal activation of spatially-variable patterns that are 3D printed with digital shape memory polymers, which are digital materials with different shape memory behaviors. The time-dependent behavior of each polymer allows the temporal sequencing of activation when the structure is subjected to a uniform temperature. This is demonstrated via a series of 3D printed structures that respond rapidly to a thermal stimulus, and self-fold to specified shapes in controlled shape changing sequences. Measurements of the spatial and temporal nature of self-folding structures are in good agreement with the companion finite element simulations. A simplified reduced-order model is also developed to rapidly and accurately describe the self-folding physics. An important aspect of self-folding is the management of self-collisions, where different portions of the folding structure contact and then block further folding. A metric is developed to predict collisions and is used together with the reduced-order model to design self-folding structures that lock themselves into stable desired configurations.

  11. A Thrombus Generation Model Applied to Aneurysms Treated with Shape Memory Polymer Foam and Metal Coils

    NASA Astrophysics Data System (ADS)

    Horn, John; Ortega, Jason; Hartman, Jonathan; Maitland, Duncan

    2015-11-01

    To prevent their rupture, intracranial aneurysms are often treated with endovascular metal coils which fill the aneurysm sac and isolate it from the arterial flow. Despite its widespread use, this method can result in suboptimal outcomes leading to aneurysm recurrence. Recently, shape memory polymer foam has been proposed as an alternative aneurysm filler. In this work, a computational model has been developed to predict thrombus formation in blood in response to such cardiovascular implantable devices. The model couples biofluid and biochemical phenomena present as the blood interacts with a device and stimulates thrombus formation. This model is applied to simulations of both metal coil and shape memory polymer foam treatments within an idealized 2D aneurysm geometry. Using the predicted thrombus responses, the performance of these treatments is evaluated and compared. The results suggest that foam-treated aneurysms may fill more quickly and more completely with thrombus than coil-filled aneurysms, potentially leading to improved long-term aneurysm healing. This work was performed in part under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  12. Fiber reinforced shape-memory polymer composite and its application in a deployable hinge

    NASA Astrophysics Data System (ADS)

    Lan, Xin; Liu, Yanju; Lv, Haibao; Wang, Xiaohua; Leng, Jinsong; Du, Shanyi

    2009-02-01

    This paper investigates the shape recovery behavior of thermoset styrene-based shape-memory polymer composite (SMPC) reinforced by carbon fiber fabrics, and demonstrates the feasibility of using an SMPC hinge as a deployable structure. The major advantages of shape-memory polymers (SMPs) are their extremely high recovery strain, low density and low cost. However, relatively low modulus and low strength are their intrinsic drawbacks. A fiber reinforced SMPC which may overcome the above-mentioned disadvantages is studied here. The investigation was conducted by three types of test, namely dynamic mechanical analysis (DMA), a shape recovery test, and optical microscopic observations of the deformation mechanism for an SMPC specimen. Results reveal that the SMPC exhibits a higher storage modulus than that of a pure SMP. At/above Tg, the shape recovery ratio of the SMPC upon bending is above 90%. The shape recovery properties of the SMPC become relatively stable after some packaging/deployment cycles. Additionally, fiber microbuckling is the primary mechanism for obtaining a large strain in the bending of the SMPC. Moreover, an SMPC hinge has been fabricated, and a prototype of a solar array actuated by the SMPC hinge has been successfully deployed.

  13. Sequential Self-Folding Structures by 3D Printed Digital Shape Memory Polymers

    PubMed Central

    Mao, Yiqi; Yu, Kai; Isakov, Michael S.; Wu, Jiangtao; Dunn, Martin L.; Jerry Qi, H.

    2015-01-01

    Folding is ubiquitous in nature with examples ranging from the formation of cellular components to winged insects. It finds technological applications including packaging of solar cells and space structures, deployable biomedical devices, and self-assembling robots and airbags. Here we demonstrate sequential self-folding structures realized by thermal activation of spatially-variable patterns that are 3D printed with digital shape memory polymers, which are digital materials with different shape memory behaviors. The time-dependent behavior of each polymer allows the temporal sequencing of activation when the structure is subjected to a uniform temperature. This is demonstrated via a series of 3D printed structures that respond rapidly to a thermal stimulus, and self-fold to specified shapes in controlled shape changing sequences. Measurements of the spatial and temporal nature of self-folding structures are in good agreement with the companion finite element simulations. A simplified reduced-order model is also developed to rapidly and accurately describe the self-folding physics. An important aspect of self-folding is the management of self-collisions, where different portions of the folding structure contact and then block further folding. A metric is developed to predict collisions and is used together with the reduced-order model to design self-folding structures that lock themselves into stable desired configurations. PMID:26346202

  14. Sequential Self-Folding Structures by 3D Printed Digital Shape Memory Polymers.

    PubMed

    Mao, Yiqi; Yu, Kai; Isakov, Michael S; Wu, Jiangtao; Dunn, Martin L; Jerry Qi, H

    2015-09-08

    Folding is ubiquitous in nature with examples ranging from the formation of cellular components to winged insects. It finds technological applications including packaging of solar cells and space structures, deployable biomedical devices, and self-assembling robots and airbags. Here we demonstrate sequential self-folding structures realized by thermal activation of spatially-variable patterns that are 3D printed with digital shape memory polymers, which are digital materials with different shape memory behaviors. The time-dependent behavior of each polymer allows the temporal sequencing of activation when the structure is subjected to a uniform temperature. This is demonstrated via a series of 3D printed structures that respond rapidly to a thermal stimulus, and self-fold to specified shapes in controlled shape changing sequences. Measurements of the spatial and temporal nature of self-folding structures are in good agreement with the companion finite element simulations. A simplified reduced-order model is also developed to rapidly and accurately describe the self-folding physics. An important aspect of self-folding is the management of self-collisions, where different portions of the folding structure contact and then block further folding. A metric is developed to predict collisions and is used together with the reduced-order model to design self-folding structures that lock themselves into stable desired configurations.

  15. Self-healing nanocomposite using shape memory polymer and carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Liu, Yingtao; Rajadas, Abhishek; Chattopadhyay, Aditi

    2013-04-01

    Carbon fiber reinforced composites are used in a wide range of applications in aerospace, mechanical, and civil structures. Due to the nature of material, most damage in composites, such as delaminations, are always barely visible to the naked eye, which makes it difficult to detect and repair. The investigation of biological systems has inspired the development and characterization of self-healing composites. This paper presents the development of a new type of self-healing material in order to impede damage progression and conduct in-situ damage repair in composite structures. Carbon nanotubes, which are highly conductive materials, are mixed with shape memory polymer to develop self-healing capability. The developed polymeric material is applied to carbon fiber reinforced composites to automatically heal the delamination between different layers. The carbon fiber reinforced composite laminates are manufactured using high pressure molding techniques. Tensile loading is applied to double cantilever beam specimens using an MTS hydraulic test frame. A direct current power source is used to generate heat within the damaged area. The application of thermal energy leads to re-crosslinking in shape memory polymers. Experimental results showed that the developed composite materials are capable of healing the matrix cracks and delaminations in the bonded areas of the test specimens. The developed self-healing material has the potential to be used as a novel structural material in mechanical, civil, aerospace applications.

  16. Highly compliant shape memory polymer gels for tunable damping and reversible adhesion

    NASA Astrophysics Data System (ADS)

    Mrozek, Randy A.; Berg, Michael C.; Gold, Christopher S.; Leighliter, Brad; Morton, Jeffrey T.; Lenhart, Joseph L.

    2016-02-01

    Materials that can dynamically change their properties to better adapt to the local environment have potential utility in robotics, aerospace, and coatings. For some of these applications, most notably robotics, it is advantageous for these responsive materials to be highly compliant in an effort to provide dynamic changes in adhesion and mechanical damping within a broad temperature operational environment. In this report, non-aqueous, highly compliant shape-memory polymer gels are developed by incorporating a low density of chemical cross-links into a physically cross-linked thermoplastic elastomer gel. Chemical cross-linkers were evaluated by varying there size and degree of functionality to determine the impact on the mechanical and adhesive properties. As a result of the chemical cross-linking, the gels exhibit modulus plateaus around room temperature and at elevated temperatures above 100 °C, where the thermoplastic elastomer gel typically melts. The materials were designed so that moduli in the plateaued regions were above and below the Dahlquist criteria of 4 × 104 Pa, respectively, where materials with a modulus below this value typically exhibit an increase in adhesion. The shape memory polymer gels were also integrated into fiber-reinforced composites to determine the temperature-dependent changes in mechanical damping. It is anticipated that this work will provide insight into materials design to provide dynamic changes in adhesion and damping to improve robotic appendage manipulation and platform mobility.

  17. Frequency-controlled wireless shape memory polymer microactuator for drug delivery application.

    PubMed

    Zainal, M A; Ahmad, A; Mohamed Ali, M S

    2017-03-01

    This paper reports the wireless Shape-Memory-Polymer actuator operated by external radio frequency magnetic fields and its application in a drug delivery device. The actuator is driven by a frequency-sensitive wireless resonant heater which is bonded directly to the Shape-Memory-Polymer and is activated only when the field frequency is tuned to the resonant frequency of heater. The heater is fabricated using a double-sided Cu-clad Polyimide with much simpler fabrication steps compared to previously reported methods. The actuation range of 140 μm as the tip opening distance is achieved at device temperature 44 °C in 30 s using 0.05 W RF power. A repeatability test shows that the actuator's average maximum displacement is 110 μm and standard deviation of 12 μm. An experiment is conducted to demonstrate drug release with 5 μL of an acidic solution loaded in the reservoir and the device is immersed in DI water. The actuator is successfully operated in water through wireless activation. The acidic solution is released and diffused in water with an average release rate of 0.172 μL/min.

  18. Electroactive polymer and shape memory alloy actuators in biomimetics and humanoids

    NASA Astrophysics Data System (ADS)

    Tadesse, Yonas

    2013-04-01

    There is a strong need to replicate natural muscles with artificial materials as the structure and function of natural muscle is optimum for articulation. Particularly, the cylindrical shape of natural muscle fiber and its interconnected structure promote the critical investigation of artificial muscles geometry and implementation in the design phase of certain platforms. Biomimetic robots and Humanoid Robot heads with Facial Expressions (HRwFE) are some of the typical platforms that can be used to study the geometrical effects of artificial muscles. It has been shown that electroactive polymer and shape memory alloy artificial muscles and their composites are some of the candidate materials that may replicate natural muscles and showed great promise for biomimetics and humanoid robots. The application of these materials to these systems reveals the challenges and associated technologies that need to be developed in parallel. This paper will focus on the computer aided design (CAD) models of conductive polymer and shape memory alloys in various biomimetic systems and Humanoid Robot with Facial Expressions (HRwFE). The design of these systems will be presented in a comparative manner primarily focusing on three critical parameters: the stress, the strain and the geometry of the artificial muscle.

  19. Polymer-Free Biolimus A9-Coated Stents in the Treatment of De Novo Coronary Lesions: 4- and 12-Month Angiographic Follow-Up and Final 5-Year Clinical Outcomes of the Prospective, Multicenter BioFreedom FIM Clinical Trial.

    PubMed

    Costa, Ricardo A; Abizaid, Alexandre; Mehran, Roxana; Schofer, Joachim; Schuler, Gerhard C; Hauptmann, Karl E; Magalhães, Marco A; Parise, Helen; Grube, Eberhard

    2016-01-11

    The purpose of this study was to evaluate the efficacy and long-term outcomes of a novel polymer/carrier-free drug-coated stent (DCS) in patients with de novo coronary lesions. The BioFreedom (BFD) DCS incorporates a low-profile, stainless-steel platform, with a surface that has been modified to create a selectively microstructured abluminal surface that allows adhesion and further release of Biolimus A9 (Biosensors Europe SA, Morges, Switzerland). A total of 182 patients (183 lesions) were randomized into a 1:1:1 ratio for treatment with BFD "standard dose" (BFD) or BFD "low dose" (BFD-LD) versus first-generation paclitaxel-eluting stents (PES) at 4 sites in Germany. Baseline and procedural characteristics were well matched. At 4-month angiographic follow-up (Cohort 1, n = 75), in-stent late lumen loss (LLL) was significantly lower with BFD and BFD-LD versus PES (0.08 and 0.12 mm vs. 0.37 mm, respectively; p < 0.0001 for BFD vs. PES, and p = 0.002 for BFD-LD vs. PES). At 12 months (Cohort 2, n = 107), in-stent LLL (primary endpoint) was 0.17 mm in BFD versus 0.35 mm in PES (p = 0.001 for noninferiority; p = 0.11 for superiority); however, the BFD-LD (0.22 mm) did not reach noninferiority (p = 0.21). At 5 years (175 of 182), there were no significant differences in major adverse cardiac events (23.8%, 26.4%, and 20.3%) and clinically indicated target lesion revascularization (10.8%, 13.4%, and 10.2%) for BFD, BFD-LD, and PES, respectively; also, there was no definite/probable stent thrombosis reported. The BFD, but not the BFD-LD, demonstrated noninferiority versus PES in terms of in-stent LLL, a surrogate of neointimal hyperplasia, at 12-month follow-up. At 5 years, clinical event rates were similar, without occurrence of stent thrombosis in all groups. (BioFreedom FIM Clinical Trial; NCT01172119). Copyright © 2016 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

  20. Ferroelectric polymer thin films for solid-state non-volatile random access memory applications

    NASA Astrophysics Data System (ADS)

    Kaza, Swaroop

    Electronic polymers offer significant advantages towards ubiquitous computing due to their low-cost, flexibility and benign fabrication conditions. In this research, ferroelectric polymers were investigated for usage in non-volatile memory applications. The work is focused on the fabrication and ferroelectricity of Polyvinylidene-trifluoroethylene and Polyamide-11 (Nylon-11) thin films. Polyvinylidene fluoride (PVDF) and its copolymers were the first class of ferroelectric polymers discovered. Although the processes and properties of PVDF and copolymers have been extensively studied, most of the reports have been on polymers in the bulk form. This work focuses on thin films of PVDF-TrFE (75:25) copolymer fabricated by solution spin-casting. Remnant polarization, Pr, of the thin films was measured to be 6 muC/cm 2 with a coercive field, Ec, of 60 MV/m. The thin film properties are highly dependent on the temperature of crystallization and is attributed to the amount of all-trans beta-phase and crystallinity. Fatigue, defined as polarization loss with repeated switching, was studied and a model based on space charge formation was proposed as the fatigue mechanism. Space charge formation was proposed to be caused by electrochemical reaction of ions (F-) at electrodes and accumulations of detrapped ions at grain boundaries. Incorporating a F- scavenger and forming small crystallites was both observed to decrease fatigue. Nylon-11 and other odd-nylons are the only other class of polymers that have been reported to exhibit ferroelectric D-E hysteresis. The published work has almost exclusively been reported on melt-quenched and cold-drawn bulk polymers and consequently there is no literature on ferroelectricity in thin film odd-nylons. The present work developed a process for the fabrication of ferroelectric thin films of nylon-11 by spin-casting. Among the solvents tested, only a solution with m-cresol was observed to result in ferroelectricity in spun films and could

  1. Polymer (PTFE) and shape memory alloy (NiTi) intercalated nano-biocomposites

    NASA Astrophysics Data System (ADS)

    Anjum, S. S.; Rao, J.; Nicholls, J. R.

    2012-09-01

    Engineering on a nano-scale has been undertaken to mimic a biomaterial by forming an intercalated nano-composite structure by PVD sputtering of a polymer with a nickel-titanium (NiTi) shape memory alloy (SMA). A PTFE polymer has been selected due to its elastic properties, low interactions with water, optimum surface energies, stability and chemical resistance. NiTi SMAs allow the coatings to be energy absorbent and thus suitable in load bearing situations. The coatings are aimed to constantly withstand variable adverse biological environments whilst maintaining their characteristics. The nano-intercalated structures have been characterised for their wettability, friction coefficients, chemical composition, and morphology. Intercalation of a polymer with energy-absorbing alloys uncovers a set of material systems that will offer characteristics such as self-healing of hierarchal tissue in the body. The reformation of PTFE following sputter deposition was confirmed by FTIR spectra. According to SEM analysis PTFE shows a promising surface interaction with NiTi, forming stable coatings. Surface interactions are evident by the hydrophobic behaviour of films as the composite's water contact angle is around 86° which lies in-between that of PTFE and NiTi. The nano composite films are lubricious and have a measured CoF below 0.2 which does not vary with layer thickness.

  2. Micro-mechanics of nanostructured carbon/shape memory polymer hybrid thin film.

    PubMed

    Lei, Ming; Xu, Ben; Pei, Yutao; Lu, Haibao; Fu, Yong Qing

    2016-01-07

    This paper investigates the mechanics of hybrid shape memory polymer polystrene (PS) based nanocomposites with skeletal structures of CNFs/MWCNTs formed inside. Experimental results showed an increase of glass transition temperature (Tg) with CNF/MWCNT concentrations instead of a decrease of Tg in nanocomposites filled by spherical particles, and an increase in mechanical properties on both macro- and μm-scales. Compared with CNFs, MWCNTs showed a better mechanical enhancement for PS nanocomposites due to their uniform distribution in the nanocomposites. In nanoindentation tests using the Berkovich tips, indentation size effects and pile-up effects appeared obviously for the nanocomposites, but not for pure PS. Experimental results revealed the enhancement mechanisms of CNFs/MWCNTs related to the secondary structures formed by nanofillers, including two aspects, i.e., filler-polymer interfacial connections and geometrical factors of nanofillers. The filler-polymer interfacial connections were strongly dependent on temperature, thus leading to the opposite changing trend of loss tangent with nanofiller concentrations, respectively, at low and high temperature. The geometrical factors of nanofillers were related to testing scales, further leading to the appearance of pile-up effects for nanocomposites in the nanoindentation tests, in which the size of indents was close to the size of the nanofiller skeleton.

  3. In vivo evaluation of the third generation biodegradable stent: a novel approach to avoiding the forgotten stent syndrome.

