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Sample records for zn-porphyrin tweezer host-guest

  1. The Design of Molecular Hosts, Guests, and Their Complexes.

    ERIC Educational Resources Information Center

    Cram, Donald J.

    1988-01-01

    Describes the origins, definitions, tools, and principles of host-guest chemistry. Gives examples of chiral recognition in complexation, of partial transacylase mimics, of caviplexes, and of a synthetic molecular cell. (Author/RT)

  2. Hybrid host-guest complexes: directing the supramolecular structure through secondary host-guest interactions.

    PubMed

    Streb, Carsten; McGlone, Thomas; Brücher, Oliver; Long, De-Liang; Cronin, Leroy

    2008-01-01

    A set of four hybrid host-guest complexes based on the inorganic crown ether analogue [H12W36O120]12- ({W36}) have been isolated and characterised. The cluster anion features a central rigid binding site made up of six terminal oxygen ligands and this motif allows the selective binding of a range of alkali and alkali-earth-metal cations. Here, the binding site was utilised to functionalise the metal oxide-based cavity by complexing a range of protonated primary amines within the recognition site. As a result, a set of four hybrid organic-inorganic host-guest complexes were obtained whereby the interactions are highly directed specifically within this cavity. The guest cations in these molecular assemblies range from the aromatic 2-phenethylamine (1) and 4-phenylbutylamine (2) to the bifunctional aromatic p-xylylene diamine (3) and the aliphatic, bifunctional 1,6-diaminohexane (4). Compounds 1-4 were structurally characterised by single-crystal X-ray diffraction, elemental analysis, flame atomic absorption spectroscopy, FTIR and bond valence sum calculations. This comparative study focuses on the supramolecular effects of the amine guest cations and investigates their structure-directing effects on the framework arrangement arising by locking the protonated amines within the cavity of the {W36} cluster. It was shown that parts of the organic guest cation protrude from the central binding cavity and the nature of this protruding organic "tail" directs the solid-state arrangement of compounds 1-4. Guest cations with a hydrophobic phenyl tail result in an antiparallel assembly of {W36} complexes arranged in a series of pillared layers. As a consequence, no direct supramolecular interactions between {W36} clusters are observed. In contrast, bifunctional guest cations with a secondary amino binding site act as molecular connectors and directly link two cluster units thus locking the supramolecular assembly in a tilted arrangement. This direct linking of {W36} anions

  3. Reversibly tunable upconversion luminescence by host-guest chemistry.

    PubMed

    Taniguchi, Takaaki; Murakami, Tomoaki; Funatsu, Asami; Hatakeyama, Kazuto; Koinuma, Michio; Matsumoto, Yasumichi

    2014-09-01

    Tuning upconversion (UPC) luminescence using external stimuli and fields, as well as chemical reactions, is expected to lead to novel and efficient optical sensors. Herein, highly tunable UPC luminescence was achieved through a host-guest chemistry approach. Specifically, interlayer ion exchange reactions reversibly tuned the emission intensity and green-red color of Er/Yb-codoped A2La2Ti3O10 layered perovskite, where A corresponds to proton and alkali metal ions, enabling the visualization of host-guest interactions and reactions. PMID:25122035

  4. Pillar[6]arene-based photoresponsive host-guest complexation.

    PubMed

    Yu, Guocan; Han, Chengyou; Zhang, Zibin; Chen, Jianzhuang; Yan, Xuzhou; Zheng, Bo; Liu, Shiyong; Huang, Feihe

    2012-05-23

    The trans form of an azobenzene-containing guest can complex with a pillar[6]arene, while it cannot complex with pillar[5]arenes due to the different cavity sizes of the pillar[6]arene and the pillar[5]arenes. The spontaneous aggregation of its host-guest complex with the pillar[6]arene can be reversibly photocontrolled by irradiation with UV and visible light, leading to a switch between irregular aggregates and vesicle-like aggregates. This new pillar[6]arene-based photoresponsive host-guest recognition motif can work in organic solvents and is a good supplement to the existing widely used cyclodextrin/azobenzene recognition motif.

  5. Host-guest binding motifs based on hyperbranched polymers.

    PubMed

    Mou, Quanbing; Ma, Yuan; Jin, Xin; Yan, Deyue; Zhu, Xinyuan

    2016-10-11

    Host-guest chemistry involves the binding of a substrate molecule (guest) to a receptor molecule (host). Various molecules, including crown ethers, cryptands, cyclophanes, calixarenes, cyclodextrins, and so on, have been used as molecular hosts. However, only limited small molecules or simple ions can be encapsulated in these hosts. Fortunately, as a class of unique host molecules, hyperbranched polymers (HBPs) can bind to numerous guests through topological entrapment, electrostatic bonding, hydrogen bonding or hydrophobic interactions in the core, at the branching points or at the periphery. Hence, hyperbranched polymeric hosts have received increasing attention in the past few decades because of their specific and unique properties. This review briefly summarizes these unique properties related to HBPs serving as hosts. In addition, HBP-based host-guest systems will be classified according to the types of guests encapsulated. Besides, the corresponding applications will be presented as well. We hope to motivate an increased understanding of molecular recognition in HBPs, and further facilitate the optimization of future host-guest systems. PMID:27464846

  6. Host-guest binding motifs based on hyperbranched polymers.

    PubMed

    Mou, Quanbing; Ma, Yuan; Jin, Xin; Yan, Deyue; Zhu, Xinyuan

    2016-10-11

    Host-guest chemistry involves the binding of a substrate molecule (guest) to a receptor molecule (host). Various molecules, including crown ethers, cryptands, cyclophanes, calixarenes, cyclodextrins, and so on, have been used as molecular hosts. However, only limited small molecules or simple ions can be encapsulated in these hosts. Fortunately, as a class of unique host molecules, hyperbranched polymers (HBPs) can bind to numerous guests through topological entrapment, electrostatic bonding, hydrogen bonding or hydrophobic interactions in the core, at the branching points or at the periphery. Hence, hyperbranched polymeric hosts have received increasing attention in the past few decades because of their specific and unique properties. This review briefly summarizes these unique properties related to HBPs serving as hosts. In addition, HBP-based host-guest systems will be classified according to the types of guests encapsulated. Besides, the corresponding applications will be presented as well. We hope to motivate an increased understanding of molecular recognition in HBPs, and further facilitate the optimization of future host-guest systems.

  7. Tunable Nanosupramolecular Aggregates Mediated by Host-Guest Complexation.

    PubMed

    Zhang, Wen; Zhang, Ying-Ming; Li, Sheng-Hua; Cui, Yong-Liang; Yu, Jie; Liu, Yu

    2016-09-12

    Nanosupramolecular assemblies with controlled topological features have inventive applications in fundamental studies and material manufacturing. Herein, a variety of morphologically interesting aggregates have been constructed using the supramolecular modulation with bipyridinium-modified diphenylalanine derivative (BP-FF). Benefiting from the high binding affinity of bipyridinium group with four different macrocyclic receptors, namely cucurbit[7]uril, cucurbit[8]uril, pillar[5]arene, and tetrasulfonated crown ether, we have succeeded in tuning the topological aggregates of BP-FF from fine nanofibers to nanorods, octahedron-like nanostructure, helical nanowires, and rectangular nanosheets without any tedious chemical modification. This supramolecular approach may provide us a powerful method to construct well-defined nanostructures with different morphologies that can be conveniently controlled by facile host-guest interactions. PMID:27527684

  8. An order-disorder ferroelectric host-guest inclusion compound.

    PubMed

    Zhang, Yi; Ye, Heng-Yun; Fu, Da-Wei; Xiong, Ren-Gen

    2014-02-17

    The host-guest complex [(DIPA)([18]crown-6)](ClO4) (1; DIPA=2,6-diisopropylanilinium) was constructed and found to undergo a sequence of phase transitions (Ibam-Pbcn-Pna21) at T1=278 K and T2=132 K, respectively. Systematic characterizations, such as differential scanning calorimetry, heat capacity, temperature-dependent dielectric constant, and P-E hysteresis loop, reveal that the centrosymmetric-to-polar phase transition at T2 is a paraelectric-to-ferroelectric transition. The symmetry breaking was also confirmed by temperature-dependent second-harmonic generation effect and X-ray powder diffraction. The ferroelectric mechanism is attributable to the linear motion of the perchlorate counterions accompanied by the order-disorder transition of the [18]crown-6 molecules and the anions.

  9. Friction and adhesion mediated by supramolecular host-guest complexes.

    PubMed

    Guerra, Roberto; Benassi, Andrea; Vanossi, Andrea; Ma, Ming; Urbakh, Michael

    2016-04-01

    The adhesive and frictional response of an AFM tip connected to a substrate through supramolecular host-guest complexes is investigated by dynamic Monte Carlo simulations. Here, the variation of the pull-off force with the unloading rate recently observed in experiments is unraveled by evidencing simultaneous (progressive) breaking of the bonds at fast (slow) rates. The model reveals the origin of the observed plateaus in the retraction force as a function of the tip-surface distance, showing that they result from the tip geometrical features. In lateral sliding, the model exhibits a wide range of dynamic behaviors ranging from smooth sliding to stick-slip at different velocities, with the average friction force determined by the characteristic formation/rupture rates of the complexes. In particular, it is shown that for some molecular complexes friction can become almost constant over a wide range of velocities. Also, we show the possibility of exploiting the ageing effect through slide-hold-slide experiments, in order to infer the characteristic formation rate. Finally, our model predicts a novel "anti-ageing" effect which is characterized by a decrease of the static friction force with the hold time. Such an effect is explained in terms of enhancement of adhesion during sliding, especially observed at high driving velocities. PMID:26975343

  10. Interfacial assembly of dendritic microcapsules with host-guest chemistry

    NASA Astrophysics Data System (ADS)

    Zheng, Yu; Yu, Ziyi; Parker, Richard M.; Wu, Yuchao; Abell, Chris; Scherman, Oren A.

    2014-12-01

    The self-assembly of nanoscale materials to form hierarchically ordered structures promises new opportunities in drug delivery, as well as magnetic materials and devices. Herein, we report a simple means to promote the self-assembly of two polymers with functional groups at a water-chloroform interface using microfluidic technology. Two polymeric layers can be assembled and disassembled at the droplet interface using the efficiency of cucurbit[8]uril (CB[8]) host-guest supramolecular chemistry. The microcapsules produced are extremely monodisperse in size and can encapsulate target molecules in a robust, well-defined manner. In addition, we exploit a dendritic copolymer architecture to trap a small hydrophilic molecule in the microcapsule skin as cargo. This demonstrates not only the ability to encapsulate small molecules but also the ability to orthogonally store both hydrophilic and hydrophobic cargos within a single microcapsule. The interfacially assembled supramolecular microcapsules can benefit from the diversity of polymeric materials, allowing for fine control over the microcapsule properties.

  11. Supramolecular Recognition Forces: An Examination of Weak Metal-Metal Interactions in Host-Guest Formation

    SciTech Connect

    Crowley, James D.; Steele, Ian M.; Bosnich, B.

    2008-10-03

    Molecular receptors consisting of two parallel-disposed terpy-M-Cl units (M = Pd{sup 2+}, Pt{sup 2+}) are used to form host-guest adducts with aromatic molecules and with neutral square-planar Pt{sup 2+} complexes. Host-guest formation is controlled by several factors including {pi}-{pi} interactions and, in some cases, weak Pt-Pt interactions between the host and the guest. This latter interaction was examined by comparing the host-guest stability of adducts formed by isoelectronic Pt{sup 2+} and Au{sup 3+} complexes with the Pt{sup 2+} receptor. Consistently, the former is more stable.

  12. A new topological parameter for monitoring subtle aggregation events in host-guest inclusion processes

    NASA Astrophysics Data System (ADS)

    Novato, Willian T. G.; De Almeida, Wagner B.; Dos Santos, Hélio F.

    2012-02-01

    Supramolecular complexes with cyclodextrin (CD) have been the subject of considerable research in the material and life sciences. The dynamics of systems are difficult to characterise, therefore, knowledge of the molecular features governing the host-guest equilibrium might aid in the design and practical application of the resulting inclusion complexes. In this Letter, we present a new topological parameter based on simple trigonometric considerations to be used to monitor subtle host-guest inclusion events along the molecular dynamics trajectory. The new topological descriptor, called vector-μ, was applied to amphetamine@α/β-CD inclusion complexes, providing interesting insights on the host-guest equilibrium.

  13. Mechanism of host-guest complexation by cucurbituril.

    PubMed

    Márquez, César; Hudgins, Robert R; Nau, Werner M

    2004-05-12

    The factors affecting host-guest complexation between the molecular container compound cucurbit[6]uril (CB6) and various guests in aqueous solution are studied, and a detailed complexation mechanism in the presence of cations is derived. The formation of the supramolecular complex is studied in detail for cyclohexylmethylammonium ion as guest. The kinetics and thermodynamics of complexation is monitored by NMR as a function of temperature, salt concentration, and cation size. The binding constants and the ingression rate constants decrease with increasing salt concentration and cation-binding constant, in agreement with a competitive binding of the ammonium site of the guest and the metal cation with the ureido carbonyl portals of CB6. Studies as a function of guest size indicate that the effective container volume of the CB6 cavity is approximately 105 A(3). It is suggested that larger guests are excluded for two reasons: a high activation barrier for ingression imposed by the tight CB6 portals and a destabilization of the complex due to steric repulsion inside. For example, in the case of the nearly spherical azoalkane homologues 2,3-diazabicyclo[2.2.1]hept-2-ene (DBH, volume ca. 96 A(3)) and 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO, volume ca. 110 A(3)), the former forms the CB6 complex promptly with a sizable binding constant (1300 M(-1)), while the latter does not form a complex even after several months at optimized complexation conditions. Molecular mechanics calculations are performed for several CB6/guest complexes. A qualitative agreement is found between experimental and calculated activation energies for ingression as a function of both guest size and state of protonation. The potential role of constrictive binding by CB6 is discussed.

  14. A semiconducting organic radical cationic host-guest complex.

    PubMed

    Fahrenbach, Albert C; Sampath, Srinivasan; Late, Dattatray J; Barnes, Jonathan C; Kleinman, Samuel L; Valley, Nicholas; Hartlieb, Karel J; Liu, Zhichang; Dravid, Vinayak P; Schatz, George C; Van Duyne, Richard P; Stoddart, J Fraser

    2012-11-27

    The self-assembly and solid-state semiconducting properties of single crystals of a trisradical tricationic complex composed of the diradical dicationic cyclobis(paraquat-p-phenylene) (CBPQT(2(•+))) ring and methyl viologen radical cation (MV(•+)) are reported. An organic field effect transistor incorporating single crystals of the CBPQT(2(•+))⊂MV(•+) complex was constructed using lithographic techniques on a silicon substrate and shown to exhibit p-type semiconductivity with a mobility of 0.05 cm(2) V(-1) s(-1). The morphology of the crystals on the silicon substrate was characterized using scanning electron microscopy which revealed that the complexes self-assemble into "molecular wires" observable by the naked-eye as millimeter long crystalline needles. The nature of the recognition processes driving this self-assembly, radical-radical interactions between bipyridinium radical cations (BIPY(•+)), was further investigated by resonance Raman spectroscopy in conjunction with theoretical investigations of the vibrational modes, and was supported by X-ray structural analyses of the complex and its free components in both their radical cationic and dicationic redox states. These spectroscopic investigations demonstrate that the bond order of the BIPY(•+) radical cationic units of host and guest components is not changed upon complexation, an observation which relates to its conductivity in the solid-state. We envision the modularity inherent in this kind of host-guest complexation could be harnessed to construct a library of custom-made electronic organic materials tailored to fit the specific needs of a given electronic application.

  15. Supramolecular chemistry at interfaces: host-guest interactions for fabricating multifunctional biointerfaces.

    PubMed

    Yang, Hui; Yuan, Bin; Zhang, Xi; Scherman, Oren A

    2014-07-15

    CONSPECTUS: Host-guest chemistry can greatly improve the selectivity of biomolecule-ligand binding on account of recognition-directed interactions. In addition, functional structures and the actuation of supramolecular assemblies in molecular systems can be controlled efficiently through various host-guest chemistry. Together, these highly selective, strong yet dynamic interactions can be exploited as an alternative methodology for applications in the field of programmable and controllable engineering of supramolecular soft materials through the reversible binding between complementary components. Many processes in living systems such as biotransformation, transportation of matter, and energy transduction begin with interfacial molecular recognition, which is greatly influenced by various external stimuli at biointerfaces. Detailed investigations about the molecular recognition at interfaces can result in a better understanding of life science, and further guide us in developing new biomaterials and medicines. In order to mimic complicated molecular-recognition systems observed in nature that adapt to changes in their environment, combining host-guest chemistry and surface science is critical for fabricating the next generation of multifunctional biointerfaces with efficient stimuli-responsiveness and good biocompatibility. In this Account, we will summarize some recent progress on multifunctional stimuli-responsive biointerfaces and biosurfaces fabricated by cyclodextrin- or cucurbituril-based host-guest chemistry and highlight their potential applications including drug delivery, bioelectrocatalysis, and reversible adsorption and resistance of peptides, proteins, and cells. In addition, these biointerfaces and biosurfaces demonstrate efficient response toward various external stimuli, such as UV light, pH, redox chemistry, and competitive guests. All of these external stimuli can aid in mimicking the biological stimuli evident in complex biological environments

  16. Supramolecular polymer assembly in aqueous solution arising from cyclodextrin host-guest complexation.

    PubMed

    Wang, Jie; Qiu, Zhiqiang; Wang, Yiming; Li, Li; Guo, Xuhong; Pham, Duc-Truc; Lincoln, Stephen F; Prud'homme, Robert K

    2016-01-01

    The employment of cyclodextrin host-guest complexation to construct supramolecular assemblies with an emphasis on polymer networks is reviewed. The main driving force for this supramolecular assembly is host-guest complexation between cyclodextrin hosts and guest groups either of which may be discrete molecular species or substituents on a polymer backbone. The effects of such complexation on properties at the molecular and macroscopic levels are discussed. It is shown that cyclodextrin complexation may be used to design functional polymer materials with tailorable properties, especially for photo-, pH-, thermo- and redox-responsiveness and self-healing. PMID:26877808

  17. Supramolecular chemistry at interfaces: host-guest interactions for fabricating multifunctional biointerfaces.

    PubMed

    Yang, Hui; Yuan, Bin; Zhang, Xi; Scherman, Oren A

    2014-07-15

    CONSPECTUS: Host-guest chemistry can greatly improve the selectivity of biomolecule-ligand binding on account of recognition-directed interactions. In addition, functional structures and the actuation of supramolecular assemblies in molecular systems can be controlled efficiently through various host-guest chemistry. Together, these highly selective, strong yet dynamic interactions can be exploited as an alternative methodology for applications in the field of programmable and controllable engineering of supramolecular soft materials through the reversible binding between complementary components. Many processes in living systems such as biotransformation, transportation of matter, and energy transduction begin with interfacial molecular recognition, which is greatly influenced by various external stimuli at biointerfaces. Detailed investigations about the molecular recognition at interfaces can result in a better understanding of life science, and further guide us in developing new biomaterials and medicines. In order to mimic complicated molecular-recognition systems observed in nature that adapt to changes in their environment, combining host-guest chemistry and surface science is critical for fabricating the next generation of multifunctional biointerfaces with efficient stimuli-responsiveness and good biocompatibility. In this Account, we will summarize some recent progress on multifunctional stimuli-responsive biointerfaces and biosurfaces fabricated by cyclodextrin- or cucurbituril-based host-guest chemistry and highlight their potential applications including drug delivery, bioelectrocatalysis, and reversible adsorption and resistance of peptides, proteins, and cells. In addition, these biointerfaces and biosurfaces demonstrate efficient response toward various external stimuli, such as UV light, pH, redox chemistry, and competitive guests. All of these external stimuli can aid in mimicking the biological stimuli evident in complex biological environments

  18. An efficient multiple healing conductive composite via host-guest inclusion.

    PubMed

    Zhang, Da-Li; Ju, Xin; Li, Luo-Hao; Kang, Yang; Gong, Xiao-Lei; Li, Bang-Jing; Zhang, Sheng

    2015-04-14

    A self-healable conductive composite is developed by combining the small molecules and nanotubes through host-guest interactions. This material shows uniform conductivity, microwave absorption and humidity sensing properties, and can be rapidly healed to over 90% electrical and mechanical properties with the aid of water multiple times. In addition, the produced material is also remouldable and recyclable. PMID:25761433

  19. Supramolecular Chemistry: Induced Circular Dichroism to Study Host-Guest Geometry

    ERIC Educational Resources Information Center

    Mendicuti, Francisco; Gonzalez-Alvarez, Maria Jose

    2010-01-01

    In this laboratory experiment, students obtain information about the structure of a host-guest complex from the interpretation of circular dichroism measurements. The value and sign of the induced circular dichroism (ICD) on an achiral chromophore guest when it complexes with a cyclodextrin can be related to the guest penetration and its…

  20. A hyperbranched supramolecular polymer constructed by orthogonal triple hydrogen bonding and host-guest interactions.

    PubMed

    Gu, Ruirui; Yao, Jian; Fu, Xin; Zhou, Wei; Qu, Da-Hui

    2015-03-28

    A hyperbranched supramolecular polymer has been constructed through orthogonal self-crosslinking by two classical binding interactions: triple hydrogen bonding interaction between a three-arm melamine derivative and DB24C8-containing bisimide and host-guest interaction between DB24C8 crown ether and ditopic dibenzyl ammonium moieties. PMID:25421931

  1. Synthesis, optical and electrochemical properties of Zn-porphyrin for dye sensitized solar cell applications

    NASA Astrophysics Data System (ADS)

    Kotteswaran, S.; Pandian, M. Senthil; Ramasamy, P.

    2016-05-01

    Zn-Porphyrin dye has been synthesized by the reaction between aldehydes and pyrrole. The dye structure was confirmed by 1H NMR, 13C NMR spectrum. The functional group of the dye molecule was confirmed by FTIR spectrum. The UV-Vis-NIR absorption spectrum of Zn-Porphyrin in DMF solution was recorded in spectrophotometer. The UV-Vis NIR spectrum of dye exhibits a strong Soret band and Q-band. Cyclic Voltammograms were obtained with three electrode systems: Pt as counter electrode, saturated calomel used as a reference electrode and glassy carbon as working electrode at a scan rate of 100 mV/s. The curves recorded the oxidation of 0.5 mM compound Zn-Porphyrin in a dichloromethane solution containing 0.1M TBAP as supporting electrolyte, reveal two successive quasi reversible redox couples with the first anodic and cathodic peak potentials of -0.2 V and -1 V. The second anodic and cathodic peak potentials are 0.82 V and 0.01 V respectively.

  2. Determination of association constant of host-guest supramolecular complex (molecular recognition of carbamazepine, antiseizure drug, with calix(4)arene).

    PubMed

    Meenakshi, C; Jayabal, P; Ramakrishnan, V

    2015-12-01

    The thermodynamic property of the host-guest, inclusion complex formed between p-t-butyl calix(4)arene which is a supramolecule, and the antiseizure drug, carbamazepine was studied. p-t-Butyl calix(4)arene has been used as a host molecule and carbamazepine as a guest molecule. Optical absorption spectral studies were carried out to investigate the molecular recognition properties of p-t-butyl calix(4)arene with carbamazepine. The stochiometry of the host-guest complexes formed and the association constant were determined. An interesting 1:2 stochiometric host-guest complex was formed. Job's continuous method of variation and Benesi-Hildebrand expression were used for the determination of binding constant and the stochiometry of the host-guest complex formed. Molecular dimension of the host molecule plays a vital role in the formation of the host-guest stochiometric complexes.

  3. Engineering responsive polymer building blocks with host-guest molecular recognition for functional applications.

    PubMed

    Hu, Jinming; Liu, Shiyong

    2014-07-15

    CONSPECTUS: All living organisms and soft matter are intrinsically responsive and adaptive to external stimuli. Inspired by this fact, tremendous effort aiming to emulate subtle responsive features exhibited by nature has spurred the invention of a diverse range of responsive polymeric materials. Conventional stimuli-responsive polymers are constructed via covalent bonds and can undergo reversible or irreversible changes in chemical structures, physicochemical properties, or both in response to a variety of external stimuli. They have been imparted with a variety of emerging applications including drug and gene delivery, optical sensing and imaging, diagnostics and therapies, smart coatings and textiles, and tissue engineering. On the other hand, in comparison with molecular chemistry held by covalent bonds, supramolecular chemistry built on weak and reversible noncovalent interactions has emerged as a powerful and versatile strategy for materials fabrication due to its facile accessibility, extraordinary reversibility and adaptivity, and potent applications in diverse fields. Typically involving more than one type of noncovalent interactions (e.g., hydrogen bonding, metal coordination, hydrophobic association, electrostatic interactions, van der Waals forces, and π-π stacking), host-guest recognition refers to the formation of supramolecular inclusion complexes between two or more entities connected together in a highly controlled and cooperative manner. The inherently reversible and adaptive nature of host-guest molecular recognition chemistry, stemming from multiple noncovalent interactions, has opened up a new platform to construct novel types of stimuli-responsive materials. The introduction of host-guest chemistry not only enriches the realm of responsive materials but also confers them with promising new applications. Most intriguingly, the integration of responsive polymer building blocks with host-guest recognition motifs will endow the former with

  4. Engineering responsive polymer building blocks with host-guest molecular recognition for functional applications.

    PubMed

    Hu, Jinming; Liu, Shiyong

    2014-07-15

    CONSPECTUS: All living organisms and soft matter are intrinsically responsive and adaptive to external stimuli. Inspired by this fact, tremendous effort aiming to emulate subtle responsive features exhibited by nature has spurred the invention of a diverse range of responsive polymeric materials. Conventional stimuli-responsive polymers are constructed via covalent bonds and can undergo reversible or irreversible changes in chemical structures, physicochemical properties, or both in response to a variety of external stimuli. They have been imparted with a variety of emerging applications including drug and gene delivery, optical sensing and imaging, diagnostics and therapies, smart coatings and textiles, and tissue engineering. On the other hand, in comparison with molecular chemistry held by covalent bonds, supramolecular chemistry built on weak and reversible noncovalent interactions has emerged as a powerful and versatile strategy for materials fabrication due to its facile accessibility, extraordinary reversibility and adaptivity, and potent applications in diverse fields. Typically involving more than one type of noncovalent interactions (e.g., hydrogen bonding, metal coordination, hydrophobic association, electrostatic interactions, van der Waals forces, and π-π stacking), host-guest recognition refers to the formation of supramolecular inclusion complexes between two or more entities connected together in a highly controlled and cooperative manner. The inherently reversible and adaptive nature of host-guest molecular recognition chemistry, stemming from multiple noncovalent interactions, has opened up a new platform to construct novel types of stimuli-responsive materials. The introduction of host-guest chemistry not only enriches the realm of responsive materials but also confers them with promising new applications. Most intriguingly, the integration of responsive polymer building blocks with host-guest recognition motifs will endow the former with

  5. Cyclodextrin-based host-guest supramolecular nanoparticles for delivery: from design to applications.

    PubMed

    Hu, Qi-Da; Tang, Gu-Ping; Chu, Paul K

    2014-07-15

    CONSPECTUS: Efficient assembly in host-guest interactions is crucial to supramolecular nanotechnology. Cyclodextrins (CDs), which possess a hydrophilic exterior surface and hydrophobic interior cavity on the truncated cone, improve the biocompatibility of nanodelivery systems, and hence, supramolecular approaches utilizing CDs can improve and expand the design and applications of functional delivery systems. Owing to good inclusion ability, αCD and βCD are commonly used in the design and construction of supramolecular structures. In this Account, we describe the design strategies to adopt CDs in host-guest delivery systems. Modification of CDs with polymers is popular in current research due to the potential benefits rendered by cationic protection and improved capability. While the process has only minor influence on the host characteristics of the CD cavity, the interaction between the CD and the guest moiety imparts new attributes to the nanosystems with guest-decorated functional groups such as adamantyl poly(ethylene glycol) (PEG) for coating protection, hybrid guests for conformational flexibility, and adamantyl prodrugs for drug delivery. Some specific agents form inclusion complexes with the polymerized βCDs directly and core-shell nanoparticles with hydrophobic cores and are usually created to carry insoluble drugs while the hydrophilic shells offer protection. These unique designs provide the means to practically adapt special characteristics for additional functions or co-delivery. In order to be accepted clinically, delivery systems need to possess extra functions such as controlled particle size, biodegradability, controlled release, and targeted delivery to overcome the hurdles in delivery. These features can be added to biomaterials by self-assembly of functional groups facilitated by the host-guest interactions. Size control by hybridization of switchable polymer compartments in supramolecular structures contributes to the biodistribution utility

  6. Computational investigation on the host-guest inclusion process of norfloxacin into β-cyclodextrin.

    PubMed

    Maia, Pollyanna P; de Sousa, Sara Maria R; De Almeida, Wagner B; Guimarães, Luciana; Nascimento, Clebio S

    2016-09-01

    A theoretical (1)H NMR spectroscopy and thermodynamic analysis of the host-guest inclusion process involving the norfloxacin (NFX) into β-cyclodextrin (β-CD) was carried out. DFT structure and stabilization energies were obtained in both gas and aqueous phases. We could establish that the complex formation is enthalpy driven, and the hydrogen bonds established between NFX and β-CD play a major role in the complex stabilization. Besides, a theoretical (1)H NMR analysis has shown to be a supplementary proceeding to predict appropriately the inclusion mode of norfloxacin molecule into the β-CD. In this work, a theoretical study of the NFX@β-CD complex is reported for the first time, seeking a deep understanding of topology and thermodynamics of the inclusion complex formation. Graphical Abstract Topology, thermodynamic and (1)H NMR analysis of NFX@β-CD host-guest complexes. PMID:27558797

  7. Computational investigation on the host-guest inclusion process of norfloxacin into β-cyclodextrin.

    PubMed

    Maia, Pollyanna P; de Sousa, Sara Maria R; De Almeida, Wagner B; Guimarães, Luciana; Nascimento, Clebio S

    2016-09-01

    A theoretical (1)H NMR spectroscopy and thermodynamic analysis of the host-guest inclusion process involving the norfloxacin (NFX) into β-cyclodextrin (β-CD) was carried out. DFT structure and stabilization energies were obtained in both gas and aqueous phases. We could establish that the complex formation is enthalpy driven, and the hydrogen bonds established between NFX and β-CD play a major role in the complex stabilization. Besides, a theoretical (1)H NMR analysis has shown to be a supplementary proceeding to predict appropriately the inclusion mode of norfloxacin molecule into the β-CD. In this work, a theoretical study of the NFX@β-CD complex is reported for the first time, seeking a deep understanding of topology and thermodynamics of the inclusion complex formation. Graphical Abstract Topology, thermodynamic and (1)H NMR analysis of NFX@β-CD host-guest complexes.

