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1

Synthesis and biological evaluation of a series of new germanium phthalocyanines incorporated into liposomes--part II: biological evaluation  

NASA Astrophysics Data System (ADS)

The pharmacokinetic and phototherapeutic properties of new phthalocyanines with Ge(IV) or Si(VI) as the central metal ion and cholesterol, cholestan or long-chain fatty acids residues as axial ligands to the central ion have been studied in tumor-bearing mice. The new photosensitizers were selectively taken up by and relatively quickly released from the tumors. Except for Si(IV)-Pc, which showed a comparably high selectivity for tumor versus peritumoral tissue, all Ge(IV)-Pc were less selective than liposomal Zn-Pc (CGP 55847). However, all the new compounds showed excellent phototherapeutic efficiency at very low drug and light doses in studies in Meth-A-sarcoma-bearing mice.

Schieweck, Klaus; Capraro, Hans-Georg; Isele, Ute; Batt, Ernst; Ochsner, Martin; van Hoogevest, Peter; Love, William G.

1994-03-01

2

Large-scale production of liposomes containing monomeric zinc phthalocyanine by controlled dilution of organic solvents.  

PubMed

This work describes the development of an organic solvent dilution method suitable for the large scale manufacturing of small unilamellar liposomes containing the water-insoluble photosensitizer zinc phthalocyanine in the monomeric state. N-Methyl pyrrolidone (NMP)/tert-butyl alcohol was selected as water miscible organic phase in which the phospholipids 1-palmitoyl, 2-oleoylphosphatidylcholine (POPC), and 1,2-dioeloylphosphatidylserine (OOPS) and the dye were dissolved. This organic phase was mixed with an excess of a water phase using a dynamic mixing device, yielding reproducibly unilamellar liposomes with a mean size of 50-150 nm as measured with quasielastic light scattering. After concentration, the organic solvents were efficiently removed by cross-flow filtration. The liposomes were then sterile filtered and freeze-dried. A method to measure the aggregation state of the dye in the liposomes was developed. A stable lyophilized formulation containing monomeric liposomal ZnPc could be obtained by using a solution of ZnPc in NMP (2 mg/mL) and ZnPc/phospholipid (1:100 w/w ratio) and performing concentration and dialysis at 4 degrees C and lyophilization in presence of a mixture of lactose and phospholipid (5:1 w/w ratio). PMID:7891283

Isele, U; van Hoogevest, P; Hilfiker, R; Capraro, H G; Schieweck, K; Leuenberger, H

1994-11-01

3

Enhanced photodynamic leishmanicidal activity of hydrophobic zinc phthalocyanine within archaeolipids containing liposomes  

PubMed Central

In this work, the in vitro anti-Leishmania activity of photodynamic liposomes made of soybean phosphatidylcholine, sodium cholate, total polar archaeolipids (TPAs) extracted from the hyperhalophile archaea Halorubrum tebenquichense and the photosensitizer zinc phthalocyanine (ZnPcAL) was compared to that of ultradeformable photodynamic liposomes lacking TPAs (ZnPcUDLs). We found that while ZnPcUDLs and ZnPcALs (130 nm mean diameter and ?35 mV zeta potential) were innocuous against promastigotes, a low concentration (0.01 ?M ZnPc and 7.6 ?M phospholipids) of ZnPcALs irradiated at a very low-energy density (0.2 J/cm2) eliminated L. braziliensis amastigotes from J774 macrophages, without reducing the viability of the host cells. In such conditions, ZnPcALs were harmless for J774 macrophages, HaCaT keratinocytes, and bone marrow-derived dendritic cells. Therefore, topical photodynamic treatment would not likely affect skin-associated lymphoid tissue. ZnPcALs were extensively captured by macrophages, but ZnPcUDLs were not, leading to 2.5-fold increased intracellular delivery of ZnPc than with ZnPcUDLs. Despite mediating low levels of reactive oxygen species, the higher delivery of ZnPc and the multiple (caveolin- and clathrin-dependent plus phagocytic) intracellular pathway followed by ZnPc would have been the reason for the higher antiamastigote activity of ZnPcALs. The leishmanicidal activity of photodynamic liposomal ZnPc was improved by TPA-containing liposomes.

Perez, Ana Paula; Casasco, Agustina; Schilrreff, Priscila; Defain Tesoriero, Maria Victoria; Duempelmann, Luc; Altube, Maria Julia; Higa, Leticia; Morilla, Maria Jose; Petray, Patricia; Romero, Eder L

2014-01-01

4

Localization of zinc(II)-phthalocyanine within implanted tumors after intravenous administration of a liposomal formulation  

NASA Astrophysics Data System (ADS)

The liposomal zinc(II) phthalocyanine (Zn-Pc) formulation CGP55847 was administered intravenously (0.5 mg Zn-Pc/kg) to C57/BL6 mice bearing subcutaneously implanted B16 melanomas or to Swiss mice bearing intramuscularly implanted Ehrlich carcinomas. Tumors were removed 3 or 24 h after dosing, and the Zn-Pc content and intratumoral distribution determined by extraction and quantitative fluorescence microscopy. Localization of the photosensitizer within the tumor mass occurred more rapidly in the highly vascularized Ehrlich carcinoma compared to the less highly vascularized B16 melanoma. Zn-Pc was evident in and around blood vessels 3 but not 24 h after dosing. More Zn-Pc was found in necrotic areas compared to viable tumor tissue; little or no Zn-Pc was detected in the muscle tissue invaded by the Ehrlich carcinoma. At the cellular level, Zn-Pc was associated with membranes and the cytosol but not the nucleus.

Duk, Saskia; Biolo, Roberta; Love, William G.; Jori, Giulio; Taylor, Peter W.

1994-10-01

5

Localization of zinc(II)-phthalocyanine within implanted tumors after intravenous administration of a liposomal formulation  

NASA Astrophysics Data System (ADS)

The liposomal zinc(II) phthalocyanine (Zn-Pc) formulation CGP55847 was administered intravenously (0.5 mg Zn-Pc/kg) to C57/BL6 mice bearing subcutaneously implanted B16 melanomas or to Swiss mice bearing intramuscularly implanted Ehrlich carcinomas. Tumors were removed 3 or 24 h after dosing, and the Zn-Pc content and intratumoral distribution determined by extraction and quantitative fluorescence microscopy. Localization of the photosensitizer within the tumor mass occurred more rapidly in the highly vascularized Ehrlich carcinoma compared to the less highly vascularized B16 melanoma. Zn-Pc was evident in and around blood vessels 3 but not 24 h after dosing. More Zn-Pc was found in necrotic areas compared to viable tumor tissue; little or no Zn-Pc was detected in the muscle tissue invaded by the Ehrlich carcinoma. At the cellular level, Zn-Pc was associated with membranes and the cytosol but not the nucleus.

Duk, Saskia; Biolo, Roberta; Love, William G.; Jori, Giulio; Taylor, Peter W.

1995-03-01

6

Mitochondria, endoplasmic reticulum and actin filament behavior after PDT with chloroaluminum phthalocyanine liposomal in HeLa cells.  

PubMed

Photodynamic therapy (PDT) for cancer is a therapeutic modality in the treatment of tumors in which visible light is used to activate a photosensitizer. Cell membranes have been identified as an important intracellular target for singlet oxygen produced during the photochemical pathway. This study analyzed the cytotoxicity in specific cellular targets of a photosensitizer used in PDT in vitro. The photosensitizing effects of chloroaluminum phthalocyanine liposomal were studied on the mitochondria, cytoskeleton and endoplasmic reticulum of HeLa cells. Cells were irradiated with a diode laser working at 670 nm, energy density of 4.5 J/cm2 and power density of 45 mW/cm2. Fluorescence microscopic analysis of the mitochondria showed changes in membrane potential. After PDT treatment, the cytoskeleton and endoplasmic reticulum presented basic alterations in distribution. The combined effect of AlPHCl liposomal and red light in the HeLa cell line induced photodamage to the mitochondria, endoplasmic reticulum and actin filaments in the cytoskeleton. PMID:18485750

Maftoum-Costa, Maíra; Naves, Karina Teixeira; Oliveira, Alexandre Lima; Tedesco, Antonio Cláudio; da Silva, Newton Soares; Pacheco-Soares, Cristina

2008-08-01

7

Spectroscopic Probing of the Acid–Base Properties and Photosensitization of a Fluorinated Phthalocyanine in Organic Solutions and Liposomes  

Microsoft Academic Search

A perfluorinated derivative of phthalocyanine was syn- thesized as the free base, hexadeca-(2,2,2-trifluoroethoxy) phthalocyanine (H2F48Pc), and as a zinc complex, hex- adeca-(2,2,2-trifluoroethoxy)-phthalocyaninatozinc (ZnF48Pc), and their spectroscopic and photochemical properties were studied. The absorption bands are shift- ed bathochromically relative to simple phthalocyanines, exhibiting the longest wavelength band near 735 nm (H2F48Pc) and 705 (ZnF48Pc). The solvatochromism of both compounds was

Hana Weitman; Smadar Schatz; Hugo E. Gottlieb; Nagao Kobayashi; Benjamin Ehrenberg

2001-01-01

8

Phthalocyanine polymers  

NASA Technical Reports Server (NTRS)

A method of forming 4,4',4'',4''' -tetraamino phthalocyanines involves reducing 4,4',4'',4''' -tetranitro phthalocyanines, polymerizing the metal tetraamino phthalocyanines with a tetracarboxylic dianhydride (preferably aromatic) or copolymerizing with a tetracarboxylic dianhydride and a diamine (preferably also aromatic) to produce amic acids which are then dehydrocyclized to imides. Thermally and oxidatively stable polymers result which form tough, flexible films, varnishes, adhesives, and fibers.

Achar, B. N.; Fohlen, G. M.; Parker, J. A. (inventors)

1985-01-01

9

Photodynamic therapy of Porphyromonas gingivalis via liposome-encapsulated sensitizers.  

PubMed

Photodynamic therapy exploits the light-activation of a photosensitizer to cause cytotoxicity. Liposomes can be used to deliver hydrophobic photosensitizers to bacteria. Positively charged dioleoyltrimethylammoniumpropane:palmitoyloleoylphosphatidylcholine (1:1) liposomes bound quantitatively to the periodontal pathogen, Porphyromonas gingivalis. Following illumination, free and liposomal zinc phthalocyanine reduced the colony-forming unit (CFU) to 65 percent and 23 percent of controls, respectively. Thus, localization of the photosensitizer at the surface of bacteria via liposome binding enhanced the photodynamic cytotoxicity of zinc phthalocyanine. PMID:24341134

Ko, Alex; Yee, Michael; Skupin-Mrugalska, Paulina; Düzgünes, Nejat

2013-11-01

10

Photodynamic ultradeformable liposomes: Design and characterization.  

PubMed

Hydrophobic ([tetrakis(2,4-dimetil-3-pentyloxi)-phthalocyaninate]zinc(II)) (ZnPc) and hydrophilic ([tetrakis(N,N,N-trimethylammoniumetoxi)-phthalocyaninate]zinc(II) tetraiodide) (ZnPcMet) phthalocyanines were synthesized and loaded in ultradeformable liposomes (UDL) of soybean phosphatidylcholine and sodium cholate (6:1, w/w, ratio), resulting 100 nm mean size vesicles of negative Zeta potential, with encapsulation efficiencies of 85 and 53%, enthalpy of phase transition of 5.33 and 158 J/mmol for ZnPc and ZnPcMet, respectively, indicating their deep and moderate partition into UD matrices. Matrix elasticity of UDL-phthalocyanines resulted 28-fold greater than that of non-UDL, leaking only 25% of its inner aqueous content after passage through a nanoporous barrier versus 100% leakage for non-UDL. UDL-ZnPc made ZnPc soluble in aqueous buffer while kept the monomeric state, rendering singlet oxygen quantum yield (Phi(Delta)) similar to that obtained in ethanol (0.61), whereas UDL-ZnPcMet had a four-fold higher Phi(Delta) than that of free ZnPcMet (0.21). Free phthalocyanines were non-toxic at 1 and 10 microM, both in dark or upon irradiation at 15 J/cm2 on Vero and J-774 cells (MTT assay). Only liposomal ZnPc at 10 microM was toxic for J-774 cells under both conditions. Additionally, endo-lysosomal confinement of the HPTS dye was kept after irradiation at 15 J/cm2 in the presence of UDL-phtalocyanines. This could lead to improve effects of singlet oxygen against intra-vesicular pathogen targets inside the endo-lysosomal system. PMID:17157460

Montanari, J; Perez, A P; Di Salvo, F; Diz, V; Barnadas, R; Dicelio, L; Doctorovich, F; Morilla, M J; Romero, E L

2007-02-01

11

Method of solubilizing phthalocyanines and metallophthalocyanines.  

National Technical Information Service (NTIS)

A one-step method of manufacturing soluble phthalocyanines and metallophthalocyanines, like zinc phthalocyanine, by converting a phthalocyanine or a metallophthalocyanine to a trialkylsilyl-substituted derivative is disclosed. The phthalocyanine or metall...

J. W. Rathke M. J. Chen C. M. Fendrick

1990-01-01

12

Investigation of factors affecting controlled release from photosensitive DMPC and DSPC liposomes.  

PubMed

An investigation of liposomes comprised of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) or 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) lipids with cholesterol and zinc phthalocyanine (ZnPC) revealed that several fundamental liposome properties are influenced by composition and by lipid-specific features. DMPC and DSPC liposomes were synthesized, and their compositional changes, encapsulation capacities, morphologies, and release properties were evaluated. In this research, liposome degradation, lysis, and content release were initiated by photolysis, i.e., rupture induced by exposure to light. A controlled release mechanism was created through the introduction of photosensitizers (i.e., ZnPC) embedded within the cholesterol-stabilized liposome membrane. The light wavelength and light exposure time accelerated photodegradation properties of DMPC liposomes compared to DSPC liposomes, which exhibited a slower release rate. Morphological changes in the liposomes were strongly influenced by light wavelength and light exposure time. For both the DMPC and DSPC liposomes, visible light with wavelengths in the red end of the spectrum and broad spectrum ambient lighting (400-700 nm) were more effective for lysis than UV-A light (365 nm). Heating liposomes to 100 °C decreased the stability of liposomes compared to liposomes kept at room temperatures. In addition, the optimal lipid-to-cholesterol-to-photoactivator ratio that produced the most stable liposomes was determined. PMID:22592778

Aygun, Aysegul; Torrey, Kathryn; Kumar, Ashok; Stephenson, Larry D

2012-06-01

13

Interaction of photosensitizers with membranes of liposomes and of erythrocytes  

NASA Astrophysics Data System (ADS)

There was investigated the interaction of two Russian photosensitizers: Photohem (hematoporphyrin derivative, HPD) and Photosense (sulfonated aluminum phthalocyanine, AlPc) with membranes of the liposomes and of the erythrocytes; and effect of laser irradiation (LI) in the presence of HPD and AlPc on lipid peroxidation of liposomes and photosensitized hemolysis of human erythrocytes. There were studied the interaction of HPD and AlPc with membranes of the liposomes and of the erythrocytes by methods of ultra-centrifugation, ultra-filtration, gel-filtration. An increase of hemolysis of erythrocytes in vivo after PDT was found out. It was found out that, photosensitized lipid peroxidation of liposomes and photosensitized hemolysis of human erythrocytes in vivo and in vitro was inhibited by antioxidants (alpha-tocopherol, carotinoids, flavonoids).

Klebanov, Gennady I.; Stranadko, Eugeny F.; Teselkin, Y. O.; Babenkova, Irina V.; Chichuk, Tatyana V.

1996-12-01

14

Doped colorimetric assay liposomes  

DOEpatents

The present invention provides compositions comprising colorimetric assay liposomes. The present invention also provides methods for producing colorimetric liposomes and calorimetric liposome assay systems. In preferred embodiments, these calorimetric liposome systems provide high levels of sensitivity through the use of dopant molecules. As these dopants allow the controlled destabilization of the liposome structure, upon exposure of the doped liposomes to analyte(s) of interest, the indicator color change is facilitated and more easily recognized.

Charych, Deborah (Albany, CA); Stevens, Raymond C. (Albany, CA)

2001-01-01

15

Thermosetting Phthalocyanine Polymers  

NASA Technical Reports Server (NTRS)

Group of phthalocyanine polymers resist thermal degradation. Polymers expected semiconducting. Principal applications probably in molded or laminated parts that have to withstand high temperatures. Polymers made from either of two classes of monomer: Bisphthalonitriles with imide linkages or Bisphthalonitriles with ester-imide linkages.

Fohlen, G.; Parker, J.; Achar, B.

1985-01-01

16

Method of solubilizing phthalocyanines and metallophthalocyanines  

DOEpatents

A one-step method of manufacturing soluble phthalocyanines and metallophthalocyanines, like zinc phthalocyanine, by converting a phthalocyanine or a metallophthalocyanine to a trialkylsilyl-substituted derivative is disclosed. The phthalocyanine or metallophthalocyanine is converted to a soluble trialkylsilyl-substituted derivative by interacting the phthalocyanine or metallophthalocyanine with an active metal amide, like lithium 2,2,6,6-tetramethylpiperidide, and a halotrialkylsilane, like chlorotrimethylsilane, to provide a phthalocyanine compound, like phthalocyanine monomers, dimers or polymers, metalated or unmetalated, that are soluble in organic media.

Rathke, Jerome W. (Bolingbrook, IL); Chen, Michael J. (Darien, IL); Fendrick, Carol M. (Downers Grove, IL)

1997-01-01

17

New Directions in Phthalocyanine Pigments  

NASA Technical Reports Server (NTRS)

The objectives were the following: (1) investigation of the synthesis of new phthalocyanines; (2) characterization of the new phthalocyanines synthesized; (3) investigate the properties of the newly synthesized phthalocyanines with emphasis on UV protection of plastics and coatings; and (4) utilize quantum mechanics to evaluate the structural relationships with possible properties and synthetic approaches. The proposed research targeted the synthesis of phthalocyanines containing an aromatic bridge between two phthalocyanine rings. The goal was to synthesize pigments which would protect plastics when exposed to the photodegradation effects of the sun in space. The stability and extended conjugation of the phthalocyanines offer a unique opportunity for energy absorption and numerous radiative and non-radiative energy loss mechanisms. Although the original targeted phthalocyanines were changed early in the project, several new and unique phthalocyanine compounds were prepared. The basic goals of this work were met and some unique and unexpected outcomes of the work were the result of the integral use of quantum mechanics and molecular modeling with the synthetic effort.

Vandemark, Michael R.

1992-01-01

18

Liposome technology. Volume I: Preparation of liposomes  

SciTech Connect

These three volumes cover liposome technology in pharmacology and medicine. Contributors emphasize methodology used in their own laboratories, and include a brief introduction, coverage of relevant literature, applications and critical evaluations for the methods they describe. Volume I examine methods for the preparation of liposomes and auxiliary techniques.

Gregoriadis, G.

1984-01-01

19

Phthalocyanine based Schottky solar cells  

NASA Astrophysics Data System (ADS)

Phthalocyanine (Pc) materials are commonly used in organic solar cells. Four different phthalocyanines, nickel phthalocyanine (NiPc), copper phthalocyanine (CuPc), iron phthalocyanine (FePc), and cobalt phthalocyanine (CoPc) have been investigated for organic solar cell applications. The devices consisted of indium tin oxide (ITO) coated lass substrate, Pc layer, and aluminum (al) electrode. It has been found that ITO/CuPc/Al Schottky cell exhibits the best performance. To investigate the influence of the active layer thickness on the cell performance, cells with several different thicknesses were fabricated and optimal value was found. Schottky cell exhibits optimal performance with one ohmic and one barrier contact. However, it is suspected that ITO/CuPc contact is not ohmic. Therefore, we have investigated various ITO surface treatments for improving the performance of CuPc based Schottky solar cell. We have found that cell on ITO treated with HCl and UV-ozone exhibits the best performance. AM1 power conversion efficiency can be improved by 30% compared to cell made with untreated ITO substrate. To improve power conversion efficiency, double or multiplayer structure are required, and it is expected that suitable ITO treatments for those devices will further improve their performance by improving the contact between ITO and phthalocyanine layer.

Kwong, Chung Yin; Djurisic, Aleksandra B.; Lam, Lillian S. M.; Chan, Wai Kin

2003-02-01

20

New directions in phthalocyanine pigments  

NASA Technical Reports Server (NTRS)

Phthalocyanines have been used as a pigment in coatings and related applications for many years. These pigments are some of the most stable organic pigments known. The phthalo blue and green pigments have been known to be ultraviolet (UV) stable and thermally stable to over 400 C. These phthalocyanines are both a semiconductor and photoconductor, exhibiting catalytic activity and photostabilization capability of polymers. Many metal free and metallic phthalocyanine derivatives have been prepared. Development of the new classes of phthalocyanine pigment could be used as coating on NASA spacecraft material such as glass to decrease the optical degradation from UV light, the outside of the space station modules for UV protection, and coating on solar cells to increase lifetime and efficiency.

Trinh, Diep VO

1994-01-01

21

Liposome-Incorporation of Polyenes.  

National Technical Information Service (NTIS)

The invention involves a liposomal agent for treating disseminated fungal infection in an animal. This liposomal agent comprises a variety of polyene antifungal compounds. The various polyene antifungal compounds of the liposomal agent include hamycin, lu...

G. Lopez-Berestein R. Mehta

1991-01-01

22

Monolayer-Forming Substituted Phthalocyanine Compounds.  

National Technical Information Service (NTIS)

This invention relates general to phthalocyanine compounds, and more particularly to the preparation of aryloxy, arylthio, alkyloxy, and alkylthio phthalocyanine compounds and their subsequent incorporation into semiconducting thin films by the Langmuir-B...

W. R. Barger N. L. Jarvis A. W. Snow H. Wohltjen

1985-01-01

23

Phthalocyanine cathode materials for secondary lithium cells  

SciTech Connect

Discharge and charge characteristics of various phthalocyanine cathodes coupled with lithium metal are studied. The best capacity based only on cathode active material weight is 1440 A-hr/kg in the lithium/iron phthalocyanine system, and the cycle life of the lithium/Cu phthalocyanine system is more than 100 times at the discharge depth of 157 A-hr/kg. The cathode reaction mechanism is supposed to be lithium intercalation between phthalocyanine molecules. The results indicate that these phthalocyanines are promising cathode active materials for lithium secondary batteries. 15 refs.

Yamaki, J.; Yamaji, A.

1982-01-01

24

Phthalocyanine cathode materials for secondary lithium cells  

SciTech Connect

Discharge and charge characteristics of various phthalocyanine cathodes coupled with lithium metal are studied. The best capacity based only on cathode active material weight is 1440 A-hr/kg in the lithium/iron phthalocyanine system, and the cycle life of the lithium/Cu phthalocyanine system is more than 100 times at the discharge depth of 157 A-hr/kg. The cathode reaction mechanism is supposed to be lithium intercalation between phthalocyanine molecules. The results indicate that these phthalocyanines are promising cathode active materials for lithium secondary batteries.

Tamaki, J.; Yamaji, A.

1982-01-01

25

Pharmacokinetics of liposomal gentamicin.  

PubMed

We present data on pharmacokinetics of free and liposomal forms of gentamicin. Comparative study of two drug forms showed that immobilization of gentamicin in liposomes significantly increased most important pharmacokinetic parameters of the antibiotic (AUC, Cmax, MRTpo, T(1/2), Kel, Vzpo) and reduced Clpo and Kel. PMID:22977848

Rotov, K A; Tikhonov, S N; Alekseev, V V; Snatenkov, E A

2012-08-01

26

Fused liposome and acid induced method for liposome fusion  

SciTech Connect

This patent describes a method of fusing liposomes. It comprises: preparing a suspension of liposomes containing at least one lipid which has a tendency to form the inverted hexagonal phase and at least 20 mol percent of palmitoylhomocysteine; and in the absence of externally added divalent cations, proteins or other macromolecules, acidifying the liposome suspension to reduce the pH of the liposomes to below pH 7, such that at least about 20% of the liposomes fuse to one another.

Huang, L.; Connor, J.

1988-12-06

27

Therapeutic uses of antioxidant liposomes  

Microsoft Academic Search

This review will focus on the therapeutic uses of antioxidant liposomes. Antioxidant liposomes have a unique ability to deliver\\u000a both lipid- and water-soluble antioxidants to tissues. This review will detail the varieties of antioxidants which have been\\u000a incorporated into liposomes, their modes of administration, and the clinical conditions in which antioxidant liposomes could\\u000a play an important therapeutic role. Antioxidant liposomes

William L. Stone; Milton Smith

2004-01-01

28

Liposomal spherical nucleic acids.  

PubMed

A novel class of metal-free spherical nucleic acid nanostructures was synthesized from readily available starting components. These particles consist of 30 nm liposomal cores, composed of an FDA-approved 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) lipid monomer. The surface of the liposomes was functionalized with DNA strands modified with a tocopherol tail that intercalates into the phospholipid layer of the liposomal core via hydrophobic interactions. The spherical nucleic acid architecture not only stabilizes these constructs but also facilitates cellular internalization and gene regulation in SKOV-3 cells. PMID:24983505

Banga, Resham J; Chernyak, Natalia; Narayan, Suguna P; Nguyen, SonBinh T; Mirkin, Chad A

2014-07-16

29

Synthesis of Monometallated and Unsymmetrically Substituted Binuclear Phthalocyanines and a Pentanuclear Phthalocyanine by Solution and Polymer Support Methods.  

National Technical Information Service (NTIS)

Binuclear phthalocyanines in which two different phthalocyanine nuclei are covalently linked through five-atom bridges, derived from 2-ethyl-2-methylpropan-1,3-diol are prepared. In the examples, one phthalocyanine ring is always substituted with neopento...

B. Khouw C. C. Leznoff P. Seymour P. I. Svirskaya R. L. Cerny

1990-01-01

30

Silicone-stabilized liposomes  

Microsoft Academic Search

The present work is focused on stabilization of liposomes by covering their surface with a thin silicone layer. The appropriate\\u000a silicone monomer was obtained by the hydrosilylation of vinylmethyldimethoxysilane with 1,3,5,7-tetramethylcyclotetrasiloxane.\\u000a The surface potential of egg yolk phosphatidylcholine vesicles was modified by incorporation of a cationic double-tailed surfactant,\\u000a dimethyldioctadecylammonium bromide (DODAB), yielding cationic liposomes. The silicone material was deposited on

Joanna Lewandowska; Mariusz K?pczy?ski; Jan Bednar; Ewa Rz?d; Veronika Moravcikova; Barbara Jachimska; Maria Nowakowska

2010-01-01

31

Permeability of oxidized phosphatidylcholine liposomes.  

PubMed

Permeability of liposomes made from mixtures of unoxidized and singlet oxygen oxidized phosphatidylcholine has been related to the degree of lipid oxidation expressed as hydroperoxide moiety content in the lipids. The effect of oxidation on the liposomes permeability has been studied by fluorometry using calcein as a fluorescent probe that undergoes self quenching when highly concentrated inside liposomes. The liposomes containing 73% and 5% of hydroperoxides retain respectively 64.5 and 96.3% of calcein with respect to that retained by the liposomes made from unoxidized phosphatidylcholine. The fluorescence data show a linear relationship between the liposome permeability and the oxidation degree of lipids. PMID:2775263

Tanfani, F; Bertoli, E

1989-08-30

32

Electrochromism in the octapentyloxy nickel phthalocyanines and related phthalocyanines  

Microsoft Academic Search

Reversible electrochromic behaviour has been shown to exist in the monophthalocyanine [Ni(pc(OCSH11)s)] and poor electrochromic behaviour in [Cu(pc(OCSH11)8)] and [Co(pc(OCSH11)a)], the samples having been prepared as Langmuir-Blodgett films. The latter two were deposited in semi-darkened conditions. Electrochromic behaviour was not observed in phthalocyanines of similar structure, in which there was no oxygen atom present, nor was it observed in compounds

B. Lukas; J. Silver; D. R. Lovett; M. J. Cook

1995-01-01

33

Phthalocyanines functionalized with 2-methyl-5-nitro-1H-imidazolylethoxy and 1,4,7-trioxanonyl moieties and the effect of metronidazole substitution on photocytotoxicity.  

PubMed

Four novel magnesium(II) and zinc(II) phthalocyanines bearing 1,4,7-trioxanonyl, polyether and/or (2-methyl-5-nitro-1H-imidazol-1-yl)ethoxy, heterocyclic substituents at their non-peripheral positions were synthesized and assessed in terms of physicochemical and biological properties. Magnesium phthalocyanine derivatives bearing polyether substituents (Pc-1), a mixed system of polyether and heterocyclic substituents (Pc-3), and four heterocyclic substituents (Pc-4), respectively, were synthesized following the Linstead macrocyclization reaction procedure. Zinc phthalocyanine (Pc-2) bearing polyether substituents at non-peripheral positions was synthesized following the procedure in n-pentanol with the zinc acetate, and DBU. Novel phthalocyanines were purified by flash column chromatography and characterized using NMR, MS, UV-Vis and HPLC. Moreover, two precursors in macrocyclization reaction phthalonitriles were characterized using X-ray. Photophysical properties of the novel macrocycles were evaluated, including UV-Vis spectra analysis and aggregation study. All macrocycles subjected to singlet oxygen generation and the oxidation rate constant measurements exhibited lower quantum yields of singlet oxygen generation in DMSO than in DMF. In addition, the Pc-2 molecule was found to be the most efficient singlet oxygen generator from the group of macrocycles studied. The photocytotoxicity evaluated on the human oral squamous cell carcinoma cell line, HSC-3, for Pc-3 was significantly higher than that for Pc-1, Pc-2, and Pc-4. Interestingly, Pc-3 was found to be the most active macrocycle in vitro although its ability to generate singlet oxygen was significantly lower than those of Pc-1 and Pc-2. However, attempts to encapsulate phthalocyanines Pc-1-Pc-3 in liposomal membranes were unsuccessful. The phthalocyanine-nitroimidazole conjugate, Pc-4 was encapsulated in phosphatidylglycerol:phosphatidylcholine unilamellar liposomes and subjected to photocytotoxicity study. PMID:23872453

Wierzchowski, Marcin; Sobotta, Lukasz; Skupin-Mrugalska, Paulina; Kruk, Justyna; Jusiak, Weronika; Yee, Michael; Konopka, Krystyna; Düzgüne?, Nejat; Tykarska, Ewa; Gdaniec, Maria; Mielcarek, Jadwiga; Goslinski, Tomasz

2013-10-01

34

Copper phthalocyanine nanoparticles and nanoflowers  

Microsoft Academic Search

Molecular organization of copper phthalocyanine (CuPc) thin films deposited at room temperature (30°C) on quartz and post annealed gold-coated quartz substrates have been studied. The thin films have been characterized by optical absorption, X-ray diffraction, atomic force microscopy and field emission scanning electron microscopy (FESEM). The FESEM images have shown densely packed nanoparticles and nanoflower like structure for the gold-coated

Santanu Karan; Dhrubajyoti Basak; Biswanath Mallik

2007-01-01

35

Inhaled liposomal amikacin.  

PubMed

Arikace™ is a novel formulation of inhaled liposomal amikacin that can penetrate deep within airway secretions and within Pseudomonas aeruginosa biofilms, making it an attractive therapeutic option for the treatment of cystic fibrosis (CF) pulmonary infections. Initial Phase I and Phase II studies in CF patients with chronic P. aeruginosa infection demonstrated that Arikace™ was a safe drug that resulted in significant improvements in lung function after 14-28 days of treatment. Phase III studies of inhaled liposomal amikacin compared to tobramycin inhalation solution in CF patients with P. aeruginosa infection revealed a comparable increase in forced expiratory volume in 1 second at the end of three cycles. In addition, inhaled liposomal amikacin has other potential applications in the management of difficult-to-treat pulmonary infections. A Phase II trial is currently underway to study the use of Arikace™ for the treatment of recalcitrant nontuberculous mycobacterial lung disease. PMID:24882271

Waters, Valerie; Ratjen, Felix

2014-08-01

36

[Kinetics stability of liposomes].  

PubMed

Liposomes find extensive use as drug carriers. The surface characteristics of vesicles (particle size, charge, composition, hydrophobicity etc.) and also, the kinetic stability of liposomes are all key factors for controlling fundamental carrier properties, such as the encapsulation or adsorption efficiency, the organ distribution of the carrier or the RES clearance etc. Small unilamellar (SUV) vesicles of dimyristoyl-phosphatidylcholine (DMPC) were prepared under standardized conditions. The liposomes were prepared both in the absence and the presence of an uncharged polymer [polyvinyl alcohol (PVA), polyvinyl acetal (PVA1) and polyvinyl pyrrolidone (PVP) respectively] and simultaneously, the long-term (kinetic) stability of the aqueous lipid dispersions were studied. The aggregation behavior of colloidal dispersions of DMPC liposomes were tested in physiological salt solution and polymer solutions, respectively. Particle aggregation, which may take place on storage or when the stability is lowered, are well reflected in the shift of the mean size and the distribution function towards higher values. The particle sizes, the size distribution and their change in time were measured by photon correlation spectroscopy using a Malvern ZETASIZER 4 apparatus (Malvern Instruments, UK). PMID:9082839

Grohmann, F L; Csempesz, F; Szógyi, M

1996-09-01

37

Phenylthio-substituted phthalocyanines as new photosensitizers for photodynamic therapy  

NASA Astrophysics Data System (ADS)

Current work is devoted to investigation of tetra-3-phenylthio-tetra-5-t-butylphthalocyanine [(PhS) 4(t-Bu) 4PcH II], aluminium hydroxyde tetra-3-phenylthiophthalocyanine [(PhS) 4PcAlOH] and zinc tetra-3-phenylthiophthalocyanine [(PhS) 4PcZn] as potential photosensitizers of near-infrared range. Investigations were performed on F I mice bearing Erlich tumor. Photosensitizers were administered intravenously in liposomal form at doses of 4-10 mg/kg. Dynamic and selectivity of sensitizers' accumulation in tumor were estimated in vivo from fluorescence and absorption spectra of sensitized tissue. Photosensitizers have shown high selectivity of accumulation in tumor comparing to normal tissue of mice. Maxima of selectivity for (PhS) 4(t-Bu) 4PcH II, (PhS) 4PcZn and (PhS) 4PcAlOH achieve the values up to 2.5:1, 5:1 and 8:1 respectively. All photosensitizers completely clear from the normal tissue in 7-8 days. For PDT investigations tumors were irradiated using 732 nm laser with power density of 100-500 mW/cm2 and light dose density up to 400 J/cm2. The photodynamic efficiency was estimated using the parameter of tumor growth inhibition (TGI). All photosensitizers had shown high photodynamic efficiency of relatively large tumors. PDT using (PhS) 4PcAlOH and (PhS) 4(t-Bu) 4PcH II caused pronounced TGI exceeding 80%. Using (PhS) 4PcZn caused moderate TGI of 60%. Investigations have shown that liposomal forms of phenylthiosubstituted phthalocyanine derivatives may be used to develop new efficient photosensitizers for PDT.

Meerovich, Igor G.; Derkacheva, Valentina M.; Meerovich, Gennady A.; Oborotova, Natalia A.; Smirnova, Zoya S.; Polozkova, Alevtina P.; Kubasova, Irina Yu.; Lukyanets, Evgeny A.; Baryshnikov, Anatoly Yu.

2007-02-01

38

Hexacoordinate bonding and aromaticity in silicon phthalocyanine.  

PubMed

Si-E bondings in hexacoordinate silicon phthalocyanine were analyzed using bond order (BO), energy partition, atoms in molecules (AIM), electron localization function (ELF), and localized orbital locator (LOL). Bond models were proposed to explain differences between hexacoordinate and tetracoordinate Si-E bondings. Aromaticity of silicon phthalocyanine was investigated using nucleus-independent chemical shift (NICS), harmonic oscillator model of aromaticity (HOMA), conceptual density functional theory (DFT), ring critical point (RCP) descriptors, and delocalization index (DI). Structure, energy, bonding, and aromaticity of tetracoordinate silicon phthalocyanine were studied and compared with hexacoordinate one. PMID:21105726

Yang, Yang

2010-12-23

39

Liposomes for Pulmonary Drug Delivery  

Microsoft Academic Search

\\u000a Liposomes have been widely used in pulmonary drug delivery for ­multiple applications including solubilization, sustained\\u000a release, cellular and intracellular ­targeting, minimization of toxicity, and facilitation of absorption. In this chapter,\\u000a formulation aspects, aerosolization, and an extensive overview of the use of pulmonary drug delivery of liposomes for disease\\u000a and drug classes are provided. Specifically, this chapter examines liposomes from in

Janani Swaminathan; Carsten Ehrhardt

40

Adsorption of ammonia on multilayer iron phthalocyanine  

SciTech Connect

The adsorption of ammonia on multilayers of well-ordered, flat-lying iron phthalocyanine (FePc) molecules on a Au(111) support was investigated by x-ray photoelectron spectroscopy. We find that the electron-donating ammonia molecules coordinate to the metal centers of iron phthlalocyanine. The coordination of ammonia induces changes of the electronic structure of the iron phthalocyanine layer, which, in particular, lead to a modification of the FePc valence electron spin.

Isvoranu, Cristina; Knudsen, Jan; Ataman, Evren; Andersen, Jesper N.; Schnadt, Joachim [Division of Synchrotron Radiation Research, Department of Physics, Lund University, Box 118, 221 00 Lund (Sweden); Schulte, Karina [MAX-lab, Lund University, Box 118, 221 00 Lund (Sweden); Wang Bin; Bocquet, Marie-Laure [Laboratoire de chimie, Ecole normale superieure de Lyon, 46, Allee d'Italie, 69364 Lyon Cedex 07 (France)

2011-03-21

41

Synthesis of Metal Phthalocyanine Sheet Polymers  

NASA Technical Reports Server (NTRS)

New method for synthesizing metal phthalocyanine tetracarboxylic acids (MPTCA's) yields high purity end product. In addition, high-purity metal phthalocyanine sheet polymers synthesized from compounds. Monomer formed into sheet polymer by heating. Units of polymer linked in manner similar to phenyl-group linkages in biphenyl: Conjugation extends throughout macromolecule, thereby increasing delocalization of TT-electrons. Increases conductivity and thermal stability of polymer.

Achar, B. N.; Fohlen, G. M.; Parker, J. A.

1986-01-01

42

Controlling nucleation in giant liposomes.  

PubMed

We introduce giant liposomes to investigate phase transformations in picoliter volumes. Precipitation of calcium carbonate in the confinement of DPPC liposomes leads to dramatic stabilization of amorphous calcium carbonate (ACC). In contrast, amorphous strontium carbonate (ASC) is a transient species, and BaCO3 precipitation leads directly to the formation of crystalline witherite. PMID:24728476

Tester, Chantel C; Whittaker, Michael L; Joester, Derk

2014-04-29

43

Liposome: classification, preparation, and applications  

NASA Astrophysics Data System (ADS)

Liposomes, sphere-shaped vesicles consisting of one or more phospholipid bilayers, were first described in the mid-60s. Today, they are a very useful reproduction, reagent, and tool in various scientific disciplines, including mathematics and theoretical physics, biophysics, chemistry, colloid science, biochemistry, and biology. Since then, liposomes have made their way to the market. Among several talented new drug delivery systems, liposomes characterize an advanced technology to deliver active molecules to the site of action, and at present, several formulations are in clinical use. Research on liposome technology has progressed from conventional vesicles to `second-generation liposomes', in which long-circulating liposomes are obtained by modulating the lipid composition, size, and charge of the vesicle. Liposomes with modified surfaces have also been developed using several molecules, such as glycolipids or sialic acid. This paper summarizes exclusively scalable techniques and focuses on strengths, respectively, limitations in respect to industrial applicability and regulatory requirements concerning liposomal drug formulations based on FDA and EMEA documents.

Akbarzadeh, Abolfazl; Rezaei-Sadabady, Rogaie; Davaran, Soodabeh; Joo, Sang Woo; Zarghami, Nosratollah; Hanifehpour, Younes; Samiei, Mohammad; Kouhi, Mohammad; Nejati-Koshki, Kazem

2013-02-01

44

Liposome: classification, preparation, and applications.  

PubMed

Liposomes, sphere-shaped vesicles consisting of one or more phospholipid bilayers, were first described in the mid-60s. Today, they are a very useful reproduction, reagent, and tool in various scientific disciplines, including mathematics and theoretical physics, biophysics, chemistry, colloid science, biochemistry, and biology. Since then, liposomes have made their way to the market. Among several talented new drug delivery systems, liposomes characterize an advanced technology to deliver active molecules to the site of action, and at present, several formulations are in clinical use. Research on liposome technology has progressed from conventional vesicles to 'second-generation liposomes', in which long-circulating liposomes are obtained by modulating the lipid composition, size, and charge of the vesicle. Liposomes with modified surfaces have also been developed using several molecules, such as glycolipids or sialic acid. This paper summarizes exclusively scalable techniques and focuses on strengths, respectively, limitations in respect to industrial applicability and regulatory requirements concerning liposomal drug formulations based on FDA and EMEA documents. PMID:23432972

Akbarzadeh, Abolfazl; Rezaei-Sadabady, Rogaie; Davaran, Soodabeh; Joo, Sang Woo; Zarghami, Nosratollah; Hanifehpour, Younes; Samiei, Mohammad; Kouhi, Mohammad; Nejati-Koshki, Kazem

2013-01-01

45

The challenge of liposomes in gene therapy  

Microsoft Academic Search

Summary Recently, liposomes have gained a special interest as gene delivery systems: over 30 human clinical trials for gene delivery using cationic liposomes have been approved; all these delivery methods use intratumoral, subcutaneous and other local delivery but not systemic delivery due to the toxicity of cationic lipids. Stealth liposomes (coated with polyethyleneglyc ol to camouflage the liposome and evade

Francis Martin; Teni Boulikas

1998-01-01

46

Liposomes in drug delivery: Progress and limitations  

Microsoft Academic Search

Liposomes are microparticulate lipoidal vesicles which are under extensive investigation as drug carriers for improving the delivery of therapeutic agents. Due to new developments in liposome technology, several liposome- based drug formulations are currently in clinical trial, and recently some of them have been approved for clinical use. Reformulation of drugs in liposomes has provided an opportunity to enhance the

Amarnath Sharma; Uma S. Sharma

1997-01-01

47

Structure and electrical conduction properties of phthalocyanine thin films  

Microsoft Academic Search

The structure and the dc and ac electrical conduction properties of evaporated phthalocyanine thin films are critically reviewed.Results of various structural studies on phthalocyanine single crystals and thin films performed using X-ray diffraction methods are described, and reported unit cell dimensions are given for several phthalocyanines in both the metastable ? and the stable ? forms: reported unit cell dimensions

R. D. Gould

1996-01-01

48

Assignment of the optical spectra of metal phthalocyanine anions  

SciTech Connect

Magnetic circular dichroism (MCD) spectroscopy was used to create a general band assignment scheme for main group and transition metal phthalocyanine anion species. The complexity of the overlapping absorption spectra of metal phthalocyanine anion species has been troublesome when creating models of the electronic structure of the phthalocyanine ring. The ZINDO program was used for molecular orbital calculations. 56 refs., 14 figs., 5 tabs.

Mack, J.; Stillman, M.J. [Univ. of Western Ontario, London (Canada)] [Univ. of Western Ontario, London (Canada)

1997-01-29

49

Propulsion of liposomes using bacterial motors  

NASA Astrophysics Data System (ADS)

Here we describe the utilization of flagellated bacteria as actuators to propel spherical liposomes by attaching bacteria to the liposome surface. Bacteria were stably attached to liposomes using a cross-linking antibody. The effect of the number of attached bacteria on propulsion speed was experimentally determined. The effects of bacterial propulsion on the bacteria-antibody-liposome complex were stochastic. We demonstrated that liposomal mobility increased when bacteria were attached, and the propulsion speed correlated with the number of bacteria.

Zhang, Zhenhai; Li, Zhifei; Yu, Wei; Li, Kejie; Xie, Zhihong; Shi, Zhiguo

2013-05-01

50

fullRecord:"self methylate" "self methylated" "self methylates" "self methylating" "self methylation" sulfomethylate sulfomethylated sulfomethylates sulfomethylating sulfomethylation phthalocyaninato phthalocyanine phthalocyanines tetrabenzoporphyrazine  

EPA Pesticide Factsheets

Did you mean: fullRecord:"self methylate" "self methylated" "self methylates" "self methylating" "self methylation" sulfomethylate sulfomethylated sulfomethylates sulfomethylating sulfomethylation phthalocyaninato phthalocyanine phthalocyanines tetrabenzoporphyrazine ?

51

Studies of phthalocyanine-containing polymers  

NASA Astrophysics Data System (ADS)

This thesis reports the synthesis, spectroscopic and photophysical properties, and in vitro photodynamic activities of several series of phthalocyanine-containing polymers including poly(norbornene), poly(anhydride), and poly(epsilon-caprolactone). Chapter 1 gives a general overview of phthalocyanines including their synthesis and applications. Special emphasis has been placed on hydrophilic and non-aggregated phthalocyanines and their use in photodynamic therapy. In addition, different classes of phthalocyanine-containing polymers will also be mentioned. Chapter 2 discusses the synthesis, characterization, and photophysical properties of a series of poly(norbornene)s with zinc(II) phthalocyanine and amino acid moieties. The copolymers were prepared by copolymerization of 2-(2-norbornenylmethoxy)phthalocyaninatozinc(II) with 5-norbornenes substituted with phenylalanine and tyrosine. As shown by absorption and fluorescence spectroscopy, phthalocyanines in this series of polymer exhibit a rather strong aggregation tendency. Chapter 3 presents the synthesis, characterization, photophysical properties, and in vitro photodynamic activities of a related series of amino acid- and sugar-containing poly(norbornene)s connected axially to a silicon(IV) phthalocyanine core. These polymers exhibit a good solubility in common organic solvents. Due to the axial polymeric substituents, these compounds are free from aggregation and give a high singlet oxygen quantum yield. These polymers in Cremophor EL emulsions also show a high photodynamic activity against HepG2 cells, in particular the polymer with protected galactose moieties. Chapter 4 reports a series of silicon(IV) phthalocyanines substituted with two poly(sebacic anhydride) chains as the axial ligands. The polymers form nanoparticles in water in the presence of surfactants cetyltrimethylammonium bromide (CTAB) and sodium dodecylsulphate (SDS). The degradation of the nanoparticles was carried out in alkaline media and was followed by absorption and fluorescence spectroscopy, and laser light scattering. It was found that phthalocyanines are gradually released during degradation. Chapter 5 describes the preparation, characterization, photophysical properties, and in vitro photodynamic activities of homo- and co-polymers of epsilon-caprolactone and/or 5-ethylene ketyl epsilon-caprolactone connected axially to silicon(IV) phthalocyanine. Again, these polymers are non-aggregated in solution as shown by absorption and fluorescence spectroscopy. Enzymatic degradation of the nanoparticles formed from these polymers with Lipase PS leads to a graduate release of phthalocyanines. In addition, these polymers show high in vitro photodynamic activities toward HepG2 cells, showing that this novel polymer-based colloidal system is potentially useful for the delivery and release of photosensitizers in photodynamic therapy. In addition to polymeric phthalocyanines, a series of symmetrical and unsymmetrical galactose-containing silicon(IV) phthalocyanines has also been prepared. Chapter 6 describes the preparation and properties of these novel compounds, including their in vitro photoactivity toward HepG2 cells. Appendix A gives characterizing data for all the new compounds. Crystallographic details for the X-ray structure determinations are listed in Appendix B.

Lee, Pui Sze Priscilla

52

Liposome Technology for Industrial Purposes  

PubMed Central

Liposomes, spherical vesicles consisting of one or more phospholipid bilayers, were first described in the mid 60s by Bangham and coworkers. Since then, liposomes have made their way to the market. Today, numerous lab scale but only a few large-scale techniques are available. However, a lot of these methods have serious limitations in terms of entrapment of sensitive molecules due to their exposure to mechanical and/or chemical stress. This paper summarizes exclusively scalable techniques and focuses on strengths, respectively, limitations in respect to industrial applicability. An additional point of view was taken to regulatory requirements concerning liposomal drug formulations based on FDA and EMEA documents.

Wagner, Andreas; Vorauer-Uhl, Karola

2011-01-01

53

40 CFR 721.9674 - Sulfonated-copper phthalocyanine salt of a triarylmethane dye (generic).  

Code of Federal Regulations, 2013 CFR

... 2013-07-01 false Sulfonated-copper phthalocyanine salt of a triarylmethane...Substances § 721.9674 Sulfonated-copper phthalocyanine salt of a triarylmethane...identified generically as sulfonated-copper phthalocyanine salt of a...

2013-07-01

54

40 CFR 721.9674 - Sulfonated-copper phthalocyanine salt of a triarylmethane dye (generic).  

Code of Federal Regulations, 2010 CFR

...2009-07-01 false Sulfonated-copper phthalocyanine salt of a triarylmethane dye (generic...721.9674 Sulfonated-copper phthalocyanine salt of a triarylmethane dye (generic...generically as sulfonated-copper phthalocyanine salt of a triarylmethane...

2009-07-01

55

40 CFR 721.9674 - Sulfonated-copper phthalocyanine salt of a triarylmethane dye (generic).  

Code of Federal Regulations, 2010 CFR

...false Sulfonated-copper phthalocyanine salt of a triarylmethane dye (generic...9674 Sulfonated-copper phthalocyanine salt of a triarylmethane dye (generic...generically as sulfonated-copper phthalocyanine salt of a triarylmethane dye (PMN...

2010-07-01

56

Two-photon excitation of aluminium phthalocyanines  

SciTech Connect

A demonstration is given of the feasibility of two-photon excitation of aluminium phthalocyanine and of the pharmaceutical preparation 'Fotosens', used in photodynamic therapy. The excitation source was an Nd:YAG laser emitting at the 1064 nm wavelength. The spectra of the two-photon-excited luminescence were obtained and the two-photon absorption cross sections were determined. (lasers in medicine)

Meshalkin, Yu P; Alfimov, E E; Makukha, V K [Novosibirsk State Technical University, Novosibirsk (Russian Federation); Vasil'ev, N E; Denisov, A N; Ogirenko, A P [Siberian Laser Medicine Centre, Novosibirsk (Russian Federation)

1999-12-31

57

Separation of Copper-64 from Copper Phthalocyanine.  

National Technical Information Service (NTIS)

The separation of copper-64 from irradiated copper phthalocyanine by Szilard-Chalmers effect is studied. Two methods of separation are used: one of them is based on the dissolution of the irradiated dry compound in concentrated sulfuric acid following its...

R. I. M. Battaglin

1979-01-01

58

Microwave-assisted synthesis and characterization of the monomeric phthalocyanines containing naphthalene-amide group moieties and the polymeric phthalocyanines containing oxa-aza bridge  

Microsoft Academic Search

New naphthalene-amide substituted phthalocyanines and oxa-aza bridge polymeric phthalocyanines were prepared by conventional and microwave methods. The chlorides of Cu(I), Ni(II) and Co(II) were employed in order to synthesize the corresponding metal phthalocyanines and Zn(CH3COO)2 was used for the preparation of the zinc phthalocyanines. For the preparation of the Co-containing phthalocyanines, ammonium molybdate had to be added as catalyst. In

Musa Özil; Erbil A?ar; Selami ?a?maz; Bahittin Kahveci; Nesuhi Akdemir; ?smail Erdem Gümrükçüo?lu

2007-01-01

59

Characterization of Liposomes for Cancer Cell Transfection  

PubMed Central

We have characterized a broad range of liposome formulations with varying DcChol:DOPE ratio. Subsequent addition of DcChol to liposomes increases its positive surface charge. However, loading the nuclear acids did not neutralize the overall negative surface potential to a similar extent. The liposomes were tested by transfection of DNA in living cancer cells.

Tatarkova, Svetlana A; Khaira, Satvinder

2007-01-01

60

Sequestration of amitriptyline by liposomes.  

PubMed

We study the uptake of amitriptyline, which is a common cause of overdose-related fatalities, in aqueous solutions by 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) liposomes and liposomes composed of a mixture of DMPC and 1,2-dioleoyl-sn-glycero-3-[phospho-rac(1-glycerol)] (DOPG) lipids. The effect of drug concentration, liposomal charge, pH, salt, and protein presence on the drug uptake is investigated using two different methodologies, a precipitation and a centrifugation method. Furthermore, the time scale of the drug uptake is studied through qualitative observations at high pH and through conductivity measurements at neutral pH and found to be <5 s. The results of the quantitative studies show that the fractional drug uptake decreases with increasing drug concentration, and for a given concentration it increases with the pH and decreases in the presence of salt. We find that a larger amount of drug is sequestered by negatively charged liposomes (those containing DOPG) than liposomes with no net charge (DMPC). We speculate that the mechanism of drug uptake is due to both electrostatic interactions as well as hydrophobic effects. The fractional uptake by DMPC:DOPG in a 70:30 ratio is as high as 95% in water and about 90% in physiological buffer. The fractional uptake is also measured in presence of 2% (w/w) bovine serum albumin (BSA), which is approximately the protein concentration in the intercellular fluid. In presence of protein the fractional uptakes by 70:30 DMPC:DOPG liposomes and 50:50 DMPC:DOPG liposomes are 82 and 90%, respectively, at 125 muM drug amitriptyline. In the absence of liposomes, 67% of the drug is taken up by the protein in a 2% (w/w) BSA, 125 muM amitriptyline solution. Thus, addition of 50:50 DMPC:DOPG liposomes reduces the free drug concentration by a factor of about 3.5, making them attractive candidates for drug detoxification. PMID:16643936

Fallon, Marissa S; Chauhan, Anuj

2006-08-01

61

Liposomes for cryopreservation of bovine sperm.  

PubMed

In this study, the effect of various unilamellar liposomes on cryopreservation of bovine spermatozoa has been investigated. Liposomes were composed of saturated lipids with various acyl chain lengths: DSPC (18:0), DPPC (16:0), DMPC (14:0), or DLPC (12:0). Alternatively, liposomes were prepared using unsaturated egg phosphatidylcholine (EPC) or DOPC (18:1, neutral), alone or in combination with lipids with various head groups: DOPS (negatively charged), DOPG (negatively charged), and DOPE (neutral). Fourier transform infrared spectroscopy studies showed that bovine sperm membranes display a gradual phase transition from 10 to 24 (o)C. Phase transition temperatures of the liposomes varied from -20 to +53 (o)C. Sperm was incubated in the presence of liposomes for either 6 or 24 h at 4 °C prior to freezing. Postfreeze survival rates were determined based on the percentage of progressively motile cells as well as the percentage of acrosome- and plasma membrane-intact cells. With DOPC liposomes a postthaw progressive motility of 43% was obtained compared with 59% using standard egg yolk freezing extender. Postthaw progressive motility increased up to 52% using DOPC:DOPG (9:1) liposomes, whereas DOPC:DOPS or DOPC:DOPE liposomes did not increase survival compared with DOPC liposomes. Among the saturated lipids, only DMPC was found to increase cryosurvival, up to 44% based on progressive motility. DLPC liposomes caused a complete loss in cell viability, already prior to freezing, whereas DPPC and DSPC liposomes neither positively nor negatively affected cryosurvival. Taken together, the higher postthaw survival obtained with DOPC:DOPG liposomes as compared with DOPC liposomes can likely be attributed to increased liposome-sperm interactions between the charged phosphatidylglycerol groups and charged regions in the sperm membranes. Interestingly, the lipid phase state of the liposomes during preincubation is not the decisive factor for their cryoprotective action. PMID:21820724

Röpke, T; Oldenhof, H; Leiding, C; Sieme, H; Bollwein, H; Wolkers, W F

2011-11-01

62

Capabilities of liposomes for topological transformation.  