    PubMed

    Chew, Ben H; Paterson, Ryan F; Clinkscales, Kenneth W; Levine, Barry S; Shalaby, Shalaby W; Lange, Dirk

    2013-02-01

    Ureteral stents are prone to irritation, encrustation and infection, and they require additional procedures for removal. Furthermore, indwelling polymer stents are often forgotten with devastating consequences to the patient. We describe the degradation time, and physiological and histological responses elicited by a novel biodegradable ureteral stent in a porcine model. A total of 16 female Yorkshire pigs were used in the study. Ten biodegradable Uriprene™ stents and 6 biostable Polaris™ stents were cystoscopically inserted unilaterally in 2 groups of animals. Excretory urogram, and blood and urine tests were performed on different days until day 28. Biostable stents were removed on day 21. On day 28 all pigs underwent necropsy for microscopic and histological evaluation. Nine of the 10 biodegradable stents (90%) degraded completely by 4 weeks, while 1 pig had 3 fragments smaller than 1.5 cm in the bladder. Excretory urogram showed equivalent drainage and significantly less hydronephrosis in biodegradable stented kidneys. Blood and urine parameters were similar in the 2 groups. A transient increase in serum creatinine on day 7 in 40% of the pigs with a degradable stent resolved by day 10. There were significantly fewer abnormal histological findings in the degradable stent group. We evaluated drainage characteristics in an unobstructed ureter and results may not be representative of what develops in obstructed ureters. The third generation biodegradable stent is a safe, effective alternative to conventional polymer stents, resulting in equivalent drainage and less hydronephrosis. Copyright © 2013 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.

  4. Drug-eluting versus bare-metal coronary stents: where are we now?

    PubMed

    Amoroso, Nicholas S; Bangalore, Sripal

    2012-11-01

    Drug-eluting stents have dramatically reduced the risk of restenosis, but concerns of an increased risk of stent thrombosis have provided uncertainty about their use. Recent studies have continued to show improved procedural and clinical outcomes with drug-eluting stents both in the setting of acute coronary syndromes and stable coronary artery disease. Newer generation drug-eluting stents (especially everolimus-eluting stents) have been shown to be not only efficacious but also safe with reduced risk of stent thrombosis when compared with bare-metal stents, potentially changing the benchmark for stent safety from bare-metal stents to everolimus-eluting stents. While much progress is being made in the development of bioabsorbable polymer stents, nonpolymer stents and bioabsorbable stent technology, it remains to be seen whether these stents will have superior safety and efficacy outcomes compared with the already much improved rates of revascularization and stent thrombosis seen with newer generation stents (everolimus-eluting stents and resolute zotarolimus-eluting stents).

  5. Biodegradable shape-memory polymers exhibiting sharp thermal transitions and controlled drug release.

    PubMed

    Nagahama, Koji; Ueda, Yuichi; Ouchi, Tatsuro; Ohya, Yuichi

    2009-07-13

    Biodegradable shape-memory polymer networks prepared by cross-linking star shape branched oligo(ε-caprolactone) (bOCL) with hexamethylene diisocyanate are introduced. The thermal and mechanical properties of these networks were investigated using differential scanning calorimetry and tensile testing, respectively, and the morphology of the phase structure was characterized by polarized optical microscopy. The shape-memory properties of the networks were quantified using thermomechanical tensile experiments and showed strain fixity rates R(f) higher than 97% and strain recovery rates R(r) as high as 100%. Of note, networks of OCL segments with a lower degree of polymerization (DP; 10) exhibited significantly improved temperature-sensitive shape recovery: 90% of the permanent shape was recovered upon heating to within a 2 °C range (37-39 °C). The networks exhibited complete shape recovery to the permanent shape within 10 s at 42 °C. Theophylline-loaded (10 and 20 wt %) shape-memory materials, prepared by cross-linking bOCL with hexamethylene diisocyanate in the presence of theophylline, are also described as a model for a controlled drug release device. The 10 wt % loaded material was sufficiently soft and flexible for complex shape transformation and also showed high R(f) (98%) and R(r) (99%). Sustained release of loaded theophylline was achieved over 1 month without initial burst-release in a phosphate buffer solution (PBS; pH 7.4) at 37 °C.

  6. Mechanical analysis of carbon fiber reinforced shape memory polymer composite for self-deployable structure in space environment

    NASA Astrophysics Data System (ADS)

    Hong, Seok Bin; Ahn, Yong San; Jang, Joon Hyeok; Kim, Jin-Gyun; Goo, Nam Seo; Yu, Woong-Ryeol

    2016-04-01

    Shape memory polymer (SMP) is one of smart polymers which exhibit shape memory effect upon external stimuli. Reinforcements as carbon fiber had been used for making shape memory polymer composite (CF-SMPC). This study investigated a possibility of designing self-deployable structures in harsh space condition using CF-SMPCs and analyzed their shape memory behaviors with constitutive equation model.CF-SMPCs were prepared using woven carbon fabrics and a thermoset epoxy based SMP to obtain their basic mechanical properties including actuation in harsh environment. The mechanical and shape memory properties of SMP and CF-SMPCs were characterized using dynamic mechanical analysis (DMA) and universal tensile machine (UTM) with an environmental chamber. The mechanical properties such as flexural strength and tensile strength of SMP and CF-SMPC were measured with simple tensile/bending test and time dependent shape memory behavior was characterized with designed shape memory bending test. For mechanical analysis of CF-SMPCs, a 3D constitutive equation of SMP, which had been developed using multiplicative decomposition of the deformation gradient and shape memory strains, was used with material parameters determined from CF-SMPCs. Carbon fibers in composites reinforced tensile and flexural strength of SMP and acted as strong elastic springs in rheology based equation models. The actuation behavior of SMP matrix and CF-SMPCs was then simulated as 3D shape memory bending cases. Fiber bundle property was imbued with shell model for more precise analysis and it would be used for prediction of deploying behavior in self-deployable hinge structure.

  7. Comparison of two biodegradable-polymer-based sirolimus-eluting stents with varying elution and absorption kinetics in patients with acute myocardial infarction: A subgroup analysis of the PANDA III trial.

    PubMed

    Guan, Changdong; Xu, Bo; Qiao, Shubin; Qin, Lei; Li, Yi; Li, Zhanquan; Guo, Yong; Sun, Zhongwei; Song, Lei; Gao, Runlin

    2017-03-01

    Implantation of early-generation metallic drug-eluting stents (DES) in patients with acute myocardial infarction (AMI) is associated with poor vessel wall healing. Use of biodegradable polymer (BP) DES might improve safety outcomes; however, the impact of varying drug elution and polymer absorption kinetics of BP-DES on clinical outcomes in the AMI population is unknown. This subgroup analysis of the randomized PANDA III trial included 732 patients (366 in each group) presenting with recent (<1 month) AMI. Primary endpoint was 1-year target lesion failure (TLF), a composite of cardiac death, target vessel myocardial infarction (MI), or ischemia-driven target lesion revascularization. Secondary endpoints included a patient-oriented composite endpoint (PoCE) of all-cause death, all MI, or any revascularization; individual TLF and PoCE components; and definite/probable stent thrombosis (ST). There were no significant differences between-groups in baseline clinical, angiographic, or procedural characteristics other than the proportion of post-dilatation, which was performed more frequently with the BuMA stent (53.9% vs. 44.5%; P = 0.004). After 1 year, compared to Excel SES implantation in patients with AMI, BuMA was associated with similar incidences of TLF and PoCE (5.5% vs. 8.3%, P = 0.14; 8.8% vs. 9.9%, P = 0.61, respectively) but lower incidences of MI (2.5% vs. 6.1%, P = 0.02), target vessel MI (2.2% vs. 5.8%, P = 0.01), and definite/probable ST (0.3% vs. 2.2%, P = 0.04). BuMA SES, with faster drug elution rate and polymer absorption kinetics, might improve safety outcomes compared to Excel SES in the high-risk AMI population. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  8. A randomized optical coherence tomography study of coronary stent strut coverage and luminal protrusion with rapamycin-eluting stents.

    PubMed

    Moore, Philip; Barlis, Peter; Spiro, Jonathan; Ghimire, Gopal; Roughton, Michael; Di Mario, Carlo; Wallis, William; Ilsley, Charles; Mitchell, Andrew; Mason, Mark; Kharbanda, Rajesh; Vincent, Peter; Sherwin, Spencer; Dalby, Miles

    2009-05-01

    We used optical coherence tomography, which has a resolution of <20 microm, to analyze thin layers of neointima in rapamycin-eluting coronary stents. Lack of neointimal coverage has been implicated in the pathogenesis of drug-eluting coronary stent thrombosis. Angiography and intracoronary ultrasound lack the resolution to examine this. We conducted a randomized trial in patients receiving polymer-coated rapamycin-eluting stents (Cypher, Cordis, Johnson & Johnson, Miami, Florida) and nonpolymer rapamycin-eluting stents (Yukon, Translumina, Hechingen, Germany) to examine neointimal thickness, stent strut coverage, and protrusion at 90 days. Twenty-four patients (n = 12 for each group) underwent stent deployment and invasive follow-up at 90 days with optical coherence tomography. The primary end point was binary stent strut coverage. Coprimary end points were neointimal thickness and stent strut luminal protrusion. No patient had angiographic restenosis. For polymer-coated and nonpolymer rapamycin-eluting stents, respectively, mean (SD), neointimal thickness was 77.2 (25.6) microm versus 191.2 (86.7) mum (p < 0.001). Binary stent strut coverage was 88.3% (11.8) versus 97.2% (6.1) (p = 0.030). Binary stent strut protrusion was 26.5% (17.5) versus 4.8% (8.6) (p = 0.001). Mean neointimal thickness for the polymer-coated rapamycin-eluting stent was significantly less than the nonpolymer rapamycin-eluting stent but as a result coverage was not homogenous, with >10% of struts being uncovered. High-resolution imaging allowed development of the concept of the protrusion index, and >25% of struts protruded into the vessel lumen with the polymer-coated rapamycin-eluting stent compared with <5% with the nonpolymer rapamycin-eluting stent. These findings may have important implications for the risk of stent thrombosis and, therefore, future stent design. (An optical coherence tomography study to determine stent coverage in polymer coated versus bare metal rapamycin eluting

  9. Coarse-grained simulation of molecular mechanisms of recovery in thermally activated shape-memory polymers

    NASA Astrophysics Data System (ADS)

    Abberton, Brendan C.; Liu, Wing Kam; Keten, Sinan

    2013-12-01

    Thermally actuated shape-memory polymers (SMPs) are capable of being programmed into a temporary shape and then recovering their permanent reference shape upon exposure to heat, which facilitates a phase transition that allows dramatic increase in molecular mobility. Experimental, analytical, and computational studies have established empirical relations of the thermomechanical behavior of SMPs that have been instrumental in device design. However, the underlying mechanisms of the recovery behavior and dependence on polymer microstructure remain to be fully understood for copolymer systems. This presents an opportunity for bottom-up studies through molecular modeling; however, the limited time-scales of atomistic simulations prohibit the study of key performance metrics pertaining to recovery. In order to elucidate the effects of phase fraction, recovery temperature, and deformation temperature on shape recovery, here we investigate the shape-memory behavior in a copolymer model with coarse-grained potentials using a two-phase molecular model that reproduces physical crosslinking. Our simulation protocol allows observation of upwards of 90% strain recovery in some cases, at time-scales that are on the order of the timescale of the relevant relaxation mechanism (stress relaxation in the unentangled soft-phase). Partial disintegration of the glassy phase during mechanical deformation is found to contribute to irrecoverable strain. Temperature dependence of the recovery indicates nearly full elastic recovery above the trigger temperature, which is near the glass-transition temperature of the rubbery switching matrix. We find that the trigger temperature is also directly correlated with the deformation temperature, indicating that deformation temperature influences the recovery temperatures required to obtain a given amount of shape recovery, until the plateau regions overlap above the transition region. Increasing the fraction of glassy phase results in higher strain

  10. A Shape Memory Polymer Dialysis Needle Adapter for the Reduction of Hemodynamic Stress within Arteriovenous Grafts

    SciTech Connect

    Ortega, J M; Small, W; Wilson, T S; Benett, W; Loge, J; Maitland, D J

    2006-08-16

    A deployable, shape memory polymer adapter is investigated for reducing the hemodynamic stress caused by a dialysis needle flow within an arteriovenous graft. Computational fluid dynamics simulations of dialysis sessions with and without the adapter demonstrate that the adapter provides a significant decrease in the wall shear stress. In vitro flow visualization measurements are made within a graft model following delivery and actuation of a prototype shape memory polymer adapter. Vascular access complications resulting from arteriovenous (AV) graft failures account for over $1 billion per year in the health care costs of dialysis patients in the U.S.[1] The primary mode of failure of arteriovenous fistulas (AVF's) and polytetrafluoroethylene (PTFE) grafts is the development of intimal hyperplasia (IH) and the subsequent formation of stenotic lesions, resulting in a graft flow decline. The hemodynamic stresses arising within AVF's and PTFE grafts play an important role in the pathogenesis of IH. Studies have shown that vascular damage can occur in regions where there is flow separation, oscillation, or extreme values of wall shear stress (WSS).[2] Nevaril et al.[3] show that exposure of red blood cells to WSS's on the order of 1500 dynes/cm2 can result in hemolysis. Hemodynamic stress from dialysis needle flow has recently been investigated for the role it plays in graft failure. Using laser Doppler velocimetry measurements, Unnikrishnan et al.[4] show that turbulence intensities are 5-6 times greater in the AV flow when the needle flow is present and that increased levels of turbulence exist for approximately 7-8cm downstream of the needle. Since the AVF or PTFE graft is exposed to these high levels of hemodynamic stress several hours each week during dialysis sessions, it is quite possible that needle flow is an important contributor to vascular access occlusion.[4] We present a method for reducing the hemodynamic stress in an AV graft by tailoring the fluid

  11. A phenomenological formulation for the shape/temperature memory effect in amorphous polymers with multi-stress components

    NASA Astrophysics Data System (ADS)

    Lu, Haibao; Wang, Xiaodong; Yu, Kai; Huang, Wei Min; Yao, Yongtao; Leng, Jinsong

    2017-09-01

    By means of combining the influence of temperature and strain rate, and based on the cooperative Eyring model, a phenomenological formulation for the shape memory effect and temperature memory effect of an amorphous shape memory polymer (SMP) is proposed. The internal stress and stored mechanical energy are correlated to shape/temperature memory behaviours below and above the glass transition temperature. The working mechanism and fundamentals for the chemo-responsive shape memory behaviour in SMPs are further investigated in terms of the activation enthalpy parameter for inductive depression. Simulation using the proposed model is compared with the experimental results reported in the literature. Predictions are also made using the proposed model. This phenomenological framework is expected to provide a powerful tool for investigating the underlying thermomechanics that originate in the movement of cooperative segments and segmental relaxations in SMPs.

  12. Study on the activation of styrene-based shape memory polymer by medium-infrared laser light

    SciTech Connect

    Leng Jinsong; Yu Kai; Lan Xin; Zhang Dawei; Liu Yanju

    2010-03-15

    This paper demonstrates the feasibility of shape memory polymer (SMP) activation by medium-infrared laser light. Medium-infrared light is transmitted by an optical fiber embedded in the SMP matrix, and the shape recovery process and temperature distribution are recorded by an infrared camera. Light-induced SMP exhibits potential applications in biomedicines and flexible displays.

  13. Study on the activation of styrene-based shape memory polymer by medium-infrared laser light

    NASA Astrophysics Data System (ADS)

    Leng, Jinsong; Zhang, Dawei; Liu, Yanju; Yu, Kai; Lan, Xin

    2010-03-01

    This paper demonstrates the feasibility of shape memory polymer (SMP) activation by medium-infrared laser light. Medium-infrared light is transmitted by an optical fiber embedded in the SMP matrix, and the shape recovery process and temperature distribution are recorded by an infrared camera. Light-induced SMP exhibits potential applications in biomedicines and flexible displays.

  14. Intravascular imaging comparison of two metallic limus-eluting stents abluminally coated with biodegradable polymers: IVUS and OCT results of the DESTINY trial.

    PubMed

    Costa, J Ribamar; Chamié, Daniel; Abizaid, Alexandre A C; Ribeiro, Expedito; Meireles, George C; Prudente, Maurício; Campos, Carlos A; Castro, Juliana P; Costa, Ricardo; Lemos, Pedro A

    2017-02-01

    We sought to compare, by means of IVUS and OCT imaging, the performance of a novel sirolimus-eluting drug-eluting stent (DES) with biodegradable polymer (Inspiron™) to the Biomatrix™ DES. From the DESTINY trial, a total of 70 randomized patients (2:1) were enrolled in the IVUS substudy (Inspiron™, n = 46; Biomatrix™: n = 20) while 25 patients were evaluated with OCT (Inspiron™, n = 19; Biomatrix™: n = 06) at 9-month follow-up. The main endpoints were % of neointimal tissue obstruction (IVUS) and neointimal stut coverage (OCT) at 9 months. Patients treated with both DES had very little NIH formation at 9 months either by IVUS (% of NIH obstruction of 4.9 ± 4.1 % with Inspiron™ vs. 2.7 ± 2.9 % with Biomatrix™, p = 0.03) or by OCT (neointimal thickness of 144.2 ± 72.5 µm Inspiron™ vs. 115.0 ± 53.9 µm with Biomatrix™, p = 0.45). Regarding OCT strut-level assessment, again both devices showed excellent 9-month performance, with high rates of strut coverage (99.49 ± 1.01 % with Inspiron™ vs. 97.62 ± 2.21 % with Biomatrix™, p < 0.001) and very rare malapposition (0.29 ± 1.06 % with Inspiron™ vs. 0.53 ± 0.82 % with Biomatrix™, p = 0.44). Patients with any uncovered struts were more frequently identified in the Biomatrix™ group (9.78 ± 7.13 vs. 2.29 ± 3.91 %, p < 0.001). In the present study, midterm IVUS and OCT evaluations showed that both new generation DES with biodegradable polymer were effective in terms of suppressing excessive neointimal response, with very high rates of apposed and covered struts, suggesting a consistent and benign healing pattern.