  8. Host-guest interaction of flavanone and 7-aminoflavone with C-Hexylpyrogallol[4]arene

    NASA Astrophysics Data System (ADS)

    Chandrasekaran, Sowrirajan; Enoch, Israel V. M. V.

    2014-11-01

    In this paper, we report the structures of the host-guest complexes of flavanone and 7-aminoflavone (guests) with C-Hexylpyrogallol[4]arene (host). The study of the host-guest binding is carried out using UV-Visible absorption, steady-state and time-resolved fluorescence, and 2D ROESY spectroscopy. The stoichiometry and the binding constant of the C-Hexylpyrogallol[4]arene-guest complexes are reported based on absorption and fluorescence titrations. Both flavanone and 7-aminoflavone form 1:1 complexes with the host with binding constant values of 1.71 × 104 mol-1 dm3 and 2.06 × 104 mol-1 dm3 respectively. Fluorescence quenching of the two flavonoids on complex formation occurs and the Stern-Volmer constants are reported. The mode of binding of flavanone and 7-aminoflavone with the host molecule is optimized with 2D ROESY and the structures of the inclusion complexes are proposed.

  9. Stimuli-responsive host-guest systems based on the recognition of cryptands by organic guests.

    PubMed

    Zhang, Mingming; Yan, Xuzhou; Huang, Feihe; Niu, Zhenbin; Gibson, Harry W

    2014-07-15

    CONSPECTUS: As the star compounds in host-guest chemistry, the syntheses of crown ethers proclaimed the birth of supramolecular chemistry. Crown ether-based host-guest systems have attracted great attention in self-assembly processes because of their good selectivity, high efficiency, and convenient responsiveness, enabling their facile application to the "bottom-up" approach for construction of functional molecular aggregates, such as artificial molecular machines, drug delivery materials, and supramolecular polymers. Cryptands, as preorganized derivatives of crown ethers, not only possess the above-mentioned properties but also have three-dimensional spatial structures and higher association constants compared with crown ethers. More importantly, the introduction of the additional arms makes cryptand-based host-guest systems responsive to more stimuli, which is crucial for the construction of adaptive or smart materials. In the past decade, we designed and synthesized crown ether-based cryptands as a new type of host for small organic guests with the purpose of greatly increasing the stabilities of the host-guest complexes and preparing mechanically interlocked structures and large supramolecular systems more efficiently while retaining or increasing their stimuli-responsiveness. Organic molecules such as paraquat derivatives and secondary ammonium salts have been widely used in the fabrication of functional supramolecular aggregates. Many host molecules including crown ethers, cyclodextrins, calixarenes, cucurbiturils, pillararenes, and cryptands have been used in the preparation of self-assembled structures with these guest molecules, but among them cryptands exhibit the best stabilities with paraquat derivatives in organic solvents due to their preorganization and additional and optimized binding sites. They enable the construction of sophisticated molecules or supramolecules in high yields, affording a very efficient way to fabricate stimuli

  10. Nanoparticles functionalized with supramolecular host-guest systems for nanomedicine and healthcare.

    PubMed

    Wu, Zilong; Song, Nan; Menz, Ryan; Pingali, Bharadwaj; Yang, Ying-Wei; Zheng, Yuebing

    2015-05-01

    Synthetic macrocyclic host compounds can interact with suitable guest molecules via noncovalent interactions to form functional supramolecular systems. With the synergistic integration of the response of molecules and the unique properties at the nanoscale, nanoparticles functionalized with the host-guest supramolecular systems have shown great potentials for a broad range of applications in the fields of nanoscience and nanotechnology. In this review article, we focus on the applications of the nanoparticles functionalized with supramolecular host-guest systems in nanomedicine and healthcare, including therapeutic delivery, imaging, sensing and removal of harmful substances. A large number of examples are included to elucidate the working mechanisms, advantages, limitations and future developments of the nanoparticle-supramolecule systems in these applications.

  11. Stimuli-responsive host-guest systems based on the recognition of cryptands by organic guests.

    PubMed

    Zhang, Mingming; Yan, Xuzhou; Huang, Feihe; Niu, Zhenbin; Gibson, Harry W

    2014-07-15

    CONSPECTUS: As the star compounds in host-guest chemistry, the syntheses of crown ethers proclaimed the birth of supramolecular chemistry. Crown ether-based host-guest systems have attracted great attention in self-assembly processes because of their good selectivity, high efficiency, and convenient responsiveness, enabling their facile application to the "bottom-up" approach for construction of functional molecular aggregates, such as artificial molecular machines, drug delivery materials, and supramolecular polymers. Cryptands, as preorganized derivatives of crown ethers, not only possess the above-mentioned properties but also have three-dimensional spatial structures and higher association constants compared with crown ethers. More importantly, the introduction of the additional arms makes cryptand-based host-guest systems responsive to more stimuli, which is crucial for the construction of adaptive or smart materials. In the past decade, we designed and synthesized crown ether-based cryptands as a new type of host for small organic guests with the purpose of greatly increasing the stabilities of the host-guest complexes and preparing mechanically interlocked structures and large supramolecular systems more efficiently while retaining or increasing their stimuli-responsiveness. Organic molecules such as paraquat derivatives and secondary ammonium salts have been widely used in the fabrication of functional supramolecular aggregates. Many host molecules including crown ethers, cyclodextrins, calixarenes, cucurbiturils, pillararenes, and cryptands have been used in the preparation of self-assembled structures with these guest molecules, but among them cryptands exhibit the best stabilities with paraquat derivatives in organic solvents due to their preorganization and additional and optimized binding sites. They enable the construction of sophisticated molecules or supramolecules in high yields, affording a very efficient way to fabricate stimuli

  12. Toward Improved Force-Field Accuracy through Sensitivity Analysis of Host-Guest Binding Thermodynamics.

    PubMed

    Yin, Jian; Fenley, Andrew T; Henriksen, Niel M; Gilson, Michael K

    2015-08-13

    Improving the capability of atomistic computer models to predict the thermodynamics of noncovalent binding is critical for successful structure-based drug design, and the accuracy of such calculations remains limited by nonoptimal force field parameters. Ideally, one would incorporate protein-ligand affinity data into force field parametrization, but this would be inefficient and costly. We now demonstrate that sensitivity analysis can be used to efficiently tune Lennard-Jones parameters of aqueous host-guest systems for increasingly accurate calculations of binding enthalpy. These results highlight the promise of a comprehensive use of calorimetric host-guest binding data, along with existing validation data sets, to improve force field parameters for the simulation of noncovalent binding, with the ultimate goal of making protein-ligand modeling more accurate and hence speeding drug discovery.

  13. High-affinity host-guest chemistry of large-ring cyclodextrins.

    PubMed

    Assaf, Khaleel I; Gabel, Detlef; Zimmermann, Wolfgang; Nau, Werner M

    2016-08-10

    The host-guest chemistry of large-ring cyclodextrins (LRCDs) has been largely unexplored due to the lack of suitable guest molecules that bind with significant affinities to enable potential applications. Herein, we report their complexation with dodecaborate anions (B12X12(2-)), a novel class of guest molecules. The binding constants of the inorganic guests (10(4)-10(6) M(-1)) allow their classification as the first tight binders for LRCDs. PMID:27456317

  14. Self-healing supramolecular gels formed by crown ether based host-guest interactions.

    PubMed

    Zhang, Mingming; Xu, Donghua; Yan, Xuzhou; Chen, Jianzhuang; Dong, Shengyi; Zheng, Bo; Huang, Feihe

    2012-07-01

    Automatic repair: a polymer with pendent dibenzo[24]crown-8 units (purple in picture) was cross-linked by two bisammonium salts (green) to form two supramolecular gels based on host-guest interactions. These two gels are stimuli-responsive materials that respond to changes of the pH value and are also self-healing materials, as can be seen by eye and as evidenced by rheological data.

  15. Controlled fragrant molecule release from surface-tethered cyclodextrin host-guest inclusion complexes.

    PubMed

    Schofield, W C E; Badyal, J P S

    2011-06-01

    β-cyclodextrin barrels can be tethered to solid surfaces using the Williamson ether synthesis reaction via an intermediate pulsed plasma deposited poly(4-vinylbenzyl chloride) linker layer. The loading and release of perfume molecules through host-guest inclusion complex formation with surface tethered β-cyclodextrin has been followed by infrared spectroscopy and quartz crystal microbalance measurements. Fragrance release lasts for several months and can be easily recharged.

  16. Self-healing supramolecular gels formed by crown ether based host-guest interactions.

    PubMed

    Zhang, Mingming; Xu, Donghua; Yan, Xuzhou; Chen, Jianzhuang; Dong, Shengyi; Zheng, Bo; Huang, Feihe

    2012-07-01

    Automatic repair: a polymer with pendent dibenzo[24]crown-8 units (purple in picture) was cross-linked by two bisammonium salts (green) to form two supramolecular gels based on host-guest interactions. These two gels are stimuli-responsive materials that respond to changes of the pH value and are also self-healing materials, as can be seen by eye and as evidenced by rheological data. PMID:22653895

  17. Protein Adsorption Switch Constructed by a Pillar[5]arene-Based Host-Guest Interaction.

    PubMed

    Xiao, Xuan; Nie, Guanrong; Zhang, Xiaoyan; Tian, Demei; Li, Haibing

    2016-01-18

    The interfacial properties of solid substrates are of importance for protein adsorption. Herein, we report a reversible protein adsorption switch based on the host-guest interaction of the butoxy pillar[5]arene and adipic acid. By the detector of the contact angle (CA), atomic force microscopy (AFM), and luminoscope on the silicon substrate, the intelligent protein switch exhibits excellent adsorptivity for BSA and switch performance by pH regulation.

  18. Diarylferrocene tweezers for cation binding.

    PubMed

    Lima, Carlos F R A C; Fernandes, Ana M; Melo, André; Gonçalves, Luís M; Silva, Artur M S; Santos, Luís M N B F

    2015-10-01

    The host-guest chemistry of ferrocene derivatives was explored by a combined experimental and theoretical study. Several 1-arylferrocenes and 1,1'-diarylferrocenes were synthesized by the Suzuki-Miyaura cross-coupling reaction. The ability of these compounds to bind small cations in the gas phase was investigated experimentally by electrospray ionization mass spectrometry (ESI-MS). The results evidenced a noticeable ability of all 1,1'-diarylferrocenes studied to bind cations, while the same was not observed for the corresponding 1-arylferrocenes nor ferrocene. The 1,1'-diarylferrocenecation relative interaction energies were evaluated by ESI-MS and quantum chemical calculations and showed that cation binding in these systems follows electrostatic trends. It was found that, due to their unique molecular shape and smooth torsional potentials, 1,1'-diarylferrocenes can act as molecular tweezers of small-sized cations in the gas phase. PMID:26309143

  19. Incommensurate host-guest structures in compressed elements: Hume—Rothery effects as origin

    NASA Astrophysics Data System (ADS)

    Degtyareva, V. F.

    2015-11-01

    Discovery of the incommensurate structure in the element Ba under pressure 15 years ago was followed by findings of a series of similar structures in other compressed elements. Incommensurately modulated structures of the host-guest type consist of a tetragonal host structure and a guest structure. The guest structure forms chains of atoms embedded in the channels of host atoms so that the axial ratio of these subcells along the c axis is not rational. Two types of the host-guest structures have been found so far: with the host cells containing 8 atoms and 16 atoms; in these both types the guest cells contain 2 atoms. These crystal structures contain a non-integer number of atoms in their unit cell: tI11* in Bi, Sb, As, Ba, Sr, Sc and tI19* in Na, K, Rb. We consider here a close structural relationship of these host-guest structures with the binary alloy phase Au3Cd5-tI32. This phase is related to the family of the Hume-Rothery phases that is stabilized by the Fermi sphere-Brillouin zone interaction. From similar considerations for alkali and alkaline-earth elements a necessary condition for structural stability emerges in which the valence electrons band overlaps with the upper core electrons and the valence electron count increases under compression.

  20. A responsive supramolecular polymer formed by orthogonal metal-coordination and cryptand-based host-guest interaction.

    PubMed

    Wei, Peifa; Xia, Binyuan; Zhang, Yanyan; Yu, Yihua; Yan, Xuzhou

    2014-04-18

    Herein, a cation responsive linear supramolecular polymer was constructed in an orthogonal fashion by unifying the themes of coordination-driven self-assembly and cryptand-based host-guest interaction. PMID:24609282

  1. Triple-helix propensity of hydroxyproline and fluoroproline: comparison of host-guest and repeating tripeptide collagen models.

    PubMed

    Persikov, Anton V; Ramshaw, John A M; Kirkpatrick, Alan; Brodsky, Barbara

    2003-09-24

    Peptide models have proved important in defining the structural features of the collagen triple-helix. Some models are based on multiple repeats of a given tripeptide unit, while a host-guest design includes an individual tripeptide unit substituted within a constant repeating Pro-Hyp-Gly framework. In the present study, proline, hydroxyproline, and fluoroproline residues are incorporated in X- or Y-positions of a guest triplet in the host-guest peptide design. All host-guest peptides, including Hyp-Pro-Gly, formed stable triple-helices, even though a triple-helix cannot be formed by (Hyp-Pro-Gly)10. The order of stability Pro-Hyp-Gly > Pro-Pro-Gly > Hyp-Pro-Gly remains the same in all models, while the Pro-Flp-Gly is very stabilizing in a repeating context but destabilizing in a host-guest context. The range of thermal stabilities and calorimetric enthalpies is very small among the five host-guest peptides, consistent with the concept that the effect of one Xaa-Yaa-Gly tripeptide unit in the host-guest system would be less than the much larger variations when there are 10 repeating units. However, a simple additive model based on host-guest peptides predicts a greater stability than experimentally observed. The difference in stability contributions of the same tripeptide unit in host-guest versus repeating tripeptide systems illustrates the impact of sequence environment on stability, and factors that play a role include ring puckering as a consequence of electron inductive effects, residual monomer structure, and native state hydration networks.

  2. A DFT investigation on the host/guest inclusion process of prilocaine into β-cyclodextrin

    NASA Astrophysics Data System (ADS)

    de Sousa, Sara Maria R.; Guimarães, Luciana; Ferrari, Jefferson L.; De Almeida, Wagner B.; Nascimento, Clebio S.

    2016-05-01

    A theoretical analysis of the host/guest inclusion process involving the prilocaine into the β-cyclodextrin was performed. Structure and stabilization energies were calculated, in both gas and aqueous phases, using Density Functional Theory level of theory. As results, a qualitative structure property relationship could be established with structural features being relevant for inclusion complex stabilization: (i) the hydrogen bonds established between guest and host molecules and (ii) the dispersion effect in the formation of the complexes. Besides, a theoretical 1H NMR analysis has shown to be an adequate procedure to predict correctly the inclusion mode of guest molecule into the host.

  3. Modular self-assembly, characterization, and host-guest chemistry of nanoscale organometallic architectures

    SciTech Connect

    Manna, J.; Kuehl, C.J.; Stang, P.J.; Muddiman, D.C.; Smith, R.D.

    1997-12-31

    The supramolecular synthesis and chemistry of organic macrocycles has been the focus of considerable study for over thirty years. In contrast, the chemistry of analogous inorganic and organometallic macrocycles is in it infancy; little is know about the stability, spectroscopic and physical properties, and chemistry of these species. We will report on the design of several unique supramolecular macrocycles and the characterization of these species by a range of spectroscopic techniques, including electrospray-ionization Fourier transform ion cyclotron resonance spectrometry. Preliminary data concerning the host-guest chemistry of these macrocycles will also be presented.

  4. Praseodymium(III)-based bis-metallacalix[4]arene with host-guest behaviour.

    PubMed

    Xu, Gong-Feng; Gamez, Patrick; Teat, Simon J; Tang, Jinkui

    2010-05-14

    The reaction of Pr(NO(3))(3).6H(2)O with the ligand 2-hydroxy-N-(2'-hydroxyethyl)-3-methoxybenzamide (H(3)L) in MeOH-MeCN generates the nonanuclear compound [Pr(9)(H(2)L)(8)(OH)(10)(NO(3))(8)](NO(3))(H(2)O)(2)(CH(3)CN) (), whose single-crystal X-ray structure reveals the presence of metallacalix[4]arene cavities that host guest molecules. The crystal packing of the antiferromagnetic Pr(9) cluster shows an intricate network of hydrogen bonds producing a one-dimensional supramolecular chain.

  5. Direct Measurement of Electron Transfer in Nanoscale Host-Guest Systems: Metallocenes in Carbon Nanotubes.

    PubMed

    McSweeney, Robert L; Chamberlain, Thomas W; Baldoni, Matteo; Lebedeva, Maria A; Davies, E Stephen; Besley, Elena; Khlobystov, Andrei N

    2016-09-12

    Electron-transfer processes play a significant role in host-guest interactions and determine physicochemical phenomena emerging at the nanoscale that can be harnessed in electronic or optical devices, as well as biochemical and catalytic systems. A novel method for qualifying and quantifying the electronic doping of single walled carbon nanotubes (SWNTs) using electrochemistry has been developed that establishes a direct link between these experimental measurements and ab initio DFT calculations. Metallocenes such as cobaltocene and methylated ferrocene derivatives were encapsulated inside SWNTs (1.4 nm diameter) and cyclic voltammetry (CV) was performed on the resultant host-guest systems. The electron transfer between the guest molecules and the host SWNTs is measured as a function of shift in the redox potential (E1/2 ) of Co(II) /Co(I) , Co(III) /Co(II) and Fe(III) /Fe(II) . Furthermore, the shift in E1/2 is inversely proportional to the nanotube diameter. To quantify the amount of electron transfer from the guest molecules to the SWNTs, a novel method using coulometry was developed, allowing the mapping of the density of states and the Fermi level of the SWNTs. Correlated with theoretical calculations, coulometry provides an accurate indication of n/p-doping of the SWNTs.

  6. Tunable polymer brush/Au NPs hybrid plasmonic arrays based on host-guest interaction.

    PubMed

    Fang, Liping; Li, Yunfeng; Chen, Zhaolai; Liu, Wendong; Zhang, Junhu; Xiang, Siyuan; Shen, Huaizhong; Li, Zibo; Yang, Bai

    2014-11-26

    The fabrication of versatile gold nanoparticle (Au NP) arrays with tunable optical properties by a novel host-guest interaction are presented. The gold nanoparticles were incorporated into polymer brushes by host-guest interaction between β-cyclodextrin (β-CD) ligand of gold nanoparticles and dimethylamino group of poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA). The gold nanoparticle arrays were prepared through the template of PDMAEMA brush patterns which were fabricated combining colloidal lithography and surface-initiated atom-transfer radical polymerization (SI-ATRP). The structure parameters of gold nanoparticle patterns mediated by polymer brushes such as height, diameters, periods and distances, could be easily tuned by tailoring the etching time or size of colloidal spheres in the process of colloidal lithography. The change of optical properties induced by different gold nanoparticle structures was demonstrated. The direct utilization of PDMAEMA brushes as guest avoids a series of complicated modification process and the PDMAEMA brushes can be grafted on various substrates, which broaden its applications. The prepared gold naoparticle arrays are promising in applications of nanosensors, memory storage and surface enhanced spectroscopy. PMID:25347749

  7. A Stimuli-Responsive Nanopore Based on a Photoresponsive Host-Guest System

    NASA Astrophysics Data System (ADS)

    Ying, Yi-Lun; Zhang, Junji; Meng, Fu-Na; Cao, Chan; Yao, Xuyang; Willner, Itamar; Tian, He; Long, Yi-Tao

    2013-04-01

    The open-close states of the ion channels in a living system are regulated by multiple stimuli such as ligand, pH, potential and light. Functionalizing natural channels by using synthetic chemistry would provide biological nanopores with novel properties and applications. Here we use para-sulfonato-calix[4]arene-based host-guest supramolecular system to develop artificial gating mechanisms aiming at regulating wild-type α-HL commanded by both ligand and light stimuli. Using the gating property of α-hemolysin, we studied the host-guest interactions between para-sulfonato-calix[4]arene and 4, 4'-dipyridinium-azobenzene at the single-molecule level. Subsequently, we have extended the application of this gating system to the real-time study of light-induced molecular shuttle based on para-sulfonato-calix[4]arene and 4, 4'-dipyridinium-azobenzene at the single-molecule level. These experiments provide a more efficient method to develop a general tool to analyze the individual motions of supramolecular systems by using commercially available α-HL nanopores.

  8. Straightforward functionalization of breath figures: Simultaneous orthogonal host-guest and pH-responsive interfaces.

    PubMed

    Sanz de León, Alberto; Muñoz-Bonilla, Alexandra; Gallardo, Alberto; Fernandez-Mayoralas, Alfonso; Bernard, Julien; Rodríguez-Hernández, Juan

    2015-11-01

    Herein, we report the design and preparation of multireversible smart porous surfaces combining two different abilities. On the one hand, either neutral or negatively charged surfaces can be formed by formation/disruption of host-guest complexes. On the other hand, these surfaces have the capability of alternating negatively and positively charge upon complexation of a polycation. Moreover, these two functionalization steps were demonstrated to be reversible so that the initial surface can be recovered and employed again. For this purpose, first, a copolymer was prepared by polymerization of two different monomers, i.e. styrene (S) and a styrene modified with cyclodextrin (SCD) by click chemistry. Blends of this copolymer and polystyrene were employed to fabricate porous surfaces with controlled pore sizes and chemical distribution by the breath figures technique. More precisely, the cyclodextrin (CD) moieties, specifically located inside the holes of the surface, interact reversibly with adamantane end-terminated poly(acrylic acid) chain (Ada-PAA85). The latter served to establish electrostatic interaction with a polycation (poly-L-lysine, PLL), leading to positively charged surface. These interactions, both host-guest and electrostatic, can be inverted obtaining again the original surface, proving the full reversibility of the system. PMID:26196710

  9. Driving Forces Controlling Host-Guest Recognition in Supercritical Carbon Dioxide Solvent.

    PubMed

    Ingrosso, Francesca; Altarsha, Muhannad; Dumarçay, Florence; Kevern, Gwendal; Barth, Danielle; Marsura, Alain; Ruiz-López, Manuel F

    2016-02-24

    The formation of supramolecular host-guest complexes is a very useful and widely employed tool in chemistry. However, supramolecular chemistry in non-conventional solvents such as supercritical carbon dioxide (scCO2 ), one of the most promising sustainable solvents, is still in its infancy. In this work, we explored a successful route to the development of green processes in supercritical CO2 by combining a theoretical approach with experiments. We were able to synthesize and characterize an inclusion complex between a polar aromatic molecule (benzoic acid) and peracetylated-β-cyclodextrin, which is soluble in the supercritical medium. This finding opens the way to wide, environmental friendly, applications of scCO2 in many areas of chemistry, including supramolecular synthesis, reactivity and catalysis, micro and nano-particle formation, molecular recognition, as well as enhanced extraction processes with increased selectivity.

  10. Host-Guest Strategy to Reversibly Control a Chloride Carrier Process with Cyclodextrins.

    PubMed

    Gravel, Julien; Kempf, Julie; Schmitzer, Andreea

    2015-12-14

    Herein, we report a reversible modular chloride transport process based on host-guest competitive interactions between an imidazolium-based chloride carrier and beta-cyclodextrin. We report evidence for the formation of the supramolecular complex between 1,3-bis(2-(adamantan-1-yl)ethyl)imidazolium bis(trifluorometyl-sulfonyl)imide with two β-cyclodextrins. Through fluorescence assays in liposomes and black lipid membrane experiments, we demonstrate that the formation of the supramolecular complex results in the inhibition of the chloride transport. We show that the chloride transport process can be entirely restored in the presence of competitive adamantyl-functionalized guests. This is the first example of an entirely reversible modular chloride transport process in phospholipid bilayers involving a mobile carrier transporter and cyclodextrin supramolecular complex.

  11. Rational Design of Multifunctional Gold Nanoparticles via Host-Guest Interaction for Cancer-Targeted Therapy.

    PubMed

    Chen, Wei-Hai; Lei, Qi; Luo, Guo-Feng; Jia, Hui-Zhen; Hong, Sheng; Liu, Yu-Xin; Cheng, Yin-Jia; Zhang, Xian-Zheng

    2015-08-12

    A versatile gold nanoparticle-based multifunctional nanocomposite AuNP@CD-AD-DOX/RGD was constructed flexibly via host-guest interaction for targeted cancer chemotherapy. The pH-sensitive anticancer prodrug AD-Hyd-DOX and the cancer-targeted peptide AD-PEG8-GRGDS were modified on the surface of AuNP@CD simultaneously, which endowed the resultant nanocomposite with the capability to selectively eliminate cancer cells. In vitro studies indicated that the AuNP@CD-AD-DOX/RGD nanocomposite was preferentially uptaken by cancer cells via receptor-mediated endocytosis. Subsequently, anticancer drug DOX was released rapidly upon the intracellular trigger of the acid microenvirenment of endo/lysosomes, inducing apoptosis in cancer cells. As the ideal drug nanocarrier, the multifunctional gold nanoparticles with the active targeting and controllable intracellular release ability hold the great potential in cancer therapy.