PubMed

Dynamic behaviors of liposomes caused by interactions between liposomal membranes and surfactant were studied by direct real-time observation by using high-intensity dark-field microscopy. Solubilization of liposomes by surfactants is thought to be a catastrophic event akin to the explosion of soap bubbles in the air; however, the actual process has not been clarified. We studied this process experimentally and found that liposomes exposed to various surfactants exhibited unusual behavior, namely continuous shrinkage accompanied by intermittent quakes, release of encapsulated liposomes, opening up, and inside-out topological inversion. PMID:11226241

Nomura, F; Nagata, M; Inaba, T; Hiramatsu, H; Hotani, H; Takiguchi, K

2001-02-27

63

Cationic liposomes for gene delivery.  

PubMed

Cationic liposome-DNA complexes (lipoplexes) constitute a potentially viable alternative to viral vectors for the delivery of therapeutic genes. This review will focus on various parameters governing lipoplex biological activity, from their mode of formation to in vivo behaviour. Particular emphasis is given to the mechanism of interaction of lipoplexes with cells, in an attempt to dissect the different barriers that need to be surpassed for efficient gene expression to occur. Aspects related to new trends in the formulation of lipid-based gene delivery systems aiming at overcoming some of their limitations will be covered. Finally, examples illustrating the potential of cationic liposomes in clinical applications will be provided. PMID:16296751

Simões, Sérgio; Filipe, Ana; Faneca, Henrique; Mano, Miguel; Penacho, Nuno; Düzgünes, Nejat; de Lima, Maria Pedroso

2005-03-01

64

Redox-Triggered Contents Release from Liposomes  

PubMed Central

An exciting new direction in responsive liposome research is endogenous triggering of liposomal payload release by overexpressed enzyme activity in affected tissues and offers the unique possibility of active and site-specific release. Bringing to fruition the fully expected capabilities of this new class of triggered liposomal delivery system requires a collection of liposome systems that respond to different upregulated enzymes; however, a relatively small number currently exist. Here we show that stable, ~100 nm diameter liposomes can be made from previously unreported quinone-dioleoyl phosphatidylethanolamine (Q-DOPE) lipids, and complete payload release (quenched fluorescent dye) from Q-DOPE liposomes occurs upon their redox activation when the quinone headgroup possesses specific substituents. The key component of the triggerable, contents-releasing Q-DOPE liposomes is a “trimethyl-locked” quinone redox switch attached to the N-terminus of DOPE lipids that undergoes a cleavage event upon two-electron reduction. Payload release by aggregation and leakage of “uncapped” Q-DOPE liposomes is supported by results from liposomes wherein deliberate alteration of the “trimethyl-locked” switch completely deactivates the redox-destructible phenomena (liposome opening). We expect that Q-DOPE liposomes and their variants will be important in treatment of diseases with associated tissues that overexpress quinone reductases, such as cancers and inflammatory diseases, because the quinone redox switch is a known substrate for this group of reductases.

Ong, Winston; Yang, Yuming; Cruciano, Angela C.; McCarley*, Robin L.

2008-01-01

65

Redox-triggered contents release from liposomes.  

PubMed

An exciting new direction in responsive liposome research is endogenous triggering of liposomal payload release by overexpressed enzyme activity in affected tissues and offers the unique possibility of active and site-specific release. Bringing to fruition the fully expected capabilities of this new class of triggered liposomal delivery system requires a collection of liposome systems that respond to different upregulated enzymes; however, a relatively small number currently exist. Here we show that stable, approximately 100 nm diameter liposomes can be made from previously unreported quinone-dioleoyl phosphatidylethanolamine (Q-DOPE) lipids, and complete payload release (quenched fluorescent dye) from Q-DOPE liposomes occurs upon their redox activation when the quinone headgroup possesses specific substituents. The key component of the triggerable, contents-releasing Q-DOPE liposomes is a "trimethyl-locked" quinone redox switch attached to the N-terminus of DOPE lipids that undergoes a cleavage event upon two-electron reduction. Payload release by aggregation and leakage of "uncapped" Q-DOPE liposomes is supported by results from liposomes wherein deliberate alteration of the "trimethyl-locked" switch completely deactivates the redox-destructible phenomena (liposome opening). We expect that Q-DOPE liposomes and their variants will be important in treatment of diseases with associated tissues that overexpress quinone reductases, such as cancers and inflammatory diseases, because the quinone redox switch is a known substrate for this group of reductases. PMID:18841890

Ong, Winston; Yang, Yuming; Cruciano, Angela C; McCarley, Robin L

2008-11-01

66

Thin films of ruthenium phthalocyanine complexes  

Microsoft Academic Search

Four new ruthenium phthalocyanine complexes bearing axial ligands with thioacetate groups that facilitate thin film formation\\u000a on gold surfaces are presented. Scanning tunnelling microscopy (STM) images and surface coverage data obtained by solution\\u000a inductively coupled plasma mass spectrometry (ICP-MS) experiments show that peripheral and axial ligand substituents on the\\u000a complexes have a significant effect on their surface coverage. A laser

Tristan Rawling; Christine E. Austin; Dominic Hare; Philip A. Doble; Hadi M. Zareie; Andrew M. McDonagh

2009-01-01

67

Scanning tunneling microscopy of metal phthalocyanines  

NASA Astrophysics Data System (ADS)

Scanning tunneling microscopy (STM) images of cobalt(II) phthalocyanine (CoPc), copper(II) phthalocyanine (CuPc), iron(II) phthalocyanine (FePc), and nickel(II) phthalocyanine (NiPc) adsorbed on the Au(111) surface are reported. These species provide images showing sub-molecular structure. A particularly exciting aspect of this work is the strong influence of the metal ion valence configuration on the observed tunneling images. Unlike CuPc and NiPc, wherein the central metal appears as a hole in the molecular image, the cobalt ion in CoPc and iron ion in FePc are the highest points (about 0.25 nm) in the molecular images. These data are interpreted as indicating that the Co(II) dsp7 and Fe(II) dsp6 systems have significant d-orbital character near the Fermi energy while the Cu(II) dsp9 and Ni(II) dsp8 systems do not. This interpretation is consistent with theoretical calculations that predict a large contribution of cobalt and iron d-orbitals near the Fermi energy. An intriguing aspect of this work is that it may be possible to chemically identify different metal complexes simply by their appearance. Metal-organic complex systems of this type may also be viewed as single molecular electronic structures with different parts of the same molecule behaving as insulator, conductor, or semiconductor. A commercial Digital Instruments NanoScope III controller was used with a McAllister Technical UHV STM. Modifications of the preamp, cabling, and coarse approach mechanism were required to achieve satisfactory operation, and these changes are described. Also included are detailed instructions for tip fabrication and final (UHV) electron bombardment cleaning.

Lu, Xing (Bill)

68

Phthalocyanine Tetraamine Epoxy-Curing Agents  

NASA Technical Reports Server (NTRS)

Tough fire- and chemical-resistant epoxies produced by using metalphthalocyanine tetraamines (MPT's) of copper, cobalt, or nickel as curing agents. Synthesis of MPT's commercially realizable and gives pure compounds with almost 90-percent yield. Synthesis applicable for metals with atomic radii of about 1.35 angstroms, including Cu, Co, Ni, Zn, Fe, Pt, Al, and V. Possible to use metal phthalocyanines to cure epoxy resins in homogeneous reaction.

Fohlen, G. M.; Achar, B. N.; Parker, J. A.

1986-01-01

69

Surface fractals in liposome aggregation  

Microsoft Academic Search

In this work, the aggregation of charged liposomes induced by magnesium is investigated. Static and dynamic light scattering, Fourier-transform infrared spectroscopy, and cryotransmission electron microscopy are used as experimental techniques. In particular, multiple intracluster scattering is reduced to a negligible amount using a cross-correlation light scattering scheme. The analysis of the cluster structure, probed by means of static light scattering,

Sándalo Roldán-Vargas; Ramon Barnadas-Rodríguez; Manuel Quesada-Pérez; Joan Estelrich; José Callejas-Fernández

2009-01-01

70

Charge-carrier photogeneration in doped metal-free phthalocyanine  

NASA Astrophysics Data System (ADS)

Photoconductivity and electric-field-induced fluorescence quenching measurements on X-metal-free phthalocyanine photovoItaic cells show that doping with metal—phthalocyanines can both increase charge-carrier photogeneralion and decrease cell resistance. Charge-carrier photogeneration appears to be extrinsic, involving field-assisted exciplex dissociation.

Menzel, E. Roland; Loutfy, Rafik O.

1980-06-01

71

Liposomes as carriers of imaging agents  

SciTech Connect

This review discusses the utilization of liposomes as imaging agents or as vehicles for contrast materials. The initial approach was the use of radiolabeled liposomes for scintigraphy. To this end liposomes were either labeled in the lipid membrane or aqueous radiotracers were incorporated inside the lipid vesicles. The lipid labeling provides a more stable association of the radioactive tracer and the lipid vesicles, while the use of water-soluble radiotracers provides a wider selection of compounds. Early attempts at selective tumor imaging using radiolabeled liposomes were unsuccessful. The use of monoclonal antibodies attached to liposomes offers new hopes. Several strategies have been proposed in this respect and several others can be envisioned. The use of liposomes permits the use of several administration routes for imaging agents. Of particular interest is the subcutaneous administration for lymph node visualization. Liposomes offer clear advantages over most radiocontrast agents for prolonged hepatosplenic contrast enhancement. This is particularly relevant in the diagnostic evaluation of the abdomen with computed tomography. Important research efforts are being conducted in this area. Two different approaches have been advanced: the incorporation of contrast agents into liposomes and the preparation of radiopaque liposomes from radiodense lipids. Nuclear magnetic resonance imaging can also benefit from contrast agents. Several centers are investigating this exciting field using liposomes loaded with paramagnetic elements.152 references.

Caride, V.J.

1985-01-01

72

Opening-Up of Liposomal Membranes by Talin  

Microsoft Academic Search

Morphological changes of liposomes caused by interactions between liposomal membranes and talin, a cytoskeletal submembranous protein, were studied by direct, real-time observation by using high-intensity dark-field microscopy. Surprisingly, when talin was added to a liposome solution, liposomes opened stable holes and were transformed into cup-shaped liposomes. The holes became larger with increasing talin concentration, and finally the cup-shaped liposomes were

Akihiko Saitoh; Kingo Takiguchi; Yohko Tanaka; Hirokazu Hotani

1998-01-01

73

Liposomes for cryopreservation of bovine sperm  

Microsoft Academic Search

In this study, the effect of various unilamellar liposomes on cryopreservation of bovine spermatozoa has been investigated. Liposomes were composed of saturated lipids with various acyl chain lengths: DSPC (18:0), DPPC (16:0), DMPC (14:0), or DLPC (12:0). Alternatively, liposomes were prepared using unsaturated egg phosphatidylcholine (EPC) or DOPC (18:1, neutral), alone or in combination with lipids with various head groups:

T. Röpke; H. Oldenhof; C. Leiding; H. Sieme; H. Bollwein; W. F. Wolkers

2011-01-01

74

Novel axially disubstituted non-aggregated silicon phthalocyanines  

NASA Astrophysics Data System (ADS)

This paper describes the synthesis, spectroscopic characterization of a range of new axially-disubstituted silicon phthalocyanines with 2-[2-(dimethylamino)ethoxy] or 2-[2-(1,4,7,10,13-pentaoxa-16-azacyclooctadecan-16-yl)ethoxy] groups as axial ligands. 2-[2-(Dimethylamino)ethoxy]ethanol 2, 2-[2-(1,4,7,10,13-pentaoxa-16-azacyclooctadecan-16-yl)ethoxy]ethanol 4 are reacted with silicon phthalocyanine 1, to give an axially-disubstituted silicon phthalocyanines 3 and 5. Axially-disubstituted silicon phthalocyanine complexes were synthesized at the first time. Newly synthesized silicon phthalocyanines were characterized by UV-Vis, IR, 1H NMR, 13C NMR spectroscopy, ESI mass spectrometry. These new silicon(IV) phthalocyanines 3 and 5 showed excellent solubility in organic solvents such as CHCl3, CH2Cl2, acetone, DMF, DMSO, THF, EtOAc. The aggregation behavior of these compounds were investigated in different concentrations of DMSO. The effect of solvents on absorption spectra were studied in various organic solvents. The thermal stabilities of the silicon(IV) phthalocyanines 3 and 5 were determined by thermogravimetric analysis.

B?y?kl?o?lu, Zekeriya; Çak?r, Dilek

2012-12-01

75

Synthesis and photophysical properties of lead phthalocyanines  

Microsoft Academic Search

This work reports on the synthesis and photophysical parameters of tetra-and octa-substituted new lead phthalocyanines. The complexes synthesized are: 1,4-(tetraphenoxyphthalocyaninato)lead (7a), 1,4-(tetra-tert-butylphenoxyphthalocyaninato)lead (7b), 2,3-(tetraphenoxyphthalocyaninato)lead (8a), 2,3-(tetra-tert-butylphenoxyphthalocyaninato)lead (8b), 2,3-octaphenoxyphthalocyaninatolead (9a) 2,3-[octakis(4-t-butylphenoxyphthalocyaninato)]lead (9b). Photophysical properties were studied for these complexes in a dimethylsulfoxide, dimethylformamide, toluene, tetrahydrofuran and chloroform. The fluorescence spectra were different from excitation spectra due to demetallation upon excitation. High

Desmond Kwena Modibane; Tebello Nyokong

2008-01-01

76

Synthesis and electrochemical properties of phthalocyanine--fullerene hybrids  

PubMed

Phthalocyanines linked to C60 have been synthesized by two general strategies. One of them involves the addition of an azomethine ylide prepared in situ from a formyl phthalocyanine to C60, and the other one involves a statistical condensation of two substituted phthalonitriles, one of them bearing the C60 moiety covalently attached. These new phthalocyanine-fullerene dyads have been studied by cyclic voltammetry and Osteryoung square wave voltammetry, and inter- and intramolecular electronic interactions between the two electroactive subunits have been demonstrated. PMID:11072826

Gouloumis; Liu; Sastre; Vazquez; Echegoyen; Torres

2000-10-01

77

BIOPHARMACEUTICS OF LIPOSOMAL INTERLEUKIN 2, ONCOLIPIN  

Microsoft Academic Search

Oncolipin is a multilamellar liposomal (dimyristoyl phosphatidylcholine) formulation of interleukin 2 (IL-2) and human serum albumin (HSA) with distinct surface characteristics which may influence its biological activities. IL-2 and HSA were detected on the surface of the liposomes using specific antibody staining. Surface expression of IL-2 was also demonstrated by the observation that Oncolipin bound to cells expressing IL-2 receptors

Mary E Neville; Lawrence T Boni; Laura E Pflug; Mircea C Popescu; Richard J Robb

2000-01-01

78

Liposomal nanocapsules in food science and agriculture.  

PubMed

Liposomes, spherical bilayer vesicles from dispersion of polar lipids in aqueous solvents, have been widely studied for their ability to act as drug delivery vehicles by shielding reactive or sensitive compounds prior to release. Liposome entrapment has been shown to stabilize encapsulated, bioactive materials against a range of environmental and chemical changes, including enzymatic and chemical modification, as well as buffering against extreme pH, temperature, and ionic strength changes. Liposomes have been especially useful to researchers in studies of various physiological processes as models of biological membranes in both eukaryotes and prokaryotes. Industrial applications include encapsulation of pharmaceuticals and therapeutics, cosmetics, anti-cancer and gene therapy drugs. In the food industry, liposomes have been used to deliver food flavors and nutrients and more recently have been investigated for their ability to incorporate food antimicrobials that could aid in the protection of food products against growth of spoilage and pathogenic microorganisms. In this review we briefly introduce key physicochemical properties of liposomes and review competing methods for liposome production. A survey of non-agricultural and food applications of liposomes are given. Finally, a detailed up-to-date summary of the emerging usage of liposomes in the food industry as delivery vehicles of nutrients, nutraceuticals, food additives, and food antimicrobials is provided. PMID:16371329

Taylor, T Matthew; Davidson, P Michael; Bruce, Barry D; Weiss, Jochen

2005-01-01

79

Liposome retention in size exclusion chromatography  

PubMed Central

Background Size exclusion chromatography is the method of choice for separating free from liposome-encapsulated molecules. However, if the column is not presaturated with lipids this type of chromatography causes a significant loss of lipid material. To date, the mechanism of lipid retention is poorly understood. It has been speculated that lipid binds to the column material or the entire liposome is entrapped inside the void. Results Here we show that intact liposomes and their contents are retained in the exclusion gel. Retention depends on the pore size, the smaller the pores, the higher the retention. Retained liposomes are not tightly fixed to the beads and are slowly released from the gels upon direct or inverted eluent flow, long washing steps or column repacking. Further addition of free liposomes leads to the elution of part of the gel-trapped liposomes, showing that the retention is transitory. Trapping reversibility should be related to a mechanism of partitioning of the liposomes between the stationary phase, water-swelled polymeric gel, and the mobile aqueous phase. Conclusion Retention of liposomes by size exclusion gels is a dynamic and reversible process, which should be accounted for to control lipid loss and sample contamination during chromatography.

Ruysschaert, Tristan; Marque, Audrey; Duteyrat, Jean-Luc; Lesieur, Sylviane; Winterhalter, Mathias; Fournier, Didier

2005-01-01

80

Liposomal Nanocapsules in Food Science and Agriculture  

Microsoft Academic Search

Liposomes, spherical bilayer vesicles from dispersion of polar lipids in aqueous solvents, have been widely studied for their ability to act as drug delivery vehicles by shielding reactive or sensitive compounds prior to release. Liposome entrapment has been shown to stabilize encapsulated, bioactive materials against a range of environmental and chemical changes, including enzymatic and chemical modification, as well as

T. Matthew Taylor; Jochen Weiss; P. Michael Davidson; Barry D. Bruce

2005-01-01

81

Highly Conductive Copper Phthalocyanine-Carbon Plack Mixtures  

Microsoft Academic Search

Data on electrical behaviour of copper phthalocyanine-carbon black mixtures are presented. Por some samples the transition between semiconducting and metallic states is observed. The conductivity of the mixtures is found to be dependent on carbon black grain size.

Marek Kulesza; Maria Zabkowska; Witold Waciawek

1985-01-01

82

Molecular aggregation in soluble phthalocyanines - Chemical interactions vs. ?-stacking  

NASA Astrophysics Data System (ADS)

Aggregation of soluble sulfonated phthalocyanines (Pcs) containing di- and trivalent central atoms in binary water-alcohol solvents has been studied. The equilibrium constants of dimerization in solutions of Pcs with divalent central atoms (Zn, Cu) were found dependent on the electrical permittivity of the solvent and on the degree of sulfonation (i.e., on the charge on the phthalocyanine anions). Our results show that in Pcs with the trivalent central atom (Al(OH)) the dimerization occurs preferentially by formation of oxygen bridges or hydrogen bonds. Disulfonated aluminum phthalocyanine anions dissolved in water-rich binary solvents seem to form both ?-stacked dimers and chemical dimers, due to a decrease in the Coulombic repulsive energy. The experiments reported in the paper indicate that the aggregation of soluble phthalocyanines can be controlled by the choice of a suitable electric permittivity of the solvent.

Palewska, Krystyna; Sworakowski, Juliusz; Lipi?ski, Józef

2012-08-01

83

Serum albumin as a vehicle for zinc phthalocyanine: photodynamic activities in solid tumour models.  

PubMed Central

Zinc phthalocyanine (ZnPc) is a second-generation photosensitiser for the photodynamic therapy (PDT) of cancer. Unsubstituted ZnPc is, however, highly insoluble in most common solvents, and for clinical applications the material needs to be incorporated in liposomes. We report a simple, alternative procedure to formulate ZnPc through non-covalent binding to bovine serum albumin (BSA). Intravenous administration of ZnPc-BSA preparations, at a molar ratio of 11:1 and at a ZnPc dose equivalent to 0.5 mol kg-1, to tumour-bearing mice followed 24 h later by PDT was shown to provide tumour control in two different models, the EMT-6 tumour in Balb/c mice and the human colon T380 carcinoma in nude mice. Analysis of serum fractions from treated animals showed that ZnPc readily redistributes over the serum high-density lipoprotein (HDL) fraction. We also demonstrated the absence of hepatic toxicity of the ZnPc-BSA preparation by monitoring the hepatic cytochrome P450 activity in treated animals and the viability of human cultured hepatocytes.

Larroque, C.; Pelegrin, A.; Van Lier, J. E.

1996-01-01

84

Photodynamic pathogen inactivation in red cell concentrates with the silicon phthalocyanine Pc 4  

NASA Astrophysics Data System (ADS)

The silicon phthalocyanine Pc 4, a photosensitizer activated with red light, has been studied for pathogen inactivation in red blood cell concentrates (RBCC). Pc 4 targets the envelope of pathogenic viruses such as HIV. To protect RBC during the process two main approaches are used: 1) Inclusion of quenches of reactive oxygen species produced during treatment. Tocopherol succinate was found to be most effective for this purpose. 2) Formulation of Pc 4, a lipophilic compound, in liposomes that reduce its binding to RBC but not to viruses. As a light source we used a light emitting diode array emitting at 660-680 nm. An efficient mixing device ensures homogeneous light exposure during treatment of intact RBCC. Treatment of RBCC with 5 (mu) M Pc 4 a d light results in the inactivation of >= 5.5 log10 HIV, >= 6.6 log10 VSV, and >= 5 log10 of PRV and BVDV. Parasites that can be transmitted by blood transfusion are even more sensitive than viruses. Following treatment, RBCC can be stored for 28 days at 4 degrees C with hemolysis below 1 percent. Baboon RBC circulate with an acceptable 24 hour recovery and half-life. Genetic toxicological studies of Pc 4 with or without light exposure are negative. We conclude that a process using Pc 4 and red light can potentially reduce the risk of transmitting pathogens in RBCC used for transfusion.

Ben-Hur, Ehud; Chan, Wai-Shun; Yim, Zachary; Zuk, Maria M.; Dayal, Vinay; Roth, Nathan; Heldman, Eli; Lazlo, A.; Valeri, C. R.; Horowitz, Bernard

2000-03-01

85

Synthesis and characterization of di-disubstituted phthalocyanines  

Microsoft Academic Search

An improved approach to the synthesis of di-disubstituted phthalocyanines from two different phthalyl precursors is described. The method combines substituted 1,3 diiminoisoindoles and 6\\/7-nitro-1,3,3-trichloroisoindolenine to synthesize phthalocyanine. The method can be applied to the synthesis of hydrogen and metallo phtahlocyanine. The yields are variable, ranging from 17% to 72% depending on the substituents.

Joseph G. Young; William Onyebuagu

1990-01-01

86

Characterization of zinc phthalocyanine (ZnPc) for photovoltaic applications  

Microsoft Academic Search

Zinc phthalocyanine (ZnPc) is a promising candidate for solar-cell applications, because it is easily synthesized and is non-toxic to the environment. Recently, phthalocyanine (Pc) was considered by many researchers as the active part in all-organic solar cells, i.e. plastic solar cells. It is a self-assembling liquid crystal developed from a common deep-blue-green pigment. It exhibits a characteristic structural self-organization, which

S. Senthilarasu; S. Velumani; R. Sathyamoorthy; A. Subbarayan; J. A. Ascencio; G. Canizal; P. J. Sebastian; J. A. Chavez; R. Perez

2003-01-01

87

Liposome fusion and lipid exchange on ultraviolet irradiation of liposomes containing a photochromic phospholipid.  

PubMed

A photochromic phospholipid, 1,2-bis[4-4(4-n-butylphenylazo) phenylbutyroyl] phosphatidylcholine (Bis-Azo PC) has been incorporated into liposomes of gel- and liquid-crystalline- phase phospholipids. Liposomes of gel-phase phospholipid are stable in the presence of the trans photostationary state Bis-Azo PC and can encapsulate fluorescent marker dye. On photoisomerization to the cis photostationary state, trapped marker is rapidly released. Liposomes containing Bis-Azo PC can rapidly fuse together after UV isomerization, this process continuing in the dark. Exposure to white light causes reversion of Bis-Azo Pc to the trans form and halts dye leakage and vesicle fusion. Both unilamellar and multilamellar liposomes are able to fuse together on UV exposure. On UV photolysis, liposomes containing Bis-Azo PC do not fuse with a large excess of unlabeled liposomes, but transfer of Bis-Azo PC can be demonstrated spectrophotometrically. Vesicles of pure gel-phase lipid containing trapped marker dye but initially no Bis-Azo PC become leaky as a result of this lipid transfer. Liposomes composed of liquid-crystalline-phase phosphatidylcholine- containing Bis-Azo PC neither leak trapped marker no fuse together on photolysis, nor do liquid-crystalline-phase liposomes fuse with gel-phase liposomes under these conditions. These results are discussed together with some possible applications of liposome photodestabilization. PMID:7638269

Morgan, C G; Yianni, Y P; Sandhu, S S; Mitchell, A C

1995-07-01

88

Electrostatically driven complexation of liposomes with a star-shaped polyelectrolyte to low-toxicity multi-liposomal assemblies.  

PubMed

Anionic liposomes are electrostatically complexed to a star-shaped cationic polyelectrolyte. Upon complexation, the liposomes retain their integrity and the resulting liposome-star complexes do not dissociate in a physiological solution with 0.15?M NaCl. This provides a multi-liposomal container for possible use as a high-capacity carrier. PMID:24243764

Yaroslavov, Alexander A; Sybachin, Andrey V; Zaborova, Olga V; Pergushov, Dmitry V; Zezin, Alexander B; Melik-Nubarov, Nikolay S; Plamper, Felix A; Müller, Axel H E; Menger, Frederic M

2014-04-01

89

Vibrational studies of molecular organization in evaporated phthalocyanine thin solid films  

SciTech Connect

This report presents results on the study of the molecular organization, utilizing transmission and reflection absorption FTIR spectroscopy, of thin films of phthalocyanine complexes and metal free phthalocyanine. The spatial anisotropy was probed.

Aroca, R.; Thedchanamoorthy, A. [Univ. of Windsor (Canada)

1995-01-01

90

Helicobacter pylori TlyA Agglutinates Liposomes and Induces Fusion and Permeabilization of the Liposome Membranes.  

PubMed

Helicobacter pylori TlyA is a pore-forming hemolysin with potent cytotoxic activity. To explore the potential membrane-damaging activity of H. pylori TlyA, we have studied its interaction with the synthetic liposome vesicles. In our study, H. pylori TlyA shows a prominent ability to associate with the liposome vesicles without displaying an obligatory requirement for any protein receptor on the liposome membranes. Interaction of TlyA triggers agglutination of the liposome vesicles. Such agglutinating activity of TlyA could also be observed with erythrocytes before the induction of its pore-forming hemolytic activity. In addition to its agglutinating activity against liposomes, TlyA also induces fusion and disruption of the liposome membranes. Altogether, our study highlights novel membrane-damaging properties of H. pylori TlyA that have not been documented previously with any other TlyA family protein. PMID:24846696

Lata, Kusum; Chattopadhyay, Kausik

2014-06-10

91

Liposomes in Double-Emulsion Globules  

PubMed Central

Tubular liposomes containing a hydrophilic model compound (fluorescein sodium salt, FSS) were entrapped inside the internal aqueous phase (W1) of water-in-oil-in-water (W1/O/W2) double-emulsion globules. Our hypothesis was that the oil membrane of double emulsions can function as a layer of protection to liposomes and their contents and thus better control their release. Liposomes were prepared in bulk, and their release was observed microscopically from individual double-emulsion globules. The liposomes containing FSS were released through external coalescence, and the behavior of this system was monitored visually by capillary video microscopy. Double-emulsion globules were stabilized with Tween 80 as the water-soluble surfactant, with Span 80 as the oil-soluble surfactant, while the oil phase (O) was n-hexadecane. The lipids in the tubular liposomes consist of l-?-phosphatidylcholine and Ceramide-VI. Variations of Tween 80 concentration in the external aqueous phase (W2) and Span 80 concentration in the O phase controlled the release of liposomes from the W1 phase to the W2 phase. The major finding of this work is that the sheer presence of liposomes in the W1 phase is by itself a stabilizing factor for double-emulsion globules.

Wang, Qing; Tan, Grace; Lawson, Louise B.; John, Vijay T.; Papadopoulos, Kyriakos D.

2010-01-01

92

Liposomes in double-emulsion globules.  

PubMed

Tubular liposomes containing a hydrophilic model compound (fluorescein sodium salt, FSS) were entrapped inside the internal aqueous phase (W(1)) of water-in-oil-in-water (W(1)/O/W(2)) double-emulsion globules. Our hypothesis was that the oil membrane of double emulsions can function as a layer of protection to liposomes and their contents and thus better control their release. Liposomes were prepared in bulk, and their release was observed microscopically from individual double-emulsion globules. The liposomes containing FSS were released through external coalescence, and the behavior of this system was monitored visually by capillary video microscopy. Double-emulsion globules were stabilized with Tween 80 as the water-soluble surfactant, with Span 80 as the oil-soluble surfactant, while the oil phase (O) was n-hexadecane. The lipids in the tubular liposomes consist of L-alpha-phosphatidylcholine and Ceramide-VI. Variations of Tween 80 concentration in the external aqueous phase (W(2)) and Span 80 concentration in the O phase controlled the release of liposomes from the W(1) phase to the W(2) phase. The major finding of this work is that the sheer presence of liposomes in the W(1) phase is by itself a stabilizing factor for double-emulsion globules. PMID:19958007

Wang, Qing; Tan, Grace; Lawson, Louise B; John, Vijay T; Papadopoulos, Kyriakos D

2010-03-01

93

Quantifying the effects of melittin on liposomes.  

PubMed

Melittin, the soluble peptide of bee venom, has been demonstrated to induce lysis of phospholipid liposomes. We have investigated the dependence of the lytic activity of melittin on lipid composition. The lysis of liposomes, measured by following their mass and dimensions when immobilised on a solid substrate, was close to zero when the negatively charged lipids phosphatidyl glycerol or phosphatidyl serine were used as the phospholipid component of the liposome. Whilst there was significant binding of melittin to the liposomes, there was little net change in their diameter with melittin binding reversed upon salt injection. For the zwitterionic phosphatidyl choline the lytic ability of melittin is dependent on the degree of acyl chain unsaturation, with melittin able to induce lysis of liposomes in the liquid crystalline state, whilst those in the gel state showed strong resistance to lysis. By directly measuring the dimensions and mass changes of liposomes on exposure to melittin using Dual Polarisation Interferometry, rather than following the florescence of entrapped dyes we attained further information about the initial stages of melittin binding to liposomes. PMID:17092481

Popplewell, J F; Swann, M J; Freeman, N J; McDonnell, C; Ford, R C

2007-01-01

94

The Role of Cavitation in Liposome Formation  

PubMed Central

Liposome size is a vital parameter of many quantitative biophysical studies. Sonication, or exposure to ultrasound, is used widely to manufacture artificial liposomes, yet little is known about the mechanism by which liposomes are affected by ultrasound. Cavitation, or the oscillation of small gas bubbles in a pressure-varying field, has been shown to be responsible for many biophysical effects of ultrasound on cells. In this study, we correlate the presence and type of cavitation with a decrease in liposome size. Aqueous lipid suspensions surrounding a hydrophone were exposed to various intensities of ultrasound and hydrostatic pressures before measuring their size distribution with dynamic light scattering. As expected, increasing ultrasound intensity at atmospheric pressure decreased the average liposome diameter. The presence of collapse cavitation was manifested in the acoustic spectrum at high ultrasonic intensities. Increasing hydrostatic pressure was shown to inhibit the presence of collapse cavitation. Collapse cavitation, however, did not correlate with decreases in liposome size, as changes in size still occurred when collapse cavitation was inhibited either by lowering ultrasound intensity or by increasing static pressure. We propose a mechanism whereby stable cavitation, another type of cavitation present in sound fields, causes fluid shearing of liposomes and reduction of liposome size. A mathematical model was developed based on the Rayleigh-Plesset equation of bubble dynamics and principles of acoustic microstreaming to estimate the shear field magnitude around an oscillating bubble. This model predicts the ultrasound intensities and pressures needed to create shear fields sufficient to cause liposome size change, and correlates well with our experimental data.

Richardson, Eric S.; Pitt, William G.; Woodbury, Dixon J.

2007-01-01

95

Axial binding and host-guest interactions of a phthalocyanine resorcinarene cavitand hybrid.  

PubMed

A Zn phthalocyanine-resorcinarene cavitand hybrid was prepared. The axial binding and host-guest interactions of this hybrid with a pyridinyl-pyrene were investigated by UV-vis and fluorescence spectroscopic means, revealing the encapsulation of the guest maintained by axial coordination to the Zn phthalocyanine. Energy transfer between the pyrene and the phthalocyanine was evidenced. PMID:24276488

Topkaya, Derya; Dumoulin, Fabienne; Ahsen, Vefa; I?ci, Ümit

2014-02-01

96

Stimulated Emission Observed from an Organic Dye, Chloro-aluminum Phthalocyanine  

Microsoft Academic Search

We have observed that when a specific phthalocyanine solution (chloro-aluminum phthalocyanine dissolved in ethyl alcohol) is irradiated by a sufficiently powerful beam from a giant-pulse ruby laser, there occurs intense stimu- lated emission from the phthalocyanine molecules. The wavelength of this stimulated emission is centered at approximately 0.755 p. Its spectral half-width was observed

P. P. Sorokin; J. R. Lankard

1966-01-01

97

Enhanced Anticancer Efficacy by ATP-Mediated Liposomal Drug Delivery.  

PubMed

A liposome-based co-delivery system composed of a fusogenic liposome encapsulating ATP-responsive elements with chemotherapeutics and a liposome containing ATP was developed for ATP-mediated drug release triggered by liposomal fusion. The fusogenic liposome had a protein-DNA complex core containing an ATP-responsive DNA scaffold with doxorubicin (DOX) and could release DOX through a conformational change from the duplex to the aptamer/ATP complex in the presence of ATP. A cell-penetrating peptide-modified fusogenic liposomal membrane was coated on the core, which had an acid-triggered fusogenic potential with the ATP-loaded liposomes or endosomes/lysosomes. Directly delivering extrinsic liposomal ATP promoted the drug release from the fusogenic liposome in the acidic intracellular compartments upon a pH-sensitive membrane fusion and anticancer efficacy was enhanced both in vitro and in vivo. PMID:24764317

Mo, Ran; Jiang, Tianyue; Gu, Zhen

2014-06-01

98

Detection of liposomes in portal blood following oral administration  

SciTech Connect

125Iodine-labeled human immunoglobulin G-encapsulated dipalmitoyl phosphatidylcholine liposomes were prepared with or without asialoganglioside. Distribution of radioactivity following the oral administration of these liposomes in rats was checked in liver and in blood of the portal vein and heart. Gel filtration of plasma from the portal vein showed the presence of intact liposomes and protein. In contrast, neither liposomes nor protein were detected in cardiac blood but only lower molecular weight materials. The presence of liposomes in portal blood was further suggested from experiments using 6-carboxyfluorescein-entrapped liposomes. The level of liposomes in portal venous blood plasma was found to be lower in asialoganglioside liposomes. But this level could be increased substantially, almost to that in liposomes without asialoganglioside, by injection (iv) of asialofetuin.

Das, N.; Das, M.K.; Bachhawat, B.K.

1984-10-01

99

Multi-layered liposomes as optical resonators  

NASA Astrophysics Data System (ADS)

Multi-layered liposomes, comprising a concentric series of lipid bilayers - separated at fixed distances and compartmentalizing aqueous solutions of alternating refractive indices - are proposed as optical Bragg resonators. Seminal work focuses on the feasibility of successive encapsulations coupled with size-control via extrusion. Synthesis criteria for realization of these liposomes were subsequently discussed based on experimental observations. Numerical studies of the proposed structure showed discernible band gaps, qualifying their potential application in biological lasing.

Yong, Derrick; Ng, Wei Long; Lee, Elizabeth; Yu, Xia; Bosman, Michel; Chan, Chi Chiu

100

Striking follicular eruption to pegylated liposomal Doxorubicin.  

PubMed

: The adverse effects of pegylated liposomal doxorubicin are primarily cutaneous. The majority of these cutaneous side effects manifest as palmar-plantar erythrodysesthesia, whereas few reports of other cutaneous reactions exist in the literature. The authors report a case of an exuberant follicular eruption in a patient treated with pegylated liposomal doxorubicin. This case also highlights the potential mechanism underlying this unusual histological and clinical reaction. PMID:24614205

Dai, Julia; Micheletti, Robert; Rosenbach, Misha; Chu, Emily Y

2014-07-01

101

Surface fractals in liposome aggregation.  

PubMed

In this work, the aggregation of charged liposomes induced by magnesium is investigated. Static and dynamic light scattering, Fourier-transform infrared spectroscopy, and cryotransmission electron microscopy are used as experimental techniques. In particular, multiple intracluster scattering is reduced to a negligible amount using a cross-correlation light scattering scheme. The analysis of the cluster structure, probed by means of static light scattering, reveals an evolution from surface fractals to mass fractals with increasing magnesium concentration. Cryotransmission electron microscopy micrographs of the aggregates are consistent with this interpretation. In addition, a comparative analysis of these results with those previously reported in the presence of calcium suggests that the different hydration energy between lipid vesicles when these divalent cations are present plays a fundamental role in the cluster morphology. This suggestion is also supported by infrared spectroscopy data. The kinetics of the aggregation processes is also analyzed through the time evolution of the mean diffusion coefficient of the aggregates. PMID:19257067

Roldán-Vargas, Sándalo; Barnadas-Rodríguez, Ramon; Quesada-Pérez, Manuel; Estelrich, Joan; Callejas-Fernández, José

2009-01-01

102

Liposomes.  

National Technical Information Service (NTIS)

Oncology Overviews are a service of the International Cancer Research Data Bank (ICRDB) Program of the National Cancer Institute, intended to facilitate and promote the exchange of information between cancer scientists by keeping them aware of literature ...

1982-01-01

103

Sequential biphotonic processes: photochemical reactivity of phthalocyanine radicals  

SciTech Connect

Results of a study of the photochemistry of Rh(III), Al(III), and Zn(II) phthalocyanine cation radicals are reported here. The radicals were generated in a flash photolysis apparatus, which employs two flash-lamp-pump dye lasers. This excitation of the metallophthalocyanines at wavelengths of the phthalocyanine's Q band produced the long-lived triplet state. Irradiation of the phthalocyanine radicals led to rapid (t less than 1 ..mu..s) decomposition of these species followed by a partial recovery of the radical concentration. The dependence of radical yield on medium conditions was noted, and this dependence was probably attributable to an increase in the yield of the reactive excited state and/or a decrease in the rate of excited-state relaxation in changing from protic to aprotic media or replacing D/sub 2/O by H/sub 2/O. 10 references, 3 figures, 2 tables.

Van Vlierberge, B.; Ferraudi, G.

1987-01-28

104

Phthalocyanine organic solar cells - Indium/x-metal free phthalocyanine Schottky barriers  

NASA Astrophysics Data System (ADS)

Operation characteristics of NESA/x-metal free phthalocyanine/indium photovoltaic devices are described, and a film of polycrystalline particles of x-metal free phthalocyanine (x-H2Pc) are shown to exhibit strong photovoltaic effects when sandwiched between tin oxide and indium electrodes. The active region responsible for electric power generation is confined to the metal/semiconductor interface. A Schottky barrier built-in potential of 0.63 V is estimated from C-V measurements, and at a peak solar power of 135 mW/sq cm, a power conversion efficiency of 1.2 percent is obtained. The effects of pigment loading, cell thickness, light intensity, binder material, dye sensitization and the nature of barrier electrodes are also studied. The devices exhibit open-circuit voltages of 0.45 V, and the concept is considered a viable approach to constructing simple, economical photovoltaic devices which are significantly more efficient than evaporated film, although engineering efficiency is low due to low transmission of light through the indium barrier electrode.

Loutfy, R. O.; Sharp, J. H.; Hsiao, C. K.; Ho, R.

1981-08-01

105

Asymmetric grain distribution in phthalocyanine thin films  

SciTech Connect

Many electronic and optical properties of organic thin films depend on the precise morphology of grains. Iron phthalocyanine thin films are grown on sapphire substrates at different temperatures to study the effect of grain growth kinematics and to experimentally quantify the grain size distribution in organic thin films. The grain size is measured with an atomic force microscope and the data is processed and analyzed with well-known image segmentation algorithms. For relevant statistics, over 3000 grains are evaluated for each sample. The data show pronounced asymmetric grain growth with increasing deposition temperature from almost spherical grains at room temperature to elongated needlelike shapes at 260 deg. C. The average size along the major axis increases from 35 to 200 nm and along the minor axis from 25 to 90 nm. The distribution is almost symmetric at low-deposition temperatures, but becomes lognormal at higher temperatures. Strikingly, the major axis and minor axis of the elliptically shaped grains have different distributions at all temperatures due to the planar asymmetry of the molecule.

Gentry, K. Paul; Gredig, Thomas; Schuller, Ivan K. [Department of Physics and Astronomy, California State University-Long Beach, 1250 Bellflower Boulevard, Long Beach, California 90840 (United States); Department of Physics and Astronomy, University of California-San Diego, 9500 Gilman Drive, La Jolla, California 92093 (United States)

2009-11-01

106

Excited state dynamics of phthalocyanine films  

SciTech Connect

Femtosecond pump-probe transient absorption measurements were performed for thermally evaporated polycrystalline vanadyl and lead phthalocyanine (VOPc and PbPc) films in order to obtain information about the excitation energy migration and relaxation. The films were shown to be composed of phase II and amorphous material. Fast excitation localization in phase II was concluded from measurement and analysis of the ground and excited state spectra. Comparison of the ground state, difference absorption, and luminescence spectra suggests a small oscillator strength of the electronic transition from the lowest excited state to the ground state. The influence of local heating on the transient spectra is discussed, and the possibility to obtain the excitation decay kinetics free from this influence is proposed. Exciton-exciton annihilation with a time dependent rate (proportional to t{sup -0.5}) is observed in both films. This is explained by one-dimensional diffusion-limited annihilation. Linear relaxation times are equal to 28{+-}6 and 42{+-}8 ps and approximate intermolecular excitation hopping times of 0.1 divide 0.4 and 0.02 divide 0.08 ps were determined for VOPc and PbPc, respectively. 22 refs., 8 figs., 1 tab.

Gulbians, V.; Valkunas, L. [Vilnius Inst. of Physics (Lithuania)] [Vilnius Inst. of Physics (Lithuania); Chachisvillis, M.; Sundstrom, V. [Lund Univ. (Sweden)] [Lund Univ. (Sweden)

1996-02-08

107

Catalytic oxidation of sulfur dioxide by heterogeneous cobalt-phthalocyanine  

SciTech Connect

Various homogeneous and hybrid cobalt phthalocyanines were developed. They were shown to be effective catalysts for the catalytic degradation of many aqueous pollutants. The catalytic activity of these systems was attributed to their ability to activate molecular oxygen. Semiconductor titanium dioxide was found to be useful both as solid support and photocatalyst. The electron relay property of cobalt phthalocyanine on the photoactive TiO/sub 2/ surface was elucidated. The homogeneous and heterogeneous kinetics and mechanisms for the catalytic oxidation of aqueous sulfur dioxide were studied.

Hong, P.K.A.

1988-01-01

108

Charge Transfer Photophysics of Tetra(?-amino) Zinc Phthalocyanine  

Microsoft Academic Search

The absorption, fluorescence, and transient absorption spectra of Tetra(?-amino) zinc phthalocyanine, ZnPc(?-NH2)4, have been measured in polar solvents and compared with that of ZnPc(?-R)4 (R?=?H, NO2, OCH(CH3)2). While the latter three showed the typical photophysics of phthalocyanines, ZnPc(?-NH2)4 exhibits distinct spectral properties, a very low fluorescence quantum yield and a relatively long fluorescence lifetime.\\u000a These observations are explained by the

Xian-Fu Zhang; Xijiang Li; Lihong Niu; Lou Sun; Lu Liu

2009-01-01

109

Liposome-Based Mucoadhesive Formulations for Oral Delivery of Macromolecules  

Microsoft Academic Search

The design and evaluation of liposome-based mucoadhesive dosage form containing mucoadhesive polymers (e.g., chitosan, pectin,\\u000a carbopol, and PVA-R) have been described. Liposomes with different compositions were prepared and surface-modified by various\\u000a polymers. The surface coating or complexation of liposomes was confirmed by monitoring the changes in surface charge before\\u000a and after surface modification. The mucoadhesion of the liposome-based formulations has

Pornsak Sriamornsak; Jringjai Thongborisute; Hirofumi Takeuchi

110

Interaction of liposome-encapsulated cisplatin with biomolecules.  

PubMed

We prepared liposomes by hydrating 1,2-dioleoyl-sn-glycero-3-phosphocholine lipid with aqueous solutions of three "probe" molecules-cis-diamminedichloroplatinum(II) (cis-[Pt(II)(NH(3))(2)Cl(2)], cisplatin), guanosine 5'-monophosphate (5'-GMP), and 9-ethylguanine (9-EtG)-in phosphate-buffered saline as well as N-(2-hydroxyethyl)piperazine-N'-ethanesulfonic acid buffer. The positively charged hydrolysis product of cisplatin, [Pt(II)(NH(3))(2)Cl(H(2)O)](+), is in the inner core of the liposomes and negatively charged 5'-GMP embeds in the lipid bilayer of liposomes. In the presence of cisplatin, the size of the liposomes remains unchanged, and for 5'-GMP-embedded liposomes the size increases significantly compared with that of empty or control liposomes. In contrast, the neutral biomolecule 9-EtG was found to be dispersed in the exterior bulk water and the size of the liposomes remained the same as that of empty or control liposomes. When cisplatin-containing liposomes mix with 5'-GMP-embedded liposomes or liposomes with 9-EtG, the N7 nitrogen atom of 5'-GMP or 9-EtG binds the cisplatin, thus replacing the "leaving groups" and forming a bisadduct. After 48 h of mixing, the size of the liposomes changes for the mixture of 5'-GMP-embedded liposomes and cisplatin-containing liposomes. We used (1)H and (31)P NMR spectroscopic techniques to monitor incorporation or association of cisplatin and biomolecules with liposomes and their subsequent reactions with each other. The dynamic light scattering technique provided the size distribution of the liposomes in the presence and absence of probe molecules. PMID:22674433

Baruah, Bharat; Surin, Alexandr

2012-08-01

111

Binding of HLA Antigen-Containing Liposomes to Bacteria  

Microsoft Academic Search

Highly purified, detergent-solubilized HLA-A and -B antigens and HLA-D antigens were separately incorporated into liposomes. Detergent-solubilized transplantation antigens, but not papain-solubilized antigens lacking the membrane-integrated portions of the molecules, were bound to the liposomes. A considerable portion of the liposome-bound antigens displayed accessible antigenic sites, suggesting that they were oriented in the right-side-out direction. Liposomes containing the HLA-A and -B

Lars Klareskog; Goran Banck; Arne Forsgren; Per A. Peterson

1978-01-01

112

Unexpected Reactions by In Vivo Applications of PEGylated Liposomes  

Microsoft Academic Search

\\u000a PEGylated liposome, a liposome coated with polyethylene glycol (PEG), is understood to be biologically inert and, therefore,\\u000a a suitable vehicle for in vivo applications. The most successful example is the doxorubicin-containing PEGylated liposome,\\u000a known under the commercial name Doxil\\/Caelyx for cancer therapy. However, several researchers have found evidence that unexpected\\u000a immune responses occur even to such polymer-coated liposomes after intravenous

Tatsuhiro Ishida; Hiroshi Kiwada

113

Immunogenicity of Liposomal Malaria Sporozoite Antigen in Monkeys: Adjuvant Effects of Aluminum Hydroxide and Non-Pyrogenic Liposomal Lipid A.  

National Technical Information Service (NTIS)

The immunogenicity of a recombinant protein containing sequences from the tetrapeptide repeat region of the circumsporozoite protein of Plasmodium falciparum was enhanced by encapsulation in liposomes containing lipid A and adsorption of the liposomes wit...

R. L. Richards G. M. Swartz C. Schultz M. D. Hayre G. S. Ward

1989-01-01

114

Studies on pectin coating of liposomes for drug delivery  

Microsoft Academic Search

The present study investigated the surface coating of charged liposomes by three different types of pectin (LM, HM and amidated pectin) by particle size determinations and zeta potential measurements. The pectins and the pectin coated liposomes were visualized by atomic force microscopy. The adsorption of pectin onto positive liposomes yielded a reproducible increase in particle size and a shift of

Sanko Nguyen; Siv Jorunn Alund; Marianne Hiorth; Anna-Lena Kjøniksen; Gro Smistad

2011-01-01

115

Preparation and characterization of liposomes entrapping allergenic proteins  

Microsoft Academic Search

This work presents results of the preparation and characterization of small unilamellar liposomes for entrapping allergenic proteins extracted from the biomass of Dreschlera (Helminthosporium) monoceras cultivated by solid fermentation. Protein was entrapped by the dehydration-rehydration method, using lyophilization of preformed liposomes in order to prevent their degradation The reconstitution of lyophilized liposomes by hydration, their capacity for entrapping allergenic proteins

E. C. M. Cabral; R. L. Zollner; M. H. A. Santana

2004-01-01

116

Hydrogen peroxide production from reactive liposomes encapsulating enzymes  

Microsoft Academic Search

Reactive cationic and anionic liposomes have been prepared from mixtures of dimyristoylphosphatidylcholine (DMPC) and cholesterol incorporating dimethyldioctadecylammonium bromide and DMPC incorporating phosphatidylinositol, respectively. The liposomes were prepared by the vesicle extrusion technique and had the enzymes glucose oxidase (GO) encapsulated in combination with horseradish peroxidase (HRP) or lactoperoxidase (LPO). The generation of hydrogen peroxide from the liposomes in response to

Michael Kaszuba; Malcolm N. Jones

1999-01-01

117

[Property of liposomal fusion induced by acid-sensitive polymer].  

PubMed

The fusion between liposome-liposome, liposome-biomembarnes induced by acid-sensitive polymers has been systematically investigated. The polymer-liposomes were constructed by post-insertion method with the poly (2-ethylacrylic acid) (PEAA) alkylamide derivatives. The liposomal fusion was studied by use of fluorescence resonance energy transfer assay, particle size, fluorescent-photometer. The results indicated that the poly (2-ethylacrylic acid)-liposomes has very strong acidic induced fusion capability. Under acidic conditions, acid-sensitive polymer liposomes fused each other, the fusion closely related to the molecular weight of acid sensitivity polymer on the surface of liposomes. The acidic fusion of polymer-liposomes was dependent upon the lipids composition, the degree of fusion was reversely related to the cholesterol contents. Acid-en ci-nsitive polymer liposomes fused with erythrocyte ghosts. The liposomal fusion induced by acid-sensitive polymer associated with the increase of membrane permeability. The good acid-sensitivity of PEAA has been further demonstrated by membrane fusion in current experiments, and the liposomes prepared with lipid anchored-poly (2-ethylacrylic acid) were developeds s a potential pH sensitive delivery system. PMID:19048789

Wang, Ru-tao; Chen, Tao; Wang, Zhao; Hui, Min-quan; Fu, Jing-guo

2008-09-01

118

Sendai virus induced leakage of liposomes containing gangliosides.  

PubMed

Sendai virus induced liposome leakage has been studied by using liposomes containing a self-quenching fluorescent dye, calcein. The liposomes used in this study were prepared by a freeze and thaw method and were composed of phosphatidylcholine, phosphatidylserine, and phosphatidylethanolamine (1:2.60:1.48 molar ratio) as well as various amounts of gangliosides and cholesterol. The leakage rate was calculated from the fluorescence increment as the entrapped calcein leaked out of the liposomal compartment and was diluted into the media. It was shown that the target liposome leakage was virus dose dependent. Trypsin-treated Sendai virus in which the F protein had been quantitatively removed did not induce liposome leakage, indicating that the leakage was a direct result of F-protein interaction with the target bilayer membrane. The activation energy of this process was approximately 12 kcal/mol below 17 degrees C and approximately 25 kcal/mol above 17 degrees C. Gangliosides GM1, GD1a, and GT1b could serve as viral receptor under appropriate conditions. Liposome leakage showed a bell-shaped curve dependence on the concentration of ganglioside in the liposomes. No leakage was observed if the ganglioside content was too low or too high. Inclusion of cholesterol in the liposome bilayer suppressed the leakage rate of liposomes containing GD1a. It is speculated that the liposome leakage is a consequence of fusion between Sendai virus and liposomes. PMID:3006743

Tsao, Y S; Huang, L

1985-02-26

119

Liposomal Encapsulated Rhodomyrtone: A Novel Antiacne Drug  

PubMed Central

Rhodomyrtone isolated from the leaves of Rhodomyrtus tomentosa possesses antibacterial, anti-inflammatory, and anti-oxidant activities. Since rhodomyrtone is insoluble in water, it is rather difficult to get to the target sites in human body. Liposome exhibited ability to entrap both hydrophilic and hydrophobic compounds and easily penetrate to the target site. The present study aimed to develop a novel liposomal encapsulated rhodomyrtone formulations. In addition, characterization of liposome, stability profiles, and their antiacne activity were performed. Three different formulations of total lipid concentrations 60, 80, and 100??mol/mL were used. Formulation with 60??mol/mL total lipid (phosphatidylcholine from soybean and cholesterol from lanolin in 4?:?1, w/w) exhibited the highest rhodomyrtone encapsulation efficacy (65.47 ± 1.7%), average particle size (209.56 ± 4.8?nm), and ?-potential (–41.19 ± 1.3?mV). All formulations demonstrated good stability when stored for 2 months in dark at 4°C as well as room temperature. Minimal inhibitory concentration and minimal bactericidal concentration values of liposomal formulation against 11 clinical bacterial isolates and reference strains ranged from 1 to 4 and from 4 to 64??g/mL, respectively, while those of rhodomyrtone were 0.25–1 and 0.5–2??g/mL, respectively. The MIC and MBC values of liposome formulation were more effective than topical drugs against Staphylococcus aureus and Staphylococcus epidermidis.

Chorachoo, Julalak; Amnuaikit, Thanaporn; Voravuthikunchai, Supayang P.

2013-01-01

120

Remotely controlled diffusion from magnetic liposome microgels.  

PubMed

The reversible, temperature-dependent change in the permeability of a phospholipid bilayer has been used for controlling the diffusion rate of encapsulated molecular payload from liposomes. Liposomes were preloaded with a fluorescent dye and immobilized in calcium alginate hydrogel microparticles that also contained iron oxide nanoparticles. The composite microparticles were produced by a drop-on-demand inkjet method. The ability of iron oxide nanoparticles to locally dissipate heat upon exposure to a radio-frequency (RF) alternating magnetic field was used to control the local temperature and therefore diffusion from the liposomes in a contactless way using an RF coil. Several different release patterns were realized, including repeated on-demand release. The internal structure of the composite alginate-liposome-magnetite microparticles was investigated, and the influence of microparticle concentration on the heating rate was determined. In order to achieve a temperature rise required for the liposome membrane melting, the concentration of alginate beads should be at least 25% of their maximum packing density for the nanoparticle concentration and specific absorption rate used. PMID:23461732

Hanuš, Jaroslav; Ullrich, Martin; Dohnal, Ji?í; Singh, Mandeep; St?pánek, František

2013-04-01

121

Treatment of digital ischemia with liposomal bupivacaine.  