  15. Recent developments in drug-eluting coronary stents.

    PubMed

    Yildiz, Mustafa; Yildiz, Banu Sahin; Gursoy, Mustafa Ozan; Akin, Ibrahim

    2014-01-01

    The interventional treatment of coronary artery disease was introduced in 1970`s by Andreas Grüntzig. The initial treatment strategy with plain old balloon angioplasty (POBA) was associated with high restenosis rates. The introduction of coronary stents, especially drug-eluting stents (DES) in 2002 has improved the results by lowering the rate of in-stent restenosis from 20-40% in the era of bare-metal stent (BMS) to 6-8%. However, in 2006 with the observation of late stent thrombosis the reputations of DES have decreased. However, improvements in stent design especially antiproliferative agents, polymeric agents as well as stent platforms improved newer generation DES. In controlled trials as well as registries the use of second-generation DES as compared to bare-metal stents (BMS) was associated with better clinical and angiographic results. A further development of these stents with use of biodegradable polymers, polymer-free stents, and biodegradable stents on the basis of poly L-lactide (PLLA) or magnesium resulted in third-generation DES and has been evaluated in preclinical and first clinical trials. However, to date, there is a lack of data comparing these third-generation DES with first- and second-generatrion DES in a large scale.

  16. Development of high shrinkage polyethylene terephthalate (PET) shape memory polymer tendons for concrete crack closure

    NASA Astrophysics Data System (ADS)

    Teall, Oliver; Pilegis, Martins; Sweeney, John; Gough, Tim; Thompson, Glen; Jefferson, Anthony; Lark, Robert; Gardner, Diane

    2017-04-01

    The shrinkage force exerted by restrained shape memory polymers (SMPs) can potentially be used to close cracks in structural concrete. This paper describes the physical processing and experimental work undertaken to develop high shrinkage die-drawn polyethylene terephthalate (PET) SMP tendons for use within a crack closure system. The extrusion and die-drawing procedure used to manufacture a series of PET tendon samples is described. The results from a set of restrained shrinkage tests, undertaken at differing activation temperatures, are also presented along with the mechanical properties of the most promising samples. The stress developed within the tendons is found to be related to the activation temperature, the cross-sectional area and to the draw rate used during manufacture. Comparisons with commercially-available PET strip samples used in previous research are made, demonstrating an increase in restrained shrinkage stress by a factor of two for manufactured PET filament samples.

  17. Magnetic Resonance Flow Velocity and Temperature Mapping of a Shape Memory Polymer Foam Device

    SciTech Connect

    Small IV, W; Gjersing, E; Herberg, J L; Wilson, T S; Maitland, D J

    2008-10-29

    Interventional medical devices based on thermally responsive shape memory polymer (SMP) are under development to treat stroke victims. The goals of these catheter-delivered devices include re-establishing blood flow in occluded arteries and preventing aneurysm rupture. Because these devices alter the hemodynamics and dissipate thermal energy during the therapeutic procedure, a first step in the device development process is to investigate fluid velocity and temperature changes following device deployment. A laser-heated SMP foam device was deployed in a simplified in vitro vascular model. Magnetic resonance imaging (MRI) techniques were used to assess the fluid dynamics and thermal changes associated with device deployment. Spatial maps of the steady-state fluid velocity and temperature change inside and outside the laser-heated SMP foam device were acquired. Though non-physiological conditions were used in this initial study, the utility of MRI in the development of a thermally-activated SMP foam device has been demonstrated.

  18. Synergic effect of carbon black and short carbon fiber on shape memory polymer actuation by electricity

    NASA Astrophysics Data System (ADS)

    Leng, Jinsong; Lv, Haibao; Liu, Yanju; Du, Shanyi

    2008-11-01

    This paper presents a study on the effect of carbon black (CB) and short carbon fibers (SCFs) on shape memory polymer (SMP) actuation by applying electric current. The coexistence of CB and SCF electrically conductive networks, supporting each other, resulting in significant improvement of electrical properties, was supported by optical microscopy, while the roles of particulate and fibrous fillers were distinguished by scanning electron microscopy. In sequence, the volume resistivity curves of one filler systems and two fillers systems were figured out and compared. Moreover, experimental results substantiated that the actuation voltage of two-filler SMP composites' shape recovery was prominently lower in comparison with that of one-filler systems at the same filler content. Additional, the response of glass transition temperature (Tg) and thermomechanical properties to filler content and two fillers' synergic effect were characterized and illuminated experimentally.

  19. Effect of Biodegradable Shape-Memory Polymers on Proliferation of 3T3 Cells

    NASA Astrophysics Data System (ADS)

    Xu, Shuo-Gui; Zhang, Peng; Zhu, Guang-Ming; Jiang, Ying-Ming

    2011-07-01

    This article evaluates the in vitro biocompatibility for biodegradable shape-memory polymers (BSMP) invented by the authors. 3T3 cells (3T3-Swiss albino GNM 9) of primary and passaged cultures were inoculated into two kinds of carriers: the BSMP carrier and the control group carrier. Viability, proliferation, and DNA synthesis (the major biocompatibility parameters), were measured and evaluated for both the BSMP and naked carrier via cell growth curve analysis, MTT colorimetry and addition of 3H-TdR to culture media. The results showed that there was no difference between the BSMP carrier and the control dish in terms of viability, proliferation, and metabolism of the 3T3 cells. Overall, the BSMP carrier provides good biocompatibility and low toxicity to cells in vitro, and could indicate future potential for this medium as a biological material for implants in vivo.

  20. A constitutive theory for shape memory polymers: coupling of small and large deformation

    NASA Astrophysics Data System (ADS)

    Tan, Qiao; Liu, Liwu; Liu, Yanju; Leng, Jinsong; Yan, Xiangqiao; Wang, Haifang

    2013-04-01

    At high temperatures, SMPs share attributes like rubber and exhibit long-range reversibility. In contrast, at low temperatures they become very rigid and are susceptible to plastic, only small strains are allowable. But there relatively little literature has considered the unique small stain (rubber phase) and large stain (glass phase) coupling in SMPs when developing the constitutive modeling. In this work, we present a 3D constitutive model for shape memory polymers in both low temperature small strain regime and high temperature large strain regime. The theory is based on the work of Liu et al. [15]. Four steps of SMP's thermomechanical loadings cycle are considered in the constitutive model completely. The linear elastic and hyperelastic effects of SMP in different temperatures are also fully accounted for in the proposed model by adopt the neo-Hookean model and the Generalized Hooke's laws.

  1. Fabrication and Characterization of Cylindrical Light Diffusers Comprised of Shape Memory Polymer

    SciTech Connect

    Small IV, W; Buckley, P R; Wilson, T S; Loge, J M; Maitland, K D; Maitland, D J

    2007-01-29

    We have developed a technique for constructing light diffusing devices comprised of a flexible shape memory polymer (SMP) cylindrical diffuser attached to the tip of an optical fiber. Devices were fabricated by casting an SMP rod over the cleaved tip of an optical fiber and media blasting the SMP rod to create a light diffusing surface. The axial and polar emission profiles and circumferential (azimuthal) uniformity were characterized for various blasting pressures, nozzle-to-sample distances, and nozzle translation speeds. The diffusers were generally strongly forward-directed and consistently withstood over 8 W of incident infrared laser light without suffering damage when immersed in water. These devices are suitable for various endoluminal and interstitial biomedical applications.

  2. Photothermal Properties of Shape Memory Polymer Micro-Actuators for Treating Stroke

    SciTech Connect

    Maitland, D J; Metzger, M F; Schumann, D; Lee, A; Wilson, T S

    2001-03-05

    Objective--In this paper the photothermal design aspects of novel shape memory polymer (SMP) microactuators for treating stroke are presented. Materials and Methods--A total of three devices will be presented: two interventional ischemic stroke devices (coil and umbrella) and one device for releasing embolic coils (microgripper). The optical properties of SMP, methods for coupling laser light into SMP, heating distributions in the SMP devices and the impact of operating the thermally activated material in a blood vessel are presented. Results--Actuating the devices requires device temperatures in the range of 65 C-85 C. Attaining these temperatures under flow conditions requires critical engineering of the SMP optical properties, optical coupling into the SMP, and device geometries. Conclusion--Laser-activated SMP devices are a unique combination of laser-tissue and biomaterial technologies. Successful deployment of the microactuator requires well-engineered coupling of the light from the diffusing fiber through the blood into the SMP.

  3. Cytotoxicity and thermomechanical behavior of biomedical shape-memory polymer networks post-sterilization.

    PubMed

    Yakacki, C M; Lyons, M B; Rech, B; Gall, K; Shandas, R

    2008-03-01

    Shape-memory polymers (SMPs) are being increasingly proposed for use in biomedical devices. This paper investigates the cytotoxicity, surface characteristics and thermomechanics of two acrylate-based SMP networks as a function of sterilization using a minimal essential media elution test, FTIR-ATR and dynamic mechanical analysis (DMA). Networks sterilized by low-temperature plasma elicited a cytotoxic response and are shown to completely destroy the cell monolayer. FTIR-ATR analysis showed evidence of surface oxidation with an increase and broadening of the absorbance peak from approximately 3500 to 3100 cm(-1), which is associated with an increase in hydroxyl groups. DMA revealed small, but statistically significant, differences in reduction of the glass transition temperatures of both networks when sterilized with gamma irradiation. One network showed an increase in rubbery modulus, which is an indication of crosslink density, after gamma irradiation. Lastly, practical sterilization concerns of SMP devices are discussed in light of the different methods.

  4. Variable stiffness corrugated composite structure with shape memory polymer for morphing skin applications

    NASA Astrophysics Data System (ADS)

    Gong, Xiaobo; Liu, Liwu; Scarpa, Fabrizio; Leng, Jinsong; Liu, Yanju

    2017-03-01

    This work presents a variable stiffness corrugated structure based on a shape memory polymer (SMP) composite with corrugated laminates as reinforcement that shows smooth aerodynamic surface, extreme mechanical anisotropy and variable stiffness for potential morphing skin applications. The smart composite corrugated structure shows a low in-plane stiffness to minimize the actuation energy, but also possess high out-of-plane stiffness to transfer the aerodynamic pressure load. The skin provides an external smooth aerodynamic surface because of the one-sided filling with the SMP. Due to variable stiffness of the shape memory polymer the morphing skin exhibits a variable stiffness with a change of temperature, which can help the skin adjust its stiffness according different service environments and also lock the temporary shape without external force. Analytical models related to the transverse and bending stiffness are derived and validated using finite element techniques. The stiffness of the morphing skin is further investigated by performing a parametric analysis against the geometry of the corrugation and various sets of SMP fillers. The theoretical and numerical models show a good agreement and demonstrate the potential of this morphing skin concept for morphing aircraft applications. We also perform a feasibility study of the use of this morphing skin in a variable camber morphing wing baseline. The results show that the morphing skin concept exhibits sufficient bending stiffness to withstand the aerodynamic load at low speed (less than 0.3 Ma), while demonstrating a large transverse stiffness variation (up to 191 times) that helps to create a maximum mechanical efficiency of the structure under varying external conditions.

  5. Silicone membranes to inhibit water uptake into thermoset polyurethane shape-memory polymer conductive composites

    DOE PAGES

    Yu, Ya-Jen; Infanger, Stephen; Grunlan, Melissa A.; ...

    2014-07-24

    Electroactive shape memory polymer (SMP) composites capable of shape actuation via resistive heating are of interest for various biomedical applications. However, water uptake into SMPs will produce a depression of the glass transition temperature (Tg) resulting in shape recovery in vivo. While water actuated shape recovery may be useful, it is foreseen to be undesirable during early periods of surgical placement into the body. Silicone membranes have been previously reported to prevent release of conductive filler from an electroactive polymer composite in vivo. In this paper, a silicone membrane was used to inhibit water uptake into a thermoset SMP compositemore » containing conductive filler. Thermoset polyurethane SMPs were loaded with either 5 wt % carbon black or 5 wt % carbon nanotubes, and subsequently coated with either an Al2O3- or silica-filled silicone membrane. It was observed that the silicone membranes, particularly the silica-filled membrane, reduced the rate of water absorption (37°C) and subsequent Tg depression versus uncoated composites. Finally, in turn, this led to a reduction in the rate of recovery of the permanent shape when exposed to water at 37°C.« less

  6. Silicone membranes to inhibit water uptake into thermoset polyurethane shape-memory polymer conductive composites

    SciTech Connect

    Yu, Ya-Jen; Infanger, Stephen; Grunlan, Melissa A.; Maitland, Duncan J.

    2014-07-24

    Electroactive shape memory polymer (SMP) composites capable of shape actuation via resistive heating are of interest for various biomedical applications. However, water uptake into SMPs will produce a depression of the glass transition temperature (Tg) resulting in shape recovery in vivo. While water actuated shape recovery may be useful, it is foreseen to be undesirable during early periods of surgical placement into the body. Silicone membranes have been previously reported to prevent release of conductive filler from an electroactive polymer composite in vivo. In this paper, a silicone membrane was used to inhibit water uptake into a thermoset SMP composite containing conductive filler. Thermoset polyurethane SMPs were loaded with either 5 wt % carbon black or 5 wt % carbon nanotubes, and subsequently coated with either an Al2O3- or silica-filled silicone membrane. It was observed that the silicone membranes, particularly the silica-filled membrane, reduced the rate of water absorption (37°C) and subsequent Tg depression versus uncoated composites. Finally, in turn, this led to a reduction in the rate of recovery of the permanent shape when exposed to water at 37°C.

  7. Silicone Membranes to Inhibit Water Uptake into Thermoset Polyurethane Shape-Memory Polymer Conductive Composites

    PubMed Central

    Yu, Ya-Jen; Infanger, Stephen; Grunlan, Melissa A.; Maitland, Duncan J.

    2014-01-01

    Electroactive shape memory polymer (SMP) composites capable of shape actuation via resistive heating are of interest for various biomedical applications. However, water uptake into SMPs will produce a depression of the glass transition temperature (Tg) resulting in shape recovery in vivo. While water actuated shape recovery may be useful, it is foreseen to be undesirable during early periods of surgical placement into the body. Silicone membranes have been previously reported to prevent release of conductive filler from an electroactive polymer composite in vivo. In this study, a silicone membrane was used to inhibit water uptake into a thermoset SMP composite containing conductive filler. Thermoset polyurethane (PU) SMPs were loaded with either 5 wt% carbon black (CB) or 5 wt% carbon nanotubes (CNT) and subsequently coated with either an Al2O3- or silica-filled silicone membrane. It was observed that the silicone membranes, particularly the silica-filled membrane, reduced the rate of water absorption (37 °C) and subsequent Tg depression versus uncoated composites. In turn, this led to a reduction in the rate of recovery of the permanent shape when exposed to water at 37 °C. PMID:25663711

  8. Silicone Membranes to Inhibit Water Uptake into Thermoset Polyurethane Shape-Memory Polymer Conductive Composites.

    PubMed

    Yu, Ya-Jen; Infanger, Stephen; Grunlan, Melissa A; Maitland, Duncan J

    2015-01-05

    Electroactive shape memory polymer (SMP) composites capable of shape actuation via resistive heating are of interest for various biomedical applications. However, water uptake into SMPs will produce a depression of the glass transition temperature (Tg ) resulting in shape recovery in vivo. While water actuated shape recovery may be useful, it is foreseen to be undesirable during early periods of surgical placement into the body. Silicone membranes have been previously reported to prevent release of conductive filler from an electroactive polymer composite in vivo. In this study, a silicone membrane was used to inhibit water uptake into a thermoset SMP composite containing conductive filler. Thermoset polyurethane (PU) SMPs were loaded with either 5 wt% carbon black (CB) or 5 wt% carbon nanotubes (CNT) and subsequently coated with either an Al2O3- or silica-filled silicone membrane. It was observed that the silicone membranes, particularly the silica-filled membrane, reduced the rate of water absorption (37 °C) and subsequent Tg depression versus uncoated composites. In turn, this led to a reduction in the rate of recovery of the permanent shape when exposed to water at 37 °C.

  9. Development of siloxane-based amphiphiles as cell stabilizers for porous shape memory polymer systems.

    PubMed

    Hasan, Sayyeda M; Easley, Alexandra D; Monroe, Mary Beth Browning; Maitland, Duncan J

    2016-09-15

    Polyurethane foaming surfactants are cell stabilized at the polymer-gas interface during foam blowing to prevent bubble coalescence. Siloxane-based surfactants are typically used to generate a surface tension gradient at the interface. The chemical structure of the hydrophobic and hydrophilic units affects surfactant properties, which can further influence foam morphology. Siloxane-polyethylene glycol (PEG) ether amphiphiles were synthesized in high yield via hydrosilylation to serve as surfactants for shape memory polymer (SMP) foams. Hydrophobic units consisted of trisiloxane and polydimethyl siloxane, and PEG allyl methyl ether (n=8 or 25) was the hydrophilic component. Upon confirming successful synthesis of the surfactants, their surface tension was measured to study their suitability for use in foaming. SMP foams were synthesized using the four surfactants, and the effects of surfactant structure and concentration on foam morphology were evaluated. Spectroscopic data confirmed successful siloxane-PEG coupling. All surfactants had a low surface tension of 20-21mN/m, indicating their ability to reduce interfacial tension. SMP foams were successfully fabricated with tunable cell size and morphology as a function of surfactant type and concentration. Copyright © 2016. Published by Elsevier Inc.

  10. Plasma immersion ion implantation of polyurethane shape memory polymer: Surface properties and protein immobilization

    NASA Astrophysics Data System (ADS)

    Cheng, Xinying; Kondyurin, Alexey; Bao, Shisan; Bilek, Marcela M. M.; Ye, Lin

    2017-09-01

    Polyurethane-type shape memory polymers (SMPU) are promising biomedical implant materials due to their ability to recover to a predetermined shape from a temporary shape induced by thermal activation close to human body temperature and their advantageous mechanical properties including large recovery strains and low recovery stresses. Plasma Immersion Ion Implantation (PIII) is a surface modification process using energetic ions that generates radicals in polymer surfaces leading to carbonisation and oxidation and the ability to covalently immobilise proteins without the need for wet chemistry. Here we show that PIII treatment of SMPU significantly enhances its bioactivity making SMPU suitable for applications in permanent implantable biomedical devices. Scanning Electron Microscopy (SEM), contact angle measurements, surface energy measurements, attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to characterise the PIII modified surface, including its after treatment aging kinetics and its capability to covalently immobilise protein directly from solution. The results show a substantial improvement in wettability and dramatic changes of surface chemical composition dependent on treatment duration, due to the generation of radicals and subsequent oxidation. The SMPU surface, PIII treated for 200s, achieved a saturated level of covalently immobilized protein indicating that a full monolayer coverage was achieved. We conclude that PIII is a promising and efficient surface modification method to enhance the biocompatibility of SMPU for use in medical applications that demand bioactivity for tissue integration and stability in vivo.