  12. Tailored host-guest lipidic cubic phases: a protocell model exhibiting nucleic acid recognition.

    PubMed

    Komisarski, Marek; Osornio, Yazmin M; Siegel, Jay S; Landau, Ehud M

    2013-01-21

    A classical conundrum in origin-of-life studies relates to the nature of the first chemical system: was it a carrier of genetic information or a facilitator of cellular compartmentalization? Here we present a system composed of tailor-made nucleolipids and hydrated monoolein, which assemble at ambient temperatures to form host-guest lipidic cubic phase (LCP) materials that are stable in bulk water and can perform both functions. As such, they may represent a molecular model for a protocell in origin-of-life studies. Nucleolipids within the lipidic material sequester and bind selectively complementary oligonucleotide sequences from solution by virtue of base-pairing; noncomplementary sequences diffuse freely between the LCP material and the bulk aqueous environment. Sequence specific enrichment of nucleic acids within the LCP material demonstrates an effective mechanism for selection of genetic material in these cell-mimetic systems. PMID:23239006

  13. Multifunctional radical-doped polyoxometalate-based host-guest material: photochromism and photocatalytic activity.

    PubMed

    Liao, Jian-Zhen; Zhang, Hai-Long; Wang, Sa-Sa; Yong, Jian-Ping; Wu, Xiao-Yuan; Yu, Rongmin; Lu, Can-Zhong

    2015-05-01

    An effective strategy to synthesize multifunctional materials is the incorporation of functional organic moieties and metal oxide clusters via self-assembly. A rare multifunctional radical-doped zinc-based host-guest crystalline material was synthesized with a fast-responsive reversible ultraviolet visible light photochromism, photocontrolled tunable luminescence, and highly selective photocatalytic oxidation of benzylic alcohols as a result of blending of distinctively different functional components, naphthalenediimide tectons, and polyoxometalates (POMs). It is highly unique to link π-electron-deficient organic tectons and POMs by unusual POMs anion-π interactions, which are not only conducive to keeping the independence of each component but also effectively promoting the charge transfer or exchange among the components to realize the fast-responsive photochromism, photocontrolled tunable luminescence, and photocatalytic activity.

  14. 3D nitrogen-doped graphene/β-cyclodextrin: host-guest interactions for electrochemical sensing

    NASA Astrophysics Data System (ADS)

    Liu, Jilun; Leng, Xuanye; Xiao, Yao; Hu, Chengguo; Fu, Lei

    2015-07-01

    Host-guest interactions, especially those between cyclodextrins (CDs, including α-, β- and γ-CD) and various guest molecules, exhibit a very high supramolecular recognition ability. Thus, they have received considerable attention in different fields. These specific interactions between host and guest molecules are promising for biosensing and clinical detection. However, there is a lack of an ideal electrode substrate for CDs to increase their performance in electrochemical sensing. Herein, we propose a new 3D nitrogen-doped graphene (3D-NG) based electrochemical sensor, taking advantage of the superior sensitivity of host-guest interactions. Our 3D-NG was fabricated by a template-directed chemical vapour deposition (CVD) method, and it showed a large specific surface area, a high capacity for biomolecules and a high electron transfer efficiency. Thus, for the first time, we took 3D-NG as an electrode substrate for β-CD to establish a new type of biosensor. Using dopamine (DA) and acetaminophen (APAP) as representative guest molecules, our 3D-NG/β-CD biosensor shows extremely high sensitivities (5468.6 μA mM-1 cm-2 and 2419.2 μA mM-1 cm-2, respectively), which are significantly higher than those reported in most previous studies. The stable adsorption of β-CD on 3D-NG indicates potential applications in clinical detection and medical testing.Host-guest interactions, especially those between cyclodextrins (CDs, including α-, β- and γ-CD) and various guest molecules, exhibit a very high supramolecular recognition ability. Thus, they have received considerable attention in different fields. These specific interactions between host and guest molecules are promising for biosensing and clinical detection. However, there is a lack of an ideal electrode substrate for CDs to increase their performance in electrochemical sensing. Herein, we propose a new 3D nitrogen-doped graphene (3D-NG) based electrochemical sensor, taking advantage of the superior sensitivity

  15. Networked-cage microcrystals for evaluation of host-guest interactions.

    PubMed

    Matsuzaki, Shohei; Arai, Tatsuhiko; Ikemoto, Koki; Inokuma, Yasuhide; Fujita, Makoto

    2014-12-31

    We have developed a new synthetic protocol for the preparation of a microcrystalline powder (median size: X50 = 25 μm) of networked M6L4 cages 1a for the stationary phase of an affinity column on a greater than 50 g scale. Analogously to large single crystals 1b (X50 ≈ 0.5 mm), microcrystals 1a accommodate guest molecules tetrathiafulvalene (TTF) and fullerene (C60) at up to 32 and 35 wt %, respectively. Importantly, the host-guest interactions within networked cages could be evaluated in terms of the retention time from HPLC analysis by using microcrystals 1a as the stationary phase. In this way, favorable guests for networked cages 1 and even solution M6L4 cage 2 could easily be assessed by HPLC.

  16. Multifunctional radical-doped polyoxometalate-based host-guest material: photochromism and photocatalytic activity.

    PubMed

    Liao, Jian-Zhen; Zhang, Hai-Long; Wang, Sa-Sa; Yong, Jian-Ping; Wu, Xiao-Yuan; Yu, Rongmin; Lu, Can-Zhong

    2015-05-01

    An effective strategy to synthesize multifunctional materials is the incorporation of functional organic moieties and metal oxide clusters via self-assembly. A rare multifunctional radical-doped zinc-based host-guest crystalline material was synthesized with a fast-responsive reversible ultraviolet visible light photochromism, photocontrolled tunable luminescence, and highly selective photocatalytic oxidation of benzylic alcohols as a result of blending of distinctively different functional components, naphthalenediimide tectons, and polyoxometalates (POMs). It is highly unique to link π-electron-deficient organic tectons and POMs by unusual POMs anion-π interactions, which are not only conducive to keeping the independence of each component but also effectively promoting the charge transfer or exchange among the components to realize the fast-responsive photochromism, photocontrolled tunable luminescence, and photocatalytic activity. PMID:25859742

  17. An extremely stable host-guest complex that functions as a fluorescence probe for calcium ions.

    PubMed

    Lin, Chi-Feng; Liu, Yi-Hung; Lai, Chien-Chen; Peng, Shie-Ming; Chiu, Sheng-Hsien

    2006-06-01

    Herein, we report a crown ether based molecular cage that forms extremely stable supramolecular complexes with dimethyldiazapyrenium (DMDAP) ions in CD(3)CN through the collaboration of multiple weak C-HO hydrogen bonds. The very strong binding affinity in this host-guest system allows the molecular cage to bleach the fluorescence signal of DMDAP substantially in equimolar solutions at concentrations as low as 1 x 10(-5) M. Remarkably, a 1x10(-5) M equimolar solution of the molecular cage and DMDAP is highly selective toward Ca(2+) ions-relative to other biologically important Li(+), Na(+), K(+), and Mg(2+) ions-and causes a substantial increase in the fluorescence intensity of the solution. As a result, this molecular cage/DMDAP complex behaves as a supramolecular fluorescence probe for the detection of Ca(2+) ions in solution.

  18. Host-guest complexation of [60]fullerenes and porphyrins enabled by "click chemistry".

    PubMed

    Ho, Khanh-Hy Le; Hijazi, Ismail; Rivier, Lucie; Gautier, Christelle; Jousselme, Bruno; de Miguel, Gustavo; Romero-Nieto, Carlos; Guldi, Dirk M; Heinrich, Benoit; Donnio, Bertrand; Campidelli, Stéphane

    2013-08-19

    Herein the synthesis, characterization, and organization of a first-generation dendritic fulleropyrrolidine bearing two pending porphyrins are reported. Both the dendron and the fullerene derivatives were synthesized by Cu(I) -catalyzed alkyne-azide cycloaddition (CuAAC). The electron-donor-acceptor conjugate possesses a shape that allows the formation of supramolecular complexes by encapsulation of C60 within the jaws of the two porphyrins of another molecule. The interactions between the two photoactive units (i.e., C60 and Zn-porphyrin) were confirmed by cyclic voltammetry as well as by steady-state and time-resolved spectroscopy. For example, a shift of about 85 mV was found for the first reduction of C60 in the electron-donor-acceptor conjugate compared with the parent molecules, which indicates that C60 is included in the jaws of the porphyrin. The fulleropyrrolidine compound exhibits a rich polymorphism, which was corroborated by AFM and SEM. In particular, it was found to form supramolecular fibrils when deposited on substrates. The morphology of the fibrils suggests that they are formed by several rows of fullerene-porphyrin complexes.

  19. Laser Spectroscopic Study of Cold Gas-Phase Host-Guest Complexes of Crown Ethers.

    PubMed

    Ebata, Takayuki; Inokuchi, Yoshiya

    2016-06-01

    The structure, molecular recognition, and inclusion effect on the photophysics of guest species are investigated for neutral and ionic cold host-guest complexes of crown ethers (CEs) in the gas phase. Here, the cold neutral host-guest complexes are produced by a supersonic expansion technique and the cold ionic complexes are generated by the combination of electrospray ionization (ESI) and a cryogenically cooled ion trap. The host species are 3n-crown-n (3nCn; n = 4, 5, 6, 8) and (di)benzo-3n-crown-n ((D)B3nCn; n = 4, 5, 6, 8). For neutral guests, we have chosen water and aromatic molecules, such as phenol and benzenediols, and as ionic species we have chosen alkali-metal ions (M(+) ). The electronic spectra and isomer-specific vibrational spectra for the complexes are observed with various laser spectroscopic methods: laser-induced fluorescence (LIF); ultraviolet-ultraviolet hole-burning (UV-UV HB); and IR-UV double resonance (IR-UV DR) spectroscopy. The obtained spectra are analyzed with the aid of quantum chemical calculations. We will discuss how the host and guest species change their flexible structures for forming best-fit stable complexes (induced fitting) and what kinds of interactions are operating for the stabilization of the complexes. For the alkali metal ion•CE complexes, we investigate the solvation effect by attaching water molecules. In addition to the ground-state stabilization problem, we will show that the complexation leads to a drastic effect on the excited-state electronic structure and dynamics of the guest species, which we call a "cage-like effect". PMID:27006080

  20. Enzyme-free electrochemical immunosensor based on host-guest nanonets catalyzing amplification for procalcitonin detection.

    PubMed

    Shen, Wen-Jun; Zhuo, Ying; Chai, Ya-Qin; Yang, Zhe-Han; Han, Jing; Yuan, Ruo

    2015-02-25

    An enzyme-free electrochemical immunosensor based on the host-guest nanonets of N,N-bis(ferrocenoyl)-diaminoethane/β-cyclodextrins/poly(amidoamine) dendrimer-encapsulated Au nanoparticles (Fc-Fc/β-CD/PAMAM-Au) for procalcitonin (PCT) detection has been developed in this study. The signal probe was constructed as follows: amine-terminated β-CD was adsorbed to PAMAM-Au first, and then the prepared Fc-Fc was recognized by the β-CD to form stable host-guest nanonets. Next, secondary antibodies (Ab2) were attached into the formed netlike nanostructure of Fc-Fc/β-CD/PAMAM-Au by chemical absorption between PAMAM-Au and -NH2 of β-CD. Herein, the PAMAM-Au act not only as nanocarriers for anchoring large amounts of the β-CD and Ab2 but also as nanocatalysts to catalyze the oxidation of ascorbic acid (AA) for signal amplification. Moreover, the Fc-Fc could be stably immobilized by the hydrophobic inner cavity of β-CD as well as improving solubility by the hydrophilic exterior of β-CD. With the unique structure of two ferrocene units, Fc-Fc not only affords more electroactive groups to make the electrochemical response more sensitive but also plays a role of combining dispersive β-CD-functionalized PAMAM-Au to form the netlike nanostructure. Furthermore, Fc-Fc exhibits good catalytic activity for AA oxidation. When the detection solution contained AA, the synergetic catalysis of PAMAM-Au and Fc-Fc to AA oxidation could be obtained, realizing enzyme-free signal amplification. The proposed immunosensor provided a linear range from 1.80 pg/mL to 500 ng/mL for PCT detection and a detection limit of 0.36 pg/mL under optimal experimental conditions. Moreover, the immunosensor has shown potential application in clinical detection of PCT.

  1. Supramolecular organic frameworks: engineering periodicity in water through host-guest chemistry.

    PubMed

    Tian, Jia; Chen, Lan; Zhang, Dan-Wei; Liu, Yi; Li, Zhan-Ting

    2016-05-11

    The development of homogeneous, water-soluble periodic self-assembled structures comprise repeating units that produce porosity in two-dimensional (2D) or three-dimensional (3D) spaces has become a topic of growing interest in the field of supramolecular chemistry. Such novel self-assembled entities, known as supramolecular organic frameworks (SOFs), are the result of programmed host-guest interactions, which allows for the thermodynamically controlled generation of monolayer sheets or a diamondoid architecture with regular internal cavities or pores under mild conditions. This feature article aims at propagating the conceptually novel SOFs as a new entry into conventional supramolecular polymers. In the first section, we will describe the background of porous solid frameworks and supramolecular polymers. We then introduce the self-assembling behaviour of several multitopic flexible molecules, which is closely related to the design of periodic SOFs from rigid multitopic building blocks. This is followed by a brief discussion of cucurbit[8]uril (CB[8])-encapsulation-enhanced aromatic stacking in water. The three-component host-guest pattern based on this stacking motif has been utilized to drive the formation of most of the new SOFs. In the following two sections, we will highlight the main advances in the construction of 2D and 3D SOFs and the related functional aspects. Finally, we will offer our opinions on future directions for both structures and functions. We hope that this article will trigger the interest of researchers in the field of chemistry, physics, biology and materials science, which should help accelerate the applications of this new family of soft self-assembled organic frameworks. PMID:27094341

  2. Supramolecular organic frameworks: engineering periodicity in water through host-guest chemistry.

    PubMed

    Tian, Jia; Chen, Lan; Zhang, Dan-Wei; Liu, Yi; Li, Zhan-Ting

    2016-05-11

    The development of homogeneous, water-soluble periodic self-assembled structures comprise repeating units that produce porosity in two-dimensional (2D) or three-dimensional (3D) spaces has become a topic of growing interest in the field of supramolecular chemistry. Such novel self-assembled entities, known as supramolecular organic frameworks (SOFs), are the result of programmed host-guest interactions, which allows for the thermodynamically controlled generation of monolayer sheets or a diamondoid architecture with regular internal cavities or pores under mild conditions. This feature article aims at propagating the conceptually novel SOFs as a new entry into conventional supramolecular polymers. In the first section, we will describe the background of porous solid frameworks and supramolecular polymers. We then introduce the self-assembling behaviour of several multitopic flexible molecules, which is closely related to the design of periodic SOFs from rigid multitopic building blocks. This is followed by a brief discussion of cucurbit[8]uril (CB[8])-encapsulation-enhanced aromatic stacking in water. The three-component host-guest pattern based on this stacking motif has been utilized to drive the formation of most of the new SOFs. In the following two sections, we will highlight the main advances in the construction of 2D and 3D SOFs and the related functional aspects. Finally, we will offer our opinions on future directions for both structures and functions. We hope that this article will trigger the interest of researchers in the field of chemistry, physics, biology and materials science, which should help accelerate the applications of this new family of soft self-assembled organic frameworks.

  3. An ion signal responsive dynamic protein nano-spring constructed by high ordered host-guest recognition.

    PubMed

    Si, Chengye; Li, Jiaxi; Luo, Quan; Hou, Chunxi; Pan, Tiezheng; Li, Hongbin; Liu, Junqiu

    2016-02-18

    A protein self-assembly nano-spring was developed through host-guest interactions between cucurbit[8]uril and tripeptide FGG tags of fusion protein FGG-recoverin-GST. Fine control of the conformational changes of the Ca(2+)-responsive domain allows for a 50% stretch of the protein nano-spring as it switches from the contracted state to the extended state.

  4. Gas/solvent-induced transformation and expansion of a nonporous solid to 1:1 host guest form

    SciTech Connect

    Thallapally, Praveen K.; McGrail, B. Peter; Dalgarno, Scott J.; Atwood, Jerry L.

    2008-07-01

    Herein we report the gas (CO2, N2O and propane) and solvent (CS2 and acetone) induced transformation and expansion of guest free thermodynamic form of a p-tert-butylcalix [4]arene to 1:1 host guest form.

  5. Light-triggered crystallization of a molecular host-guest complex.

    PubMed

    Clever, Guido H; Tashiro, Shohei; Shionoya, Mitsuhiko

    2010-07-28

    The control of structural changes in supramolecular assemblies is a key point in the development of molecular machines. The reversible photoisomerization of organic compounds such as azobenzene using light as an external input is especially suited because no waste products are generated. Based on our previous studies on the quantitative encapsulation of suitably sized bis-sulfonate guests by a self-assembled, metal-organic cage consisting of four rigid, bent bis-monodentate pyridyl ligands and two Pd(II) ions, we show here how the light-switchable guest cis-4,4'-azobenzene bis-sulfonate can be expelled from its 1:1 host-guest complex triggered by its photoisomerization to the trans-isomer. Using a highly soluble, PEGylated cage derivative, the full reversibility of this light-driven encapsulation/release process is demonstrated. In contrast, a sample of the less soluble, unsubstituted cages including 1 equiv of the cis-guest was shown to result in immediate crystallization upon photoisomerization of the guest. X-ray structure analysis confirmed the guest molecules having left the cavity of the host and on the contrary joining the cages into a polymeric material by binding to their Pd(II) centers from outside.

  6. Vesicular gold assemblies based on host-guest inclusion and its controllable release of doxorubicin.

    PubMed

    Ha, Wei; Kang, Yang; Peng, Shu-Lin; Ding, Li-Sheng; Zhang, Sheng; Li, Bang-Jing

    2013-12-13

    We have developed a kind of gold nanoparticle (AuNP) in which polyethylene glycol (PEG) and poly(N-isopropylacrylamide) (PNIPAM) are attached on the surface of a gold nanocrystal through the host-guest inclusion between adamantane groups (ADA) and β-cyclodextrin (β-CD). The resulting AuNPs become amphiphilic in water above body temperature and self-assemble into vesicles. It is found that these vesicles can load doxorubicin (Dox) effectively. With a decrease in temperature, the PNIPAM shifted from hydrophobic to hydrophilic, causing Au vesicles to disassemble into stable small AuNPs, triggering the release of Dox. These hybrid vesicles, combining polymer functionality with the intriguing properties of AuNPs, can first release free Dox and AuNP/Dox at a site of a tumor through the application of either simple ice packs or deeply penetrating cryoprobes, then the AuNP/Dox can be taken in by tumor cells and destroy them like miniature munitions. Furthermore, these vesicles showed other therapeutic possibilities due to the presence of gold. We believe that the development of such multi-functional vesicles will provide new and therapeutically useful means for medical applications. PMID:24231410

  7. High Precision Measurement of Isotope Effects on Noncovalent Host-Guest Interactions

    SciTech Connect

    Mugridge, Jeffrey S.; Bergman, Robert G.; Raymond, Kenneth N.

    2009-06-23

    Isotope effects (IEs) are a powerful tool for examining the reactivity of, and interactions between, molecules. Recently, secondary IEs have been used to probe the nature of noncovalent interactions between guest and host molecules in supramolecular systems. While these studies can provide valuable insight into the specific interactions governing guest recognition and binding properties, IEs on noncovalent interactions are often very small and difficult to measure precisely. The Perrin group has developed an NMR titration method capable of determining ratios of equilibrium constants with remarkable precision. They have used this technique to study small, secondary equilibrium isotope effects (EIEs) on the acidity of carboxylic acids and phenols and on the basicity of amines, measuring differences down to thousandths of a pK{sub a} unit. It occurred to us that this titration method can in principle measure relative equilibrium constants for any process which is fast on the NMR timescale and for which the species under comparison are distinguishable by NMR. Here we report the application of this method to measure very small EIEs on noncovalent host-guest interactions in a supramolecular system.

  8. Selective Organic and Organometallic Reactions in Water-Soluble Host-Guest Supramolecular Systems

    SciTech Connect

    Pluth, Michael D.; Raymond, Kenneth N.; Bergman, Robert G.

    2008-02-16

    Inspired by the efficiency and selectivity of enzymes, synthetic chemists have designed and prepared a wide range of host molecules that can bind smaller molecules with their cavities; this area has become known as 'supramolecular' or 'host-guest' chemistry. Pioneered by Lehn, Cram, Pedersen, and Breslow, and followed up by a large number of more recent investigators, it has been found that the chemical environment in each assembly - defined by the size, shape, charge, and functional group availability - greatly influences the guest-binding characteristics of these compounds. In contrast to the large number of binding studies that have been carried out in this area, the exploration of chemistry - especially catalytic chemistry - that can take place inside supramolecular host cavities is still in its infancy. For example, until the work described here was carried out, very few examples of organometallic reactivity inside supramolecular hosts were known, especially in water solution. For that reason, our group and the group directed by Kenneth Raymond decided to take advantage of our complementary expertise and attempt to carry out metal-mediated C-H bond activation reactions in water-soluble supramolecular systems. This article begins by providing background from the Raymond group in supramolecular coordination chemistry and the Bergman group in C-H bond activation. It goes on to report the results of our combined efforts in supramolecular C-H activation reactions, followed by extensions of this work into a wider range of intracavity transformations.

  9. Vesicular gold assemblies based on host-guest inclusion and its controllable release of doxorubicin

    NASA Astrophysics Data System (ADS)

    Ha, Wei; Kang, Yang; Peng, Shu-Lin; Ding, Li-Sheng; Zhang, Sheng; Li, Bang-Jing

    2013-12-01

    We have developed a kind of gold nanoparticle (AuNP) in which polyethylene glycol (PEG) and poly(N-isopropylacrylamide) (PNIPAM) are attached on the surface of a gold nanocrystal through the host-guest inclusion between adamantane groups (ADA) and β-cyclodextrin (β-CD). The resulting AuNPs become amphiphilic in water above body temperature and self-assemble into vesicles. It is found that these vesicles can load doxorubicin (Dox) effectively. With a decrease in temperature, the PNIPAM shifted from hydrophobic to hydrophilic, causing Au vesicles to disassemble into stable small AuNPs, triggering the release of Dox. These hybrid vesicles, combining polymer functionality with the intriguing properties of AuNPs, can first release free Dox and AuNP/Dox at a site of a tumor through the application of either simple ice packs or deeply penetrating cryoprobes, then the AuNP/Dox can be taken in by tumor cells and destroy them like miniature munitions. Furthermore, these vesicles showed other therapeutic possibilities due to the presence of gold. We believe that the development of such multi-functional vesicles will provide new and therapeutically useful means for medical applications.

  10. Sustained Small Molecule Delivery from Injectable Hyaluronic Acid Hydrogels through Host-Guest Mediated Retention

    PubMed Central

    Mealy, Joshua E.; Rodell, Christopher B.; Burdick, Jason A.

    2015-01-01

    Self-assembled and injectable hydrogels have many beneficial properties for the local delivery of therapeutics; however, challenges still exist in the sustained release of small molecules from these highly hydrated networks. Host-guest chemistry between cyclodextrin and adamantane has been used to create supramolecular hydrogels from modified polymers. Beyond assembly, this chemistry may also provide increased drug retention and sustained release through the formation of inclusion complexes between drugs and cyclodextrin. Here, we engineered a two-component system from adamantane-modified and β-cyclodextrin (CD)-modified hyaluronic acid (HA), a natural component of the extracellular matrix, to produce hydrogels that are both injectable and able to sustain the release of small molecules. The conjugation of cyclodextrin to HA dramatically altered its affinity for hydrophobic small molecules, such as tryptophan. This interaction led to lower molecule diffusivity and the release of small molecules for up to 21 days with release profiles dependent on CD concentration and drug-CD affinity. There was significant attenuation of release from the supramolecular hydrogels (~20% release in 24h) when compared to hydrogels without CD (~90% release in 24h). The loading of small molecules also had no effect on hydrogel mechanics or self-assembly properties. Finally, to illustrate this controlled delivery approach with clinically used small molecule pharmaceuticals, we sustained the release of two widely used drugs (i.e., doxycycline and doxorubicin) from these hydrogels. PMID:26693019

  11. Host-Guest Binding-Site-Tunable Self-Assembly of Stimuli-Responsive Supramolecular Polymers.

    PubMed

    Yao, Hao; Qi, Miao; Liu, Yuyang; Tian, Wei

    2016-06-13

    Despite the remarkable progress made in controllable self-assembly of stimuli-responsive supramolecular polymers (SSPs), a basic issue that has not been consideration to date is the essential binding site. The noncovalent binding sites, which connect the building blocks and endow supramolecular polymers with their ability to respond to stimuli, are expected to strongly affect the self-assembly of SSPs. Herein, the design and synthesis of a dual-stimuli thermo- and photoresponsive Y-shaped supramolecular polymer (SSP2) with two adjacent β-cyclodextrin/azobenzene (β-CD/Azo) binding sites, and another SSP (SSP1) with similar building blocks, but only one β-CD/Azo binding site as a control, are described. Upon gradually increasing the polymer solution temperature or irradiating with UV light, SSP2 self-assemblies with a higher binding-site distribution density; exhibits a flower-like morphology, smaller size, and more stable dynamic aggregation process; and greater controllability for drug-release behavior than those observed with SSP1 self-assemblies. The host-guest binding-site-tunable self-assembly was attributed to the positive cooperativity generated among adjacent binding sites on the surfaces of SSP2 self-assemblies. This work is beneficial for precisely controlling the structural parameters and controlled release function of SSP self-assemblies.

  12. Pressure-induced chemistry in a nitrogen-hydrogen host-guest structure

    NASA Astrophysics Data System (ADS)

    Spaulding, Dylan K.; Weck, Gunnar; Loubeyre, Paul; Datchi, Fréderic; Dumas, Paul; Hanfland, Michael

    2014-12-01

    New topochemistry in simple molecular systems can be explored at high pressure. Here we examine the binary nitrogen/hydrogen system using Raman spectroscopy, synchrotron X-ray diffraction, synchrotron infrared microspectroscopy and visual observation. We find a eutectic-type binary phase diagram with two stable high-pressure van der Waals compounds, which we identify as (N2)6(H2)7 and N2(H2)2. The former represents a new type of van der Waals host-guest compound in which hydrogen molecules are contained within channels in a nitrogen lattice. This compound shows evidence for a gradual, pressure-induced change in bonding from van der Waals to ionic interactions near 50 GPa, forming an amorphous dinitrogen network containing ionized ammonia in a room-temperature analogue of the Haber-Bosch process. Hydrazine is recovered on decompression. The nitrogen-hydrogen system demonstrates the potential for new pressure-driven chemistry in high-pressure structures and the promise of tailoring molecular interactions for materials synthesis.