PubMed

Objective. This report describes a case in which the off-label use of liposomal bupivacaine (Exparel) in a peripheral nerve block resulted in marked improvement of a patient's vasoocclusive symptoms. The vasodilating and analgesic properties of liposomal bupivacaine in patients with ischemic symptoms are unknown, but our clinical experience suggests a role in the management of patients suffering from vasoocclusive disease. Case Report. A 45-year-old African American female was admitted to the hospital with severe digital ischemic pain. She was not a candidate for any vascular surgical or procedural interventions. Two continuous supraclavicular nerve blocks were placed with modest clinical improvement. These effects were also short-lived, with the benefits resolving after the discontinuation of the peripheral nerve blocks. She continued to report severe pain and was on multiple anticoagulant medications, so a decision was made to perform an axillary nerve block using liposomal bupivacaine (Exparel) given the compressibility of the site as well as the superficial nature of the target structures. Conclusions. This case report describes the successful off-label usage of liposomal bupivacaine (Exparel) in a patient with digital ischemia. Liposomal bupivacaine (Exparel) is currently FDA approved only for wound infiltration use at this time. PMID:24653844

Raul Soberón, José; Duncan, Scott F; Sternbergh, W Charles

2014-01-01

122

Phosphosubstituted phthalocyanine derivatives as effective photosensitizers for PDT  

Microsoft Academic Search

The photodynamic therapy in the spectral range 690 - 750 nm is more perspective for treatment of the deeply located tumors because the absorption of tissue has a significant minimis in this spectral range. A series of phosphosubstituted phthalocyanine derivatives were studied in vitro and in experiment on white mice. It has been shown that photodynamic therapy using these photosensitizers

Gennady A. Meerovich; Eugene A. Lukyanets; Olga A. Yuzhakova; Nadezgda L. Torshina; Victor B. Loschenov; Alexander A. Stratonnikov; Eugenia A. Kogan; Georgy N. Vorozhtsov; Andrei V. Kunetz; Yury P. Kuvshinov; Boris K. Poddubny; Anna I. Volkova; Anna M. Posypanova

1997-01-01

123

LASERS IN MEDICINE: Two-photon excitation of aluminium phthalocyanines  

NASA Astrophysics Data System (ADS)

A demonstration is given of the feasibility of two-photon excitation of aluminium phthalocyanine and of the pharmaceutical preparation 'Fotosens', used in photodynamic therapy. The excitation source was an Nd:YAG laser emitting at the 1064 nm wavelength. The spectra of the two-photon-excited luminescence were obtained and the two-photon absorption cross sections were determined.

Meshalkin, Yu P.; Alfimov, E. E.; Vasil'ev, N. E.; Denisov, A. N.; Makukha, V. K.; Ogirenko, A. P.

1999-12-01

124

LASERS IN MEDICINE: Two-photon excitation of aluminium phthalocyanines  

Microsoft Academic Search

A demonstration is given of the feasibility of two-photon excitation of aluminium phthalocyanine and of the pharmaceutical preparation 'Fotosens', used in photodynamic therapy. The excitation source was an Nd:YAG laser emitting at the 1064 nm wavelength. The spectra of the two-photon-excited luminescence were obtained and the two-photon absorption cross sections were determined.

Yu P. Meshalkin; E. E. Alfimov; N. E. Vasil'ev; A. N. Denisov; V. K. Makukha; A. P. Ogirenko

1999-01-01

125

1,8-Naphthalene Linked Cofacial Binuclear Phthalocyanines.  

National Technical Information Service (NTIS)

Cofacial binuclear phthalocyanines linked by a three atom bridge are described, utilizing the 1,8-position of the naphthalene nucleus. Electrochemical and uv/vis/nmr data are reported for the metal-free and cobalt derivatives in various oxidation states. ...

C. C. Leznoff H. Lam A. W. Nevin N. Kobayashi P. Janda

1987-01-01

126

Raman spectra of solid films—II. Vanadyl phthalocyanine  

NASA Astrophysics Data System (ADS)

Preresonance and resonance Raman spectra of vanadyl phthalocyanine films (˜ 100 nm) deposited on glass and quartz subtrates at different temperatures have been studied. A vibrational assignment of observed wavenumbers is proposed and intensity changes associated with distinctive polymorphic forms are discussed.

Aroca, Ricardo; Loutfy, Rafik O.

127

Novel Phthalocyanine Polymers for Applications in Optical Devices  

Microsoft Academic Search

The optical properties of substituted phthalocyaninato-polysiloxanes and their copolymers having the chromophores separated by spacers are discussed in terms of the molecular exciton model. The shift of the Q band maximum of the siloxane polymer compared to the monomeric phthalocyanine as well as the absorption profile is well in accordance with the predictions of the model based on structural data

Thomas Sauer; Walter Caseri; Gerhard Wegner

1990-01-01

128

Amphiphilic phthalocyanine-cyclodextrin conjugates for cancer photodynamic therapy.  

PubMed

Three phthalocyanines (Pcs) conjugated with ?-, ?- and ?-cyclodextrins (CDs) were prepared and their application as photosensitizer (PS) agents was assessed by photophysical, photochemical and in vitro photobiological studies. The photoactivity of and ensures their potential as PDT drugs against UM-UC-3 human bladder cancer cells. PMID:24943806

Lourenço, Leandro M O; Pereira, Patrícia M R; Maciel, Elisabete; Válega, Mónica; Domingues, Fernando M J; Domingues, Maria R M; Neves, Maria G P M S; Cavaleiro, José A S; Fernandes, Rosa; Tomé, João P C

2014-07-01

129

Submonolayer growth of H2-phthalocyanine on Ag(111)  

NASA Astrophysics Data System (ADS)

We present a comprehensive study of structural and electronic properties of the adsorbate system H2-phthalocyanine (H2Pc) on Ag(111). A comparison with copper-phthalocyanine (CuPc) on Ag(111) allows us to elucidate the impact of the central metal atom in the molecule on the adsorbate-substrate interaction. This metal atom is one fundamental parameter which can be changed in order to modify the properties of phthalocyanine molecules, and therefore its influence on the adsorption behavior is highly relevant. From high-resolution electron diffraction, we obtained a phase diagram for submonolayer coverages which turns out to be similar to that of CuPc/Ag(111). The most striking difference is a higher stability of a commensurate phase, indicating a stronger and more adsorption site-specific bonding of the H2Pc molecules. Furthermore, ultraviolet photoelectron spectroscopy and x-ray standing waves prove chemisorptive interaction between molecules and substrate and a significant bending of the molecules with the nitrogen atoms approaching the surface. We conclude that the attractive interaction of metal-phthalocyanine molecules with Ag(111) is mainly mediated by the aromatic body of the molecule (the tetraazaporphyrin ring in particular) rather than by the central metallic atom which (in the case of CuPc) already shows Pauli repulsion.

Kröger, Ingo; Bayersdorfer, Patrick; Stadtmüller, Benjamin; Kleimann, Christoph; Mercurio, Giuseppe; Reinert, Friedrich; Kumpf, Christian

2012-11-01

130

Aminopyridine coordinated iron phthalocyanines: Synthesis, structure, and characterization  

Microsoft Academic Search

Two bis-axially coordinated iron phthalocyanines, bis-[3-aminopyridine] phthalocyaninatoiron (3-ampyFePc) and bis-[4-aminopyridine] phthalocyaninatoiron (4-ampyFePc), were synthesized and characterized. The intermolecular ?–? intereactions are investigated from the crystal structures and related to the ?max of UV\\/vis diffuse reflectance spectra (UV\\/vis DRS).

Xin Fang; Feng-Ju Yang; Hai-Yang Yu; Nai-Sheng Chen; Ming-Dong Huang; Jun-Dong Wang

2009-01-01

131

Synthesis, photophysical and photochemical properties of substituted zinc phthalocyanines.  

PubMed

The synthesis, photophysical and photochemical properties of the 4-({3,4,5-tris-[2-(2-ethoxyethoxy)ethyloxy]benzyl}oxy) and 4-({3,4,5-tris-[2-(2-ethoxyethoxy)ethyloxy]benzyl}thio) zinc(ii) phthalocyanines are reported for the first time. The new compounds have been characterized by elemental analysis, IR, (1)H and (13)C NMR spectroscopy, electronic spectroscopy and mass spectra. General trends are described for photodegradation, singlet oxygen, fluorescence and triplet excited state quantum yields, and triplet state and fluorescence lifetimes of these compounds in dimethylsulfoxide (DMSO). The fluorescence of the complexes was quenched by benzoquinone (BQ). The effects of the substitution on the photophysical and photochemical parameters of the zinc(II) phthalocyanines (6, 7 and 8) are also reported. Photophysical and photochemical properties of phthalocyanine complexes are very useful for PDT applications. The substituted Zn(II) phthalocyanines showed high triplet and singlet oxygen quantum yields. High singlet oxygen quantum yields are very important for Type II mechanism. Thus, these complexes show potential as Type II photosensitizers. PMID:17712444

Gürol, Ilke; Durmu?, Mahmut; Ahsen, Vefa; Nyokong, Tebello

2007-09-14

132

Origin of electronic transport of lithium phthalocyanine iodine crystal  

NASA Astrophysics Data System (ADS)

The electronic structures of Lithium Phthalocyanine Iodine are investigated using density functional theory. Comparing the band structures of several model crystals, the metallic conductivity of highly doped LiPcIx can be explained by the band of doped iodine. These results reveal that there is a new mechanism for electronic transport of doped organic semiconductors that the dopant band plays the main role.

Koike, Noritake; Oda, Masato; Shinozuka, Yuzo

2013-12-01

133

Light-Activated Content Release from Liposomes  

PubMed Central

Successful integration of diagnostic and therapeutic actions at the level of individual cells requires new materials that combine biological compatibility with functional versatility. This review focuses on the development of liposome-based functional materials, where payload release is activated by light. Methods of sensitizing liposomes to light have progressed from the use of organic molecular moieties to the use of metallic plasmon resonant structures. This development has facilitated application of near infrared light for activation, which is preferred for its deep penetration and low phototoxicity in biological tissues. Presented mechanisms of light-activated liposomal content release enable precise in vitro manipulation of minute amounts of reagents, but their use in clinical diagnostic and therapeutic applications will require demonstration of safety and efficacy.

Leung, Sarah J.; Romanowski, Marek

2012-01-01

134

Bioavailability of polyphenol liposomes: a challenge ahead.  

PubMed

Dietary polyphenols, including flavonoids, have long been recognized as a source of important molecules involved in the prevention of several diseases, including cancer. However, because of their poor bioavailability, polyphenols remain difficult to be employed clinically. Over the past few years, a renewed interest has been devoted to the use of liposomes as carriers aimed at increasing the bioavailability and, hence, the therapeutic benefits of polyphenols. In this paper, we review the causes of the poor bioavailability of polyphenols and concentrate on their liposomal formulations, which offer a means of improving their pharmacokinetics and pharmacodynamics. The problems linked to their development and their potential therapeutic advantages are reviewed. Future directions for liposomal polyphenol development are suggested. PMID:24300518

Mignet, Nathalie; Seguin, Johanne; Chabot, Guy G

2013-01-01

135

Electronic properties of the interface between hexadecafluoro copper phthalocyanine and unsubstituted copper phthalocyanine films  

SciTech Connect

The formation of an interface during the deposition of unsubstituted copper phthalocyanine (CuPc) films on the surface of hexadecafluoro copper phthalocyanine (F{sub 16}-CuPc) films is studied. An incident low-energy electron beam with energies from 0 to 25 eV is used to test the surface under study according to the very-low-energy electron-diffraction technique (VLEED) in the mode of total current spectroscopy. For F{sub 16}-CuPc films, the structure of the maxima in the total current spectra and its main differences from the structure of the maxima for the CuPc film are determined in the energy range from 5 to 15 eV above the Fermi level. The differences in the structure of vacant electron orbitals for CuPc and F{sub 16}-CuPc are also revealed using density functional theory calculations. As a result of an analysis of variations in the intensities of the total current spectra of the CuPc and F{sub 16}-CuPc films, it is assumed that an intermediate layer up to 1 nm thick appears during the formation of an interface between these films, which is characterized by a spread of the features in the total current spectrum. The height, width, and change in the work function are determined for the studied F{sub 16}-CuPc/NuPc interface barrier. A decrease in the level of vacuum by 0.7 eV occurs in the boundary region, which corresponds to electron density transfer from the CuPc film toward the F{sub 16}-CuPc substrate.

Komolov, A. S., E-mail: akomolov07@ya.ru; Lazneva, E. F. [Saint Petersburg State University, Faculty of Physics (Russian Federation); Pshenichnyuk, S. A. [Russian Academy of Sciences, Institute of Molecular and Crystal Physics, Ufa Research Center (Russian Federation); Gavrikov, A. A.; Chepilko, N. S.; Tomilov, A. A.; Gerasimova, N. B.; Lezov, A. A.; Repin, P. S. [Saint Petersburg State University, Faculty of Physics (Russian Federation)

2013-07-15

136

Preparation and characterization of hydroxyapatite/liposome core shell nanocomposites  

NASA Astrophysics Data System (ADS)

Hydroxyapatite (HAP)/liposome core-shell nanocomposites have been prepared at room temperature. The liposome shells and the precipitate cores ranged in diameter mainly from 80 to 140 nm and from 40 to 120 nm, respectively. Rod-like whiskers ranging in length mainly from 10 to 30 nm were obtained after separating the precipitates from the liposomes. In contrast, the whiskers synthesized without liposomes ranged in length mainly from 70 to 140 nm. The precipitates synthesized both with and without liposomes were poorly crystalline, and had a similar chemical composition to the natural HAP.

Chu, Maoquan; Liu, Guojie

2005-08-01

137

Mechanical properties of a giant liposome studied using optical tweezers  

NASA Astrophysics Data System (ADS)

The mechanical properties of a micrometer-sized giant liposome are studied by deforming it from the inside using dual-beam optical tweezers. As the liposome is extended, its shape changes from a sphere to a lemon shape, and finally, a tubular part is generated. The surface tension ? and the bending rigidity ? of the lipid membrane are obtained from the measured force-extension curve. In a one-phase liposome, it was found that ? increases as the charged component increases but ? remains approximately constant. In a two-phase liposome, the characteristic deformation and the force-extension curve differ from those observed for the one-phase liposome.

Shitamichi, Yoko; Ichikawa, Masatoshi; Kimura, Yasuyuki

2009-09-01

138

Microfluidic-enabled liposomes elucidate size-dependent transdermal transport.  

PubMed

Microfluidic synthesis of small and nearly-monodisperse liposomes is used to investigate the size-dependent passive transdermal transport of nanoscale lipid vesicles. While large liposomes with diameters above 105 nm are found to be excluded from deeper skin layers past the stratum corneum, the primary barrier to nanoparticle transport, liposomes with mean diameters between 31-41 nm exhibit significantly enhanced penetration. Furthermore, multicolor fluorescence imaging reveals that the smaller liposomes pass rapidly through the stratum corneum without vesicle rupture. These findings reveal that nanoscale liposomes with well-controlled size and minimal size variance are excellent vehicles for transdermal delivery of functional nanoparticle drugs. PMID:24658111

Hood, Renee R; Kendall, Eric L; Junqueira, Mariana; Vreeland, Wyatt N; Quezado, Zenaide; Finkel, Julia C; DeVoe, Don L

2014-01-01

139

Microfluidic-Enabled Liposomes Elucidate Size-Dependent Transdermal Transport  

PubMed Central

Microfluidic synthesis of small and nearly-monodisperse liposomes is used to investigate the size-dependent passive transdermal transport of nanoscale lipid vesicles. While large liposomes with diameters above 105 nm are found to be excluded from deeper skin layers past the stratum corneum, the primary barrier to nanoparticle transport, liposomes with mean diameters between 31–41 nm exhibit significantly enhanced penetration. Furthermore, multicolor fluorescence imaging reveals that the smaller liposomes pass rapidly through the stratum corneum without vesicle rupture. These findings reveal that nanoscale liposomes with well-controlled size and minimal size variance are excellent vehicles for transdermal delivery of functional nanoparticle drugs.

Junqueira, Mariana; Vreeland, Wyatt N.; Quezado, Zenaide; Finkel, Julia C.; DeVoe, Don L.

2014-01-01

140

Application of liposomes in drug development -- focus on gastroenterological targets  

PubMed Central

Over the past decade, liposomes became a focal point in developing drug delivery systems. New liposomes, with novel lipid molecules or conjugates, and new formulations opened possibilities for safely and efficiently treating many diseases including cancers. New types of liposomes can prolong circulation time or specifically deliver drugs to therapeutic targets. This article concentrates on current developments in liposome based drug delivery systems for treating diseases of the gastrointestinal tract. We will review different types and uses of liposomes in the development of therapeutics for gastrointestinal diseases including inflammatory bowel diseases and colorectal cancer.

Zhang, Jian-Xin; Wang, Kun; Mao, Zheng-Fa; Fan, Xin; Jiang, De-Li; Chen, Min; Cui, Lei; Sun, Kang; Dang, Sheng-Chun

2013-01-01

141

Fluorescence Resonance Energy Transfer in Polydiacetylene Liposomes  

PubMed Central

Conjugated polydiacetylene (PDA) possessing stimuli-responsive properties has been intensively investigated for developing efficient sensors. We report here fluorescence resonance energy transfer (FRET) in liposomes synthesized using different molar ratios of dansyl-tagged diacetylene and diacetylene–carboxylic acid monomers. Photopolymerization of diacetylene resulted in cross-linked PDA liposomes. We used steady-state electronic absorption, emission, and fluorescence anisotropy (FA) analysis to characterize the thermal-induced FRET between dansyl fluorophores (donor) and PDA (acceptor). We found that the monomer ratio of acceptor to donor (Rad) and length of linkers (functional part that connects dansyl fluorophores to the diacetylene group in the monomer) strongly affected FRET. For Rad = 10 000, the acceptor emission intensity was amplified by more than 18 times when the liposome solution was heated from 298 to 338 K. A decrease in Rad resulted in diminished acceptor emission amplification. This was primarily attributed to lower FRET efficiency between donors and acceptors and a higher background signal. We also found that the FRET amplification of PDA emissions after heating the solution was much higher when dansyl was linked to diacetylene through longer and flexible linkers than through shorter linkers. We attributed this to insertion of dansyl in the bilayer of the liposomes, which led to an increased dansyl quantum yield and a higher interaction of multiple acceptors with limited available donors. This was not the case for shorter and more rigid linkers where PDA amplification was much smaller. The present studies aim at enhancing our understanding of FRET between fluorophores and PDA-based conjugated liposomes. Furthermore, receptor tagged onto PDA liposomes can interact with ligands present on proteins, enzymes, and cells, which will produce emission sensing signal. Therefore, using the present approach, there exist opportunities for designing FRET-based highly sensitive and selective chemical and biochemical sensors.

Li, Xuelian; Matthews, Shelton; Kohli, Punit

2009-01-01

142

Enhancing nicotine vaccine immunogenicity with liposomes  

PubMed Central

A major liability of existing nicotine vaccine candidates is the wide variation in anti-nicotine immune responses among clinical trial participants. In order to address this liability, significant emphasis has been directed at evaluating adjuvants and delivery systems that confer more robust potentiation of the anti-nicotine immune response. Toward that end, we have initiated work that seeks to exploit the adjuvant effect of liposomes, with or without Toll-like receptor agonist(s). The results of the murine immunization study described herein support the hypothesis that a liposomal nicotine vaccine formulation may provide a means for addressing the immunogenicity challenge.

Lockner, Jonathan W.; Ho, Sam On; McCague, Karen C.; Chiang, Su Ming; Do, Thai Q.; Fujii, Gary; Janda, Kim D.

2013-01-01

143

[Interaction of aldolase A with lecithin liposomes].  

PubMed

The aldolase A binding to the lecithin liposomes (Kd = 2.4 +/- 0.1 X 10(-3) M) has been shown by the fluorescence and tryptophan phosphorescence at the room temperature. The interaction is accompanied by an increase in the phospholipid bilayer microviscosity, and some conformational changes in the hydrophobic part of the enzyme, pronouncing themselves in Trp-147 environment rigidity, decrease. The observation of membrane viscosity vs. incubation time revealed practically instant enzyme-membrane interaction and no gradual incorporation. The accessibility of the NAD-binding domain of aldolase for NADH in the liposome presence remains unaltered. PMID:3394175

Sytnik, A I; Chumachenko, Iu V; Volovik, Z N; Demchenko, A P

1988-01-01

144

Photovoltaic properties of cadmium sulfide/trivalent-metal phthalocyanine heterojunction devices  

NASA Astrophysics Data System (ADS)

Thin-film photovoltaic devices consisting of a CdS/trivalent-metal phthalocyanine heterojunction have been prepared. The devices are fabricated by first electrodepositing a thin film of CdS onto a transparent conducting indium-tin-oxide substrate and then depositing phthalocyanine and gold layers sequentially in a vacuum coater. The trivalent-metal phthalocyanines used are chloroaluminum chlorophthalocyanine, chloroaluminum phthalocyanine, and chloroindium phthalocyanine. Under an AM2 illumination of 75 mW/sq cm, these heterojunction devices produce an open-circuit voltage of 0.70 V and short-circuit current of 0.8 mA/sq cm. The conversion efficiency is about 0.2 percent, which represents one of the highest values reported for phthalocyanine photovoltaic devices at high light intensity.

Hor, A.-M.; Loutfy, R. O.; Hsiao, C.-K.

1983-01-01

145

Liposomal delivery and polyethylene glycol-liposomal oxaliplatin for the treatment of colorectal cancer (Review)  

PubMed Central

Oxaliplatin is effective for the treatment of advanced colorectal cancer; however, its application is restricted due to its dose-limiting toxicity. Liposomes are sphere-shaped vesicles consisting of one or more phospholipid bilayers. Liposomes as drug carriers are characterized by delayed release, lesion targeting and may be used as a drug-delivery system to decrease the side effects of cytotoxic drugs. Active targeting modification of liposomes may change the biological distribution of the anticancer agents, reduce or reverse multidrug resistance of tumor cells and enhance the effects of anticancer therapy. Based on the characteristics mentioned above, the aim of the present review was to demonstrate that polyethylene glycol-liposomes containing oxaliplatin may offer advantages for the treatment of colorectal cancer in clinical practice.

YANG, CHUANG; FU, ZHONG-XUE

2014-01-01

146

Localization study of co-phthalocyanines in cells by Raman micro(spectro)scopy  

Microsoft Academic Search

An investigation of intracellular localization of Co-phthalocyanines is reported. The Raman images of K562 cells stained with phthalocyanine were acquired. To understand the peculiarities of the Raman images, measurements were performed at different z-axis positions. The intracellular concentration of phthalocyanine was estimated. A colocalization study was carried out using the fluorescence probes FITC-dextran and acridine orange by means of Raman

S. Y. Arzhantsev; A. Y. Chikishev; N. I. Koroteev; J. Greve; C. Otto; N. M. Sijtsema

1999-01-01

147

Hydrogen peroxide vapor sensor using metal-phthalocyanine functionalized carbon nanotubes  

Microsoft Academic Search

We have developed a process for preparation of composites by blending and ultrasonification of multi-walled carbon nanotubes with metal-phthalocyanines and have used the same as very selective and sensitive sensor for detection of H2O2 vapors. A combination of sensors made from composites of cobalt-phthalocyanine and copper-phthalocyanine with multiwall carbon nanotubes has been found to show opposite conductivities to H2O2 vapors

A. L. Verma; Swasti Saxena; G. S. S. Saini; Vikesh Gaur; V. K. Jain

2011-01-01

148

First-row transition metal phthalocyanines as catalysts for water electrolysis: a comparative study  

Microsoft Academic Search

Modification of carbon electrodes with first row transition metal phthalocyanines results in the lowering of the potentials needed for water electrolysis in basic media, by 600 to 700 mV when compared to unmodified carbon electrodes. Nickel(II), cobalt(II) and iron(II) phthalocyanines show higher catalytic activity than zinc(II), manganese(II), copper(II) and metal free phthalocyanines.

Natalia Chebotareva; Tebello Nyokong

1997-01-01

149

Encapsulating nanoemulsions inside eLiposomes for ultrasonic drug delivery.  

PubMed

An eLiposome is a liposome encapsulating an emulsion nanodroplet and can be used for drug delivery. For example, therapeutic agents are encapsulated inside the eLiposomes, and the application of ultrasound can cause the emulsion droplet to change from liquid to gas, thus increasing the volume inside the vesicle and causing rupture and the release of the drug. In this research, two different methods were used to prepare eLiposomes. In the first method, emulsion droplets were made of perfluorohexane or perfluoropentane and stabilized with 1,2-dipalmitoyl-sn-glycero-3-phosphate. A layer of 1,2-dimyristoyl-sn-glycero-3-phosphocholine was dried in a round-bottomed flask. Then the emulsion suspension was added to the flask. As the suspension hydrated the phospholipids, they formed liposomes around the emulsions. In the second method, emulsions and liposomes were made separately, and then they were mixed using ultrasound. The advantage of this second method compared to the previous one is that eLiposomes can be made with fewer restrictions because of incompatible combinations of surfactants. Dynamic light scattering and transmission electron microscopy were used to measure the size of the emulsions, liposomes, and eLiposomes. The size of eLiposomes is appropriate for extravasation into tumors with malformed capillary beds. We hypothesize that ultrasound breaks open these eLiposomes. Both types of eLiposomes were constructed with folate attached via a poly(ethylene glycol) tether to induce endocytosis of the eLiposome. The latter eLiposomes were successfully used to deliver calcein as a model drug to HeLa cells. PMID:22989347

Javadi, Marjan; Pitt, William G; Belnap, David M; Tsosie, Naakaii H; Hartley, Jonathan M

2012-10-16

150

Co-encapsulation of isoniazid and rifampicin in liposomes and characterization of liposomes by derivative spectroscopy.  

PubMed

Taking into consideration the benefits of the combined therapy of isoniazid (INH) and rifampicin (RIF), this study focused on co-encapsulation of INH and RIF in the same liposome formulation. INH was incorporated in the aqueous phase and RIF in the lipid layer. Liposomes containing either INH or RIF were also prepared. All liposome formulations were compared for their loading capacity, encapsulation percentage and release properties. Drug amounts in the liposomes were estimated using peak-to-peak first-order derivative UV spectroscopy. Among the liposome formulations DPPC:chol liposomes showed the highest loading capacity (106.70 +/- 0.12 for INH and 18.17 +/- 0.06 (x 10(-3)) for RIF) and encapsulation percentage (73.84 +/- 0.78 for INH and 81.53 +/- 2.06 for RIF) compared to EPC:chol liposomes (loading capacity 93.36 +/- 0.58 for INH and 17.87 +/- 0.11 (x 10(-3)) for RIF; encapsulation percentage 64.61 +/- 0.51 for INH and 74.45 +/- 0.48 for RIF). Co-encapsulation of INH and RIF increased their individual encapsulation percentage and extended drug release compared to the formulations containing drug alone (Table 2). Results of this study support the conclusion that lipid and water soluble drugs can be successfully co-encapsulated in the same liposome formulation and also show that derivative UV spectroscopy is a sensitive method for direct and accurate quantification of these co-encapsulated drugs. PMID:15129978

Gürsoy, Ayla; Kut, Ece; Ozkirimli, Sumru

2004-03-01

151

GMP PRODUCTION OF LIPOSOMES PRODUCTION OF LIPOSOMES - - A NEW INDUSTRIAL APPROACH A NEW INDUSTRIAL APPROACH  

Microsoft Academic Search

Passive entrapment of rh-Cu\\/Zn-SOD: The liposomes are produced with the multiple injection mode. The 33kDa and hydrophilic rh-Cu\\/Zn-SOD, which is produced in E.coli is passively entrapped in liposomes consisting of DPPC, cholesterol and stearylamine. The protein solution was pumped from vessel A to vessel B passing the crossflow injection module, where the ethanol\\/ lipid solution is injected into the protein

152

Bone marrow uptake of liposome-entrapped spin label after liver blockade with empty liposomes.  

PubMed

Using an ESR spectrometer, we studied the time course of the uptake of the liposome-entrapped spin label 2,2,6,6-tetramethylpiperidine-N-oxyl-4-trimethylammonium in liver, spleen, and bone marrow following reticuloendothelial liver blockade. Our results show that suppression of the phagocytic activity of the liver increases the delivery of liposomes to the spleen and bone marrow without substantially altering uptake by the liver. PMID:2733596

Federico, M; Iannone, A; Chan, H C; Magin, R L

1989-06-01

153

Innovative Liposomes as a Transfollicular Drug Delivery System: Penetration into Porcine Hair Follicles  

Microsoft Academic Search

Liposomes had been widely used for drug delivery in the past. In this study, five different liposomes were used as a follicular delivery system in pig ear skin. The liposomes mainly differed in their sphere diameter, lipid composition, and surface charge. A novel class of liposomes being amphoteric in their charge behavior are compared to established anionic and cationic liposomes.

Sascha Jung; Nina Otberg; Gisela Thiede; Heike Richter; Wolfram Sterry; Steffen Panzner; Jürgen Lademann

2006-01-01

154

The role of ? 2-glycoprotein I in liposome–hepatocyte interaction  

Microsoft Academic Search

Adsorption of serum proteins to the liposomal surface plays a critical role in liposome clearance from the blood. The aim of this study was to investigate the role of liposome-adsorbed serum proteins in the interaction of liposomes with hepatocytes. We analyzed the serum proteins adsorbing to the surface of differently composed small unilamellar liposomes during incubation with human or rat

X. Yan; H. W. M. Morselt; G. L. Scherphof; K. Poelstra; J. A. A. M. Kamps

2004-01-01

155

Optical limiting of eight-?-octa-octyloxy-phthalocyanines for picosecond pulses in solution  

NASA Astrophysics Data System (ADS)

The optical power limiting performances for eight-?-octa-octyloxy phthalocyanines with initial linear transmission T0=88-92% at 532 nm in a 0.5 cm spectroscopic cell in toluene have been measured with 35 ps pulses, in which eight-?-octa-octyloxy phthalocyanine free-base exhibits the strongest optical limiting ability through a reverse saturable absorption from S 1?S n excited singlet states with ?S 1=4.0×10 -17 cm 2. The optical limiting thresholds are 50, 130 and 140 mJ/cm 2 at T/ T0=0.5 for eight-?-octa-octyloxy phthalocyanine free base, nickel phthalocyanine, and lead phthalocyanine respectively. The throughput of eight-?-octa-octyloxy phthalocyanine free base is clamped down to 70 mJ/cm 2 with the limiting nonlinear transmittance Tlim=0.18 as the incident fluence reaching to 400 mJ/cm 2. The aggregation behaviors for eight-?-octa-octyloxy phthalocyanines have been studied, in which the aggregation equilibrium constant k=5.6×10 3 in toluene for eight-?-octa-octyloxy phthalocyanine free base is larger than in mixed solvent containing acetonitrile ( k'=1.4×10 3). This means that the eight-?-octa-octyloxy phthalocyanines aggregate more easily in nonpolar solvent than in polar solvent through the ?- ? interaction.

Chen, Yu; Wang, Duoyuan; Li, Yunjing; Nie, Yuxin

2003-12-01

156

Zinc oxide and metal phthalocyanine based hybrid P-N junction diodes  

NASA Astrophysics Data System (ADS)

Hybrid p-n junction diode based on zinc oxide (ZnO) and metal phthalocyanine (MePc) has been demonstrated using highly conducting Al doped ZnO as transparent electrode. Three different MePcs: copper phthalocyanine, zinc phthalocyanine (ZnPc), and cobalt phthalocyanine are used as p-type layer in hybrid p-n junction. It is found that most desirable performance can be achieved in ZnO/ZnPc based hybrid p-n junction. The depletion region in hybrid p-n junctions has been measured using current-voltage and capacitance-voltage characteristics.

Singh, Budhi; Ghosh, Subhasis

2013-09-01

157

Highly Unquenched Orbital Moment In Fe Phthalocyanine  

NASA Astrophysics Data System (ADS)

Metal-Phthalocyanine molecules (MPc) form a family of compounds with a wide range of commercial application such as catalysts or dyes, and more recently in thin film technology. In an early work we found that in the ?-phase of FePc, where the FePc molecules are stacked in a herringbone structure, the Fe atoms are strongly magnetically coupled into ferromagnetic Ising chains with very weak antiferromagnetic interchain coupling. The chains achieve 3D long range ordering at TN=10 K, and strong irreversibility (slow relaxation) below 5K. The Fe(II) is in a S=1 state and the hyperfine field in the ordered phase reaches a record value in Fe(II) of Bhf=66.2 T. This result is consistent with a large, unquenched orbital moment. It has been measured directly in a X-ray Magnetic Circular Dichroism (XMCD) spectroscopic study on FePc thin films deposited parallel on a Au surface predeposited on a Si substrate. The XMCD spectra at the L3 and L2 edges were measured as a function of incident angle ?. The orbital moment is | mL |=0.53±0.04?B and the isotropic spin component is mS=0.64±0.05?B. The origin of this unusually high orbital moment is the incompletely filled eg level lying close to the Fermi energy. The ferromagnetically coupled Fe moments show strong, in-plane anisotropy [1]. Angular dependent measurements at the Fe K-edge also show strong quadrupolar excitations associated to a strong orbital moment, confirming the above result of the existence of a large, unquenched orbital moment in this molecule. Submonolayer FePc thin films deposited on Au, recently studied my XAS and XMCD have shown that there is charge transfer from the substrate to the Fe atom, modifying the electronic structure and magnetic properties [2] [4pt] [1] J. Bartolom'e et al., Phys. Rev. B 81, 195405 (2010) [0pt] [2] S. Stepanow et al., Phys. Rev. B 83, 220401(R) (2011).

Bartolome, Juan

2012-02-01

158

Bone marrow-targeted liposomal carriers  

PubMed Central

Introduction Bone marrow targeted drug delivery systems appear to offer a promising strategy for advancing diagnostic, protective, and/or therapeutic medicine for the hematopoietic system. Liposome technology can provide a drug delivery system with high bone marrow targeting that is mediated by specific phagocytosis in bone marrow. Area covered This review focuses on a bone marrow specific liposome formulation labeled with technetium-99m (99mTc). Interspecies differences in bone marrow distribution of the bone marrow targeted formulation are emphasized. This review provides a liposome technology to target bone marrow. In addition, the selection of proper species for the investigation of bone marrow targeting is suggested. Expert opinion It can be speculated that the bone marrow macrophages have a role in the delivery of lipids to the bone marrow as a source of energy and for membrane biosynthesis or in the delivery of fat soluble vitamins for hematopoiesis. This homeostatic system offers a potent pathway to deliver drugs selectively into bone marrow tissues from blood. High selectivity of the present BMT-liposome formulation for bone marrow suggests the presence of an active and specific mechanism, but specific factors affecting the uptake of the bone marrow MPS are still unknown. Further investigation of this mechanism will increase our understanding of factors required for effective transport of agents to the bone marrow, and may provide an efficient system for bone marrow delivery for therapeutic purposes.

Sou, Keitaro; Goins, Beth; Oyajobi, Babatunde O.; Travi, Bruno L.; Phillips, William T.

2011-01-01

159

Liposomes for drug delivery to mitochondria.  

PubMed

Efficacy of therapeutically active drugs known to act on intracellular targets can be enhanced by specific delivery to the site of action. Triphenylphosphonium cations can be used to create subcellular targeted liposomes that efficiently deliver drugs to mitochondria, thus enhancing their therapeutic action. PMID:20072889

Boddapati, Sarathi V; D'Souza, Gerard G M; Weissig, Volkmar

2010-01-01

160

Nanocomposite liposomes containing quantum dots and anticancer drugs for bioimaging and therapeutic delivery: a comparison of cationic, PEGylated and deformable liposomes  

NASA Astrophysics Data System (ADS)

Multifunctional liposomes loaded with quantum dots (QDs) and anticancer drugs were prepared for simultaneous bioimaging and drug delivery. Different formulations, including cationic, PEGylated and deformable liposomes, were compared for their theranostic efficiency. We had evaluated the physicochemical characteristics of these liposomes. The developed liposomes were examined using experimental platforms of cytotoxicity, cell migration, cellular uptake, in vivo melanoma imaging and drug accumulation in tumors. The average size of various nanocomposite liposomes was found to be 92-134 nm. Transmission electron microscopy confirmed the presence of QDs within liposomal bilayers. The incorporation of polyethylene glycol (PEG) and Span 20 into the liposomes greatly increased the fluidity of the bilayers. The liposomes provided sustained release of camptothecin and irinotecan. The cytotoxicity and cell migration assay demonstrated superior activity of cationic liposomes compared with other carriers. Cationic liposomes also showed a significant fluorescence signal in melanoma cells after internalization. The liposomes were intratumorally administered to a melanoma-bearing mouse. Cationic liposomes showed the brightest fluorescence in tumors, followed by classical liposomes. This signal could last for up to 24 h for cationic nanosystems. Intratumoral accumulation of camptothecin from free control was 35 nmol g-1 it could be increased to 50 nmol g-1 after loading with cationic liposomes. However, encapsulation of irinotecan into liposomes did not further increase intratumoral drug accumulation. Cationic liposomes were preferable to other liposomes as nanocarriers in both bioimaging and therapeutic approaches.

Wen, Chih-Jen; Sung, Calvin T.; Aljuffali, Ibrahim A.; Huang, Yu-Jie; Fang, Jia-You

2013-08-01

161

Cobaltacarborane-phthalocyanine conjugates: Syntheses and photophysical properties  

PubMed Central

Syntheses of two new cobaltacarborane–phthalocyanine conjugates, one anionic (Pc 6) and one zwitterionic (Pc 7), were accomplished via cyclotetramerization of the corresponding cobaltacarborane-substituted phthalonitriles (4 or 5) with excess phthalonitrile in quinoline. X-ray structures of two phthalonitrile precursors (2 and 3) were obtained and are discussed, and the absorption and emission properties of the two cobaltacarborane–phthalocyanine conjugates in several solvents were investigated. The anionic conjugate 6 exists mainly as a monomer in polar organic solvents and has fluorescence quantum yields in the region 0.2–0.3. The zwitterionic conjugate 7 aggregates in solution and displays lower quantum yields ~0.1 in organic solvents.

Li, Hairong; Fronczek, Frank R.; Vicente, M. Graca H.

2010-01-01

162

Optical limiting in solutions of metallo-phthalocyanines and naphthalocyanines  

NASA Technical Reports Server (NTRS)

Optical limiting measurements have been made on solutions of several metal containing phthalocyanines and naphthalocyanines. Measurements at 532nm using nanosecond pulses from a Q-switched Nd:YAG laser show limiting throughputs of 1-10 millijoules with mild focussing in alcohol solutions with nominal transmissions of 30-70 percent. Measurements on chloro-aluminum-phthalocyanine solutions utilizing individual 30 psec pulses or trains (spanning about 100nsec) of modelocked pulses have shown even lower limiting throughputs. Thus, the dynamic range of the limiting behavior has been shown to cover at least three orders of magnitude. Prompt limiting is attributed to strong singlet-singlet (S1-Sn) absorption, whereas the longer time limiting behavior is postulated to result from strong triplet-triplet (T1-Tn) absorption. In addition to these studies, efforts have been underway to identify materials with reduced limiting throughput and improved optical transmission characteristics.

Coulter, Daniel R.; Miskowski, Vincent M.; Perry, Joseph W.; Wei, Tai-Huei; Van Stryland, Eric W.

1989-01-01

163

Electrical Field Effects in Phthalocyanine Film Growth by Vapor Deposition  

NASA Technical Reports Server (NTRS)

Phthalocyanine, an organic material, is a very good candidate for non-linear optical application, such as high-speed switching and optical storage devices. Phthalocyanine films have been synthesized by vapor deposition on quartz substrates. Some substrates were coated with a very thin gold film for introducing electrical field. These films have been characterized by surface morphology, material structure, chemical and thermal stability, non-linear optical parameters, and electrical behaviors. The films have excellent chemical and optical stability. However, the surface of these films grown without electrical field shows flower-like morphology. When films are deposited under an electrical field ( an aligned structure is revealed on the surface. A comparison of the optical and electrical properties and the growth mechanism for these films grown with and without an electrical field will be discussed.

Banks, Curtis E.; Zhu, Shen; Frazier, Donald O.; Penn, Benjamin; Abdeldayem, Hossin; Hicks, Roslin; Sarkisov, Sergey

1999-01-01

164

Elucidating the 3d electronic configuration in manganese phthalocyanine.  

PubMed

To shed light on the metal 3d electronic structure of manganese phthalocyanine, so far controversial, we performed photoelectron measurements both in the gas phase and as thin film. With the purpose of explaining the experimental results,three different electronic configurations close in energy to one another were studied by means of density functional theory. The comparison between the calculated valence band density of states and the measured spectra revealed that in the gas phase the molecules exhibit a mixed electronic configuration, while in the thin film, manganese phthalocyanine finds itself in the theoretically computed ground state, namely, the b1(2g)e3(g)a1(1g)b0(1g) electronic configuration. PMID:24428172

Brumboiu, Iulia Emilia; Totani, Roberta; de Simone, Monica; Coreno, Marcello; Grazioli, Cesare; Lozzi, Luca; Herper, Heike C; Sanyal, Biplab; Eriksson, Olle; Puglia, Carla; Brena, Barbara

2014-02-01

165

Optical limiting behavior of octa-decyloxy metallo-phthalocyanines  

SciTech Connect

One of the key issues involved in the development of passive optical power limiters is the search for appropriate materials that show effective reverse saturable absorption. Metallo-phthalocyanines seem to be good candidates for such applications because of their high optical nonlinearity and their unique electronic absorption characteristics. A series of 1,4,8,11,15,18,22,25-octa-decyloxy metallo-phthalocyanines containing palladium, nickel, cobalt, copper, and zinc as central metal atoms were characterized for their nonlinear absorptive properties to evaluate their suitability to function as reverse saturable absorbers. Nonlinear transmission measurements were analyzed in terms of a five-state model and a simple model based on the effective excited-state absorption cross sections without ascribing their origin to the states involved. Optical limiting thresholds were also estimated and compared with the absorption cross sections. {copyright} 2001 American Institute of Physics.

Sanghadasa, Mohan; Shin, In-Seok; Clark, Ronald D.; Guo, Huaisong; Penn, Benjamin G.

2001-07-01

166

Magnetic Relaxation in Iron Chains of Phthalocyanine Thin Films  

NASA Astrophysics Data System (ADS)

Self-assembled iron chains are formed in metallo-organic thin films based on the small iron phthalocyanine molecule. The chains are grown parallel to the substrate and the mean chain length is controlled via deposition parameters from 30 -- 300 nm. The strong intra-chain coupling with weak inter-chain coupling leads to ferromagnetic behavior below the critical temperature. After application of a magnetic saturation field, the remanent magnetic moment is not stable when measured over time scales of 10^4 s. The magnetic relaxation can be fit to a stretched exponential function, which yields the mean relaxation time and a stretch exponent. The temperature-dependent peak of the relaxation time occurs at lower temperatures for shorter iron chains that also have smaller coercivities. This means that by templating iron phthalocyanine thin films both magneto-crystalline anisotropy and inter-grain interactions can be selected.

Gredig, Thomas; Javier, Daniel; Werber, Mathew; Byrne, Matthew

2013-03-01

167

Phthalocyanine photoelectrochemical cell prepared by a micelle disruption method  

SciTech Connect

Photoelectrochemical characteristics of a metal-free phthalocyanine electrode prepared by a micelle disruption method are described. The novel technique is found to provide more photoactive phthalocyanine layers on indium tin oxide (ITO), compared with a vacuum sublimation technique. A short-circuit photocurrent of 0.1 mA cm/sup -2/ is obtained for the ITO/H/sub 2/ Pc(MD)/I/sup -//sub 3/ -I/sup -//Pt cell under the white light illumination of 6 mW cm/sup -2/, together with an open-circuit photovoltage of 70 mV and a fill factor of 0.42. These data lead to a value of 0.06% for the energy conversion efficiency.

Harima, Y.; Yamashita, K.; Saji, T.

1988-05-02

168

Photoelectrochemistry of some aluminum phthalocyanines in regenerative solar cells  

SciTech Connect

Chloroaluminum phthalocyanine (ClAlPc) films sublimed with a high growth rate on SnO/sub 2/ can be made to undergo two transformations when the films are in contact with an acidic (HCl) aqueous solution: transformation I is obtained if the solution contains I/sub 3//I and transformation H occurs when there is no redox couple in the solution. The short-circuit photocurrents produced by these two transformations are different. The highest J/sub sc/(1.1 mA cm/sup -2/), under 100 mW cm/sup -2/ white light illumination, was measured for transformation I. An investigation of the differences between the initial and the highly photoactive film shows that transformation I induces the growth of an 840 nm band in both absorption and action spectra. Moreover, IR spectroscopy suggests that there is a possible protonation of a peripheral nitrogen of the phthalocyanine macrocycle.

Guay, D.; Dodelet, J.P. (INRS-Energie, Varennes, Quebec (CA)); Cote, R.; Langford, C.H. (Chemistry Dept., Concordia Univ., Montreal, Quebec (CA)); Gravel, D. (Dept. de chimie, Univ. de Montreal, Montreal, Quebec (CA))

1989-08-01

169

Assembling photosensitive capsules by phthalocyanines and polyelectrolytes for photodynamic therapy  

Microsoft Academic Search

A photosensitive capsule consisting of aluminum phthalocyanine tetrasulfonate chloride (AlPcS4Cl) and polyelectrolytes was fabricated by assembling of oppositely charged poly(allylamine hydrochloride) (PAH) and AlPcS4Cl onto the preformed capsules composed of poly(styrene sulfonate) (PSS) and PAH. UV–visible absorption spectra, EDX spectrum and AFM images confirmed the successful deposition of AlPcS4Cl onto as-prepared hollow capsules. The assembled photosensitive capsules were found to

Yu Zeng; Xiao-Lei Wang; Yun-Jie Yang; Jian-Feng Chen; Jiwen Fu; Xia Tao

2011-01-01

170

DFT Modeling and Experiments on Phthalocyanines Field-Effect Transistors  

NASA Astrophysics Data System (ADS)

We present the possible construction of organic FET-like photoactive device in which source-drain current through phthalocyanine (H2Pc) film is affected by photo-induced dipolar field in a photoactive ``gate'' electrode. The influence of the dipolar electric field on charge transfer between H2Pc molecules, is modeled by DFT quantum chemical calculations on H2Pc dimers and tetramers.

Kratochvílová, I.; Nešpu?Rek, S.; Šebera, J.; Záliš, S.; Pavelka, M.; Wang, G.; Sworakowski, J.

2009-08-01

171

Resonance Raman spectra of. cap alpha. -copper phthalocyanine  

Microsoft Academic Search

Raman spectra of ..cap alpha..-copper phthalocyanine (..cap alpha..-CuPc) were recorded at room temperature and at 10 K with excitation wavelengths between 457 and 714 nm. Resonance enhancement was greatest for modes for which the largest displacements were on either the inner five-membered ring of the isoindole groups or the inner macrocycle and consequently assignment of the bands to modes of

A. J. Bovill; A. A. McConnell; J. A. Nimmo; W. E. Smith

1986-01-01

172

The production of copper phthalocyanine and/or its derivatives  

NASA Technical Reports Server (NTRS)

This document discusses the production of copper phthalocyanine and/or its derivatives, which are useful for dye pigments. The method described uses urea, a copper compound and/or a catalyst which have been suspended in an inert reaction medium. The copper compound, catalyst and urea fused and the reaction is performed by using the obtained fusion. The advantages of the invention are listed.

Segawa, T.; Matsuzaki, K.; Sawada, H.; Ninomiya, R.; Suyama, M.

1984-01-01

173

Characterization of electrochemically polymerized metal phthalocyanines using Rutherford backscattering spectrometry  

Microsoft Academic Search

A new electrochemical polymerization method for producing electronically conductive thin films of metal phthalocyanines has been developed. The thickness and stoichiometric composition of nickelphthalocyanine films produced with this technique have been measured using Rutherford backscattering spectrometry. The film thickness is directly proportional to the number of polymerization cycles in the thickness range of 100-2000 (1015 atoms\\/cm2). Diffusion of the solvent,

E. M. Baum; H. Li; T. F. Guarr; J. D. Robertson

1991-01-01

174

Characterization of loaded liposomes by size exclusion chromatography.  

PubMed

This review focuses on the use of conventional (SEC) and high performance (HPSEC) size exclusion chromatography for the analysis of liposomes. The suitability of both techniques is examined regarding the field of liposome applications. The potentiality of conventional SEC is strongly improved by using a HPLC system associated to gel columns with a size selectivity range allowing liposome characterization in addition to particle fractionation. Practical aspects of size exclusion chromatography are described and a methodology based on HPSEC coupled to multidetection modes for on-line analysis of liposomes via label or substance encapsulation is presented. Examples of conventional SEC and HPSEC applications are described which concern polydispersity, size and encapsulation stability, bilayer permeabilization, liposome formation and reconstitution, incorporation of amphiphilic molecules. Size exclusion chromatography is a simple and powerful technique for investigation of encapsulation, insertion/interaction of substances from small solutes (ions, surfactants, drugs, etc.) up to large molecules (proteins, peptides and nucleic acids) in liposomes. PMID:12834977

Grabielle-Madelmont, Cécile; Lesieur, Sylviane; Ollivon, Michel

2003-06-30

175

Optical absorption studies of copper phthalocyanine thin films  

NASA Astrophysics Data System (ADS)

The optical absorption of thermally evaporated copper phthalocyanine (CuPc) was studied in the UV-VIS-NIR region. The absorption spectra recorded in the UV-VIS region show two well-defined absorption bands of the phthalocyanine molecules, namely, the Soret ( B) and the Q-band . The Q-band shows its characteristic splitting (Davydov splitting) of the main absorption peak in the metal phthalocyanine correlates with the relative tendencies of the metal to out-of-plane bonding. Some of the important spectral characteristics such as the molar extinction coefficient (? molar), the oscillator strength ( f), the electric dipole strength ( q2) and absorption half-bandwidth (? ?) of the principle optical transitions were evaluated. The analysis of the spectral behavior of the absorption coefficient ? in the absorption region revealed two indirect allowed transitions with corresponding energies 2.95±0.03 and 1.55±0.02 eV. The spectra of the infrared absorption allow characterization of vibration modes for the powder, as-deposited material and thin films of CuPc annealed at 423 K for two hours. Discussion of the obtained results and their comparison with the previous published data are also given.

Farag, A. A. M.

2007-06-01

176

Localized orbital study on the electronic structure of phthalocyanine dimers  

SciTech Connect

The lowest excited state of lanthanide phthalocyanine dimer and {mu}-oxo silicon phthalocyanine dimer are studied by configuration interaction calculations on the localized orbital basis set obtained by a unitary transformation of semiempirical SCMOs of the dimers. The model can characterize the dimer excited states as a superposition of intraligand and interligand excitation. The higher energy component band in the Q band region of the lanthanide dimer complexes is ascribed to an excitation in the excited state essentially of the exciton coupling state, while the lower energy component band is assigned as an excitation to that of the charge resonance state, which is granted a spectral intensity from the exciton component. A rapid decrease in the splitting of the Q band of the dimers with increasing radius of the central lanthanide ion is attributable to a pronounced decrease in the difference of diagonal energies of charge transfer and local excitation configurations and the off-diagonal interaction between the two configurations. Theory can well reproduce the dimer spectra of Q band with a reduced interplanar two-electron interaction ({alpha} = 0.8). On the other hand, the dimer spectra in B band region are obtained only with an enhanced interplanar interaction ({alpha} = 1.0-1.2). A broadening of the band in the Q band region of the silicon complex dimer is attributed to an internal rotation of phthalocyanine macrocycles around their C{sub 4} symmetry axis. 44 refs., 7 figs., 3 tabs.

Ishikawa, Naoto; Ohno, Osamu; Kaizu, Youkoh; Kobayashi, Hiroshi [Tokyo Institute of Technology (Japan)

1992-10-29

177

Liposome-mediated DNA vaccination: the effect of vesicle composition  

Microsoft Academic Search

Liposome-entrapped DNA has been shown to enhance the potency of DNA vaccines, possibly by facilitating uptake of the plasmid by antigen-presenting cells (APC). In this paper, we have investigated the influence of the liposomal composition and surface charge on such potency. Plasmid DNA pRc\\/CMV HBS encoding the S (small) region of hepatitis B surface antigen was entrapped within cationic liposomes

Yvonne Perrie; Peter M. Frederik; Gregory Gregoriadis

2001-01-01

178

[Novel possibilities of development and therapeutical application of liposomes].  

PubMed

Properties and possibilities of application of liposomal drug delivery systems are summarized in this review. Technological and biopharmeceutical criteria that have to be taken into consideration in the course of development of biocompatible liposomes are discussed. The manner and possibilities of active and passive targeting are shown according to the literary data and special liposome-based drug delivery systems responsible for pathologic or arteficial stimuli are introduced. PMID:18986087

Bozó, Tamás; Pál, Szilárd; Dévay, Attila

2008-01-01

179

Endocytosis and intracellular processing accompanying transfection mediated by cationic liposomes  

Microsoft Academic Search

Cationic liposomes mediate efficient transfection of mammalian cells, but the manner in which cells internalize and process cationic liposome-DNA complexes has not been well characterized. We exposed several cell types, including human and murine erythroleukemia cells, African green monkey kidney cells (CV-1), isolated rat alveolar type II cells and alveolar macrophages to DNA-cationic liposome complexes containing N-(1-2,3-dioleyloxypropyl)-N,N,N-triethylammonium (DOTMA) and Dioleylphosphatidylethanolamine

Daniel S Friend; Demetrios Papahadjopoulos; Robert J Debs

1996-01-01

180

Targeting Anticancer Drugs to Tumor Vasculature Using Cationic Liposomes  

Microsoft Academic Search

Liposomal drug delivery systems improve the therapeutic index of chemotherapeutic agents, and the use of cationic liposomes\\u000a to deliver anticancer drugs to solid tumors has recently been recognized as a promising therapeutic strategy to improve the\\u000a effectiveness of conventional chemotherapeutics. This review summarizes the selective targeting of cationic liposomes to tumor\\u000a vasculature, the merits of incorporating the polymer polyethylene-glycol (PEG),

Amr S. Abu Lila; Tatsuhiro Ishida; Hiroshi Kiwada

2010-01-01

181

Determination of the absorption and scattering cross sections of zinc phthalocyanine nanoparticles  

NASA Astrophysics Data System (ADS)

The real and imaginary parts of the refractive index of thin zinc phthalocyanine films have been measured by two different methods (spectral and ellipsometric). The results obtained have been used to calculate the absorption and scattering cross sections of spherical zinc phthalocyanine nanoparticles in water as functions of their size.

Malimonenko, N. V.; Dudkin, V. S.; Kogan, B. Ya.

2014-03-01

182

Inhomogeneous broadening of the zero phonon line of phthalocyanine in superfluid helium droplets  

Microsoft Academic Search

The electronic origin band of the S1<--S0 transition of monomer phthalocyanine doped into liquid helium droplets consist of a single zero phonon line (ZPL) and a structured phonon wing. The latter reflects the low frequency modes of the helium droplet. At very high resolution (1 MHz) the asymmetric spectrum of the ZPL of phthalocyanine provides no indication of a rotational

Alkwin Slenczka; Bernhard Dick; Matthias Hartmann; J. Peter Toennies

2001-01-01

183

Preparation and photoelectrical properties of poly(phenylethanone)-Znic phthalocyanine derivative  

Microsoft Academic Search

A phthalocyanine derivative of poly (phenylethanone)-Znic phthalocyanine (PPE-ZnPc) with excellent film-forming property was synthesized and characterized. The photoconductivity of PPE-ZnPc increased about 6 times compared with dark conductivity, indicating that PPE-ZnPc has good photovoltaic response.

Huina Lu; Yue Shen; Feng Gu; Fei Zheng; Qi Ying; Jiancheng Zhang

2009-01-01

184

Novel, soluble, FluXoro functional substituted zinc phthalocyanines; synthesis, characterization and photophysicochemical properties  

Microsoft Academic Search

Three novel phthalonitriles and the respective, peripheral tetrakis zinc phthalocyanines were synthesized and characterized using elemental analysis, IR, 1H NMR, mass spectra and electronic spectroscopy. The phthalocyanines displayed good solubility in organic solvents such as CHCl3, DCM, DMSO, DMF, THF and toluene. The presence of a long chain fluorine substitituent was found to result in reduced aggregation. The singlet oxygen,

Ali Erdo?mu?; Tebello Nyokong

2010-01-01

185

Preparation and properties of octa-substituted phthalocyanines peripherally substituted with phenyl derivatives  

Microsoft Academic Search

2,3,9,10,16,17,23,24-Octa-substituted phthalocyanines modified with phenyl, tolyl, tert-butylphenyl, and trifluoromethylphenyl groups and their nickel(II) complexes were prepared and characterized. The phthalonitriles with the phenyl derivatives, which are precursors of the phthalocyanines, were synthesized from 4,5-dichlorophthalonitrile and phenyl boronic acids by use of Suzuki-coupling reaction.