  11. Modification of Shape Memory Polymer Foams Using Tungsten, Aluminum Oxide, and Silicon Dioxide Nanoparticles.

    PubMed

    Hasan, S M; Thompson, R S; Emery, H; Nathan, A L; Weems, A C; Zhou, F; Monroe, M B B; Maitland, D J

    Shape memory polymer (SMP) foams were synthesized with three different nanoparticles (tungsten, silicon dioxide, and aluminum oxide) for embolization of cerebral aneurysms. Ultra-low density SMP foams have previously been utilized for aneurysm occlusion, resulting in a rapid, stable thrombus. However, the small cross section of foam struts can potentially lead to fracture and particulate generation, which would be a serious adverse event for an embolic device. The goal of this study was to improve the mechanical properties of the system by physically incorporating fillers into the SMP matrix. Thermal and mechanical characterization suggested minimal changes in thermal transition of the SMP nanocomposites and improved mechanical strength and toughness for systems with low filler content. Actuation profiles of the three polymer systems were tuned with filler type and content, resulting in faster SMP foam actuation for nanocomposites containing higher filler content. Additionally, thermal stability of the SMP nanocomposites improved with increasing filler concentration, and particulate count remained well below accepted standard limits for all systems. Extraction studies demonstrated little release of silicon dioxide and aluminum oxide from the bulk over 16 days. Tungstun release increased over the 16 day examination period, with a maximum measured concentration of approxiately 2.87 μg/mL. The SMP nanocomposites developed through this research have the potential for use in medical devices due to their tailorable mechanical properties, thermal resisitivity, and actuation profiles.

  12. Shape Recovery with Concomitant Mechanical Strengthening of Amphiphilic Shape Memory Polymers in Warm Water

    DOE PAGES

    Zhang, Ben; DeBartolo, Janae E.; Song, Jie

    2017-01-26

    Maintaining adequate or enhancing mechanical properties of shape memory polymers (SMPs) after shape recovery in an aqueous environment are greatly desired for biomedical applications of SMPs as self-fitting tissue scaffolds or minimally invasive surgical implants. Here we report stable temporary shape fixing and facile shape recovery of biodegradable triblock amphiphilic SMPs containing a poly(ethylene glycol) (PEG) center block and flanking poly(lactic acid) or poly(lactic-co-glycolic acid) blocks in warm water, accompanied with concomitant enhanced mechanical strengths. Differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WXRD) and small-angle X-ray scattering (SAXS) analyses revealed that the unique stiffening of the amphiphilic SMPs upon hydrationmore » was due to hydration-driven microphase separation and PEG crystallization. We further demonstrated that the chemical composition of degradable blocks in these SMPs could be tailored to affect the persistence of hydration-induced stiffening upon subsequent dehydration. These properties combined open new horizons for these amphiphilic SMPs for smart weight-bearing in vivo applications (e.g. as self-fitting intervertebral discs). In conclusion, this study also provides a new material design strategy to strengthen polymers in aqueous environment in general.« less

  13. PCL-based Shape Memory Polymers with Variable PDMS Soft Segment Lengths

    PubMed Central

    Zhang, Dawei; Giese, Melissa L.; Prukop, Stacy L.; Grunlan, Melissa A.

    2012-01-01

    Thermoresponsive shape memory polymers (SMPs) are stimuli-responsive materials that return to their permanent shape from a temporary shape in response to heating. The design of new SMPs which obtain a broader range of properties including mechanical behavior is critical to realize their potential in biomedical as well as industrial and aerospace applications. To tailor the properties of SMPs, “AB networks” comprised of two distinct polymer components have been investigated but are overwhelmingly limited to those in which both components are organic. In this present work, we prepared inorganic-organic SMPs comprised of inorganic polydimethyl-siloxane (PDMS) segments of varying lengths and organic poly(ε-caprolactone) (PCL) segments. PDMS has a particularly low Tg (−125 °C) which makes it a particularly effective soft segment to tailor the mechanical properties of PCL-based SMPs. The SMPs were prepared via the rapid photocure of solutions of diacrylated PCL40-block-PDMSm-block-PCL40 macromers (m = 20, 37, 66 and 130). The resulting inorganic-organic SMP networks exhibited excellent shape fixity and recovery. By changing the PDMS segment length, the thermal, mechanical, and surface properties were systematically altered. PMID:22904597

  14. An annulus fibrosus closure device based on a biodegradable shape-memory polymer network.

    PubMed

    Sharifi, Shahriar; van Kooten, Theo G; Kranenburg, Hendrik-Jan C; Meij, Björn P; Behl, Marc; Lendlein, Andreas; Grijpma, Dirk W

    2013-11-01

    Injuries to the intervertebral disc caused by degeneration or trauma often lead to tearing of the annulus fibrosus (AF) and extrusion of the nucleus pulposus (NP). This can compress nerves and cause lower back pain. In this study, the characteristics of poly(D,L-lactide-co-trimethylene carbonate) networks with shape-memory properties have been evaluated in order to prepare biodegradable AF closure devices that can be implanted minimally invasively. Four different macromers with (D,L-lactide) to trimethylene carbonate (DLLA:TMC) molar ratios of 80:20, 70:30, 60:40 and 40:60 with terminal methacrylate groups and molecular weights of approximately 30 kg mol(-1) were used to prepare the networks by photo-crosslinking. The mechanical properties of the samples and their shape-memory properties were determined at temperatures of 0 °C and 40 °C by tensile tests- and cyclic, thermo-mechanical measurements. At 40 °C all networks showed rubber-like behavior and were flexible with elastic modulus values of 1.7-2.5 MPa, which is in the range of the modulus values of human annulus fibrosus tissue. The shape-memory characteristics of the networks were excellent with values of the shape-fixity and the shape-recovery ratio higher than 98 and 95%, respectively. The switching temperatures were between 10 and 39 °C. In vitro culture and qualitative immunocytochemistry of human annulus fibrosus cells on shape-memory films with DLLA:TMC molar ratios of 60:40 showed very good ability of the networks to support the adhesion and growth of human AF cells. When the polymer network films were coated by adsorption of fibronectin, cell attachment, cell spreading, and extracellular matrix production was further improved. Annulus fibrosus closure devices were prepared from these AF cell-compatible materials by photo-polymerizing the reactive precursors in a mold. Insertion of the multifunctional implant in the disc of a cadaveric canine spine showed that these shape-memory devices could be

  15. Multi-shape active composites by 3D printing of digital shape memory polymers.

    PubMed

    Wu, Jiangtao; Yuan, Chao; Ding, Zhen; Isakov, Michael; Mao, Yiqi; Wang, Tiejun; Dunn, Martin L; Qi, H Jerry

    2016-04-13

    Recent research using 3D printing to create active structures has added an exciting new dimension to 3D printing technology. After being printed, these active, often composite, materials can change their shape over time; this has been termed as 4D printing. In this paper, we demonstrate the design and manufacture of active composites that can take multiple shapes, depending on the environmental temperature. This is achieved by 3D printing layered composite structures with multiple families of shape memory polymer (SMP) fibers - digital SMPs - with different glass transition temperatures (Tg) to control the transformation of the structure. After a simple single-step thermomechanical programming process, the fiber families can be sequentially activated to bend when the temperature is increased. By tuning the volume fraction of the fibers, bending deformation can be controlled. We develop a theoretical model to predict the deformation behavior for better understanding the phenomena and aiding the design. We also design and print several flat 2D structures that can be programmed to fold and open themselves when subjected to heat. With the advantages of an easy fabrication process and the controllable multi-shape memory effect, the printed SMP composites have a great potential in 4D printing applications.

  16. Temperature dependent evolution of wrinkled single-crystal silicon ribbons on shape memory polymers.

    PubMed

    Wang, Yu; Yu, Kai; Qi, H Jerry; Xiao, Jianliang

    2017-10-06

    Shape memory polymers (SMPs) can remember two or more distinct shapes, and thus can have a lot of potential applications. This paper presents combined experimental and theoretical studies on the wrinkling of single-crystal Si ribbons on SMPs and the temperature dependent evolution. Using the shape memory effect of heat responsive SMPs, this study provides a method to build wavy forms of single-crystal silicon thin films on top of SMP substrates. Silicon ribbons obtained from a Si-on-insulator (SOI) wafer are released and transferred onto the surface of programmed SMPs. Then such bilayer systems are recovered at different temperatures, yielding well-defined, wavy profiles of Si ribbons. The wavy profiles are shown to evolve with time, and the evolution behavior strongly depends on the recovery temperature. At relatively low recovery temperatures, both wrinkle wavelength and amplitude increase with time as evolution progresses. Finite element analysis (FEA) accounting for the thermomechanical behavior of SMPs is conducted to study the wrinkling of Si ribbons on SMPs, which shows good agreement with experiment. Merging of wrinkles is observed in FEA, which could explain the increase of wrinkle wavelength observed in the experiment. This study can have important implications for smart stretchable electronics, wrinkling mechanics, stimuli-responsive surface engineering, and advanced manufacturing.

  17. Thermo-mechanical and micro-structural characterization of shape memory polymer foams

    NASA Astrophysics Data System (ADS)

    di Prima, Matthew Allen

    The need for a set of design criteria, models, and limits for the use of shape memory polymer foams was proposed. The effect of temperature and strain on the mechanical behavior; compression, tensile, cyclic compression, constrained recovery, and free strain recovery of the material was used to determine the operational limits of the material. Next, the damage mechanism and viscoelastic effects in compressive cycling were determined through further mechanical testing and with the incorporation of three dimensional structure mapping via micro-CT scanning. The influence of microstructure was determined by testing the basic thermomechanical, viscoelactic, and shape recovery behavior of foams with relative densities of 20, 30, and 40 percent. A similar suite of tests were then performed with the base epoxy material to generate the material properties for computational modeling. This data was then combined with three dimensional microstructures generated from micro-CT scans to develop material models for shape memory foams. These models were then validated by comparing model results to the experimental results under similar conditions.

  18. Multi-shape active composites by 3D printing of digital shape memory polymers

    PubMed Central

    Wu, Jiangtao; Yuan, Chao; Ding, Zhen; Isakov, Michael; Mao, Yiqi; Wang, Tiejun; Dunn, Martin L.; Qi, H. Jerry

    2016-01-01

    Recent research using 3D printing to create active structures has added an exciting new dimension to 3D printing technology. After being printed, these active, often composite, materials can change their shape over time; this has been termed as 4D printing. In this paper, we demonstrate the design and manufacture of active composites that can take multiple shapes, depending on the environmental temperature. This is achieved by 3D printing layered composite structures with multiple families of shape memory polymer (SMP) fibers – digital SMPs - with different glass transition temperatures (Tg) to control the transformation of the structure. After a simple single-step thermomechanical programming process, the fiber families can be sequentially activated to bend when the temperature is increased. By tuning the volume fraction of the fibers, bending deformation can be controlled. We develop a theoretical model to predict the deformation behavior for better understanding the phenomena and aiding the design. We also design and print several flat 2D structures that can be programmed to fold and open themselves when subjected to heat. With the advantages of an easy fabrication process and the controllable multi-shape memory effect, the printed SMP composites have a great potential in 4D printing applications. PMID:27071543

  19. Multi-shape active composites by 3D printing of digital shape memory polymers

    NASA Astrophysics Data System (ADS)

    Wu, Jiangtao; Yuan, Chao; Ding, Zhen; Isakov, Michael; Mao, Yiqi; Wang, Tiejun; Dunn, Martin L.; Qi, H. Jerry

    2016-04-01

    Recent research using 3D printing to create active structures has added an exciting new dimension to 3D printing technology. After being printed, these active, often composite, materials can change their shape over time; this has been termed as 4D printing. In this paper, we demonstrate the design and manufacture of active composites that can take multiple shapes, depending on the environmental temperature. This is achieved by 3D printing layered composite structures with multiple families of shape memory polymer (SMP) fibers – digital SMPs - with different glass transition temperatures (Tg) to control the transformation of the structure. After a simple single-step thermomechanical programming process, the fiber families can be sequentially activated to bend when the temperature is increased. By tuning the volume fraction of the fibers, bending deformation can be controlled. We develop a theoretical model to predict the deformation behavior for better understanding the phenomena and aiding the design. We also design and print several flat 2D structures that can be programmed to fold and open themselves when subjected to heat. With the advantages of an easy fabrication process and the controllable multi-shape memory effect, the printed SMP composites have a great potential in 4D printing applications.

  20. Effects of sensitizer length on radiation crosslinked shape-memory polymers

    NASA Astrophysics Data System (ADS)

    Ware, Taylor; Voit, Walter; Gall, Ken

    2010-04-01

    Shape-memory polymers (SMPs) are smart materials that can be designed to retain a metastable state and upon activation, recover a preprogrammed shape. In this study, poly(methyl acrylate) (PMA) is blended with poly(ethylene glycol) diacrylate (PEGDA) of various molecular weights in various concentrations and subsequently exposed to ionizing radiation. PEGDA sensitizes the radiation crosslinking of PMA, lowering the minimum absorbed dose for gelation and increasing the rubbery modulus, after crosslinking. Minimum dose for gelation, as determined by the Charlesby-Pinner equation, decreases from 25.57 kGy for unblended PMA to 2.06 kGy for PMA blended with 10.00 mole% PEGDA. Moreover, increase in the blend concentration of PEGDA increases the crosslinking density of the resulting networks. Sensitizer length, namely Mn of PEGDA, also affects crosslinking and final mechanical properties. Increase in the length of the PEGDA molecule at a constant molar ratio increases the efficacy of the molecule as a radiation sensitizer as determined by the increase in gel fraction and rubbery modulus across doses. However, at a constant weight ratio of PEGDA to PMA, shorter PEGDA chains sensitize more crosslinking because they have more reactive ends per weight fraction. Sensitized samples of PMA with PEGDA were tested for shape-memory properties and showed shape fixity of greater than 99%. Samples had a glass transition temperature near 28 °C and recovered between 97% and 99% of the induced strain when strained to 50%.

  1. Multiple Shape Memory Polymers Based on Laminates Formed from Thiol-Click Chemistry Based Polymerizations

    PubMed Central

    Podgórski, M.; Wang, C.

    2015-01-01

    This investigation details the formation of polymer network trilayer laminates formed by thiol-X click chemistries, and their subsequent implementation and evaluation for quadruple shape memory behavior. Thiol-Michael addition and thiol-isocyanate-based crosslinking reactions were employed to fabricate each of the laminate’s layers with independent control of the chemistry and properties of each layer and outstanding interlayer adhesion and stability. The characteristic features of step-growth thiol-X reactions, such as excellent network uniformity and narrow thermal transitions as well as their stoichiometric nature, enabled fabrication of trilayer laminates with three distinctly different glass transition temperatures grouped within a narrow range of 100 °C. Through variations in the layer thicknesses, a step-wise modulus drop as a function of temperature was achieved. This behavior allowed multi-step programming and the demonstration and quantification of quadruple shape memory performance. As is critical for this performance, the interface connecting the layers was evaluated in stoichiometric as well as off-stoichiometric systems. It was shown that the laminated structures exhibit strong interfacial binding and hardly suffer any delamination during cyclic material testing and deformation. PMID:26234205

  2. Multivalent Polymer Nanocomplex Targeting Endosomal Receptor of Immune Cells for Enhanced Antitumor and Systemic Memory Response.

    PubMed

    Kim, Sun-Young; Heo, Min Beom; Hwang, Geum-Sook; Jung, Youngae; Choi, Do Yeol; Park, Yeong-Min; Lim, Yong Taik

    2015-07-06

    We have designed and synthesized linear polymer-based nanoconjugates and nanocomplexes bearing multivalent immunostimulatory ligands and also demonstrated that the synthetic multivalent nanocomplexes led to an enhanced stimulation of immune cells in vitro and antitumor and systemic immune memory response in vivo. We have developed hyaluronic acid (HA)-based multivalent nanoconjugates and nanocomplexes for enhanced immunostimulation through the combination of multivalent immune adjuvants with CpG ODNs (as a TLR9 ligand) and cationic poly(L-lysine) (PLL; for the enhancement of cellular uptake). The multivalent HA-CpG nanoconjugate efficiently stimulated the antigen-presenting cells and the multivalent PLL/HA-CpG nanocomplex also led to an enhanced cellular uptake as well as continuous stimulation of endosomal TLR9. The mice vaccinated with dendritic cells treated with the multivalent nanocomplex exhibited tumor growth inhibition as well as a strong antitumor memory response. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Investigation of thermomechanical couplings, strain localization and shape memory properties in a shape memory polymer subjected to loading at various strain rates

    NASA Astrophysics Data System (ADS)

    Pieczyska, E. A.; Staszczak, M.; Maj, M.; Kowalczyk-Gajewska, K.; Golasiński, K.; Cristea, M.; Tobushi, H.; Hayashi, S.

    2016-08-01

    This paper presents experimental and modeling results of the effects of thermomechanical couplings occurring in a polyurethane shape memory polymer (SMP) subjected to tension at various strain rates within large strains. The SMP mechanical curves, recorded using a testing machine, and the related temperature changes, measured in a contactless manner using an IR camera, were used to investigate the polymer deformation process at various loading stages. The effects of thermomechanical couplings allowed the determination of the material yield point in the initial loading stage, the investigation of nucleation and development of the strain localization at larger strains and the estimation of the effects of thermoelastic behavior during the unloading process. The obtained stress-strain and thermal characteristics, the results of the dynamic mechanical analysis and estimated values of the shape fixity and shape recovery parameters confirmed that the shape memory polymer (T g = 45 °C) is characterized by good mechanical and shape memory properties, as well as high sensitivity to the strain rate. The mechanical response of the SMP subjected to tension was simulated using the finite element method and applying the large strain, two-phase model. Strain localization observed in the experiment was well reproduced in simulations and the temperature spots were correlated with the accumulated viscoplastic deformation of the SMP glassy phase.