  13. Host-Guest Binding-Site-Tunable Self-Assembly of Stimuli-Responsive Supramolecular Polymers.

    PubMed

    Yao, Hao; Qi, Miao; Liu, Yuyang; Tian, Wei

    2016-06-13

    Despite the remarkable progress made in controllable self-assembly of stimuli-responsive supramolecular polymers (SSPs), a basic issue that has not been consideration to date is the essential binding site. The noncovalent binding sites, which connect the building blocks and endow supramolecular polymers with their ability to respond to stimuli, are expected to strongly affect the self-assembly of SSPs. Herein, the design and synthesis of a dual-stimuli thermo- and photoresponsive Y-shaped supramolecular polymer (SSP2) with two adjacent β-cyclodextrin/azobenzene (β-CD/Azo) binding sites, and another SSP (SSP1) with similar building blocks, but only one β-CD/Azo binding site as a control, are described. Upon gradually increasing the polymer solution temperature or irradiating with UV light, SSP2 self-assemblies with a higher binding-site distribution density; exhibits a flower-like morphology, smaller size, and more stable dynamic aggregation process; and greater controllability for drug-release behavior than those observed with SSP1 self-assemblies. The host-guest binding-site-tunable self-assembly was attributed to the positive cooperativity generated among adjacent binding sites on the surfaces of SSP2 self-assemblies. This work is beneficial for precisely controlling the structural parameters and controlled release function of SSP self-assemblies. PMID:27167577

  14. Supramolecular Porphyrin Copolymer Assembled through Host-Guest Interactions and Metal-Ligand Coordination.

    PubMed

    Kinjo, Kanashi; Hirao, Takehiro; Kihara, Shin-ichi; Katsumoto, Yukiteru; Haino, Takeharu

    2015-12-01

    Bisporphyrin cleft molecule 1 Zn possessing a guest moiety assembled to form supramolecular polymers through host-guest interactions. Bispyridine cross-linkers created interchain connections among the supramolecular polymers to form networked polymers in solution. Solution viscometry confirmed that the cross-linked supramolecular polymers were highly entangled. Frequency-dependent linear viscoelastic spectroscopy revealed that the supramolecular polymers generated well-entangled solutions with associating and networking polymers, whereas the solid-like aggregates moved individually without breaking and reforming structures below the transition temperature of 9.6 °C. Morphological transition of the supramolecular polymers was evidenced by AFM images; the non-cross-linked polymer resulted in wide-spread thin networks, while the cross-linked networks produced thicker worm-like nanostructures. The supramolecular networks gelled in 1,1,2,2-tetrachloroethane, and an elastic free-standing film was fabricated with a Young's modulus of 1 GPa. PMID:26486784

  15. Recent advances in pillar[n]arenes: synthesis and applications based on host-guest interactions.

    PubMed

    Yang, Kui; Pei, Yuxin; Wen, Jia; Pei, Zhichao

    2016-07-19

    Pillar[n]arenes (n = 5-15) are a novel class of macrocyclic molecules with hydroquinone as the repeating unit linked by methylene bridges at para-positions. Introduced by T. Ogoshi for the first time in 2008, pillararenes have attracted increasing interest and have been widely studied during the last eight years, due to their unique structural advantages as host molecules, such as symmetrical rigid architecture, electron-rich cavities and facile functional modification. In this review, we first describe the syntheses of pillar[n]arenes including cyclooligomerization of pillar[n]arenes and modification of pillar[n]arenes after cyclooligomerization, summarising almost twenty different kinds of guest motifs and dividing them into three types: cationic, neutral and anionic motifs. The main section of this review examines the applications of pillar[n]arenes based on the host-guest interactions in different research fields, including biology, materials science and environmental science. Finally, future research directions and potential for novel applications are discussed. PMID:27332040

  16. Prediction of Host-Guest Na-Fe Intermetallics at High Pressures.

    PubMed

    Zhou, Yuanyuan; Wang, Hui; Zhu, Chunye; Liu, Hanyu; Tse, John S; Ma, Yanming

    2016-07-18

    High pressure can fundamentally alter the electronic structure of elemental metals, leading to the unexpected formation of intermetallics with unusual structural features. In the present study, the phase stabilities and structural changes of Na-Fe intermetallics under pressure were studied using unbiased structure searching methods, combined with density functional theory calculations. Two intermetallics with stoichiometries Na3Fe and Na4Fe are found to be thermodynamically stable at pressures above 120 and 155 GPa, respectively. An interesting structural feature is that both have form a host-guest-like structure with Na sublattices constructed from small and large polygons similar to the host framework of the self-hosting incommensurate phases observed in Group I and II elements. Apart from the one-dimensional (1D) Fe chains running through the large channels, more interestingly, electrides are found to localize in the small channels between the layers. Electron topological analysis shows secondary bonding interactions between the Fe atoms and the interstitial electrides help to stabilize these structures. PMID:27341197

  17. Cyclodextrin-modified zeolites: host-guest surface chemistry for the construction of multifunctional nanocontainers.

    PubMed

    Szarpak-Jankowska, Anna; Burgess, Christine; De Cola, Luisa; Huskens, Jurriaan

    2013-10-25

    The functionalization of nanoporous zeolite L crystals with β-cyclodextrin (CD) has been demonstrated. The zeolite surface was first modified with amino groups by using two different aminoalkoxysilanes. Then, 1,4-phenylene diisothiocyanate was reacted with the amino monolayer and used to bind CD heptamine by using its remaining isothiocyanate groups. The use of the different aminoalkoxysilanes, 3-aminopropyl dimethylethoxysilane (APDMES) and 3-aminopropyl triethoxysilane (APTES), led to drastic differences in uptake and release properties. Thionine was found to be absorbed and released from amino- and CD-functionalized zeolites when APDMES was used, whereas functionalization by APTES led to complete blockage of the zeolite channels. Fluorescence microscopy showed that the CD groups covalently attached to the zeolite crystals could bind adamantyl-modified dyes in a specific and reversible manner. This strategy allowed the specific immobilization of His-tagged proteins by using combined host-guest and His-tag-Ni-nitrilotriacetic acid (NTA) coordination chemistry. Such multifunctional systems have the potential for encapsulation of drug molecules inside the zeolite pores and non-covalent attachment of other (for example, targeting) ligand molecules on its surface.

  18. Pressure-induced chemistry in a nitrogen-hydrogen host-guest structure.

    PubMed

    Spaulding, Dylan K; Weck, Gunnar; Loubeyre, Paul; Datchi, Fréderic; Dumas, Paul; Hanfland, Michael

    2014-01-01

    New topochemistry in simple molecular systems can be explored at high pressure. Here we examine the binary nitrogen/hydrogen system using Raman spectroscopy, synchrotron X-ray diffraction, synchrotron infrared microspectroscopy and visual observation. We find a eutectic-type binary phase diagram with two stable high-pressure van der Waals compounds, which we identify as (N2)6(H2)7 and N2(H2)2. The former represents a new type of van der Waals host-guest compound in which hydrogen molecules are contained within channels in a nitrogen lattice. This compound shows evidence for a gradual, pressure-induced change in bonding from van der Waals to ionic interactions near 50 GPa, forming an amorphous dinitrogen network containing ionized ammonia in a room-temperature analogue of the Haber-Bosch process. Hydrazine is recovered on decompression. The nitrogen-hydrogen system demonstrates the potential for new pressure-driven chemistry in high-pressure structures and the promise of tailoring molecular interactions for materials synthesis. PMID:25484135

  19. Exploring host-guest complexation mechanisms by a molecular dynamics/quantum mechanics/continuum solvent model approach

    NASA Astrophysics Data System (ADS)

    Ye, Renlong; Nie, Xuemei; Zhou, Yumei; Wong, Chung F.; Gong, Xuedong; Jiang, Wei; Tang, Weihua; Wang, Yan A.; Heine, Thomas; Zhou, Baojing

    2016-03-01

    We introduce a molecular dynamics/quantum mechanics/continuum solvent model (MD/QM/CSM) approach to investigate binding mechanisms of host-guest systems. The representative conformations of host, guest, and their complex generated from MD simulations at the molecular-mechanics level are used for binding free energy calculations based on a QM/CSM model. We use this approach to explore the binding mechanisms of β-cyclodextrin (β-CD) and 2, 6-di-methyl-β-CD (DM-β-CD) with various guest molecules. Our results suggest that solvent effects play a more important role in determining the relative binding affinities of DM-β-CD than those of β-CD mainly because the former is more flexible than the latter.

  20. Molecular Recognition: Use of Metal-Containing Molecular Clefts for Supramolecular Self-Assembly and Host-Guest Formation

    SciTech Connect

    Crowley, James D.; Bosnich, Brice

    2008-10-03

    Molecular clefts consisting of a rigid spacer linked to two parallel cofacially disposed terpy-M-X (M = Pd{sup 2+}, Pt{sup 2+}) units, which can vary in separation from 6.6 to 7.2 {angstrom}, have been used as molecular receptors and for self-assembly with linear and triangular linkers to produce rectangles and trigonal prisms, respectively. Aromatic molecules form multiple host-guest adducts with the molecular cleft receptors and with the rectangles and trigonal prisms. Planar complexes of Pt{sup 2+} also form host-guest adducts. The forces that control this molecular recognition, namely, {pi}-{pi} interactions, charge-induced dipole interactions, charge-charge forces, weak metal-metal interactions and solvation effects, are discussed and assigned to the various adducts.

  1. Host-guest interactions mediated nano-assemblies using cyclodextrin-containing hydrophilic polymers and their biomedical applications

    PubMed Central

    Zhang, Jianxiang; Ma, Peter X

    2010-01-01

    Summary Supramolecular nanostructures assembled by polymeric amphiphiles have been intensively studied during the last two decades. Such nanocarriers may be engineered to possess on-demand bio-responsitivity for the prevention, diagnosis, and treatment of human diseases. The successful development of several nanoassembly-based polymer therapeutics further encouraged scientists to develop nano-vehicles to achieve controlled release, enhanced efficacy, improved specificity and reduced toxicity. Different from the abundant existing literatures on the hydrophobically or electrostatically driven self-assemblies and their therapeutic applications, this article reviews host-guest interaction mediated nanoassemblies, especially those constructed using cyclodextrins as the host entities. The excellent biocompatibility, complexation capacity, and chemical-sensitivity of cyclodextrin make cyclodextrin-containing polymers attractive to construct host-guest nanoassemblies. Such nanocarriers may be advantageous also because of the broad availability of cyclodextrins, their flexibility for structure/property modulation and their chemical-responsive characteristics. PMID:20725642

  2. Spectroscopic and Thermal Characterization of the Host-Guest Interactions between α-, β-, and γ-cyclodextrins and vanadocene dichloride

    PubMed Central

    Morales, Alexis; Weber, Ralph T.; Melendez, Enrique

    2009-01-01

    Host-guest interactions between α-, β-, and γ-cyclodextrins and vanadocene dichloride (Cp2VCl2) have been investigated by a combination of thermogravimetric analysis, differential scanning calorimeters, PXRD and solid state and solution EPR spectroscopy. The solid state results demonstrated that only β- and γ-cyclodextrins form 1:1 inclusion complexes, while α-cyclodextrin does not form an inclusion complex with Cp2VCl2. The β- and γ-CD-Cp2VCl2 inclusion complexes exhibited anisotropic electron-51V (I = 7/2) hyperfine coupling constants whereas the α-CD- Cp2VCl2 system showed only an asymmetric peak with no anisotropic hyperfine constant. On the other hand, solution EPR spectroscopy showed that α-CD may be involved in weak host-guest interactions in equilibrium with free vanadocene species. PMID:19881887

  3. Host-guest interaction induced supramolecular amphiphilic star architecture and uniform nanovesicle formation for anticancer drug delivery.

    PubMed

    Zhu, Jing-Ling; Liu, Kerh Li; Wen, Yuting; Song, Xia; Li, Jun

    2016-01-21

    A star polymer of poly[(R,S)-3-hydroxybutyrate] (PHB) with adamantyl end-terminals extended from an α-cyclodextrin (α-CD) core is designed. It subsequently self-assembles to form controllable and uniform nanovesicles induced by host-guest interactions between heptakis(2,6-di-O-methyl)-β-CD and the adamantyl ends. The nanovesicles are suitable for loading and intracellular delivery of the anticancer drug doxorubicin. PMID:26692041

  4. Host-guest supramolecular chemistry in solid-state nanopores: potassium-driven modulation of ionic transport in nanofluidic diodes

    NASA Astrophysics Data System (ADS)

    Pérez-Mitta, Gonzalo; Albesa, Alberto G.; Knoll, Wolfgang; Trautmann, Christina; Toimil-Molares, María Eugenia; Azzaroni, Omar

    2015-09-01

    We describe the use of asymmetric nanopores decorated with crown ethers for constructing robust signal-responsive chemical devices. The modification of single conical nanopores with 18-crown-6 units led to a nanodevice whose electronic readout, derived from the transmembrane ion current, can be finely tuned over a wide range of K+ concentrations. The electrostatic characteristics of the nanopore environment arising from host-guest ion-recognition processes taking place on the pore walls are responsible for tuning the transmembrane ionic transport and the rectification properties of the pore. This work illustrates the potential and versatility of host-guest chemistry, in combination with nanofluidic elements, as a key enabler to achieve addressable chemical nanodevices mimicking the ion transport properties and gating functions of specific biological channels.We describe the use of asymmetric nanopores decorated with crown ethers for constructing robust signal-responsive chemical devices. The modification of single conical nanopores with 18-crown-6 units led to a nanodevice whose electronic readout, derived from the transmembrane ion current, can be finely tuned over a wide range of K+ concentrations. The electrostatic characteristics of the nanopore environment arising from host-guest ion-recognition processes taking place on the pore walls are responsible for tuning the transmembrane ionic transport and the rectification properties of the pore. This work illustrates the potential and versatility of host-guest chemistry, in combination with nanofluidic elements, as a key enabler to achieve addressable chemical nanodevices mimicking the ion transport properties and gating functions of specific biological channels. Electronic supplementary information (ESI) available: Experimental details of the preparation and characterization of the brush-modified nanopores. See DOI: 10.1039/c5nr04645a

  5. Host-guest architectures with a surface confined imine covalent organic framework as two-dimensional host networks.

    PubMed

    Sun, Jiang; Zhou, Xin; Lei, Shengbin

    2016-07-01

    A two-dimensional covalent organic framework (2D COF), synthesized on a highly oriented pyrolytic graphite (HOPG) surface with benzene-1,3,5-tricarbaldehyde and p-phenylenediamine as the precursors, is used as a host to accommodate three guest molecules, coronene, copper phthalocyanine (CuPc), and fluorine-substituted copper phthalocyanine (F16CuPc). The host-guest interaction and dynamic behavior were investigated by scanning tunneling microscopy and density functional theory. PMID:27333296

  6. Modulating the rate of charge transport in a metal-organic framework thin film using host:guest chemistry.

    PubMed

    Hod, Idan; Farha, Omar K; Hupp, Joseph T

    2016-01-28

    Herein we demonstrate the use of host-guest chemistry to modulate rates of charge transport in metal-organic framework (MOF) films. The kinetics of site-to-site of charge hopping and, in turn, the overall redox conductivity, of a ferrocene-modified MOF can be altered by up to 30-fold by coupling electron exchange to the oxidation-state-dependent formation of inclusion complexes between cyclodextrin and channel-tethered metallocenes.

  7. Tuning Emission Responses of a Triphenylamine Derivative in Host-Guest Complexes and an Unusual Dynamic Inclusion Phenomenon.

    PubMed

    Gangopadhyay, Monalisa; Mandal, Amal K; Maity, Arunava; Ravindranathan, Sapna; Rajamohanan, Pattuparambil R; Das, Amitava

    2016-01-15

    A newly synthesized triphenylamine derivative (1Cl3) shows significant differences in inclusion complex formation with two different macrocyclic hosts, cucurbit[7]uril (CB[7]) and β-cyclodextrin (β-CD). Detailed investigations by NMR spectroscopy reveal that CB[7] forms a 1:3 host-guest complex ([1·3{CB[7]}]Cl3) in which three arms of 1Cl3 are bound to three host molecules. On the other hand, β-CD forms a dynamic 1:1 inclusion complex ([1·{β-CD}]Cl3) by binding to only one of the three arms of 1Cl3 at a given time. The formation of a 1:1 host-guest complex with β-CD and 1:3 host-guest complex with CB[7] was also confirmed from the results of the isothermal titration calorimetric studies. Interestingly, 1Cl3 exhibits a rare dual emission property in solution at room temperature with the lower and higher energy bands arising from a locally excited state and an intramolecular charge-transfer transition, respectively. The difference in inclusion complex formation behavior of 1Cl3 with the two macrocyclic hosts results in the stabilization of different emission states in the two inclusion complexes. The fundamental difference in the electrostatic surface potentials, cavity polarities, and shapes of the two macrocyclic hosts could account for the formation of the different inclusion complexes with distinct luminescence responses. PMID:26649441

  8. Cooperative Treatment of Metastatic Breast Cancer Using Host-Guest Nanoplatform Coloaded with Docetaxel and siRNA.

    PubMed

    Wang, Dangge; Wang, Tingting; Xu, Zhiai; Yu, Haijun; Feng, Bing; Zhang, Junying; Guo, Chengyue; Yin, Qi; Zhang, Zhiwen; Li, Yaping

    2016-01-27

    Conventional chemotherapy shows moderate efficiency against metastatic cancer since it targets only part of the mechanisms regulating tumor growth and metastasis. Here, gold nanorod (GNR)-based host-guest nanoplatforms loaded with docetaxel (DTX) and small interfering RNA (siRNA)-p65 (referred to as DTX-loaded GNR (GDTX)/p65) for chemo-, RNA interference (RNAi), and photothermal ablation (PTA) cooperative treatment of metastatic breast cancer are reported. To prepare the nanoplatform, GNRs are first coated with cyclodextrin (CD)-grafted polyethylenimine (PEI) and then loaded with DTX and siRNA through host-guest interaction with CD and electrostatic interaction with PEI, respectively. Upon near-infrared laser irradiation, GNRs generate a significant hyperthermia effect to trigger siRNA and DTX release. DTX reduces tumor growth by inhibiting mitosis of cancer cells. Meanwhile, siRNA-p65 suppresses lung metastasis and proliferation of cancer cells by blocking the nuclear factor kappa B (NF-κB) pathway and downregulating the downstream genes matrix metalloproteinase-9 (MMP-9) and B cell lymphoma-2 (Bcl-2). It is demonstrated that GDTX/p65 in combination with laser irradiation significantly inhibits the growth and lung metastasis of 4T1 breast tumors. The antitumor results suggest promising potential of the host-guest nanoplatform for combinational treatment of metastatic cancer by using RNAi, chemotherapy, and PTA. PMID:26662850

  9. Analysis of the nitrogen K-edge x-ray absorption spectra of Zn-porphyrin/C70-fulleren complex for solar cells

    NASA Astrophysics Data System (ADS)

    Suchkova, S. A.; Castellarin Cudia, C.; Soldatov, A.

    2009-11-01

    The atomic structure models of Zn-porphyrin/C70 multilayer for solar cells were examined. The local atomic structure of the Zn-porphyrin/C70 complex was refined with the use of previously published results [1]. Since near-edge spectral region (XANES) is sensitive to the three-dimensional atomic geometry, the theoretical analysis of the experimental XANES was performed on the basis of finite difference method (FDMnes 2008 program code). Some electronic properties of the complex were obtained from the DFT calculations performed by means of Amsterdam Density Functional program package.

  10. Host-guest inclusion complex of mesalazine and β-cyclodextrin and spectrofluorometric determination of mesalazine.

    PubMed

    Elbashir, Abdalla A; Altayib Alasha Abdalla, Fatima; Aboul-Enein, Hassan Y

    2015-06-01

    The supramolecular interaction of mesalazine (MSZ) and β-cyclodextrin (β-CD) has been examined by ultraviolet-visible (UV-vis) light, infra-red (IR) light and fluorescence spectroscopy. The formation of an inclusion complex has been confirmed based on the changes of the spectral properties. MSZ-β-CD host-guest complex was formed in (1:1) stoichiometry and the inclusion constant (K = 1.359 × 10(2)  L mol(-1) ) was ascertained by typical double reciprocal plots. Furthermore, the thermodynamic parameters (ΔG°, ΔH° and ΔS°) of (MSZ-β-CD) were obtained. Based on the remarkable enhancement of the fluorescence intensity of MSZ produced through complex formation, a simple, accurate, rapid and highly sensitive spectrofluorometric method for the determination of MSZ in aqueous solution in the presence of β-CD was developed. The measurement of relative fluorescence intensity was carried with excitation at 330 nm and emission 493 nm. All variables affecting the reactions were studied and optimized. Beer's law was obeyed in the concentration range 0.1-0.45 µg/mL. Absorbance was found to increase linearly with increasing concentration of MSZ, which is corroborated by the calculated correlation coefficient values of 0.99989. The molar absorptivity, Sandell's sensitivity, detection and quantification limits were calculated. The validity of the described methods was assessed, and the method was successfully applied to the determination of MSZ in its pharmaceutical formulation. In addition, a solid inclusion complex was synthesized by co-precipitation method.

  11. Host-Guest Self-Assembly Toward Reversible Thermoresponsive Switching for Bacteria Killing and Detachment.

    PubMed

    Shi, Zhen-Qiang; Cai, Yu-Ting; Deng, Jie; Zhao, Wei-Feng; Zhao, Chang-Sheng

    2016-09-14

    A facile method to construct reversible thermoresponsive switching for bacteria killing and detachment was currently developed by host-guest self-assembly of β-cyclodextrin (β-CD) and adamantane (Ad). Ad-terminated poly(N-isopropylacrylamide) (Ad-PNIPAM) and Ad-terminated poly[2-(methacryloyloxy)ethyl]trimethylammonium chloride (Ad-PMT) were synthesized via atom transfer radical polymerization, and then assembled onto the surface of β-CD grafted silicon wafer (SW-CD) by simply immersing SW-CD into a mixed solution of Ad-PNIPAM and Ad-PMT, thus forming a thermoresponsive surface (SW-PNIPAM/PMT). Atomic force microscopy (AFM), X-ray photoelectron spectrometry (XPS), and water contact angle (WCA) analysis were used to characterize the surface of SW-PNIPAM/PMT. The thermoresponsive bacteria killing and detachment switch of the SW-PNIPAM/PMT was investigated against Staphyloccocus aureus. The microbiological experiments confirmed the efficient bacteria killing and detachment switch across the lower critical solution temperature (LCST) of PNIPAM. Above the LCST, the Ad-PNIPAM chains on the SW-PNIPAM/PMT surface were collapsed to expose Ad-PMT chains, and then the exposed Ad-PMT would kill the attached bacteria. While below the LCST, the previously collapsed Ad-PNIPAM chains became more hydrophilic and swelled to cover the Ad-PMT chains, leading to the detachment of bacterial debris. Besides, the proposed method to fabricate stimuli-responsive surfaces with reversible switches for bacteria killing and detachment is facile and efficient, which creates a new route to extend the application of such smart surfaces in the fields requiring long-term antimicrobial treatment. PMID:27552087

  12. The synthesis and host-guest applications of synthetic receptor molecules

    NASA Astrophysics Data System (ADS)

    Osner, Zachary R.

    2011-12-01

    Host-guest chemistry involves the complimentary binding between two molecules. Host molecules have been synthesized to bind negative, positive, and neutral molecules such as proteins and enzymes, and have been used as optical sensors, electrochemical sensors, supramolecular catalysts, and in the pharmaceutical industry as anti-cancer agents.1 The field of nanoscience has exploited guest-host interactions to create optical sensors with colloidal gold and Dip-Pen nanolithography technologies. Gold nanoparticles, have been functionalized with DNA, and have been developed as a selective colorimetric detection system, that upon binding turns the solution from a red to blue in color.2 Cyclotriveratrylene (CTV) 1 is a common supramolecular scaffold that has been previously employed in guest-host chemistry, and the construction of CTV involves the cyclic trimerization of veratryl alcohol via the veratryl cation.3 Due to the rigid bowl shaped structure of CTV, CTV has been shown to act as a host molecule for fullerene-C60.4 Lectin binding receptor proteins are a specific class of proteins found in bacteria, viruses, plants, and animals that can bind to complimentary carbohydrates. It is these lectins that are believed to be responsible for cell-cell interactions and the formation of biofilms in pathenogenic bacteria.5 P. aeruginosa is a pathenogenic bacterium, shown to have a high resistance to many antibiotics, which can form biofilms in human lung tissue, causing respiratory tract infections in patients with compromised immune systems. 5 I will exploit guest-host interactions to create synthetic supramolecular and carbohydrate receptor molecules to that will be of use as biological sensing devices via self-assembled monolayers on solid surfaces and nanoparticle technologies. *Please refer to dissertation for references/footnotes.

  13. Computational Calorimetry: High-Precision Calculation of Host-Guest Binding Thermodynamics.

    PubMed

    Henriksen, Niel M; Fenley, Andrew T; Gilson, Michael K

    2015-09-01

    We present a strategy for carrying out high-precision calculations of binding free energy and binding enthalpy values from molecular dynamics simulations with explicit solvent. The approach is used to calculate the thermodynamic profiles for binding of nine small molecule guests to either the cucurbit[7]uril (CB7) or β-cyclodextrin (βCD) host. For these systems, calculations using commodity hardware can yield binding free energy and binding enthalpy values with a precision of ∼0.5 kcal/mol (95% CI) in a matter of days. Crucially, the self-consistency of the approach is established by calculating the binding enthalpy directly, via end point potential energy calculations, and indirectly, via the temperature dependence of the binding free energy, i.e., by the van't Hoff equation. Excellent agreement between the direct and van't Hoff methods is demonstrated for both host-guest systems and an ion-pair model system for which particularly well-converged results are attainable. Additionally, we find that hydrogen mass repartitioning allows marked acceleration of the calculations with no discernible cost in precision or accuracy. Finally, we provide guidance for accurately assessing numerical uncertainty of the results in settings where complex correlations in the time series can pose challenges to statistical analysis. The routine nature and high precision of these binding calculations opens the possibility of including measured binding thermodynamics as target data in force field optimization so that simulations may be used to reliably interpret experimental data and guide molecular design.

  14. UV photodissociation spectroscopy of cryogenically cooled gas phase host-guest complex ions of crown ethers.

    PubMed

    Inokuchi, Yoshiya; Haino, Takeharu; Sekiya, Ryo; Morishima, Fumiya; Dedonder, Claude; Féraud, Géraldine; Jouvet, Christophe; Ebata, Takayuki

    2015-10-21

    The geometric and electronic structures of cold host-guest complex ions of crown ethers (CEs) in the gas phase have been investigated by ultraviolet (UV) fragmentation spectroscopy. As host CEs, we chose 15-crown-5 (15C5), 18-crown-6 (18C6), 24-crown-8 (24C8), and dibenzo-24-crown-8 (DB24C8), and as guests protonated-aniline (aniline·H(+)) and protonated-dibenzylamine (dBAM·H(+)) were chosen. The ions generated by an electrospray ionization (ESI) source were cooled in a quadrupole ion-trap (QIT) using a cryogenic cooler, and UV spectra were obtained by UV photodissociation (UVPD) spectroscopy. UV spectroscopy was complemented by quantum chemical calculations of the most probable complex structures. The UV spectrum of aniline·H(+)·CEs is very sensitive to the symmetry of CEs; aniline·H(+)·18C6 shows a sharp electronic spectrum similar to aniline·H(+), while aniline·H(+)·15C5 shows a very broad structure with poor Franck-Condon factors. In addition, a remarkable cage effect in the fragmentation process after UV excitation was observed in both complex ions. In aniline·H(+)·CE complexes, the cage effect completely removed the dissociation channels of the aniline·H(+) moiety. A large difference in the fragmentation yield between dBAM·H(+)·18C6 and dBAM·H(+)·24C8 was observed due to a large barrier for releasing dBAM·H(+) from the axis of rotaxane in the latter complex.