Tamotsu Sugimori; Masaharu Torikata; Jun Nojima; Shinobu Tominaka; Kaori Tobikawa; Makoto Handa; Kuninobu Kasuga

2002-01-01

186

Increased Liposome Extravasation in Selected Tissues: Effect of Substance P  

NASA Astrophysics Data System (ADS)

We have used a pharmacologic mediator to open intercellular connections in selected vessels to allow liposomes to escape from the blood stream and to extravasate into tissues that have appropriate receptors. We have examined the effects of substance P (SP), a peptide known to increase vascular permeability in selected tissues, such as trachea, esophagus, and urinary bladder in rats. We used quantitative fluorescence analysis of tissues to measure two fluorescent markers, one attached to the lipid (rhodamine-phosphatidylethanolamine) and another, doxorubicin (an antitumor drug), encapsulated within the aqueous interior. We have also examined the deposition of liposomes microscopically by the use of encapsulated colloidal gold and silver enhancement. Analysis of the biochemical and morphological observations indicate the following: (i) Injection of SP produces a striking increase in both liposome labels, but only in tissues that possess receptors for SP in postcapillary venules; (ii) liposome material in these tissues has extravasated and is found extracellularly near a variety of cells beyond the endothelial layer over the first few hours; (iii) 24 h following injection of liposomes and SP, liposome material is found in these tissues, localized intracellularly in both endothelial cells and macrophages. We propose that appropriate application of tissue-specific mediators can result in liposome extravasation deep within tissues that normally do not take up significant amounts of liposomes from the blood. Such liposomes are able to carry a variety of pharmacological agents that can be released locally within selected target tissues for therapeutic purposes.

Rosenecker, Joseph; Zhang, Weiming; Hong, Keelung; Lausier, James; Geppetti, Pierangelo; Yoshihara, Shigemi; Papahadjopoulos, Demetrios; Nadel, Jay A.

1996-07-01

187

Current trends in the use of liposomes for tumor targeting  

PubMed Central

The use of liposomes for drug delivery began early in the history of pharmaceutical nanocarriers. These nanosized, lipid bilayered vesicles have become popular as drug delivery systems owing to their efficiency, biocompatibility, nonimmunogenicity, enhanced solubility of chemotherapeutic agents and their ability to encapsulate a wide array of drugs. Passive and ligand-mediated active targeting promote tumor specificity with diminished adverse off-target effects. The current field of liposomes focuses on both clinical and diagnostic applications. Recent efforts have concentrated on the development of multifunctional liposomes that target cells and cellular organelles with a single delivery system. This review discusses the recent advances in liposome research in tumor targeting.

Deshpande, Pranali P; Biswas, Swati; Torchilin, Vladimir P

2013-01-01

188

Paramagnetic Liposome Nanoparticles for Cellular and Tumour Imaging  

PubMed Central

In this review we discuss the development of paramagnetic liposomes incorporating MRI contrast agents and show how these are utilized in cellular imaging in vitro. Bi-functional, bi-modal imaging paramagnetic liposome systems are also described. Next we discuss the upgrading of paramagnetic liposomes into bi-modal imaging neutral nanoparticles for in vivo imaging applications. We discuss the development of such systems and show how paramagnetic liposomes and imaging nanoparticles could be developed as platforms for future multi-functional, multi-modal imaging theranostic nanodevices tailor-made for the combined imaging of early stage disease pathology and functional drug delivery.

Kamaly, Nazila; Miller, Andrew D.

2010-01-01

189

Adsorbed liposome deformation studied with quartz crystal microbalance  

NASA Astrophysics Data System (ADS)

Deformation of surface-adsorbed liposomes is an important parameter that governs the kinetics of their transformations, but one that is very difficult to measure in the case of nm-size liposomes. We investigate the deformation of dimyristoyl phosphatidyl choline liposomes by quartz crystal microbalance (QCM) as a function of temperature and show that it follows the dependence of this lipid's bending modulus on temperature, as expected from theoretical considerations. To corroborate our approach, we model QCM response from adsorbed liposomes by explicitly considering their shape and mechanical properties.

Reviakine, Ilya; Gallego, Marta; Johannsmann, Diethelm; Tellechea, Edurne

2012-02-01

190

Liposomal nanoparticles encapsulating iloprost exhibit enhanced vasodilation in pulmonary arteries  

PubMed Central

Prostacyclin analogues are standard therapeutic options for vasoconstrictive diseases, including pulmonary hypertension and Raynaud’s phenomenon. Although effective, these treatment strategies are expensive and have several side effects. To improve drug efficiency, we tested liposomal nanoparticles as carrier systems. In this study, we synthesized liposomal nanoparticles tailored for the prostacyclin analogue iloprost and evaluated their pharmacologic efficacy on mouse intrapulmonary arteries, using a wire myograph. The use of cationic lipids, stearylamine, or 1,2-di-(9Z-octadecenoyl)-3-trimethylammonium-propane (DOTAP) in liposomes promoted iloprost encapsulation to at least 50%. The addition of cholesterol modestly reduced iloprost encapsulation. The liposomal nanoparticle formulations were tested for toxicity and pharmacologic efficacy in vivo and ex vivo, respectively. The liposomes did not affect the viability of human pulmonary artery smooth muscle cells. Compared with an equivalent concentration of free iloprost, four out of the six polymer-coated liposomal formulations exhibited significantly enhanced vasodilation of mouse pulmonary arteries. Iloprost that was encapsulated in liposomes containing the polymer polyethylene glycol exhibited concentration-dependent relaxation of arteries. Strikingly, half the concentration of iloprost in liposomes elicited similar pharmacologic efficacy as nonencapsulated iloprost. Cationic liposomes can encapsulate iloprost with high efficacy and can serve as potential iloprost carriers to improve its therapeutic efficacy.

Jain, Pritesh P; Leber, Regina; Nagaraj, Chandran; Leitinger, Gerd; Lehofer, Bernhard; Olschewski, Horst; Olschewski, Andrea; Prassl, Ruth; Marsh, Leigh M

2014-01-01

191

Size dependence of protein-induced flocculation of phosphatidylcholine liposomes  

NASA Astrophysics Data System (ADS)

The adsorption of lysozyme and cytochrome C on phosphatidylcholine liposomes essentially changes the physical properties of the phospholipid membranes and under certain circumstances greatly affects the stability of the colloid dispersion by inducing bridging liposome flocculation. This study was designed to examine experimentally the influence of liposome size on two kinetic parameters of the flocculation, its rate constant and activation energy. As the liposome radius increased in the range 50-500 nm, the activation energy tended to decrease, resulting in an increased flocculation rate, except for the flocculation of 400-nm liposomes, which was greatly impeded. The pronounced influence of the liposome size on the flocculation rate constant was evident, since a well-defined minimum in the kinetic rate of flocculation of 400-nm liposomes was detected experimentally. The obtained nonlinear radius dependencies of the flocculation rates and activation energies are interpreted in terms of the bridging mechanism of the protein-induced liposome flocculation and the supplementary concept of the stability of thin liquid films formed between approaching protein-adsorbed liposomes.

Dimitrova, M. N.; Tsekov, R.; Matsumura, H.; Furusawa, K.

2000-06-01

192

Preparation and evaluation of liposome-encapsulated codrug LMX.  

PubMed

A novel codrug (LMX) consisting of Lamivudine and Ursolic acid has been shown to possess the dual action of anti-hepatitis B virus activity and hepatoprotective effects against acute liver injury in vivo. Because of the limited water solubility of LMX, our aims were to design and optimize a liposomal formulation that could facilitate its in vivo administration, and to estimate the potential of LMX-loaded liposomes as oral or intravenous delivery system. In this work, LMX-loaded liposomes were prepared by the thin film hydration method coupled with sonication. LMX-loaded liposomes showed spherical morphology under transmission electron microscope (TEM) analysis. The mean particle size of liposomes was about 210 nm, and the drug entrapment efficiency was more than 90%. Stability data indicated that lyophilized liposomes were stable for at least 6 months at 4 °C. In vitro drug release profile of LMX-loaded liposomes showed a sustained release profile of LMX and an initial mild burst was observed. The relative bioavailability of LMX-loaded liposomes was 1074.8% compared with LMX suspension after oral administration, and 135.2% relative to 50% alcohol solution after intravenous (i.v.) administration. These results indicated that LMX-loaded liposomes were valued to develop as a practical preparation for oral or i.v. administration. PMID:22981689

Zhong, Yan; Wang, Jing; Wang, Yao; Wu, Bin

2012-11-15

193

Modifying the release properties of liposomes toward personalized medicine.  

PubMed

Surfactant-liposome interactions have historically been investigated as a simplified model of solubilization and breakdown of biological membranes by surfactants. In contrast, our goal was to utilize surfactants to modify the encapsulation and release properties of liposomes. The ability to manufacture one liposomal formulation, which could be modified by the addition of a surfactant to support a wide range of release profiles, would provide greater flexibility than manufacturing multiple batches of liposomes, each differing in composition and with its own specific release profile. A liposomal ciprofloxacin formulation was modified by the addition of various surfactants. These formulations were characterized in terms of liposome structure by cryo-TEM imaging, vesicle size by dynamic light scattering, drug encapsulation by centrifugation-filtration, and in vitro release (IVR) performance. The addition of polysorbate 20 or polysorbate 80 to liposomal ciprofloxacin, in a hypotonic environment, resulted in a concentration-dependent loss of encapsulated drug, and above 0.4% polysorbate 20, or 0.2% polysorbate 80, a modified IVR profile as well. This study demonstrates that the encapsulation and release properties of a liposomal formulation can be modified postmanufacture by the addition of judiciously chosen surfactants in combination with osmotic swelling of the liposomes and may support a personalized approach to treating patients. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci. PMID:24715635

Cipolla, David; Wu, Huiying; Gonda, Igor; Eastman, Simon; Redelmeier, Tom; Chan, Hak-Kim

2014-06-01

194

Mechanism of Oligonucleotide Release from Cationic Liposomes  

Microsoft Academic Search

We propose a mechanism for oligonucleotide (ODN) release from cationic lipid complexes in cells that accounts for various observations on cationic lipid-nucleic acid-cell interactions. Fluorescent confocal microscopy of cells treated with rhodamine-labeled cationic liposome\\/fluorescein-labeled ODN (F-ODN) complexes show the F-ODN separates from the lipid after internalization and enters the nucleus leaving the fluorescent lipid in cytoplasmic structures. ODN displacement from

Olivier Zelphati; Francis C. Szoka

1996-01-01

195

Liposomes and lipopolymeric carriers for gene delivery.  

PubMed

In this work we have examined the ability of various lipopolyplexes to deliver genes into liver cancer cells. We evaluated different parameters such as the protocol of preparation, the lipid/DNA molar ratio, and the molecular weight and type of PEI, to optimize the formulation to achieve high transfection activity. Our hypothesis was that the association of PEI with cationic liposomes (lipopolyplexes) would increase luciferase expression compared to lipoplexes (cationic lipid and DNA) and polyplexes (cationic polymer and DNA) alone. PMID:20923400

Tros de Ilarduya, Conchita; García, Leire; Düzgünes, Nejat

2010-01-01

196

Secretory Phospholipase A2 Responsive Liposomes  

PubMed Central

Secretory phospholipase A2 (sPLA2) expression is increased in several cancers and has been shown to trigger release from some lipid carriers. This study used electrospray ionization mass spectrometry (ESI-MS) and release of 6-carboxyfluorescein (6-CF) to determine the effects of sPLA2 on various liposome formulations. Different combinations of zwitterionic [1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine, 1,2-distearoyl-sn-glycero-3-phosphatidylcholine, and 1,2- distearoyl-sn-glycero-3-phosphatidylethanolamine (DSPE)] and anionic [1,2-distearoyl-sn-glycero-3-phosphatidic acid, 1,2-distearoyl-sn-glycero-3-phosphatidylglycerol (DSPG), 1,2-distearoyl-sn-glycero-3-phosphatidylserine, and 1,2-distearoyl-sn-glycero-3-phosphoethanolamine–N-poly(ethylene glycol) 2000 (DSPE–PEG)] phospholipids were examined. DSPG and DSPE were most susceptible to sPLA2-mediated degradation compared with other phospholipids. Increased 6-CF release was observed after inclusion of 10 mol % DSPE and anionic lipids into different liposome formulations. Group IIa sPLA2-mediated 6-CF release was less than Group III and relatively insensitive to cholesterol (Chol), whereas Chol reduced sPLA2-mediated release. Inclusion of DSPE–PEG increased sPLA2-mediated 6-CF release, whereas serum reduced lipid degradation and 6-CF release significantly. These data demonstrate that ESI-MS and 6-CF release were useful in determining the selectivity of sPLA2 and release from liposomes, that differences in the activity of different sPLA2 isoforms exist, and that DSPE–PEG enhanced sPLA2-mediated release of liposomal constituents. These findings will aid in the selection of lipids and optimization of the kinetics of drug release for the treatment of cancers and diseases of inflammation in which sPLA2 expression is increased.

ZHU, GUODONG; MOCK, JASON N.; ALJUFFALI, IBRAHIM; CUMMINGS, BRIAN S.; ARNOLD, ROBERT D.

2011-01-01

197

Photochemistry of transition-metal phthalocyanines. Mechanistic aspects of the photochemistry of the acido(phthalocyanine)rhodium(III) complexes investigated by continuous, flash, and laser flash photolysis  

SciTech Connect

Rh(ph)(CH/sub 3/OH)X, X = Cl, Br, or I, has been prepared and characterized. Continuous-wave irradiations of these phthalocyanines in the ultraviolet region of the spectrum, in acetonitrile and acetonitrile-isopropyl alcohol mixtures, result in the redox-induced substitution of the axially coordinated halide ions by the solvent. Even though the overall reaction was photosubstitution, the intermediates observed by conventional and laser flash photolysis were found to be rhodium(II) phthalocyanine and rhodium(III) phthalocyanine ligand radicals. The photoredox processes were attributed to the population of (n..pi..*) ligand-centered excited states that involve the lone electron pair from the bridge nitrogens of the phthalocyanine ligand. 9 figures, 3 tables.

Muralidharan, S.; Ferraudi, G.; Schmatz, K.

1982-08-01

198

Phototriggerable Liposomes: Current Research and Future Perspectives  

PubMed Central

The field of cancer nanomedicine is considered a promising area for improved delivery of bioactive molecules including drugs, pharmaceutical agents and nucleic acids. Among these, drug delivery technology has made discernible progress in recent years and the areas that warrant further focus and consideration towards technological developments have also been recognized. Development of viable methods for on-demand spatial and temporal release of entrapped drugs from the nanocarriers is an arena that is likely to enhance the clinical suitability of drug-loaded nanocarriers. One such approach, which utilizes light as the external stimulus to disrupt and/or destabilize drug-loaded nanoparticles, will be the discussion platform of this article. Although several phototriggerable nanocarriers are currently under development, I will limit this review to the phototriggerable liposomes that have demonstrated promise in the cell culture systems at least (but not the last). The topics covered in this review include (i) a brief summary of various phototriggerable nanocarriers; (ii) an overview of the application of liposomes to deliver payload of photosensitizers and associated technologies; (iii) the design considerations of photoactivable lipid molecules and the chemical considerations and mechanisms of phototriggering of liposomal lipids; (iv) limitations and future directions for in vivo, clinically viable triggered drug delivery approaches and potential novel photoactivation strategies will be discussed.

Puri, Anu

2013-01-01

199

Effect of lipid composition and liposome size on toxicity and in vitro fungicidal activity of liposome-intercalated amphotericin B.  

PubMed

Intercalation of amphotericin B into liposomes at a 10 mol% drug/lipid ratio decreased its cytotoxicity by 3- to 90-fold in cultured murine cells and reduced its lethality by 2- to 8-fold in a median lethal dose (LD50) test in mice when compared with the commercial deoxycholate-solubilized drug (LD50 = 2.3 mg/kg). The cytotoxicity and lethality of the liposomal preparations were a function of their lipid composition and diameter. There was no correlation between the reduction of toxicity in the tissue culture assay and the reduction of lethality in the LD50 test. The rank order of reduction of lethality was sterol-containing liposomes greater than solid liposomes greater than fluid liposomes. In general, small sterol-containing vesicles were less lethal than large vesicles of the same composition. Intercalation of amphotericin B in sterol or solid liposomes increased not only the LD50 but also the time to death. The organ distribution of amphotericin B 24 h after intravenous administration was similar whether the drug was given as the commercial deoxycholate preparation or in liposomes. Finally, there were no differences among any of the formulations in their fungicidal activity against Candida tropicalis and Saccharomyces cerevisiae in vitro. The lesser and slower lethality of the liposomal and detergent-solubilized drug suggests that the mechanism by which liposomes reduce the lethality of amphotericin B is by slowing its rate of transfer to a sensitive cellular target. PMID:3579259

Szoka, F C; Milholland, D; Barza, M

1987-03-01

200

Targeting of liposome-associated calcipotriol to the skin: effect of liposomal membrane fluidity and skin barrier integrity.  

PubMed

Many dermal diseases like psoriasis are characterized by major changes in skin barrier function, which challenge the reproducible delivery of drugs into specific layers of diseased skin. The purpose of this study was to elucidate how liposomal bilayer fluidity and barrier integrity affected the delivery of liposome-associated calcipotriol to the skin. Calcipotriol-containing gel state and liquid state dipalmitoylphosphatidyl-choline:dilauroylphosphatidylcholine liposomes were prepared by extrusion. Using Langmuir monolayers, calcipotriol was shown to affect the packing of the lipid membrane. The penetration of radioactively labeled lipid and calcipotriol into pig skin was examined using the Franz diffusion cell model, and tape stripping was applied to impose an impaired barrier. Distorting the skin barrier resulted in an enhanced penetration of lipid from both gel and liquid state liposomes. In addition, increased penetration of lipid from liquid state liposomes was observed compared to gel state liposomes into barrier-impaired skin. For barrier-impaired skin, an elevated calcipotriol-to-lipid ratio was found in the receptor fluid for both liposome compositions indicating that calcipotriol is released from the vesicles. This suggests that the liposome-mediated delivery of calcipotriol to the epidermis of diseased skin is affected by the fluidity of the liposomal membrane. PMID:21419203

Knudsen, Nina Østergaard; Jorgensen, Lene; Hansen, Jens; Vermehren, Charlotte; Frokjaer, Sven; Foged, Camilla

2011-09-20

201

Liposomal nanoparticles as a drug delivery vehicle against osteosarcoma  

NASA Astrophysics Data System (ADS)

The delivery of curcumin, a broad-spectrum anticancer drug, has been explored in the form of liposomal nanoparticles to treat osteosarcoma (OS). Curcumin is water insoluble and an effective delivery route is through encapsulation in cyclodextrins followed by a second encapsulation in liposomes. Liposomal curcumin's potential was evaluated against cancer models of mesenchymal (OS) and epithelial origin (breast cancer). The resulting 2-Hydroxypropyl-gamma-cyclodextrin/curcumin - liposome complex shows promising anticancer potential both in vitro and in vivo against KHOS OS cell line and MCF-7 breast cancer cell line. An interesting aspect is that liposomal curcumin initiates the caspase cascade that leads to apoptotic cell death in vitro in comparison with DMSO-curcumin induced autophagic cell death. In addition, the efficiency of the liposomal curcumin formulation was confirmed in vivo using a xenograft OS model. Curcumin-loaded gamma-cyclodextrin liposomes indicate significant potential as delivery vehicles for the treatment of cancers of different tissue origin. The second part of this study examines the anti-tumor potential of curcumin and C6 ceramide (C6) against osteosarcoma cell lines when both are encapsulated in the bilayer of liposomal nanoparticles. Curcumin in combination with C6 showed 1.5 times enhanced cytotoxic effect in the case of MG-63 and KHOS OS cell lines, in comparison with systems with curcumin alone. Interestingly, C6-curcumin liposomes were found to be less toxic on untransformed human cells in comparison to OS cell lines. In addition, cell cycle assays on a KHOS cell line after treatment revealed that curcumin only liposomes induced G 2/M arrest by upregulation of cyclin B1, while C6 only liposomes induced G1 arrest by downregulation of cyclin D1. C6-curcumin liposomes induced G2/M arrest and showed a combined effect in the expression levels of cyclin D1 and cyclin B1. Using pegylated liposomes to increase the plasma half-life and tagging with folate for targeted delivery in vivo, a significant reduction in tumor size was observed with C6-curcumin-folate liposomes. The encapsulation of two water insoluble drugs, curcumin and C6, in the lipid bilayer of liposomes enhances the cytotoxic effect and validates the potential of combined drug therapy.

Dhule, Santosh Subhashrao

202

Treatment of visceral leishmaniasis in children with liposomal amphotericin B  

Microsoft Academic Search

We used liposomal amphotericin B as first-choice treatment of visceral leishmaniasis in 106 immunocompetent children who acquired the infection in a temperate region of southern Europe (Italy) where Leishmania infantum visceral leishmaniasis is endemic. The aim of the study was to identify the minimum total dose of liposomal amphotericin B needed to cure the infection in children and reduce the

Lucio di Martino; Robert N. Davidson; Raffella Giacchino; Silvestro Scotti; Francesco Raimondi; Elio Castagnola; Loredana Tasso; Antonio Cascio; Luigi Gradoni; Marina Gramiccia; Massimo Pettoello-Mantovani; Anthony D. M. Bryceson

1997-01-01

203

Optically guided controlled release from liposomes with tunable plasmonic nanobubbles  

Microsoft Academic Search

A new method of optically guided controlled release was experimentally evaluated with liposomes containing a molecular load and gold nanoparticles (NPs). NPs were exposed to short laser pulses to induce transient vapor bubbles around the NPs, plasmonic nanobubbles, in order to disrupt the liposome and eject its molecular contents. The release efficacy was tuned by varying the lifetime and size

Lindsey J. E. Anderson; Eric Hansen; Ekaterina Y. Lukianova-Hleb; Jason H. Hafner; Dmitri O. Lapotko

2010-01-01

204

Nerve growth factor-mediated targeting of liposomes to cells  

SciTech Connect

Derivatives of beta-nerve growth factor (NGF), modified by biotinylation of carboxyl groups, were used to target the specific binding of liposomes to cultured rat and human cells bearing NGF receptors. Streptavidin was conjugated via peptide bonds to amino groups on liposomes. Biotinylated NGF, but not unmodified NGF, mediated the binding of radiolabeled streptavidin-liposomes to rat pheochromocytoma PC12 cells in suspension at 4/sup 0/C. In contrast, biotinylated NGF did not increase the binding of hemoglobin-conjugated liposomes tested as a control for specificity. Biotinylated NGF also mediated the specific binding of streptavidin-liposomes containing fluorescein isothiocyanate-labeled dextran to PC12 cells and human melanoma HS294 cells. When HS294 cells were incubated at 37/sup 0/C following liposome binding at 4/sup 0/C, the cell-associated fluorescence appeared to become internalized, in that some cells displayed a perinuclear pattern of fluorescence similar to that observed when lysosomes were stained with acridine orange. Trypsin treatment abolished cell-associated fluorescence when cells were held at 4/sup 0/C but did not affect the fluorescence in cells following incubation at 37/sup 0/C. When liposomes containing carboxyfluorescein, a dye that can diffuse out of acidic compartments, were targeted to HS294 cells, incubation at 37/sup 0/C resulted in diffuse cytoplasmic fluorescence, suggesting that internalized liposomes encounter lysosomal or prelysosomal organelles.

Hawrot, E.; Rosenberg, M.B.; Preston, P.E.; Breakefield, X.O.

1986-05-01

205

Structural properties of liposomes from digital holographic microscopy  

NASA Astrophysics Data System (ADS)

We have constructed liposomes from L alpha Phosphatidylcholine (PC) lipids, which are biomimetic lipids similar to those present in the membranes of mammalian cells. We propose an advance in the use of liposomes, such as for drug delivery, to incorporate into the liposomal membranes transport proteins that have been extracted from the lipid membranes of mammalian cells. In this paper, we describe the usage of a novel optical microscope to characterize the nanomechanical properties of these liposomes. We have applied the technique of digital holographic microscopy, using an instrument recently developed at the University of Münster, Germany. This system enabled us to measure quantitatively the structural changes in liposomes. We have investigated the deformations of these biomimetic lipids comprising these liposomes by applying osmotic stresses, in order to gain insight into the membrane environment prior to incorporation of cloned membrane transport proteins. This control of the nanomechanical properties is important in the stresses transmitted to mechanosensitive ion channels that we have incorporated into the liposomal membranes. These liposomes provide transporting vesicles that respond to mechanical stresses, such as those that occur during implantation.

Di Maio, Isabelle L.; Carl, Daniel; Langehanenberg, Patrik; Valenzuela, Stella M.; Battle, Andrew R.; Al Khazaaly, Sabah; Killingsworth, Murray; Kemper, Bjorn; von Bally, Gert; Martin, Donald K.

2006-01-01

206

Opening-up of liposomal membranes by talin  

PubMed Central

Morphological changes of liposomes caused by interactions between liposomal membranes and talin, a cytoskeletal submembranous protein, were studied by direct, real-time observation by using high-intensity dark-field microscopy. Surprisingly, when talin was added to a liposome solution, liposomes opened stable holes and were transformed into cup-shaped liposomes. The holes became larger with increasing talin concentration, and finally the cup-shaped liposomes were transformed into lipid bilayer sheets. These morphological changes were reversed by protein dilution, i.e., the sheets could be transformed back into closed spherical liposomes. We demonstrated that talin was localized mainly along the membrane verges, presumably avoiding exposure of its hydrophobic portion at the edge of the lipid bilayer. This is the first demonstration that a lipid bilayer can stably maintain a free verge in aqueous solution. This finding refutes the established dogma that all lipid bilayer membranes inevitably form closed vesicles and suggests that talin is a useful tool for manipulating liposomes.

Saitoh, Akihiko; Takiguchi, Kingo; Tanaka, Yohko; Hotani, Hirokazu

1998-01-01

207

DOTAP cationic liposomes prefer relaxed over supercoiled plasmids  

Microsoft Academic Search

Cationic liposomes and DNA interact electrostatically to form complexes called lipoplexes. The amounts of unbound (free) DNA in a mixture of cationic liposomes and DNA at different cationic lipid:DNA molar ratios can be used to describe DNA binding isotherms; these provide a measure of the binding efficiency of DNA to different cationic lipid formulations at various medium conditions. In order

Simcha Even-Chen; Yechezkel Barenholz

2000-01-01

208

Differential inhibition of macrophage microbicidal activity by liposomes.  

PubMed

In vitro culture of murine resident peritoneal macrophages with lymphokine (LK)-rich leukocyte culture fluids induces enhanced microbicidal activity against amastigotes of the protozoan parasite Leishmania tropica. Macrophages infected with Leishmania and treated with LKs after infection acquire the capacity to kill the intracellular parasite within 72 h. When compared with control macrophage cultures treated with medium lacking LKs, 80 to 90% fewer macrophages treated with LKs contained amastigotes. In experiments designed to test liposome delivery of LKs to infected macrophages, addition of multilamellar liposomes composed of phosphatidylcholine and phosphatidylserine (molar ratio, 7:3) completely abrogated LK-induced microbicidal activity. Liposomes containing only phosphatidylcholine were not inhibitory. Inhibition of LK activity by the liposomes occurred regardless of whether the liposomes contained LKs. Liposomal inhibition of activated macrophage effector activity was limited to intracellular killing; LK-induced macrophage extracellular cytolysis (i.e., tumor cytotoxicity) was not affected by liposome treatment. These data indicate that elucidation of the effects of liposome composition on acquired host defense mechanisms may be useful for the design of drug delivery systems that allow expression or augmentation of immunologically induced mechanisms for the intracellular destruction of infectious agents. PMID:3967927

Gilbreath, M J; Swartz, G M; Alving, C R; Nacy, C A; Hoover, D L; Meltzer, M S

1985-02-01

209

Antibacterial Efficacy of Benzoyl Peroxide in Phospholipid Liposomes  

Microsoft Academic Search

Background: Literature reports indicate that phospholipid liposomes facilitate the accumulation of active agents in the infundibulum. Objective: The study hypothesis of an improved antibacterial efficacy of benzoyl peroxide (BPO) in phospholipid liposomes was tested in comparison with a commercial and a pharmacopoeial BPO preparation. Methods: The infundibular bacterial samples were obtained with the Permabond technique from 20 acne patients who

J. W. Fluhr; O. Barsom; W. Gehring; M. Gloor

1999-01-01

210

Optimization and characterization of liposome formulation by mixture design.  

PubMed

This study presents the application of the mixture design technique to develop an optimal liposome formulation by using the different lipids in type and percentage (DOPC, POPC and DPPC) in liposome composition. Ten lipid mixtures were generated by the simplex-centroid design technique and liposomes were prepared by the extrusion method. Liposomes were characterized with respect to size, phase transition temperature, ?-potential, lamellarity, fluidity and efficiency in loading calcein. The results were then applied to estimate the coefficients of mixture design model and to find the optimal lipid composition with improved entrapment efficiency, size, transition temperature, fluidity and ?-potential of liposomes. The response optimization of experiments was the liposome formulation with DOPC: 46%, POPC: 12% and DPPC: 42%. The optimal liposome formulation had an average diameter of 127.5 nm, a phase-transition temperature of 11.43 °C, a ?-potential of -7.24 mV, fluidity (1/P)(TMA-DPH)((¬)) value of 2.87 and an encapsulation efficiency of 20.24%. The experimental results of characterization of optimal liposome formulation were in good agreement with those predicted by the mixture design technique. PMID:22158519

Maherani, Behnoush; Arab-tehrany, Elmira; Kheirolomoom, Azadeh; Reshetov, Vadzim; Stebe, Marie José; Linder, Michel

2012-02-01

211

Liposomes remain intact when complexed with polycationic brushes.  

PubMed

Anionic liposomes adsorb onto the surface of spherical polymer particles bearing grafted linear cationic macromolecules. The size, shape, and encapsulation ability of the liposomes remain unchanged upon adsorption, thus providing immobilized self-organizing containers that have potential applications in the biomedical field. PMID:20387892

Yaroslavov, Alexander A; Sybachin, Andrei V; Schrinner, Marc; Ballauff, Matthias; Tsarkova, Larisa; Kesselman, Ellina; Schmidt, Judith; Talmon, Yeshayahu; Menger, Fredric M

2010-05-01

212

Thermosensitive liposomes for localized delivery and triggered release of chemotherapy.  

PubMed

Liposomes are a promising class of nanomedicine with the potential to provide site-specific chemotherapy, thus improving the quality of cancer patient care. First-generation liposomes have emerged as one of the first nanomedicines used clinically for localized delivery of chemotherapy. Second-generation liposomes, i.e. stimuli-responsive liposomes, have the potential to not only provide site-specific chemotherapy, but also triggered drug release and thus greater spatial and temporal control of therapy. Temperature-sensitive liposomes are an especially attractive option, as tumors can be heated in a controlled and predictable manner with external energy sources. Traditional thermosensitive liposomes are composed of lipids that undergo a gel-to-liquid phase transition at several degrees above physiological temperature. More recently, temperature-sensitization of liposomes has been demonstrated with the use of lysolipids and synthetic temperature-sensitive polymers. The design, drug release behavior, and clinical potential of various temperature-sensitive liposomes, as well as the various heating modalities used to trigger release, are discussed in this review. PMID:23583706

Ta, Terence; Porter, Tyrone M

2013-07-10

213

Synthesis, characterization and spectral properties of novel zinc phthalocyanines derived from C2 symmetric diol  

NASA Astrophysics Data System (ADS)

In this study, we described the syntheses of new zinc(II) phthalocyanine compounds derived from (1R,2R)-1,2-diphenyl-1,2-ethanediol units. The phthalonitrile precursors 3 and 4 were synthesized by the reaction of 4,5-dichlorophthalonitrile with (1R,2R)-1,2-diphenyl-1,2-ethanediol. The synthesis of zinc(II) phthalocyanine 5 and zinc(II) phthalocyanine polymer 6 by cyclotetramerization of corresponding phthalonitrile derivative were accomplished in the presence of Zn(CH3CO2)2 in a Schlenk tube containing quinoline under nitrogen atmosphere. The zinc(II) phthalocyanine 5 showed enhanced solubility in various organic solvents. The aggregation behavior of phthalocyanines was investigated at different concentrations in different solvents. Both phthalocyanines were found to exist in non-aggregated form at concentrations between 10 × 10-6 and 1 × 10-6 mol dm-3. As the concentration increased to 5 × 10-5 mol dm-3, a deviation from ideality was observed for both phthalocyanines. The novel compounds were characterized by a combination of elemental analysis and 1H NMR, 13C NMR, IR, UV-Vis and MS spectral data.

Gök, Ya?ar; Gök, Halil Zeki

2014-06-01

214

UV visible spectral study on the stability of lead phthalocyanine complexes  

NASA Astrophysics Data System (ADS)

UV visible electronic spectral study has been done on lead phthalocyanine (PbPc), lead tetranitro phthalocyanine (PbTNP) and lead tetraamino phthalocyanine (PbTAP) in dimethyl sulphoxide (DMSO) and H2SO4 media. Metal free phthalocyanine (H2Pc) is insoluble in DMSO and soluble in conc. H2SO4. The study has been extended to H2Pc to compare the stability of phthalocyanine structure with the PbPc complexes in H2SO4 medium. PbPc complexes are stable in DMSO, and all the complexes are more stable in 36 N H2SO4 than in 30 N and 28 N H2SO4 media. Further, complete demetallation and degradation of the phthalocyanine structure have been observed for all the PbPc complexes in 36 N H2SO4 medium within a week's time. The stability of these complexes is compared with H2Pc in H2SO4 medium. The decomposition reactions in H2SO4 media for H2Pc, PbPc, PbTNP and PbTAP are followed spectrophotometrically and rate constants were calculated. The decomposition reactions were found to follow the first-order kinetics with respect to the concentration of their respective phthalocyanine derivatives.

Mohan Kumar, T. M.; Achar, B. N.

2006-11-01

215

Synthesis of sterically hindered phthalocyanines and their applications to dye-sensitized solar cells.  

PubMed

Phthalocyanines with high peripheral substitutions and free from potential contamination by regioisomers have been synthesized and evaluated as photosensitizers for dye-sensitized solar cell applications. Each of the sterically hindered precursor compounds was accomplished by Suzuki-Miyaura cross-coupling reactions with the arylchloride and corresponding boronic acids. Metal free phthalocyanine-sensitized solar cells showed no photocurrent generation due to its low excited singlet state (LUMO) compared with the conduction band of TiO(2). Upon zinc metalation, the LUMO level of the phthalocyanine was pushed up, and this variation afforded an exergonic free energy change for electron injection. The zinc phthalocyanine-sensitized solar cell displayed 0.57% power conversion efficiency (eta) and 4.9% maximal IPCE in the near infrared region. More importantly, the cell prepared with and without the presence of chenodeoxycholic acid revealed no difference in the power conversion efficiency. This implies that the well-known aggregation tendency of phthalocyanines that is considered to enhance the self-quenching of the phthalocyanine excited singlet state is effectively suppressed by the high degree of substitutions. The significance of the driving force for electron injection and the distance between the dye core and the TiO(2) surface is also highlighted for devising high performance phthalocyanine photosensitizers. PMID:19082031

Eu, Seunghun; Katoh, Takashi; Umeyama, Tomokazu; Matano, Yoshihiro; Imahori, Hiroshi

2008-10-28

216

Recent Applications of Liposomes in Ophthalmic Drug Delivery  

PubMed Central

Liposomal formulations were significantly explored over the last decade for the ophthalmic drug delivery applications. These formulations are mainly composed of phosphatidylcholine (PC) and other constituents such as cholesterol and lipid-conjugated hydrophilic polymers. Liposomes are biodegradable and biocompatible in nature. Current approaches for topical delivery of liposomes are focused on improving the corneal adhesion and permeation by incorporating various bioadhesive and penetration enhancing polymers. In the case of posterior segment disorders improvement in intravitreal half life and targeted drug delivery to the retina is achieved by liposomes. In this paper we have attempted to summarize the applications of liposomes in the field of ophthalmic drug delivery by citing numerous investigators over the last decade.

Mishra, Gyan P.; Bagui, Mahuya; Tamboli, Viral; Mitra, Ashim K.

2011-01-01

217

Recent Developments in Liposome-Based Veterinary Therapeutics  

PubMed Central

Recent advances in nanomedicine have been studied in the veterinary field and have found a wide variety of applications. The past decade has witnessed a massive surge of research interest in liposomes for delivery of therapeutic substances in animals. Liposomes are nanosized phospholipid vesicles that can serve as delivery platforms for a wide range of substances. Liposomes are easily formulated, highly modifiable, and easily administered delivery platforms. They are biodegradable and nontoxic and have long in vivo circulation time. This review focuses on recent and ongoing research that may have relevance for veterinary medicine. By examining the recent developments in liposome-based therapeutics in animal cancers, vaccines, and analgesia, this review depicts the current significance and future directions of liposome-based delivery in veterinary medicine.

2013-01-01

218

Electromagnetic field triggered drug and chemical delivery via liposomes  

DOEpatents

The present invention relates to a system and to a method of delivering a drug to a preselected target body site of a patient, comprising the steps of encapsulating the chemical agent within liposomes, essentially temperature insensitive, i.e. not having a specific predetermined phase transition temperature within the specific temperature range of drug administration; administering the liposomes to the target body site; and subjecting the target body site to nonionizing electromagnetic fields in an area of the preselected target body in order to release the chemical agent from the liposomes at a temperature of between about +10 and 65 C. The invention further relates to the use of the liposomes to bind to the surface of or to enter target tissue or an organ in a living system, and, when subjected to a nonionizing field, to release a drug from the liposomes into the target site.

Liburdy, R.P.

1993-03-02

219

Electromagnetic field triggered drug and chemical delivery via liposomes  

DOEpatents

The present invention relates to a system and to a method of delivering a drug to a preselected target body site of a patient, comprising the steps of encapsulating the chemical agent within liposomes, essentially temperature insensitive, i.e. not having a specific predetermined phase transition temperature within the specific temperature range of drug administration; administering the liposomes to the target body site; and subjecting the target body site to nonionizing electromagnetic fields in an area of the preselected target body in order to release said chemical agent from the liposomes at a temperature of between about +10 and 65.degree. C. The invention further relates to the use of said liposomes to bind to the surface of or to enter target tissue or an organ in a living system, and, when subjected to a nonionizing field, to release a drug from the liposomes into the target site.

Liburdy, Robert P. (1820 Mountain View Rd., Tiburon, CA 94920)

1993-01-01

220

[Temperature sensitive liposome encapsulated adriamycin combined with hepatic artery embolization].  

PubMed

A temperature sensitive liposome composed of a vesicle membrane of dipalmitoyl phosphatidylcholine and encapsulated adriamycin was made by the modified reverse-phase evaporation method. The encapsulation efficiency measured with a centrifugal filtration method was about 38%. The phase-transition temperature of the liposome determined by DSC was 41 degrees C. The liposome size was 851 +/- 50 nm, and the size distribution was from 772 to 952 nm as measured by laser particle analyzer with dynamic light scatter method. Eighty-four percent of the encapsulated drug could be released at precisely the phase-transition temperature of liposome in vitro. The results show that the liposomal drug is sensitive to temperature-controlled release. PMID:1805526

Zou, Y Y; Gu, X Q; Horikoshi, I M

1991-01-01

221

pH-Dependent Fusion between the Semliki Forest Virus Membrane and Liposomes  

Microsoft Academic Search

Semliki Forest virus was mixed with liposomes containing phosphatidylcholine, phosphatidylethanolamine, sphingomyelin, and cholesterol. When the pH of the mixture was dropped to 6 or below, rapid fusion between the membranes of the virus and the liposomes occurred, resulting in the transfer of viral nucleocapsids into the liposomes. Fusion was demonstrated biochemically by trapping RNase or trypsin within the liposomes. Trapped

Judy White; Ari Helenius

1980-01-01

222

Water-soluble platinum phthalocyanines as potential antitumor agents.  

PubMed

Breast cancer represents the second cause of death in the European female population. The lack of specific therapies together with its high invasive potential are the major problems associated to such a tumor. In the last three decades platinum-based drugs have been considered essential constituents of many therapeutic strategies, even though with side effects and frequent generation of drug resistance. These drugs have been the guide for the research, in last years, of novel platinum and ruthenium based compounds, able to overcome these limitations. In this work, ruthenium and platinum based phthalocyanines were synthesized through conventional techniques and their antiproliferative and/or cytotoxic actions were tested. Normal mammary gland (MCF10A) and several models of mammarian carcinoma at different degrees of invasiveness (BT474, MCF-7 and MDA-MB-231) were used. Cells were treated with different concentrations (5-100 ?M) of the above reported compounds, to evaluate toxic concentration and to underline possible dose-response effects. The study included growth curves made by trypan blue exclusion test and scratch assay to study cellular motility and its possible negative modulation by phthalocyanine. Moreover, we investigated cell cycle and apoptosis through flow cytometry and AMNIS Image Stream cytometer. Among all the tested drugs, tetrasulfonated phthalocyanine of platinum resulted to be the molecule with the best cytostatic action on neoplastic cell lines at the concentration of 30 ?M. Interestingly, platinum tetrasulfophtalocyanine, at low doses, had no antiproliferative effects on normal cells. Therefore, such platinum complex, appears to be a promising drug for mammarian carcinoma treatment. PMID:24699848

Bologna, Giuseppina; Lanuti, Paola; D'Ambrosio, Primiano; Tonucci, Lucia; Pierdomenico, Laura; D'Emilio, Carlo; Celli, Nicola; Marchisio, Marco; d'Alessandro, Nicola; Santavenere, Eugenio; Bressan, Mario; Miscia, Sebastiano

2014-06-01

223

Magnetism and multiplets in metal-phthalocyanine molecules  

PubMed Central

Magnetism and multiplets for metal-phthalocyanine (MPc) molecules with transition-metals (M) of Mn and Co were investigated based on the constraint density functional theory calculations by imposing density matrix constraint on the d-orbital occupation numbers. For the MnPc, the ground state is found to be the 4Eg state with the perpendicular magnetic anisotropy with respect to the molecular plane, while for the CoPc, the ground state is the 2A1g state with a planar magnetic anisotropy.

Kitaoka, Y.; Sakai, T.; Nakamura, K.; Akiyama, T.; Ito, T.

2013-01-01

224

Magnetism and multiplets in metal-phthalocyanine molecules.  

PubMed

Magnetism and multiplets for metal-phthalocyanine (MPc) molecules with transition-metals (M) of Mn and Co were investigated based on the constraint density functional theory calculations by imposing density matrix constraint on the d-orbital occupation numbers. For the MnPc, the ground state is found to be the (4)Eg state with the perpendicular magnetic anisotropy with respect to the molecular plane, while for the CoPc, the ground state is the (2)A1g state with a planar magnetic anisotropy. PMID:23606755

Kitaoka, Y; Sakai, T; Nakamura, K; Akiyama, T; Ito, T

2013-05-01

225

Porphyrins XV. Vapor absorption spectra and stability: Phthalocyanines  

Microsoft Academic Search

Vapor absorption spectra in the range 800-200 mmu are given for free base phthalocyanine (H2Pc), MgPc, TiOPc, VOPc, CrPc, FePc, CoPc, NiPc, CuPc, ZuPc, SnCl2Pc, and PbPc. Electronic bands Q, B, N, L, C characteristic of the ring are found in the regions 660 mmu (15 200 cm-1), 320 mmu (31 300 cm-1), 275 mmu (36 400 cm-1), 245 mmu

Lawrence Edwards; Martin Gouterman

1970-01-01

226

Novel gallium(III) phthalocyanine derivatives – Synthesis, photophysics and photochemistry  

Microsoft Academic Search

The syntheses of gallium(III) chloride phthalocyanine {(Cl)GaPc}, octaphenoxyphthalocyaninato gallium(III) chloride {(Cl)GaOPPc} and octakis(4-tert-butylphenoxy)phthalocyaninato gallium(III) chloride {(Cl)GaOTBPPc}; as well as their photophysical and photochemical parameters are hereby presented. Fluorescence quantum yields do not vary much among the three metallophthalocyanines (MPcs); therefore it was concluded that the effect of the substituents is not significant amongst (Cl)GaPc, (Cl)GaOPPc and (Cl)GaOTBPPc. Solvents effects, however,

Vongani Chauke; Abimbola Ogunsipe; Mahmut Durmu?; Tebello Nyokong

2007-01-01

227

Phthalocyanine-C60 composites as improved photoreceptor materials?  

NASA Astrophysics Data System (ADS)

With the methods of photoelectron spectroscopy (UPS), X-ray absorption near edge spectroscopy (XANES) and optical transmission spectroscopy we demonstrate that an electron transfer from light-induced excitonic states of different phthalocyanines (Pcs) towards unoccupied electronic states of C60 is energetically possible, thereby increasing the generation efficiency for free charge carriers. No indication for a ground state electron transfer is found for any of the Pcs in contact to C60. The improvement of ?-H2-Pc due to the admixture of C60 is directly shown by an enhanced photoconductivity.

Kessler, B.; Schlebusch, C.; Morenzin, J.; Eberhardt, W.

1998-08-01

228

Novel phthalocyanine thin film for compact disc recordable  

NASA Astrophysics Data System (ADS)

In this paper, the spin-coated thin films of phthalocyanine dye are presented. Absorption spectrum of the thin film shows a comparatively broad absorption in the wavelength range 630-770 nm. Optical parameters of the thin film were measured by a spectroscopic ellipsometer system. 5-in CD-R discs made of this dye exhibit good performance with Yamaha 20-speed recorder. Jitters of land and pit are less than 30 ns, and the 3T-11T's signals show very good quality. This dye is a promising recording medium for CD-R with much higher recording speed.

Geng, Yongyou; Gu, Donghong; Wu, Yiqun; Gan, Fuxi

2003-02-01

229

TLC characterization of liposomes containing D-myo-inositol derivatives.  

PubMed

The thin-layer chromatographic (TLC) behaviour of liposomes containing inositol phosphates (IPs) was studied. The liposomes contained different concentrations of D-myo-inositol 1,4,5k-trisphosphate (IP3), D-myo-inositol 1,2,6-trisphosphate (alpha-trinositol, PP 56, a novel Perstorp Pharma derivative), D-myo-inositol 1,3,4,5-tetrakisphosphate (IP4), D-myo-inositol 1,3,4,5,6-pentakisphosphate (IP5) and D-myo-inositol 1,2,3,4,5,6-hexakisphosphate (IP6). Migration of all liposome batches was compared to that of control liposomes (containing only triple distilled water), and to that of free phosphatidylcholine (PC); the same amount of lipid was used in all situations. Thin-layer chromatography was performed on silica gel as adsorbent. As solvent we used an n-buthanol:ethanol:water mixture in a 4:3:3 volume ratio. Significant differences were found between PC and all liposome batches, as well as between control liposomes and the ones containing IP3, alpha-trinositol, IP4, or IP5, in various concentrations. Liposomes containing IP6 migrate completely differently compared not only to phosphatidylcholine and control liposomes, but also to the ones containing other IPs ( < 10(-3) M). Unlike the other IPs studied, liposome-entrapped IP6 elicits dose-dependent contractions of the isolated rat aorta. This suggests that liposomes loaded with IP6 undergo, during or after their preparation, physico-chemical alterations that eventually change their drug-delivery capacity. PMID:8520206

Brailoiu, E; Huhurez, G; Slatineanu, S; Filipeanu, C M; Costuleanu, M; Branisteanu, D D

1995-01-01

230

Clearance and localization of intravitreal liposomes in the aphakic vitrectomized eye  

SciTech Connect

The authors have examined the fate of intravitreally injected liposomes in the aphakic, vitrectomized eye of the rabbit. Liposomes labelled with /sup 125/(I)-p-hydroxybenzimidylphosphatidylethanolamine were eliminated rapidly from the intraocular fluid. Nonetheless, a significant fraction of these liposomes were found to bind to various ocular tissues including the retina, iris, sclera, and cornea. Ultrastructural studies with gold colloid-loaded liposomes revealed that retinal bound liposomes were attached to the inner limiting lamina but did not penetrate to the internal cells of the retina. Epiretinal cells bound and internalized gold colloid-loaded liposomes suggesting that these cells may be very sensitive to liposome mediated drug delivery.

Stern, W.H.; Heath, T.D.; Lewis, G.P.; Guerin, C.J.; Erickson, P.A.; Lopez, N.G.; Hong, K.L.

1987-05-01

231

An OEGylated thiol monolayer for the tethering of liposomes and the study of liposome interactions.  

PubMed

The aim of the present work is to develop a protocol for the specific immobilization of liposomes, via tethers, onto functionalized gold surfaces, and in addition to give one example for such a surface architecture. All surface functionalization steps are charcerized and controlled. First, mixed thiolate self-assembled monolayers (SAMs) prepared from COOH- and OCH(3)-terminated oligo(ethylene glycol) (OEG) alkane thiols were characterized by polarization modulation reflection absorption infrared spectroscopy (PM-RAIRS) and by X-ray photoemission spectroscopy (XPS). The composition of the mixed SAMs was found to be close to that of the thiol solution. Next, grafting of biotin conjugated with an NH(2)-terminated OEG spacer (biotin-OEG-NH(2)) to the COOH groups via conventional amine coupling was optimized with respect to the COOH/OCH(3) ratio of the SAM. The grafting of biotin-OEG-NH(2) was assessed by monitoring the binding of neutravidin and albumin to the biotinylated surfaces using quartz crystal microbalance with dissipation monitoring (QCM-D), as well as by PM-RAIRS. It was shown that a COOH/OCH(3) ratio of around 0.3 was sufficient to saturate the SAMs with neutravidin. Finally, tethering of liposomes onto the neutravidin-terminated SAMs, was achieved. As an application example, of a close packed layer of tethered liposomes was exposed to the membrane-penetrating peptide melittin. As monitored by QCM-D, the liposomes fused when interacting with the peptide and ruptured into an extended, supported lipid bilayer over the whole surface. In summary, the described surface modification has potential for the development of assays requiring tethered intact liposomes, or tethered planar bilayers. Such surface architectures are especially important for the study of transmembrane proteins and peptides. PMID:20441878

Briand, Elisabeth; Humblot, Vincent; Pradier, Claire-Marie; Kasemo, Bengt; Svedhem, Sofia

2010-06-15

232

Synthesis, photophysical and photochemical studies on long chain zinc phthalocyanine derivatives  

Microsoft Academic Search

The synthesis and characterization of 2,9,16,23-chloro-3,10,17,24-triethyleneoxysulphanylphthalocyaninato zinc(II) (CTESZnPc) is described. The photophysics and photochemistry of CTESZnPc and those of tetrakis(triethyleneoxysulphanyl)zinc phthalocyanine (TTESZnPc) and octakis(triethyleneoxysulphanyl)zinc phthalocyanine (OTESZnPc), are presented and compared with those of unsubstituted zinc phthalocyanine (ZnPc). The presence of triethyleneoxysulphanyl substituents on the ZnPc ring gave rise to higher values of singlet oxygen (??) and photodegradation (?Pd) quantum yields

Abimbola Ogunsipe; Mahmut Durmu?; Devrim Atilla; Ay?e Gül Gürek; Vefa Ahsen; Tebello Nyokong

2008-01-01

233

Accelerated blood clearance of PEGylated liposomes following preceding liposome injection: Effects of lipid dose and PEG surface-density and chain length of the first-dose liposomes  

Microsoft Academic Search

We recently reported that a second dose of polyethylene glycol (PEG) (M.W. 2000)-modified liposomes (mPEG2000-liposomes) is rapidly cleared from the blood and accumulates in the liver when injected twice in the same rat or mouse at several-day intervals (referred to as the “accelerated blood clearance (ABC) phenomenon”). In the present study we observed that a high dose (5 ?mol\\/kg) of

Tatsuhiro Ishida; Masae Harada; Xin Yu Wang; Masako Ichihara; Kenji Irimura; Hiroshi Kiwada

2005-01-01

234

Analysis of individual lipoproteins and liposomes  

SciTech Connect

We describe the application of single molecule detection (SMD) technologies for the analysis of natural (serum lipoproteins) and synthetic (liposomes) transport systems. The need for advanced analytical procedures of these complex and important systems is presented with the specific enhancements afforded by SMD with flowing sample streams. In contrast to bulk measurements which yield only average values, measurement of individual species allows creation of population histograms from heterogeneous samples. The data are acquired in minutes and the analysis requires relatively small sample quantities. Preliminary data are presented from the analysis of low density lipoprotein, and multilamellar and unilamellar vesicles.

Robbins, D.L.; Keller, R.A.; Nolan, J.P. [and others

1997-08-01

235

Spectroscopic studies of alpha tocopherol interaction with a model liposome and its influence on oxidation dynamics.  

PubMed

The influence of ?-tocopherol on the surface conformation of liposome, as a model component of lipoproteins, and its role in oxidation process were studied. FT-IR spectra from suspensions of neat liposome, mixtures of liposome and ?-tocopherol and liposome with incorporated ?-tocopherol were analyzed. When ?-tocopherol was incorporated into liposome, intensities of some bands were decreased or increased in comparison with the spectra of liposome and ?-tocopherol mixture. These changes reflect the different localization of ?-tocopherol in two types of liposome suspensions. The oxidation of liposome suspensions was initiated by addition of cupric ions. After prolonged oxidation, the differences in FT-IR spectra of oxidized samples were recorded. Differences were observed in comparison with spectra of native and oxidized liposomes were analyzed. The rate of oxidation was measured by EPR oximetry. Oxidation was generally very slow, but faster in liposome without ?-tocopherol, indicating the protective role of ?-tocopherol against liposome oxidation. On the other hand, liposome suspensions with EDTA in the buffer were not oxidized at all, while those with ?-tocopherol and liposome mixture were only slightly oxidized. In this case the consumption of oxygen was the result of liposome oxidation supported by ?-tocopherol. These results reflect the ambivalent role of ?-tocopherol in liposome oxidation, similarly to findings in studies of lipoprotein oxidation. PMID:24746659

Krilov, Dubravka; Kosovi?, Marin; Serec, Kristina

2014-08-14

236

Effect of antiooxidants on phthalocyanine photosensitization of human erythrocytes  

NASA Astrophysics Data System (ADS)

Photohemolysis of human erythrocytes sensitized by sulfonated aluminum phthalocyanine was used as an endpoint to study possible chemical modifications of photodynamic therapy. Ascorbate, in concentrations up to 0.1 mM, had a small protective effect. In larger amounts it stimulated the rate of photohemolysis in a concentration dependent manner up to 1 mM, by a factor of 2. Azide and D2O tests indicated some participation of singlet oxygen, although to a lesser extent than in the absence of ascorbate. Kinetic considerations augur for reaction path initiated by an interaction of excited sensitizer-ascorbate, parallel to the singlet oxygen- mediated process. Because of the ubiquitous presence of ascorbate in human tissues in concentrations comparable to those of dissolved oxygen, it is a reasonable estimation that in photodynamic therapy, a fraction of the photodynamic damage proceeds via a Type I, ascorbate-assisted mechanism. Tocopherol had an effect opposite to that of ascorbate, namely it inhibited the photohemolysis. Likewise, quercetin, a plant flavonoid, was protective against phthalocyanine-induced photohemolysis.