  4. One-year clinical outcome of amphilimus polymer-free drug-eluting stent in diabetes mellitus patients: Insight from the ASTUTE registry (AmphilimuS iTalian mUlticenTre rEgistry).

    PubMed

    Colombo, Antonio; Godino, Cosmo; Donahue, Michael; Testa, Luca; Chiarito, Mauro; Pavon, Anna Giulia; Colantonio, Riccardo; Cappelletti, Alberto; Monello, Alberto; Magni, Valeria; Milazzo, Diego; Parisi, Rosario; Nicolino, Annamaria; Moshiri, Shahram; Fattori, Rossella; Aprigliano, Gianfranco; Palloshi, Altin; Caramanno, Giuseppe; Montorfano, Matteo; Bedogni, Francesco; Margonato, Alberto; Briguori, Carlo

    2016-07-01

    Despite several improvements in drug-eluting stent (DES) technology, patients with diabetes mellitus (DM) are affected by higher rate of adverse events after PCI with DES, mainly in terms of target lesion revascularization (TLR). The Cre8 stent, a polymer-free amphilimus-eluting stent (AES), has shown promising preliminary results in DM patients. The ASTUTE registry was conceived to assess clinical performance of this polymer-free AES in DM in a "real-world" multicenter-independent cohort of patients. 1216 consecutive patients (1637 lesions) treated with Cre8 between August 2011 and January 2015 were retrospectively enrolled and divided in two groups: DM and non-DM patients. The primary and secondary endpoints were target lesion failure (TLF) and TLR at 1-year, respectively. 1-Year clinical outcome was available for 407 (80%) DM and 566 (84%) non-DM patients. Diabetic patients were more frequently affected by hypertension (p<0.001) and dyslipidemia (p<0.001) and more frequently dialyzed (p=0.010). At 1-year, TLF occurred in 50 (5.1%) overall patients, and was similar in DM and non-DM patients (4.9 vs 5.3%, respectively, p=0.788). The secondary endpoint (TLR) occurred in 3% of overall patients and similarly in DM and non-DM patients (3.7 vs 2.5%, respectively, p=0.273). Primary and secondary endpoints were similar also between insulin and non-insulin dependent DM patients. The results of this large, real-world, multicenter-independent registry show that Cre8 AES has similar safety and efficacy profile in DM as well as non-DM patients, reducing the adverse outcomes related to DM in patients undergoing PCI. A large randomized trial will be necessary to definitely prove these preliminary findings. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  5. Shape-Memory Hydrogels: Evolution of Structural Principles To Enable Shape Switching of Hydrophilic Polymer Networks.

    PubMed

    Löwenberg, Candy; Balk, Maria; Wischke, Christian; Behl, Marc; Lendlein, Andreas

    2017-02-15

    The ability of hydrophilic chain segments in polymer networks to strongly interact with water allows the volumetric expansion of the material and formation of a hydrogel. When polymer chain segments undergo reversible hydration depending on environmental conditions, smart hydrogels can be realized, which are able to shrink/swell and thus alter their volume on demand. In contrast, implementing the capacity of hydrogels to switch their shape rather than volume demands more sophisticated chemical approaches and structural concepts. In this Account, the principles of hydrogel network design, incorporation of molecular switches, and hydrogel microstructures are summarized that enable a spatially directed actuation of hydrogels by a shape-memory effect (SME) without major volume alteration. The SME involves an elastic deformation (programming) of samples, which are temporarily fixed by reversible covalent or physical cross-links resulting in a temporary shape. The material can reverse to the original shape when these molecular switches are affected by application of a suitable stimulus. Hydrophobic shape-memory polymers (SMPs), which are established with complex functions including multiple or reversible shape-switching, may provide inspiration for the molecular architecture of shape-memory hydrogels (SMHs), but cannot be identically copied in the world of hydrophilic soft materials. For instance, fixation of the temporary shape requires cross-links to be formed also in an aqueous environment, which may not be realized, for example, by crystalline domains from the hydrophilic main chains as these may dissolve in presence of water. Accordingly, dual-shape hydrogels have evolved, where, for example, hydrophobic crystallizable side chains have been linked into hydrophilic polymer networks to act as temperature-sensitive temporary cross-links. By incorporating a second type of such side chains, triple-shape hydrogels can be realized. Considering the typically given light

  6. Safety and Efficacy of New Sirolimus-eluting Stent Models in a Preclinical Study.

    PubMed

    Estévez-Loureiro, Rodrigo; Pérez de Prado, Armando; Pérez-Martínez, Claudia; Cuellas-Ramón, Carlos; Regueiro-Purriños, Marta; Gonzalo-Orden, José M; López-Benito, María; Molina-Crisol, María; Duocastella-Codina, Luis; Fernández-Vázquez, Felipe

    2015-12-01

    Initial preclinical studies are required during the process of improving polymers, platforms, and drug-eluting systems for new coronary stent designs. Our objective was to analyze the efficacy and safety of new drug-eluting stent models compared with a conventional stent and commercialized drug-eluting stents in an experimental model with healthy porcine coronary arteries. Sixty stents (conventional stent, new sirolimus-eluting stents: drug-eluting stents 1, 2 and 3; Cypher(®) and Xience(®)) were randomly placed in the coronary arteries of 20 Large White domestic pigs. Angiographic and histomorphometric studies were done 28 days later. The stents were implanted at a stent/artery ratio of 1.34±0.15, with no significant differences between groups. The new stents showed less late loss and angiographic restenosis than conventional stents (P=.006 and P<.001, respectively). Histologically, restenosis and neointimal area were lower with all the new platforms than with the conventional stents (P<.001 for each variable), and no differences were found vs the drug-eluting stents on the market. Safety data showed that endothelialization was lower with drug-eluting stents than with conventional stents, except for drug-eluting stent 3 (P=.084). Likewise, inflammation was lower with drug-eluting stent 3 than with other stents. The new drug-eluting stent platforms studied are associated with less restenosis than conventional stents and showed no significant differences in safety or efficacy vs commercialized drug-eluting stents. Copyright © 2015 Sociedad Española de Cardiología. Published by Elsevier España, S.L.U. All rights reserved.

  7. Angioplasty and Vascular Stenting

    MedlinePlus

    ... Drug-coated (also called drug-eluting) stents have recently been approved for clinical use by the U.S. ... you notify the MRI department that you have recently had a stent. Although stents used today may ...

  8. Shape-memory polymer nanocomposites with a 3D conductive network for bidirectional actuation and locomotion application.

    PubMed

    Peng, Qingyu; Wei, Hongqiu; Qin, Yuyang; Lin, Zaishan; Zhao, Xu; Xu, Fan; Leng, Jinsong; He, Xiaodong; Cao, Anyuan; Li, Yibin

    2016-10-27

    Electrical stimulation of shape-memory polymers (SMPs) has many advantages over thermal methods; creating an efficient conductive path through the bulk polymers is essential for developing high performance electroactive systems. Here, we show that a three-dimensional (3D) porous carbon nanotube sponge can serve as a built-in integral conductive network to provide internal, homogeneous, in situ Joule heating for shape-memory polymers, thus significantly improving the mechanical and thermal behavior of SMPs. As a result, the 3D nanocomposites show a fast response and produce large exerting forces (with a maximum flexural stress of 14.6 MPa) during shape recovery. We further studied the construction of a double-layer composite structure for bidirectional actuation, in which the shape change is dominated by the temperature-dependent exerting force from the top and bottom layer, alternately. An inchworm-type robot is demonstrated whose locomotion is realized by such bidirectional shape memory. Our large stroke shape-memory nanocomposites have promising applications in many areas including artificial muscles and bionic robots.

  9. An approach to predict the shape-memory behavior of amorphous polymers from Dynamic Mechanical Analysis (DMA) data

    NASA Astrophysics Data System (ADS)

    Kuki, Ákos; Czifrák, Katalin; Karger-Kocsis, József; Zsuga, Miklós; Kéki, Sándor

    2015-02-01

    The prediction of shape-memory behavior is essential regarding the design of a smart material for different applications. This paper proposes a simple and quick method for the prediction of shape-memory behavior of amorphous shape memory polymers (SMPs) on the basis of a single dynamic mechanical analysis (DMA) temperature sweep at constant frequency. All the parameters of the constitutive equations for linear viscoelasticity are obtained by fitting the DMA curves. The change with the temperature of the time-temperature superposition shift factor ( a T ) is expressed by the Williams-Landel-Ferry (WLF) model near and above the glass transition temperature ( T g ), and by the Arrhenius law below T g . The constants of the WLF and Arrhenius equations can also be determined. The results of our calculations agree satisfactorily with the experimental free recovery curves from shape-memory tests.

  10. Inorganic-organic shape memory polymers and foams for bone defect repairs

    NASA Astrophysics Data System (ADS)

    Zhang, Dawei

    The ultimate goal of this research was to develop a "self-fitting" shape memory polymer (SMP) scaffold for the repair of craniomaxillofacial (CMF) bone defects. CMF defects may be caused by trauma, tumor removal or congenital abnormalities and represent a major class of bone defects. Their repair with autografts is limited by availability, donor site morbidity and complex surgical procedures. In addition, shaping and positioning of these rigid grafts into irregular defects is difficult. Herein, we have developed SMP scaffolds which soften at T > ˜56 °C, allowing them to conformally fit into a bone defect. Upon cooling to body temperature, the scaffold becomes rigid and mechanically locks in place. This research was comprised of four major studies. In the first study, photocrosslinkable acrylated (AcO) SMP macromers containing a poly(epsilon-caprolactone) (PCL) segment and polydimethylsiloxane (PDMS) segments were synthesized with the general formula: AcO-PCL40-block-PDMS m-block-PCL40-OAc. By varying the PDMS segment length (m), solid SMPs with highly tunable mechanical properties and excellent shape memory abilities were prepared. In the second study, porous SMP scaffolds were fabricated based on AcO-PCL 40-block-PDMS37-block-PCL 40-OAc via a revised solvent casting particulate leaching (SCPL) method. By tailoring scaffold parameters including salt fusion, macromer concentration and salt size, scaffold properties (e.g. pore features, compressive modulus and shape memory behavior) were tuned. In the third study, porous SMP scaffolds were produced from macromers with variable PDMS segment lengths (m = 0 -- 130) via an optimized SCPL method. The impact on pore features, thermal, mechanical, and shape memory properties as well as degradation rates were investigated. In the final study, a bioactive polydopamine coating was applied onto pore surfaces of the SMP scaffold prepared from PCL diacrylate. The thin coating did not affect intrinsic bulk properties of the

  11. Symptomatic stent cast.

    PubMed

    Keohane, John; Moore, Michael; O'Mahony, Seamus; Crosbie, Orla

    2008-02-01

    Biliary stent occlusion is a major complication of endoscopic stent insertion and results in repeat procedures. Various theories as to the etiology have been proposed, the most frequently studied is the attachment of gram negative bacteria within the stent. Several studies have shown prolongation of stent patency with antibiotic prophylaxis. We report the case of stent occlusion from a cast of a previously inserted straight biliary stent; a "stent cast" in an 86-year-old woman with obstructive jaundice. This was retrieved with the lithotrypter and she made an uneventful recovery. This is the first reported case of a biliary stent cast.

  12. Are bio-absorbable stents the future of SFA treatment?

    PubMed

    Peeters, P; Keirse, K; Verbist, J; Deloose, K; Bosiers, M

    2010-02-01

    Several limitations inherent to the implantation of a metallic device, such as the occurrence of in-stent re-stenosis, in an arterial lumen intuitively explain the interest for developing bio-absorbable stents. Two main types of bio-absorbable stents currently exist: polymer stents and metallic stents. To date, no studies with bio-absorbable stents have been conducted in the superficial femoral artery (SFA). Because of their strut thickness and lack of radial force, polymer stents are no good candidates for endovascular use. Absorbable metal stents (AMS) do have the potential to perform well for artery treatment, although current evidence from in-human coronary and infrapopliteal studies yield unsatisfactory results. Drastic technological improvements are mandatory before AMS can be considered for every day practice. Yet, it is our belief that further development of other metal and non-metal bio-absorbable stents, with or without drug-coating, may lead to the creation of the ultimate SFA stent.

  13. Comparative assessment of three drug eluting stents with different platforms but with the same biodegradable polymer and the drug based on quantitative coronary angiography and optical coherence tomography at 12-month follow-up.

    PubMed

    Gil, Robert J; Bil, Jacek; Legutko, Jacek; Pawłowski, Tomasz; Gil, Katarzyna E; Dudek, Dariusz; Costa, Ricardo A

    2017-09-30

    The aim of this study was to compare neointima proliferation in three drug-eluting stents (DES) produced by the same company (Balton, Poland) which are covered with a biodegradable polymer and elute sirolimus (concentration: 1.0 and 1.2 µg/mm(2)), but have different stent platforms and strut thickness: stainless steel Prolim(®) (115 µm) and BiOSS LIM(®) (120 µm) and cobalt-chromium Alex(®) (70 µm). We analyzed data of patients with quantitative coronary angiography (QCA) and optical coherence tomography (OCT) at 12 months from BiOSS LIM Registry, Prolim Registry and Alex OCT clinical trial. There were 56 patients enrolled, in whom 29 Prolim(®) stents were deployed, in 11-BiOSS LIM(®) and in 16-Alex stents. The late lumen loss was the smallest in Prolim(®) subgroup (0.26 ± 0.17 mm) and did not differ from Alex(®) subgroup (0.28 ± 0.47 mm). This parameter was significantly bigger in BiOSS(®) subgroup (0.38 ± 0.19 mm; p < 0.05). In OCT analysis there was no statistically significant difference between Prolim(®) and Alex(®) subgroups in terms of mean neointima burden (24.6 ± 8.6 vs. 19.27 ± 8.11%) and neointima volume (28.16 ± 15.10 vs. 24.51 ± 17.64 mm(3)). In BiOSS(®) group mean neointima burden (30.9 ± 6.2%) and mean neointima volume (44.9 ± 4.9 mm(3)) were significantly larger. The morphological analysis revealed that in most cases in all groups the neointima was homogenous with plaque presence only around stent struts. In the QCA and OCT analysis regular DES (Prolim(®) and Alex(®)) obtained similar results, whereas more pronounced response from the vessel wall was found in the BiOSS(®) subgroup.

  14. Memory effect in the chain-collapse process in a dilute polymer solution

    NASA Astrophysics Data System (ADS)

    Maki, Yasuyuki; Sasaki, Naoki; Nakata, Mitsuo

    2004-12-01

    The effect of temperature perturbation on a single-chain-collapse process was studied for poly(methyl methacrylate) with the molecular weight Mw=1.05×107 in the mixed solvent of tert-butyl alcohol+water (2.5 vol %). In the chain-collapse process after a quench from the θ temperature to a temperature T1, the temperature was changed from T1 to T2 at the time t1 after the quench and returned to T1 at the time t1+t2. In the three stages at T1, T2, and T1, measurements of the mean-square radius of gyration of polymer chains were carried out by static light scattering and the chain-collapse process was represented by the expansion factor as a function of time. An effect of chain aggregation on the measurements was negligibly small because of the very slow phase separation. For the negative temperature perturbation (T1>T2), the chain-collapse processes observed in the first and third stages were connected smoothly and agreed with the collapse process due to a single-stage quench to T1. A memory of the chain collapse in the first stage at T1 was found to persist into the third stage at the same temperature T1 without being affected by the temperature perturbation of T2 during t2. The memory effect was observed irrespective of the time period of t2. The positive temperature perturbation (T1

  15. Strong electroactive biodegradable shape memory polymer networks based on star-shaped polylactide and aniline trimer for bone tissue engineering.

    PubMed

    Xie, Meihua; Wang, Ling; Ge, Juan; Guo, Baolin; Ma, Peter X

    2015-04-01

    Preparation of functional shape memory polymer (SMP) for tissue engineering remains a challenge. Here the synthesis of strong electroactive shape memory polymer (ESMP) networks based on star-shaped polylactide (PLA) and aniline trimer (AT) is reported. Six-armed PLAs with various chain lengths were chemically cross-linked to synthesize SMP. After addition of an electroactive AT segment into the SMP, ESMP was obtained. The polymers were characterized by (1)H NMR, GPC, FT-IR, CV, DSC, DMA, tensile test, and degradation test. The SMP and ESMP exhibited strong mechanical properties (modulus higher than GPa) and excellent shape memory performance: short recovery time (several seconds), high recovery ratio (over 94%), and high fixity ratio (almost 100%). Moreover, cyclic voltammetry test confirmed the electroactivity of the ESMP. The ESMP significantly enhanced the proliferation of C2C12 cells compared to SMP and linear PLA (control). In addition, the ESMP greatly improved the osteogenic differentiation of C2C12 myoblast cells compared to PH10 and PLA in terms of ALP enzyme activity, immunofluorescence staining, and relative gene expression by quantitative real-time polymerase chain reaction (qRT-PCR). These intelligent SMPs and electroactive SMP with strong mechanical properties, tunable degradability, good electroactivity, biocompatibility, and enhanced osteogenic differentiation of C2C12 cells show great potential for bone regeneration.

  16. Epitaxial Growth of Thin Ferroelectric Polymer Films on Graphene Layer for Fully Transparent and Flexible Nonvolatile Memory.

    PubMed

    Kim, Kang Lib; Lee, Wonho; Hwang, Sun Kak; Joo, Se Hun; Cho, Suk Man; Song, Giyoung; Cho, Sung Hwan; Jeong, Beomjin; Hwang, Ihn; Ahn, Jong-Hyun; Yu, Young-Jun; Shin, Tae Joo; Kwak, Sang Kyu; Kang, Seok Ju; Park, Cheolmin

    2016-01-13

    Enhancing the device performance of organic memory devices while providing high optical transparency and mechanical flexibility requires an optimized combination of functional materials and smart device architecture design. However, it remains a great challenge to realize fully functional transparent and mechanically durable nonvolatile memory because of the limitations of conventional rigid, opaque metal electrodes. Here, we demonstrate ferroelectric nonvolatile memory devices that use graphene electrodes as the epitaxial growth substrate for crystalline poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) polymer. The strong crystallographic interaction between PVDF-TrFE and graphene results in the orientation of the crystals with distinct symmetry, which is favorable for polarization switching upon the electric field. The epitaxial growth of PVDF-TrFE on a graphene layer thus provides excellent ferroelectric performance with high remnant polarization in metal/ferroelectric polymer/metal devices. Furthermore, a fully transparent and flexible array of ferroelectric field effect transistors was successfully realized by adopting transparent poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] semiconducting polymer.