  15. Formation of host-guest complexes of β-cyclodextrin and perfluorooctanoic acid.

    PubMed

    Karoyo, Abdalla H; Borisov, Alex S; Wilson, Lee D; Hazendonk, Paul

    2011-08-11

    Structural characterization and dynamic properties of solid-state inclusion complexes of β-cyclodextrin (β-CD) with perfluorooctanoic acid (PFOA) were investigated by (19)F/(13)C solid-state and (19)F/(1)H solution NMR spectroscopy. The complexes in the solid state were prepared using dissolution and slow cool methods, where thermal analyses (DSC and TGA), PXRD, and FT-IR results provided complementary support that inclusion complexes were formed between β-CD and PFOA with variable stoichiometry and inclusion geometry. (19)F DP (direct polarization) and (13)C CP (cross-polarization) with magic-angle spinning (MAS) solids NMR, along with (19)F/(1)H solution NMR were used to characterize the complexes in the solid and solution phases, respectively. The dynamics of the guest molecules in the inclusion complexes (ICs) were studied using variable temperature (VT) (19)F DP/MAS NMR experiments in the solid state. The guest molecules were observed to be in several different molecular environments, providing strong evidence of variable host-guest stoichiometry and inclusion geometry, in accordance with the preparation method of the complex and the conformational preference of PFOA. It was concluded from PXRD that β-CD and PFOA form inclusion complexes with "channel-type" structures. Variable spin rate (VSR) (19)F DP/MAS NMR was used to assess the phase purity of the complexes, and it was revealed that slow cooling resulted in relatively pure phases. In the solution state, (1)H and (19)F NMR complexation-induced chemical shifts (CISs) of β-CD and PFOA, respectively, provided strong support for the formation of 1:1 and 2:1 β-CD/PFOA inclusion complexes. The dynamics of the guest molecule in the β-CD/PFOA complexes in D(2)O solutions were probed using VT (19)F NMR and revealed some guest conformational and exchange dynamics as a function of temperature and the relative concentrations of the host and guest. PMID:21688796

  16. Prediction of SAMPL3 host-guest binding affinities: evaluating the accuracy of generalized force-fields.

    PubMed

    Muddana, Hari S; Gilson, Michael K

    2012-05-01

    We used the second-generation mining minima method (M2) to compute the binding affinities of the novel host-guest complexes in the SAMPL3 blind prediction challenge. The predictions were in poor agreement with experiment, and we conjectured that much of the error might derive from the force field, CHARMm with Vcharge charges. Repeating the calculations with other generalized force-fields led to no significant improvement, and we observed that the predicted affinities were highly sensitive to the choice of force-field. We therefore embarked on a systematic evaluation of a set of generalized force fields, based upon comparisons with PM6-DH2, a fast yet accurate semi-empirical quantum mechanics method. In particular, we compared gas-phase interaction energies and entropies for the host-guest complexes themselves, as well as for smaller chemical fragments derived from the same molecules. The mean deviations of the force field interaction energies from the quantum results were greater than 3 kcal/mol and 9 kcal/mol, for the fragments and host-guest systems respectively. We further evaluated the accuracy of force-fields for computing the vibrational entropies and found the mean errors to be greater than 4 kcal/mol. Given these errors in energy and entropy, it is not surprising in retrospect that the predicted binding affinities deviated from the experiment by several kcal/mol. These results emphasize the need for improvements in generalized force-fields and also highlight the importance of systematic evaluation of force-field parameters prior to evaluating different free-energy methods.

  17. Cyclodextrin type dependent host-guest interaction mode with phthalocyanine and their influence on photodynamic activity to cancer.

    PubMed

    Lu, S; Wang, A; Ma, Y J; Xuan, H Y; Zhao, B; Li, X D; Zhou, J H; Zhou, L; Wei, S H

    2016-09-01

    Three host-guest complexes of phthalocyanines (Pc) with α-, β- or γ-cyclodextrins (CDs) were prepared and their interaction modes, reactive oxygen species (ROSs) generation ability and in vitro anticancer activities were studied and compared. After forming complex with CD, the aggregation degree of Pc was greatly decreased and the water solubility and photodynamic activity was sharply increased. Computer modeling results indicated that the interaction modes between Pc and CDs were varied with different kinds of CD. Especially, the complex of Pc and β-CD has superior stability, ROSs generation ability, and anticancer activity to other complexes.

  18. Smart protein biogate as a mediator to regulate competitive host-guest interaction for sensitive ratiometric electrochemical assay of prion.

    PubMed

    Yu, Peng; Zhang, Xiaohua; Zhou, Jiawan; Xiong, Erhu; Li, Xiaoyu; Chen, Jinhua

    2015-01-01

    A novel competitive host-guest strategy regulated by protein biogate was developed for sensitive and selective analysis of prion protein. The methylene blue (MB)-tagged prion aptamer (MB-Apt) was introduced to the multiwalled carbon nanotubes-β-cyclodextrins (MWCNTs-β-CD) composites-modified glassy carbon (GC) electrode through the host-guest interaction between β-CD and MB. In the absence of prion, MB-Apt could be displaced by ferrocenecarboxylic acid (FCA) due to its stronger binding affinity to β-CD, resulting in a large oxidation peak of FCA. However, in the presence of prion, the specific prion-aptamer interaction drove the formation of protein biogate to seal the cavity of β-CD, which hindered the guest displacement of MB by FCA and resulted in the oxidation peak current of MB (IMB) increased and that of FCA (IFCA) decreased. The developed aptasensor showed good response towards the target (prion protein) with a low detection limit of 160 fM. By changing the specific aptamers, this strategy could be easily extended to detect other proteins, showing promising potential for extensive applications in bioanalysis.

  19. Host-Guest Inclusion Complexation of α-Cyclodextrin and Triiodide Examined Using UV-Vis Spectrophotometry.

    PubMed

    Pursell, Janet L; Pursell, Christopher J

    2016-04-01

    The historically relevant host-guest complexation of α-cyclodextrin (α-CD) and triiodide (I3(-)) in aqueous solution was examined using a systematic UV-vis spectrophotometric approach. This particular system is experimentally challenging because of the coupled equilibria, namely, I2 + I(-) ⇌ I3(-) and α-CD + I3(-) ⇌ α-CD·I3(-). We therefore developed a unique experimental approach that allowed us to determine the concentration of all iodine species. This enabled us to unequivocally demonstrate that the large increase in the UV absorbance with added α-cyclodextrin is due to an increase in the overall triiodide concentration as α-CD essentially converts iodine to triiodide according to the coupled equilibria. Herein we report (a) the complexation stoichiometry is 1:1 (i.e., the host-guest complex is α-CD·I3(-)), (b) the binding constant is KH-G = (1.35 ± 0.05) × 10(5) M(-1) at room temperature, and PMID:26997285

  20. Tunable Two-color Luminescence and Host-guest Energy Transfer of Fluorescent Chromophores Encapsulated in Metal-Organic Frameworks

    NASA Astrophysics Data System (ADS)

    Yan, Dongpeng; Tang, Yanqun; Lin, Heyang; Wang, Dan

    2014-03-01

    Co-assembly of chromophore guests with host matrices can afford materials which have photofunctionalities different from those of individual components. Compared with clay and zeolite materials, the use of metal-organic frameworks (MOFs) as a host structure for fabricating luminescent host-guest materials is still at an early stage. Herein, we report the incorporation of a laser dye, 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM), into stilbene-based and naphthalene-based MOF systems. The resulting materials exhibit blue/red two-color emission, and the intensity ratio of blue to red fluorescence varies in different planes within the MOF crystal as detected by 3D confocal fluorescence microscopy. The observed changes in ratiometric fluorescence suggest the occurrence of energy transfer from MOF host to DCM molecules, which can be further confirmed by periodic density functional theoretical (DFT) calculations. Moreover, selective changes in luminescence behavior are observed on treating the guest@MOF samples with volatile organic compounds (methanol, acetone and toluene), indicating that these host-guest systems have potential applications as fluorescence sensors. It can be expected that by rational selection of MOF hosts and guest chromophores with suitable emissive colors and energy levels, a wide variety of multi-color luminescent and energy-transfer systems can readily be prepared in a similar manner.

  1. Supramolecular Thermo-Electrochemical Cells: Enhanced Thermoelectric Performance by Host-Guest Complexation and Salt-Induced Crystallization.

    PubMed

    Zhou, Hongyao; Yamada, Teppei; Kimizuka, Nobuo

    2016-08-24

    Thermo-electrochemical cells have potential to generate thermoelectric voltage 1 order higher than that given by semiconductor materials. To overcome the current issues in thermoelectric energy conversion, it is of paramount importance to grow and fulfill the full potential of thermo-electrochemical cells. Here we report a rational supramolecular methodology that yielded the highest Seebeck coefficient of ca. 2.0 mV K(-1) around ambient temperatures. This is based on the encapsulation of triiodide ions in α-cyclodextrin, whose equilibrium is shifted to the complexation at lower temperatures, whereas it is inverted at elevated temperatures. This temperature-dependent host-guest interaction provides a concentration gradient of redox ion pairs between two electrodes, leading to the eminent performance of the thermo-electrochemical cells. The figure of merit for this system, zT reached a high value of 5 × 10(-3). The introduction of host-guest chemistry to thermoelectric cells thus provides a new perspective in thermoelectric energy conversion. PMID:27508406

  2. Supramolecular host-guest polycationic gene delivery system based on poly(cyclodextrin) and azobenzene-terminated polycations.

    PubMed

    Jiang, Qimin; Zhang, Yunti; Zhuo, Renxi; Jiang, Xulin

    2016-11-01

    This article describes the supramolecular host-guest polycationic gene delivery system based on poly(β-cyclodextrin) (PCD) and azobenzene-terminated polycations. The azobenzene-terminated linear (Az-LPDM) and branched (Az-BPDM) cationic polymers were synthesized by atom transfer radical polymerization (ATRP) of 2-dimethylamino ethyl methacrylate (DMAEMA). The formation and photosensitive behavior of the supramolecular polycations of azobenzene-terminated polycations Az-LPDM and Az-BPDM with PCD were confirmed by UV-vis and NMR analysis. The supramolecular PCD/Az-BPDM/DNA and PCD/Az-LPDM/DNA polyplexes showed smaller size and were less positive than those of their corresponding polyplexes without PCD. Moreover, the UV irradiation may promote release of DNA from the photosensitive supramolecular polyplexes due to dissociation of supramoelcular polyplexes. In vitro experiments revealed that the photosensitive supramolecular polycationic polyplexes (PCD/Az-LPDM/DNA and PCD/Az-BPDM/DNA) exhibited enhancement of cellular uptake, higher transfection efficiency, and lower cytoxicity compared to the azobenzene-terminated polycation/DNA polyplexes in the absence of PCD. Branched polycationic polyplexes showed higher transfection efficiency than its linear polycationic polyplexes. Furthermore, after UV irradiation, the transfection efficiency of photosensitive supramolecular polyplexes was improved resulting from more DNAs delivered and released inside of the cell nuclei. Thus this photoresponsive supramolecular host-guest system containing azobenzene-terminated branched cationic polymers and PCD is a promising gene vector. PMID:27478960

  3. Host-guest interaction induced supramolecular amphiphilic star architecture and uniform nanovesicle formation for anticancer drug delivery

    NASA Astrophysics Data System (ADS)

    Zhu, Jing-Ling; Liu, Kerh Li; Wen, Yuting; Song, Xia; Li, Jun

    2016-01-01

    A star polymer of poly[(R,S)-3-hydroxybutyrate] (PHB) with adamantyl end-terminals extended from an α-cyclodextrin (α-CD) core is designed. It subsequently self-assembles to form controllable and uniform nanovesicles induced by host-guest interactions between heptakis(2,6-di-O-methyl)-β-CD and the adamantyl ends. The nanovesicles are suitable for loading and intracellular delivery of the anticancer drug doxorubicin.A star polymer of poly[(R,S)-3-hydroxybutyrate] (PHB) with adamantyl end-terminals extended from an α-cyclodextrin (α-CD) core is designed. It subsequently self-assembles to form controllable and uniform nanovesicles induced by host-guest interactions between heptakis(2,6-di-O-methyl)-β-CD and the adamantyl ends. The nanovesicles are suitable for loading and intracellular delivery of the anticancer drug doxorubicin. Electronic supplementary information (ESI) available: Polymer synthesis, characterization, preparation of drug-loaded nanovesicles, intracellular drug release and cytotoxicity assays, TEM and DLS measurements. See DOI: 10.1039/c5nr06744h

  4. Supramolecular Thermo-Electrochemical Cells: Enhanced Thermoelectric Performance by Host-Guest Complexation and Salt-Induced Crystallization.

    PubMed

    Zhou, Hongyao; Yamada, Teppei; Kimizuka, Nobuo

    2016-08-24

    Thermo-electrochemical cells have potential to generate thermoelectric voltage 1 order higher than that given by semiconductor materials. To overcome the current issues in thermoelectric energy conversion, it is of paramount importance to grow and fulfill the full potential of thermo-electrochemical cells. Here we report a rational supramolecular methodology that yielded the highest Seebeck coefficient of ca. 2.0 mV K(-1) around ambient temperatures. This is based on the encapsulation of triiodide ions in α-cyclodextrin, whose equilibrium is shifted to the complexation at lower temperatures, whereas it is inverted at elevated temperatures. This temperature-dependent host-guest interaction provides a concentration gradient of redox ion pairs between two electrodes, leading to the eminent performance of the thermo-electrochemical cells. The figure of merit for this system, zT reached a high value of 5 × 10(-3). The introduction of host-guest chemistry to thermoelectric cells thus provides a new perspective in thermoelectric energy conversion.

  5. Host guest inclusion complexes of four partial alkyl-substituted cucurbit[6]urils with some probe guests

    NASA Astrophysics Data System (ADS)

    Yu, Da-Hai; Ni, Xin-Long; Tian, Zhong-Cheng; Zhang, Yun-Qin; Xue, Sai-Feng; Tao, Zhu; Zhu, Qing-Jiang

    2008-11-01

    Using probe guests, three host-guest inclusion complexes of two new alkyl-substituted cucurbit[6]uril hosts, ortho-tetramethyl cucurbit[6]uril ( o-TMeQ[6]) and symmetrical tetracyclohexano cucurbit[6]uril (TCyHQ[6]) have been characterized successfully by single crystal X-ray diffractions. They are { o-TMeQ[6]-5,5'dimethyl-2,2'-bispyridine ( DMBPY) +}Cl -21H 2O( 1), {( o-TMeQ[6]) 2-1,6-bisbenzoimidazolylhexane ( SBH) 2+} 2Cl -52H 2O ( 2) and {TCyHQ[6]- dioxane}14H 2O ( 3). Moreover, two similar crystal structure of two inclusion complexes of other two partial substituted cucurbit[6]urils, meta-hexamethyl cucurbit[6]uril ( m-HMeQ[6]) and symmetrical dicyclohexano cucurbit[6]uril ( p-(CyH) 2Q[6]) with HCl salt of DMBPY were also reported. They were { p-(CyH) 2Q[6]- DMBPY+}Cl -16H 2O ( 4) and { m-HMeQ[6]- DMBPY+}Cl -15H 2O ( 5). The driving force for the information of the host-guest inclusion complexes can be attributed to not only the cavity interaction (host), but also the hydrogen bonding and ion-dipole interaction between the carbonyl oxygen at the portals of the host and the protonated nitrogen of the guest.

  6. Sequential energy and charge transfer processes in mixed host-guest complexes of subphthalocyanine, porphyrin and phthalocyanine chromophores.

    PubMed

    Menting, Roel; Ng, Dennis K P; Röder, Beate; Ermilov, Eugeny A

    2012-11-14

    Porphyrins, phthalocyanines and subphthalocyanines are three attractive classes of chromophores with intriguing properties making them suitable for the design of artificial photosynthetic systems. The assembly of these components by a supramolecular approach is of particular interest as it provides a facile means to build multi-chromophoric arrays with various architectures and tuneable photophysical properties. In this paper, we show the formation of mixed host-guest supramolecular complexes that consist of a β-cyclodextrin-conjugated subphthalocyanine, a tetrasulfonated porphyrin and a series of silicon(IV) phthalocyanines substituted axially with two β-cyclodextrins via different spacers. We found that the three components form supramolecular complexes held by host-guest interactions in aqueous solution. Upon excitation of the subphthalocyanine part of the complex, the excitation energy is delivered to the phthalocyanine unit via excitation energy transfer and the porphyrin chromophore acts as an energy transfer bridge enabling this process. It was shown that photo-induced charge transfer also takes place. A sequential electron transfer process from the porphyrin unit to the phthalocyanine moiety and subsequently from the subphthalocyanine moiety to the porphyrin unit takes place, and the probability of this process is controlled by the linker between β-cyclodextrin and phthalocyanine. The lifetime of the charge-separated state was found to be 1.7 ns by transient absorption spectroscopy.

  7. Light-triggered capture and release of DNA and proteins by host-guest binding and electrostatic interaction.

    PubMed

    Moratz, Johanna; Samanta, Avik; Voskuhl, Jens; Mohan Nalluri, Siva Krishna; Ravoo, Bart Jan

    2015-02-16

    The development of an effective and general delivery method that can be applied to a large variety of structurally diverse biomolecules remains a bottleneck in modern drug therapy. Herein, we present a supramolecular system for the dynamic trapping and light-stimulated release of both DNA and proteins. Self-assembled ternary complexes act as nanoscale carriers, comprising vesicles of amphiphilic cyclodextrin, the target biomolecules and linker molecules with an azobenzene unit and a charged functionality. The non-covalent linker binds to the cyclodextrin by host-guest complexation with the azobenzene. Proteins or DNA are then bound to the functionalized vesicles through multivalent electrostatic attraction. The photoresponse of the host-guest complex allows a light-induced switch from the multivalent state that can bind the biomolecules to the low-affinity state of the free linker, thereby providing external control over the cargo release. The major advantage of this delivery approach is the wide variety of targets that can be addressed by multivalent electrostatic interaction, which we demonstrate on four types of DNA and six different proteins. PMID:25585879

  8. A pH-Responsive Host-guest Nanosystem Loading Succinobucol Suppresses Lung Metastasis of Breast Cancer

    PubMed Central

    Dan, Zhaoling; Cao, Haiqiang; He, Xinyu; Zhang, Zhiwen; Zou, Lili; Zeng, Lijuan; Xu, Yan; Yin, Qi; Xu, Minghua; Zhong, Dafang; Yu, Haijun; Shen, Qi; Zhang, Pengcheng; Li, Yaping

    2016-01-01

    Cancer metastasis is the leading reason for the high mortality of breast cancer. Herein, we report on a pH-responsive host-guest nanosystem of succinobucol (PHN) with pH-stimuli controlled drug release behavior to improve the therapeutic efficacy on lung metastasis of breast cancer. PHN was composed of the host polymer of β-cyclodextrin linked with multiple arms of N,N-diisopropylethylenediamine (βCD-DPA), the guest polymer of adamantyl end-capped methoxy poly(ethylene glycol) (mPEG-Ad), and the active agent of succinobucol. PHN comprises nanometer-sized homogenous spherical particles, and exhibits specific and rapid drug release in response to the intracellular acidic pH-stimuli. Then, the anti-metastatic efficacy of PHN is measured in metastatic 4T1 breast cancer cells, which effectively confirms the superior inhibitory effects on cell migration and invasion activities, VCAM-1 expression and cell-cell binding of RAW 264.7 to 4T1 cells. Moreover, PHN can be specifically delivered to the sites of metastatic nodules in lungs, and result in an obviously improved therapeutic efficacy on lung metastasis of breast cancer. Thereby, the pH-responsive host-guest nanosystem can be a promising drug delivery platform for effective treatment of cancer metastasis. PMID:26909117

  9. Smart protein biogate as a mediator to regulate competitive host-guest interaction for sensitive ratiometric electrochemical assay of prion

    PubMed Central

    Yu, Peng; Zhang, Xiaohua; Zhou, Jiawan; Xiong, Erhu; Li, Xiaoyu; Chen, Jinhua

    2015-01-01

    A novel competitive host-guest strategy regulated by protein biogate was developed for sensitive and selective analysis of prion protein. The methylene blue (MB)-tagged prion aptamer (MB-Apt) was introduced to the multiwalled carbon nanotubes-β-cyclodextrins (MWCNTs-β-CD) composites-modified glassy carbon (GC) electrode through the host-guest interaction between β-CD and MB. In the absence of prion, MB-Apt could be displaced by ferrocenecarboxylic acid (FCA) due to its stronger binding affinity to β-CD, resulting in a large oxidation peak of FCA. However, in the presence of prion, the specific prion-aptamer interaction drove the formation of protein biogate to seal the cavity of β-CD, which hindered the guest displacement of MB by FCA and resulted in the oxidation peak current of MB (IMB) increased and that of FCA (IFCA) decreased. The developed aptasensor showed good response towards the target (prion protein) with a low detection limit of 160 fM. By changing the specific aptamers, this strategy could be easily extended to detect other proteins, showing promising potential for extensive applications in bioanalysis. PMID:26531259

  10. Responsive supramolecular polymer metallogel constructed by orthogonal coordination-driven self-assembly and host/guest interactions.

    PubMed

    Yan, Xuzhou; Cook, Timothy R; Pollock, J Bryant; Wei, Peifa; Zhang, Yanyan; Yu, Yihua; Huang, Feihe; Stang, Peter J

    2014-03-26

    An emerging strategy for the fabrication of advanced supramolecular materials is the use of hierarchical self-assembly techniques wherein multiple orthogonal interactions between molecular precursors can produce new species with attractive properties. Herein, we unify the spontaneous formation of metal-ligand bonds with the host/guest chemistry of crown ethers to deliver a 3D supramolecular polymer network (SPN). Specifically, we have prepared a highly directional dipyridyl donor decorated with a benzo-21-crown-7 moiety that undergoes coordination-driven self-assembly with a complementary organoplatinum acceptor to furnish hexagonal metallacycles. These hexagons subsequently polymerize into a supramolecular network upon the addition of a bisammonium salt due to the formation of [2]pseudorotaxane linkages between the crown ether and ammonium moieties. At high concentrations, the resulting 3D SPN becomes a gel comprising many cross-linked metallohexagons. Notably, thermo- and cation-induced gel-sol transitions are found to be completely reversible, reflecting the dynamic and tunable nature of such supramolecular materials. As such, these results demonstrate the structural complexity that can be obtained when carefully controlling multiple interactions in a hierarchical fashion, in this case coordination and host/guest chemistry, and the interesting dynamic properties associated with the materials thus obtained. PMID:24621148

  11. Smart protein biogate as a mediator to regulate competitive host-guest interaction for sensitive ratiometric electrochemical assay of prion

    NASA Astrophysics Data System (ADS)

    Yu, Peng; Zhang, Xiaohua; Zhou, Jiawan; Xiong, Erhu; Li, Xiaoyu; Chen, Jinhua

    2015-11-01

    A novel competitive host-guest strategy regulated by protein biogate was developed for sensitive and selective analysis of prion protein. The methylene blue (MB)-tagged prion aptamer (MB-Apt) was introduced to the multiwalled carbon nanotubes-β-cyclodextrins (MWCNTs-β-CD) composites-modified glassy carbon (GC) electrode through the host-guest interaction between β-CD and MB. In the absence of prion, MB-Apt could be displaced by ferrocenecarboxylic acid (FCA) due to its stronger binding affinity to β-CD, resulting in a large oxidation peak of FCA. However, in the presence of prion, the specific prion-aptamer interaction drove the formation of protein biogate to seal the cavity of β-CD, which hindered the guest displacement of MB by FCA and resulted in the oxidation peak current of MB (IMB) increased and that of FCA (IFCA) decreased. The developed aptasensor showed good response towards the target (prion protein) with a low detection limit of 160 fM. By changing the specific aptamers, this strategy could be easily extended to detect other proteins, showing promising potential for extensive applications in bioanalysis.

  12. Supramolecular host-guest polycationic gene delivery system based on poly(cyclodextrin) and azobenzene-terminated polycations.

    PubMed

    Jiang, Qimin; Zhang, Yunti; Zhuo, Renxi; Jiang, Xulin

    2016-11-01

    This article describes the supramolecular host-guest polycationic gene delivery system based on poly(β-cyclodextrin) (PCD) and azobenzene-terminated polycations. The azobenzene-terminated linear (Az-LPDM) and branched (Az-BPDM) cationic polymers were synthesized by atom transfer radical polymerization (ATRP) of 2-dimethylamino ethyl methacrylate (DMAEMA). The formation and photosensitive behavior of the supramolecular polycations of azobenzene-terminated polycations Az-LPDM and Az-BPDM with PCD were confirmed by UV-vis and NMR analysis. The supramolecular PCD/Az-BPDM/DNA and PCD/Az-LPDM/DNA polyplexes showed smaller size and were less positive than those of their corresponding polyplexes without PCD. Moreover, the UV irradiation may promote release of DNA from the photosensitive supramolecular polyplexes due to dissociation of supramoelcular polyplexes. In vitro experiments revealed that the photosensitive supramolecular polycationic polyplexes (PCD/Az-LPDM/DNA and PCD/Az-BPDM/DNA) exhibited enhancement of cellular uptake, higher transfection efficiency, and lower cytoxicity compared to the azobenzene-terminated polycation/DNA polyplexes in the absence of PCD. Branched polycationic polyplexes showed higher transfection efficiency than its linear polycationic polyplexes. Furthermore, after UV irradiation, the transfection efficiency of photosensitive supramolecular polyplexes was improved resulting from more DNAs delivered and released inside of the cell nuclei. Thus this photoresponsive supramolecular host-guest system containing azobenzene-terminated branched cationic polymers and PCD is a promising gene vector.

  13. Responsive supramolecular polymer metallogel constructed by orthogonal coordination-driven self-assembly and host/guest interactions.

    PubMed

    Yan, Xuzhou; Cook, Timothy R; Pollock, J Bryant; Wei, Peifa; Zhang, Yanyan; Yu, Yihua; Huang, Feihe; Stang, Peter J

    2014-03-26

    An emerging strategy for the fabrication of advanced supramolecular materials is the use of hierarchical self-assembly techniques wherein multiple orthogonal interactions between molecular precursors can produce new species with attractive properties. Herein, we unify the spontaneous formation of metal-ligand bonds with the host/guest chemistry of crown ethers to deliver a 3D supramolecular polymer network (SPN). Specifically, we have prepared a highly directional dipyridyl donor decorated with a benzo-21-crown-7 moiety that undergoes coordination-driven self-assembly with a complementary organoplatinum acceptor to furnish hexagonal metallacycles. These hexagons subsequently polymerize into a supramolecular network upon the addition of a bisammonium salt due to the formation of [2]pseudorotaxane linkages between the crown ether and ammonium moieties. At high concentrations, the resulting 3D SPN becomes a gel comprising many cross-linked metallohexagons. Notably, thermo- and cation-induced gel-sol transitions are found to be completely reversible, reflecting the dynamic and tunable nature of such supramolecular materials. As such, these results demonstrate the structural complexity that can be obtained when carefully controlling multiple interactions in a hierarchical fashion, in this case coordination and host/guest chemistry, and the interesting dynamic properties associated with the materials thus obtained.

  14. Tunable two-color luminescence and host-guest energy transfer of fluorescent chromophores encapsulated in metal-organic frameworks.