Ben-Hur, Ehud; Rosenthal, Ionel

1993-06-01

237

Photovoltaic action spectra of metal-phthalocyanine Schottky barrier cells  

NASA Astrophysics Data System (ADS)

The direct current (dc) action spectra of Al and In/phthalocyanine (alpha, beta, and x-H2Pc and VOPc) photovoltaic cells in the wavelength range of 400-900 nm were determined. The data were evaluated in terms of both the local carrier generation and exciton diffusion models. Photoactive barrier widths of 390, 475, 310, and 950 A for In/alpha, beta, and x-H2Pc and VOPC, respectively, were found using the local carrier generation model. A dc discharge capacitance technique was employed to measure the depletion region width of In-phthalocyanine Schottky junctions. In all cases, the depletion region widths (capacitance) were found to be consistently smaller than the photoactive collection region widths (action spectra). These findings indicate that excitons produced within a diffusion length of the barrier can diffuse into the barrier zone and dissociate into collectable carriers. A barrier width of the order of 200-300 A and an exciton diffusion length of 300-500 A were obtained for In/x-H2Pc cells using a combined local carrier generation and exciton diffusion model.

Loutfy, R. O.; Hsiao, C. K.; Ho, R.

1983-10-01

238

Rational design of a zinc phthalocyanine binding protein.  

PubMed

Phthalocyanines have long been used as primary donor molecules in synthetic light-powered devices due to their superior properties when compared to natural light activated molecules such as chlorophylls. Their use in biological contexts, however, has been severely restricted due to their high degree of self-association, and its attendant photoquenching, in aqueous environments. To this end we report the rational redesign of a de novo four helix bundle di-heme binding protein into a heme and Zinc(II) phthalocyanine (ZnPc) dyad in which the ZnPc is electronically and photonically isolated. The redesign required transformation of the homodimeric protein into a single chain four helix bundle and the addition of a negatively charge sulfonate ion to the ZnPc macrocycle. To explore the role of topology on ZnPc binding two constructs were made and the resulting differences in affinity can be explained by steric interference of the newly added connecting loop. Singular binding of ZnPc was verified by absorption, fluorescence, and magnetic circular dichroism spectroscopy. The engineering guidelines determined here, which enable the simple insertion of a monomeric ZnPc binding site into an artificial helical bundle, are a robust starting point for the creation of functional photoactive nanodevices. PMID:23827257

Mutter, Andrew C; Norman, Jessica A; Tiedemann, Michael T; Singh, Sunaina; Sha, Sha; Morsi, Sara; Ahmed, Ismail; Stillman, Martin J; Koder, Ronald L

2014-02-01

239

Submonolayer growth of copper-phthalocyanine on Ag(111)  

NASA Astrophysics Data System (ADS)

The growth of high-quality thin films is a key issue in the ability to design electronic devices based on organic materials and to tune their properties. In this context, the interfaces between metals and organic films play a decisive role. Here, we report on the interface formation between copper-phthalocyanine (CuPc) and an Ag(111) surface using various complementary methods. High-resolution low-energy electron diffraction revealed a rich phase diagram for this system with disordered (two-dimensional (2D)-gas-like) and ordered structures (commensurate and point-on-line). In particular, a continuous change in lattice parameters with increasing coverage was found for long-range ordered structures, indicating a substrate-mediated repulsive intermolecular interaction similar to the case of tin-phthalocyanine/Ag(111). Chemisorptive bonding to the substrate was found by x-ray standing waves and ultraviolet photoelectron spectroscopy, and this weakened with increasing coverage at low temperature. This remarkable effect is correlated to a shift in the highest occupied molecular orbital (HOMO) and a HOMO-1 split off band to higher binding energies. Based on our experimental results, we present a comprehensive study of the adsorption behavior of CuPc/Ag(111), including the mechanisms for phase formation and molecular interaction.

Kröger, Ingo; Stadtmüller, Benjamin; Stadler, Christoph; Ziroff, Johannes; Kochler, Mario; Stahl, Andreas; Pollinger, Florian; Lee, Tien-Lin; Zegenhagen, Jörg; Reinert, Friedrich; Kumpf, Christian

2010-08-01

240

Electrical bistable properties of copper phthalocyanine at different deposition rates  

NASA Astrophysics Data System (ADS)

Organic bistable memory device is a next-generation of the electrical memory unit. In this paper, we report about the influence of structural properties on electrical bistable behavior of copper phthalocyanine organic memory device. Copper phthalocyanine (CuPc) layer was prepared by thermal evaporation technique at different deposition rates. When the deposition rate is increased, the film crystalline decreases and the surface morphology gradually changes from large flat grain to fine grain structure. Structural parameters such as the crystalline size of CuPc films and dislocation density can be calculated from XRD spectra. Moreover, the effect of deposition rate of CuPC layer on the bistable properties can be performed by current-voltage characteristics, retention measurement, impedance spectroscopy and temperature dependence measurement. The conduction mechanism in both ON and OFF states of the bistable device was analyzed by theoretical model, which can be proposed as a possible trap center of the carrier trapping and de-trapping process by structural defects in CuPc layer. Furthermore, the reliability issue such as cycling endurance and data retention is presented.

Onlaor, K.; Tunhoo, B.; Keeratithiwakorn, P.; Thiwawong, T.; Nukeaw, J.

2012-06-01

241

Electrophoretic deposition of phthalocyanine in organic solutions containing trifluoroacetic acid.  

PubMed

The absorption spectra of copper phthalocyanine (CuPc) 1,2-dichloroethane (DCE) solutions containing trifluoroacetic acid (TFAA) shows that the number of protons coordinating to the CuPc molecule was 1 and 2 for the first and second proton adducts, respectively, which indicates the formations of CuPcH(+) and CuPcH(2)(2+). This CuPc molecule may act as a catalyst to dissociate TFAA into trifluoroacetate anion (A(-)) and H(+) and form the proton adducts. The electrical conductivity dependence of the solution on CuPc concentration also supports this mechanism. A dense film of CuPc was deposited on an indium tin oxide cathode plate by electrophoresis of the solution. Similar dense films of a wide variety of phthalocyanines (MPc; M = Cu, H(2), Fe, Ni, Zn, Pb, VO) were also deposited using this method. Similar films of CuPc were also formed using dichloromethane (DCM) and 1,1,1-trichloroethane (TCE) in place of DCE. Depositions are ascribed to the migration of positively charged monomers (i.e., protonated MPc). Scanning electron microscopy revealed that these films are composed of fibrous crystallites, size of which was found to increase with the electrophoresis time, the strength of the applied electrical field and the concentration of CuPc in the bath. The influence of the dielectric constant of the organic solvent on the film growth is discussed. PMID:20886893

Shrestha, Nabeen K; Kohn, Hideki; Imamura, Mitsuharu; Irie, Kazunobu; Ogihara, Hitoshi; Saji, Tetsuo

2010-11-16

242

The effect of intercalants on the host liposome.  

PubMed

When phospholipids are vigorously dispersed in water, liposomes are formed. In the present study, we have explored the effect of intercalant concentration on various properties of unilamellar liposomes. Liposomes were sonically intercalated with vitamin E acetate (VitEAc) and hypericin (Hy) until no difference in light transmission was observed, which reflects the formation of liposomes of minimal diameter. Our studies indicate that the intercalant structure and concentration have an influence on the liposome diameter, which could be directly measured by cryogenic transmittance electronic microscopy. Thus, intercalated VitEAc substantially decreased the diameter of unilamellar dimyristoylphosphatidylcholine liposomes, whereas Hy did not. In addition, we followed peak intensities in the absorbance and fluorescence spectra of Hy as a function of intercalant concentration in the liposomal solution. Initially, the fluorescence intensity increased linearly with concentration; however, the curve then arched asymptotically, followed by a decrease in fluorescence at yet higher concentrations. Because the Hy monomer is the only species that emits fluorescence, we believe that the decrease of fluorescence intensity is the result of Hy aggregation. PMID:22799604

Cohen, Yael; Weitman, Hana; Afri, Michal; Yanus, Rinat; Rudnick, Safra; Talmon, Yeshayahu; Schmidt, Judith; Aped, Pinchas; Shatz, Smadar; Ehrenberg, Benjamin; Frimer, Aryeh A

2012-12-01

243

Complexation of anionic liposomes with spherical polycationic brushes.  

PubMed

Spherical polycationic brushes, consisting of polystyrene particles with linear cationic macromolecules grafted onto their surfaces, were electrostatically complexed with small unilamellar anionic liposomes. Complexation was monitored using a multimethod approach that included laser electrophoresis, dynamic light scattering, fluorescence, cryogenic transmission electron microscopy, and conductivity. Liposomes adsorb onto the outer edges of the brushes rather than penetrate into their dense polycationic layer. The integrity of the liposomes remains unaltered when the liposomes reside on the polycationic brushes. The resulting complexes (roughly 40 liposomes per brush) do not dissociate into their components upon exposure to physiological solutions. The system is potentially useful in that liposomes are gathered into well-defined clusters with a high encapsulating potential. Multicomponent constructs can be easily prepared if polycationic brushes are allowed to bind to a mixture of liposomes that encapsulate different guests. This work provides an example of "systems chemistry" whereby as many as eight components, each with its own particular location and function (i.e., polystyrene core, polycationic graft, egg lecithin, cardiolipin, two fluorescent dyes, water, and buffer), collectively self-assemble. PMID:21449568

Sybachin, Andrey V; Ballauff, Matthias; Kesselman, Ellina; Schmidt, Judith; Talmon, Yeshayahu; Tsarkova, Larisa; Menger, Fredric M; Yaroslavov, Alexander A

2011-05-01

244

Effect of liposomal amphotericin B on murine macrophages and lymphocytes.  

PubMed Central

The effect of liposome-encapsulated amphotericin B on mouse macrophages and on T- and B-lymphocyte functions in vitro was compared with that of free amphotericin B. Liposomal amphotericin B was generally less toxic than the free form of the drug. Low concentrations of free amphotericin B completely inhibited the serum-dependent induction of transglutaminase, a marker for macrophage differentiation, and production of superoxide anion by macrophages, whereas encapsulation of the drug within liposomes protected the cells from these adverse effects. Liposomal amphotericin B did not affect the blastogenic response of T cells compared with the free drug, which was inhibitory at high concentrations. Antibody production in vivo was inhibited partially by both free and liposomal amphotericin B. These results thus suggest that encapsulation of amphotericin B in liposomes reduces the immunosuppressive effects exerted by free amphotericin B. This provides further justification for therapeutic use of liposomal amphotericin B in systemic fungal infections (G. Lopez-Berestein, R. Mehta, R. L. Hopfer, K. Mills, L. Kasi, K. Mehta, V. Fainstein, M. Luna, E. M. Hersh, and R. L. Juliano, J. Infect. Dis. 147:939-945, 1983).

Mehta, R T; Mehta, K; Lopez-Berestein, G; Juliano, R L

1985-01-01

245

Liposomes loaded with histone deacetylase inhibitors for breast cancer therapy.  

PubMed

Histone deacetylase (HDAC) inhibitors (HDACi) of the class I trichostatin A (TSA), CG1521 (CG), and PXD101 (PXD) were incorporated at a high rate (approximately 1mM) in liposomes made of egg phosphatidylcholine/cholesterol/distearoylphosphoethanolamine-polyethylenglycol(2000) (64:30:6). Physicochemical parameters (size, zeta potential, loading, stability, release kinetics) of these HDACi-loaded pegylated liposomes were optimized and their cytotoxicity (MTT test) was measured in MCF-7, T47-D, MDA-MB-231 and SkBr3 breast cancer cell lines. In MCF-7 cells, TSA and PXD were efficient inducers of proteasome-mediated estradiol receptor alpha degradation and they both affected estradiol-induced transcription (TSA>PXD) contrary to CG. Moreover, TSA most efficiently altered breast cancer cell viability as compared to the free drug, CG-liposomes being the weakest, while unloaded liposomes had nearly no cytotoxicity. Pegylated liposomes loaded with TSA or PXD remained stable in size, charge and biological activity for one month when stored at 4 degrees C. All HDACi-loaded liposomes released slowly the encapsulated drug in vitro, CG-loaded liposomes showed the slowest release kinetic. These formulations could improve the efficacy of HDACi not only in breast cancers but also in other solid tumors because most of these drugs are poor water soluble and unstable in vivo, and their administration remains a challenge. PMID:20603204

Urbinati, Giorgia; Marsaud, Véronique; Plassat, Vincent; Fattal, Elias; Lesieur, Sylviane; Renoir, Jack-Michel

2010-09-15

246

Thioaptamer Conjugated Liposomes for Tumor Vasculature Targeting  

PubMed Central

Recent developments in multi-functional nanoparticles offer a great potential for targeted delivery of therapeutic compounds and imaging contrast agents to specific cell types, in turn, enhancing therapeutic effect and minimizing side effects. Despite the promise, site specific delivery carriers have not been translated into clinical reality. In this study, we have developed long circulating liposomes with the outer surface decorated with thioated oligonucleotide aptamer (thioaptamer) against E-selectin (ESTA) and evaluated the targeting efficacy and PK parameters. In vitro targeting studies using Human Umbilical Cord Vein Endothelial Cell (HUVEC) demonstrated efficient and rapid uptake of the ESTA conjugated liposomes (ESTA-lip). In vivo, the intravenous administration of ESTA-lip resulted in their accumulation at the tumor vasculature of breast tumor xenografts without shortening the circulation half-life. The study presented here represents an exemplary use of thioaptamer for targeting and opens the door to testing various combinations of thioaptamer and nanocarriers that can be constructed to target multiple cancer types and tumor components for delivery of both therapeutics and imaging agents.

Mann, Aman P.; Bhavane, Rohan C.; Somasunderam, Anoma; Montalvo-Ortiz, Brenda Liz; Ghaghada, Ketan B.; Volk, David; Nieves-Alicea, Rene; Suh, K. Stephen; Ferrari, Mauro; Annapragada, Ananth; Gorenstein, David G.; Tanaka, Takemi

2011-01-01

247

Studying amino acid transport using liposomes.  

PubMed

The transport of amino acid across the membranes has great importance in cell metabolism. Specific experimental methodologies are required for measuring the vectorial reactions catalyzed by the membrane transporters. So far, the most widely used technique to study amino acid transport was the measure of amino acid flux in intact cell systems expressing a specific transporter. Some limitations in this procedure are caused by the presence of endogenous transporters and intracellular enzymes and by the inaccessibility of the intracellular compartment. Alternative experimental strategies which allow to reducing the interferences and improving the handling of the internal compartment would be useful to the amino acid transport knowledge.An experimental protocol, which makes use of liposomes to study the transport of amino acid mediated by the glutamine/amino acid (ASCT2) transporter, solubilized from rat kidney brush borders, is described. The procedure is based on the reconstitution of the transporter in liposomes by removal of detergent from mixed micelles of detergent, solubilized protein, and phospholipid. The transport is assayed in the formed proteoliposomes measuring the Na(+) dependent uptake of L: -[(3)H]glutamine in antiport with internal L: -glutamine. This method allows measuring the transport activity under well controlled experimental conditions and permits performing experiments which cannot be realized in intact cell systems. PMID:20013389

Indiveri, Cesare

2010-01-01

248

Binding of phosphorothioate oligonucleotides to zwitterionic liposomes.  

PubMed

Although double-stranded DNA (dsDNA) has been shown to bind to zwitterionic lipids, it has been reported that this association is stronger for disordered (L(alpha)) phase lipids than for well-ordered (L(beta)) lipids. In this work, the interaction of single-strand phosphorothioate oligonucleotides (ONs) with unilamellar liposomes of saturated and unsaturated zwitterionic phosphocholines (PCs) and phosphoroethylamine (PE) was investigated. It is shown that the association of phosphorothioate ONs to diacyl glycerophosphocholines is strong, but only for L(beta) phase or otherwise ordered bilayers. There is no measurable affinity for PE lipids. The apparent affinity of three different phosphorothioate ONs for L(beta) phase 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) has been measured and the dissociation constants were on the order of 10(-7) M. Purine-rich ON sequences had stronger binding to DPPC liposomes than did pyrimidine-rich sequences, but there were other sequence-dependent factors. This exceptionally high affinity could be an important consideration in ON uptake, delivery, and biodistribution. PMID:12007624

Lu, Dongmei; Rhodes, David G

2002-06-13

249

Droplet-Based Production of Liposomes  

NASA Technical Reports Server (NTRS)

A process for making monodisperse liposomes having lipid bilayer membranes involves fewer, simpler process steps than do related prior methods. First, a microfluidic, cross junction droplet generator is used to produce vesicles comprising aqueous solution droplets contained in single layer lipid membranes. The vesicles are collected in a lipid-solvent mix that is at most partially soluble in water and is less dense than is water. A layer of water is dispensed on top of the solvent. By virtue of the difference in densities, the water sinks to the bottom and the solvent floats to the top. The vesicles, which have almost the same density as that of water, become exchanged into the water instead of floating to the top. As there are excess lipids in the solvent solution, in order for the vesicles to remain in the water, the addition of a second lipid layer to each vesicle is energetically favored. The resulting lipid bilayers present the hydrophilic ends of the lipid molecules to both the inner and outer membrane surfaces. If lipids of a second kind are dissolved in the solvent in sufficient excess before use, then asymmetric liposomes may be formed.

Ackley, Donald E.; Forster, Anita

2009-01-01

250

Liposomal daunorubicin as treatment for Kaposi's sarcoma  

PubMed Central

Anthracycline compounds including daunorubicin are the foundation of many modern chemotherapeutic regimens. However, the side-effects of these compounds can be severe, leading to alopecia, nausea, immune deficiency, and cardiotoxicity. For immunocompromised patients with aggressive Kaposi’s sarcoma (KS), these complications often preclude the completion of appropriate chemotherapeutic regimens. This review focuses on the development and efficacy of liposomal daunorubicin (DaunoXome®; DNX) carriers for the treatment of KS. Encouragingly, DNX demonstrated increased in vivo stability and specificity. As a result, KS patients benefit from higher cumulative chemotherapeutic doses without significant cardiotoxicity. Tumor response to DNX treatment surpasses that of non-encapsulated daunorubicin and is similar to that observed with conventional multi-drug therapies such as ABV (doxorubicin, bleomycin, vincristine). Moreover, some reports indicate the patient quality of life during therapy may improve with DNX treatment. Although the development of DNX represents a significant advance in KS therapy, recent data suggest that additional modification of the liposomal carrier to include pegylation or target specific antibodies may further increase daunorubicin efficacy in the future.

Petre, Christin E; Dittmer, Dirk P

2007-01-01

251

Photo-induced electron transfer between a dendritic zinc(II) phthalocyanine and methyl viologen  

NASA Astrophysics Data System (ADS)

The intermolecular electron transfer between the carboxylic dendritic zinc(II) phthalocyanines [G1-ZnPc( and G2-ZnPc(] and methyl viologen (MV) is studied by steady-state fluorescence and UV/Vis absorption spectroscopic method. The effect of dendron generation of this series of dendritic phthalocyanines on intermolecular electron transfer is investigated. The results show that the fluorescence emission of these dendritic phthalocyanines could be greatly quenched by MV upon excitation at 610 nm. The Stern-Volmer constant (KSV) of electron transfer is decreased with increasing dendron generations. Our study suggests that these dendritic phthalocyanines are an effective new electron donor and transmission complex and could be used as a potential artificial photosynthesis system.

Wang, Yuhua; Chen, Jiangxu; Huang, Lishan; Xie, Shusen; Yang, Hongqin; Peng, Yiru

2013-01-01

252

Femtosecond Dynamics of Fluoro-Aluminum Phthalocyanine and Linear Alkane Molecules.  

National Technical Information Service (NTIS)

The dynamics of fluoro-aluminum phthalocyanine polycrystalline thin films is studied using differential transmission spectroscopy with femtosecond laser pulses. Following excitation by 620 nm pulses into the first electronic transition a very rapid energy...

Z. Z. Ho V. William N. Peyghambarian W. M. Hetherington

1989-01-01

253

Raman spectra of solid films—V. Chloroaluminum, chlorogallium and chloroindium phthalocyanine complexes  

NASA Astrophysics Data System (ADS)

Raman spectra of evaporated thin solid films (200 nm thickness) are studied using excitation frequencies in resonance and near resonance with the absorption red band of Al, Ga and in phthalocyanine. Depolarization ratios measured on thin films are also discussed.

Jennings, Carol; Aroca, Ricardo; Hor, Ah-Mee; Loutfy, Rafik O.

254

Evaluation of Doped Phthalocyanines and a Chemically-Sensitive Field Effect Transistor for Detecting Nitrogen Dioxide.  

National Technical Information Service (NTIS)

This study involved the design and fabrication of an integrated circuit microsensor for the detection of nitrogen dioxide; metal-doped phthalocyanine compounds were evaluated as a candidate chemically-sensitive membrane, and their performance was compared...

T. J. Jenkins

1989-01-01

255

Electronic Structure of Iron Phthalocyanine and Its Analogs: A Theoretical Study.  

National Technical Information Service (NTIS)

Molecular electronic structures of the dianions and iron complexes of phthalocyanine and other macrocyclic compounds (i.e., tetrabenzoporphyrin, tetrazaporphyrin and porphyrin) which are of interest in oxygen electrocatalysis have been calculated using CN...

N. H. Sabelli L. K. Lee C. A. Melendres

1981-01-01

256

Influence of different peripheral substituents on the nonlinear optical properties of cobalt phthalocyanine core  

SciTech Connect

In this article, we show how the substituting different peripheral substituents around the cobalt phthalocyanine core correlate with nonlinear optical properties. We present the results on nonlinear optical properties of solution of cobalt phthalocyanine (CoPc), cobalt phthalocyanine with DNA-CTMA surfactant complex (CoPc-DNA-CTMA), and cobalt phthalocyanine with liquid crystal (CoPc-LC) measured by degenerate four-wave mixing (DFWM) method at the 532 nm wavelength region. We found that the values of third-order nonlinear optical susceptibility ({chi}{sup <3>}) of CoPc-LC and CoPc-DNA-CTMA increase in comparison with the value of the third-order nonlinear optical susceptibilities of CoPc. We supposed that this is caused by increase of the charge-transfer effects and of the dipole moments of the molecule with the increase of the chain length.

Derkowska, B.; Wojdyla, M.; Bala, W.; Jaworowicz, K.; Karpierz, M.; Grote, James G.; Krupka, O.; Kajzar, F.; Sahraoui, B. [Institute of Physics, N. Copernicus University, GrudziaPdzka 5/7, 87-100 Torun (Poland); Optics Division, Faculty of Physics, Warsaw University of Technology, Koszykowa 75, 00-681 Warsaw (Poland); Air Force Research Laboratory Materials and Manufacturing Directorate, Wright-Patterson Air Force Base, 3005 Hobson Way, Dayton, Ohio 45433-7707 (United States); Laboratory POMA, UMR CNRS 6136, University of Angers, 2 Boulevard Lavoisier, 49045 Angers (France)

2007-04-15

257

In search of the main properties of phthalocyanines participating in toxicity against cyanobacteria.  

PubMed

Phthalocyanines are promising photosensitizers for use in various branches of science including nanotechnology. In the presence of visible light and diatomic oxygen, phthalocyanines can react to produce singlet oxygen (1O2*), which has known inhibitory effects on cellular growth and metabolic activity, although other mechanisms may be involved. The present work focuses on the properties of phthalocyanines (atom charge densities, singlet oxygen production, inhibition effects at various irradiances) contributing to toxicity against the cyanobacteria, Synechococcus nidulans. Our results indicate that positive charge densities at peripheral parts of substituents exhibit greater inhibitory effects against S. nidulans than the amount of singlet oxygen produced, potentially by binding to negatively charged membranes on the cell surface. The weak effect of 1O2* was further demonstrated by a 10% increase in phthalocyanine toxicity (the maximal inhibition detected) when the irradiance increased 3-fold from 1200 to 4000 lux. PMID:19846205

Jancula, Daniel; Marsálek, Blahoslav; Novotná, Zlatica; Cerný, Jirí; Karásková, Marie; Rakusan, Jan

2009-12-01

258

Spectroscopic insights on imidazole substituted phthalocyanine photosensitizers: Fluorescence properties, triplet state and singlet oxygen generation.  

PubMed

Imidazole substituted metal phthalocyanine (Pc) complexes were synthesized. UV-vis absorption, steady state and time-resolved fluorescence, as well as laser flash photolysis were used to measure the photophysical and photosensitizing properties. All the imidazole-phthalocyanine conjugates show high ?T (quantum yield of excited triplet formation), high ?? (singlet oxygen formation yield, >0.50) and good fluorescence properties (quantum yield ?f>0.20 and lifetime ?f>3.0 ns). Compared to the unsubstituted Pc, both ?- and ?-imidazole substitutions result in the remarkable decrease in ?f and ?f, but the ?-substitution is stronger. The imidazole substitution, on the other hand, causes the increase of ?T, ?T, and ?? values. Magnesium phthalocyanine (MgPc) is more susceptible to the substitution than zinc phthalocyanine (ZnPc). The mechanism responsible for the result is suggested based on the involvement of intramolecular photoinduced electron transfer. The high ?? and appropriate fluorescence properties make the Pcs good candidate for PDT photosensitizers. PMID:24997445

Zhang, Xian-Fu; Lin, Yong; Guo, Wenfeng; Zhu, Jingzhong

2014-12-10

259

Comparative semiempirical study of oxygen binding to model iron complexes of phthalocyanine and porphyrin  

SciTech Connect

Molecular electronic structures of the danions and iron complexes of phthalocyanine and related macrocyclic compounds (i.e., tetrabenzoporphyrin, tetraazaporphyrin, and porphyrin) which are of interest in electrocatalysis have been calculated with semiempirical all-valence electron methods. Significant differences are found between the electron distributions in phthalocyanine and porphyrin dianions due mainly to the nature of the atom bridging the indole or pyrrole ligands. Iron complexes of both macrocyclics also show significant electronic differences, with the iron atom in an intermediate spin state in phthalocyanine and a high spin state in porphyrin. Oxygen binding to the iron center in model compounds of both complexes was also studied. The side-on configuration appears to be preferred in the oxygen-phthalocyanine system and end-on bonding in the oxygen-porphyrin complex.

Sabelli, N.H. (Univ. of Illinois, Chicago); Melendres, C.A.

1982-10-28

260

Targeted drug delivery and enhanced intracellular release using functionalized liposomes  

NASA Astrophysics Data System (ADS)

The ability to target cancer cells using an appropriate drug delivery system can significantly reduce the associated side effects from cancer therapies and can help in improving the overall quality of life, post cancer survival. Integrin alpha5beta1 is expressed on several types of cancer cells, including colon cancer and plays an important role in tumor growth and metastasis. Thus, the ability to target the integrin alpha 5beta1 using an appropriate drug delivery nano-vector can significantly help in inhibiting tumor growth and reducing tumor metastasis. The work in this thesis focuses on designing and optimizing, functionalized stealth liposomes (liposomes covered with polyethylene glycol (PEG)) that specifically target the integrin alpha5beta1. The PEG provides a steric barrier allowing the liposomes to circulate in the blood for longer duration and the functionalizing moiety, PR_b peptide specifically recognizes and binds to integrin alpha5beta1 expressing cells. The work demonstrates that by optimizing the amount of PEG and PR_b on the liposomal interface, nano-vectors can be engineered that bind to CT26.WT colon cancer cells in a specific manner and internalize through alpha 5beta1-mediated endocytosis. To further improve the efficacy of the system, PR_b functionalized pH-sensitive stealth liposomes that exhibit triggered release under mild acidic conditions present in endocytotic vesicles were designed. The study showed that PR_b functionalized pH-sensitive stealth liposomes, undergo destabilization under mildly acidic conditions and incorporation of the PR_b peptide does not significantly affect the pH-sensitivity of the liposomes. PR_b functionalized pH-sensitive stealth liposomes bind to CT26.WT colon carcinoma cells that express integrin alpha5beta 1, undergo cellular internalization, and release their load intracellularly in a short period of time as compared to other formulations. PR_b-targeted pH-sensitive stealth liposomes encapsulating 5-fluorouracil (5-FU) show significantly higher cytotoxicity than the PR_b-targeted inert stealth liposomes and the non-targeted stealth liposomes (both pH-sensitive and inert). The studies demonstrated that optimized PR_b functionalized pH sensitive liposomes have the potential to deliver a payload, such as chemotherapeutic agents, directly to colon cancer cells in an efficient and specific manner.

Garg, Ashish

261

Liposomal Drug Products: A Quality by Design Approach  

NASA Astrophysics Data System (ADS)

Quality by Design (QbD) principles has been applied to the development of two liposomal formulations, containing a hydrophilic small molecule therapeutic (Tenofovir) and a protein therapeutic (superoxide dismutase). The goal of the research is to provide critical information on 1) how to reduce the preparation variability in liposome formulations, and 2) how to increase drug encapsulation inside liposomes to reduce manufacturing cost. Most notably, an improved liposome preparation method was developed which increased the encapsulation efficiency of hydrophilic molecules. In particular, this method allows for very high encapsulation efficiency. For example, encapsulation efficiencies of up to 50% have been achieved, whereas previously only 20% or less have been reported. Another significant outcome from this research is a first principle mathematical model to predict the encapsulation efficiency of hydrophilic drugs in unilamellar liposomes. This mathematical model will be useful in: formulation development to rapidly achieve optimized formulations; comparison of drug encapsulation efficiencies of liposomes prepared using different methods; and assisting in the development of suitable process analytical technologies to achieve real-time monitoring and control of drug encapsulation during manufacturing. A novel two-stage reverse dialysis in vitro release testing method has also been developed for passively targeted liposomes, which uses the first stage to mimic the circulation of liposomes in the body and the second stage to imitate the drug release process at the target. The developed in vitro release testing method can be used to distinguish formulations with varied compositions for quality control testing purposes. This developed method may pave the way to the development of more biorelevant quality control testing methods for liposomal drug products in the future. The QbD case studies performed in this research are examples of how this approach can be used to obtain design space for liposome products to achieve the desired in vivo product performance criteria. From an industrial perspective, this study provides an in-depth understanding of the parameters (risks) involved in liposome formulation and processing. From a regulatory perspective, the development of QbD principles for liposomal drug products will facilitate their regulation assuring safety and efficacy of these complex delivery systems.

Xu, Xiaoming

262

Unit cell parameters for a new crystalline polymorph of lead phthalocyanine and for two polymorphs of magnesium phthalocyanine  

NASA Astrophysics Data System (ADS)

X ray diffraction techniques were employed to examine the lattice metallophthalocyanines magnesium phthalocyanine (MgPc) and lead phthalocyanine (PbPc) and unit cell dimensions were determined. The specimens were purified by means of entrainer gas sublimation, wherein raw dyes were sublimed with N2, then allowed to separate out by temperature dependent recrystallization. X ray diffraction measurements were made in the zone where temperature dropped from 430 C to 340 C (PbPc) and where deposition occurred in a transition from 470 C to 400 C (MgPc). Additional diffraction studies were made of a ground powder of the deposits. Unit parameters for PbPc and MgPc in monoclinic and monoclinic, space group, undetermined forms, respectively, are provided. A least squares procedure was employed to determine the d-spacings exceeding 0.26 nm in the MgPc powder. The results were indicative of an alpha type structure. The formation characterization is considered critical if the dyes are to be employed in photoelectric applications.

Bluhm, T. L.; Wagner, H. J.; Loutfy, R. O.

1983-02-01

263

Modeling the interactions of phthalocyanines in water: From the Cu(II)-tetrasulphonate to the metal-free phthalocyanine  

NASA Astrophysics Data System (ADS)

A quantum and statistical study on the effects of the ions Cu2+ and SO3- in the solvent structure around the metal-free phthalocyanine (H2Pc) is presented. We developed an ab initio interaction potential for the system CuPc-H2O based on quantum chemical calculations and studied its transferability to the H2Pc-H2O and [CuPc(SO3)4]4--H2O interactions. The use of the molecular dynamics technique allows the determination of energetic and structural properties of CuPc, H2Pc, and [CuPc(SO3)4]4- in water and the understanding of the keys for the different behaviors of the three phthalocyanine (Pc) derivatives in water. The inclusion of the Cu2+ cation in the Pc structure reinforces the appearance of two axial water molecules and second-shell water molecules in the solvent structure, whereas the presence of SO3- anions implies a well defined hydration shell of about eight water molecules around them making the macrocycle soluble in water. Debye-Waller factors for axial water molecules have been obtained in order to examine the potential sensitivity of the extended x-ray absorption fine structure technique to detect the axial water molecules.

Martín, Elisa I.; Martínez, Jose M.; Marcos, Enrique Sánchez

2011-01-01

264

Tuning pH sensitivities of zinc phthalocyanines in ionic liquid modified matrices  

Microsoft Academic Search

Phthalocyanine dyes are clinically important bright fluorophores with many desirable properties. Their absorption and emission maxima in near infrared region make them proper tool for optical probing of biologically relevant materials and optical-chemical-sensing purposes. In this work we have shown that pH sensitivities of the phthalocyanines can be manipulated as desired. This property makes the Pcs very proper photosensitizers for

Sevinc Zehra Topal; Kadriye Ertekin; Ay?e Gül Gürek; Berrin Yenigul; Vefa Ahsen

2011-01-01

265

Communication: Influence of graphene interlayers on the interaction between cobalt phthalocyanine and Ni(111).  

PubMed

The influence of graphene interlayers on electronic interface properties of cobalt phthalocyanine on Ni(111) is studied using both photoemission and X-ray absorption spectroscopy. A charge transfer associated with a redistribution of the d-electrons at the Co-atom of the phthalocyanine occurs at the interface to Ni(111). Even a graphene buffer layer cannot prevent the charge transfer at the interface to Ni(111); however, the detailed electronic situation is different. PMID:23464132

Uihlein, Johannes; Peisert, Heiko; Glaser, Mathias; Polek, Ma?gorzata; Adler, Hilmar; Petraki, Fotini; Ovsyannikov, Ruslan; Bauer, Maximilian; Chassé, Thomas

2013-02-28

266

Enhanced reverse saturable absorption and optical limiting in heavy-atom-substituted phthalocyanines  

Microsoft Academic Search

The reverse saturable absorption and optical limiting response of metal phthalocyanines can be enhanced by using the heavy-atom effect. Phthalocyanines containing heavy metal atoms, such as In, Sn, and Pb show nearly a factor of two enhancement in the ratio of effective excited-state to ground-state absorption cross sections compared to those containing lighter atoms, such as Al and Si. In

Joseph W. Perry; Kamjou Mansour; Seth R. Marder; Kelly J. Perry; Daniel Alvarez Jr.; Ingrid Choong

1994-01-01

267

Spectrophotometric study of mercaptide ion-cobalt phthalocyanine-oxygen ternary system  

SciTech Connect

Cobalt(II) phthalocyanine undergoes a one-electron reduction by sodium mercaptide in a N,N-dimethylformamide medium under anaerobic conditions. A ternary complex of cobalt phthalocyanine with thiolate and oxygen is formed during contact with oxygen in the presence of excess thiolate ions. The complex has sensitivity to light and decomposes in the presence of aqueous alkali. The alternative possibility of a formation of a dithiolate derivative of cobalt(III) is less probable.

Kozlyak, E.I.; Erokhin, A.S.; Yatsimirskii, A.K.; Berezin, I.V.

1986-10-10

268

Spectroelectrochemical characterisation of Langmuir–Schaefer films of heteroleptic phthalocyanine complexes. Potential applications  

Microsoft Academic Search

The Langmuir–Schaefer technique has been used to fabricate ordered monolayers of novel heteroleptic double and triple-decker phthalocyanine derivatives. The molecules studied include a double-decker mixed porphyrinate and naphthalocyaninate lanthanum(III) compound and a europium triple-decker molecule where one of the rings is a substituted porphyrin and the two remaining rings are substituted phthalocyanine macrocycles.The materials and their films have been characterised

C. Apetrei; S. Casilli; M. De Luca; L. Valli; J. Jiang; M. L. Rodríguez-Méndez; J. A. De Saja

2006-01-01

269

Solvent-free synthesis of soluble, near-IR absorbing titanyl phthalocyanine derivatives.  

PubMed

Solvent-free synthesis of a series of alkylthio-substituted titanyl phthalocyanine (TiOPc) derivatives starting from the corresponding phthalonitriles (Pn) is reported. This methodology eliminates the formation of the unmetalated phthalocyanine (H2Pc), a side product that makes purification difficult. The alkylthio groups on the reported derivatives enhance solubility in common organic solvents and shift the absorption to the near-IR region. PMID:21028904

Mayukh, Mayank; Sema, Clarissa M; Roberts, Jessica M; McGrath, Dominic V

2010-11-19

270

X-ray study of structural reorganization in phthalocyanine containing Langmuir Blodgett heterostructures  

NASA Astrophysics Data System (ADS)

Langmuir-Blodgett heterostructures containing phthalocyanine and fatty acid salt multilayers were studied by X-ray scattering using synchrotron radiation. Two structural reorganizations of the film were registered after the thermal treatment. The first phase transition took place after heating till the melting point of the fatty acid and the second one, at a higher temperature, but before the phthalocyanine melting point. Models of the molecular organization for all three film packings were suggested.

Erokhin, Victor; Carrara, Sandro; Paternolli, Cristina; Valkova, Larisa; Bernstorff, Sigrid; Nicolini, Claudio

2005-05-01

271

Electronic structure of iron phthalocyanine and its analogs: a theoretical study  

SciTech Connect

Molecular electronic structures of the dianions and iron complexes of phthalocyanine and other macrocyclic compounds (i.e., tetrabenzoporphyrin, tetrazaporphyrin and porphyrin) which are of interest in oxygen electrocatalysis have been calculated using CNDO/INDO molecular orbital methods. Significatn differences are found between the electron distributions in phthalocyanine and porphyrin due mainly to a difference in the nature of the atom bridging the indole and pyrrole ligands. Both iron complexes of phthalocyanine and porphyrin have a quintuplet molecular electronic ground state with iron in an intermediate spin state in the former and high spin in the latter. Binding of oxygen to the iron center in model compounds of iron phthalocyanine and iron porphyrin was studied. Side-on configuration appears to be preferred in the oxygen-phthalocyanine system and end-on bonding in the oxygen-porphyrin complex. The effect of catalyst support, electron delocalization by dimerization, and protons in solution on the oxygen binding by iron phthalocyanine was also examined and preliminary results are described. 2 figures, 3 tables.

Sabelli, N.H.; Lee, L.K.; Melendres, C.A.

1981-04-01

272

The modulation of the permeability and the cellular uptake of liposome by stable anchoring of lipid-conjugated pluronic on liposome.  

PubMed

Controlling the permeability of liposome is important to modulate the release behavior of drug from the liposome. Pluronic F127 (PF127) is a biocompatible tri-block copolymer, which can interact with lipid bilayer of liposomes and make leakages that allow the release of hydrophilic substance from liposome interior. However, the interaction between unmodified PF127 and lipid bilayer is not very strong and the incorporated PF127 is easily desorbed from the liposomes in an infinite reservoir condition. In this paper, we conjugated lipid molecule (1,2-distearoyl-sn-glycero-3-phosphoethanolamine [DSPE]) at the both ends of PF127 to increase the interaction between polymer and liposome. This lipid-conjugated PF127 was incorporated into the liposomes and it remained stably without desorption from liposomes in an infinite reservoir condition. The stably bound PF127 increased the release rate of hydrophilic drug from liposomes in a dose-dependent manner. Moreover, the lipid-conjugated PF127 changed the surface property of liposomes and inhibited its cellular uptake when the incorporated amount was above 2.5 wt%. In conclusion, the lipid-conjugated PF127 could function as a stable anchor on the lipid bilayer of liposomes to control the permeability as well as provide the hydrophilic surface of liposomes in an open system like an in vivo situation. PMID:24724502

Kim, Jong Chul; Chungt, Yong-Il; Kim, Young Ha; Tae, Giyoong

2014-01-01

273

Thermal and photic stimuli-responsive polydiacetylene liposomes with reversible fluorescence  

NASA Astrophysics Data System (ADS)

A novel reversible fluorescent switch of a polydiacetylene liposome (PDA liposome) was realized by alternating heating and UV irradiation processes. The reversible fluorescence switching of the PDA liposome was mainly caused by the microstructural changes of the PDA backbone in the PDA liposomes under the alternating conditions of heating and UV irradiation.A novel reversible fluorescent switch of a polydiacetylene liposome (PDA liposome) was realized by alternating heating and UV irradiation processes. The reversible fluorescence switching of the PDA liposome was mainly caused by the microstructural changes of the PDA backbone in the PDA liposomes under the alternating conditions of heating and UV irradiation. Electronic supplementary information (ESI) available: The preparation method, cytotoxicity and biocompatibility assays and HREM images of PDA liposomes. See DOI: 10.1039/c3nr00954h

Yan, Xiaojuan; An, Xueqin

2013-06-01

274

[Advance in studies on NGR peptide modified liposome and its anti-tumor performance].  

PubMed

Aspargine-glycine-arginine (NGR)-containing peptides are targeted peptides which can be integrated with CD13 receptors on tumor vascular endothelial cells. NGR peptides are connected to liposomes to obtain NGR peptide-modified liposomes. By intravenous injection of these liposomes, NGR peptides can be combined with CD13 receptors on tumor vascular endothelial cells, position liposomes in tumor tissues, and concentrate drug in liposomes in tumor, so as to enhance the antitumor effect. The article starts with NGR peptides, summarizes definition of NGR, NGR peptide-modified liposomes, strengths and weaknesses of NGR peptide-modified liposomes in antitumor and the latest study orientation of NGR peptide-modified liposomes, and looks into the future of studies on NGR peptide-modified liposomes. PMID:24079222

Wang, Yong; Chen, Jun; Lin, Ai-Hu; Fang, Yun

2013-07-01

275

Effect of adsorption of bovine serum albumin on liposomal membrane characteristics.  

PubMed

The effect of adsorption of bovine serum albumin (BSA) on the membrane characteristics of liposomes at pH 7.4 was examined in terms of zeta potential, micropolarity, microfluidity and permeability of liposomal bilayer membranes, where negatively charged L-alpha-dipalmitoylphosphatidylglycerol (DPPG)/L-alpha-dipalmitoylphosphatidylcholine (DPPC), negatively charged dicetylphosphate (DCP)/DPPC and positively charged stearylamine (SA)/DPPC mixed liposomes were used. BSA with negative charges adsorbed on negatively charged DPPG/DPPC mixed liposomes but did not adsorb on negatively charged DCP/DPPC and positively charged SA/DPPC mixed liposomes. Furthermore, the adsorption amount of BSA on the mixed DPPG/DPPC liposomes increased with increasing the mole fraction of DPPG in spite of a possible electrostatic repulsion between BSA and DPPG. Thus, the adsorption of BSA on liposomes was likely to be related to the hydrophobic interaction between BSA and liposomes. The microfluidity of liposomal bilayer membranes near the bilayer center decreased by the adsorption of BSA, while the permeability of liposomal bilayer membranes increased by the adsorption of BSA on liposomes. These results are considered to be due to that the adsorption of BSA brings about a phase separation in liposomes and that a temporary gap is consequently formed in the liposomal bilayer membranes, thereby the permeability of liposomal bilayer membranes increases by the adsorption of BSA. PMID:11087982

Yokouchi; Tsunoda; Imura; Yamauchi; Yokoyama; Sakai; Abe

2001-02-01

276

Cholesterol Derivatives Based Charged Liposomes for Doxorubicin Delivery: Preparation, In Vitro and In Vivo Characterization  

PubMed Central

Cholesterol plays a critical role in liposome composition. It has great impact on the behavior of liposome in vitro and in vivo. In order to verify the possible effects from cholesterol charge, surface shielding and chemical nature, two catalogs of liposomes with charged and PEGylated cholesterols were synthesized. Anionic liposomes (AL) and cationic liposomes (CL) were prepared, with charges from hemisuccinate and lysine in cholesterol derivatives, respectively. Characteristics of different formulated liposomes were investigated after doxorubicin encapsulation, using neutral liposomes (NL) as control. Results showed that after PEGylation, AL and CL liposomes displayed prolonged retention release profile, while kept similar size distribution, encapsulation efficiency, low cytotoxicity and hemolysis comparing with NL. Confocal laser scanning microscopy and flow cytometry experiments confirmed the significantly higher cell uptake from AL and CL vesicles than the NL in mouse breast carcinoma and melanoma cells, human epithelial carcinoma and hepatoma cells. It was in accordance with our corresponding cellular mortality studies of DOX-loaded liposomes. The in vivo anti-tumor effect experiments from charged liposomes also presented much higher tumor inhibition effect (70% vs 45%, p < 0.05) than NL liposomes. This is the first time reporting anti-cancer effect from charged cholesterol liposome with/without PEGylation. It may give deeper understanding on the liposome formulation which is critical for liposome associated drug research and development.

Nie, Yu; Ji, Li; Ding, Hong; Xie, Li; Li, Li; He, Bin; Wu, Yao; Gu, Zhongwei

2012-01-01

277

Liposomes destabilize tRNA during heat stress.  

PubMed

Biomembranes play an important role in cellular response to heat stress. In this study, we focus on the interaction between liposomes and tRNA. Upon heat treatment we determined circular dichroism spectra of tRNA in presence of liposomes prepared from POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) and cholesterol (Ch). To compare thermal stability, midpoint temperature (T(m)) of tRNA was calculated from normalized theta(208). Addition of POPC/Ch liposomes decreased the T(m) value of tRNA from 48 degrees C to 38 degrees C. We conclude that POPC/Ch liposomes interact with tRNA and destabilize its conformation under heat stress. PMID:20401904

Suga, Keishi; Umakoshi, Hiroshi; Tomita, Hibiki; Tanabe, Tomoyuki; Shimanouchi, Toshinori; Kuboi, Ryoichi

2010-05-01

278

Liposomal packaging generates Wnt protein with in vivo biological activity.  

PubMed

Wnt signals exercise strong cell-biological and regenerative effects of considerable therapeutic value. There are, however, no specific Wnt agonists and no method for in vivo delivery of purified Wnt proteins. Wnts contain lipid adducts that are required for activity and we exploited this lipophilicity by packaging purified Wnt3a protein into lipid vesicles. Rather than being encapsulated, Wnts are tethered to the liposomal surface, where they enhance and sustain Wnt signaling in vitro. Molecules that effectively antagonize soluble Wnt3a protein but are ineffective against the Wnt3a signal presented by a cell in a paracrine or autocrine manner are also unable to block liposomal Wnt3a activity, suggesting that liposomal packaging mimics the biological state of active Wnts. When delivered subcutaneously, Wnt3a liposomes induce hair follicle neogenesis, demonstrating their robust biological activity in a regenerative context. PMID:18698373

Morrell, Nathan T; Leucht, Philipp; Zhao, Ludan; Kim, Jae-Beom; ten Berge, Derk; Ponnusamy, Karthik; Carre, A Lyonel; Dudek, Henryk; Zachlederova, Marie; McElhaney, Michael; Brunton, Shirley; Gunzner, Janet; Callow, Marinella; Polakis, Paul; Costa, Mike; Zhang, Xiaoyan M; Helms, Jill A; Nusse, Roel

2008-01-01

279

Liposomal delivery of boron to tumors for BNCT  

SciTech Connect

Results are reported on the use of liposomes to encapsulate boron containing compounds for use as a delivery vehicle to tumors. An increase in injected dose to the tumor in mammary glands of mice was realized.

Hawthorne, M.F.; Feakes, D.A.; Shelly, K. [Univ. of California, Los Angeles, CA (United States)

1994-12-31

280

Atmospheric-pressure guided streamers for liposomal membrane disruption  

NASA Astrophysics Data System (ADS)

The potential to use liposomes (LIPs) as a cellular model in order to study interactions of cold atmospheric-pressure plasma with cells is herein investigated. Cold atmospheric-pressure plasma is formed by a dielectric-barrier discharge reactor. Large multilamellar vesicle liposomes, consisted of phosphatidylcholine and cholesterol, are prepared by the thin film hydration technique, to encapsulate a small hydrophilic dye, i.e., calcein. The plasma-induced release of calcein from liposomes is then used as a measure of liposome membrane integrity and, consequently, interaction between the cold atmospheric plasma and lipid bilayers. Physical mechanisms leading to membrane disruption are suggested, based on the plasma characterization including gas temperature calculation.

Svarnas, P.; Matrali, S. H.; Gazeli, K.; Aleiferis, Sp.; Clément, F.; Antimisiaris, S. G.

2012-12-01

281

Liposomes with polyribonucleotides as model of precellular systems  

NASA Technical Reports Server (NTRS)

Three types of liposomes were prepared under anoxic conditions: from dipalmitoyl phosphatidyl choline (DPPC), from egg yolk phosphatidyl choline (PC), and from PC with cholesterol (PC:Chol). These were used for encapsulation of poly(U) and poly(C). It was found that 36 to 70 percent of the available liposome lipids and 2 to 5 percent of the polyribonucleotides could be entrapped. An enhanced encapsulation of poly(U) and poly(C) by all three types of liposomes was observed in the presence of 0.001 to 0.01 M Zn(2+), with the effect being greatest with DPPC. The presence of 1.0 M urea inhibited the formation of PC liposomes.

Baeza, Isabel; Ibanez, Miguel; Santiago, Carlos; Lazcano, Antonio; Arguello, Carlos

1987-01-01

282

Efficacy and toxicity of cisplatin liposomes modified with polyethylenimine.  

PubMed

The polycation transfection agent, polyethylenimine (PEI) was introduced into cisplatin (CDDP)-encapsulated liposomes by modification with amphiphilic PEI-cholesterol (PEI-Chol) to evaluate its potential application in chemotherapeutic drug delivery. Compared with unmodified neutral liposomes (CDDP-NL), the remarkable features of PEI-modified cationic liposomes (CDDP-CL) increased cytotoxicity attributed to enhanced cellular uptake and extended cellular retention resulting from endosome escape in vitro. In a H22 hepatoma-bearing mouse model, CDDP-CL reduced the nephrotoxicity associated with CDDP and had an antitumor activity similar to free drug, without inducing obvious system toxicity. These results confirm that the cationic modification of liposomes with PEI is efficient and safe for antitumor drug delivery. PMID:24791592

Sun, Xiaoyi; Chen, Jinliang; Gu, Xiaohui; Liang, Wenquan; Wang, Junbo

2014-04-01

283

Acoustical properties of individual liposome-loaded microbubbles.  

PubMed

A comparison between phospholipid-coated microbubbles with and without liposomes attached to the microbubble surface was performed using the ultra-high-speed imaging camera (Brandaris 128). We investigated 73 liposome-loaded microbubbles (loaded microbubbles) and 41 microbubbles without liposome loading (unloaded microbubbles) with a diameter ranging from 3-10 ?m at frequencies ranging from 0.6-3.8 MHz and acoustic pressures ranging from 5-100 kPa. The experimental data showed nearly the same shell elasticity for the loaded and unloaded bubbles, but the shell viscosity was higher for loaded bubbles compared with unloaded bubbles. For loaded bubbles, a higher pressure threshold for the bubble vibrations was noticed. In addition, an "expansion-only" behavior was observed for up to 69% of the investigated loaded bubbles, which mostly occurred at low acoustic pressures (?30 kPa). Finally, fluorescence imaging showed heterogeneity of liposome distributions of the loaded bubbles. PMID:23196203

Luan, Ying; Faez, Telli; Gelderblom, Erik; Skachkov, Ilya; Geers, Bart; Lentacker, Ine; van der Steen, Ton; Versluis, Michel; de Jong, Nico

2012-12-01

284

Pharmacokinetics of a 5-fluorouracil liposomal delivery system.  

PubMed Central

A liposomal delivery system was developed in an attempt to prolong ocular levels of 5-fluorouracil for glaucoma filtering surgery. The pharmacokinetics of the 5-fluorouracil liposomal delivery system were studied in normal pigmented rabbits with 5-fluorouracil labelled with carbon-14 (C-14). 14C 5-fluorouracil was incorporated into the liposomes at a concentration of 10 g/l and injected subconjunctivally in doses of 5 and 10 mg. Concentrations of 5-fluorouracil were assayed at 10 time intervals from 0.5 to 96 hours in cornea, sclera, and conjunctiva and at six time intervals from 0.5 to 12 hours in aqueous. Two peak concentrations were noted at approximately one and eight hours, with measurable levels present at 96 hours. This study demonstrates the ability of this liposomal delivery system to prolong levels of 5-fluorouracial in normal pigmented rabbits.

Simmons, S T; Sherwood, M B; Nichols, D A; Penne, R B; Sery, T; Spaeth, G L

1988-01-01

285

Avoiding failed reconstitution of ultradeformable liposomes upon dehydration.  

PubMed

Although freeze-drying is an ordinarily used technique to dehydrate conventional liposomes, we have found that ultradeformable liposomes (UDLs) suffered irreversible aggregation when rehydrated upon freeze-drying (99.4% water elimination), even in high sugar content (4/1 sucrose/lipid mass ratio). When dehydrated by speed vac and vacuum drying, two alternative techniques that rendered less pronounced dehydration (94.27 and 96.2% water elimination, respectively) and avoid ice formation, however, UDL could only be successfully rehydrated when vacuum dried in 4/1 sucrose/lipid mass ratios. Conventional liposomes, on the other hand, were successfully reconstituted upon dehydrated by the three methods in lower sugar content (2/1 sucrose/lipid mass ratio). These results indicated that the 27% mole sodium cholate within the UDL lipid matrix was responsible for a greater and differential mechanical sensitivity of the bilayers to the different dehydration stress, as compared to conventional liposomes. PMID:19429279

Montanari, J; Roncaglia, D I; Lado, L A; Morilla, M J; Romero, E L

2009-05-01

286

Optically Guided Controlled Release from Liposomes With Tunable Plasmonic Nanobubbles  

PubMed Central

A new method of optically guided controlled release was experimentally evaluated with liposomes containing a molecular load and gold nanoparticles (NPs). NPs were exposed to short laser pulses to induce transient vapor bubbles around the NPs, plasmonic nanobubbles, in order to disrupt the liposome and eject its molecular contents. The release efficacy was tuned by varying the lifetime and size of the nanobubble with the fluence of the laser pulse. Optical scattering by nanobubbles correlated to the molecular release and was used to guide the release. The release of two fluorescent proteins from individual liposomes has been directly monitored by fluorescence microscopy, while the generation of the plasmonic nanobubbles was imaged and measured with optical scattering techniques. Plasmonic nanobubble-induced release was found to be a mechanical, nonthermal process that requires a single laser pulse and ejects of the liposome contents within a millisecond timescale without damage to the molecular cargo and that can be controlled through the fluence of laser pulse.

Anderson, Lindsey; Hansen, Eric; Lukianova-Hleb, Ekaterina Y.; Hafner, Jason H.; Lapotko, Dmitri O.

2010-01-01

287

Plasma Protein Binding of Amphotericin B and Pharmacokinetics of Bound versus Unbound Amphotericin B after Administration of Intravenous Liposomal Amphotericin B (AmBisome) and Amphotericin B Deoxycholate  

Microsoft Academic Search

Unilamellar liposomal amphotericin B (AmBisome) (liposomal AMB) reduces the toxicity of this antifungal drug. The unique composition of liposomal AMB stabilizes the liposomes, producing higher sustained drug levels in plasma and reducing renal and hepatic excretion. When liposomes release their drug payload, unbound, protein-bound, and liposomal drug pools may exist simultaneously in the body. To determine the amounts of drug

Ihor Bekersky; Robert M. Fielding; Dawna E. Dressler; Jean W. Lee; Donald N. Buell; Thomas J. Walsh

2002-01-01

288

Technology of Liposomal Tiosens, Cifelin and Lysomustin for Industrial Purposes  

NASA Astrophysics Data System (ADS)

This work is devoted to the development of national antineoplastic drug (Tiosens, Cifelin, Lysomustin) liposomal dosage form (LDF) circuit technology and their manufacturing technology. In modern oncology liposomes, which are hollow phospholipid vesicles, are used as delivery systems protected drugs from biodegradation, and healthy cells from the toxic effect of chemotherapeutic agents. The technology of their production is stretching and multistage. It is also necessary to give consideration a lot of factors that influence on the finished product quality.

Sanarova, E. V.; Kotova, E. A.; Lantsova, A. V.