  17. Advantages and disadvantages of biodegradable platforms in drug eluting stents

    PubMed Central

    Rodriguez-Granillo, Agustina; Rubilar, Bibiana; Rodriguez-Granillo, Gaston; Rodriguez, Alfredo E

    2011-01-01

    Coronary angioplasty with drug-eluting stent (DES) implantation is currently the most common stent procedure worldwide. Since the introduction of DES, coronary restenosis as well as the incidence of target vessel and target lesion revascularization have been significantly reduced. However, the incidence of very late stent thrombosis beyond the first year after stent deployment has more commonly been linked to DES than to bare-metal stent (BMS) implantation. Several factors have been associated with very late stent thrombosis after DES implantation, such as delayed healing, inflammation, stent mal-apposition and endothelial dysfunction. Some of these adverse events were associated with the presence of durable polymers, which were essential to allow the elution of the immunosuppressive drug in the first DES designs. The introduction of erodable polymers in DES technology has provided the potential to complete the degradation of the polymer simultaneously or immediately after the release of the immunosuppressive drug, after which a BMS remains in place. Several DES designs with biodegradable (BIO) polymers have been introduced in preclinical and clinical studies, including randomized trials. In this review, we analyze the clinical results from 6 observational and randomized studies with BIO polymers and discuss advantages and disadvantages of this new technology. PMID:21499496

  18. Stent Coating Integrity of Durable and Biodegradable Coated Drug Eluting Stents.

    PubMed

    Yazdani, Saami K; Sheehy, Alexander; Pacetti, Stephen; Rittlemeyer, Brandon; Kolodgie, Frank D; Virmani, Renu

    2016-10-01

    Coatings consisting of a polymer and drug are widely used in drug-eluting stents (DES) and are essential in providing programmable drug release kinetics. Among other factors, stent coating technologies can influence blood compatibility, affect acute and sub-acute healing, and potentially trigger a chronic inflammatory response. The aim of this study was to investigate the short-term (7 and 28 days) and long-term (90 and 180 days) coating integrity of the Xience Prime Everolimus-Eluting Stent (EES), Resolute Zotarolimus-Eluting Stent (ZES), Taxus Paclitaxel-Eluting Stent (PES), and Nobori Biolimus A9-Eluting Stent (BES) in a rabbit ilio-femoral stent model. Stented arteries (n = 48) were harvested and the tissue surrounding the implanted stents digested away with an enzymatic solution. Results demonstrated that the majority of struts of EES were without any coating defects with a few struts showing minor defects. Similarly, for the ZES, most of the struts were without coating defects at all time points except at 180 days. The majority of PES demonstrated mostly webbing and uneven coating. In the BES group, the majority of strut coating showed polymer cracking. Overall, the EES and ZES had fewer coating defects than the PES and BES. Coating defects, however increase over time for the ZES, whereas the percent of coating irregularities remained constant for the EES. These results provide, for the first time, a comparison of the long-term durability of these drug-eluting stent coatings in vivo. © 2016, Wiley Periodicals, Inc.

  19. High Performance Transparent Transistor Memory Devices Using Nano-Floating Gate of Polymer/ZnO Nanocomposites

    PubMed Central

    Shih, Chien-Chung; Lee, Wen-Ya; Chiu, Yu-Cheng; Hsu, Han-Wen; Chang, Hsuan-Chun; Liu, Cheng-Liang; Chen, Wen-Chang

    2016-01-01

    Nano-floating gate memory devices (NFGM) using metal nanoparticles (NPs) covered with an insulating polymer have been considered as a promising electronic device for the next-generation nonvolatile organic memory applications NPs. However, the transparency of the device with metal NPs is restricted to 60~70% due to the light absorption in the visible region caused by the surface plasmon resonance effects of metal NPs. To address this issue, we demonstrate a novel NFGM using the blends of hole-trapping poly (9-(4-vinylphenyl) carbazole) (PVPK) and electron-trapping ZnO NPs as the charge storage element. The memory devices exhibited a remarkably programmable memory window up to 60 V during the program/erase operations, which was attributed to the trapping/detrapping of charge carriers in ZnO NPs/PVPK composite. Furthermore, the devices showed the long-term retention time (>105 s) and WRER test (>200 cycles), indicating excellent electrical reliability and stability. Additionally, the fabricated transistor memory devices exhibited a relatively high transparency of 90% at the wavelength of 500 nm based on the spray-coated PEDOT:PSS as electrode, suggesting high potential for transparent organic electronic memory devices. PMID:26831222

  20. Thermomechanical properties of polyurethane shape memory polymer-experiment and modelling

    NASA Astrophysics Data System (ADS)

    Pieczyska, E. A.; Maj, M.; Kowalczyk-Gajewska, K.; Staszczak, M.; Gradys, A.; Majewski, M.; Cristea, M.; Tobushi, H.; Hayashi, S.

    2015-04-01

    In this paper extensive research on the polyurethane shape memory polymer (PU-SMP) is reported, including its structure analysis, our experimental investigation of its thermomechanical properties and its modelling. The influence of the effects of thermomechanical couplings on the SMP behaviour during tension at room temperature is studied using a fast and sensitive infrared camera. It is shown that the thermomechanical behaviour of the SMP significantly depends on the strain rate: at a higher strain rate higher stress and temperature values are obtained. This indicates that an increase of the strain rate leads to activation of different deformation mechanisms at the micro-scale, along with reorientation and alignment of the molecular chains. Furthermore, influence of temperature on the SMP’s mechanical behaviour is studied. It is observed during the loading in a thermal chamber that at the temperature 20 °C below the glass transition temperature (Tg) the PU-SMP strengthens about six times compared to the material above Tg but does not exhibit the shape recovery. A finite-strain constitutive model is formulated, where the SMP is described as a two-phase material composed of a hyperelastic rubbery phase and elastic-viscoplastic glassy phase. The volume content of phases is governed by the current temperature. Finally, model predictions are compared with the experimental results.

  1. Characterizing and modeling the free recovery and constrained recovery behavior of a polyurethane shape memory polymer

    PubMed Central

    Volk, Brent L; Lagoudas, Dimitris C; Maitland, Duncan J

    2011-01-01

    In this work, tensile tests and one-dimensional constitutive modeling are performed on a high recovery force polyurethane shape memory polymer that is being considered for biomedical applications. The tensile tests investigate the free recovery (zero load) response as well as the constrained displacement recovery (stress recovery) response at extension values up to 25%, and two consecutive cycles are performed during each test. The material is observed to recover 100% of the applied deformation when heated at zero load in the second thermomechanical cycle, and a stress recovery of 1.5 MPa to 4.2 MPa is observed for the constrained displacement recovery experiments. After performing the experiments, the Chen and Lagoudas model is used to simulate and predict the experimental results. The material properties used in the constitutive model – namely the coefficients of thermal expansion, shear moduli, and frozen volume fraction – are calibrated from a single 10% extension free recovery experiment. The model is then used to predict the material response for the remaining free recovery and constrained displacement recovery experiments. The model predictions match well with the experimental data. PMID:22003272

  2. Opacification of Shape Memory Polymer Foam Designed for Treatment of Intracranial Aneurysms

    PubMed Central

    Rodriguez, Jennifer N.; Yu, Ya-Jen; Miller, Matthew W.; Wilson, Thomas S.; Hartman, Jonathan; Clubb, Fred J.; Gentry, Brandon; Maitland, Duncan J.

    2012-01-01

    Shape memory polymer (SMP) foam possesses structural and mechanical characteristics that make them very promising as an alternative treatment for intracranial aneurysms. Our SMP foams have low densities, with porosities as high as 98.8%; favorable for catheter delivery and aneurysm filling, but unfavorable for attenuating X-rays. This lack of contrast impedes the progression of this material becoming a viable medical device. This paper reports on increasing radioopacity by incorporating a high-Z element, tungsten particulate filler to attenuate X-rays, while conserving similar physical properties of the original non-opacified SMP foams. The minimal amount of tungsten for visibility was determined and subsequently incorporated into SMP foams, which were then fabricated into samples of increasing thicknesses. These samples were imaged through a pig’s skull to demonstrate radio-opacity in situ. Quantification of the increase in image contrast was performed via image processing methods and standard curves were made for varying concentrations of tungsten doped solid and foam SMP. 4% by volume loading of tungsten incorporated into our SMP foams has proven to be an effective method for improving radio-opacity of this material while maintaining the mechanical, physical and chemical properties of the original formulation. PMID:22101759

  3. In vitro performance of a shape memory polymer foam-coated coil embolization device.

    PubMed

    Boyle, Anthony J; Wierzbicki, Mark A; Herting, Scott; Weems, Andrew C; Nathan, Adam; Hwang, Wonjun; Maitland, Duncan J

    2017-07-31

    Intracranial saccular aneurysm treatment using endovascular embolization devices are limited by aneurysm recurrence that can lead to aneurysm rupture. A shape memory polymer (SMP) foam-coated coil (FCC) embolization device was designed to increase packing density and improve tissue healing compared to current commercial devices. FCC devices were fabricated and tested using in vitro models to assess feasibility for clinical treatment of intracranial saccular aneurysms. FCC devices demonstrated smooth delivery through tortuous pathways similar to control devices as well as greater than 10 min working time for clinical repositioning during deployment. Furthermore, the devices passed pilot verification tests for particulates, chemical leachables, and cytocompatibility. Finally, devices were successfully implanted in an in vitro saccular aneurysm model with large packing density. Though improvements and future studies evaluating device stiffness were identified as a necessity, the FCC device demonstrates effective delivery and packing performance that provides great promise for clinical application of the device in treatment of intracranial saccular aneurysms. Copyright © 2017 IPEM. Published by Elsevier Ltd. All rights reserved.

  4. Artificial muscles made of chiral two-way shape memory polymer fibers

    NASA Astrophysics Data System (ADS)

    Yang, Qianxi; Fan, Jizhou; Li, Guoqiang

    2016-10-01

    In this work, we demonstrate the unusual improvement of the tensile actuation of hierarchically chiral structured artificial muscle made of two-way shape memory polymer (2W-SMP) fiber. Experimental results show that the chemically cross-linked poly(ethylene-co-vinyl acetate) 2W-SMP fibers possess an average negative coefficient of thermal expansion (NCTE) that is at least one order higher than that of the polyethylene fiber used previously. As expected, the increase in axial thermal contraction of the precursor fiber leads to an increase in the recovered torque ( 4.4 Nmm ) of the chiral fiber and eventually in the tensile actuation of the twisted-then-coiled artificial muscle ( 67.81 ±1.82 % ). A mechanical model based on Castigliano's second theorem is proposed, and the calculated result is consistent with the experimental result (64.17% tensile stroke). The model proves the significance of the NCTE and the recovered torque on tensile actuation of the artificial muscle and can be used as a guidance for the future design.

  5. Shape memory polymers and their composites in aerospace applications: a review

    NASA Astrophysics Data System (ADS)

    Liu, Yanju; Du, Haiyang; Liu, Liwu; Leng, Jinsong

    2014-02-01

    As a new class of smart materials, shape memory polymers and their composites (SMPs and SMPCs) can respond to specific external stimulus and remember the original shape. There are many types of stimulus methods to actuate the deformation of SMPs and SMPCs, of which the thermal- and electro-responsive components and structures are common. In this review, the general mechanism of SMPs and SMPCs are first introduced, the stimulus methods are then discussed to demonstrate the shape recovery effect, and finally, the applications of SMPs and SMPCs that are reinforced with fiber materials in aerospace are reviewed. SMPC hinges and booms are discussed in the part on components; the booms can be divided again into foldable SMPC truss booms, coilable SMPC truss booms and storable tubular extendible member (STEM) booms. In terms of SMPC structures, the solar array and deployable panel, reflector antenna and morphing wing are introduced in detail. Considering the factors of weight, recovery force and shock effect, SMPCs are expected to have great potential applications in aerospace.

  6. Shape forming by thermal expansion mismatch and shape memory locking in polymer/elastomer laminates

    NASA Astrophysics Data System (ADS)

    Yuan, Chao; Ding, Zhen; Wang, T. J.; Dunn, Martin L.; Qi, H. Jerry

    2017-10-01

    This paper studies a novel method to fabricate three-dimensional (3D) structure from 2D thermo-responsive shape memory polymer (SMP)/elastomer bilayer laminate. In this method, the shape change is actuated by the thermal mismatch strain between the SMP and the elastomer layers upon heating. However, the glass transition behavior of the SMP locks the material into a new 3D shape that is stable even upon cooling. Therefore, the second shape becomes a new permanent shape of the laminate. A theoretical model that accounts for the temperature-dependent thermomechanical behavior of the SMP material and thermal mismatch strain between the two layers is developed to better understand the underlying physics. Model predictions and experiments show good agreement and indicate that the theoretical model can well predict the bending behavior of the bilayer laminate. The model is then used in the optimal design of geometrical configuration and material selection. The latter also illustrates the requirement of thermomechanical behaviors of the SMP to lock the shape. Based on the fundamental understandings, several self-folding structures are demonstrated by the bilayer laminate design.

  7. Facile 3D Metal Electrode Fabrication for Energy Applications via Inkjet Printing and Shape Memory Polymer

    NASA Astrophysics Data System (ADS)

    Roberts, R. C.; Wu, J.; Hau, N. Y.; Chang, Y. H.; Feng, S. P.; Li, D. C.

    2014-11-01

    This paper reports on a simple 3D metal electrode fabrication technique via inkjet printing onto a thermally contracting shape memory polymer (SMP) substrate. Inkjet printing allows for the direct patterning of structures from metal nanoparticle bearing liquid inks. After deposition, these inks require thermal curing steps to render a stable conductive film. By printing onto a SMP substrate, the metal nanoparticle ink can be cured and substrate shrunk simultaneously to create 3D metal microstructures, forming a large surface area topology well suited for energy applications. Polystyrene SMP shrinkage was characterized in a laboratory oven from 150-240°C, resulting in a size reduction of 1.97-2.58. Silver nanoparticle ink was patterned into electrodes, shrunk, and the topology characterized using scanning electron microscopy. Zinc-Silver Oxide microbatteries were fabricated to demonstrate the 3D electrodes compared to planar references. Characterization was performed using 10M potassium hydroxide electrolyte solution doped with zinc oxide (57g/L). After a 300s oxidation at 3Vdc, the 3D electrode battery demonstrated a 125% increased capacity over the reference cell. Reference cells degraded with longer oxidations, but the 3D electrodes were fully oxidized for 4 hours, and exhibited a capacity of 5.5mA-hr/cm2 with stable metal performance.

  8. A multi-branch finite deformation constitutive model for a shape memory polymer based syntactic foam

    NASA Astrophysics Data System (ADS)

    Gu, Jianping; Sun, Huiyu; Fang, Changqing

    2015-02-01

    A multi-branch thermoviscoelastic-themoviscoplastic finite deformation constitutive model incorporated with structural and stress relaxation is developed for a thermally activated shape memory polymer (SMP) based syntactic foam. In this paper, the total mechanical deformation of the foam is divided into the components of the SMP and the elastic glass microballoons by using the mixture rule. The nonlinear Adam-Gibbs model is used to describe the structural relaxation of the SMP as the temperature crosses the glass transition temperature (Tg). Further, a multi-branch model combined with the modified Eying model of viscous flow is used to capture the multitude of relaxation processes of the SMP. The deformation of the glass microballoons could be split into elastic and inelastic components. In addition, the phenomenological evolution rule is implemented in order to further characterize the macroscopic post-yield strain softening behaviors of the syntactic foam. A comparison between the numerical simulation and the thermomechanical experiment shows an acceptable agreement. Moreover, a parametric study is conducted to examine the predictability of the model and to provide guidance for reasonable design of the syntactic foam.

  9. The effect of moisture absorption on the physical properties of polyurethane shape memory polymer foams

    PubMed Central

    Yu, Ya-Jen; Hearon, Keith; Wilson, Thomas S.; Maitland, Duncan J.

    2011-01-01

    The effect of moisture absorption on the glass transition temperature (Tg) and stress/strain behavior of network polyurethane shape memory polymer (SMP) foams has been investigated. With our ultimate goal of engineering polyurethane SMP foams for use in blood contacting environments, we have investigated the effects of moisture exposure on the physical properties of polyurethane foams. To our best knowledge, this study is the first to investigate the effects of moisture absorption at varying humidity levels (non-immersion and immersion) on the physical properties of polyurethane SMP foams. The SMP foams were exposed to differing humidity levels for varying lengths of time, and they exhibited a maximum water uptake of 8.0% (by mass) after exposure to 100% relative humidity for 96 h. Differential scanning calorimetry results demonstrated that water absorption significantly decreased the Tg of the foam, with a maximum water uptake shifting the Tg from 67 °C to 5 °C. Samples that were immersed in water for 96 h and immediately subjected to tensile testing exhibited 100% increases in failure strains and 500% decreases in failure stresses; however, in all cases of time and humidity exposure, the plasticization effect was reversible upon placing moisture-saturated samples in 40% humidity environments for 24 h. PMID:21949469

  10. Electro-induced shape-memory polymer nanocomposite containing conductive particles and short fibers

    NASA Astrophysics Data System (ADS)

    Lv, Haibao; Leng, Jinsong; Du, Shanyi

    2008-03-01

    This present paper is focused on the effect of conductive particulate and fibrous fillers on the characterized property of styrene-based shape memory polymer incorporating carbon black (CB) and short carbon fiber (SCF). It was shown that the particulate additives are dispersed homogeneously within matrix and served as interconnections between the fibers, while the fibrous additives may be considered as a rigid long aggregate of carbon, leading to easy formation of continuous conductive networks. The glass transition temperature of nanocomposites drops sharply as compared with that of pure SMP from the differential scanning calorimetry (DSC). For the composite containing 5 wt% CB and 2 wt% SCF, the storage modulus increases by 16.2% compared to that of the composite containing 5 wt% CB and 1 wt% SCF; the peak of tangent delta curve is an alternative definition of T g, thus T g defined in such a way is determined as 69.44°C from Dynamic Mechanical Analyzer (DMA) test which is higher than 25.78°C obtained from DSC test. The electrical conductivity of the composite achieves 3 S/cm by four-point Van De Pauw method, and the shape recovery can be activated with a constant voltage of 25 V through them.