    PubMed

    Yan, Dongpeng; Tang, Yanqun; Lin, Heyang; Wang, Dan

    2014-03-11

    Co-assembly of chromophore guests with host matrices can afford materials which have photofunctionalities different from those of individual components. Compared with clay and zeolite materials, the use of metal-organic frameworks (MOFs) as a host structure for fabricating luminescent host-guest materials is still at an early stage. Herein, we report the incorporation of a laser dye, 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM), into stilbene-based and naphthalene-based MOF systems. The resulting materials exhibit blue/red two-color emission, and the intensity ratio of blue to red fluorescence varies in different planes within the MOF crystal as detected by 3D confocal fluorescence microscopy. The observed changes in ratiometric fluorescence suggest the occurrence of energy transfer from MOF host to DCM molecules, which can be further confirmed by periodic density functional theoretical (DFT) calculations. Moreover, selective changes in luminescence behavior are observed on treating the guest@MOF samples with volatile organic compounds (methanol, acetone and toluene), indicating that these host-guest systems have potential applications as fluorescence sensors. It can be expected that by rational selection of MOF hosts and guest chromophores with suitable emissive colors and energy levels, a wide variety of multi-color luminescent and energy-transfer systems can readily be prepared in a similar manner.

  15. Structural investigation of the β-cyclodextrin complexes with linalool and isopinocampheol - Influence of monoterpenes cyclicity on the host-guest stoichiometry

    NASA Astrophysics Data System (ADS)

    Ceborska, Magdalena

    2016-05-01

    The crystal structures of the complexes of β-cyclodextrin with two chiral terpene alcohols are presented. (-)-Linalool forms the complex of a 2:2 host-guest stoichiometry, while the complex with (-)-isopinocampheol exhibits a 2:3 stoichiometry. The comparison of the crystal structures with the data for other complexes of β-cyclodextrin with chiral monoterpene alcohols obtained from Cambridge Structural Database (CSD) highlights the tendency of linear and monocyclic alcohols to form complexes of 2:2 stoichiometry whereas bicyclic alcohols prefer to form 2:3 host-guest inclusion complexes.

  16. Spectrofluorimetric study of host-guest complexation of ibuprofen with β-cyclodextrin and its analytical application

    NASA Astrophysics Data System (ADS)

    Manzoori, Jamshid L.; Amjadi, Mohammad

    2003-03-01

    The characteristics of host-guest complexation between β-cyclodextrin (β-CD) and two forms of ibuprofen (protonated and deprotonated) were investigated by fluorescence spectrometry. 1:1 stoichiometries for both complexes were established and their association constants at different temperatures were calculated by applying a non-linear regression method to the change in the fluorescence of ibuprofen that brought about by the presence of β-CD. The thermodynamic parameters (Δ H, Δ S and Δ G) associated with the inclusion process were also determined. Based on the obtained results, a sensitive spectrofluorimetric method for the determination of ibuprofen was developed with a linear range of 0.1-2 μg ml -1 and a detection limit of 0.03 μg ml -1. The method was applied satisfactorily to the determination of ibuprofen in pharmaceutical preparations.

  17. Iridium Cyclometalated Complexes in Host-Guest Chemistry: A Strategy for Maximizing Quantum Yield in Aqueous Media.

    PubMed

    Alrawashdeh, Lubna R; Cronin, Michael P; Woodward, Clifford E; Day, Anthony I; Wallace, Lynne

    2016-07-01

    The weaker emission typically seen for iridium(III) cyclometalated complexes in aqueous medium can be reversed via encapsulation in cucurbit[10]uril (Q[10]). The Q[10] cavity is shown to effectively maximize quantum yields for the complexes, compared to any other medium. This may provide significant advantages for a number of sensor applications. NMR studies show that the complexes are accommodated similarly within the host molecule, even with cationic substituents attached to the ppy ligands, indicating that the hydrophobic effect is the dominant driving force for binding. Cavity-encapsulated 1:1 host-guest species dominate the emission, but 1:2 species are also indicated, which also give some enhancement of intensity. Results demonstrate that the enhancement is due primarily to much lower rates of nonradiative decay but also suggest that the encapsulation can cause a change in character of the emitting state.

  18. Spatial, Hysteretic, and Adaptive Host-Guest Chemistry in a Metal-Organic Framework with Open Watson-Crick Sites.

    PubMed

    Cai, Hong; Li, Mian; Lin, Xiao-Rong; Chen, Wei; Chen, Guang-Hui; Huang, Xiao-Chun; Li, Dan

    2015-09-01

    Biological and artificial molecules and assemblies capable of supramolecular recognition, especially those with nucleobase pairing, usually rely on autonomous or collective binding to function. Advanced site-specific recognition takes advantage of cooperative spatial effects, as in local folding in protein-DNA binding. Herein, we report a new nucleobase-tagged metal-organic framework (MOF), namely ZnBTCA (BTC=benzene-1,3,5-tricarboxyl, A=adenine), in which the exposed Watson-Crick faces of adenine residues are immobilized periodically on the interior crystalline surface. Systematic control experiments demonstrated the cooperation of the open Watson-Crick sites and spatial effects within the nanopores, and thermodynamic and kinetic studies revealed a hysteretic host-guest interaction attributed to mild chemisorption. We further exploited this behavior for adenine-thymine binding within the constrained pores, and a globally adaptive response of the MOF host was observed.

  19. Host-guest inclusion system of artesunate with β-cyclodextrin and its derivatives: Characterization and antitumor activity

    NASA Astrophysics Data System (ADS)

    Xie, Hudie; Yang, Bo; Wang, Fen; Zhao, Yulin

    2015-04-01

    Inclusion complexes between artesunate (ATS) and three cyclodextrins, namely β-cyclodextrin (β-CD), hydroxypropyl-β-cyclodextrin (HP-β-CD) and sulfobutyl ether-β-cyclodextrin (SBE-β-CD), were prepared by a suspension method. The complexes in both liquid and solid were characterized by phase-solubility diagram, nuclear magnetic resonance (NMR), powder X-ray diffraction (XRD) and thermoanalysis. The results suggested that artesunate was partly encapsulated within the cyclodextrin cavity to form a 1:1 stoichiometry host-guest compound. Especially in the SBE-β-CD complex, displayed the greatest stability constant. Significant enhancement of water solubility and thermal stability of ATS in present of β-CDs was shown. The calculated IC50 values indicated that the antitumor activities of inclusion complexes were better than that of ATS. Satisfactory aqueous solubility, along with high thermal stability of inclusion complexes will be potentially useful for their application on the formulation design of natural medicine.

  20. Self-assembly behavior of a linear-star supramolecular amphiphile based on host-guest complexation.

    PubMed

    Wang, Juan; Wang, Xing; Yang, Fei; Shen, Hong; You, Yezi; Wu, Decheng

    2014-11-01

    A star polymer, β-cyclodextrin-poly(l-lactide) (β-CD-PLLA), and a linear polymer, azobenzene-poly(ethylene glycol) (Azo-PEG), could self-assemble into a supramolecular amphiphilic copolymer (β-CD-PLLA@Azo-PEG) based on the host-guest interaction between β-CD and azobenzene moieties. This linear-star supramolecular amphiphilic copolymer further self-assembled into a variety of morphologies, including sphere-like micelle, carambola-like micelle, naan-like micelle, shuttle-like lamellae, tube-like fiber, and random curled-up lamellae, by tuning the length of hydrophilic or hydrophobic chains. The variation of morphology was closely related to the topological structure and block ratio of the supramolecular amphiphiles. These self-assembly structures could disassemble upon an ultraviolet (UV) light irradiation. PMID:25310380

  1. Self-assembly behavior of a linear-star supramolecular amphiphile based on host-guest complexation.

    PubMed

    Wang, Juan; Wang, Xing; Yang, Fei; Shen, Hong; You, Yezi; Wu, Decheng

    2014-11-01

    A star polymer, β-cyclodextrin-poly(l-lactide) (β-CD-PLLA), and a linear polymer, azobenzene-poly(ethylene glycol) (Azo-PEG), could self-assemble into a supramolecular amphiphilic copolymer (β-CD-PLLA@Azo-PEG) based on the host-guest interaction between β-CD and azobenzene moieties. This linear-star supramolecular amphiphilic copolymer further self-assembled into a variety of morphologies, including sphere-like micelle, carambola-like micelle, naan-like micelle, shuttle-like lamellae, tube-like fiber, and random curled-up lamellae, by tuning the length of hydrophilic or hydrophobic chains. The variation of morphology was closely related to the topological structure and block ratio of the supramolecular amphiphiles. These self-assembly structures could disassemble upon an ultraviolet (UV) light irradiation.

  2. Iridium Cyclometalated Complexes in Host-Guest Chemistry: A Strategy for Maximizing Quantum Yield in Aqueous Media.

    PubMed

    Alrawashdeh, Lubna R; Cronin, Michael P; Woodward, Clifford E; Day, Anthony I; Wallace, Lynne

    2016-07-01

    The weaker emission typically seen for iridium(III) cyclometalated complexes in aqueous medium can be reversed via encapsulation in cucurbit[10]uril (Q[10]). The Q[10] cavity is shown to effectively maximize quantum yields for the complexes, compared to any other medium. This may provide significant advantages for a number of sensor applications. NMR studies show that the complexes are accommodated similarly within the host molecule, even with cationic substituents attached to the ppy ligands, indicating that the hydrophobic effect is the dominant driving force for binding. Cavity-encapsulated 1:1 host-guest species dominate the emission, but 1:2 species are also indicated, which also give some enhancement of intensity. Results demonstrate that the enhancement is due primarily to much lower rates of nonradiative decay but also suggest that the encapsulation can cause a change in character of the emitting state. PMID:27315543

  3. Analysis of the phosphorescent dye concentration dependence of triplet-triplet annihilation in organic host-guest systems

    NASA Astrophysics Data System (ADS)

    Zhang, L.; van Eersel, H.; Bobbert, P. A.; Coehoorn, R.

    2016-10-01

    Using a novel method for analyzing transient photoluminescence (PL) experiments, a microscopic description is obtained for the dye concentration dependence of triplet-triplet annihilation (TTA) in phosphorescent host-guest systems. It is demonstrated that the TTA-mechanism, which could be a single-step dominated process or a diffusion-mediated multi-step process, can be deduced for any given dye concentration from a recently proposed PL intensity analysis. A comparison with the results of kinetic Monte Carlo simulations provides the TTA-Förster radius and shows that the TTA enhancement due to triplet diffusion can be well described in a microscopic manner assuming Förster- or Dexter-type energy transfer.

  4. A novel, smart microsphere with K(+)-induced shrinking and aggregating properties based on a responsive host-guest system.

    PubMed

    Jiang, Ming-Yue; Ju, Xiao-Jie; Fang, Lu; Liu, Zhuang; Yu, Hai-Rong; Jiang, Lu; Wang, Wei; Xie, Rui; Chen, Qianming; Chu, Liang-Yin

    2014-01-01

    A novel type of smart microspheres with K(+)-induced shrinking and aggregating properties is designed and developed on the basis of a K(+)-recognition host-guest system. The microspheres are composed of cross-linked poly(N-isopropylacrylamide-co-acryloylamidobenzo-15-crown-5) (P(NIPAM-co-AAB15C5)) networks. Due to the formation of stable 2:1 "sandwich-type" host-guest complexes between 15-crown-5 units and K(+) ions, the P(NIPAM-co-AAB15C5) microspheres significantly exhibit isothermally and synchronously K(+)-induced shrinking and aggregating properties at a low K(+) concentration, while other cations (e.g., Na(+), H(+), NH4(+), Mg(2+), or Ca(2+)) cannot trigger such response behaviors. Effects of chemical compositions of microspheres on the K(+)-induced shrinking and aggregating behaviors are investigated systematically. The K(+)-induced aggregating sensitivity of the P(NIPAM-co-AAB15C5) microspheres can be enhanced by increasing the content of crown ether units in the polymeric networks; however, it is nearly not influenced by varying the monomer and cross-linker concentrations in the microsphere preparation. State diagrams of the dispersed-to-aggregated transformation of P(NIPAM-co-AAB15C5) microspheres in aqueous solutions as a function of temperature and K(+) concentration are constructed, which provide valuable information for tuning the dispersed/aggregated states of microspheres by varying environmental K(+) concentration and temperature. The microspheres with synchronously K(+)-induced shrinking and aggregating properties proposed in this study provide a brand-new model for designing novel targeted drug delivery systems.

  5. Macrocyclic and lantern complexes of palladium(II) with bis(amidopyridine) ligands: synthesis, structure, and host-guest chemistry.

    PubMed

    Yue, Nancy L S; Eisler, Dana J; Jennings, Michael C; Puddephatt, Richard J

    2004-11-29

    The reactions of [PdCl2(NCPh)2] in a 1:1 ratio with the bis(amidopyridine) ligands LL=C6H3(5-R)(1,3-CONH-3-C5H4N)2 with R=H (1a) or R=t-Bu (1b) give the corresponding neutral dipalladium(II) macrocycles trans,trans-[Pd2Cl4(mu-LL)2], 2a and 2b, which crystallize from dimethylformamide with one or two solvent molecules as macrocycle guests. The reaction of [PdCl2(NCPh)2] with LL in a 1:2 ratio gave the cationic lantern complex [Pd2(mu-LL)4]Cl4, 3c (LL=1b), and the reaction in the presence of AgO2CCF3 gave the corresponding trifluoroacetate salts [Pd2(mu-LL)4](CF3CO2)4, 3a (LL=1a) and 3b (LL=1b). These lantern complexes exhibit a remarkable host-guest chemistry, as they can encapsulate cations, anions, and water molecules by interaction of the guest with either the electrophilic NH or the nucleophilic C=O substituents of the amide groups, which can be directed toward the center of the lantern through easy conformational change. The structures of several of these host-guest complexes were determined, and it was found that the cavity size and shape vary according to the ligand conformation, with Pd...Pd separations in the range from 9.45 to 11.95 A. Supramolecular ordering of the lanterns was observed in the solid state, through either hydrogen bonding or secondary bonding to the cationic palladium(II) centers. The selective inclusion by the lantern complexes of alkali metal ions in the sequence Na+ > K+ > Li+ was observed by ESI-MS.

  6. Emergent ion-gated binding of cationic host-guest complexes within cationic M12L24 molecular flasks.

    PubMed

    Bruns, Carson J; Fujita, Daishi; Hoshino, Manabu; Sato, Sota; Stoddart, J Fraser; Fujita, Makoto

    2014-08-27

    "Molecular flasks" are well-defined supramolecular cages that can encapsulate one or more molecular guests within their cavities and, in so doing, change the physical properties and reactivities of the guests. Although molecular flasks are powerful tools for manipulating matter on the nanoscale, most of them are limited in their scope because of size restrictions. Recently, however, increasingly large and diverse supramolecular cages have become available with enough space in their cavities for larger chemical systems such as polymers, nanoparticles, and biomolecules. Here we report how a class of metallosupramolecular cages known as M12L24 polyhedra have been adapted to serve as nanometer-scale containers for solutions of a pseudorotaxane host-guest complex based on a tetracationic cyclophane host, cyclobis(paraquat-p-phenylene) (CBPQT(4+)), and a 1,5-dioxynaphthalene (DNP) guest. Remarkably, the hierarchical integration of pseudorotaxanes and M12L24 superhosts causes the system to express stimulus-responsive behavior, a property which can be described as emergent because neither the DNP⊂CBPQT(4+) nor the M12L24 assemblies exhibit this behavior independently. The DNP-containing M12L24 molecular flasks are effectively "sealed off" to CBPQT(4+) until ions are added as a stimulus to "open" them. The electrolyte stimulus reduces the electrostatic screening distance in solution, allowing favorable DNP⊂CBPQT(4+) host-guest interactions to overcome repulsive Coulombic interactions between the cationic M12L24 cages and CBPQT(4+) rings. This unusual example of ion-gated transport into chemical nanocontainers is reminiscent of transmembrane ion channels which act as gates to the cell, with the important difference that this system is reversible and operates at equilibrium.

  7. Binding enthalpy calculations for a neutral host-guest pair yield widely divergent salt effects across water models.

    PubMed

    Gao, Kaifu; Yin, Jian; Henriksen, Niel M; Fenley, Andrew T; Gilson, Michael K

    2015-10-13

    Dissolved salts are a part of the physiological milieu and can significantly influence the kinetics and thermodynamics of various biomolecular processes, such as binding and catalysis; thus, it is important for molecular simulations to reliably describe their effects. The present study uses a simple, nonionized host-guest model system to study the sensitivity of computed binding enthalpies to the choice of water and salt models. Molecular dynamics simulations of a cucurbit[7]uril host with a neutral guest molecule show striking differences in the salt dependency of the binding enthalpy across four water models, TIP3P, SPC/E, TIP4P-Ew, and OPC, with additional sensitivity to the choice of parameters for sodium and chloride. In particular, although all of the models predict that binding will be less exothermic with increasing NaCl concentration, the strength of this effect varies by 7 kcal/mol across models. The differences appear to result primarily from differences in the number of sodium ions displaced from the host upon binding the guest rather than from differences in the enthalpy associated with this displacement, and it is the electrostatic energy that contributes most to the changes in enthalpy with increasing salt concentration. That a high sensitivity of salt affecting the choice of water model, as observed for the present host-guest system despite it being nonionized, raises issues regarding the selection and adjustment of water models for use with biological macromolecules, especially as these typically possess multiple ionized groups that can interact relatively strongly with ions in solution.

  8. Binding Enthalpy Calculations for a Neutral Host-Guest Pair Yield Widely Divergent Salt Effects across Water Models

    PubMed Central

    Gao, Kaifu; Yin, Jian; Henriksen, Niel M.; Fenley, Andrew T.; Gilson, Michael K.

    2015-01-01

    Dissolved salts are a part of the physiological milieu and can significantly influence the kinetics and thermodynamics of varied biomolecular processes, such as binding and catalysis, so it is important for molecular simulations to reliably describe their effects. The present study uses a simple, non-ionized host-guest model system to study the sensitivity of computed binding enthalpies to the choice of water and salt models. Molecular dynamics simulations of a cucurbit[7]uril host with a neutral guest molecule show striking differences in the salt dependency of the binding enthalpy across four water models, TIP3P, SPC/E, TIP4P-Ew and OPC, with additional sensitivity to the choice of parameters for sodium and chloride. In particular, although all of the models predict that binding will be less exothermic with increasing NaCl concentration, the strength of this effect varies by 7 kcal/mol across models. The differences appear to result primarily from differences in the number of sodium ions displaced from the host on binding the guest, rather than from differences in the enthalpy associated with this displacement; and it is the electrostatic energy that contributes most to the changes in enthalpy with increasing salt concentration. That a high sensitivity of salt effects to the choice of water model is observed for the present host-guest system, despite its being non-ionized, raises issues regarding the selection and adjustment of water models for use with biological macromolecules, especially as these typically possess multiple ionized groups which can interact relatively strongly with ions in solution. PMID:26574247

  9. A self-assembled conformational switch: a host-guest stabilized triple stem molecular beacon via a photoactivated and thermal regeneration mode.

    PubMed

    He, Leiliang; Yang, Xiaohai; Wang, Kemin; Wang, Qing; Zhao, Fang; Huang, Jin; Liu, Jianbo

    2014-07-25

    We present a novel strategy for construction of a conformational switch of a molecular beacon based on the combination of nucleic acid (DNA) self-assembly and reversible host-guest inclusion interaction. With the functionalized probe, the nucleic acid hybridization process can be easily controlled with a photoactivated and thermal regeneration mode.

  10. Synthesis and Small Molecule Exchange Studies of a Magnesium Bisformate Metal-Organic Framework: An Experiment in Host-Guest Chemistry for the Undergraduate Laboratory

    ERIC Educational Resources Information Center

    Rood, Jeffrey A.; Henderson, Kenneth W.

    2013-01-01

    concepts of host-guest chemistry and size exclusion in porous metal-organic frameworks (MOFs). The experiment has been successfully carried out in both introductory and advanced-level inorganic chemistry laboratories. Students synthesized the porous MOF, alpha-Mg[subscript…

  11. Photonic hybrid crystals constructed from in situ host-guest nanoconfinement of a light-emitting complex in metal-organic framework pores

    NASA Astrophysics Data System (ADS)

    Chaudhari, Abhijeet K.; Ryder, Matthew R.; Tan, Jin-Chong

    2016-03-01

    We report the concept underpinning the facile nanoconfinement of a bulky luminous guest molecule in the pores of a metal-organic framework (MOF) host, which yields a hybrid host ⊃ guest nanomaterial with tunable opto-electronic characteristics and enhanced photostability. Utilizing an in situ host-guest confinement strategy enabled by molecular self-assembly, we show that the highly emitting ZnQ [Zn-(bis-8-hydroxyquinoline)] guest complexes could be rapidly encapsulated within the sodalite nanocages of zeolitic imidazolate framework (ZIF-8) host crystals. The nature of optical and electronic transitions phenomena of the guest-encapsulated ZIF-8 ⊃ ZnQ has been elucidated by means of fluorescence and absorption spectroscopy measurements, and substantiated further via theoretical molecular orbital calculations revealing the plausible host-guest charge transfer mechanism involved. Evidence suggests that its photophysical properties are not only strongly determined by the host-guest co-operative bonding interactions within the environment of the confined MOF nanocage, but also can be engineered to manipulate its emission color chromaticity or to shield light-sensitive emitting guests against rapid photochemical degradation.We report the concept underpinning the facile nanoconfinement of a bulky luminous guest molecule in the pores of a metal-organic framework (MOF) host, which yields a hybrid host ⊃ guest nanomaterial with tunable opto-electronic characteristics and enhanced photostability. Utilizing an in situ host-guest confinement strategy enabled by molecular self-assembly, we show that the highly emitting ZnQ [Zn-(bis-8-hydroxyquinoline)] guest complexes could be rapidly encapsulated within the sodalite nanocages of zeolitic imidazolate framework (ZIF-8) host crystals. The nature of optical and electronic transitions phenomena of the guest-encapsulated ZIF-8 ⊃ ZnQ has been elucidated by means of fluorescence and absorption spectroscopy measurements, and

  12. Synchronous spectrofluorimetric study of the supramolecular host-guest interaction of β-cyclodextrin with propranolol: A comparative study

    NASA Astrophysics Data System (ADS)

    Bani-Yaseen, Abdulilah Dawoud

    2015-09-01

    The objective of this work is to assess the use of constant-wavelength synchronous fluorescence spectroscopy (SFS) in comparison to conventional fluorescence spectroscopy (CFS) for the investigation of the supramolecular host-guest interaction of β-CD with propranolol (PPL) in aqueous solutions. Scanning for the optimal Δλ at which the SFS can be performed in the presence of β-CD was examined. The results obtained revealed three distinguishable shapes for PPL using SFS that can be represented by three different Δλ values, namely 10, 40, and 100 nm. However, the effect of the β-CD concentration on the fluorescence intensity of PPL was examined using CFS and SFS of PPL at a Δλ of 10 and 100 nm. The change in the fluorescence intensity was used to calculate the equilibrium constant (Keq) for the formation of the β-CD:PPL inclusion complex by applying the Benesi-Hildebrand method. Keq values of 108, 112, and 117 M-1 were obtained using SFS with a Δλ of 10 and 100 nm, and CFS, respectively. Further, the SFS method was successfully employed to examine the iodide quenching effect on the fluorescence intensity of PPL, where the results obtained revealed a Stern-Volmer quenching constant of 42.8 M-1, which is in good agreement with results obtained using CFS. All results obtained using the SFS method were compared with the results obtained using the CFS method.

  13. Visual determination of aliphatic diamines based on host-guest recognition of calix[4]arene derivatives capped gold nanoparticles.

    PubMed

    Chen, Yangyang; Zhang, Jiangjiang; Gao, Yanmin; Lee, Jaebeom; Chen, Hongxia; Yin, Yongmei

    2015-10-15

    Since amine compounds have been widespread pollutants in nature and they are extensively used in pharmaceutical industries and dye manufacturing, it is highly desirable to develop simple, effective and naked-eye available analytical methods for such aliphatic diamines determination. Calixarenes as macrocycles have drawn intensive interests for fields such as biomedicine, supramolecular chemistry and smart materials. Here, instead of the normal complicated modification strategy, a facile and efficient method for one-pot synthesis of calix[4]arene crown ether (CCE4) capped gold nanoparticles (AuNPs) is proposed. The as-prepared CCE4-AuNPs are not only high water dispersity and stability even after storage for 3 months, but also capable of host-guest recognition of diamines in aqueous systems. Size-selective encapsulation of amine group between CCE4 and diamines carry out the aggregation of CCE4-AuNPs. The determination of diamines such as hexamethylenediamine or spermine can be realized by the UV-vis absorbance change and visual color difference. PMID:26002014

  14. Predicting paramagnetic 1H NMR chemical shifts and state-energy separations in spin-crossover host-guest systems.

    PubMed

    Isley, William C; Zarra, Salvatore; Carlson, Rebecca K; Bilbeisi, Rana A; Ronson, Tanya K; Nitschke, Jonathan R; Gagliardi, Laura; Cramer, Christopher J

    2014-06-14

    The behaviour of metal-organic cages upon guest encapsulation can be difficult to elucidate in solution. Paramagnetic metal centres introduce additional dispersion of signals that is useful for characterisation of host-guest complexes in solution using nuclear magnetic resonance (NMR). However, paramagnetic centres also complicate spectral assignment due to line broadening, signal integration error, and large changes in chemical shifts, which can be difficult to assign even for known compounds. Quantum chemical predictions can provide information that greatly facilitates the assignment of NMR signals and identification of species present. Here we explore how the prediction of paramagnetic NMR spectra may be used to gain insight into the spin crossover (SCO) properties of iron(II)-based metal organic coordination cages, specifically examining how the structure of the local metal coordination environment affects SCO. To represent the tetrahedral metal-organic cage, a model system is generated by considering an isolated metal-ion vertex: fac-ML3(2+) (M = Fe(II), Co(II); L = N-phenyl-2-pyridinaldimine). The sensitivity of the (1)H paramagnetic chemical shifts to local coordination environments is assessed and utilised to shed light on spin crossover behaviour in iron complexes. Our data indicate that expansion of the metal coordination sphere must precede any thermal SCO. An attempt to correlate experimental enthalpies of SCO with static properties of bound guests shows that no simple relationship exists, and that effects are likely due to nuanced dynamic response to encapsulation. PMID:24752730

  15. Host-guest inclusion complex of propafenone hydrochloride with α- and β-cyclodextrins: Spectral and molecular modeling studies

    NASA Astrophysics Data System (ADS)

    Siva, S.; Thulasidhasan, J.; Rajendiran, N.

    2013-11-01

    Host-guest inclusion complexes of cyclodextrins (CDs) with a potential cardiovascular drug propafenone hydrochloride (PFO), were prepared and characterized using absorption, fluorescence, time-resolved fluorescence, SEM, FT-IR, DSC, 1H NMR, XRD and PM3 methods. The spectral studies suggested the phenyl ring along with carbonyl group is present inside of CD cavity. Solvent studies revealed that the normal Stokes shifted band originates from the locally excited state and the large Stokes shifted band occurs due to the emission from ICT. Nanosecond time-resolved studies indicated that PFO exhibits biexponential decay in water and triexponential decay in CD, indicating the formation of 1:1 inclusion complex. The results from solid state studies showed important modifications in the physicochemical properties of free PFO. The ΔH, ΔG and ΔS of the complexation process were determined and it was found that the complexation processes were spontaneous. Investigations of thermodynamic and electronic properties confirmed the stability of the inclusion complex.

  16. pH-Responsive Poly(ethylene glycol)/Poly(L-lactide) Supramolecular Micelles Based on Host-Guest Interaction.