2012-02-01

289

Hyaluronic acid-coated liposomes for active targeting of gemcitabine.  

PubMed

The aim of this work was the preparation, characterization, and preliminary evaluation of the targeting ability toward pancreatic adenocarcinoma cells of liposomes containing the gemcitabine lipophilic prodrug [4-(N)-lauroyl-gemcitabine, C12GEM]. Hyaluronic acid (HA) was selected as targeting agent since it is biodegradable, biocompatible, and can be chemically modified and its cell surface receptor CD44 is overexpressed on various tumors. For this purpose, conjugates between a phospholipid, the 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE), and HA of two different low molecular weights 4800 Da (12 disaccharidic units) and 12,000 Da (32 disaccharidic units), were prepared, characterized, and introduced in the liposomes during the preparation. Different liposomal formulations were prepared and their characteristics were analyzed: size, Z potential, and TEM analyses underline a difference in the HA-liposomes from the non-HA ones. In order to better understand the HA-liposome cellular localization and to evaluate their interaction with CD44 receptor, confocal microscopy studies were performed. The results demonstrate that HA facilitates the recognition of liposomes by MiaPaCa2 cells (CD44(+)) and that the uptake increases with increase in the polymer molecular weight. Finally, the cytotoxicity of the different preparations was evaluated and data show that incorporation of C12GEM increases their cytotoxic activity and that HA-liposomes inhibit cell growth more than plain liposomes. Altogether, the results demonstrate the specificity of C12GEM targeting toward CD44-overexpressing pancreatic adenocarcinoma cell line using HA as a ligand. PMID:23791684

Arpicco, Silvia; Lerda, Carlotta; Dalla Pozza, Elisa; Costanzo, Chiara; Tsapis, Nicolas; Stella, Barbara; Donadelli, Massimo; Dando, Ilaria; Fattal, Elias; Cattel, Luigi; Palmieri, Marta

2013-11-01

290

Novel liposomal forms of antifungal antibiotics modified by amphiphilic polymers  

Microsoft Academic Search

A novel method was developed to incorporate macrocyclic polyene antibiotics, nystatin and amphotericin B, into liposomes prepared from the mixture of phosphatidylcholine and cholesterol (7: 3) or phosphatidylcholine, cholesterol,\\u000a and cardiolipin (7: 3: 1). Membranes of the liposomes were modified using the amphiphilic polymer N-vinylpyrrolidone with\\u000a the molecular mass (MM) of the polymer fragment of 4000 and a single terminal

I. A. Yamskov; A. N. Kuskov; K. K. Babievsky; B. B. Berezin; M. A. Krayukhina; N. A. Samoylova; V. E. Tikhonov; M. I. Shtilman

2008-01-01

291

Liposome-mediated gene transfer to lung isografts  

Microsoft Academic Search

Objectives: Our objectives were to determine the feasibility, efficacy, and safety of in vivo and ex vivo liposome-mediated gene transfer to lung isografts.Methods: Fischer rats were divided into three main groups: (1) Nontransplant setting: Liposome–chloramphenicol acetyl transferase cDNA was intravenously injected, and lungs were harvested at different time points: 2, 6, 12, and 24 hours; 2, 5, 8, and 21

Carlos H. R. Boasquevisque; Teng C. Lee; Bassem N. Mora; David Peterson; William O. Osburn; Matthew Bernstein; Wei Zhang; Jennifer B. Nietupski; Ronald K. Scheule; Joel D. Cooper; Mitchell D. Botney; G. Alexander Patterson

1997-01-01

292

Insertion of a Glycosylphosphatidylinositol-Anchored Enzyme into Liposomes  

Microsoft Academic Search

Incorporation of alkaline phosphatase (AP), a glycosylphosphatidylinositol (GPI)-anchored protein, into liposomes containing detergent, followed by detergent removal with hydrophobic resin was performed. Incorporation media were collected during different steps of detergent removal and were analyzed by flotation in sucrose gradient. The presence of protein was checked by measuring enzymatic activity, while the presence of 3H-radio-labelled liposomes was followed by determination

F. Ronzon; S. Morandat; B. Roux; M. Bortolato

2004-01-01

293

Atrioventricular block related to liposomal amphotericin B.  

PubMed

Atrioventricular block can occur in normal children, young adults or athletes. It is also associated with underlying heart disease or occurs as a drug adverse effect. Amphotericin B is used in the treatment of invasive fungal infections. Cardiac toxicity is a rare adverse reaction. We report the case of a 9-month girl, admitted in the paediatric intensive care unit with cytomegalovirus pneumonitis. During hospitalisation the patient developed a systemic fungic infection and was medicated with liposomal amphotericin B. On the third day of treatment she began repeated episodes of bradycardia with spontaneous reversion. The investigation revealed a second-degree atrioventricular block. We excluded the misplacement of the central catheter, myocarditis or structural cardiomyopathy and suspended amphotericin. After 8?days, the bradycardia episodes ceased what was consistent with the drug's half-life. Amphotericin cardiotoxic mechanism is still unclear. It may be related with alteration of myocardial membrane depolarisation. PMID:24907206

Sanches, Bruno Fernandes; Nunes, Pedro; Almeida, Helena; Rebelo, Mónica

2014-01-01

294

Osmotic water permeability in glycoprotein containing liposomes.  

PubMed

The kinetics of osmotic water permeability in proteoliposomes containing alpha 1-acid glycoprotein was investigated by means of stopped-flow spectrophotometry. A biphasic time-course of scattered light with time was registered. The rate constants calculated from fits to an exponential function in the first phase were proportional to the final medium osmolarity. The apparent second order rate constants Kapp (Osm-1 sec-1) were determined at different glycoprotein concentrations in the original mixture for preparation of proteoliposomes. The value of Kapp at lipid:glycoprotein weight ratio = 1 was plotted in Arrhenius coordinates. The calculated activation energy for water permeation through the lipid bilayer suggests that eventual channel mechanism may be involved due to the presence of glycoprotein molecule in the liposomes. PMID:3431542

Neitchev, V Z; Kostadinov, A P

1987-01-01

295

[Liposomal-amphotericin B efficacy and safety].  

PubMed

Liposomal amphotericin B (L-AMB), a lipid-based amphotericin B formulation, has been used in Japan since June 2006 to treat fungal infection. In the 3 years since L-AMB was launched, few reports have been made on its status. To ensure its appropriate use, we restrospectively reviewed its efficacy and safety in treating fungal infections. 25 subjects with fungal infection treated with L-AMB from April 2007 until February 2008. Of those, 16 showed clinical improvement. Elevated serum creatinine occurred in 1 and decreased serum potassium in 6. We found a positive relationship between the serum potassium decrease and L-AMB dose. Logistic regression analysis of this relationship showed that serum potassium tended to fall on day 5 to 6 of L-AMB administration. While L-AMB appears highly effective in fungal infection, it requires serum potassium monitoring to ensure patient safety. PMID:20420165

Hamada, Yukihiro; Komatsu, Toshiaki; Seto, Yoshinori; Matsubara, Hajime; Kume, Hikaru; Sunakawa, Keisuke; Yago, Kazuo

2010-03-01

296

Aluminium phthalocyanine chloride thin films for temperature sensing  

NASA Astrophysics Data System (ADS)

This study presents the fabrication and temperature sensing properties of sensors based on aluminium phthalocyanine chloride (AlPcCl) thin films. To fabricate the sensors, 50-nm-thick electrodes with 50-?m gaps between them are deposited on glass substrates. AlPcCl thin films with thickness of 50-100 nm are deposited in the gap between electrodes by thermal evaporation. The resistance of the sensors decreases with increasing thickness and the annealing at 100 °C results in an increase in the initial resistance of sensors up to 24%. The sensing mechanism is based on the change in resistance with temperature. For temperature varying from 25 °C to 80 °C, the change in resistance is up to 60%. Simulation is carried out and results obtained coincide with experimental data with an error of ±1%.

Muhammad Tariq Saeed, Chani; Abdullah, M. Asiri; Kh., S. Karimov; Atif, Khan Niaz; Sher Bhadar, Khan; Khalid., A. Alamry

2013-11-01

297

Magnetism and multiplets in Fe-phthalocyanine molecules  

NASA Astrophysics Data System (ADS)

Magnetism and multiplets for Fe-phthalocyanine molecules were investigated based on the constraint density functional theory (DFT) by imposing a density matrix constraint on the d-orbital occupation numbers. We demonstrate that for a single FePc molecule, there are three stationary states of multiplets, 3 E g , 3 A 2 g , and 3 B 2 g , and that the magnetic anisotropy (MA) strongly depends on the multiplet structures. The ground state of the 3 A 2 g obtained from the constraint DFT total energy calculations has planar MA, with the spin moments pointing along the molecule's planar direction. The columnar stacking structure for ?-FePc, with the ground state of the 3 E g , shows planar MA.

Kitaoka, Yukie; Nakamura, Kohji; Akiyama, Toru; Ito, Tomonori; Weinert, M.; Freeman, A. J.

2013-08-01

298

Correlation dependences in infrared spectra of metal phthalocyanines  

SciTech Connect

Metal-phthalocyanine (MPc) complexes CoPc, CuPc, CuPcCl{sub 15-16}, CuPc(4-NO{sub 2}-5-OPh){sub 4}, CuPc(4-CH{sub 2}-phthalimide){sub 4}, CuPc(4-NO{sub 2}-5-NHPhBr){sub 4}, PdPc, MgPc, PbPc, EuOAcPc, SmOAcPc, SmPc{sub 2}, and YOAcPc were obtained and studied using IR spectroscopy. The correlation between the shift of the absorption band maximum in the range of 1100-1600 cm{sup -1} and the atomic radius of template metal is found. It is shown that the planarity of the macrocycle of peripherally substituted CuPc can be estimated from the characteristics of the IR spectra.

Ziminov, A. V., E-mail: ziminov@yandex.ru; Ramsh, S. M. [Technical University, St. Petersburg Technological Institute (Russian Federation); Terukov, E. I.; Trapeznikova, I. N. [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation); Shamanin, V. V. [Russian Academy of Sciences, Institute of Macromolecular Compounds (Russian Federation); Yurre, T. A. [Technical University, St. Petersburg Technological Institute (Russian Federation)

2006-10-15

299

Laser deposition of sulfonated phthalocyanines for gas sensors  

NASA Astrophysics Data System (ADS)

Thin layers of nickel and copper tetrasulfonated phthalocyanines (NiPcTS and CuPcTS) were prepared by Matrix Assisted Pulsed Laser Evaporation method. The depositions were carried out with KrF excimer laser (energy density of laser radiation EL = 0.1-0.5 J cm-2) from dimethylsulfoxide matrix. For both materials the ablation threshold EL-th was determined. The following properties of deposited layers were characterized: (a) chemical composition (FTIR spectra); (b) morphology (SEM and AFM portraits); and (c) impedance of gas sensors based on NiPcTS and CuPcTS layers in the presence of two analytes - hydrogen and ozone. The prepared sensors exhibit response to 1000 ppm of hydrogen and 100 ppb of ozone even at laboratory temperature.

Fitl, Premysl; Vrnata, Martin; Kopecky, Dusan; Vlcek, Jan; Skodova, Jitka; Bulir, Jiri; Novotny, Michal; Pokorny, Petr

2014-05-01

300

Phthalocyanines as photosensitizing agents for tumors--mechanism of action  

NASA Astrophysics Data System (ADS)

Aluminum phthalocyanine (AlPc) is a second-generation photosensitizer under study for photodynamic therapy (PDT) of cancer. Its mechanism of action is not known. Fluoride appears to be a powerful probe for the mechanistic study of AlPc derivatives. F- forms a complex with the Al ligand, resulting in drastically reduced AlPc-induced phototoxicity. This is due to a modified binding of AlPc with certain target proteins, resulting in inhibition of electron transfer reactions (type I) but not singlet oxygen reactions (type II). In Chinese hamster ovary (CHO) cell membranes, Na+/K+-ATPase activity is selectively protected by F- from photosensitized inhibition by AlPc, suggesting that this enzyme may be a critical target for AlPc-PDT. Another cellular response, not interfered with by F-, is a transient increase of cytoplasmic free Ca2+ after AlPc-PDT. This increase was shown to trigger the induction of a recovery process.

Ben-Hur, Ehud

1994-03-01

301

Order on disorder: Copper phthalocyanine thin films on technical substrates  

SciTech Connect

We have studied the molecular orientation of the commonly used organic semiconductor copper phthalocyanine (CuPC) grown as thin films on the technically relevant substrates indium tin oxide, oxidized Si, and polycrystalline gold using polarization-dependent x-ray absorption spectroscopy, and compare the results with those obtained from single crystalline substrates [Au(110) and GeS(001)]. Surprisingly, the 20{endash}50 nm thick CuPC films on the technical substrates are as highly ordered as on the single crystals. Importantly, however, the molecular orientation in the two cases is radically different: the CuPC molecules stand on the technical substrates and lie on the single crystalline substrates. The reasons for this and its consequences for our understanding of the behavior of CuPC films in devices are discussed. {copyright} 2001 American Institute of Physics.

Peisert, H.; Schwieger, T.; Auerhammer, J. M.; Knupfer, M.; Golden, M. S.; Fink, J.; Bressler, P. R.; Mast, M.

2001-07-01

302

Nonlinear Optothermal Properties of Metal-Free Phthalocyanine  

NASA Technical Reports Server (NTRS)

The nonlinear optical properties of metal-free phthalocyanine (MFPC) thin films were examined using the second harmonic at 532 nm from a pulsed Nd:YAG laser, and the cw He-Ne , and Ar+ lasers. The He-Ne laser transmission at fixed input intensity was found to increase temporally within a time scale of twelve hours. The origin of this temporal change of transmission is discussed. The third order nonlinear susceptibilities (chi (exp(3))) by four-wave mixing were measured for films of different thickness. The saturation intensity of MFPC, and its absorption cross section, at 633 nm from a He-Ne laser, are reported. An optical bistability was recorded using a He-Ne laser. An AND logic gate was also demonstrated in the system. These phenomena in the system are attributed to refractive index modulation by thermal excitations.

Abdeldayem, Hossin A.; Frazier, Donald O.; Penn, Benjamin G.; Smith, David D.; Banks, Curtis E.

1998-01-01

303

Characterization of hot wall grown silver phthalocyanine films  

NASA Astrophysics Data System (ADS)

Silver phthalocyanine (AgPc) has attracted considerable interest because of its outstanding chemical stability, optical and electrical properties, and wide variety of potential applications in modern optical recording and optoelectronic devices. To improve the performance of devices based on AgPc, hot wall technique has been used to grow thin layers of AgPc onto the glass substrates kept at different temperatures in a vacuum of 10-5 Torr. The films so obtained are annealed and studied for structural, electrical, and optical characterization. The x-ray diffraction and scanning electron microscopy pattern of these films show a crystalline behavior of films. The films deposited at higher substrate temperature suggest the formation of more ordered and crystalline films. An analysis of optical absorption measurements on the films indicates that the interband transition energies lie in the range 4.1-4.13 eV.

Gupta, Himani; Bedi, R. K.; Mahajan, Aman

2007-10-01

304

Anomalous photoelectric emission from Ag on zinc-phthalocyanine film  

NASA Astrophysics Data System (ADS)

Photoelectric emission from organic and metal thin films is generally observed with irradiation of photon energy larger than 4 eV. In this paper, however, we report photoelectric emission from Ag on a zinc-phthalocyanine (ZnPc) layer at a photon energy of 3.4 eV. The threshold energy for this photoelectric emission is much smaller than the work function of Ag estimated by conventional photoelectron spectroscopy. The photoelectric emission by low-energy photons is significant for Ag thicknesses of less than 1 nm. Photoelectron spectroscopy and morphological study of the Ag/ZnPc suggest that the anomalous photoelectric emission from the Ag surface is caused by a vacuum level shift at the Ag/ZnPc interface and by surface plasmons of the Ag nanoparticles.

Tanaka, Senku; Otani, Tomohiro; Fukuzawa, Ken; Ogawa, Koji; Azuma, Junpei; Yamamoto, Isamu; Takahashi, Kazutoshi; Kamada, Masao; Hiromitsu, Ichiro

2014-05-01

305

Magnetic properties of phthalocyanine-based organometallic nanowire  

NASA Astrophysics Data System (ADS)

Using first principles calculations, we investigate the electronic and magnetic properties of transition metal phthalocyanine (M-Pc, M = Cr, Mn, Co, Ni, Cu, and Zn) nanowire (M-PcNW). Our calculations show that Ni-PcNW and Zn-PcNW are nonmagnetic, while Cr-PcNW and Cu-PcNW are antiferromagnetic with small energy difference and Co-PcNW show paramagnetic due to their long spin coherence length. Most importantly, we predicate that Mn-PcNW frameworks display long-ranged ferromagnetic spin ordering, offering strong spin polarization around Fermi level. Moreover, Mn-PcNW frameworks are half-metals, which make Mn-PcNW frameworks ideal candidates for spintronic devices. These results may shed light on further experimental studies on molecular spintronics.

Ma, Yandong; Dai, Ying; Zhang, Zhenkui; Yu, Lin; Huang, Baibiao

2012-08-01

306

Interface conductivity contribution in Co-Phthalocyanines capacitive type devices  

NASA Astrophysics Data System (ADS)

Metal Phthalocyanines are flat organic semiconductors which exhibit interesting magnetotransport properties. Recent experimental studies in a particular system together with theoretical calculations have shown that the temperature and thickness dependence of the ohmic conductivity can be universally described by two independent contributions: the organic film and the electrode-film interface [1]. In order to explore the implications of this model we performed transport measurements in sandwich devices with different bottom electrodes materials. These devices are grown in-situ by Organic Molecular Beam Epitaxy to assure ultra clean electrode-film interfaces. A combination of structural and transport studies are used to investigate the reason for the drastic change in ohmic conductance at metallo-organic film thickness around 100nm. [4pt] [1] C. N. Colesniuc, R. R. Biswas, S. A. Hevia, A. V. Balatsky, and I. K. Schuller, Phys. Rev. B 83, 085414 (2011).

Monton, Carlos; Valmiansky, Ilya; Schuller, Ivan

2012-02-01

307

Molecular targeting of liposomal nanoparticles to tumor microenvironment  

PubMed Central

Liposomes are biodegradable and can be used to deliver drugs at a much higher concentration in tumor tissues than in normal tissues. Both passive and active drug delivery by liposomal nanoparticles can significantly reduce the toxic side effects of anticancer drugs and enhance the therapeutic efficacy of the drugs delivered. Active liposomal targeting to tumors is achieved by recognizing specific tumor receptors through tumor-specific ligands or antibodies coupled onto the surface of the liposomes, or by stimulus-sensitive drug carriers such as acid-triggered release or enzyme-triggered drug release. Tumors are often composed of tumor cells and nontumor cells, which include endothelial cells, pericytes, fibroblasts, stromal, mesenchymal cells, innate, and adaptive immune cells. These nontumor cells thus form the tumor microenvironment, which could be targeted and modified so that it is unfavorable for tumor cells to grow. In this review, we briefly summarized articles that had taken advantage of liposomal nanoparticles as a carrier to deliver anticancer drugs to the tumor microenvironment, and how they overcame obstacles such as nonspecific uptake, interaction with components in blood, and toxicity. Special attention is devoted to the liposomal targeting of anticancer drugs to the endothelium of tumor neovasculature, tumor associated macrophages, fibroblasts, and pericytes within the tumor microenvironment.

Zhao, Gang; Rodriguez, B Leticia

2013-01-01

308

Long-circulating, pH-sensitive liposomes.  

PubMed

A major limiting factor for the wide application of pH-sensitive liposomes is their recognition and sequestration by the phagocytes of the reticulo-endothelial system, which conditions a very short circulation half-life. Typically prolonged circulation of liposomes is achieved by grafting their membranes with pegylated phospholipids (PEG-lipids), which have been shown, however, to deteriorate membrane integrity on one hand and to hamper the pH-responsiveness on the other. Hence, the need for novel alternative surface modifying agents to ensure effective half-life prolongation of pH-sensitive liposomes is a subject of intensive research. A series of copolymers having short blocks of lipid-mimetic units has been shown to sterically stabilize conventional liposomes based on different phospholipids. This has prompted us to broaden their utilization to pH-sensitive liposomes, too. The present contribution gives thorough account on the chemical synthesis of these copolymers their incorporation in DOPE:CHEMs pH-sensitive liposomes and detailed explanation on the battery of techniques for the biopharmaceutical characterization of the prepared formulations in terms of pH-responsiveness, cellular internalization, in vivo pharmacokinetics and biodistribution. PMID:20072904

Momekova, Denitsa; Rangelov, Stanislav; Lambov, Nikolay

2010-01-01

309

The Antimicrobial Activity of Liposomal Lauric Acids Against Propionibacterium acnes  

PubMed Central

This study evaluated the antimicrobial activity of lauric acid (LA) and its liposomal derivatives against Propionibacterium acnes (P. acnes), the bacterium that promotes inflammatory acne. First, the antimicrobial study of three free fatty acids (lauric acid, palmitic acid and oleic acid) demonstrated that LA gives the strongest bactericidal activity against P. acnes. However, a setback of using LA as a potential treatment for inflammatory acne is its poor water solubility. Then the LA was incorporated into a liposome formulation to aid its delivery to P. acnes. It's demonstrated that the antimicrobial activity of LA was not only well maintained in its liposomal derivatives but also enhanced at low LA concentration. In addition, the antimicrobial activity of LA-loaded liposomes (LipoLA) mainly depended on the LA loading concentration per single liposomes. Further study found that the LipoLA could fuse with the membranes of P. acnes and release the carried LA directly into the bacterial membranes, thereby killing the bacteria effectively. Since LA is a natural compound that is the main acid in coconut oil and also resides in human breast milk and liposomes have been successfully and widely applied as a drug delivery vehicle in the clinic, the LipoLA developed in this work holds great potential of becoming an innate, safe and effective therapeutic medication for acne vulgaris and other P. acnes associated diseases.

Yang, Darren; Pornpattananangkul, Dissaya; Nakatsuji, Teruaki; Chan, Michael; Carson, Dennis; Huang, Chun-Ming; Zhang, Liangfang

2009-01-01

310

Pharmacokinetics and in vivo activity of liposome-encapsulated gentamicin.  

PubMed Central

Gentamicin sulfate was encapsulated in liposomes composed solely of egg phosphatidylcholine and administered via intravenous injection to rats and mice. The total gentamicin activity (regardless of whether it was free or liposome associated) in serum and selected tissues was determined for 24 h (serum) or up to 15 weeks (tissues) by using a microbiological assay. The mean half-lives in serum of a single 20-mg/kg dose of free (nonencapsulated) gentamicin in mice and rats were estimated to be 1.0 and 0.6 h, respectively, whereas a similar dose of encapsulated drug had apparent mean half-lives of 3.8 h in mice and 4.0 h in rats. In both species, the apparent half-life in serum of the liposomal formulation increased as the dose increased. Liposome encapsulation resulted in higher and more prolonged activity in organs rich in reticuloendothelial cells (especially spleen and liver). In acute septicemia infections in mice, the liposomal formulation showed enhanced prophylactic activity (as determined by calculation of the 50% protective dose). In a model of murine salmonellosis, liposomal gentamicin greatly enhanced survival when given as a single dose (10 mg/kg) at 1 or 2 days after infection as well as up to 7 days before infection.

Swenson, C E; Stewart, K A; Hammett, J L; Fitzsimmons, W E; Ginsberg, R S

1990-01-01

311

Liposome distribution after intravenous and selective intraarterial infusion in dogs  

SciTech Connect

In an effort to improve hepatic uptake of liposomes for drug delivery, empty vesicles were administered by means of selective arterial infusion. Negatively charged, multilamellar liposomes were labeled with technetium-99m and infused into healthy adult dogs. Each dog received 100 mg/m2 of lipid over 10 minutes at 2 mL/min. Liposomes were administered via the common hepatic artery after proximal occlusion of the gastroduodenal artery, via the cranial mesenteric artery, and via the cephalic vein. Distribution (liver, spleen, and lungs) was determined by computer-assisted external imaging techniques. On the average, after arterial infusion, 69.2% of the total activity was located in the liver, 3.6% in the spleen, 3.2% in the lungs, and 3.5% in the general circulation. Following venous injection, 50.7% of the radioactivity was found in the liver, 9.1% in the spleen, 8.6% in the lungs, and 6.7% in the peripheral blood. Once the liposomes entered the systemic circulation, they were cleared at the same rate (half-life beta = 21.5 hours) independent of their route of administration. Increased hepatic liposome uptake should translate into higher local and lower systemic liposomal drug levels.

Wright, K.C.; Kasi, L.P.; Jahns, M.S.; Hashimoto, S.; Wallace, S. (Univ. of Texas M.D. Anderson Cancer Center, Houston (USA))

1990-09-01

312

Modification of wool surface by liposomes for dyeing with weld.  

PubMed

In this research work, wool surface has been modified by liposome to investigate its effects on dyeing with weld, a yellow natural dye. To do this, samples were first treated with aluminium sulphate and afterward with different concentrations of liposomes at various temperatures for 30 minutes and, finally, dyed with weld at 75, 85, and 95 degrees C for 30, 45, and 60 minutes. K/S values of fabric samples were calculated and washing, light and rub fastness properties of the samples were indicated. The results proposed that the sample treated with 1% liposomes and dyed at 75 degrees C for 60 min has the highest K/S value. The central composite design (CCD) used for the experimental plan with three variables on the results of color strength and statistical analysis confirms the optimum conditions obtained by the experimental results. It was also found that washing, light, wet, and dry rub fastness properties of samples dyed with weld, including liposomes, have not significantly changed. The results of water drop absorption indicated that the hydrophobicity is higher for the samples pretreated with liposomes. The SEM picture of wool sample treated with mordant and liposomes and finally dyed with weld shows a coated layer on the fiber surface. PMID:19552578

Montazer, Majid; Zolfaghari, Alireza; Toliat, Taibeh; Moghadam, Mohammad Bameni

2009-01-01

313

Click modification of multifunctional liposomes bearing hyperbranched polyether chains.  

PubMed

Aiming at controlled modification of liposomal surface structures, we describe a postpreparational approach for surface derivatization of a new type of multifunctional, sterically stabilized liposomes. Application of dual centrifugation (DC) resulted in high encapsulation efficiencies above 50% at very small batch sizes with a total volume of 150 ?L, which were conductive to fast and efficient optimization of variegated surface modification reactions. Cholesterol-polymer amphiphiles, including complex hyperbranched polyether structures bearing 1-4 terminal alkynes, were used in DC formulations to provide steric stabilization. The alkyne moieties were explored as anchors for the conjugation of small molecules to the liposomal surface via click chemistry, binding 350-450 fluorophores per liposome as examples for surface active molecules. Using Förster resonance energy transfer (FRET) spectroscopy, the conjugation reaction as well as the uptake of FRET-labeled liposomes by RBE4 cells was monitored, and the distribution of the fluorescent lipids among cellular structures and membranes could be studied. Thus, the combination of clickable hyperbranched amphiphiles and dual centrifugation provides access to well-defined liposomal formulations with a variety of surface moieties. PMID:24805163

Fritz, Thomas; Hirsch, Markus; Richter, Felix C; Müller, Sophie S; Hofmann, Anna M; Rusitzka, Kristiane A K; Markl, Jürgen; Massing, Ulrich; Frey, Holger; Helm, Mark

2014-07-14

314

(18)F-labeled-bioorthogonal liposomes for in vivo targeting.  

PubMed

Liposomes are attractive vehicles for the controlled release of drugs and cytotoxins and have a long-standing history in medical research and clinical practice. In addition to established therapeutic indications, liposomes have several favorable properties for molecular imaging, including high stability and the ability to be labeled with radioisotopes, as well as paramagnetic and fluorescent contrast agents. However, long circulation times and difficulties in creating targeted liposomes have proven challenges for imaging. In this study, we have addressed these limitations using a recently developed strategy for bioorthogonal conjugation, the reaction between tetrazines and trans-cyclooctenes. By coating radiolabeled liposomes with trans-cyclooctene and pretargeting with a tetrazine coupled to a targeted peptide, we were able to selectively enhance the retention of liposomes and bind them to tumor tissue in live animals. The rapid reaction between tetrazines and trans-cyclooctenes allowed imaging to be performed with the short-lived PET tracer (18)F, yielding signal-to-background activity ratios of 7:1. The covalent, bioorthogonally driven tumor-targeting of liposomes by in vivo click chemistry is promising and should be explored for more selective and rapid delivery of radiodiagnostics and radiotherapeutics, two classes of drugs which particularly benefit from fast clearance, low nonspecific binding, and the associated reduced toxicity to kidneys and bone marrow. PMID:24180480

Emmetiere, Fabien; Irwin, Christopher; Viola-Villegas, Nerissa Therese; Longo, Valerie; Cheal, Sarah M; Zanzonico, Pat; Pillarsetty, Nagavarakishore; Weber, Wolfgang A; Lewis, Jason S; Reiner, Thomas

2013-11-20

315

Protrusive growth from giant liposomes driven by actin polymerization  

PubMed Central

Development of protrusions in the cell is indispensable in the process of cell motility. Membrane protrusion has long been suggested to occur as a result of actin polymerization immediately beneath the cell membrane at the leading edge, but elucidation of the mechanism is insufficient because of the complexity of the cell. To study the mechanism, we prepared giant liposomes containing monomeric actin (100 or 200 ?M) and introduced KCl into individual liposomes by an electroporation technique. On the electroporation, the giant liposomes deformed. Most importantly, protrusive structure grew from the liposomes containing 200 ?M actin at rates (ranging from 0.3 to 0.7 ?m/s) similar to those obtained in the cell. The deformation occurred in a time range (30 ? 100 s) similar to that of actin polymerization monitored in a cuvette (ca. 50 s). Concomitant with deformation, Brownian motion of micron-sized particles entrapped in the liposomes almost ceased. From these observations, we conclude that actin polymerization in the liposomes caused the protrusive formation.

Miyata, Hidetake; Nishiyama, Shuji; Akashi, Ken-ichirou; Kinosita, Kazuhiko

1999-01-01

316

Galactodendritic Phthalocyanine Targets Carbohydrate-Binding Proteins Enhancing Photodynamic Therapy  

PubMed Central

Photosensitizers (PSs) are of crucial importance in the effectiveness of photodynamic therapy (PDT) for cancer. Due to their high reactive oxygen species production and strong absorption in the wavelength range between 650 and 850 nm, where tissue light penetration is rather high, phthalocyanines (Pcs) have been studied as PSs of excellence. In this work, we report the evaluation of a phthalocyanine surrounded by a carbohydrate shell of sixteen galactose units distributed in a dendritic manner (PcGal16) as a new and efficient third generation PSs for PDT against two bladder cancer cell lines, HT-1376 and UM-UC-3. Here, we define the role of galacto-dendritic units in promoting the uptake of a Pc through interaction with GLUT1 and galectin-1. The photoactivation of PcGal16 induces cell death by generating oxidative stress. Although PDT with PcGal16 induces an increase on the activity of antioxidant enzymes immediately after PDT, bladder cancer cells are unable to recover from the PDT-induced damage effects for at least 72 h after treatment. PcGal16 co-localization with galectin-1 and GLUT1 and/or generation of oxidative stress after PcGal16 photoactivation induces changes in the levels of these proteins. Knockdown of galectin-1 and GLUT1, via small interfering RNA (siRNA), in bladder cancer cells decreases intracellular uptake and phototoxicity of PcGal16. The results reported herein show PcGal16 as a promising therapeutic agent for the treatment of bladder cancer, which is the fifth most common type of cancer with the highest rate of recurrence of any cancer.

Pereira, Patricia M. R.; Silva, Sandrina; Cavaleiro, Jose A. S.; Ribeiro, Carlos A. F.; Tome, Joao P. C.; Fernandes, Rosa

2014-01-01

317

The combined effect of encapsulating curcumin and C6 ceramide in liposomal nanoparticles against osteosarcoma.  

PubMed

This study examines the antitumor potential of curcumin and C6 ceramide (C6) against osteosarcoma (OS) cell lines when both are encapsulated in the bilayer of liposomal nanoparticles. Three liposomal formulations were prepared: curcumin liposomes, C6 liposomes and C6-curcumin liposomes. Curcumin in combination with C6 showed 1.5 times enhanced cytotoxic effect in the case of MG-63 and KHOS OS cell lines, in comparison with curcumin liposomes alone. Importantly, C6-curcumin liposomes were found to be less toxic on untransformed primary human cells (human mesenchymal stem cells) in comparison to OS cell lines. In addition, cell cycle assays on a KHOS cell line after treatment revealed that curcumin only liposomes induced G2/M arrest by upregulation of cyclin B1, while C6 only liposomes induced G1 arrest by downregulation of cyclin D1. C6-curcumin liposomes induced G2/M arrest and showed a combined effect in the expression levels of cyclin D1 and cyclin B1. The efficiency of the preparations was tested in vivo using a human osteosarcoma xenograft assay. Using pegylated liposomes to increase the plasma half-life and tagging with folate (FA) for targeted delivery in vivo, a significant reduction in tumor size was observed with C6-curcumin-FA liposomes. The encapsulation of two water insoluble drugs, curcumin and C6, in the lipid bilayer of liposomes enhances the cytotoxic effect and validates the potential of combined drug therapy. PMID:24380633

Dhule, Santosh S; Penfornis, Patrice; He, Jibao; Harris, Michael R; Terry, Treniece; John, Vijay; Pochampally, Radhika

2014-02-01

318

Antibody-Hapten Recognition at the Surface of Functionalized Liposomes Studied by SPR: Steric Hindrance of Pegylated Phospholipids in Stealth Liposomes Prepared for Targeted Radionuclide Delivery  

PubMed Central

Targeted PEGylated liposomes could increase the amount of drugs or radionuclides delivered to tumor cells. They show favorable stability and pharmacokinetics, but steric hindrance of the PEG chains can block the binding of the targeting moiety. Here, specific interactions between an antihapten antibody (clone 734, specific for the DTPA-indium complex) and DTPA-indium-tagged liposomes were characterized by surface plasmon resonance (SPR). Non-PEGylated liposomes fused on CM5 chips whereas PEGylated liposomes did not. By contrast, both PEGylated and non-PEGylated liposomes attached to L1 chips without fusion. SPR binding kinetics showed that, in the absence of PEG, the antibody binds the hapten at the surface of lipid bilayers with the affinity of the soluble hapten. The incorporation of PEGylated lipids hinders antibody binding to extents depending on PEGylated lipid fraction and PEG molecular weight. SPR on immobilized liposomes thus appears as a useful technique to optimize formulations of liposomes for targeted therapy.

Botosoa, Eliot. P.; Maillasson, Mike; Mougin-Degraef, Marie; Remaud-Le Saec, Patricia; Gestin, Jean-Francois; Jacques, Yannick; Barbet, Jacques; Faivre-Chauvet, Alain

2011-01-01

319

Silica-based monolithic capillary columns modified by liposomes for characterization of analyte-liposome interactions by capillary liquid chromatography.  

PubMed

This study introduces a silica-based monolith in a capillary format (0.1 mm × 100 mm) as a support for immobilization of liposomes and its characterization in immobilized liposome chromatography. Silica-based monolithic capillary columns prepared by acidic hydrolysis of tetramethoxysilane in the presence of polyethylene glycol and urea were modified by (3-aminopropyl)trimethoxysilane, whereby amino groups were introduced to the monolithic surface. These groups undergo reaction with glutaraldehyde to form an iminoaldehyde, allowing covalent binding of pre-formed liposomes containing primary amino groups. Two types of phospholipid vesicles were used for column modification; these were 2-oleoyl-1-palmitoyl-sn-glycero-3-phosphatidyl choline with and without 1,2-diacyl-sn-glycero-3-phospho-L-serine. The prepared columns were evaluated under isocratic separation conditions employing 20mM phosphate buffer at pH 7.4 as a mobile phase and a set of unrelated drugs as model analytes. The liposome layer on the synthesized columns significantly changed the column selectivity compared to the aminopropylsilylated monolithic stationary phase. Monolithic columns modified by liposomes were stable under the separation conditions, which proved the applicability of the suggested preparation procedure for the synthesis of capillary columns dedicated to study analyte-liposome interactions. The column efficiency originating from the silica monolith was preserved and reached, e.g., more than 120,000 theoretical plates/m for caffeine as a solute. PMID:23978749

Moravcová, Dana; Planeta, Josef; Wiedmer, Susanne K

2013-11-22

320

Dynamic and structural aspects of PEGylated liposomes monitored by NMR.  

PubMed

Proton-detected NMR diffusion and (31)P NMR chemical shifts/bandwidths measurements were used to investigate a series of liposomal formulations where size and PEGylation extent need to be controlled for ultrasound mediated drug release. The width of the (31)P line is sensitive to aggregate size and shape and self-diffusion (1)H NMR conveys information about diffusional motion, size, and PEGylation extent. Measurements were performed on the formulations at their original pH, osmolality, and lipid concentration. These contained variable amounts of PEGylated phospholipid (herein referred to as PEG-lipid) and cholesterol. At high levels of PEG-lipid (11.5 and 15 mol%) the self-diffusion (1)H NMR revealed the coexistence of two entities with distinct diffusion coefficients: micelles (1.3 to 3x10(-11) m(2)/s) and liposomes (approximately 5x10(-12) m(2)/s). The (31)P spectra showed a broad liposome signal and two distinct narrow lines that were unaffected by temperature. The narrow lines arise from mixed micelles comprising both PEG-lipids and phospholipids. The echo decay in the diffusion experiments could be described as a sum of exponentials revealing that the exchange of PEG-lipid between liposomes and micellar aggregates is slower than the experimental observation time. For low amounts of PEG-lipid (1 and 4.5 mol%) the (31)P spectra consisted of a broad signal typically obtained for liposomes and the diffusion data were best described by a single exponential decay attributed solely to liposomes. For intermediate amounts of PEG-lipid (8 mol%), micellization started to occur and the diffusion data could no longer be fitted to a single or bi-exponential decay. Instead, the data were best described by a log-normal distribution of diffusion coefficients. The most efficient PEG-lipid incorporation in liposomes (about 8 mol%) was achieved for lower molecular weight PEG (2000 Da vs 5000 Da) and when the PEG-lipid acyl chain length matched the acyl chain length of the liposomal core phospholipid. Simultaneously to the PEGylation extent, self-diffusion (1)H NMR provides information about the size of micelles and liposomes. The size of the micellar aggregates decreased as the PEG-lipid content was increased while the liposome size remained invariant. PMID:18589432

Leal, Cecília; Rögnvaldsson, Sibylla; Fossheim, Sigrid; Nilssen, Esben A; Topgaard, Daniel

2008-09-15

321

Observation of Outermost Surface Layers of Phthalocyanine Ultra-Thin Films by Penning Ionization Electron Spectroscopy: Chloroaluminium Phthalocyanine on MoS2  

Microsoft Academic Search

Using Penning ionization electron spectroscopy, which provides information on the local distribution of the individual orbitals exposed outside the outermost surface layer, ultra-thin films (1 to several monolayers) of chloroaluminium phthalocyanine were characterized during layer-by-layer vacuum deposition onto an MoS2 substrate and the change in the molecular orientation was sensitively detected.

Masaru Aoki; Shigeru Masuda; Yuichi Einaga; Koji Kamiya; Nobuo Ueno; Yoshiya Harada

1995-01-01

322

Study of the white-rot fungal degradation of selected phthalocyanine dyes by capillary electrophoresis and liquid chromatography  

Microsoft Academic Search

The phthalocyanine dyes, Remazol Turquoise Blue G133, Everzol Turquoise Blue and Heligon Blue S4 are found to be biosorbed by Phanerochaete chrysosporium (white-rot fungi) and also metabolised by its ligninolytic extracellular enzymes resulting in dye decolourisation, formation of free copper ions and organic metabolites with ultimate extensive phthalocyanine ring breakdown. It is believed that the ligninolytic extracellular enzyme laccase is

A. Conneely; W. F. Smyth; G. McMullan

2002-01-01

323

New synthetic amphiphilic polymers for steric protection of liposomes in vivo.  

PubMed

Carboxy group-terminated synthetic polymers--branched poly(ethylene glycol), poly(acryloylmorpholine), and poly(vinylpyrrolidone)--were made amphiphilic by derivatization with phosphatidyl ethanolamine via the terminal carboxy group and then incorporated into lecithin-cholesterol liposomes prepared by the detergent dialysis method. Following the biodistribution of liposomes in mice, all three polymers were shown to be effective steric protectors for liposomes and were able to sharply increase liposome circulation times in a concentration-dependent manner. The accumulation of liposomes in the liver decreases. The effects observed are similar to those found for liposomes modified with linear poly(ethylene glycol). At low polymer concentration, amphiphilic branched poly(ethylene glycol) seems to be the most effective liposome protector, most probably, because at the same molar content of anchoring groups, each attachment point carries two polymeric chains and doubles the quantity of liposome-grafted polymer comparing to linear poly(ethylene glycol). PMID:8537880

Torchilin, V P; Trubetskoy, V S; Whiteman, K R; Caliceti, P; Ferruti, P; Veronese, F M

1995-09-01

324

Inhibitory Effects of Gangliosides on Immune Reactions of Antibodies to Neutral Glycolipids in Liposomes.  

National Technical Information Service (NTIS)

Specific immune damage to liposomes containing forssman or globoside glycolipid was inhibited when the liposomes also contained ganglioside. The activity of a human monoclonal waldenstrom macroglobulin antibody to forssman glycolipid was inhibited by each...

S. Shichijo C. R. Alving

1986-01-01

325

Inhibition of cationic liposomes of (3H)thymidine incorporation into DNA of L1210 cells  

SciTech Connect

The in vitro cytotoxicity of cationic liposomes for L1210 cells was studied by measuring in two hours incubation their effect on (3H) thymidine incorporation into DNA. Liposomes prepared from the mixtures dipalmitoylphosphatidylcholine-cholesterol-stearylamine, egg yolk phosphatidyl-choline-cholesterol-stearylamine and egg yolk phosphatidyl-choline-stearylamine inhibit (3H) thymidine incorporation into L1210 cells DNA. The degree of inhibition increases with incubation time and the concentration of liposomes in the incubations. Liposomes of similar compositions, but without stearylamine (neutral liposomes), did not affect (3H) thymidine incorporation. On the other hand, fluorescence microscopy of cell incubated with liposomes containing 10 mM 6-carboxy fluorescein showed only cationic liposomes adsorbed on the surface of L1210 cells. It is concluded that the inhibition of (3H) thymidine incorporation due to cationic liposomes is partly related to their adsorption on the cell plasma membrane.

Laurent, G.; Laduron, C.; Ruysschaert, J.M.; Deleers, M.

1981-03-01

326

Clinical development of liposome-based drugs: formulation, characterization, and therapeutic efficacy.  

PubMed

Research on liposome formulations has progressed from that on conventional vesicles to new generation liposomes, such as cationic liposomes, temperature sensitive liposomes, and virosomes, by modulating the formulation techniques and lipid composition. Many research papers focus on the correlation of blood circulation time and drug accumulation in target tissues with physicochemical properties of liposomal formulations, including particle size, membrane lamellarity, surface charge, permeability, encapsulation volume, shelf time, and release rate. This review is mainly to compare the therapeutic effect of current clinically approved liposome-based drugs with free drugs, and to also determine the clinical effect via liposomal variations in lipid composition. Furthermore, the major preclinical and clinical data related to the principal liposomal formulations are also summarized. PMID:22275822

Chang, Hsin-I; Yeh, Ming-Kung

2012-01-01

327

Lipid Segregation in Membranes of Anionic Liposomes Adsorbed onto Polycationic Brushes.  

PubMed

Two-phased: Complexation of liposomes to spherical polycationic brushes induces lipid segregation in the liposomal membrane. The greater the initial anionic lipid content in the membrane, the more the electroneutral lipid dilutes the induced anionic clusters. PMID:24092540

Yaroslavov, Alexander A; Sybachin, Andrey V; Zaborova, Olga V; Orlov, Viktor N; Ballauff, Matthias; Talmon, Yeshayahu; Menger, Fredric M

2013-10-01

328

Clinical development of liposome-based drugs: formulation, characterization, and therapeutic efficacy  

PubMed Central

Research on liposome formulations has progressed from that on conventional vesicles to new generation liposomes, such as cationic liposomes, temperature sensitive liposomes, and virosomes, by modulating the formulation techniques and lipid composition. Many research papers focus on the correlation of blood circulation time and drug accumulation in target tissues with physicochemical properties of liposomal formulations, including particle size, membrane lamellarity, surface charge, permeability, encapsulation volume, shelf time, and release rate. This review is mainly to compare the therapeutic effect of current clinically approved liposome-based drugs with free drugs, and to also determine the clinical effect via liposomal variations in lipid composition. Furthermore, the major preclinical and clinical data related to the principal liposomal formulations are also summarized.

Chang, Hsin-I; Yeh, Ming-Kung

2012-01-01

329

Preparation of liposomes containing Ceramide 3 and their membrane characteristics.  

PubMed

Liposomes composed of Ceramide 3, [2S,3S,4R-2-stearoylamide-1,3,4-octadecanetriol], and L-alpha-dipalmitoylphosphatidylcholine (DPPC) were prepared by varying the amount of Ceramide 3, and the effects of Ceramide 3 on the liposome formation, particle size, dispersibility, microviscosity and phase transition temperature were examined by means of a microscopy, a dynamic light scattering method, a fluorescence polarization method, a differential scanning calorimetry (DSC) and so on. All the DPPC was able to contribute to the formation of liposomes up to 0.130 mol fraction of Ceramide 3. The particle size of liposomes was almost unaffected by the addition of Ceramide 3. The dispersibility of liposomes containing Ceramide 3 was maintained for at least 15 days. The microviscosity of liposomal bilayer membranes in the liquid crystalline state was increased with increasing the mole fraction of Ceramide 3, while that in the gel state was independent of the mole fraction of Ceramide 3. The phase transition temperature from gel to liquid crystalline states of DPPC bilayer membranes was shifted upwards with the addition of Ceramide 3, indicating a cooperative interaction between DPPC and Ceramide 3 molecules. However, a sharp DSC peak became broad and split at higher mole fractions of Ceramide 3, suggesting a phase separation in the mixed DPPC/Ceramide 3 liposomal bilayer membranes. These phenomena were suggested to be related to the previously observed fact for the mixed DPPC/Ceramide 3 monolayers that Ceramide 3 interacts with DPPC in the liquid-expanded phase with consequent phase separation accompanied with domain formation. PMID:11084304

Imura; Sakai; Yamauchi; Kaise; Kozawa; Yokoyama; Abe

2001-01-15

330

Liposomal diltiazem HCl as ocular drug delivery system for glaucoma.  

PubMed

Abstract In this study, unilamellar liposomal vesicles of diltiazem HCl (DH) were prepared using either reversed phase evaporation (REV) or proliposome methods. Soya phosphatidylcholine (SPC) was used for preparing the liposomes, and the vesicles were rigidified using cholesterol (Chol) or cetyl alcohol (CA) in different molarities. The major differences in both the entrapment efficiency percent (EE%) and drug release were evaluated as a function of the method of preparation, Chol or CA contents, and charging lipids. Moreover, the morphology of the vesicles was confirmed by transmission electron microscopy. The effects of Chol or CA incorporation into the liposomes were discussed based on thermal analysis. The in vivo evaluation of liposomal DH was assessed using intra-ocular pressure (IOP), reducing effects in rabbit eyes. Liposomes prepared via REV exhibited higher EE% and lower release rates when compared with those prepared from proliposomes. The incorporation of either Chol or CA in the liposomes enhanced the EE% and decreased the release rates; however, Chol yielded higher results than CA. In addition, both dicetyl phosphate (DCP; negative charge inducer) and stearyl amine (SA, positive charge inducer) decreased the EE% and increased the DH release rate. The in vivo antiglaucoma effects of the liposomes were calculated according to the area above the IOP/Time curve, the maximum response and the time for the maximum response and were compared with effects of the DH solution. The results were in the following order: DH solution?

Mokhtar Ibrahim, Mahmoud; Tawfique, Salma A H; Mahdy, Mahmoud M

2014-06-01

331

Evaluation of circulation profiles of liposomes coated with hydrophilic polymers having different molecular weights in rats  

Microsoft Academic Search

The purpose of this study was to evaluate the circulating properties of liposomes coated with modified polyvinyl alcohol (PVA-R) having different molecular weights (6000, 9000 and 20?000). The size controlled liposomes (egg phosphatidylcholine (or distearoylphosphatidylcholine):cholesterol=7:3 in a molar ratio) were prepared by the hydration method followed by sonication. Polymer coated liposomes were prepared by just mixing the resultant liposomal suspension

Hirofumi Takeuchi; Hiroyuki Kojima; Hiromitsu Yamamoto; Yoshiaki Kawashima

2001-01-01

332

Spleen plays an important role in the induction of accelerated blood clearance of PEGylated liposomes  

Microsoft Academic Search

It is well known that steric stabilization of the surface of liposomes by a polyethyleneglycol (PEG) conjugated lipid results in reduced recognition of the liposomes by the cells of the mononuclear phagocyte system and consequently extended circulation times of the liposomes (t1\\/2?20 h in rat). Recently, we reported on the “accelerated blood clearance (ABC) phenomenon”, causing PEGylated liposomes to be cleared

Tatsuhiro Ishida; Masako Ichihara; XinYu Wang; Hiroshi Kiwada

2006-01-01

333

Liposome-encapsulated actin–hemoglobin (LEAcHb) artificial blood substitutes  

Microsoft Academic Search

A new approach to enhance the circulation persistence of liposomes has been applied to develop liposome-encapsulated actin–hemoglobin (LEAcHb) dispersions as potential blood substitutes by introducing an actin matrix into the liposome aqueous core. Asymmetric flow field-flow fractionation coupled with multi-angle static light scattering was used to study the shape, size distribution, and encapsulation efficiency of liposome-encapsulated hemoglobin (LEHb) and LEAcHb

Shuliang Li; Jonathan Nickels; Andre Francis Palmer

2005-01-01

334

Membrane-Targeted Nanotherapy with Hybrid Liposomes for Tumor Cells Leading to Apoptosis  

PubMed Central

Hybrid liposomes are nanosized liposomal particles and can be prepared by sonication of vesicular and micellar molecules in a buffer solution. In this study, we obtained the first successful experiment resulting in a good correlation between inhibitory effects of hybrid liposomes on the growth of various tumor cells and the membrane fluidity of tumor cells (plasma membranes). The results indicated that hybrid liposomes could provide the possibility of novel membrane-targeted nanotherapy for intractable cancers.

2011-01-01

335

Multi-polar resistance switching and memory effect in copper phthalocyanine junctions  

NASA Astrophysics Data System (ADS)

Copper phthalocyanine junctions, fabricated by magnetron sputtering and evaporating methods, show multi-polar (unipolar and bipolar) resistance switching and the memory effect. The multi-polar resistance switching has not been observed simultaneously in one organic material before. With both electrodes being cobalt, the unipolar resistance switching is universal. The high resistance state is switched to the low resistance state when the bias reaches the set voltage. Generally, the set voltage increases with the thickness of copper phthalocyanine and decreases with increasing dwell time of bias. Moreover, the low resistance state could be switched to the high resistance state by absorbing the phonon energy. The stability of the low resistance state could be tuned by different electrodes. In Au/copper phthalocyanine/Co system, the low resistance state is far more stable, and the bipolar resistance switching is found. Temperature dependence of electrical transport measurements demonstrates that there are no obvious differences in the electrical transport mechanism before and after the resistance switching. They fit quite well with Mott variable range hopping theory. The effect of Al2O3 on the resistance switching is excluded by control experiments. The holes trapping and detrapping in copper phthalocyanine layer are responsible for the resistance switching, and the interfacial effect between electrodes and copper phthalocyanine layer affects the memory effect.

Qiao, Shi-Zhu; Kang, Shi-Shou; Qin, Yu-Feng; Li, Qiang; Zhong, Hai; Kang, Yun; Yu, Shu-Yun; Han, Guang-Bing; Yan, Shi-Shen; Mei, Liang-Mo

2014-05-01

336

Electronic Structure of C60/Phthalocyanine/ITO Interfaces Studied using Soft X-ray Spectroscopies  

SciTech Connect

The interface electronic structure of a bilayer heterojunction of C{sub 60} and three different phthalocyanines grown on indium tin oxide (ITO) has been studied using synchrotron radiation-excited photoelectron spectroscopy. The energy difference between the highest occupied molecular orbital level of the phthalocyanine (donor) layer and the lowest unoccupied molecular orbital level of the C{sub 60} (acceptor) layer (E{sub HOMO}{sup D} - E{sub LUMO}{sup A}) was determined. The E{sub HOMO}{sup D} - E{sub LUMO}{sup A} of a heterojunction with boron subphthalocyanine chloride (SubPc) was found to be much larger than those of copper phthalocyanine (CuPc) and chloro-aluminum phthalocyanine (ClAlPc). This observation is discussed in terms of the difference of the ionization energy of each donor material. Additionally, we have studied the molecular orientation of the phthalocyanine films on ITO using angle-dependent X-ray absorption spectroscopy. We found that the SubPc films showed significant disorder compared to the CuPc and ClAlPc films and also found that E{sub HOMO}{sup D} - E{sub LUMO}{sup A} varied with the orientation of the ClAlPc molecules relative to the ITO substrate. This orientation could be controlled by varying the ClAlPc deposition rate.

Cho, S.; Piper, L; DeMasi, A; Preston, A; Smith, K; Chauhan, K; Sullivan, P; Hatton, R; Jones, T

2010-01-01

337

Elaboration of ammonia gas sensors based on electrodeposited polypyrrole--cobalt phthalocyanine hybrid films.  

PubMed

The electrochemical incorporation of a sulfonated cobalt phthalocyanine (sCoPc) in conducting polypyrrole (PPy) was done, in the presence or absence of LiClO4, in order to use the resulting hybrid material for the sensing of ammonia. After electrochemical deposition, the morphological features and structural properties of polypyrrole/phthalocyanine hybrid films were investigated and compared to those of polypyrrole films. A gas sensor consisting in platinum microelectrodes arrays was fabricated using silicon microtechnologies, and the polypyrrole and polypyrrole/phthalocyanine films were electrochemically deposited on the platinum microelectrodes arrays of this gas sensor. When exposed to ammonia, polymer-based gas sensors exhibited a decrease in conductance due to the electron exchange between ammonia and sensitive polymer-based layer. The characteristics of the gas sensors (response time, response amplitude, reversibility) were studied for ammonia concentrations varying from 1 ppm to 100 ppm. Polypyrrole/phthalocyanine films exhibited a high sensitivity and low detection limit to ammonia as well as a fast and reproducible response at room temperature. The response to ammonia exposition of polypyrrole films was found to be strongly enhanced thanks to the incorporation of the phthalocyanine in the polypyrrole matrix. PMID:24209308

Patois, Tilia; Sanchez, Jean-Baptiste; Berger, Franck; Fievet, Patrick; Segut, Olivier; Moutarlier, Virginie; Bouvet, Marcel; Lakard, Boris

2013-12-15

338

Formation of bovine serum albumin associates with zinc tetra(4,4'-carboxy)phenylamino- and tetra-(4,4'-carboxy)phenoxy phthalocyanines in aqueous-organic solutions at 298 K  

NASA Astrophysics Data System (ADS)

The states of water-soluble complexes of zinc phthalocyanine containing -O-C6H4-COONa and -NH-C6H4-COONa substituents in aqueous and organic media are studied. The type of dimerization is determined for each phthalocyanine. Phthalocyanine interaction with bovine serum albumin is studied with respect to the association equilibria. It is shown that phthalocyanines are localized in protein subdomains IB and IIA, and the interaction between protein and phthalocyanines is of a multicenter character.

Lebedeva, N. Sh.; Popova, T. E.; Mal'kova, E. A.; Gubarev, Yu. A.