  11. Sensing and actuating capabilities of a shape memory polymer composite integrated with hybrid filler

    NASA Astrophysics Data System (ADS)

    Lu, Haibao; Yu, Kai; Liu, Yanju; Leng, Jinsong

    2010-06-01

    In this paper, hybrid fillers, including carbon black (CB) and chopped short carbon fibers (SCF), are integrated into a styrene-based shape memory polymer (SMP) with sensing and actuating capabilities. The hybrid filler is expected to transform insulating SMP into conducting. Static mechanical properties of the SMP composites containing various filler concentrations of hybrid filler reinforcement are studied first, and it is theoretically and experimentally confirmed that the mechanical properties are significantly improved by a factor of filler content of SCF. The excellent electrical properties of this novel type of SMP composite are determined by a four-point-probe method. As a consequence, the sensing properties of SMP composite filled with 5 wt% CB and 2 wt% SCF are characterized by functions of temperature and strain. These two experimental results both aid the use of SMP composites as sensors that respond to changes in temperature or mechanical loads. On the other hand, the actuating capability of SMP composites is also validated and demonstrated. The dynamic mechanical analysis result reveals that the output strength of SMP composites is improved with an increase in filler content of SCF. The actuating capability of SMP composites is subsequently demonstrated in a series of photographs.

  12. A simplified constitutive model for predicting shape memory polymers deformation behavior

    NASA Astrophysics Data System (ADS)

    Li, Yunxin; Guo, Siu-Siu; He, Yuhao; Liu, Zishun

    2015-12-01

    Shape memory polymers (SMPs) can keep a temporary shape after pre-deformation at a higher temperature and subsequent cooling. When they are reheated, their original shapes can be recovered. Such special characteristics of SMPs make them widely used in aerospace structures, biomedical devices, functional textiles and other devices. Increasing usefulness of SMPs motivates us to further understand their thermomechanical properties and deformation behavior, of which the development of appropriate constitutive models for SMPs is imperative. There is much work in literatures that address constitutive models of the thermo-mechanical coupling in SMPs. However, due to their complex forms, it is difficult to apply these constitutive models in the real world. In this paper, a three-element model with simple form is proposed to investigate the thermo-mechanical small strain (within 10%) behavior of polyurethane under uniaxial tension. Two different cases of heated recovery are considered: (1) unconstrained free strain recovery and (2) stress recovery under full constraint at a strain level fixed during low temperature unloading. To validate the model, simulated and predicted results are compared with Tobushi's experimental results and good agreement can be observed.

  13. Magnetic resonance flow velocity and temperature mapping of a shape memory polymer foam device

    PubMed Central

    2009-01-01

    Background Interventional medical devices based on thermally responsive shape memory polymer (SMP) are under development to treat stroke victims. The goals of these catheter-delivered devices include re-establishing blood flow in occluded arteries and preventing aneurysm rupture. Because these devices alter the hemodynamics and dissipate thermal energy during the therapeutic procedure, a first step in the device development process is to investigate fluid velocity and temperature changes following device deployment. Methods A laser-heated SMP foam device was deployed in a simplified in vitro vascular model. Magnetic resonance imaging (MRI) techniques were used to assess the fluid dynamics and thermal changes associated with device deployment. Results Spatial maps of the steady-state fluid velocity and temperature change inside and outside the laser-heated SMP foam device were acquired. Conclusions Though non-physiological conditions were used in this initial study, the utility of MRI in the development of a thermally-activated SMP foam device has been demonstrated. PMID:20043833

  14. Structural design of flexible Au electrode to enable shape memory polymer for electrical actuation

    NASA Astrophysics Data System (ADS)

    Lu, Haibao; Lei, Ming; Zhao, Chao; Xu, Ben; Leng, Jinsong; Fu, Y. Q.

    2015-04-01

    An effective resistive Joule heating approach was conducted to improve the electrical actuation and shape-recovery performance of a shape memory polymer (SMP) nanocomposite. Two types of gold (Au) film patterns were deposited to be used as electrodes to drive thermal-responsive SMPs and achieve a uniform temperature distribution during electro-activated shape recovery. Furthermore, the sensing capability of the Au electrode to both mechanical and thermal stimuli applied to the SMP nanocomposite was experimentally investigated and theoretically analyzed. It was found that the change in the electrical resistance of the Au electrode could be used as an indication of shape-recovery performance. The linear response of the electrical resistance to strain was identified mainly due to the opening/closing of microcracks and their propagations in the Au electrodes during out-of-plane deformations. With an increment of thermomechanical bending cycles, the electrical resistance was increased exponentially, but it returned back to the original reading when the SMP nanocomposite returned back to its permanent shape. Finally, the flexible Au electrode enabled the actuation of the SMP nanocomposite under an electric voltage of 13.4 V, with an improved shape-recovery performance and temperature distribution.

  15. Solvent stimulated actuation of polyurethane-based shape memory polymer foams using dimethyl sulfoxide and ethanol

    NASA Astrophysics Data System (ADS)

    Boyle, A. J.; Weems, A. C.; Hasan, S. M.; Nash, L. D.; Monroe, M. B. B.; Maitland, D. J.

    2016-07-01

    Solvent exposure has been investigated to trigger actuation of shape memory polymers (SMPs) as an alternative to direct heating. This study aimed to investigate the feasibility of using dimethyl sulfoxide (DMSO) and ethanol (EtOH) to stimulate polyurethane-based SMP foam actuation and the required solvent concentrations in water for rapid actuation of hydrophobic SMP foams. SMP foams exhibited decreased T g when submerged in DMSO and EtOH when compared to water submersion. Kinetic DMA experiments showed minimal or no relaxation for all SMP foams in water within 30 min, while SMP foams submerged in EtOH exhibited rapid relaxation within 1 min of submersion. SMP foams expanded rapidly in high concentrations of DMSO and EtOH solutions, where complete recovery over 30 min was observed in DMSO concentrations greater than 90% and in EtOH concentrations greater than 20%. This study demonstrates that both DMSO and EtOH are effective at triggering volume recovery of polyurethane-based SMP foams, including in aqueous environments, and provides promise for use of this actuation technique in various applications.

  16. Memory

    MedlinePlus

    ... it has to decide what is worth remembering. Memory is the process of storing and then remembering this information. There are different types of memory. Short-term memory stores information for a few ...

  17. Vascular pathology of drug-eluting stents.

    PubMed

    Nakazawa, Gaku; Finn, Aloke V; Virmani, Renu

    2007-06-01

    Polymer-based sirolimus- (Cypher) and paclitaxel-eluting stents (Taxus), so-called drug-eluting stents (DES), have become the treatment of choice for patients with symptomatic coronary artery disease undergoing percutaneous coronary revascularization (PCI). While these stents have reduced rates of restenosis and late lumen loss compared to bare-metal stents (BMS), late thrombosis, a life-threatening complication of this technology, has emerged as a major concern. Our understanding of the pathophysiology of late DES thrombosis is derived from animal and human pathologic samples taken after implantation of these devices. These data indicate that the DES cause substantial impairment in arterial healing characterized by lack of complete reendothelialization and persistence of fibrin when compared to BMS. This so-called delayed healing is "identified as" the primary substrate of an underlying cause of late DES thrombosis at autopsy. Several additional risk factors for late stent thrombosis include penetration of necrotic core, malapposition, overlapping stent placement, excessive stent length, and bifurcation lesions. These represent additional barriers to healing and should be avoided if DES are to be used in order to minimize the late thrombotic risks of these devices. Since the time course of complete healing with DES is unknown, the optimal duration of antiplatelet treatment remains to be determined.

  18. Methotrexate loaded SAE coated coronary stents reduce neointimal hyperplasia in a porcine coronary model

    PubMed Central

    Huang, Y; Salu, K; Liu, X; Li, S; Wang, L; Verbeken, E; Bosmans, J; De Scheerder, I

    2004-01-01

    Objective: To evaluate the effect of stent based methotrexate delivery on neointimal hyperplasia. Methods: Stainless steel coronary stents and biological polymer coated (SAE) stents were randomly implanted in coronary arteries of pigs with a stent to artery ratio of 1.1:1. The pigs were killed after five days (10 stents) or four weeks (20 stents). Second, stainless steel coronary stents were dip coated in a 10 mg/ml methotrexate–SAE polymer solution, resulting in a total load of 150 μg methotrexate/stent. SAE coated stents and methotrexate loaded stents were randomly implanted in porcine coronary arteries with a stent to artery ratio of 1.2:1 and followed up to four weeks. Results: SAE coated stents and bare stents elicited a similar tissue response at five days. At four weeks, neointimal hyperplasia induced by the coated stents was less pronounced than with the bare stents (1.32 (0.66) v 1.73 (0.93) mm2, p > 0.05). In vitro drug release studies showed that 50% of the methotrexate was released in 24 hours, and all drug was released within four weeks. No impact on vascular smooth muscle cell proliferation or viability was observed in in vitro cell cultures. At four weeks the arteries with methotrexate loaded stents had decreased peristrut inflammation and neointimal hyperplasia (1.22 (0.34) v 2.25 (1.28) mm2, p < 0.01). Conclusions: SAE coating had an excellent biocompatibility with vascular tissue. Stent based delivery of methotrexate in the SAE coating effectively reduced neointimal hyperplasia in a porcine coronary stent model, potentially due to reduced peristrut inflammation. PMID:14729797

  19. Memory.

    ERIC Educational Resources Information Center

    McKean, Kevin

    1983-01-01

    Discusses current research (including that involving amnesiacs and snails) into the nature of the memory process, differentiating between and providing examples of "fact" memory and "skill" memory. Suggests that three brain parts (thalamus, fornix, mammilary body) are involved in the memory process. (JN)

  20. Memory.

    ERIC Educational Resources Information Center

    McKean, Kevin

    1983-01-01

    Discusses current research (including that involving amnesiacs and snails) into the nature of the memory process, differentiating between and providing examples of "fact" memory and "skill" memory. Suggests that three brain parts (thalamus, fornix, mammilary body) are involved in the memory process. (JN)

  1. Coronary Stent Materials and Coatings: A Technology and Performance Update.

    PubMed

    O'Brien, Barry; Zafar, Haroon; Ibrahim, Ahmad; Zafar, Junaid; Sharif, Faisal

    2016-02-01

    This paper reviews the current state of the art for coronary stent materials and surface coatings, with an emphasis on new technologies that followed on from first-generation bare metal and drug-eluting stents. These developments have been driven mainly by the need to improve long term outcomes, including late stent thrombosis. Biodegradable drug-eluting coatings aim to address the long term effects of residual durable polymer after drug elution; the SYNERGY, BioMatrix, and Nobori stents are all promising devices in this category, with minimal polymer through the use of abluminal coatings. Textured stent surfaces have been used to attached drug directly, without polymer; the Yukon Choice and BioFreedom stents have some promising data in this category, while a hydroxyapatite textured surface has had less success. The use of drug-filled reservoirs looked promising initially but the NEVO device has experienced both technical and commercial set-backs. However this approach may eventually make it to market if trials with the Drug-Filled Stent prove to be successful. Non-pharmacological coatings such as silicon carbide, carbon, and titanium-nitride-oxide are also proving to have potential to provide better performance than BMS, without some of the longer term issues associated with DES. In terms of biological coatings, the Genous stent which promotes attachment of endothelial progenitor cells has made good progress while gene-eluting stents still have some practical challenges to overcome. Perhaps the most advancement has been in the field of biodegradable stents. The BVS PLLA device is now seeing increasing clinical use in many complex indications while magnesium stents continue to make steady advancements.

  2. Computational Modeling of Shape Memory Polymer Origami that Responds to Light

    NASA Astrophysics Data System (ADS)

    Mailen, Russell William

    Shape memory polymers (SMPs) transform in response to external stimuli, such as infrared (IR) light. Although SMPs have many applications, this investigation focuses on their use as actuators in self-folding origami structures. Ink patterned on the surface of the SMP sheet absorbs thermal energy from the IR light, which produces localized heating. The material shrinks wherever the activation temperature is exceeded and can produce out-of-plane deformation. The time and temperature dependent response of these SMPs provides unique opportunities for developing complex three-dimensional (3D) structures from initially flat sheets through self-folding origami, but the application of this technique requires predicting accurately the final folded or deformed shape. Furthermore, current computational approaches for SMPs do not fully couple the thermo-mechanical response of the material. Hence, a proposed nonlinear, 3D, thermo-viscoelastic finite element framework was formulated to predict deformed shapes for different self-folding systems and compared to experimental results for self-folding origami structures. A detailed understanding of the shape memory response and the effect of controllable design parameters, such as the ink pattern, pre-strain conditions, and applied thermal and mechanical fields, allows for a predictive understanding and design of functional, 3D structures. The proposed modeling framework was used to obtain a fundamental understanding of the thermo-mechanical behavior of SMPs and the impact of the material behavior on hinged self-folding. These predictions indicated how the thermal and mechanical conditions during pre-strain significantly affect the shrinking and folding response of the SMP. Additionally, the externally applied thermal loads significantly influenced the folding rate and maximum bending angle. The computational framework was also adapted to understand the effects of fully coupling the thermal and mechanical response of the material

  3. A semi-analytical study on helical springs made of shape memory polymer

    NASA Astrophysics Data System (ADS)

    Baghani, M.; Naghdabadi, R.; Arghavani, J.

    2012-04-01

    In this paper, the responses of shape memory polymer (SMP) helical springs under axial force are studied both analytically and numerically. In the analytical solution, we first derive the response of a cylindrical tube under torsional loadings. This solution can be used for helical springs in which both the curvature and pitch effects are negligible. This is the case for helical springs with large ratios of the mean coil radius to the cross sectional radius (spring index) and also small pitch angles. Making use of this solution simplifies the analysis of the helical springs to that of the torsion of a straight bar with circular cross section. The 3D phenomenological constitutive model recently proposed for SMPs is also reduced to the 1D shear case. Thus, an analytical solution for the torsional response of SMP tubes in a full cycle of stress-free strain recovery is derived. In addition, the curvature effect is added to the formulation and the SMP helical spring is analyzed using the exact solution presented for torsion of curved SMP tubes. In this modified solution, the effect of the direct shear force is also considered. In the numerical analysis, the 3D constitutive equations are implemented in a finite element program and a full cycle of stress-free strain recovery of an SMP (extension or compression) helical spring is simulated. Analytical and numerical results are compared and it is shown that the analytical solution gives accurate stress distributions in the cross section of the helical SMP spring besides the global load-deflection response. Some case studies are presented to show the validity of the presented analytical method.

  4. Preliminary Evaluation of Clinical and Angiographic Outcomes with Biodegradable Polymer Coated Sirolimus-Eluting Stent in De Novo Coronary Artery Disease: Results of the MANIPAL-FLEX Study

    PubMed Central

    Prajapati, Jayesh; Pai, Umesh; Shetty, Kiran

    2016-01-01

    Objective. The objective of the MANIPAL-FLEX study was to evaluate the feasibility, preliminary safety, and efficacy of the Supraflex sirolimus-eluting stent (SES) implantation, in de novo coronary artery disease, using clinical and quantitative coronary angiography (QCA) follow-ups. Methods. This was a prospective, nonrandomized, multicenter, single-arm study that enrolled 189 patients with de novo coronary artery disease who were treated with the Supraflex SES. Of 189 patients enrolled, the first 61 consecutive patients who consented to a 9-month follow-up evaluation by QCA, irrespective of presence of symptoms, were to be followed up with angiography at 9 months. The primary endpoint of the study was target lesion failure (TLF), including cardiac death, myocardial infarction, and target lesion revascularization during 12-month follow-up after the index procedure. Results. The mean age of the study population was 58 ± 11 years, with 51.3% (97/189) of hypertensive patients. Total of 66 lesions, analyzed by offline QCA, showed good scaffolding of the target vessel with in-stent late lumen loss at 9 months of 0.18 ± 0.23 mm. The observed TLF at 30-day, 6-month, and 12-month follow-up were 2 (1.1%), 6 (3.2%), and 10 (5.3%), respectively. Conclusion. This study provides preliminary evidence for the feasibility, safety, and efficacy of the Supraflex sirolimus-eluting stent. PMID:27597929

  5. New stents for SFA.

    PubMed

    MINAR, E; SCHILLINGER, M

    2009-10-01

    Endovascular stent implantation was introduced to femoropopliteal procedures almost two decades ago. Initial results with balloon-expandable stainless steel stents and self expanding Elgiloy stents, however, were disappointing. In particular, recurrence rates after long-segment femoropopliteal stenting were rather high, in the range of 60% to 80% at 1 year. After years of stagnation, recent developments in femoropopliteal stent technology have been promising. Self-expanding nitinol stents have been evaluated in several prospective studies. Initial problems with stent fractures seem to be resolved using second-generation devices. The second generation of Nitinol stents have an enhanced flexibility particularly also in axial direction due to a reduction of cell interconnections and a more spiral orientation of the interconnections. However, until now there is no proof of any impact of the stent design on restenosis rate. Otherwise, stenting has been shown to be beneficial compared to balloon angioplasty especially in longer femoropopliteal lesions. The superior fracture resistance of the latest stent generation in combination with the production of long nitinol stents of up to 20 cm in length allow that more difficult and complex lesions can be treated endovascularly. The main unresolved problem with femoropopliteal stenting is the treatment of instent restenosis. Future concepts to further improve long-term patency after femoropopliteal stenting are therefore under investigation, including drug-eluting stents (DES), biodegradable stents, and coated stent-grafts. Stent grafts appear to be a viable option for the treatment of complex superficial femoral artery lesions, with comparable outcomes to prosthetic above-knee femoropopliteal bypass surgery. Concerning DES, we have to wait for the results of the ongoing studies.