    PubMed

    Zhang, Zhe; Lv, Qiang; Gao, Xiaoye; Chen, Li; Cao, Yue; Yu, Shuangjiang; He, Chaoliang; Chen, Xuesi

    2015-04-29

    pH-responsive supramolecular amphiphilic micelles based on benzimidazole-terminated poly(ethylene glycol) (PEG-BM) and β-cyclodextrin-modified poly(L-lactide) (CD-PLLA) were developed by exploiting the host-guest interaction between benzimidazole (BM) and β-cyclodextrin (β-CD). The dissociation of the supramolecular micelles was triggered in acidic environments. An antineoplastic drug, doxorubicin (DOX), was loaded into the supramolecular micelles as a model drug. The release of DOX from the supramolecular micelles was clearly accelerated as the pH was reduced from 7.4 to 5.5. The DOX-loaded PEG-BM/CD-PLLA supramolecular micelles displayed an enhanced intracellular drug-release rate in HepG2 cells compared to the pH-insensitive DOX-loaded PEG-b-PLLA counterpart. After intravenous injection into nude mice bearing HepG2 xenografts by the tail vein, the DOX-loaded supramolecular micelles exhibited significantly higher tumor inhibition efficacy and reduced systemic toxicity compared to free DOX. Furthermore, the DOX-loaded supramolecular micelles showed a blood clearance rate markedly lower than that of free DOX and comparable to that of the DOX-loaded PEG-b-PLLA micelles after intravenous injection into rats. Therefore, the pH-responsive PEG-BM/CD-PLLA supramolecular micelles hold potential as a smart nanocarrier for anticancer drug delivery. PMID:25856564

  17. Host-guest chemistry for tuning colloidal solubility, self-organization and photoconductivity of inorganic-capped nanocrystals.

    PubMed

    Bodnarchuk, Maryna I; Yakunin, Sergii; Piveteau, Laura; Kovalenko, Maksym V

    2015-12-09

    Colloidal inorganic nanocrystals (NCs), functionalized with inorganic capping ligands, such as metal chalcogenide complexes (MCCs), have recently emerged as versatile optoelectronic materials. As-prepared, highly charged MCC-capped NCs are dispersible only in highly polar solvents, and lack the ability to form long-range ordered NC superlattices. Here we report a simple and general methodology, based on host-guest coordination of MCC-capped NCs with macrocyclic ethers (crown ethers and cryptands), enabling the solubilization of inorganic-capped NCs in solvents of any polarity and improving the ability to form NC superlattices. The corona of organic molecules can also serve as a convenient knob for the fine adjustment of charge transport and photoconductivity in films of NCs. In particular, high-infrared-photon detectivities of up to 3.3 × 10(11) Jones with a fast response (3 dB cut-off at 3 kHz) at the wavelength of 1,200 nm were obtained with films of PbS/K3AsS4/decyl-18-crown-6 NCs.

  18. Host-guest chemistry for tuning colloidal solubility, self-organization and photoconductivity of inorganic-capped nanocrystals

    NASA Astrophysics Data System (ADS)

    Bodnarchuk, Maryna I.; Yakunin, Sergii; Piveteau, Laura; Kovalenko, Maksym V.

    2015-12-01

    Colloidal inorganic nanocrystals (NCs), functionalized with inorganic capping ligands, such as metal chalcogenide complexes (MCCs), have recently emerged as versatile optoelectronic materials. As-prepared, highly charged MCC-capped NCs are dispersible only in highly polar solvents, and lack the ability to form long-range ordered NC superlattices. Here we report a simple and general methodology, based on host-guest coordination of MCC-capped NCs with macrocyclic ethers (crown ethers and cryptands), enabling the solubilization of inorganic-capped NCs in solvents of any polarity and improving the ability to form NC superlattices. The corona of organic molecules can also serve as a convenient knob for the fine adjustment of charge transport and photoconductivity in films of NCs. In particular, high-infrared-photon detectivities of up to 3.3 × 1011 Jones with a fast response (3 dB cut-off at 3 kHz) at the wavelength of 1,200 nm were obtained with films of PbS/K3AsS4/decyl-18-crown-6 NCs.

  19. Efficient complexation between pillar[5]arenes and neutral guests: from host-guest chemistry to functional materials.

    PubMed

    Wang, Yiliang; Ping, Guchuan; Li, Chunju

    2016-08-01

    Since their discovery in 2008, pillar[n]arenes have been a popular family of macrocyclic arene hosts due to their accessible one-step synthesis, convenient functionalization, symmetrical prism structures and perfect cavity host-guest properties. Compared with other macrocyclic hosts, the most peculiar recognition behavior of pillararenes is the strong binding affinities of pillar[5]arenes (P5As) towards neutral guests in organic media, which is unfeasible for classic crown ethers and calixarenes. The intriguing properties have found extensive applications in many fields from supramolecular chemistry to materials science. This feature article provides a detailed summary of the molecular recognition of P5As and neutral guests, where the driving forces, binding mechanisms, and binding selectivities are comprehensively discussed. Furthermore, brief highlights of research progress in the functional applications based on the neutral guest⊂P5A motifs were also discussed, including the construction of complex topological superstructures (e.g. rotaxanes, catenanes and daisy chains), supramolecular polymers, and functional materials. PMID:27351168

  20. A versatile strategy for appending a single functional group to a multifunctional host through host-guest covalent-capture.

    PubMed

    Rebilly, Jean-Noël; Hessani, Assia; Colasson, Benoit; Reinaud, Olivia

    2014-10-21

    Mono-functionalization of a molecular host is a key step for the development of various efficient systems ranging from supramolecular fluorescent probes to supramolecular catalysts. The presence of several identical reactive groups on the host makes its selective mono-functionalization a challenge. We propose a general two-step strategy to achieve this, based on the receptor properties of the host. A guest bearing two orthogonal functions is first reacted with the host presenting itself a reactive function that is complementary to one of those of the guest. As a result, the host is selectively mono-functionalized by the covalent capture of the guest, which inhibits further reaction of the host. The second function that was present on the guest and which is now covalently linked to the host can be activated in the second step for the grafting of various objects. As a proof of concept, the strategy is described on a calix[6]arene scaffold presenting three identical reactive units. Using Huisgen thermal azide-alkyne cycloaddition for the host-guest covalent-capture step, three examples of post-functionalization are described, allowing cavities bearing a single redox tag, fluorescent probe or polydentate ligand through esterification, Schiff base formation or nucleophilic substitution to be obtained.

  1. Enhanced photoelectrochemical water splitting efficiency of a hematite-ordered Sb:SnO2 host-guest system.

    PubMed

    Wang, Lei; Palacios-Padrós, Anna; Kirchgeorg, Robin; Tighineanu, Alexei; Schmuki, Patrik

    2014-02-01

    Host-guest systems such as hematite/SnO2 have attracted a great deal of interest as photoanodes for photoelectrochemical water splitting. In the present work we form an ordered porous tin oxide layer formed by self-organizing anodization of Sn films on a FTO substrate. Subsequently the anodic tin oxide nanostructure is doped with antimony (ATO) by a simple impregnation and annealing treatment, and then decorated with hematite using anodic deposition. Photoelectrochemical water splitting experiments show that compared to conventional SnO2 nanostructures, using a Sb doped nanochannel SnO2 as a host leads to a drastic increase of the water splitting photocurrent response up to 1.5 mA cm(-2) at 1.6 V (vs. RHE) in 1 M KOH under AM 1.5 (100 mW cm(-2) ) conditions compared to 0.04 mA cm(-2) for the non-Sb doped SnO2 scaffold.

  2. Probing into the Supramolecular Driving Force of an Amphiphilic β-Cyclodextrin Dimer in Various Solvents: Host-Guest Recognition or Hydrophilic-Hydrophobic Interaction?

    PubMed

    Bai, Yang; Fan, Xiao-dong; Yao, Hao; Yang, Zhen; Liu, Ting-ting; Zhang, Hai-tao; Zhang, Wan-bin; Tian, Wei

    2015-09-01

    Tuning of the morphology and size of supramolecular self-assemblies is of theoretical and practical significance. To date, supramolecular driving forces in different solvents remain unclear. In this study, we first synthesized an amphiphilic β-cyclodextrin (β-CD) dimer that consists of one hydrophobic ibuprofen (Ibu) and two hydrophilic β-CD moieties (i.e., Ibu-CD2). Ibu-CD2 possesses double supramolecular driving forces, namely, the host-guest recognition and hydrophilic-hydrophobic interaction. The host-guest interaction of Ibu-CD2 induced the formation of branched supramolecular polymers (SPs) in pure water, whereas the hydrophilic-hydrophobic interaction generated spherical or irregular micelles in water/organic mixtures. The SP size increased with the increase in Ibu-CD2 concentration in pure water. By contrast, the size of micelles decreased with the increase in volume ratio of water in mixtures. PMID:26301920

  3. Self-Healing, Expansion-Contraction, and Shape-Memory Properties of a Preorganized Supramolecular Hydrogel through Host-Guest Interactions.

    PubMed

    Miyamae, Kohei; Nakahata, Masaki; Takashima, Yoshinori; Harada, Akira

    2015-07-27

    Supramolecular materials cross-linked between polymer chains by noncovalent bonds have the potential to provide dynamic functions that are not produced by covalently cross-linked polymeric materials. We focused on the formation of supramolecular polymeric materials through host-guest interactions: a powerful method for the creation of nonconventional materials. We employed two different kinds of host-guest inclusion complexes of β-cyclodextrin (βCD) with adamantane (Ad) and ferrocene (Fc) to bind polymers together to form a supramolecular hydrogel (βCD-Ad-Fc gel). The βCD-Ad-Fc gel showed self-healing ability when damaged and responded to redox stimuli by expansion or contraction. Moreover, the βCD-Ad-Fc gel showed a redox-responsive shape-morphing effect. We thus succeeded in deriving three functions from the introduction of two kinds of functional units into a supramolecular material.

  4. A size, shape and concentration controlled self-assembling structure with host-guest recognition at the liquid-solid interface studied by STM

    NASA Astrophysics Data System (ADS)

    Shen, Mengqi; Luo, Zhouyang; Zhang, Siqi; Wang, Shuai; Cao, Lili; Geng, Yanfang; Deng, Ke; Zhao, Dahui; Duan, Wubiao; Zeng, Qingdao

    2016-06-01

    In the present investigation, we reported the fabrication of host networks formed by two newly prepared phenanthrene-butadiynylene macrocycles (PBMs) at the liquid-solid interface. Size, shape and concentration controlled experiments have been performed to investigate the PBMs/coronene (COR) host-guest system with the structural polymorphism phenomenon. Initially, PBM1 could form a regular linear network structure and PBM2 form a well-ordered nanoporous network structure. When the COR molecules were introduced, the self-assembled structure of PBM1 remained unchanged, while COR could be entrapped into the cavities of the PBM2 nanoporous network, and the co-assembly of the PBM2/COR host-guest systems underwent a structural transformation with the increase of concentration of COR. Scanning tunneling microscopy (STM) measurements and density functional theory (DFT) calculations are utilized to reveal the formation mechanism of the molecular nanoarrays controlled by the solution concentration.In the present investigation, we reported the fabrication of host networks formed by two newly prepared phenanthrene-butadiynylene macrocycles (PBMs) at the liquid-solid interface. Size, shape and concentration controlled experiments have been performed to investigate the PBMs/coronene (COR) host-guest system with the structural polymorphism phenomenon. Initially, PBM1 could form a regular linear network structure and PBM2 form a well-ordered nanoporous network structure. When the COR molecules were introduced, the self-assembled structure of PBM1 remained unchanged, while COR could be entrapped into the cavities of the PBM2 nanoporous network, and the co-assembly of the PBM2/COR host-guest systems underwent a structural transformation with the increase of concentration of COR. Scanning tunneling microscopy (STM) measurements and density functional theory (DFT) calculations are utilized to reveal the formation mechanism of the molecular nanoarrays controlled by the solution

  5. Molecular host-guest energy-transfer system with an ultralow amplified spontaneous emission threshold employing an ambipolar semiconducting host matrix.

    PubMed

    Toffanin, Stefano; Capelli, Raffaella; Hwu, Tsyr-Yuan; Wong, Ken-Tsung; Plötzing, Tobias; Först, Michael; Muccini, Michele

    2010-01-14

    We report on the characteristics of a host-guest lasing system obtained by coevaporation of an oligo(9,9-diarylfluorene) derivative named T3 with the red-emitter 4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran dye (DCM). We demonstrate that the ambipolar semiconductor T3 can be implemented as an active matrix in the realization of a host-guest system in which an efficient energy transfer takes place from the T3 matrix to the lasing DCM molecules. We performed a detailed spectroscopic study on the system by systematically varying the DCM concentration in the T3 matrix. Measurements of steady-state photoluminescence (PL), PL quantum yield (PLQY), time-resolved picosecond PL, and amplified spontaneous emission (ASE) threshold are used to optimize the acceptor concentration at which the ASE from DCM molecules takes place with the lowest threshold. The sample with a DCM relative deposition ratio of 2% shows an ASE threshold as low as 0.6 kW/cm(2) and a net optical gain measured by femtosecond time-resolved pump-and-probe spectroscopy as high as 77 cm(-1). The reference model system Alq(3):DCM sample measured in exactly the same experimental conditions presents an one-order-of-magnitude higher ASE threshold. The ASE threshold of T3:DCM is the lowest reported to date for a molecular host-guest energy-transfer system, which makes the investigated blend an appealing system for use as an active layer in lasing devices. In particular, the ambipolar charge transport properties of the T3 matrix and its field-effect characteristics make the host-guest system presented here an ideal candidate for the realization of electrically pumped organic lasers.

  6. Mechanically resilient, injectable, and bioadhesive supramolecular gelatin hydrogels crosslinked by weak host-guest interactions assist cell infiltration and in situ tissue regeneration.

    PubMed

    Feng, Qian; Wei, Kongchang; Lin, Sien; Xu, Zhen; Sun, Yuxin; Shi, Peng; Li, Gang; Bian, Liming

    2016-09-01

    Although considered promising materials for assisting organ regeneration, few hydrogels meet the stringent requirements of clinical translation on the preparation, application, mechanical property, bioadhesion, and biocompatibility of the hydrogels. Herein, we describe a facile supramolecular approach for preparing gelatin hydrogels with a wide array of desirable properties. Briefly, we first prepare a supramolecular gelatin macromer via the efficient host-guest complexation between the aromatic residues of gelatin and free diffusing photo-crosslinkable acrylated β-cyclodextrin (β-CD) monomers. The subsequent crosslinking of the macromers produces highly resilient supramolecular gelatin hydrogels that are solely crosslinked by the weak host-guest interactions between the gelatinous aromatic residues and β-cyclodextrin (β-CD). The obtained hydrogels are capable of sustaining excessive compressive and tensile strain, and they are capable of quick self healing after mechanical disruption. These hydrogels can be injected in the gelation state through surgical needles and re-molded to the targeted geometries while protecting the encapsulated cells. Moreover, the weak host-guest crosslinking likely facilitate the infiltration and migration of cells into the hydrogels. The excess β-CDs in the hydrogels enable the hydrogel-tissue adhesion and enhance the loading and sustained delivery of hydrophobic drugs. The cell and animal studies show that such hydrogels support cell recruitment, differentiation, and bone regeneration, making them promising carrier biomaterials of therapeutic cells and drugs via minimally invasive procedures. PMID:27294539

  7. Polymers with customizable optical and rheological properties based on an epoxy acrylate based host-guest system

    NASA Astrophysics Data System (ADS)

    Gleiβner, U.; Hobmaier, J.; Hanemann, T.

    2015-09-01

    We report an easy way to tune the optical refractive index and viscosity of an epoxy acrylate-based host-guest system which can be used for the fabrication of optical waveguides. This allows fast and precise modification of the material system for different replication methods like hot embossing, inkjet printing or spin coating. To modify the refractive index n, an electron-rich organic dopant such as phenanthrene is added to a commercially available reactive polymer based resin. Moreover, changes in viscosity can be achieved by using a comonomer with suitable properties like benzyl methacrylate (BMA). We used a commercially available UV-curable epoxy acrylate based polymer matrix to investigate both the influence of phenanthrene and of benzyl methacrylate. First, mixtures of the pure polymer and benzyl methacrylate with a ratio of 30, 50, and 80 wt% benzyl methacrylate were produced. Second, phenanthrene was added with 5 and 10 wt%, respectively. All components were mixed and then polymerized by UV-irradiation and with a thermal postcure. The viscosity of the mixtures decreased at 20°C linearly from 1.5 Pa·s (30 wt%) to 8 mPa·s (80 wt%), whereas the refractive index decreased at the same time by a small amount from 1.570 to 1.568 (@589 nm, 20 °C). By adding phenanthrene refractive index increased to a maximum of n = 1.586 (50 wt% BMA, 10 wt% phenanthrene). Abbe numbers for the compositions without phenanthrene ranged from 35 to 38.

  8. Tridentate Lewis Acids Based on 1,3,5-Trisilacyclohexane Backbones and an Example of Their Host-Guest Chemistry.

    PubMed

    Weisheim, Eugen; Reuter, Christian G; Heinrichs, Peter; Vishnevskiy, Yury V; Mix, Andreas; Neumann, Beate; Stammler, Hans-Georg; Mitzel, Norbert W

    2015-08-24

    Directed tridentate Lewis acids based on the 1,3,5-trisilacyclohexane skeleton with three ethynyl groups [CH2Si(Me)(C2H)]3 were synthesised and functionalised by hydroboration with HB(C6F5)2, yielding the ethenylborane {CH2Si(Me)[C2H2B(C6F5)2]}3, and by metalation with gallium and indium organyls affording {CH2Si(Me)[C2M(R)2]}3 (M = Ga, In, R = Me, Et). In the synthesis of the backbone the influence of substituents (MeO, EtO and iPrO groups at Si) on the orientation of the methyl group was studied with the aim to increase the abundance of the all-cis isomer. New compounds were identified by elemental analyses, multi-nuclear NMR spectroscopy and in some cases by IR spectroscopy. Crystal structures were obtained for cis-trans-[CH2Si(Me)(Cl)]3, all-cis-[CH2Si(Me)(H)]3, all-cis-[CH2Si(Me)(C2H)]3, cis-trans-[CH2Si(Me)(C2H)]3 and all-cis-[CH2Si(Me)(C2SiMe3)]3. A gas-phase electron diffraction experiment for all-cis-[CH2Si(Me)(C2H)]3 provides information on the relative stabilities of the all-equatorial and all-axial form; the first is preferred in both solid and gas phase. The gallium-based Lewis acid {CH2Si(Me)[C2Ga(Et)2]}3 was reacted with a tridentate Lewis base (1,3,5-trimethyl-1,3,5-triazacyclohexane) in an NMR titration experiment. The generated host-guest complexes involved in the equilibria during this reaction were identified by DOSY NMR spectroscopy by comparing measured diffusion coefficients with those of the suitable reference compounds of same size and shape.

  9. Tridentate Lewis Acids Based on 1,3,5-Trisilacyclohexane Backbones and an Example of Their Host-Guest Chemistry.

    PubMed

    Weisheim, Eugen; Reuter, Christian G; Heinrichs, Peter; Vishnevskiy, Yury V; Mix, Andreas; Neumann, Beate; Stammler, Hans-Georg; Mitzel, Norbert W

    2015-08-24

    Directed tridentate Lewis acids based on the 1,3,5-trisilacyclohexane skeleton with three ethynyl groups [CH2Si(Me)(C2H)]3 were synthesised and functionalised by hydroboration with HB(C6F5)2, yielding the ethenylborane {CH2Si(Me)[C2H2B(C6F5)2]}3, and by metalation with gallium and indium organyls affording {CH2Si(Me)[C2M(R)2]}3 (M = Ga, In, R = Me, Et). In the synthesis of the backbone the influence of substituents (MeO, EtO and iPrO groups at Si) on the orientation of the methyl group was studied with the aim to increase the abundance of the all-cis isomer. New compounds were identified by elemental analyses, multi-nuclear NMR spectroscopy and in some cases by IR spectroscopy. Crystal structures were obtained for cis-trans-[CH2Si(Me)(Cl)]3, all-cis-[CH2Si(Me)(H)]3, all-cis-[CH2Si(Me)(C2H)]3, cis-trans-[CH2Si(Me)(C2H)]3 and all-cis-[CH2Si(Me)(C2SiMe3)]3. A gas-phase electron diffraction experiment for all-cis-[CH2Si(Me)(C2H)]3 provides information on the relative stabilities of the all-equatorial and all-axial form; the first is preferred in both solid and gas phase. The gallium-based Lewis acid {CH2Si(Me)[C2Ga(Et)2]}3 was reacted with a tridentate Lewis base (1,3,5-trimethyl-1,3,5-triazacyclohexane) in an NMR titration experiment. The generated host-guest complexes involved in the equilibria during this reaction were identified by DOSY NMR spectroscopy by comparing measured diffusion coefficients with those of the suitable reference compounds of same size and shape. PMID:26213228

  10. A surprising host-guest relationship between 1,2-dichloroethane and the cesium complex of tetrabenzo-24-crown-8

    SciTech Connect

    Levitskaia, T.G.; Bryan, J.C.; Sachleben, R.A.; Lamb, J.D.; Moyer, B.A.

    2000-02-02

    The structure of the complex [Cs(tetrabenzo-24-crown-8)(1,2-dichloroethane){sub 2}](NO{sub 3}){sm{underscore}bullet}H{sub 2}O was shown by X-ray crystallography to involve an unprecedented bidentate coordination of two 1,2-dichloroethane solvent molecules to the Cs{sup +} cation via the four chlorine atoms. The coordination of the solvent molecules occurs within two clefts between facing benzo groups, one pair of benzo groups related to the other pair by an improper noncrystallographic 90{degree} rotation. Resembling the seam on a tennis ball, the crown ether envelops the metal cation within a cagelike arrangement of eight crown ether oxygen atoms. Good geometric and electronic complimentarily characterizes the apparent host-guest relationship between the cleft environment and the solvent molecules. The complete encapsulation of the cation by the crown ether and two solvent molecules explains well the speciation behavior observed in liquid-liquid extraction of CsNO{sub 3} or CsClO{sub 4} from aqueous solution to 1,2-dichloroethane solutions of the alkylated analogues 4,4{double{underscore}prime}- or 4,5{double{underscore}prime}-bis(tert-octylbenzo)dibenzo-24-crown-8. In the extraction process studied at 25 C, simple 1:1 metal/crown complexes form in the solvent phase, as modeled by the program SXLSQI. The complex cation and counteranion are present both as ion-pairs, postulated to be ligand-separated ion-pairs as suggested by the crystal structure, and as dissociated ions. In agreement with a theoretical treatment of ion-pairing, the ion-pairs possess unusually low stability and exhibit no discrimination between the anions, largely ascribed to the large effective radius of the complex metal cation. Values of log K{sub f} corresponding to the formation of the complex cations Cs[bis(tert-octylbenzo)-dibenzo-24-crown-8]{sup +} in 1,2-dichloroethane at 25 C average 10.5 {+-} 0.2 for both positional isomers of the crown ether and for their 3:2 mixture. Overall, these

  11. Supramolecular side-chain poly[2]pseudorotaxanes formed by orthogonal coordination-driven self-assembly and crown-ether-based host-guest interactions.

    PubMed

    Xing, Hao; Wei, Peifa; Yan, Xuzhou

    2014-06-01

    The themes of coordination-driven self-assembly, host-guest interactions, and supramolecular polymerization are unified in an orthogonal noninterfering fashion to deliver side-chain poly[2]pseudorotaxanes. Specifically, a bis(p-phenylene)-34-crown-10 derivative 1 bearing two pyridyl groups polymerizes into a side-chain poly[2]pseudorotaxane upon the addition of di-Pt(II) acceptor 4 in the presence of paraquat. Interestingly, by adding a competitive guest 3, the poly[2]pseudorotaxane can realize a conversion in one pot.

  12. Supramolecular side-chain poly[2]pseudorotaxanes formed by orthogonal coordination-driven self-assembly and crown-ether-based host-guest interactions.

    PubMed

    Xing, Hao; Wei, Peifa; Yan, Xuzhou

    2014-06-01

    The themes of coordination-driven self-assembly, host-guest interactions, and supramolecular polymerization are unified in an orthogonal noninterfering fashion to deliver side-chain poly[2]pseudorotaxanes. Specifically, a bis(p-phenylene)-34-crown-10 derivative 1 bearing two pyridyl groups polymerizes into a side-chain poly[2]pseudorotaxane upon the addition of di-Pt(II) acceptor 4 in the presence of paraquat. Interestingly, by adding a competitive guest 3, the poly[2]pseudorotaxane can realize a conversion in one pot. PMID:24819441

  13. Supramolecular host-guest interaction of trityl-nitroxide biradicals with cyclodextrins: modulation of spin-spin interaction and redox sensitivity

    PubMed Central

    Tan, Xiaoli; Song, Yuguang; Liu, Huiqiang; Zhong, Qinwen; Rockenbauer, Antal; Villamena, Frederick A.; Zweier, Jay L.; Liu, Yangping

    2016-01-01

    Supramolecular host-guest interactions of trityl-nitroxide (TN) biradicals CT02-VT, CT02-AT and CT02-GT with methyl-β-cyclodextrin (M-β-CD), hydroxypropyl-β-cyclodextrin (H-β-CD) and γ-cyclodextrin (γ-CD) were investigated by EPR spectroscopy. In the presence of cyclodextrins (i.e., γ-CD, M-β-CD and H-β-CD), host-guest complexes of CT02-VT are formed where the nitroxide and linker parts possibly interact with the cyclodextrins’ cavities. Complexation with cyclodextrins leads to suppression of the intramolecular through-space spin-spin exchange coupling in CT02-VT, thus allowing determination of the through-bond spin-spin exchange coupling which was calculated to be 1.6 G using EPR simulations. Different types of cyclodextrins have variable binding affinity with CT02-VT with γ-CD (95 M−1) > M-β-CD (70 M−1) > H-β-CD (32 M−1). In addition, the effect of the linkers in TN biradicals on the host-guest interactions was also investigated. Among three TN biradicals studied, CT02-VT has the highest association constant with one designated cyclodextrin derivative. On the other hand, the complexes of CT02-GT (~ 22 G) and CT02-AT (7.7–9.0 G) with cyclodextrins have much higher through-bond spin-spin exchange couplings than that of CT02-VT (1.6 G) due to the shorter linkers than that of CT02-VT. Furthermore, the stability of TN biradicals towards ascorbate was significantly enhanced after the complexation with CDs, with an almost 2-time attenuation of the second-order rate constants for all the biradicals. Therefore, the supramolecular host-guest interactions with cyclodextrins will be an alternative method to modulate the magnitude of the spin-spin interactions and redox sensitivity of TN biradicals and the resulting complexes are promising as highly efficient DNP polarizing agents as well as EPR redox probes. PMID:26700002

  14. Influence of Equilibration Time in Solution on the Inclusion/Exclusion Topology Ratio of Host-Guest Complexes Probed by Ion Mobility and Collision-Induced Dissociation.

    PubMed

    Carroy, Glenn; Daxhelet, Charlotte; Lemaur, Vincent; De Winter, Julien; De Pauw, Edwin; Cornil, Jérôme; Gerbaux, Pascal

    2016-03-18

    Host-guest complexes are formed by the creation of multiple noncovalent bonds between a large molecule (the host) and smaller molecule(s) or ion(s) (the guest(s)). Ion-mobility separation coupled with mass spectrometry nowadays represents an ideal tool to assess whether the host-guest complexes, when transferred to the gas phase upon electrospray ionization, possess an exclusion or inclusion nature. Nevertheless, the influence of the solution conditions on the nature of the observed gas-phase ions is often not considered. In the specific case of inclusion complexes, kinetic considerations must be taken into account beside thermodynamics; the guest ingression within the host cavity can be characterized by slow kinetics, which makes the complexation reaction kinetically driven on the timescale of the experiment. This is particularly the case for the cucurbituril family of macrocyclic host molecules. Herein, we selected para-phenylenediamine and cucurbit[6]uril as a model system to demonstrate, by means of ion mobility and collision-induced dissociation measurements, that the inclusion/exclusion topology ratio varies as a function of the equilibration time in solution prior to the electrospray process.