2013-12-01

339

Effect of zeta potential of cationic liposomes containing cationic cholesterol derivatives on gene transfection  

Microsoft Academic Search

Cationic liposomes are known to be useful tools for gene transfection. However, the relation between transfection efficiency and physicochemical properties of liposomes has not been well understood. Here, we synthesized eight cationic derivatives of cholesterol which contain a tertiary amino head group with a different spacer arm. Transfection of plasmid pSV2CAT DNA into cells was done by cationic liposomes made

Ken-ichiro Takeuchi; Minoru Ishihara; Chiyo Kawaura; Masahide Noji; Tadahide Furuno; Mamoru Nakanishi

1996-01-01

340

Curcumin-loaded ?-cyclodextrin liposomal nanoparticles as delivery vehicles for osteosarcoma  

Microsoft Academic Search

The delivery of curcumin, a broad-spectrum anticancer drug, has been explored in the form of liposomal nanoparticles to treat osteosarcoma (OS). Curcumin is water insoluble and an effective delivery route is through encapsulation in cyclodextrins followed by a second encapsulation in liposomes. Liposomal curcumin's potential was evaluated against cancer models of mesenchymal (OS) and epithelial origin (breast cancer). The resulting

Santosh S. Dhule; Patrice Penfornis; Trivia Frazier; Ryan Walker; Joshua Feldman; Grace Tan; Jibao He; Alina Alb; Vijay John; Radhika Pochampally

341

Liposomal Vaccines. Clinical Status and Immunological Presentation for Humoral and Cellular Immunity.  

National Technical Information Service (NTIS)

Liposomes have been extensively tested and found to be relatively safe as drug carriers for a variety of clinical applications. In contrast to the use of liposomes as drug carriers, in which it is often proposed that large quantities of liposomes should b...

C. R. Alving

1995-01-01

342

In vivo targeting of acoustically reflective liposomes for intravascular and transvascular ultrasonic enhancement  

Microsoft Academic Search

OBJECTIVESThe purpose of this study was to target acoustically reflective liposomes to atherosclerotic plaques in vivo for ultrasound image enhancement.BACKGROUNDWe have previously demonstrated the development of acoustically reflective liposomes that can be conjugated for site-specific acoustic enhancement. This study evaluates the ability of liposomes coupled to antibodies specific for different components of atherosclerotic plaques and thrombi to target and enhance

Sasha M. Demos; Hayat Alkan-Onyuksel; Bonnie J. Kane; Kishin Ramani; Ashwin Nagaraj; Rodney Greene; Melvin Klegerman; David D. McPherson

1999-01-01

343

Investigations of a new, highly negative liposome with improved biodistribution for imaging  

SciTech Connect

An attractive feature of liposomes is the wide range of lipid composition that can lead to liposome formation, coupled with the observation that liposome biodistribution may be altered by varying lipid composition. For instance, adding charged lipids to neutral lecithin will alter the biodistribution of the resulting charged liposomes. We have prepared highly negative liposomes by replacing lecithin with negatively charged cardiolipin. The liposomes have been labeled in the lipid phase with Ga-67 and Tc-99m oxine and their properties evaluated. The expected high negative charge of the resulting liposomes was confirmed by an ion-exchange chromatographic technique. Using paper chromatography, the stability of the label was determined during incubation in saline and serum. Finally, biodistributions were determined at 2 h in mice, and the results compared with those for negative lecithin liposomes. Accumulated activities in liver and spleen were reduced by factors of five and 20, respectively, over lecithin liposomes. Since preferential accumulation of activity in these organs constitutes the biggest limitation to the use of lecithin liposomes, cardiolipin liposomes may prove to be more useful carriers of radioactivity in imaging applications. More importantly, however, these results illustrate the value of studying novel liposome types as potential radiopharmaceuticals.

Hnatowich, D.J.; Clancy, B.

1980-07-01

344

Nebulization of ultradeformable liposomes: the influence of aerosolization mechanism and formulation excipients.  

PubMed

Ultradeformable liposomes are stress-responsive phospholipid vesicles that have been investigated extensively in transdermal delivery. In this study, the suitability of ultradeformable liposomes for pulmonary delivery was investigated. Aerosols of ultradeformable liposomes were generated using air-jet, ultrasonic or vibrating-mesh nebulizers and their stability during aerosol generation was evaluated using salbutamol sulphate as a model hydrophilic drug. Although delivery of ultradeformable liposome aerosols in high fine particle fraction was achievable, the vesicles were very unstable to nebulization so that up to 98% drug losses were demonstrated. Conventional liposomes were relatively less unstable to nebulization. Moreover, ultradeformable liposomes tended to aggregate during nebulization whilst conventional vesicles demonstrated a "size fractionation" behaviour, with smaller liposomes delivered to the lower stage of the impinger and larger vesicles to the upper stage. A release study conducted for 2 h showed that ultradeformable liposomes retained only 30% of the originally entrapped drug, which was increased to 53% by inclusion of cholesterol within the formulations. By contrast, conventional liposomes retained 60-70% of the originally entrapped drug. The differences between ultradeformable liposomes and liposomes were attributed to the presence of ethanol or Tween 80 within the elastic vesicle formulations. Overall, this study demonstrated, contrary to our expectation, that materials included with the aim of making the liposomes more elastic and ultradeformable to enhance delivery from nebulizers were in fact responsible for vesicle instability during nebulization and high leakage rates of the drug. PMID:22796173

Elhissi, Abdelbary M A; Giebultowicz, Joanna; Stec, Anna A; Wroczynski, Piotr; Ahmed, Waqar; Alhnan, Mohamed Albed; Phoenix, David; Taylor, Kevin M G

2012-10-15

345

A liposome-based energy conversion system for accelerating the multi-enzyme reactions.  

PubMed

We report the first example of a liposome-based energy conversion system that is useful for entrapping enzymes and NAD coenzyme to accelerate multi-step enzymatic reactions. The liposome generates a much higher catalytic current compared with the non-liposome system, which is in good consistency with numerical simulations. PMID:20848047

Matsumoto, Ryuhei; Kakuta, Masaya; Sugiyama, Taiki; Goto, Yoshio; Sakai, Hideki; Tokita, Yuichi; Hatazawa, Tsuyonobu; Tsujimura, Seiya; Shirai, Osamu; Kano, Kenji

2010-11-14

346

Targeting of lysosomes by liposomes modified with octadecyl-rhodamine B  

PubMed Central

The use of lysosome-targeted liposomes may significantly improve a delivery of therapeutic enzymes into lysosomes for the treatment of lysosome-associated diseases. The aim of this research was to achieve a specific intracellular targeting of lysosomes, by using liposomes modified with the lysosomotropic octadecyl-rhodamine B (RhB) and loaded with a model compound, fluorescein isothiocyanate (FITC)–dextran (FD). Plain and RhB-modified liposomes were prepared by hydration of lipid films and loaded with FD or with 5-dodecanoylaminofluorescein di-?-D-galactopyranoside (C12FDG), a specific substrate for the intralysosomal ?-galactosidase. The delivery of these liposomes and their content to lysosomes in HeLa cells was investigated by confocal microscopy, flow cytometry, and subcellular fractionation. Confocal microscopy demonstrated that RhB-liposomes co-localize well with the specific lysosomal markers, unlike plain liposomes. The comparison of the FITC fluorescence of the lysosomes isolated by subcellular fractionation also showed that the efficiency of FD delivery into lysosomes by RhB-modified liposomes was significantly higher compared with plain liposomes. These results were additionally confirmed by the flow cytometry of the intact cells treated with C12FDG-loaded liposomes that also demonstrated increased lysosomal targeting by RhB-modified liposomes. The modification of the liposomal surface with a lysosomotropic ligand, such as octadecyl-RhB, can significantly increase the delivery of liposomal loads to lysosomes.

Koshkaryev, Alexander; Thekkedath, Ritesh; Pagano, Cinzia; Meerovich, Igor; Torchilin, Vladimir P.

2014-01-01

347

Light- and temperature-responsive liposomes incorporating cinnamoyl Pluronic F127.  

PubMed

Light- and temperature-responsive liposomes were prepared by immobilizing cinnamoyl Pluronic F127 (CP F127) on the surface of egg phosphatidylcholine liposomes. CP F127 was prepared by a condensation reaction, and the molar ratio of cinnamoyl group to Pluronic F127 was calculated to be 1:1.4 on (1)H NMR spectrum. The cinnamoyl group of CP F127 was readily dimerized under the irradiation of a UV light (254nm, 6W). CP F127 decreased the absolute value of the zeta potential of liposome possibly because it can shift the hydrodynamic plane away from the liposome surface. The size of liposome decorated with CP F127, measured on a dynamic light scattering machine and observed on a TEM, was larger than that of bare liposome. The liposome bearing CP F127 seemed to fuse and aggregate each other. The liposome released calcein, a fluorescence dye, in response to a UV irradiation, possibly because the photo-dimerization of cinnamoyl group perturbs the liposomal membrane. Moreover, the liposome released the dye in response to a temperature change, possible due to the phase transition of Pluronic F127 layer on the liposomal surface or the hydrophobic interaction of the polymer with liposomal membrane. PMID:24709213

Wang, MinHui; Kim, Jin-Chul

2014-07-01

348

Effect of formulation design and freeze-drying on properties of fluconazole multilamellar liposomes  

PubMed Central

Fluconazole-entrapped multilamellar liposomes were prepared using the thin-film hydration method. The effects of cholesterol molar ratio, charge-inducing agents, and ?-tocopherol acetate on encapsulation efficiency values and in vitro drug release of multilamellar liposomes were studied. Freeze-dried liposomal products were prepared with or without cryoprotectants. Results showed that incorporation of stearylamine resulted in an increased entrapment of fluconazole, whereas incorporation of dicetyl phosphate decreased the drug entrapment efficiency. The incorporation of ?-tocopherol acetate into fluconazole multilamellar liposomes resulted in the increase of entrapment efficiency of fluconazole liposomes. In vitro release studies revealed that incorporation of cholesterol into multilamellar liposomal formulations decreased drug permeability from formulations. Positively charged fluconazole multilamellar liposomes gave rise to a slow release rate compared to neutral liposomes whereas negatively charged fluconazole liposomes showed a rapid release rate. Physical stability studies showed that lyophilized cake of liposomes without cryoprotectants was compact and difficult to reconstitute compared to fluffy easily reconstituted cakes upon using cryoprotectants. Fluconazole retained in freeze-dried liposomes without cryoprotectants was 63.452% compared to 91.877% using three grams of trehalose as a cryoprotectant per gram lipid in positively charged multilamellar liposomes. Physical stability studies showed superior potentials of the lyophilized product after reconstitution in comparison with those of a solution product.

El-Nesr, Ola H.; Yahiya, Soad A.; El-Gazayerly, Omaima N.

2010-01-01

349

Paramagnetic liposomes for molecular MRI and MRI-guided drug delivery.  

PubMed

Liposomes are a versatile class of nanoparticles with tunable properties, and multiple liposomal drug formulations have been clinically approved for cancer treatment. In recent years, an extensive library of gadolinium (Gd)-containing liposomal MRI contrast agents has been developed for molecular and cellular imaging of disease-specific markers and for image-guided drug delivery. This review discusses the advances in the development and novel applications of paramagnetic liposomes in molecular and cellular imaging, and in image-guided drug delivery. A high targeting specificity has been achieved in vitro using ligand-conjugated paramagnetic liposomes. On targeting of internalizing cell receptors, the effective longitudinal relaxivity r1 of paramagnetic liposomes is modulated by compartmentalization effects. This provides unique opportunities to monitor the biological fate of liposomes. In vivo contrast-enhanced MRI studies with nontargeted liposomes have shown the extravasation of liposomes in diseases associated with endothelial dysfunction, such as tumors and myocardial infarction. The in vivo use of targeted paramagnetic liposomes has facilitated the specific imaging of pathophysiological processes, such as angiogenesis and inflammation. Paramagnetic liposomes loaded with drugs have been utilized for therapeutic interventions. MR image-guided drug delivery using such liposomes allows the visualization and quantification of local drug delivery. PMID:23703874

Langereis, Sander; Geelen, Tessa; Grüll, Holger; Strijkers, Gustav J; Nicolay, Klaas

2013-07-01

350

Enhanced localization of anticancer drug in tumor tissue using polyethylenimine-conjugated cationic liposomes  

PubMed Central

Liposome-based drug delivery systems hold great potential for cancer therapy. However, to enhance the localization of payloads, an efficient method of systemic delivery of liposomes to tumor tissues is required. In this study, we developed cationic liposomes composed of polyethylenimine (PEI)-conjugated distearoylglycerophosphoethanolamine (DSPE) as an enhanced local drug delivery system. The particle size of DSPE-PEI liposomes was 130?±?10 nm and the zeta potential of liposomes was increased from -25 to 30 mV by the incorporation of cationic PEI onto the liposomal membrane. Intracellular uptake of DSPE-PEI liposomes by tumor cells was 14-fold higher than that of DSPE liposomes. After intratumoral injection of liposomes into tumor-bearing mice, DSPE-PEI liposomes showed higher and sustained localization in tumor tissue compared to DSPE liposomes. Taken together, our findings suggest that DSPE-PEI liposomes have the potential to be used as effective drug carriers for enhanced intracellular uptake and localization of anticancer drugs in tumor tissue through intratumoral injection.

2014-01-01

351

Enhanced localization of anticancer drug in tumor tissue using polyethylenimine-conjugated cationic liposomes  

NASA Astrophysics Data System (ADS)

Liposome-based drug delivery systems hold great potential for cancer therapy. However, to enhance the localization of payloads, an efficient method of systemic delivery of liposomes to tumor tissues is required. In this study, we developed cationic liposomes composed of polyethylenimine (PEI)-conjugated distearoylglycerophosphoethanolamine (DSPE) as an enhanced local drug delivery system. The particle size of DSPE-PEI liposomes was 130 ± 10 nm and the zeta potential of liposomes was increased from -25 to 30 mV by the incorporation of cationic PEI onto the liposomal membrane. Intracellular uptake of DSPE-PEI liposomes by tumor cells was 14-fold higher than that of DSPE liposomes. After intratumoral injection of liposomes into tumor-bearing mice, DSPE-PEI liposomes showed higher and sustained localization in tumor tissue compared to DSPE liposomes. Taken together, our findings suggest that DSPE-PEI liposomes have the potential to be used as effective drug carriers for enhanced intracellular uptake and localization of anticancer drugs in tumor tissue through intratumoral injection.

Han, Hee Dong; Byeon, Yeongseon; Jeon, Hat Nim; Shin, Byung Cheol

2014-05-01

352

Liposomal incorporation of Artemisia arborescens L. essential oil and in vitro antiviral activity  

Microsoft Academic Search

The effect of liposomal inclusion on the in vitro antiherpetic activity of Artemisia arborescens L. essential oil was investigated. In order to study the influence of vesicle structure and composition on the antiviral activity of the vesicle-incorporated oil, multilamellar (MLV) and unilamellar (SUV) positively charged liposomes were prepared by the film method and sonication. Liposomes were obtained from hydrogenated (P90H)

Chiara Sinico; Alessandro De Logu; Francesco Lai; Donatella Valenti; Maria Manconi; Giuseppe Loy; Leonardo Bonsignore; Anna Maria Fadda

2005-01-01

353

Synthesis of phthalocyanine doped sol-gel materials  

NASA Technical Reports Server (NTRS)

The synthesis of sol-gel silica materials doped with three different types of metallophthalocyanines has been studied. Homogeneous materials of good optical quality were prepared and the first optical limiting measurements of dyes in sol-gel hosts were carried out. The properties of these solid state limiters are similar to limiters based on phthalocyanine (Pc) in solution. Sol-gel silica materials containing copper, tin and germanium phthalocyanines were investigated. The initial step in all cases was to prepare silica sols by the sonogel method using tetramethoxy silane (TMOS), HCl and distilled water. Thereafter, the synthesis depended upon the specific Pc and its solubility characteristics. Copper phthalocyanine tetrasulfonic acid tetra sodium salt (CuPc4S) is soluble in water and various doping levels (1 x 10 (exp -4) M to 1 x 10 (exp -5) M) were added to the sol. The group IV Pc's, SnPc(OSi(n-hexyl)3)2 and GePc(OSi(n-hexyl)3)2, are insoluble in water and the process was changed accordingly. In these cases, the compounds were dissolved in THF and then added to the sol. The Pc concentration in the sol was 2 x 10(exp -5)M. The samples were then aged and dried in the standard method of making xerogel monoliths. Comparative nanosecond optical limiting experiments were performed on silica xerogels that were doped with the different metallophthalocyanines. The ratio of the net excited state absorption cross section (sigma(sub e)) to the ground state cross section (sigma(sub g)) is an important figure of merit that is used to characterize these materials. By this standard the SnPc sample exhibits the best limiting for the Pc doped sol-gel materials. Its cross section ratio of 19 compares favorably with the value of 22 that was measured in toluene. The GePc materials appear to not be as useful as those containing SnPc. The GePc doped solids exhibit a higher onset energy (2.5 mj and lower cross section ratio, 7. The CuPc4S sol-gel material has a still lower cross section ratio, 4, however, the tetrasulfonate groups make the dye soluble in water which greatly facilitates its incorporation into the sol-gel matrix. The nonlinear transmission of CuPc4S in a pH 2 buffer solution and in a silica xerogel were compared. It is evident that the CuPc4S preserves its optical limiting behavior in the sol-gel matrix, indicating that the fundamental excited state absorption process is essentially the same for a molecule in solution or in the solid state. Although the spectroscopic details of energy level lifetimes are unknown, the significance is that passive optical limiting has been achieved in the solid state via incorporation of a dye into an inorganic host. The only compromise occurs at the extremely high energy regime where photobleaching is observed. This is a result of the limited mobility of the dye molecules in the solid silica host relative to a liquid host. The effects of photodegradation in the xerogel are additive, whereas the solution provides a supply of fresh molecules that are free to enter the active volume between pulses.

Dunn, Bruce

1993-01-01

354

Pharmacokinetics of poly(hydroxyethyl-l-asparagine)-coated liposomes is superior over that of PEG-coated liposomes at low lipid dose and upon repeated administration.  

PubMed

'Stealth' liposomes with a poly(ethylene glycol) (PEG) coating are frequently studied for drug delivery and diagnostic purposes because of their prolonged blood circulation kinetics. However, several recent reports have demonstrated that PEG-liposomes are rapidly cleared at single low lipid doses (<1 micromol/kg) and upon repeated administration (time interval between the injections 5 days-4 weeks). Recently, poly(amino acid)-based stealth liposome coatings have been developed as alternative to the PEG-coating. In this study, the pharmacokinetic behavior of liposomes coated with the poly(amino acid) poly(hydroxyethyl-l-asparagine) (PHEA) was evaluated at low lipid doses and upon repeated administration in rats. Blood circulation times and hepatosplenic localization of PHEA-liposomes were assessed after intravenous injection. When administered at a dose of 0.25 micromol/kg or less, PHEA-liposomes showed significantly longer blood circulation times than PEG-liposomes. A second dose of PHEA-liposomes 1 week after the first injection was less rapidly cleared from the circulation than a second dose of PEG-liposomes. Although the mechanisms behind these observations are still not clear yet, the use of PHEA-liposomes appears beneficial when single low lipid doses and/or repeated dosing schedules are being applied. PMID:17223070

Romberg, Birgit; Oussoren, Christien; Snel, Cor J; Carstens, Myrra G; Hennink, Wim E; Storm, Gert

2007-03-01

355

Inhibition of lymphokine-induced macrophage microbicidal activity against Leishmania major by liposomes: characterization of the physicochemical requirements for liposome inhibition.  

PubMed

Resident peritoneal macrophages from untreated mice develop potent microbicidal activity against amastigotes of Leishmania major after in vitro treatment with lymphokine (LK) from mitogen-stimulated spleen cells. LK-induced macrophage microbicidal activity was completely and selectively abrogated by treatment with phosphatidylcholine-phosphatidylserine (PC/PS) liposomes. Other macrophage effector functions (phagocytosis, tumoricidal activity) were unaffected, as was cytotoxicity by macrophages activated in vivo or by LK in vitro before liposome treatment. Activation factors in LK were not adsorbed or destroyed by liposomes. Liposome-induced inhibition was unaffected by indomethacin and was fully reversible: macrophages washed free of liposomes developed strong microbicidal activity with subsequent LK treatment. Changes in liposomal lipid composition markedly altered suppressive effects, but inhibition was not dependent on liposome size, cholesterol content, charge, or number of lamellae. Liposomes composed of PC alone or in combination with any of five different phospholipids were not suppressive. In contrast, inhibition was directly dependent on PS concentration within PC/PS liposomes. Phosphoserine was not inhibitory nor was dimyristoyl PS (synthetic saturated PS). However, the lysophospholipid metabolite of PS, lysoPS, was strongly suppressive. These studies suggest that the reversible and selective inhibition of LK-induced macrophage microbicidal activity by PC/PS liposomes is mediated by PS and its lysoPS metabolite. PMID:3745916

Gilbreath, M J; Hoover, D L; Alving, C R; Swartz, G M; Meltzer, M S

1986-09-01

356

Design considerations for liposomal vaccines: Influence of formulation parameters on antibody and cell-mediated immune responses to liposome associated antigens  

PubMed Central

Liposomes (phospholipid bilayer vesicles) are versatile and robust delivery systems for induction of antibody and T lymphocyte responses to associated subunit antigens. In the last 15 years, liposome vaccine technology has matured and now several vaccines containing liposome-based adjuvants have been approved for human use or have reached late stages of clinical evaluation. Given the intensifying interest in liposome-based vaccines, it is important to understand precisely how liposomes interact with the immune system and stimulate immunity. It has become clear that the physicochemical properties of liposomal vaccines – method of antigen attachment, lipid composition, bilayer fluidity, particle charge, and other properties – exert dramatic effects on the resulting immune response. Here, we present a comprehensive review of the physicochemical properties of liposomal vaccines and how they influence immune responses. A discussion of novel and emerging immunomodulators that are suitable for inclusion in liposomal vaccines is also presented. Through a comprehensive analysis of the body of liposomal vaccine literature, we enumerate a series of principles that can guide the rational design of liposomal vaccines to elicit immune responses of a desired magnitude and quality. We also identify major unanswered questions in the field, pointing the direction for future study.

Watson, Douglas S.; Endsley, Aaron N.; Huang, Leaf

2012-01-01

357

Application of Liposomes in Treatment of Rheumatoid Arthritis: Quo Vadis  

PubMed Central

The most common treatments for rheumatoid arthritis include nonsteroidal anti-inflammatory drugs (NSAIDs), corticosteroids, disease modifying antirheumatic drugs (DMARDs), and some biological agents. However, none of the treatments available is able to achieve the ultimate goal of treatment, that is, drug-free remission. This limitation has shifted the focus of treatment to delivery strategies with an ability to deliver the drugs into the synovial cavity in the proper dosage while mitigating side effects to other tissues. A number of approaches like microemulsions, microspheres, liposomes, microballoons, cocrystals, nanoemulsions, dendrimers, microsponges, and so forth, have been used for intrasynovial delivery of these drugs. Amongst these, liposomes have proven to be very effective for retaining the drug in the synovial cavity by virtue of their size and chemical composition. The fast clearance of intra-synovially administered drugs can be overcome by use of liposomes leading to increased uptake of drugs by the target synovial cells, which in turn reduces the exposure of nontarget sites and eliminates most of the undesirable effects associated with therapy. This review focuses on the use of liposomes in treatment of rheumatoid arthritis and summarizes data relating to the liposome formulations of various drugs. It also discusses emerging trends of this promising technology.

Singh, Sachin Kumar; Gulati, Monica

2014-01-01

358

Characterization of liposomes containing iodine-125-labeled radiographic contrast agents  

SciTech Connect

Multilamellar liposomes were prepared containing either iodine-125-labeled (/sup 125/I) diatrizoate or /sup 125/I labeled iotrol in their aqueous phase. The in vitro permeabilities of liposomes containing both contrast agents were measured in the presence of saline and serum at 37 degrees C. Two different phospholipid compositions were studied: phosphatidylcholine/cholesterol/stearylamine (PC/C/S, 8: 1:1 molar ratio) and distearoylphosphatidylcholine/sphingomyelin (DSPC/SM, 5:2 mole ratio). In saline, similar permeabilities were observed for the four phospholipid-contrast agent combinations. In serum, however, leakage of /sup 125/I activity was 2 to 3 times greater from PC/C/S liposomes than from vesicles composed of DSPC/SM. When PC/C/S liposomes that contained /sup 125/I-diatrizoate were injected into rats, the clearance half-times for /sup 125/I activity from the liver, spleen, and whole body were 4.4 hours, 4.5 hours, and 2.8 hours, respectively. Liposomes composed of DSPC/SM cleared at a significantly slower rate from the liver, spleen, and whole body with half-times of 24.0 hours, 18.4 hours, and 17.2 hours observed from these tissues, respectively.

Zalutsky, M.R.; Noska, M.A.; Seltzer, S.E.

1987-02-01

359

Liposomes physically coated with peptides: preparation and characterization.  

PubMed

Physically coating liposomes with peptides of desirable functions is an economic, versatile, and less time-consuming approach to prepare drug delivery vehicles. In this work, we designed three peptides-Ac-WWKKKGGNNN-NH2 (W2K3), Ac-WWRRRGGNNN-NH2(W2R3), Ac-WWGGGGGNNN-NH2(W2G3)-and studied their coating ability on negatively charged liposomes. It was found that the coating was mainly driven by the electrostatic interaction between the peptides' cationic side groups and the acidic lipids, which also mediated the "anchoring " of Trp residuals in the interfacial region of lipid bilayers. At the same conditions, the amount of the coated W2R3 was more than that of W2K3, but the stability of the liposome coated with W2R3 was deteriorated. This was caused by the delocalized charge of the guanidinium group of arginine. The coating of the peptide rendered the liposome pH-responsive behavior but did not prominently change the phase transition temperature. The liposome coated with peptides displayed appropriate pH/temperature dual responsive characteristics and was able to release the content in a controlled manner. PMID:24826785

Su, Cuicui; Xia, Yuqiong; Sun, Jianbo; Wang, Nan; Zhu, Lin; Chen, Tao; Huang, Yanyi; Liang, Dehai

2014-06-01

360

Liposomes as drug deposits in multilayered polymer films.  

PubMed

The ex vivo growth of implantable hepatic or cardiac tissue remains a challenge and novel approaches are highly sought after. We report an approach to use liposomes embedded within multilayered films as drug deposits to deliver active cargo to adherent cells. We verify and characterize the assembly of poly(l-lysine) (PLL)/alginate, PLL/poly(l-glutamic acid), PLL/poly(methacrylic acid) (PMA), and PLL/cholesterol-modified PMA (PMAc) films, and assess the myoblast and hepatocyte adhesion to these coatings using different numbers of polyelectrolyte layers. The assembly of liposome-containing multilayered coatings is monitored by QCM-D, and the films are visualized using microscopy. The myoblast and hepatocyte adhesion to these films using PLL/PMAc or poly(styrenesulfonate) (PSS)/poly(allyl amine hydrochloride) (PAH) as capping layers is evaluated. Finally, the uptake of fluorescent lipids from the surface by these cells is demonstrated and compared. The activity of this liposome-containing coating is confirmed for both cell lines by trapping the small cytotoxic compound thiocoraline within the liposomes. It is shown that the biological response depends on the number of capping layers, and is different for the two cell lines when the compound is delivered from the surface, while it is similar when administered from solution. Taken together, we demonstrate the potential of liposomes as drug deposits in multilayered films for surface-mediated drug delivery. PMID:23514370

Lynge, Martin E; Laursen, Marie Baekgaard; Hosta-Rigau, Leticia; Jensen, Bettina E B; Ogaki, Ryosuke; Smith, Anton A A; Zelikin, Alexander N; Städler, Brigitte

2013-04-24

361

Preparation, characterization, and pharmacodynamics of thermosensitive liposomes containing docetaxel.  

PubMed

A novel thermosensitive liposome (TL) containing docetaxel (DTX) was designed to enhance DTX-targeted delivery and antitumor effect. TL loading DTX (DTX-TL) were prepared by thin film hydration. The mean particle size of the liposomes was about 100 nm, and the drug entrapment efficiency was more than 95%. The phase transition temperature of liposomes was about 42°C. In vitro drug release showed that drug released at 37°C was obviously less than that at 42°C. For in vivo experiments, the human breast tumor model was established by subcutaneous xenotransplantation on nude mice; liposomes and injection containing DTX were injected i.v. in nude mice, followed by exposure of the tumors to hyperthermia (HT) for 30 min after administration. The tumor inhibition ratio of DTX-TL group was significantly higher than the normal injection group. Combining TL with HT enhanced the delivery of DTX and thereby its antitumor effects. The liposomes reported in this paper could potentially produce viable clinical strategies for improved targeting and delivery of DTX for the treatment of breast cancer. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 103:2177-2183, 2014. PMID:24846075

Zhang, Hui; Gong, Wei; Wang, Zhi-Yuan; Yuan, Shou-Jun; Xie, Xiang-Yang; Yang, Yan-Fang; Yang, Yang; Wang, Shan-Shan; Yang, De-Xuan; Xuan, Zi-Xue; Mei, Xing-Guo

2014-07-01

362

Interaction of ionic surfactants with cornea-mimicking anionic liposomes.  

PubMed

The interaction of surface-active molecules with lipid bilayers is ubiquitous both in biological systems and also in several technological applications. Here we explore the interaction of ionic surfactants with liposomes whose composition mimics the ocular epithelia. In this study, liposomes with a composition mimicking ocular epithelia are loaded with calcein dye above the self-quenching concentration. The liposomes are then exposed to surfactants, and the rate of dye leaked from the liposomes due to the interaction of surfactants is measured. Both cationic and anionic surfactants at various concentrations and ionic strengths are explored. Results show that the liposome bilayer permeability to the dye increases on exposure to the surfactants, leading to the release of the dye trapped in the core. However, the dye release stops after a finite time, suggesting a transient increase in permeability followed by healing. The leakage profiles exhibit two different timescales for the cationic surfactant but only one timescale for the anionic surfactant. The total dye leakage increases with surfactant concentration, and at a given concentration, the dye leakage is significantly higher for the cationic surfactants. The timescale for the healing decreases with increasing surfactant concentration, and increasing ionic strength increases the dye leakage for the anionic surfactant. These results show that the surfactant binding to the lipid bilayer increases the permeability while the bilayers heal likely because of the surfactant jump from the outer to the inner leaflet and/or rearrangement into tighter aggregates. PMID:21786813

Gupta, Chhavi; Daechsel, Andrew K; Chauhan, Anuj

2011-09-01

363

Development and Characterization of Liposomal Doxorubicin Hydrochloride with Palm Oil  

PubMed Central

The usage of natural products in pharmaceuticals has steadily seen improvements over the last decade, and this study focuses on the utilization of palm oil in formulating liposomal doxorubicin (Dox). The liposomal form of Dox generally minimizes toxicity and enhances target delivery actions. Taking into account the antiproliferative and antioxidant properties of palm oil, the aim of this study is to design and characterize a new liposomal Dox by replacing phosphatidylcholine with 5% and 10% palm oil content. Liposomes were formed using the freeze_thaw method, and Dox was loaded through pH gradient technique and characterized through in vitro and ex vivo terms. Based on TEM images, large lamellar vesicles (LUV) were formed, with sizes of 438 and 453?nm, having polydispersity index of 0.21 ± 0.8 and 0.22 ± 1.3 and zeta potentials of about ?31 and ?32?mV, respectively. In both formulations, the entrapment efficiency was about 99%, and whole Dox was released through 96 hours in PBS (pH = 7.4) at 37°C. Comparing cytotoxicity and cellular uptake of LUV with CaelyxR on MCF7 and MDA-MBA 231 breast cancer cell lines indicated suitable uptake and lower IC50 of the prepared liposomes.

Sabeti, Bahareh; Noordin, Mohamed Ibrahim; Mohd, Shaharuddin; Hashim, Rosnani; Akbari Javar, Hamid

2014-01-01

364

Development and characterization of liposomal doxorubicin hydrochloride with palm oil.  

PubMed

The usage of natural products in pharmaceuticals has steadily seen improvements over the last decade, and this study focuses on the utilization of palm oil in formulating liposomal doxorubicin (Dox). The liposomal form of Dox generally minimizes toxicity and enhances target delivery actions. Taking into account the antiproliferative and antioxidant properties of palm oil, the aim of this study is to design and characterize a new liposomal Dox by replacing phosphatidylcholine with 5% and 10% palm oil content. Liposomes were formed using the freeze_thaw method, and Dox was loaded through pH gradient technique and characterized through in vitro and ex vivo terms. Based on TEM images, large lamellar vesicles (LUV) were formed, with sizes of 438 and 453?nm, having polydispersity index of 0.21 ± 0.8 and 0.22 ± 1.3 and zeta potentials of about -31 and -32?mV, respectively. In both formulations, the entrapment efficiency was about 99%, and whole Dox was released through 96 hours in PBS (pH = 7.4) at 37°C. Comparing cytotoxicity and cellular uptake of LUV with Caelyx(R) on MCF7 and MDA-MBA 231 breast cancer cell lines indicated suitable uptake and lower IC50 of the prepared liposomes. PMID:24795894

Sabeti, Bahareh; Noordin, Mohamed Ibrahim; Mohd, Shaharuddin; Hashim, Rosnani; Dahlan, Afendi; Javar, Hamid Akbari

2014-01-01

365

Liposome encapsulated polyethylenimine/ODN polyplexes for brain targeting.  

PubMed

Despite high in vitro transfection efficiency, the use of the cationic polymer polyethylenimine (PEI) for systemic application is limited due to its rapid blood clearance and accumulation by RES sites upon intravenous administration of PEI/DNA polyplexes. Therefore, it is important to improve the properties of the PEI/DNA complex with respect to extending the systemic circulation time and suppression of RES uptake. In this study, we applied PEGylated liposome technology for systemic delivery of PEI polyplex of oligodeoxynucleotides (ODN), based on encapsulation of the PEI/ODN polyplexes into PEGylated liposomes. The PEI/ODN polyplex was prepared with a low-branched PEI with MW 2.7 kDa and 20-mer double stranded ODN and was then entrapped into PEGylated liposomes with 95% loading efficiency, leading to a virus-like structure with approximately 130 nm diameter. The PEG-stabilized liposome (PSL) entrapping PEI/ODN polyplexes remained stable in the presence of serum. Upon intravenous administration, the DNA in the PSL was cleared from systemic circulation at a significantly slower rate as compared to the naked PEI/ODN complex. Furthermore, targeting of the PSL with antibody specific to transferrin receptor redirected biodistribution of the entrapped ODN, leading to significant accumulation in the targeted organ, i.e. brain. Encapsulation of the PEI/ODN polyplexes within a long-circulating liposome provided a promising ODN delivery system for in vivo application. PMID:19013203

Ko, Young Tag; Bhattacharya, Raktima; Bickel, Ulrich

2009-02-10

366

Assembly of liposomes controlled by triple helix formation.  

PubMed

Attachment of DNA to the surface of different solid nanoparticles (e.g., gold and silica nanoparticles) is well established, and a number of DNA-modified solid nanoparticle systems have been applied to thermal denaturation analysis of oligonucleotides. We report herein the noncovalent immobilization of oligonucleotides on the surface of soft nanoparticles (i.e., liposomes) and the subsequent controlled assembly by DNA triple helix formation. The noncovalent approach avoids tedious surface chemistry and necessary purification procedures and can simplify and extend the available methodology for the otherwise difficult thermal denaturation analysis of complex triple helical DNA assemblies. The approach is based on lipid modified triplex forming oligonucleotides (TFOs) which control the assembly of liposomes in solution in the presence of single- or double-stranded DNA targets. The thermal denaturation analysis is monitored by ultraviolet spectroscopy at submicromolar concentrations and compared to regular thermal denaturation assays in the absence of liposomes. We report on triplex forming oligonucleotides (TFOs) based on DNA and locked nucleic acid (LNA)/DNA hybrid building blocks and different target sequences (G or C-rich) to explore the applicability of the method for different triple helical assembly modes. We demonstrate advantages and limitations of the approach and show the reversible and reproducible formation of liposome aggregates during thermal denaturation cycles. Nanoparticle tracking analysis (NTA) and dynamic light scattering (DLS) show independently from ultraviolet spectroscopy experiments the formation of liposome aggregates. PMID:23885785

Jakobsen, Ulla; Vogel, Stefan

2013-09-18

367

Mimicking Liver Iron Overload Using Liposomal Ferritin Preparations  

PubMed Central

Close monitoring of liver iron content is necessary to prevent iron overload in transfusion-dependent anemias. Liver biopsy remains the gold standard; however, MRI potentially offers a noninvasive alternative. Iron metabolism and storage is complicated and tissue/disease-specific. This report demonstrates that iron distribution may be more important than iron speciation with respect to MRI signal changes. Simple synthetic analogs of hepatic lysosomes were constructed from noncovalent attachment of horse-spleen ferritin to 0.4 ?m diameter phospholipid liposomes suspended in agarose. Graded iron loading was achieved by varying ferritin burden per liposome as well as liposomal volume fraction. T1 and T2 relaxation times were measured on a 60 MHz NMR spectrometer and compared to simple ferritin-gel combinations. Liposomal-ferritin had 6-fold stronger T2 relaxivity than unaggregated ferritin but identical T1 relaxivity. Liposomal-ferritin T2 relaxivity also more closely matched published results from hemosiderotic marmoset liver, suggesting a potential role as an iron-calibration phantom.

Wood, John C.; Fassler, Joe D.; Meade, Tom

2010-01-01

368

In vitro evaluation of the efficacy of liposomal and pegylated liposomal hydroxyurea.  

PubMed

Breast cancer is one of the most frequent cancer types within women population. Hydroxyurea (HU) is a chemotherapy compound for treatment of patients with cancer diagnosis, including breast cancer associated with several adverse effects. In this study, we applied nanotechnology to decreased drug side effects along with improvement of therapeutic index. Liposomation is widely used in modern pharmacological developments in order to enhance the effects of the drugs. To achieve this, in this study a mixture of phosphatidylcholine and cholesterol was made up and HU was added to the resultant mixture, was then pegylated using Polyethylene Glycol 2000 to increase resistance, applicability and solubility. The mean diameters of nanoliposomal and pegylated nanoliposomal HU were measured by Zeta sizer device and obtained about 402.5 and 338.2 nm. The efficiency of non-pegylated and pegylated liposomal HU was 70.8 and 64.2, respectively. Releasing HU in both formulations was estimated about 25.8 and 21.7 %. Also, this study investigated the cytotoxicity effect of nanoliposomal and pegylated nanoliposomal HU using MTT assay. Results of this investigation showed that the cytotoxic properties of pegylated HU was 3.6 % more than those non-pegylated form, while was 38.93 % more than ordinary from of HU. This study showed that the stability, releasing pattern and cytotoxicity of the pegylated nanoliposomal HU is better than that of nanoliposomal HU. PMID:24478555

Alavi, Seyed Ebrahim; Esfahani, Maedeh Koohi Moftakhari; Ghassemi, Soheil; Akbarzadeh, Azim; Hassanshahi, Gholamhossein

2014-01-01

369

Spectral, photophysical and photochemical properties of tetra- and octaglycosylated zinc phthalocyanines.  

PubMed

Photophysical and photochemical properties of a series of tetra- and octaglycosylated zinc phthalocyanines (ZnPcs) substituted with glucose and galactose moieties have been reported. Spectral properties of these phthalocyanines are compared in DMSO. Absorption spectra of the non-peripherally tetra-substituted ZnPcs 2 showed a significant red shift in their Q-band maxima as compared to the peripherally substituted analog 1. All the complexes gave high triplet quantum yields ranging from 0.68 to 0.88, whereas triplet lifetimes were in the range of 100-430 ?s in argon-saturated solutions. The octagalactosylated ZnPc 3b showed the highest triplet quantum yield and singlet oxygen quantum yield of 0.88 and 0.69, respectively. The fluorescence quantum yields and lifetimes of all the compounds under investigation were within the range of zinc phthalocyanine complexes. PMID:22286670

Iqbal, Zafar; Masilela, Nkosiphile; Nyokong, Tebello; Lyubimtsev, Alexey; Hanack, Michael; Ziegler, Thomas

2012-04-01

370

Quantitative surface-enhanced resonance Raman scattering of phthalocyanine-labelled oligonucleotides  

PubMed Central

The evaluation of phthalocyanine labels for the surface-enhanced resonance Raman scattering (SERRS) detection of oligonucleotides is reported. Three phthalocyanine-labelled oligonucleotides were assessed, each containing a different metal centre. Detection limits for each labelled oligonucleotide were determined using two excitation frequencies where possible. Limits of detection as low as 2.8 × 10?11?mol.?dm?3 were obtained which are comparable to standard fluorescently labelled probes used in previous SERRS studies. The identification of two phthalocyanine-labelled oligonucleotides without separation was also demonstrated indicating their suitability for multiplexing. This study extends the range of labels suitable for quantitative surface-enhanced resonance Raman scattering with silver nanoparticles and offers more flexibility and choice when considering SERRS for quantitative DNA detection.

Macaskill, A.; Chernonosov, A. A.; Koval, V. V.; Lukyanets, E. A.; Fedorova, O. S.; Smith, W. E.; Faulds, K.; Graham, D.

2007-01-01

371

Chromenone 12-crown-4 substituted zinc phthalocyanine complexes: Investigation of spectral, photophysical and photochemical properties  

NASA Astrophysics Data System (ADS)

The synthesis of novel 6,7-[(12-crown-4)-3-[ p-(3,4-dicyanophenoxy)phenyl]coumarin ( 1), 6,7-[(12-crown-4)-3-[ p-(2,3-dicyanophenoxy)phenyl]coumarin ( 2), and their corresponding tetra-(chromenone 12-crown-4)-substituted zinc (II) phthalocyanine complexes ( 3 and 4) have been prepared. These new compounds have been characterized by elementel analysis, 1H NMR ( 1 and 2), MALDI-TOF, IR and UV-Vis spectral data. The fluorescence intensity changes for 1 and 2 by addition of Na + or K + ions have been determined at 25 °C in THF. Intensity of the binding Na +- and K +-complexes ( 1 and 2) have decreased. The effects of the chromenone crown ether on the phthalocyanine molecule concerning photophysical and photochemical properties are also investigated. Photodegredation, singlet oxygen, fluorescence quantum yields, and fluorescence lifetimes of zinc phthalocyanine complexes ( 3 and 4) are also examined in DMSO.

Esenp?nar, Aliye Asl?; Durmu?, Mahmut; Bulut, Mustafa

2011-10-01

372

Highly ordered phthalocyanine thin films on a technically relevant polymer substrate  

NASA Astrophysics Data System (ADS)

We have studied the molecular orientation of well-known representatives of organic semiconductors from the family of the phthalocyanines [copper phthalocyanine (CuPc) and its perfluorinated relative (CuPcF16)] on a conducting polymer thin film using polarization-dependent x-ray absorption spectroscopy. As a polymer substrate PEDOT:PSS [a mixture of poly-3,4-ethylenedioxy-thiophene (PEDOT) and polystyrenesulfonate (PSS), which is often applied as an electrode material in (all-)organic semiconductor devices] was spin coated onto indium-tin-oxide substrates. Even if the interfaces themselves are relatively ill defined (we found recently a mixing of the two organic materials and charge-transfer processes), a very high degree of molecular ordering is observed in the 20-50 nm thick phthalocyanine films.

Peisert, H.; Liu, X.; Olligs, D.; Petr, A.; Dunsch, L.; Schmidt, T.; Chassé, T.; Knupfer, M.

2004-10-01

373

Change in the character of liposomes as a drug carrier by modifying various polyethyleneglycol-lipids.  

PubMed

When liposomes, as a superior drug carrier, are injected intravenously, active liposomes as medicines require polyethyleneglycol (PEG) as a modification tool around the liposomal membrane. PEG modification of a liposome forms a fixed aqueous layer, and the trapping by cells of the reticuloendothelial system (RES) is avoided. Hence, PEG-modified liposomes have long circulation in the bloodstream, and passive targeting to tumors has been achieved by PEG modification. We have been studying the passive targeting by liposomes with the expectation of more usefulness. It was proved a correlation between the PEG molecular weight of PEG-modified liposomes and blood circulation time and antitumor effect, too. Liposomes modified by PEG2000 were useful for uptake into tumor cells. We thought that the re-uptake in the liposomal membrane also increased accumulation. Moreover, it was proved that mixing two different PEGs to modify the liposome surface gives a bigger fixed aqueous layer thickness (FALT) around the liposome, giving the liposome strong antitumor activity. Then, we designed a novel PEG-lipid, 1,2-distearoyl-sn-glycero-3-phospho-ethanolamine-PEG (different double arms PEG; DDA-PEG), which had two different PEGs (2000 and 500) in one molecule. One of the innovative characteristics of DDA-PEG-modified liposome (DDAL) is that it heightens the contact ability with tumor cells. DDAL may be an effective DDS carrier for solving various PEG dilemmas. It was observed that passive targeting by PEG-modified liposomes had different characteristics by changing PEG length, anchor type or those combination. Thus, it should be applied to liposomes suitable for various diseases. PMID:23727913

Sugiyama, Ikumi; Sadzuka, Yasuyuki

2013-01-01

374

Evaluation of polyethylene glycol coated liposomes labeled with Tc-99m as a blood pool agent  

SciTech Connect

This investigation evaluated Tc-99m liposomes coated with polyethylene glycol (PEG) as a blood pool agent in comparison with Tc-99m liposomes carrying no surface charge (Neutral) and with Tc-99m autologous red cells. Liposomes (135 nm diameter) encapsulating glutathione were labeled with Tc-99m using the lipophilic chelator, HMPAO as previously described. Autologous red cells were labeled using an Ultratag kit. Labeling efficiencies averaged 66%, 52%, and 97% for the PEG liposomes. Neutral liposomes, and red cells, respectively. Rabbits (3-3.5 Kg) were injected IV via ear vein with 2.0 mls of PEG liposomes (2 mCi, 17 mg phospholipid/Kg body weight, n=5). Neutral liposomes (1.3 mCi, 17 mg phospholipid/Kg body weight, n=4), or red cells (2.6 mCi, n=2). Gamma camera images were acquired at 5,22, and 45 minutes, and 2,20,and 44 hours post-injection. Blood samples were obtained at each time point to determine clearance kinetics. Circulation half lives of both Tc-99m liposome formulations were longer than Tc-99m red cells (8 hrs), with the half life of PEG liposomes (35 hrs) 1.6 times longer than Neutral liposomes (22 hrs). In vivo stability of the Tc-99m label was excellent for the liposomes with only 3.5-4% bladder activity at 45 minutes compared to 12% bladder activity for the red cells. Excellent blood pool images were obtained for the PEG liposomes in the rabbit. Heart/liver ratios calculated from region of interest analysis of 45 minutes images were 1.9, 1.5, and 1.7 for PEG liposomes, Neutral liposomes and red cells. This study demonstrates the feasibility of using Tc-99m PEG liposomes to perform gated cardiac blood pool and rapid gastrointestinal bleeding studies.

Phillips, W.T.; Klipper, R.; Goins, B. [Univ. of Texas Health Science Center, San Antonio, TX (United States)

1994-05-01

375

The organ distribution of liposome-encapsulated and free cobalt in rats. Liposomes decrease the cardiac uptake of the metal  

SciTech Connect

Rats were administered intravenously liposome-encapsulated or free cobalt, and the organ distribution of the metal was explored using Co{sup 57} tracer. Two hours after administration, the cobalt level in the heart was about 40 % of the control when given in sphingomyelin (SM)/cholesterol (CH) (1:1 mole ratio) liposomes. These vesicles also tended to decrease the uptake of cobalt in the kidney and the carcass, and to increase it in the spleen and the bones. Liposomes prepared from soybean phosphatidylcholine (SPC)/CH (1:1) had no effect on the uptake of cobalt in the heart, whereas increased its level in the spleen, liver and lung. The time-course of cobalt deposition in the organs displayed substantial variation with the different preparations. Most importantly, no buildup of cobalt level was observed in the heart when the metal was administered in SM/CH vesicles. While confirming known effects of liposomes on the organ-distribution of entrapped drugs, our findings suggest that administration of cobalt in SM/CH liposome-encapsulated form may result in decreased cardiotoxicity and thus increased safety of cobalt-treatment in some anemias.

Garcia, R.; Eskelson, C.D.; Chvapil, M. (Univ. of Arizona, Tucson (USA)); Szebeni, J. (Univ. of Arizona, Tucson (USA) National Institute of Food Hygiene and Nutrition, Budapest (Hungary))

1989-01-01

376

Double emulsion templated monodisperse phospholipid liposomes incorporating Doxorubicin hydrochloride  

NASA Astrophysics Data System (ADS)

We present a novel approach for fabricating monodisperse phospholipid liposomes incorporating water soluble anticancer drug Doxorubicin hydrochloride using controlled w/o/w double emulsions as templates. Glass-capillary microfluidics is used to generate monodisperse w/o/w double emulsion templates and double emulsion droplet size is from 20 to 100 um according to different flow rates. We show that the high uniformity in size and shape of the templates are maintained in the final phospholipid liposomes after a solvent removal step by Nikon eclipse microscopy. The lipid bilayers encapsulating anticancer drug inside is retained after the emulsion drops are converted to vesicles. The liposomes vesicles are promising water soluble anticancer drug delivery vehicles.

Hai, Mingtan; Weitz, David

2012-02-01

377

Liposomal extended-release bupivacaine for postsurgical analgesia.  

PubMed

When physicians consider which analgesia to use postsurgery, the primary goal is to relieve pain with minimal adverse side effects. Bupivacaine, a commonly used analgesic, has been formulated into an aqueous suspension of multivesicular liposomes that provide long-lasting analgesia for up to 72 hours, while avoiding the adverse side effects of opioids. The increased efficacy of liposomal extended-release bupivacaine, compared to bupivacaine hydrochloride, has promoted its usage in a variety of surgeries including hemorrhoidectomy, bunionectomy, inguinal hernia repair, total knee arthroplasty, and augmentation mammoplasty. However, like other bupivacaine formulations, the liposomal extended-release bupivacaine does have some side effects. In this brief review, we provide an update of the current knowledge in the use of bupivacaine for postsurgical analgesia. PMID:24043932

Lambrechts, Mark; O'Brien, Michael J; Savoie, Felix H; You, Zongbing

2013-01-01

378

Trigger release liposome systems: local and remote controlled delivery?  

PubMed

Target-specific delivery has become an integral area of research in order to increase bioavailability and reduce the toxic effects of drugs. As a drug-delivery option, trigger-release liposomes offer sophisticated targeting and greater control-release capabilities. These are broadly divided into two categories; those that utilise the local environment of the target site where there may be an upregulation in certain enzymes or a change in pH and those liposomes that are triggered by an external physical stimulus such as heat, ultrasound or light. These release mechanisms offer a greater degree of control over when and where the drug is released; furthermore, targeting of diseased tissue is enhanced by incorporation of target-specific components such as antibodies. This review aims to show the development of such trigger release liposome systems and the current research in this field. PMID:22208705

Bibi, Sagida; Lattmann, E; Mohammed, Afzal R; Perrie, Yvonne

2012-01-01

379

Topical liposome delivery of molecules to hair follicles in mice.  

PubMed

The hair cycle consisting of growing and resting phases, is subject to widespread disease such as androgenic alopecia or loss of pigment which are in need of effective, targeted therapeutics. In order to develop a hair-follicle delivery system we demonstrate here that phosphatidylcholine liposomes entrapping either the fluorescent dye calcein or the pigment melanin can deliver these molecules into the hair follicle and hair shafts of mice when applied topically. Liposomal delivery of these molecules is time dependent. Negligible amounts of delivered molecules enter the dermis, epidermis or blood stream thereby demonstrating the enrichment of follicle delivery. Naked calcein and melanin are trapped in the stratum corneum and are unable to enter the follicle. The potential of the hair-follicle liposome delivery system for therapeutic use for hair disease is discussed. PMID:9039973

Li, L; Hoffman, R M

1997-02-01

380

Gemcitabine-loaded liposomes: rationale, potentialities and future perspectives  

PubMed Central

This review describes the strategies used in recent years to improve the biopharmaceutical properties of gemcitabine, a nucleoside analog deoxycytidine antimetabolite characterized by activity against many kinds of tumors, by means of liposomal devices. The main limitation of using this active compound is the rapid inactivation of deoxycytidine deaminase following administration in vivo. Consequently, different strategies based on its encapsulation/complexation in innovative vesicular colloidal carriers have been investigated, with interesting results in terms of increased pharmacological activity, plasma half-life, and tumor localization, in addition to decreased side effects. This review focuses on the specific approaches used, based on the encapsulation of gemcitabine in liposomes, with particular attention to the results obtained during the last 5 years. These approaches represent a valid starting point in the attempt to obtain a novel, commercializable drug formulation as already achieved for liposomal doxorubicin (Doxil®, Caelyx®).

Federico, Cinzia; Morittu, Valeria M; Britti, Domenico; Trapasso, Elena; Cosco, Donato

2012-01-01

381

Design of liposomal colloidal systems for ocular delivery of ciprofloxacin  

PubMed Central

Ophthalmic drug bioavailability is limited due to protective mechanisms of the eye which require the design of a system to enhance ocular delivery. In this study several liposomal formulations containing ciprofloxacin (CPX) have been formulated using reverse phase evaporation technique with final dispersion of pH 7.4. Different types of phospholipids including Phosphatidylcholine, Dipalmitoylphosphatidylcholine and Dimyristoyl-sn-glycero-3-phosphocholine were utilized. The effect of formulation factors such as type of phospholipid, cholesterol content, incorporation of positively charging inducing agents and ultrasonication on the properties of the liposomal vesicles was studied. Bioavailability of selected liposomal formulations in rabbit eye aqueous humor has been investigated and compared with that of commercially available CPX eye drops (Ciprocin®). Pharmacokinetic parameters including Cmax, Tmax, elimination rate constant, t1/2, MRT and AUC0–?, were determined. The investigated formulations showed more than three folds of improvement in CPX ocular bioavailability compared with the commercial product.

Taha, Ehab I.; El-Anazi, Magda H.; El-Bagory, Ibrahim M.; Bayomi, Mohsen A.

2013-01-01

382

Recent Trends in Multifunctional Liposomal Nanocarriers for Enhanced Tumor Targeting  

PubMed Central

Liposomes are delivery systems that have been used to formulate a vast variety of therapeutic and imaging agents for the past several decades. They have significant advantages over their free forms in terms of pharmacokinetics, sensitivity for cancer diagnosis and therapeutic efficacy. The multifactorial nature of cancer and the complex physiology of the tumor microenvironment require the development of multifunctional nanocarriers. Multifunctional liposomal nanocarriers should combine long blood circulation to improve pharmacokinetics of the loaded agent and selective distribution to the tumor lesion relative to healthy tissues, remote-controlled or tumor stimuli-sensitive extravasation from blood at the tumor's vicinity, internalization motifs to move from tumor bounds and/or tumor intercellular space to the cytoplasm of cancer cells for effective tumor cell killing. This review will focus on current strategies used for cancer detection and therapy using liposomes with special attention to combination therapies.

Perche, Federico; Torchilin, Vladimir P.

2013-01-01

383

Ultraviolet- and sunlight-induced lipid peroxidation in liposomal membrane  

SciTech Connect

Ultraviolet radiation and sunlight caused lipid peroxidation in the liposomal membrane (as detected by measurement of the oxidation index, A/sub 233//A/sub 215/, and the amount of malondialdehyde formed) and made the membrane leaky (as revealed by the release of the trapped chromate anions). The oxidation index and the formation of malondialdehyde increased linearly with increasing dose of radiation and depended significantly on the dose rate. The effects were smaller in liposomes derived from Vibrio cholerae phospholipid than in those derived from egg lecithin. The effects of the radiation dose and dose rate on hemolysis and peroxidation (MDA formation) of the erythrocyte membrane followed a similar pattern. A direct correlation between the percentage leakage of chromate (Y) and the oxidation index (X) of the liposomal system was obtained as Y = 236.5 x X.