  6. Multistability, ionic doping, and charge dynamics in electrosynthesized polypyrrole, polymer-nanoparticle blend nonvolatile memory, and fixed p-i-n junction polymer light-emitting electrochemical cells

    NASA Astrophysics Data System (ADS)

    Simon, Daniel Theodore

    A variety of factors make semiconducting polymers a fascinating alternative for both device development and new areas of fundamental research. Among these are solution processability, low cost, flexibility, and the strong dependence of conduction on the presence of charge compensating ions. With the lack of a complete fundamental understanding of the materials, and the growing demand for novel solutions to semiconductor device design, research in the field can take many, often multifaceted, routes. Due to ion-mediated conduction and versatility of fabrication, conducting polymers can provide a route to the study of neural signaling. In the first of three research topics presented, junctions of polypyrrole electropolymenzed on microelectrode arrays are demonstrated. Indi vidual junctions, when synthesized in a three-electrode configuration, exhibit current switching behavior analogous to neural weighting. Junctions copolymerized with thiophene exhibit current rectification and the nonlinear current-voltage behavior requisite for complex neural systems. Applications to larger networks, and eventual use in analysis of signaling, are discussed. In the second research topic, nonvolatile resistive memory consisting of gold nanoparticles embedded in a polymer film is examined using admittance spectroscopy. The frequency dependence of the devices indicates space-charge-limited transport in the high-conductivity "on" state, and similar transport in the lower-conductivity "off' state. Furthermore, a larger do capacitance of the on state indicates that a greater amount of filling of midgap trap levels introduced by the nanoparticles increases conductivity, leading to the memory effect. Implications on the question as to whether or not the on state is the result of percolation pathways is discussed. The third and final research topic is a presentation of enhanced efficiency of polymer light-emitting electrochemical cells (LECs) by means of forming a doping self

  7. Differences in vessel healing following delivery of everolimus or paclitaxel: a comparative experimental study using identical stent and biodegradable polymer platforms.

    PubMed

    Buszman, Piotr P; Milewski, Krzysztof; Pająk, Jacek; Jelonek, Michał; Orlik, Bartłomiej; Krauze, Agata; Gwiazdowska-Nowotka, Beata; Wojakowski, Wojciech; Tellez, Armando; Granada, Juan F; Buszman, Paweł E

    2014-10-01

    We aimed to compare the vascular effects exclusive to antiproliferative agents by using identical stent and biodegradable polymeric matrices eluting everolimus (BP-EES) (Carlo; Balton) and paclitaxel (BP-PES) (Luc-Chopin2; Balton) in the porcine model of coronary injury. A total of 37 stents were implanted with 110% overstretch in the coronary arteries of 14 domestic pigs: 13 BP-PES, 16 BP-EES and eight bare metal stents (BMS) (Chopin2; Balton). Coronary angiography was performed after 28 and 90 days, the animals were sacrificed and the stented segments harvested for histopathological evaluation. At 28 days, BP-PES most effectively limited angiographic late loss (LL PES: 0.15±0.1 vs. EES: 0.40±0.3 vs. BMS: 0.5±0.2 mm; p=0.04) and neointimal thickness (NT) in histology (PES: 0.12 [0.1-0.2] vs. EES: 0.38 [0.3-0.4] vs. BMS: 0.35 [0.3-0.4] mm; p<0.01). The BP-PES had lower endothelialisation (EES: 100% vs. PES: 40±4% vs. BMS: 97.5±5%; p<0.01) and slightly higher inflammation scores (EES: 1 vs. PES: 2.1±0.3 vs. BMS: 1; p<0.01). At three months, LL remained unchanged in the EES and BMS groups in contrast to an increase in the PES group (EES: 0.38±0.3 vs. PES: 0.52±0.4 vs. BMS: 0.51±0.3 mm; p=0.69). NT stabilised at 90 days in the EES group in comparison to a fourfold increase in the PES group and a 30% increase in the BMS group (EES: 0.35 [0.3-0.5] vs. PES: 0.53 [0.5-0.8] vs. BMS: 0.46 [0.4-0.5] mm: p=0.07). Stent endothelialisation and inflammation were comparable at 90 days in all groups. Temporal differences in vascular response were seen by the delivery of different antiproliferative agents. In contrast to everolimus, paclitaxel seems to induce a slightly higher degree of inflammation in the short term, potentially leading to further neointimal hyperplasia in the long term.

  8. Deformation behavior of carbon-fiber reinforced shape-memory-polymer composites used for deployable structures (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Lan, Xin; Liu, Liwu; Li, Fengfeng; Pan, Chengtong; Liu, Yanju; Leng, Jinsong

    2017-04-01

    Shape memory polymers (SMPs) are a new type of smart material, they perform large reversible deformation with a certain external stimulus (e.g., heat and electricity). The properties (e.g., stiffness, strength and other mechanically static or quasi-static load-bearing capacity) are primarily considered for conventional resin-based composite materials which are mainly used for structural materials. By contrast, the mechanical actuating performance with finite deformation is considered for the shape memory polymers and their composites which can be used for both structural materials and functional materials. For shape memory polymers and their composites, the performance of active deformation is expected to further promote the development in smart active deformation structures, such as deployable space structures and morphing wing aircraft. The shape memory polymer composites (SMPCs) are also one type of High Strain Composite (HSC). The space deployable structures based on carbon fiber reinforced shape memory polymer composites (SMPCs) show great prospects. Considering the problems that SMPCs are difficult to meet the practical applications in space deployable structures in the recent ten years, this paper aims to research the mechanics of deformation, actuation and failure of SMPCs. In the overall view of the shape memory polymer material's nonlinearity (nonlinearity and stress softening in the process of pre-deformation and recovery, relaxation in storage process, irreversible deformation), by the multiple verifications among theory, finite element and experiments, one obtains the deformation and actuation mechanism for the process of "pre-deformation, energy storage and actuation" and its non-fracture constraint domain. Then, the parameters of SMPCs will be optimized. Theoretical analysis is realized by the strain energy function, additionally considering the interaction strain energy between the fiber and the matrix. For the common resin-based or soft

  9. Second- and third-generation drug-eluting coronary stents: progress and safety.

    PubMed

    Akin, I; Schneider, H; Ince, H; Kische, S; Rehders, T C; Chatterjee, T; Nienaber, C A

    2011-05-01

    Drug-eluting stents (DES) have revolutionized the treatment of coronary artery disease by reducing the rate of in-stent restenosis from 20-40% with bare-metal stent (BMS) to 6-8% with DES. However, with widespread use of DES, safety concerns have risen due to the observation of late stent thrombosis. With this in mind and better understanding of mechanism and pathophysiology of stent thrombosis, the technological platform, especially innovative anti-restenotic agents, polymeric coatings, and stent platforms, improved with newer DES. Two second-generation DES, the Endeavor zotarolimus-eluting stent (ZES) and the Xience-V everolimus-eluting stent (EES), have provided promising results in both randomized controlled trials (SPIRIT and ENDEAVOR) and registries (E-Five, COMPARE) compared with bare-metal stents (BMS) and first-generation DES. Newer third-generation stent technology, especially biodegradable polymers, polymer-free stents, and biodegradable stents on the basis of poly-L-lactide (PLLA) or magnesium, has been evaluated in preclinical and initial clinical trials. However, despite encouraging initial results, long-term data of large-scale randomized trials as well as registries comparing them to currently approved first- and second-generation DES are still lacking.

  10. Self-assembled regular arrays of carbon nanotube and the route toward actuation of shape memory polymer

    NASA Astrophysics Data System (ADS)

    Lu, Haibao; Wu, Chunxia; Liu, Yanju; Gou, Jan; Leng, Jinsong

    2010-04-01

    The synthesis of massive arrays of monodispersed carbon nanotubes that are self-assembled on hydrophilic polycarbonate membrane is reported. This approach involves individual carbon nanotube manufacturing by non-ionic surfactant to aid in dispersion and nanotubes self-assembled for three-dimensional orientation by high press filtration. The inherent capability of carbon nanotube and microstructure of well-packed arrays predominate excellent conductive properties of massive arrays. These potential applications of nanometer-sized sensor, probe and energy resistor have been characterized in this study. Furthermore, the route toward application of self-assembled regular arrays, as heat transmission intermedium, has been carried out by activating shape-memory polymer. The electrical conductivity of insulating polymer is significantly improved by assembled carbon nanotubes, resulting in shape recovery behavior of nanocomposite being driven by electrical resistive heating.

  11. Fabrication and static characterization of carbon-fiber-reinforced polymers with embedded NiTi shape memory wire actuators

    NASA Astrophysics Data System (ADS)

    de Araújo, C. J.; Rodrigues, L. F. A.; Coutinho Neto, J. F.; Reis, R. P. B.

    2008-12-01

    In this work, unidirectional carbon-fiber-reinforced polymers (CFRP) with embedded NiTi shape memory alloy (SMA) wire actuators were manufactured using a universal testing machine equipped with a thermally controlled chamber. Beam specimens containing cold-worked, annealed and trained NiTi SMA wires distributed along their neutral plane were fabricated. Several tests in a three-point bending mode at different constant temperatures were performed. To verify thermal buckling effects, electrical activation of the specimens was realized in a cantilevered beam mode and the influence of the SMA wire actuators on the tip deflection of the composite is demonstrated.

  12. Polymers.

    ERIC Educational Resources Information Center

    Tucker, David C.

    1986-01-01

    Presents an open-ended experiment which has students exploring polymer chemistry and reverse osmosis. This activity involves construction of a polymer membrane, use of it in a simple osmosis experiment, and application of its principles in solving a science-technology-society problem. (ML)

  13. Polymers.

    ERIC Educational Resources Information Center

    Tucker, David C.

    1986-01-01

    Presents an open-ended experiment which has students exploring polymer chemistry and reverse osmosis. This activity involves construction of a polymer membrane, use of it in a simple osmosis experiment, and application of its principles in solving a science-technology-society problem. (ML)

  14. Polymer Nanodot-Hybridized Alkyl Silicon Oxide Nanostructures for Organic Memory Transistors with Outstanding High-Temperature Operation Stability

    PubMed Central

    Lee, Chulyeon; Seo, Jooyeok; Kim, Jeongnam; Jeong, Jaehoon; Han, Hyemi; Kim, Hwajeong; Kim, Youngkyoo

    2016-01-01

    Organic memory devices (OMDs) are becoming more important as a core component in flexible electronics era because of their huge potentials for ultrathin, lightweight and flexible plastic memory modules. In particular, transistor-type OMDs (TOMDs) have been gradually spotlighted due to their structural advantages possessing both memory and driving functions in single devices. Although a variety of TOMDs have been developed by introducing various materials, less attention has been paid to the stable operation at high temperatures. Here we demonstrate that the polymer nanodot-embedded alkyl silicon oxide (ASiO) hybrid materials, which are prepared by sol-gel and thermal cross-linking reactions between poly(4-vinylphenol) (PVP) and vinyltriethoxysilane, can deliver low-voltage (1~5 V) TOMDs with outstanding operation stability (>4700 cycles) at high temperatures (150 °C). The efficient low-voltage memory function is enabled by the embedded PVP nanodots with particular lattice nanostructures, while the high thermal stability is achieved by the cross-linked ASiO network structures. PMID:27703187

  15. Polymer Nanodot-Hybridized Alkyl Silicon Oxide Nanostructures for Organic Memory Transistors with Outstanding High-Temperature Operation Stability.

    PubMed

    Lee, Chulyeon; Seo, Jooyeok; Kim, Jeongnam; Jeong, Jaehoon; Han, Hyemi; Kim, Hwajeong; Kim, Youngkyoo

    2016-10-05

    Organic memory devices (OMDs) are becoming more important as a core component in flexible electronics era because of their huge potentials for ultrathin, lightweight and flexible plastic memory modules. In particular, transistor-type OMDs (TOMDs) have been gradually spotlighted due to their structural advantages possessing both memory and driving functions in single devices. Although a variety of TOMDs have been developed by introducing various materials, less attention has been paid to the stable operation at high temperatures. Here we demonstrate that the polymer nanodot-embedded alkyl silicon oxide (ASiO) hybrid materials, which are prepared by sol-gel and thermal cross-linking reactions between poly(4-vinylphenol) (PVP) and vinyltriethoxysilane, can deliver low-voltage (1~5 V) TOMDs with outstanding operation stability (>4700 cycles) at high temperatures (150 °C). The efficient low-voltage memory function is enabled by the embedded PVP nanodots with particular lattice nanostructures, while the high thermal stability is achieved by the cross-linked ASiO network structures.

  16. Polymer Nanodot-Hybridized Alkyl Silicon Oxide Nanostructures for Organic Memory Transistors with Outstanding High-Temperature Operation Stability

    NASA Astrophysics Data System (ADS)

    Lee, Chulyeon; Seo, Jooyeok; Kim, Jeongnam; Jeong, Jaehoon; Han, Hyemi; Kim, Hwajeong; Kim, Youngkyoo

    2016-10-01

    Organic memory devices (OMDs) are becoming more important as a core component in flexible electronics era because of their huge potentials for ultrathin, lightweight and flexible plastic memory modules. In particular, transistor-type OMDs (TOMDs) have been gradually spotlighted due to their structural advantages possessing both memory and driving functions in single devices. Although a variety of TOMDs have been developed by introducing various materials, less attention has been paid to the stable operation at high temperatures. Here we demonstrate that the polymer nanodot-embedded alkyl silicon oxide (ASiO) hybrid materials, which are prepared by sol-gel and thermal cross-linking reactions between poly(4-vinylphenol) (PVP) and vinyltriethoxysilane, can deliver low-voltage (1~5 V) TOMDs with outstanding operation stability (>4700 cycles) at high temperatures (150 °C). The efficient low-voltage memory function is enabled by the embedded PVP nanodots with particular lattice nanostructures, while the high thermal stability is achieved by the cross-linked ASiO network structures.

  17. Impact of stent strut design in metallic stents and biodegradable scaffolds.

    PubMed

    Foin, Nicolas; Lee, Renick D; Torii, Ryo; Guitierrez-Chico, Juan Luis; Mattesini, Alessio; Nijjer, Sukhjinder; Sen, Sayan; Petraco, Ricardo; Davies, Justin E; Di Mario, Carlo; Joner, Michael; Virmani, Renu; Wong, Philip

    2014-12-20

    Advances in the understanding of healing mechanisms after stent implantation have led to the recognition of stent strut thickness as an essential factor affecting re-endothelialization and overall long term vessel healing response after Percutaneous Coronary Interventions (PCI). Emergence of Drug-eluting stents (DESs) with anti-proliferative coating has contributed to reducing the incidence of restenosis and Target Lesion Revascularization (TVR), while progress and innovations in stent materials have in the meantime facilitated the design of newer platforms with more conformability and thinner struts, producing lesser injury and improving integration into the vessel wall. Recent advances in biodegradable metal and polymer materials now also allow for the design of fully biodegradable platforms, which are aimed at scaffolding the vessel only temporarily to prevent recoil and constrictive remodeling of the vessel during the initial period required, and are then progressively resorbed thereby avoiding the drawback of leaving an unnecessary implant permanently in the vessel. The aim of this article is to review recent evolution in stent material and stent strut design while understanding their impact on PCI outcomes. The article describes the different metallic alloys and biodegradable material properties and how these have impacted the evolution of stent strut thickness and ultimately outcomes in patients. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  18. Research of Customized Aortic Stent Graft Manufacture

    NASA Astrophysics Data System (ADS)

    Zhang, Lei; Chen, Xin; Liu, Muhan

    2017-03-01

    Thoracic descending aorta diseases include aortic dissection and aortic aneurysm, of which the natural mortality rate is extremely high. At present, endovascular aneurysm repair (EVAR) has been widely used as an effective means for the treatment of descending aortic disease. Most of the existing coating stents are standard design, which are unable to meet the size or structure of different patients. As a result, failure of treatment would be caused by dimensional discrepancy between stent and vessels, which could lead to internal leakage or rupture of blood vessels. Therefore, based on rapid prototyping sacrificial core - coating forming (RPSC-CF), a customized aortic stent graft manufactured technique has been proposed in this study. The aortic stent graft consists of film and metallic stent, so polyether polyurethane (PU) and nickel-titanium (NiTi) shape memory alloy with good biocompatibility were chosen. To minimum film thickness without degrading performance, effect of different dip coating conditions on the thickness of film were studied. To make the NiTi alloy exhibit super-elasticity at body temperature (37°C), influence of different heat treatment conditions on austenite transformation temperature (Af) and mechanical properties were studied. The results show that the customized stent grafts could meet the demand of personalized therapy, and have good performance in blasting pressure and radial support force, laying the foundation for further animal experiment and clinical experiment.

  19. Pitavastatin-incorporated nanoparticle-eluting stents attenuate in-stent stenosis without delayed endothelial healing effects in a porcine coronary artery model.

    PubMed

    Tsukie, Noriaki; Nakano, Kaku; Matoba, Tetsuya; Masuda, Seigo; Iwata, Eiko; Miyagawa, Miho; Zhao, Gang; Meng, Wei; Kishimoto, Junji; Sunagawa, Kenji; Egashira, Kensuke

    2013-01-01

    The use of currently marketed drug-eluting stents presents safety concerns including increased late thrombosis, which is thought to result mainly from delayed endothelial healing effects (impaired re-endothelialization resulting in abnormal inflammation and fibrin deposition). We recently developed a bioabsorbable polymeric nanoparticle (NP)-eluting stent using a novel cationic electrodeposition technology. Statins are known to inhibit the proliferation of vascular smooth muscle cells (VSMC) and to promote vascular healing. We therefore hypothesized that statin-incorporated NP-eluting stents would attenuate in-stent stenosis without delayed endothelial healing effects. Among six marketed statins, pitavastatin (Pitava) was found to have the most potent effects on VSMC proliferation and endothelial regeneration in vitro. We thus formulated a Pitava-NP-eluting stent (20µg Pitava per stent). In a pig coronary artery model, Pitava-NP-eluting stents attenuated in-stent stenosis as effectively as polymer-coated sirolimus-eluting stents (SES). At SES sites, delayed endothelial healing effects were noted, whereas no such effects were observed in Pitava-N