Mandal, T.K.; Chatterjee, S.N.

1980-08-01

384

Preclinical evaluation of zinc phthalocyanine tetrasulfonate-based PDT  

NASA Astrophysics Data System (ADS)

Photodynamic therapy (PDT) involves the light activation of a drug within a tumor causing selective tumor cell death. Unfortunately, some photosensitizing drugs have been associated with adverse reactions in veterinary patients. Zinc phthalocyanine tetrasulfonate (ZnPcS4) is a promising second-generation photosensitizer for use in veterinary medicine, however, it cannot be applied clinically until safety and efficacy data are available. ZnPcS4 was given to Swiss Webster mice to assess acute toxicity. Doses >100 mg/kg were associated with acute toxicity and mortality, and doses >100 mg/kg resulted in renal tubular nephrosis, suggesting that the minimum toxic dose is approximately 100 mg/kg. Based on these data, a Phase I clinical trial of ZnPcS4-based PDT in tumor-bearing dogs is underway, with ZnPcS4 doses up to 2 mg/kg producing no apparent toxicity. Tumor response has been observed after ZnPcS4-based PDT using doses as low as 0.25 mg/kg, suggesting that conventional phase I clinical trials may not be appropriate for PDT protocols.

Borgatti-Jeffreys, Antonella; Hooser, Stephen B.; Miller, Margaret A.; Thomas, Rose M.; deGortari, Amalia; Lucroy, Michael D.

2005-04-01

385

Electrochemical and spectroelectrochemical studies of cobalt phthalocyanine polymers  

SciTech Connect

Spectroscopic and electrochemical properties of cobalt phthalocyanine (CoPc) polymers, which are believed to have two- and three-dimensional structures, have been studied and the results are reported. The spectral bands are shifted and a significant band broadening is observed as expected. The cyclic voltammetric results suggest that there are two energetically different Co ions in the three-dimensional polymer. The spectroscopic and electrochemical results indicate that the Co ion on the polymers appears to be in a partially reduced state in solution phases, as evidenced by the presence of the metal-ligand charge-transfer band. When adsorbed onto the carbon surface, this band becomes more prominent even in the formally unreduced state, perhaps due to the coordination of {pi}-electron clouds of carbon into the coaxial axis of the complex, resulting in the partially reduced Co ion. As a result of this partial reduction, the electron transfer from CoPc polymers appears to be enhanced, which becomes the basis for the catalytic activities observed for this class of compounds.

Ortiz, B.; Park, S.M. [Univ. of New Mexico, Albuquerque, NM (United States). Dept. of Chemistry; Doddapaneni, N. [Sandia National Labs., Albuquerque, NM (United States). Battery Research Dept.

1996-06-01

386

Resonance Raman spectra of. cap alpha. -copper phthalocyanine  

SciTech Connect

Raman spectra of ..cap alpha..-copper phthalocyanine (..cap alpha..-CuPc) were recorded at room temperature and at 10 K with excitation wavelengths between 457 and 714 nm. Resonance enhancement was greatest for modes for which the largest displacements were on either the inner five-membered ring of the isoindole groups or the inner macrocycle and consequently assignment of the bands to modes of the entire molecule was possible by comparison with nickel octaethylporphyrin. Four out of five bands resonant in the Q band region and preresonant near the B band absorption region are totally symmetric modes. B band preresonance occurs more strongly with high-frequency modes. At low temperatures, multimode interactions are reduced and profiles were obtained which can be compared with solution profiles of porphyrins. Both Q/sub x/ and Q/sub y/ 0-0 scattering can be identified and a helper mode is evident. A term enhancement predominates, with B/sub 1g/ and B/sub 2g/ modes enhanced because of a Jahn-Teller distortion of the excited state. The resonance studies, together with electronic absorption spectra and published theoretical studies, confirm that the Q band in ..cap alpha..-CuPc is largely due to an allowed ..pi..-..pi..* transition associated mainly with the macrocycle and inner five-membered rings of the isoindole groups. 25 references, 5 figures, 2 tables.

Bovill, A.J.; McConnell, A.A.; Nimmo, J.A.; Smith, W.E.

1986-02-13

387

Chloroaluminum phthalocyanine thin films: chemical reaction and molecular orientation.  

PubMed

The chemical transformation of the polar chloroaluminum phthalocyanine, AlClPc, to ?-(oxo)bis(phthalocyaninato)aluminum(III), (PcAl)2O, in thin films on indium tin oxide is studied and its influence on the molecular orientation is discussed. The studies were conducted using complementary spectroscopic techniques: Raman spectroscopy, X-ray photoelectron spectroscopy, and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. In addition, density functional theory calculations were performed in order to identify specific vibrations and to monitor the product formation. The thin films of AlClPc were annealed in controlled environmental conditions to obtain (PcAl)2O. It is shown that the chemical transformation in the thin films can proceed only in the presence of water. The influence of the reaction and the annealing on the molecular orientation was studied with Raman spectroscopy and NEXAFS spectroscopy in total electron yield and partial electron yield modes. The comparison of the results obtained from these techniques allows the determination of the molecular orientation of the film as a function of the probing depth. PMID:23494276

Latteyer, Florian; Peisert, Heiko; Uihlein, Johannes; Basova, Tamara; Nagel, Peter; Merz, Michael; Schuppler, Stefan; Chassé, Thomas

2013-05-01

388

Humidity sensors based on aluminum phthalocyanine chloride thin films  

NASA Astrophysics Data System (ADS)

In present paper, the fabrication and humidity sensing properties of aluminum phthalocyanine chloride (AlPcCl) thin film based sensors have been presented. AlPcCl thin films with nominal thickness of 50-100 nm are deposited on glass substrates between pre-deposited 50 nm thick aluminum electrodes. The gap between the electrodes is 50 ?m. It is observed that the sensing mechanism is based on the variation of resistance with change in humidity. For change in relative humidity (RH) from 20% to 92%, the change in resistance is 22.2×102 and 13.3×102 times respectively for the sensors having 50 nm and 100 nm thick AlPcCl films, while the 1 h annealing of these samples at 100 °C results in increase in average sensitivity up to 30% and 40% respectively. The consequence of measuring frequency and absorption-desorption behavior of the humidity sensor are also discussed in detail. It is also observed that annealing results in minimization of hysteresis and reduction of recovery time (?rec) up to 63% and 70% in sensors with 50 nm and 100 nm thick organic film respectively, while the response (?res) time is 10 s for both the sensors.

Chani, Muhammad Tariq Saeed; Karimov, Kh. S.; Ahmad Khalid, F.; Raza, Kabeer; Umer Farooq, Muhammad; Zafar, Qayyum

2012-08-01

389

Electrochromic lutetium phthalocyanine films for in situ detection of NADH  

NASA Astrophysics Data System (ADS)

A simple and sensitive method for the detection of NADH on a glass substrate modified with spin coated electrochromic [(C6H13S)8Pc]2Lu is presented. The modification of a [(C6H13S)8Pc]2Lu sensing layer was achieved chemically. The functionalized layer shows an efficient activity towards the NADH at conc. as low as 1 × 10-5 M. The in situ UV-Vis and Raman measurements were carried out to study the interaction of oxidized films with NADH. The electrochromic behaviour of [(C6H13S)8Pc]2Lu thin films was examined in detail under various conditions. The spin coated films deposited on glass substrate were chemically oxidized and were found to change the colour. The oxidized films were believed to be reduced to its natural form on interaction with NADH. The colour of the film changed from green to brownish-purple after interaction with NADH. Reversible electrochromism was observed, leading reusable sensor film. The transformation of the oxidised phthalocyanine films into neutral form was monitored by both in situ UV-Vis and Raman techniques.

Basova, Tamara; Gürek, Ay?e Gül; Ahsen, Vefa; Ray, Asim

2013-01-01

390

Spin tuning of electron-doped metal-phthalocyanine layers.  

PubMed

The spin state of organic-based magnets at interfaces is to a great extent determined by the organic environment and the nature of the spin-carrying metal center, which is further subject to modifications by the adsorbate-substrate coupling. Direct chemical doping offers an additional route for tailoring the electronic and magnetic characteristics of molecular magnets. Here we present a systematic investigation of the effects of alkali metal doping on the charge state and crystal field of 3d metal ions in Cu, Ni, Fe, and Mn phthalocyanine (Pc) monolayers adsorbed on Ag. Combined X-ray absorption spectroscopy and ligand field multiplet calculations show that Cu(II), Ni(II), and Fe(II) ions reduce to Cu(I), Ni(I), and Fe(I) upon alkali metal adsorption, whereas Mn maintains its formal oxidation state. The strength of the crystal field at the Ni, Fe, and Mn sites is strongly reduced upon doping. The combined effect of these changes is that the magnetic moment of high- and low-spin ions such as Cu and Ni can be entirely turned off or on, respectively, whereas the magnetic configuration of MnPc can be changed from intermediate (3/2) to high (5/2) spin. In the case of FePc a 10-fold increase of the orbital magnetic moment accompanies charge transfer and a transition to a high-spin state. PMID:24635343

Stepanow, Sebastian; Lodi Rizzini, Alberto; Krull, Cornelius; Kavich, Jerald; Cezar, Julio C; Yakhou-Harris, Flora; Sheverdyaeva, Polina M; Moras, Paolo; Carbone, Carlo; Ceballos, Gustavo; Mugarza, Aitor; Gambardella, Pietro

2014-04-01

391

Organic semiconductor nickel phthalocyanine-based photocapacitive and photoresistive detector  

NASA Astrophysics Data System (ADS)

In this study, the photosensitive organic semiconductor nickel phthalocyanine (NiPc) is investigated as a photocapacitive and photoresistive detector. NiPc thin film is grown by vacuum thermal evaporation on an indium tin oxide (ITO)-coated glass substrate. Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is deposited as a top electrode by drop-casting to fabricate the ITO/NiPc/PEDOT:PSS light detector. It has been observed that under the unmodulated filament lamp illumination of up to 9720 lux the capacitance of the detectors increased up to 21, 18 and 4% at a frequency of measuring voltage of 120 Hz, 1 kHz and 10 kHz, respectively, under dark conditions. The change in resistance with the variation in the intensity of light is also investigated. The capacitance and resistance of the light detector decrease with an increase in the frequency. It is assumed that the photocapacitive and photoresistive response of the detector is associated with polarization occurring due to the transfer of photo-generated electrons and holes. The calculated results are in reasonable agreement with the experimental results.

Shah, Mutabar; Karimov, Kh S.; Sayyad, M. H.

2010-07-01

392

Environment effects on the oxidation of thiols: cobalt phthalocyanine as a test case  

NASA Astrophysics Data System (ADS)

The reactivity of Co(II) phthalocyanine toward the oxidation of 2-mercaptoethanol was investigated using first principle theoretical methods. Calculations have been carried out using a hybrid Hartree-Fock/density functional approach (PBE0). Solvent effects have been included through a polarizable continuum model (C-PCM), while surface effects have been mimicked by a supramolecular (phthalocyanine + carbon cluster) approach. The influences of chemical environment and of the medium on reactivity were analyzed using two different reactivity descriptors, the donor-acceptor intermolecular hardness and the electrophilicity index. Our results show that solvent and surface have a cooperative effect, both increasing the reactivity of the adsorbed complex.

Ciofini, Ilaria; Bedioui, Fethi; Zagal, José H.; Adamo, Carlo

2003-07-01

393

Metal-phthalocyanine functionalized carbon nanotubes as catalyst for the oxygen reduction reaction: A theoretical study  

NASA Astrophysics Data System (ADS)

The covalent functionalization of metallic single-walled carbon nanotubes (CNTs) with transition metal phthalocyanines (MPc, with M = Mn, Fe and Co) are addressed by density functional calculations. The CNT-MPc catalytic activity toward the oxygen reduction reaction (ORR) is investigated through the O2 stretching frequency adsorbed on the phthalocyanine metal center. We find better reduction abilities when the CNT functionalization occurs through sp2-like bonds. Multiple stable-spin states for the M-O2 adduct are also found for M = Mn and Fe, suggesting higher ORR rates. The CNT-MPc complexes show metallic characteristics, suggesting favorable conditions to work as ORR cathode catalysts in fuel cells.

Orellana, Walter

2012-07-01

394

Influence of film thickness and air exposure on the transport gap of manganese phthalocyanine  

SciTech Connect

The interface formation between manganese phthalocyanine (MnPc) and cobalt was investigated combining ultraviolet photoelectron spectroscopy and inverse photoelectron spectroscopy. The transport band gap of the MnPc increases with the film thickness up to a value of (1.2 {+-} 0.3) eV while the optical band gap as determined from spectroscopic ellipsometry amounts to 0.5 eV. The gap values are smaller compared to other phthalocyanines due to metallic Mn 3d states close to the Fermi level. The transport band gap was found to open upon air exposure as a result of the disappearance of the occupied 3d electronic states.

Haidu, F.; Fechner, A.; Salvan, G.; Gordan, O. D.; Fronk, M.; Zahn, D. R. T. [Semiconductor Physics, Chemnitz University of Technology, D-09107 Chemnitz (Germany); Lehmann, D. [Semiconductor Physics, Chemnitz University of Technology, D-09107 Chemnitz (Germany); INNOVENT Technology Development, D-07745 Jena (Germany); Mahns, B.; Knupfer, M. [Electronic and Optical Properties Department, IFW Dresden, D-01171 Dresden (Germany)

2013-06-15

395

Photoreduction of methylviologen catalyzed by phthalocyanine complexes of yttrium(III) and lanthanoid(III) metals  

SciTech Connect

The preparation of phthalocyanine complexes of yttrium, samarium, gadolinium, ytterbium, and lutetium is reported. The PcLnAcO complex (Pc = phthalocyanine dianion and AcO = acetate anion) was found to act as the sensitizer for the photoreduction of methylviologen chloride (MVCl{sub 2}) in a methanol solution upon irradiation with visible light. On the basis of data from visible spectrophotometric studies and laser flash-photolysis studies, the observation is made that the photoreduction of metalophthalocyanine complexes proceeds via an oxidative process, and a reaction scheme is proposed. 15 refs., 2 figs.

Kasuga, Kuninobu; Takahashi, Seiji; Tsukahara, Keiichi (Shimane Univ., Matsue (Japan)); Ohno, Takeshi (Osaka Univ. (Japan))

1990-01-24

396

Synthesis, photophysical studies and (1)O2 generation of carboxylate-terminated zinc phthalocyanine dendrimers.  

PubMed

Highly water-soluble dendrimers have been prepared consisting of a central zinc phthalocyanine moiety and dendritic wedges with terminal carboxylate groups. The biggest polyelectrolyte comprises 32 negative charges at the dendrimer surface. The photophysical studies reveal a strong correlation between the degree of dendritic environment, the extent of aggregation, and the ability to generate singlet oxygen in aqueous media. Compared to dendrimers having an axial derivatization the functionalization on the outer rim also significantly improves the phthalocyanine's ability to photosensitize singlet oxygen. PMID:24629699

Setaro, Francesca; Ruiz-González, Rubén; Nonell, Santi; Hahn, Uwe; Torres, Tomás

2014-07-01

397

Inhomogeneous broadening of the zero phonon line of phthalocyanine in superfluid helium droplets  

NASA Astrophysics Data System (ADS)

The electronic origin band of the S1<--S0 transition of monomer phthalocyanine doped into liquid helium droplets consist of a single zero phonon line (ZPL) and a structured phonon wing. The latter reflects the low frequency modes of the helium droplet. At very high resolution (1 MHz) the asymmetric spectrum of the ZPL of phthalocyanine provides no indication of a rotational substructure. Changes in the asymmetry and the peak position of the ZPL with variation of the average droplet size are in very good agreement with an inhomogeneous model line shape.

Slenczka, Alkwin; Dick, Bernhard; Hartmann, Matthias; Peter Toennies, J.

2001-12-01

398

X-ray photoelectron investigation of charge distribution in copper(II) phthalocyanine complexes  

Microsoft Academic Search

The charged states of atoms in unsubstituted copper(II) phthalocyanine (CuPcH16) and hexade-cafluorinated copper(II) phthalocyanine (CuPcF16) complexes and in thin films of them deposited on silicon substrates by vacuum thermal evaporation are investigated by X-ray\\u000a photoelectron spectroscopy (XPS). The C(1s), N(1s), Cu(2p) core level energies and the charged states of atoms in the studied complexes are calculated using the DFT method.

R. V. Gulyaev; N. A. Kryuchkova; L. N. Mazalov; A. I. Boronin; T. V. Basova; V. A. Plyashkevich

2011-01-01

399

Modulation of the electronic and spectroscopic properties of Zn(II) phthalocyanines by their substitution pattern.  

PubMed

Four isomerically pure octasubstituted zinc phthalocyanines with variations in the attachment atom and positions of the substituents were selected for a systematic investigation of the effect of the substitution pattern on their electronic and spectroscopic properties. Effects which were investigated are the position, the electron donating and withdrawing properties, and the donating force of the substituent. The results are discussed and interpreted based on theoretical and experimental determination of the orbital levels. This work allows us to highlight which substitution patterns are the most suitable considering different common applications of phthalocyanines. PMID:24667853

Topal, Sevinc Z; ??ci, Ümit; Kumru, Ufuk; Atilla, Devrim; Gürek, Ay?e G; Hirel, Catherine; Durmu?, Mahmut; Tommasino, Jean-Bernard; Luneau, Dominique; Berber, Savas; Dumoulin, Fabienne; Ahsen, Vefa

2014-05-14

400

Transdermal delivery of butamben using elastic and conventional liposomes.  

PubMed

Gel formulations containing the local anesthetic butamben (BTB) encapsulated in either conventional (BTBLUV) or elastic (BTBLUV-EL) liposomes were prepared and characterized, and then evaluated in terms of their skin permeability. Parameters measured included vesicle size and surface charge, BTB fluorescence anisotropy, encapsulation efficiency, partition coefficient and liposomal membrane organization. Encapsulation efficiencies and membrane/water partition coefficients were determined using a phase separation. The partition coefficients of the elastic and conventional formulations were 2025?±?234 and 1136?±?241, respectively. The sizes of the elastic and conventional liposomes did not change significantly (p?>?0.05) following incorporation of the anesthetic. As expected, the elastic liposomes presented order parameters that were lower than those of the conventional liposomes, as determined by electron paramagnetic resonance with a 5-stearic acid nitroxide probe incorporated into the bilayer. After 8?h, the fluxes into the receiving solution (µg/cm(2)/h) were 6.95?±?1.60 (10% BTB), 23.17?±?6.09 (10% BTBLUV) and 29.93?±?6.54 (10% BTBLUV-EL). The corresponding time lags (h) were 1.90?±?0.48, 1.23?±?0.28 and 1.57?±?0.38, respectively. The permeability coefficients (10(-3?)cm/h) were 1.02?±?0.23, 2.96?±?0.77 and 4.14?±?0.9, for 10% BTB, 10% BTBLUV and 10% BTBLUV-EL, respectively. The results demonstrate that anesthetic access through the skin can be considerably enhanced using liposomal gel formulations, compared to plain gel formulations. PMID:23697904

Cereda, Cintia Maria Saia; Franz-Montan, Michelle; da Silva, Camila Morais Gonçalves; Casadei, Bruna Renata; Domingues, Cleyton Crepaldi; Tofoli, Giovana Radomille; de Araujo, Daniele Ribeiro; de Paula, Eneida

2013-09-01

401

Selective killing of T lymphocytes by phototoxic liposomes  

SciTech Connect

Two-fold specificity in drug delivery obtained through the localized activation of drugs by physical means and the attachment of drugs to proteins that bind to target cells might be used for highly selective cancer chemotherapy or for immunosuppression. Toward this end, a monoclonal antibody against an antigen on the surface of T lymphocytes was covalently attached to liposomes containing a phototoxic drug, pyrene, bound to the lipid bilayer. When unfractionated peripheral blood lymphocytes, or B- and T-cell lines, were irradiated after treatment with these liposomes, T cells were killed while B cells were spared, demonstrating the validity of the approach in a simple in vitro assay.

Yemul, S.; Berger, C.; Estabrook, A.; Suarez, S.; Edelson, R.; Bayley, H.

1987-01-01

402

Selective Killing of T Lymphocytes by Phototoxic Liposomes  

NASA Astrophysics Data System (ADS)

Two-fold specificity in drug delivery obtained through (i) the localized activation of drugs by physical means and (ii) the attachment of drugs to proteins that bind to target cells might be used for highly selective cancer chemotherapy or for immunosuppression. Toward this end, a monoclonal antibody against an antigen on the surface of T lymphocytes was covalently attached to liposomes containing a phototoxic drug, pyrene, bound to the lipid bilayer. When unfractionated peripheral blood lymphocytes, or B- and T-cell lines, were irradiated after treatment with these liposomes, T cells were killed while B cells were spared, demonstrating the validity of the approach in a simple in vitro assay.

Yemul, Shrishailam; Berger, Carole; Estabrook, Alison; Suarez, Sylvia; Edelson, Richard; Bayley, Hagan

1987-01-01

403

Liposome fusion rates depend upon the conformation of polycation catalysts.  

PubMed

Cryo-TEM and NaCl-leakage experiments demonstrated that the cationic polymer polylysine induces fusion of anionic liposomes but that the cationic polymer poly(N-ethyl-4-vinylpyridinium bromide) (PEVP) does not, although both polymers bind strongly to the liposomes. The difference was traced to the thickness of the coatings at constant charge coverage. Polylysine is believed to form planar ?-sheets that are sufficiently thin to allow membrane fusion. In contrast, looping and disorganization among adsorbed PEVP molecules physically prevent fusion. A similar effect is likely to be applicable to important polycation-induced fusion of cell membranes. PMID:21322595

Yaroslavov, Alexander A; Sybachin, Andrey V; Kesselman, Ellina; Schmidt, Judith; Talmon, Yeshayahu; Rizvi, Syed A A; Menger, Fredric M

2011-03-01

404

Pharmacokinetics of poly(hydroxyethyl- l-asparagine)-coated liposomes is superior over that of PEG-coated liposomes at low lipid dose and upon repeated administration  

Microsoft Academic Search

‘Stealth’ liposomes with a poly(ethylene glycol) (PEG) coating are frequently studied for drug delivery and diagnostic purposes because of their prolonged blood circulation kinetics. However, several recent reports have demonstrated that PEG-liposomes are rapidly cleared at single low lipid doses (<1 ?mol\\/kg) and upon repeated administration (time interval between the injections 5 days–4 weeks). Recently, poly(amino acid)-based stealth liposome coatings have

Birgit Romberg; Christien Oussoren; Cor J. Snel; Myrra G. Carstens; Wim E. Hennink; Gert Storm

2007-01-01

405

Injection of PEGylated liposomes in rats elicits PEG-specific IgM, which is responsible for rapid elimination of a second dose of PEGylated liposomes  

Microsoft Academic Search

Steric stabilization of the surface of liposomes by a PEG conjugated lipid results in reduced recognition of the liposomes by the cells of the mononuclear phagocyte system and consequently extended their circulation times (t1\\/2?20h in rat). Recently, we reported on the “accelerated blood clearance phenomenon”, causing ‘invisible’ PEGylated liposomes to be cleared very rapidly from the circulation upon repeated injection.

Tatsuhiro Ishida; Masako Ichihara; XinYu Wang; Kenji Yamamoto; Junji Kimura; Eiji Majima; Hiroshi Kiwada

2006-01-01

406

Liposome surface functionalization based on different anchoring lipids via Staudinger ligation.  

PubMed

Liposome surface functionalization facilitates numerous potential applications of liposomes, such as enhanced stability, bioactive liposome conjugates, and targeted drug, gene and image agent delivery. Anchoring lipids are needed for grafting ligands of interest and play important roles in ligand grafting density, liposome stability, and liposome chemical and physical characteristics as well. In this report, glyco-functionalized liposome systems based on two kinds of anchoring lipids, phosphatidylethanolamine (PE) and cholesterol (Chol), were prepared by post chemically selective functionalization via Staudinger ligation. The size and stability of the liposomes were confirmed by dynamic light scattering (DLS). Particularly, the impact of anchor lipids on the stability of glyco-functionalized liposomes was investigated by comparing two different anchor lipids, namely Chol-PEG2000-TP and DSPE-PEG2000-TP. In addition, the encapsulation and releasing capacity of the glycosylated liposome based on the two anchoring lipids were investigated by entrapping 5,6-carboxyfluorescein (CF) dye and monitoring the fluorescence leakage, respectively. Furthermore, the density and accessibility of grafted carbohydrate residues on the liposome surface were evaluated for the two anchoring lipid-derived liposomes with lectin binding, respectively. PMID:24413731

Vabbilisetty, Pratima; Sun, Xue-Long

2014-02-28

407

Effects of complexation between liposome and poly(malic acid) on aggregation and leakage behaviour.  

PubMed

The design and development of novel pH-sensitive liposomes were investigated to improve the release of liposome-encapsulated chemicals. Stable liposomes comprising of L-alpha-dipalmitoylphosphatidylcholine (DPPC) and poly(carboxylic acid) were prepared and characterized. Poly(malic acid) (PMLA) was chosen as a fusogen, because of its excellent biodegradability in physiological regions. Octyl groups introduced in the poly(malic acid) worked as anchors at the surface of the liposomes and made a remarkable contribution to complexing. The interaction between the liposomes and the polyacids was studied in terms of the change in size of the liposomes. The influences of molecular weight and amounts of polymer upon their characteristics, especially fusion, were discussed. The influences of pH change with respect to the association behavior of the liposomes such as aggregation and fusion were estimated by the particle size of the liposomes, turbidimetry of the solution and resonance energy transfer assay. From the results of these studies, it was shown that more tightly complexed liposomes aggregated and fused more positively with increasing acidity of the solution. The leakage of calcein entrapped in the inner aqueous phase of the liposomes increased with decreasing pH. The effect of pH on the liposome aggregation in a solution qualitatively paralleled that found in the leakage behavior. PMID:10735463

Osanai, S; Nakamura, K

2000-05-01

408

Hyaluronic acid derivative-coated nanohybrid liposomes for cancer imaging and drug delivery.  

PubMed

Nanohybrid liposomes coated with amphiphilic hyaluronic acid-ceramide (HACE) was fabricated for targeted delivery of anticancer drug and in vivo cancer imaging. Nanohybrid liposomes including doxorubicin (DOX) and Magnevist, a contrast agent for magnetic resonance (MR) imaging, with 120-130nm mean diameter and a narrow size distribution were developed. DOX release from the developed formulation was improved at acidic pH (pH5.5 and 6.8) versus physiological pH (pH7.4). Cytotoxicity induced by the blank plain liposome was reduced by coating the outer surface of the nanohybrid liposome with HACE. Cellular uptake of DOX from the nanohybrid liposome was enhanced by HA and CD44 receptor interaction, versus the plain liposome. In vivo contrast-enhancing effects revealed that the nanohybrid liposome can be used as a tumor targeting MR imaging probe for cancer diagnosis. In a pharmacokinetic study in rats, in vivo clearance of DOX was decreased in the order DOX solution, plain liposome (F2), and nanohybrid liposome (F3), indicating prolonged circulation of the drug in the blood stream and improved therapeutic efficacy of the nanohybrid liposome (F3). Based on these findings, the nanohybrid liposomal system may be a useful candidate for real-time cancer diagnosis and therapy. PMID:24280260

Park, Ju-Hwan; Cho, Hyun-Jong; Yoon, Hong Yeol; Yoon, In-Soo; Ko, Seung-Hak; Shim, Jae-Seong; Cho, Jee-Hyun; Park, Jae Hyung; Kim, Kwangmeyung; Kwon, Ick Chan; Kim, Dae-Duk

2014-01-28

409

Effect of positively and negatively charged liposomes on skin permeation of drugs.  

PubMed

To clarify the effect of the surface charge of liposomes on percutaneous absorption, the permeation of liposomal drugs through rat skin was investigated in vitro and in vivo. Liposomes were prepared using egg yolk lecithin (EPC, phase transition temperature, -15 to -17 degrees C), cholesterol and dicetylphosphate (DP) or stearylamine (SA) (10:1:1, mol/mol). Also examined was the penetration behavior of positively and negatively charged liposomes, using a fluorescent probe (Nile Red). The in vitro penetration rate of melatonin (MT) entrapped in negatively charged liposomes was higher than that of positively charged ones (p<0.05). When the percutaneous absorption of ethosuximide (ES) encapsulated was estimated in vivo, the absorption of ES from negatively charged liposomes was slightly higher than that from positively charged liposomes. Additionally, the absorption of ES from both types of liposomes was superior to that from the lipid mixtures consisting of the same composition as the vesicles. The percutaneous absorption of betahistine (BH) from a gel formulation containing negatively charged liposomes of BH was much more than that from the formulation with positively charged ones, with 2-fold higher AUC (p<0.05). Histological studies revealed that the negatively charged liposomes diffused to the dermis and the lower portion of hair follicles through the stratum corneum and the follicles much faster than the positive vesicles at the initial time stage after application. Thus, the rapid penetration of negatively charged liposomes would contribute to the increased permeation of drugs through the skin. PMID:11378523

Ogiso, T; Yamaguchi, T; Iwaki, M; Tanino, T; Miyake, Y

2001-01-01

410

New approach on evaluation of liposome release property with electric impedance measuring method  

NASA Astrophysics Data System (ADS)

The purpose of this study is to develop a novel method for evaluation of the liposomes' release property by detecting the electric impedance change in the liposome solution. Liposomes encapsulating calcein (calcein-liposomes) and de-ionized water (white-liposomes) were prepared and ultrasound was employed as the stimulus in order to release the calcein from liposomes. The impedance change of calcein-liposomes in de-ionized water was measured before and after ultrasound treatment, as well as that of white-liposomes in de-ionized water and in calcein solutions for comparison. Besides, the release of calcein-liposome suspensions was evaluated simultaneously by spectrofluorometer. Results showed that the impedance of white-liposomes would change greatly when it was exposed to ultrasound and it was related to the total ion concentration of the sample. The release rate of calcein calculated with electric impedances showed a good agreement to that calculated with fluorescence intensities. It indicates that the electric impedance measuring method has high potential to estimate the release rate as the fluorescence analysis do, and might be used for non-fluorescent encapsulated liposomes which could not be evaluated by fluorescence method.

Chen, Guoming; Jiang, Zhongwei; Yoshimoto, Makato; Luo, Yafang; Wei, Yunlong

2007-12-01

411

Phospholipase A(2)-catalyzed membrane leakage studied by immobilized liposome chromatography with online fluorescent detection.  

PubMed

Unilamellar liposomes composed of phosphatidylcholine with an entrapped self-quenching fluorescent dye, calcein, were immobilized in chromatographic gel beads by avidin-biotin binding. Bee venom phospholipase A(2) (PLA(2)) was applied in a small amount onto the immobilized liposome column. The release of calcein from the immobilized liposomes resulting from the catalyzed hydrolysis of the phospholipids was detected online by immobilized liposome chromatography (ILC) using a flow fluorescent detector. The PLA(2)-catalyzed membrane leakage of the immobilized liposomes as studied with ILC was found to be affected by the gel pore size used for immobilization, by liposome size, and as expected by the concentration of calcium, but was unaffected by the flow rate of ILC. The largest PLA(2)-induced calcein release from the liposome column was detected on large unilamellar liposomes immobilized on TSK G6000PW or Sephacryl S-1000 gel in the presence of 1 mM Ca(2+) in the aqueous mobile phase. Comparison with the PLA(2)-catalyzed membrane leakage in free liposome suspensions, we conclude that the fluorescent leakage from liposomes hydrolyzed by PLA(2) can be rapidly and sensitively detected by ILC runs using large amount of immobilized liposomes with entrapped fluorescent dye. PMID:11399040

Liu, X Y; Nakamura, C; Yang, Q; Miyake, J

2001-06-15

412

Poly(amino acid)s: promising enzymatically degradable stealth coatings for liposomes.  

PubMed

Poly(amino acid)s (PAAs) were evaluated as coating polymers for long-circulating liposomes. The pharmacokinetics of PAA-coated liposomes were assessed in rats. Prolonged circulation times were obtained, comparable to those reported for poly(ethylene glycol) (PEG)-liposomes. Besides, the enzymatic degradability of PAAs was studied. PAAs - in free as well as liposome-associated form - are degradable by proteases, which is beneficial for reducing the risks of accumulation in vivo. Furthermore, complement activation by PAA-liposomes was evaluated in vitro and in vivo. Like other liposome types, they appear to activate the complement system. However, a role of endotoxin contamination of the PAA-liposome formulations used cannot be excluded in our complement activation studies. PMID:17145145

Romberg, Birgit; Metselaar, Josbert M; Baranyi, Lajos; Snel, Cor J; Bünger, Rolf; Hennink, Wim E; Szebeni, Janos; Storm, Gert

2007-03-01

413

Development of liposome-based mimics of superoxide dismutase and peroxidase based on the "LIPOzyme" concept.  

PubMed

An antioxidative liposome catalyst, LIPOzyme, that mimics both superoxide dismutase (SOD) and peroxidase (POD)-like activities has been developed by using liposomes modified with simple ligands (dodecanoyl-histidine, Dodec-His) and metal ions (Mn). The SOD-like activity is dependent on the stability of the ligand-metal complex on the liposome membrane, with the value being higher for the DPPC liposome and at a higher pH. The POD-like activity was found to be maximal in the case of DMPC liposome, in which the ligand-metal complex is inserted more deeply into the membrane. It was thus shown that liposome modified with simple ligands can exhibit different enzyme-like activities depending on the characteristics of the liposome membrane. PMID:20188129

Umakoshi, Hiroshi; Morimoto, Kengo; Yasuda, Naoto; Shimanouchi, Toshinori; Kuboi, Ryoichi

2010-05-01

414

Topical delivery of liposomally encapsulated interferon evaluated in a cutaneous herpes guinea pig model.  

PubMed Central

The topical delivery of liposomally encapsulated interferon was evaluated in the cutaneous herpes simplex virus guinea pig model. Application of liposomally entrapped interferon caused a reduction of lesion scores, whereas application of interferon formulated as a solution or as an emulsion was ineffective. The method of liposomal preparation rather than the lipid composition of the bilayers appeared to be the most important factor for reducing lesion scores. Only liposomes prepared by the dehydration-rehydration method were effective. This finding implied that the dehydration and subsequent rehydration of the liposomes facilitate partitioning of the interferon into liposomal bilayers, where the drug is positioned for transfer into the lipid compartment of the stratum corneum. Liposomes do not appear to function as permeation enhancers but seem to provide the needed physicochemical environment for transfer of interferon into the skin.

Weiner, N; Williams, N; Birch, G; Ramachandran, C; Shipman, C; Flynn, G

1989-01-01

415

Enhanced active targeting via cooperative binding of ligands on liposomes to target receptors.  

PubMed

To achieve effective active targeting in a drug delivery system, we previously developed dual-targeting (DT) liposomes decorated with both vascular endothelial growth factor receptor-1 (VEGFR-1)-targeted APRPG and CD13-targeted GNGRG peptide ligands for tumor neovessels, and observed the enhanced suppression of tumor growth in Colon26 NL-17 tumor-bearing mice by the treatment with the DT liposomes encapsulating doxorubicin. In this present study, we examined the binding characteristics of DT liposomes having a different couple of ligands, namely, APRPG and integrin ?v?3-targeted GRGDS peptides. These DT liposomes synergistically associated to stimulated human umbilical vein endothelial cells compared with single-targeting (ST) liposomes decorated with APRPG or GRGDS. The results of a surface plasmon resonance assay showed that ST liposomes modified with APRPG or GRGDS peptide selectively bound to immobilized VEGFR-1 or integrin ?v?3, respectively. DT liposomes showed a higher affinity for a mixture of VEGFR-1 and integrin ?v?3 compared with ST liposomes, suggesting the cooperative binding of these 2 kinds of ligand on the liposomal surface. In a biodistribution assay, the DT liposomes accumulated to a significantly greater extent in the tumors of Colon26 NL-17 tumor-bearing mice compared with other liposomes. Moreover, the intratumoral distribution of the liposomes examined by confocal microscopy suggested that the DT liposomes targeted not only angiogenic endothelial cells but also tumor cells due to GRGDS-decoration. These findings suggest that "dual-targeting" augmented the affinity of the liposomes for the target cells and would thus be useful for active-targeting drug delivery for cancer treatment. PMID:23840738

Sugiyama, Tomoki; Asai, Tomohiro; Nedachi, Yuki Murase; Katanasaka, Yasufumi; Shimizu, Kosuke; Maeda, Noriyuki; Oku, Naoto

2013-01-01

416

Composition and properties of complexes between spherical polycationic brushes and anionic liposomes.  

PubMed

A spherical polycationic brush (SPB) is made by graft-polymerizing a cationic monomer onto the surface of a 100 nm polystyrene bead. It is possible to adsorb anionic liposomes (40-60 nm diameter) onto the SPBs while maintaining the liposome integrity. The liposomes were constructed with phosphatidyl choline (PC) admixed with 0.05-0.4 mol fraction of an dianionic lipid, cardiolipin (CL(2-)). As shown by electrophoretic mobility measurements, SPB-to-liposome complexation leads to a conversion from the initial positive charge of the copolymer to a negative charge. The higher the CL(2-) content of the liposomes, the lower the concentration needed for charge neutralization. Dynamic light scattering (DLS) revealed that multicomplex aggregates are formed with a maximum size at the SPB/liposome charge-equivalence point. Experiments with fluorescent-labeled liposomes show that at low CL(2-) content about 80 liposomes are adsorbed per SPB. As the mole fraction of CL(2-) increases from 0.05 to 0.4, fewer liposomes adsorb owing to electrostatic repulsion among neighboring liposomes. The effect of added NaCl also depends upon the CL(2-) content. With 0.05 mol fraction CL(2-), the SPB/liposome complex dissociates into its components at 0.15 M NaCl. With a mole fraction of >0.1, complexes fail to dissociate even at 1.2 M NaCl. Additional information about the SPB/liposome morphology was obtained from cryo-TEM. For example, cryo-TEM data confirm liposome integrity upon complexation, a behavior that contrasts with the liposome destruction as found with adsorption to many other types of surfaces. PMID:23121151

Sybachin, Andrey V; Zaborova, Olga V; Ballauff, Matthias; Kesselman, Ellina; Schmidt, Judith; Talmon, Yeshayahu; Menger, Fredric M; Yaroslavov, Alexander A

2012-11-20

417

Preparation, characterization and properties of sterically stabilized paclitaxel-containing liposomes.  

PubMed

Paclitaxel (Taxol) is a diterpenoid isolated from Taxus brevifolia, approved by the FDA for the treatment of ovarian and breast cancers. Due to its low solubility in water, it is clinically administered dissolved in Cremophor EL, (polyethoxylated castor oil) and ethanol, which cause serious side effects. Inclusion of paclitaxel in liposomal formulations has proved to be a good approach to eliminating this vehicle and improving the drug's antitumor efficacy. We prepared different conventional and PEGylated liposomes containing paclitaxel and determined encapsulation efficiency, physical stability and drug leakage in human plasma. The best conventional liposome formulation was composed of ePC/PG 9:1, while for PEGylated liposomes the best composition was ePC/PG/CHOL/PEG(5000)-DPPE 9:1:2:0.7. PEGylated liposomes were found to be less stable during storage than the corresponding conventional liposomes and to have lower drug release in human plasma at 37 degrees C. In vitro cytotoxic activities were evaluated on HT-29 human colon adenocarcinoma and MeWo melanoma cell lines. After 2 and 48 h, conventional liposomes had the same cytotoxicity as free paclitaxel, while PEGylated liposomes were as active as free drug, only after 48 h. Pharmacokinetics and biodistribution were evaluated in Balb/c mice after i.v. injection of paclitaxel, formulated in Cremophor EL or in conventional or in PEGylated liposomes. Encapsulation of paclitaxel in conventional liposomes produced marked differences over the free drug pharmacokinetics. PEGylated liposomes were long-circulating liposomes, with an increased t(1/2) beta 48.6 h, against t(1/2) beta 9.27 h of conventional liposomes. Biodistribution studies showed a considerable decrease in drug uptake in MPS-containing organs (liver and spleen) at 0.5 and 3 h after injection with PEGylated compared to conventional liposomes. PMID:10640577

Crosasso, P; Ceruti, M; Brusa, P; Arpicco, S; Dosio, F; Cattel, L

2000-01-01

418

Preparation and pharmaceutical evaluation of liposomes entrapping salicylic acid/gamma-cyclodextrin conjugate.  

PubMed

To evaluate the potential use of a drug/cyclodextrin (CyD) conjugate for efficient entrapment in liposomes and prolonged residence of a drug in tissues, we synthesized a salicylic acid (SA) conjugate bound covalently with gamma-cyclodextrin (SA/gamma-CyD conjugate), a model drug/CyD conjugate, and then liposomes entrapping the conjugate (conjugate-in-liposome) were prepared by a freezing-thawing method. The chemical and physicochemical properties of the SA/gamma-CyD conjugate in solution and solid state were investigated and then the physicochemical properties of conjugate-in-liposome, in vitro cellular uptake/release and in vivo disposition of SA/gamma-CyD conjugate after intravenous administration of aqueous suspension containing conjugate-in-liposome in rats, were evaluated, comparing with those of the liposome-entrapped SA alone (SA-in-liposome) or the liposome-entrapped noncovalent SA/gamma-CyD complex (complex-in-liposome). As a result, it was found that the conjugate was amorphous powder and the release of SA from the conjugate in phosphate-buffered saline (PBS) was tolerated to chemical and enzymatic degradation. Meanwhile, the particle sizes and stability of these liposomes were almost identical, and the entrapment ratio of SA/gamma-CyD conjugate in liposomes was higher than those of SA alone and SA/gamma-CyD complex. The cellular uptake of these liposomes was almost equivalent, but the release of SA/gamma-CyD conjugate from RAW264.7 cells was markedly slower, compared with that of SA from cells following cellular uptake of the SA-in-liposome and complex-in-liposome. The disposition of SA or SA/gamma-CyD conjugate following intravenous administration of aqueous suspensions containing each liposome system in rats was comparable, but the residence time of the conjugate in tissues significantly prolonged, compared with that of the SA-in-liposome and complex-in-liposome systems. These results suggest the potential use of SA/gamma-CyD conjugate for efficient entrapment in liposomes as well as of liposomes containing SA/gamma-CyD conjugates for prolonged residence of drugs in tissues. PMID:16394544

Hagiwara, Yoshiyuki; Arima, Hidetoshi; Miyamoto, Yuji; Hirayama, Fumitoshi; Uekama, Kaneto

2006-01-01

419

Photo-induced electron transfer between dendritic zinc(II) phthalocyanine bearing carboxylic terminal groups and methyl viologen  

NASA Astrophysics Data System (ADS)

The intermolecular electron transfer between carboxylic dendritic zinc(II) phthalocyanine bearing carboxylic terminal groups(G1-ZnPc(COOH)8) and methyl viologens (MV2+) was studied by steady-state fluorescence and UV/Vis spectroscopy. The effect of different concentrations of MV2+ on intermolecular electron transfer was investigated. The results show that the fluorescence emission of this dendritic phthalocyanine could be greatly quenched with an increasing amount of MV2+ upon excitation at 610 nm. Our study suggests that this novel dendritic phthalocyanine is an effective new electron donor and transmission complex and could be used as a potential biosensor conjugated with suitable fluorescence quencher.

Wang, Yuhua; Chen, Jiangxu; Huang, Lishan; Xie, Shusen; Yang, Hongqin; Peng, Yiru

2012-12-01

420

Photophysical properties of a new water soluble tetra thiamine substituted zinc phthalocyanine conjugated to gold nanorods of different aspect ratios.  

PubMed

A water soluble zinc phthalocyanine substituted with thiamine is reported in this work. The aggregation of this compound in aqueous solutions causes quenching of the fluorescence quantum yields. Gold nanospheres and nanorods were linked to the phthalocyanine. X-ray photoelectron spectroscopy showed that both the amine and the sulphur groups on the thiamine substituent of the zinc phthalocyanine were involved in the linking to gold nanoparticles. The Pc showed an increase in the fluorescence quantum yields in the presence of the nanoparticles. The singlet oxygen quantum yield increased when the Pc was conjugated to the nanoparticles and even higher for larger aspect ratio gold nanorods. PMID:24671409

Mthethwa, Thandekile; Antunes, Edith; Nyokong, Tebello

2014-05-13

421

Porphyrin-phospholipid liposomes permeabilized by near-infrared light  

PubMed Central

The delivery of therapeutic compounds to target tissues is a central challenge in treating disease. Externally controlled drug release systems hold potential to selectively enhance localized delivery. Here we describe liposomes doped with porphyrin–phospholipid that are permeabilized directly by near-infrared light. Molecular dynamics simulations identified a novel light-absorbing monomer esterified from clinically approved components predicted and experimentally demonstrated to give rise to a more stable porphyrin bilayer. Light-induced membrane permeabilization is enabled with liposomal inclusion of 10 molar % porphyrin–phospholipid and occurs in the absence of bulk or nanoscale heating. Liposomes reseal following laser exposure and permeability is modulated by varying porphyrin–phospholipid doping, irradiation intensity or irradiation duration. Porphyrin–phospholipid liposomes demonstrate spatial control of release of entrapped gentamicin and temporal control of release of entrapped fluorophores following intratumoral injection. Following systemic administration, laser irradiation enhances deposition of actively loaded doxorubicin in mouse xenografts, enabling an effective single-treatment antitumour therapy.

Carter, Kevin A.; Shao, Shuai; Hoopes, Matthew I.; Luo, Dandan; Ahsan, Bilal; Grigoryants, Vladimir M.; Song, Wentao; Huang, Haoyuan; Zhang, Guojian; Pandey, Ravindra K.; Geng, Jumin; Pfeifer, Blaine A.; Scholes, Charles P.; Ortega, Joaquin; Karttunen, Mikko; Lovell, Jonathan F.

2014-01-01

422

Liposomal bupivacaine: a review of a new bupivacaine formulation.  

PubMed

Many attempts have been made to increase the duration of local anesthetic action. One avenue of investigation has focused on encapsulating local anesthetics within carrier molecules to increase their residence time at the site of action. This article aims to review the literature surrounding the recently approved formulation of bupivacaine, which consists of bupivacaine loaded in multivesicular liposomes. This preparation increases the duration of local anesthetic action by slow release from the liposome and delays the peak plasma concentration when compared to plain bupivacaine administration. Liposomal bupivacaine has been approved by the US Food and Drug Administration for local infiltration for pain relief after bunionectomy and hemorrhoidectomy. Studies have shown it to be an effective tool for postoperative pain relief with opioid sparing effects and it has also been found to have an acceptable adverse effect profile. Its kinetics are favorable even in patients with moderate hepatic impairment, and it has been found not to delay wound healing after orthopedic surgery. More studies are needed to establish its safety and efficacy for use via intrathecal, epidural, or perineural routes. In conclusion, liposomal bupivacaine is effective for treating postoperative pain when used via local infiltration when compared to placebo with a prolonged duration of action, predictable kinetics, and an acceptable side effect profile. However, more adequately powered trials are needed to establish its superiority over plain bupivacaine. PMID:23049275

Chahar, Praveen; Cummings, Kenneth C

2012-01-01

423

Liposomal bupivacaine: a review of a new bupivacaine formulation  

PubMed Central

Many attempts have been made to increase the duration of local anesthetic action. One avenue of investigation has focused on encapsulating local anesthetics within carrier molecules to increase their residence time at the site of action. This article aims to review the literature surrounding the recently approved formulation of bupivacaine, which consists of bupivacaine loaded in multivesicular liposomes. This preparation increases the duration of local anesthetic action by slow release from the liposome and delays the peak plasma concentration when compared to plain bupivacaine administration. Liposomal bupivacaine has been approved by the US Food and Drug Administration for local infiltration for pain relief after bunionectomy and hemorrhoidectomy. Studies have shown it to be an effective tool for postoperative pain relief with opioid sparing effects and it has also been found to have an acceptable adverse effect profile. Its kinetics are favorable even in patients with moderate hepatic impairment, and it has been found not to delay wound healing after orthopedic surgery. More studies are needed to establish its safety and efficacy for use via intrathecal, epidural, or perineural routes. In conclusion, liposomal bupivacaine is effective for treating postoperative pain when used via local infiltration when compared to placebo with a prolonged duration of action, predictable kinetics, and an acceptable side effect profile. However, more adequately powered trials are needed to establish its superiority over plain bupivacaine.

Chahar, Praveen; Cummings, Kenneth C

2012-01-01

424

Complement-Dependent Immune Damage to Liposomes Containing Gangliosides.  

National Technical Information Service (NTIS)

Rabbit antiserum against mixed beef brain gangliosides served as an excellent source of antibodies to gangliosides Gm1, Gm3, Gd1a, Gd1b, and GT1b. Immune potency of antiserum was determined by complement-dependent damage to liposomes containing gangliosid...

S. Shichijo G. Toffano C. R. Alving

1985-01-01

425

Topical liposome delivery of molecules to hair follicles in mice  

Microsoft Academic Search

The hair cycle consisting of growing and resting phases, is subject to widespread disease such as androgenic alopecia or loss of pigment which are in need of effective, targeted therapeutics. In order to develop a hair-follicle delivery system we demonstrate here that phosphatidylcholine liposomes entrapping either the fluorescent dye calcein or the pigment melanin can deliver these molecules into the

Lingna Li; Robert M. Hoffman

1997-01-01

426

Porphyrin–phospholipid liposomes permeabilized by near-infrared light  

NASA Astrophysics Data System (ADS)

The delivery of therapeutic compounds to target tissues is a central challenge in treating disease. Externally controlled drug release systems hold potential to selectively enhance localized delivery. Here we describe liposomes doped with porphyrin–phospholipid that are permeabilized directly by near-infrared light. Molecular dynamics simulations identified a novel light-absorbing monomer esterified from clinically approved components predicted and experimentally demonstrated to give rise to a more stable porphyrin bilayer. Light-induced membrane permeabilization is enabled with liposomal inclusion of 10 molar % porphyrin–phospholipid and occurs in the absence of bulk or nanoscale heating. Liposomes reseal following laser exposure and permeability is modulated by varying porphyrin–phospholipid doping, irradiation intensity or irradiation duration. Porphyrin–phospholipid liposomes demonstrate spatial control of release of entrapped gentamicin and temporal control of release of entrapped fluorophores following intratumoral injection. Following systemic administration, laser irradiation enhances deposition of actively loaded doxorubicin in mouse xenografts, enabling an effective single-treatment antitumour therapy.

Carter, Kevin A.; Shao, Shuai; Hoopes, Matthew I.; Luo, Dandan; Ahsan, Bilal; Grigoryants, Vladimir M.; Song, Wentao; Huang, Haoyuan; Zhang, Guojian; Pandey, Ravindra K.; Geng, Jumin; Pfeifer, Blaine A.; Scholes, Charles P.; Ortega, Joaquin; Karttunen, Mikko; Lovell, Jonathan F.

2014-04-01

427

Temperature-sensitive liposomes for doxorubicin delivery under MRI guidance.  

PubMed

Local drug delivery of doxorubicin holds promise to improve the therapeutic efficacy and to reduce toxicity profiles. Here, we investigated the release of doxorubicin and [Gd(HPDO3A)(H(2)O)] from different temperature-sensitive liposomes for applications in temperature-induced drug delivery under magnetic resonance image guidance. In particular, two temperature-sensitive systems composed of DPPC:MPPC:DPPE-PEG2000 (low temperature-sensitive liposomes, LTSL) and DPPC:HSPC:cholesterol:DPPE-PEG2000 (traditional temperature-sensitive liposomes, TTSL) were investigated. The co-encapsulation of [Gd(HPDO3A)(H(2)O)], a clinically approved MRI contrast agent, did not influence the encapsulation and release of doxorubicin. The LTSL system showed a higher leakage of doxorubicin at 37 degrees C, but a faster release of doxorubicin at 42 degrees C compared to the TTSL system. Furthermore, the rapid release of both doxorubicin and the MRI contrast agent from the liposomes occurred near the melting phase transition temperature, making it possible to image the release of doxorubicin using MRI. PMID:19969035

de Smet, Mariska; Langereis, Sander; van den Bosch, Sandra; Grüll, Holger

2010-04-01

428

Porphyrin-phospholipid liposomes permeabilized by near-infrared light.  

PubMed

The delivery of therapeutic compounds to target tissues is a central challenge in treating disease. Externally controlled drug release systems hold potential to selectively enhance localized delivery. Here we describe liposomes doped with porphyrin-phospholipid that are permeabilized directly by near-infrared light. Molecular dynamics simulations identified a novel light-absorbing monomer esterified from clinically approved components predicted and experimentally demonstrated to give rise to a more stable porphyrin bilayer. Light-induced membrane permeabilization is enabled with liposomal inclusion of 10 molar % porphyrin-phospholipid and occurs in the absence of bulk or nanoscale heating. Liposomes reseal following laser exposure and permeability is modulated by varying porphyrin-phospholipid doping, irradiation intensity or irradiation duration. Porphyrin-phospholipid liposomes demonstrate spatial control of release of entrapped gentamicin and temporal control of release of entrapped fluorophores following intratumoral injection. Following systemic administration, laser irradiation enhances deposition of actively loaded doxorubicin in mouse xenografts, enabling an effective single-treatment antitumour therapy. PMID:24699423

Carter, Kevin A; Shao, Shuai; Hoopes, Matthew I; Luo, Dandan; Ahsan, Bilal; Grigoryants, Vladimir M; Song, Wentao; Huang, Haoyuan; Zhang, Guojian; Pandey, Ravindra K; Geng, Jumin; Pfeifer, Blaine A; Scholes, Charles P; Ortega, Joaquin; Karttunen, Mikko; Lovell, Jonathan F

2014-01-01

429

Development of a liposomal nanodelivery system for nevirapine  

Microsoft Academic Search

BACKGROUND: The treatment of AIDS remains a serious challenge owing to high genetic variation of Human Immunodeficiency Virus type 1 (HIV-1). The use of different antiretroviral drugs (ARV) is significantly limited by severe side-effects that further compromise the quality of life of the AIDS patient. In the present study, we have evaluated a liposome system for the delivery of nevirapine,

Lakshmi N Ramana; Swaminathan Sethuraman; Udaykumar Ranga; Uma M Krishnan

2010-01-01

430

Radiation induced oxidative damage modification by cholesterol in liposomal membrane  

NASA Astrophysics Data System (ADS)

Ionizing radiation induced structural and chemical alterations in egg lecithin liposomal membrane have been studied by measurements of lipid peroxides, conjugated diene and fluorescence polarization. Predominantly unilamellar phospholipid vesicles prepared by sonication procedure were subjected to radiation doses of ?-rays from Co-60 in aerated, buffered aqueous suspensions. The oxidative damage in irradiated lipid molecules of liposomes has been determined spectrophotometrically by diene conjugate formation and thiobarbituric acid reactive (TBAR) method as a function of radiation dose. A correlation was found between the radiation dose applied (0.1-1 kGy) and the consequent lipid oxidation. The damage produced in irradiated liposomal membrane was measured by 1,6-diphenyl-1,3,5-hexatriene (DPH) fluorescence decay and polarization. The observed decrease in DPH fluorescence and increase in polarization was found dependent on the radiation dose suggesting alterations in rigidity or organizational order in phospholipid bilayer after irradiation. Furthermore, irradiated liposome vesicles composed of cholesterol showed marked reduction in observed radiation mediated peroxide formation and significantly affected the DPH fluorescence parameters. The magnitude of these modifying effects were found dependent on the mole fraction of cholesterol. It is concluded that modulation of structural order in unilamellar vesicle membrane by variations in basic molecular components controlled the magnitude of lipid peroxidation and diene conjugate formation. These observations contribute to our understanding of mechanism of radical reaction mediated damage caused by ionizing radiation in phospholipid membrane.

Pandey, B. N.; Mishra, K. P.

1999-05-01

431