  15. Host-Guest Chemistry between Perylene Diimide (PDI) Derivatives and 18-Crown-6: Enhancement in Luminescence Quantum Yield and Electrical Conductivity.

    PubMed

    Lasitha, P; Prasad, Edamana

    2016-07-18

    Perylene diimide (PDI) derivatives exhibit a high propensity for aggregation, which causes the aggregation-induced quenching of emission from the system. Host-guest chemistry is one of the best-known methods for preventing aggregation through the encapsulation of guest molecules. Herein we report the use of 18-crown-6 (18-C-6) as a host system to disaggregate suitably substituted PDI derivatives in methanol. 18-C-6 formed complexes with amino-substituted PDIs in methanol, which led to disaggregation and enhanced emission from the systems. Furthermore, the embedding of the PDI⋅18-C-6 complexes in poly(vinyl alcohol) (PVA) films generated remarkably high emission quantum yields (60-70 %) from the PDI derivatives. More importantly, the host-guest systems were tested for their ability to conduct electricity in PVA films. The electrical conductivities of the self-assembled systems in PVA were measured by electrochemical impedance spectroscopy (EIS) and the highest conductivity observed was 2.42×10(-5)  S cm(-1) .

  16. Applying Mechanochemistry for Bottom-Up Synthesis and Host-Guest Surface Modification of Semiconducting Nanocrystals: A Case of Water-Soluble β-Cyclodextrin-Coated Zinc Oxide.

    PubMed

    Krupiński, Piotr; Kornowicz, Arkadiusz; Sokołowski, Kamil; Cieślak, Anna M; Lewiński, Janusz

    2016-06-01

    Mechanochemistry has recently emerged as an environmentally friendly solventless synthesis method enabling a variety of transformations including those impracticable in solution. However, its application in the synthesis of well-defined nanomaterials remains very limited. Here, we report a new bottom-up mechanochemical strategy to rapid mild-conditions synthesis of organic ligand-coated ZnO nanocrystals (NCs) and their further host-guest modification with β-cyclodextrin (β-CD) leading to water-soluble amide-β-CD-coated ZnO NCs. The transformations can be achieved by either one-pot sequential or one-step three-component process. The developed bottom-up methodology is based on employing oxo-zinc benzamidate, [Zn4 (μ4 -O)(NHOCPh)6 ], as a predesigned molecular precursor undergoing mild solid-state transformation to ZnO NCs in the presence of water in a rapid, clean and sustainable process. PMID:27114269

  17. NMR, surface tension and conductance study to investigate host-guest inclusion complexes of three sequential ionic liquids with β-cyclodextrin in aqueous media

    NASA Astrophysics Data System (ADS)

    Barman, Siti; Ekka, Deepak; Saha, Subhadeep; Roy, Mahendra Nath

    2016-08-01

    Host-guest inclusion complexes of three sequential cationic room temperature surface active ionic liquids, benzyltrialkylammonium chloride [(C6H5CH2)N(CnH2n+1)3Cl; where n = 1, 2, 4] with β-cyclodextrin in aqueous media have been studied using surface tension, conductance and NMR spectroscopy. All the studies have suggested that the hydrophobic benzyl group of ionic liquids is encapsulated inside into the cavity of β-cyclodextrin and played a crucial role in supporting the formation of inclusion complexes. The variation of the thermodynamic parameters with guest size, shape is used to draw inferences about contributions to the overall binding by means of the driving forces, viz., hydrophobic effect, steric hindrance, van der Waal force, and electrostatic force.

  18. Fluorescent and colorimetric magnetic microspheres as nanosensors for Hg2+ in aqueous solution prepared by a sol-gel grafting reaction and host-guest interaction

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Zhang, Yue; Yang, Qingbiao; Sun, Mingda; Fei, Xiaoliang; Song, Yan; Zhang, Yingmu; Li, Yaoxian

    2013-05-01

    Fluorescent sensing TSRh6G-β-cyclodextrin fluorophore/adamantane-modified inclusion complex magnetic nanoparticles (TFIC MNPs) have been synthesized via the cooperation of a host-guest interaction and sol-gel grafting reaction. Powder X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, and UV-visible absorption and emission spectroscopy have been employed to characterize the material. Fluorescence and UV-visible spectra have shown that the resultant multifunctional nanoparticle sensors exhibit selective `turn-on' type fluorescent enhancements and a clear color change from light brown to pink with Hg2+. Owing to a larger surface area and high permeability, TFIC MNPs exhibit remarkable selectivity and sensitivity for Hg2+, and its detection limit measures up to the micromolar level in aqueous solution. Most importantly, magnetic measurements have shown that TFIC magnetic nanoparticles are superparamagnetic and they can be separated and collected easily using a commercial magnet. These results not only solve the limitations in practical sensing applications of nanosensors, but also enable the fabrication of other multifunctional nanostructure-based hybrid nanomaterials.Fluorescent sensing TSRh6G-β-cyclodextrin fluorophore/adamantane-modified inclusion complex magnetic nanoparticles (TFIC MNPs) have been synthesized via the cooperation of a host-guest interaction and sol-gel grafting reaction. Powder X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, and UV-visible absorption and emission spectroscopy have been employed to characterize the material. Fluorescence and UV-visible spectra have shown that the resultant multifunctional nanoparticle sensors exhibit selective `turn-on' type fluorescent enhancements and a clear color change from light brown to pink with Hg2+. Owing to a larger surface area and high permeability, TFIC MNPs exhibit remarkable selectivity and sensitivity for Hg2

  19. Host-Guest Interaction-Based Self-Engineering of Nano-Sized Vesicles for Co-Delivery of Genes and Anticancer Drugs.

    PubMed

    Yang, Bin; Dong, Xing; Lei, Qi; Zhuo, Renxi; Feng, Jun; Zhang, Xianzheng

    2015-10-01

    On the basis of host-guest interactions, this study reported a kind of linear-hyperbranched supramolecular amphiphile and its assembled vesicles for the combined achievement of drug encapsulation and DNA delivery. Amine-attached β-cyclodextrin-centered hyperbranched polyglycerol and linear adamantane-terminated octadecane were arranged to spontaneously interlink together and then self-assemble into nanoscale vesicles. As the model of a hydrophilic agent, DOX·HCl was demonstrated to be readily loaded into the hollow cavity of the vesicles. The drug release pattern could be controlled by adjusting the environmental acidity, favoring the intracellularly fast drug liberation in response to the cellular lysosomal microenvironment. The nanovesicles displayed superior serum-tolerant transgene ability and significantly lower cytotoxicity compared to those of PEI25K, the gold standard of gene delivery vectors. The drug-loaded nanovesicle can co-deliver DNA payloads into cells and allow the preferable accumulation of two payloads in nuclei. The drug encapsulation was found to have little influence on the transfection. This co-delivery vehicle presents a good example of rational design of cationic supramolecular vesicles for stimulus-responsive drug/DNA transport. PMID:26398113

  20. Azo-capped polysarcosine-b-polylysine as polypeptide gene vector: A new strategy to improve stability and easy optimization via host-guest interaction.

    PubMed

    Du, Jianwei; Tian, Ce; Liu, Yajie; Ling, Jun; Wang, Youxiang

    2015-06-01

    Polypeptide has been extensively researched in gene/drug delivery system due to the good biocompatibility. Herein, we synthesized total-polypeptide copolymers, i.e. Azo(azobenzene)-capped polysarcosine-b-polylysine (ASL) with narrow molecular weight distribution by α-amino acid N-carboxyanhydride (NCA) polymerization. Although the molecular weight of PLL segment was only about 6 kDa, ASL could condense DNA effectively and form about 150 nm spherical nanoparticles at N/P ratio of 15. The surface charge was significantly reduced due to the shielding effect of polysarcosine (PSAR) shell. ASL/DNA PeptoPlexes showed good colloidal stability under physiological salt condition and complexation competition stability in the presence of counter polyanion, which might improve the circulation time in vivo. The tip design of azobenzene provided a facile way for ligand modification via host-guest interaction, which could be flexibly optimized by changing its functional tags responding to a request. Our data showed that the introduction of CD-R8 could promote the internalization of gene into cytoplasm and even nucleus owing to the membrane penetrating effect of R8. Cell culture experiments indicated as a total-polypeptide system, ASL showed good cellular viability and comparable gene transfection level as PLL with molecular weight of 50 kDa. Overall, PSAR served as an ideal alternative of PEG and this total-polypeptide system showed us a good direction for gene carrier design.

  1. Competing Noncovalent Host-guest Interactions and H/D Exchange: Reactions of Benzyloxycarbonyl-Proline Glycine Dipeptide Variants with ND3

    NASA Astrophysics Data System (ADS)

    Miladi, Mahsan; Olaitan, Abayomi D.; Zekavat, Behrooz; Solouki, Touradj

    2015-11-01

    A combination of density functional theory calculations, hydrogen/deuterium exchange (HDX) reactions, ion mobility-mass spectrometry, and isotope labeling tandem mass spectrometry was used to study gas-phase "host-guest" type interactions of a benzyloxycarbonyl (Z)-capped proline (P) glycine (G) model dipeptide (i.e., Z-PG) and its various structural analogues with ND3. It is shown that in a solvent-free environment, structural differences between protonated and alkali metal ion (Na+, K+, or Cs+)-complexed species of Z-PG affect ND3 adduct formation. Specifically, [Z-PG + H]+ and [Z-PG-OCH3 + H]+ formed gas-phase ND3 adducts ([Z-PG (or Z-PG-OCH3) + H + ND3]+) but no ND3 adducts were observed for [Z-PG + alkali metal]+ or [Z-PG + H - CO2]+. Experimentally measured and theoretically calculated collision cross sections (CCSs) of protonated and alkali metal ion-complexed Z-PG species showed similar trends that agreed with the observed structural differences from molecular modeling results. Moreover, results from theoretical ND3 affinity calculations were consistent with experimental HDX observations, indicating a more stable ND3 adduct for [Z-PG + H]+ compared to [Z-PG + alkali metal]+ species. Molecular modeling and experimental MS results for [Z-PG + H]+ and [Z-PG + alkali metal]+ suggest that optimized cation-π and hydrogen bonding interactions of carbonyl groups in final products are important for ND3 adduct formation.

  2. A 1H NMR Study of Host/Guest Supramolecular Complexes of a Curcumin Analogue with β-Cyclodextrin and a β-Cyclodextrin-Conjugated Gemini Surfactant.

    PubMed

    Poorghorban, Masoomeh; Karoyo, Abdalla H; Grochulski, Pawel; Verrall, Ronald E; Wilson, Lee D; Badea, Ildiko

    2015-08-01

    Host systems based on β-cyclodextrin (βCD) were employed as pharmaceutical carriers to encapsulate a poorly soluble drug, curcumin analogue (NC 2067), in order to increase its water solubility. βCD was chemically conjugated with an amphiphilic gemini surfactant with the ability to self-assemble and to form nanoscale supramolecular structures. The conjugated molecule, βCDgemini surfactant (βCDg), was shown to be a promising drug delivery agent. In this report, its physicochemical properties were assessed in aqueous solution using 1D and 2D 1H NMR spectroscopy. The results showed that the apolar hydrocarbon domain of the gemini surfactant was self-included within the βCD internal cavity. The host/guest complexes composed of native βCD or βCDg with NC 2067 were examined using 1D/2D ROESY NMR methods. The stoichiometry of βCD/NC 2067 complex was estimated using Job's method via 1H NMR spectroscopy. The binding geometry of NC 2067 within βCD was proposed using molecular docking and further supported by 1D and 2D ROESY NMR results. Addition of NC 2067 to βCDg revealed minimal changes to the overall structure of the βCDg system, in agreement with the formation of a βCDg/NC 2067 ternary complex. PMID:26083126

  3. Fluorescent Cross-Linked Supramolecular Polymer Constructed by Orthogonal Self-Assembly of Metal-Ligand Coordination and Host-Guest Interaction.

    PubMed

    Qian, Xiaomin; Gong, Weitao; Li, Xiaopeng; Fang, Le; Kuang, Xiaojun; Ning, Guiling

    2016-05-10

    A new host molecule consists of four terpyridine groups as the binding sites with zinc(II) ion and a copillar[5]arene incorporated in the center as a spacer to interact with guest molecule was designed and synthesized. Due to the 120 ° angle of the rigid aromatic segment, a cross-linked dimeric hexagonal supramolecular polymer was therefore generated as the result of the orthogonal self-assembly of metal-ligand coordination and host-guest interaction. UV/Vis spectroscopy, (1) H NMR spectroscopy, viscosity and dynamic light-scattering techniques were employed to characterize and understand the cross-linking process with the introduction of zinc(II) ion and guest molecule. More importantly, well-defined morphology of the self-assembled supramolecular structure can be tuned by altering the adding sequence of the two components, that is, the zinc(II) ion and the guest molecule. In addition, introduction of a competitive ligand suggested the dynamic nature of the supramolecular structure. PMID:27062539

  4. Can we beat the biotin-avidin pair?: cucurbit[7]uril-based ultrahigh affinity host-guest complexes and their applications.

    PubMed

    Shetty, Dinesh; Khedkar, Jayshree K; Park, Kyeng Min; Kim, Kimoon

    2015-12-01

    The design of synthetic, monovalent host-guest molecular recognition pairs is still challenging and of particular interest to inquire into the limits of the affinity that can be achieved with designed systems. In this regard, cucurbit[7]uril (CB[7]), an important member of the host family cucurbit[n]uril (CB[n], n = 5-8, 10, 14), has attracted much attention because of its ability to form ultra-stable complexes with multiple guests. The strong hydrophobic effect between the host cavity and guests, ion-dipole and dipole-dipole interactions of guests with CB portals helps in cooperative and multiple noncovalent interactions that are essential for realizing such strong complexations. These highly selective, strong yet dynamic interactions can be exploited in many applications including affinity chromatography, biomolecule immobilization, protein isolation, biological catalysis, and sensor technologies. In this review, we summarize the progress in the development of high affinity guests for CB[7], factors affecting the stability of complexes, theoretical insights, and the utility of these high affinity pairs in different challenging applications. PMID:26434388

  5. Are electron tweezers possible?

    PubMed

    Oleshko, Vladimir P; Howe, James M

    2011-11-01

    Positively answering the question in the title, we demonstrate in this work single electron beam trapping and steering of 20-300nm solid Al nanoparticles generated inside opaque submicron-sized molten Al-Si eutectic alloy spheres. Imaging of solid nanoparticles and liquid alloy in real time was performed using energy filtering in an analytical transmission electron microscope (TEM). Energy-filtering TEM combined with valence electron energy-loss spectroscopy enabled us to investigate in situ nanoscale transformations of the internal structure, temperature dependence of plasmon losses, and local electronic and optical properties under melting and crystallization of individual binary alloy particles. For particles below 20nm in size, enhanced vibrations of the dynamic solid-liquid interface due to instabilities near the critical threshold were observed just before melting. The obtained results indicate that focused electron beams can act as a tool for manipulation of metal nanoparticles by transferring linear and angular mechanical momenta. Such thermally assisted electron tweezers can be utilized for touchless manipulation and processing of individual nano-objects and potentially for fabrication of assembled nanodevices with atomic level sensitivity and lateral resolution provided by modern electron optical systems. This is by three orders of magnitude better than for light microscopy utilized in conventional optical tweezers. New research directions and potential applications of trapping and tracking of nano-objects by focused electron beams are outlined.

  6. Formation of 1:2 host-guest complexes based on triptycene-derived macrotricycle and paraquat derivatives: anion-π interactions between PF6(-) and bipyridinium rings in the solid state.

    PubMed

    Guo, Jia-Bin; Han, Ying; Cao, Jing; Chen, Chuan-Feng

    2011-10-21

    A triptycene-derived macrotricyclic host containing two dibenzo-[30]-crown-10 moieties forms stable 1:2 host-guest complexes with paraquat derivatives in both solution and the solid state, in which anion-π interactions between PF(6)(-) and the bipyridinium rings play an important role. Moreover, it was found that binding and release of the guest molecules in the complexes could be easily controlled by the addition and removal of potassium ions. PMID:21962056

  7. A joint structural, kinetic, and thermodynamic investigation of substituent effects on host-guest complexation of bicyclic azoalkanes by beta-cyclodextrin.

    PubMed

    Zhang, Xiangyang; Gramlich, Gabriela; Wang, Xiaojuan; Nau, Werner M

    2002-01-16

    Derivatives of the azoalkane 2,3-diazabicyclo[2,2,2]oct-2-ene (1a) with bridgehead 1,4-dialkyl (1b), 1,4-dichloro (1c), 1-hydroxymethyl (1d), 1-aminomethyl (1e), and 1-ammoniummethyl (1f) substituents form host-guest inclusion complexes with beta-cyclodextrin. They were employed as probes to assess substituent effects on the kinetics and thermodynamics of this complexation by using time-resolved and steady-state fluorimetry, UV spectrophotometry, induced circular dichroism (ICD) measurements, and (1)H NMR spectroscopy. The kinetic analysis based on quenching of the long-lived fluorescence of the azoalkanes by addition of host provided excited-state association rate constants between 2.6 x 10(8) and 7.0 x 10(8) M(-)(1) s(-)(1). The binding constants for 1a (1100 M(-1)), 1b (900 M(-1)), 1c (1900 M(-1)), 1d (180 M(-1)), 1e (250 M(-1)), and 1f (ca. 20 M(-1)) were obtained by UV, NMR, and ICD titrations. A positive ICD signal of the azo absorption around 370 nm was observed for the beta-cyclodextrin complexes of 1a, 1d, and 1f with the intensity order 1a > 1d approximately 1f, and a negative signal was measured for those of 1b, 1c, and 1e with the intensity order 1c < 1b approximately 1e. The ICD was employed for the assignment of the solution structures of the complexes, in particular the relative orientation of the guest in the host (co-conformation).

  8. Amplified fluorescence detection of DNA based on catalyzed dynamic assembly and host-guest interaction between β-cyclodextrin polymer and pyrene.

    PubMed

    Huang, Haihua; Yang, Xiaohai; Wang, Kemin; Wang, Qing; Guo, Qiuping; Huang, Jin; Liu, Jianbo; Guo, Xiaochen; Li, Wenshan; He, Leiliang

    2015-11-01

    The detection of nucleic acids is fundamental for studying their functions and for the development of biological studies and medical diagnostics. Herein, we report a new strategy for nucleic acid amplified detection by combining target-catalyzed dynamic assembly with host-guest interaction between β-cyclodextrin polymer (β-CDP) and pyrene. In this strategy, a metastable pyrene-labeled hairpin DNA probe (probe H1) and a metastable unlabeled hairpin DNA probe (probe H2) were elaborately designed as the assembly components, which were kinetically handicapped from cross-opening in the absence of target DNA. In this state, pyrene labled at the 5'-termini of single-stranded stem of probe H1 would be easily trapped into the hydrophobic cavity of β-CDP because of weak steric hindrance, leading to significant fluorescence enhancement. Once the dynamic assembly was catalyzed by target DNA, a hybridized DNA duplex H1-H2 would be created continuously. In this state, it is difficult for pyrene to enter the cavity of β-CDP due to steric hindrance and weak-binding interaction, leading to a weak fluorescent signal. Thus, target DNA could be detected by this simple mix-and-detect amplification method without the need of expensive and perishable protein enzymes. As low as 10 pM of the target DNA was detected by this assay, which was comparable to that of some reported enzyme-dependent amplification methods. Meanwhile, the proposed method was further successfully applied to detect DNA in cell lysate samples, showing great potential for target detection from complex fluids. In addition, as a novel transformation of dynamic DNA assembly technology into enzyme-free signal-amplification analytical application, the proposed strategy has shown great potential for applications in a wide range of fields, such as aptamer-based non-nucleic acid target sensing, biomedicine and bioimaging.

  9. Amplified fluorescence detection of adenosine via catalyzed hairpin assembly and host-guest interactions between β-cyclodextrin polymer and pyrene.

    PubMed

    Huang, Haihua; Yang, Xiaohai; Wang, Kemin; Wang, Qing; Guo, Qiuping; Huang, Jin; Liu, Jianbo; Song, Chunxia

    2016-04-21

    Nowadays, enzyme-free nucleic acid-based signal amplification strategies are frequently utilized in the design of biosensors due to their excellent sensitivity. Developing more extended analytical methods is fundamental for basic studies in the biological and biomedical fields. Herein, we introduce an enzyme-free amplified detection strategy for the small molecule adenosine. The approach is based on adenosine-aptamer binding triggered catalyzed hairpin assembly and host-guest interactions between β-cyclodextrin polymer (β-CDP) and pyrene. Two hairpin probes (probe H1 and probe H2) and an aptamer-trigger/inhibitor duplex probe were employed in the system and the pyrene-labeled probe H1 was chosen as the signal unit. In the absence of adenosine, the aptamer-trigger was inhibited by the inhibitor strand. The hairpin probes were in the closed hairpin formation without activation of the trigger strand. Pyrene labeled at the 5'-termini of the single-stranded stem of probe H1 could be easily trapped in the hydrophobic cavity of β-CDP because of weak steric hindrance, leading to a significant fluorescence enhancement. Once the hairpin assembly was catalyzed by the adenosine-aptamer binding event, a hybridized DNA duplex H1/H2 was created continuously. Pyrene labeled at the 5'-termini of the DNA duplex H1/H2 finds it difficult to enter the cavity of β-CDP due to steric hindrance, leading to a weaker fluorescence signal. Thus, the target could be detected by this simple mix-and-detect amplification method without a need for expensive and perishable protein enzymes. As low as 42 nM of adenosine was detected by this assay, which is comparable to that of some reported colorimetric methods. Meanwhile, the proposed method was further successfully applied to detect adenosine in human serum samples, showing great potential for adenosine detection from complex fluids.

  10. Competing noncovalent host-guest interactions and H/D exchange: reactions of benzyloxycarbonyl-proline glycine dipeptide variants with ND3.

    PubMed

    Miladi, Mahsan; Olaitan, Abayomi D; Zekavat, Behrooz; Solouki, Touradj

    2015-11-01

    A combination of density functional theory calculations, hydrogen/deuterium exchange (HDX) reactions, ion mobility-mass spectrometry, and isotope labeling tandem mass spectrometry was used to study gas-phase "host-guest" type interactions of a benzyloxycarbonyl (Z)-capped proline (P) glycine (G) model dipeptide (i.e., Z-PG) and its various structural analogues with ND3. It is shown that in a solvent-free environment, structural differences between protonated and alkali metal ion (Na(+), K(+), or Cs(+))-complexed species of Z-PG affect ND3 adduct formation. Specifically, [Z-PG + H](+) and [Z-PG-OCH3 + H](+) formed gas-phase ND3 adducts ([Z-PG (or Z-PG-OCH3) + H + ND3](+)) but no ND3 adducts were observed for [Z-PG + alkali metal](+) or [Z-PG + H - CO2](+). Experimentally measured and theoretically calculated collision cross sections (CCSs) of protonated and alkali metal ion-complexed Z-PG species showed similar trends that agreed with the observed structural differences from molecular modeling results. Moreover, results from theoretical ND3 affinity calculations were consistent with experimental HDX observations, indicating a more stable ND3 adduct for [Z-PG + H](+) compared to [Z-PG + alkali metal](+) species. Molecular modeling and experimental MS results for [Z-PG + H](+) and [Z-PG + alkali metal](+) suggest that optimized cation-π and hydrogen bonding interactions of carbonyl groups in final products are important for ND3 adduct formation. Graphical Abstract ᅟ. PMID:26289383

  11. On chip shapeable optical tweezers

    NASA Astrophysics Data System (ADS)

    Renaut, C.; Cluzel, B.; Dellinger, J.; Lalouat, L.; Picard, E.; Peyrade, D.; Hadji, E.; de Fornel, F.

    2013-07-01

    Particles manipulation with optical forces is known as optical tweezing. While tweezing in free space with laser beams was established in the 1980s, integrating the optical tweezers on a chip is a challenging task. Recent experiments with plasmonic nanoantennas, microring resonators, and photonic crystal nanocavities have demonstrated optical trapping. However, the optical field of a tweezer made of a single microscopic resonator cannot be shaped. So far, this prevents from optically driven micromanipulations. Here we propose an alternative approach where the shape of the optical trap can be tuned by the wavelength in coupled nanobeam cavities. Using these shapeable tweezers, we present micromanipulation of polystyrene microspheres trapped on a silicon chip. These results show that coupled nanobeam cavities are versatile building blocks for optical near-field engineering. They open the way to much complex integrated tweezers using networks of coupled nanobeam cavities for particles or bio-objects manipulation at a larger scale.

  12. Undergraduate Construction of Optical Tweezers

    NASA Astrophysics Data System (ADS)

    Hubbell, Lawrence

    2012-10-01

    I will present a poster on the construction of optical tweezers. This will demonstrate the full process one must go through when working on a research project. First I sifted through the internet for papers and information pertaining to the tweezers. Afterwards I discussed the budget with the lab manager. Next I made purchases, however some items, such as the sample mount, needed to be custom made. These I built in the machine shop. Once the tweezers were operational I spent some time ensuring that the mirrors and lenses were adjusted just right, so that the trap performed at full strength. Finally, I used video data of the Brownian motion of trapped silica microspheres to get a reasonable estimate of the trapping stiffness with such particles. As a general note, all of this was done with the intent of leaving the tweezers for future use by other undergraduates. Because of this extra effort was taken to ensure the tweezers were as safe to use as possible. For this reason a visible LASER was chosen over an infrared LASER, in addition, the LASER was oriented parallel to the surface of the table in order to avoid stray upwards beams.

  13. Magnetic tweezers for intracellular applications

    NASA Astrophysics Data System (ADS)

    Hosu, Basarab G.; Jakab, Károly; Bánki, Péter; Tóth, Ferenc I.; Forgacs, Gabor

    2003-09-01

    We have designed and constructed a versatile magnetic tweezer primarily for intracellular investigations. The micromanipulator uses only two coils to simultaneously magnetize to saturation micron-size superparamagnetic particles and generate high magnitude constant field gradients over cellular dimensions. The apparatus resembles a miniaturized Faraday balance, an industrial device used to measure magnetic susceptibility. The device operates in both continuous and pulse modes. Due to its compact size, the tweezers can conveniently be mounted on the stage of an inverted microscope and used for intracellular manipulations. A built-in temperature control unit maintains the sample at physiological temperatures. The operation of the tweezers was tested by moving 1.28 μm diameter magnetic beads inside macrophages with forces near 500 pN.

  14. Theoretical exploration of the nanoscale host-guest interactions between [n]cycloparaphenylenes (n = 10, 8 and 9) and fullerene C₆₀: from single- to three-potential well.

    PubMed

    Yuan, Kun; Zhou, Cai-Hua; Zhu, Yuan-Cheng; Zhao, Xiang

    2015-07-28

    The nanoscale host-guest interactions between [n]cycloparaphenylene ([n]CPP; n = 10, 8 and 9) nano-ring and fullerene C60 were explored theoretically. It is found that relatively small variations in the sizes of the [n]CPP host lead to very significant changes in encapsulation property toward the fullerene C60 guest. Expectedly, one stable inclusion-configuration of [10]CPP⊃C60 and one floating-configuration of [8]CPP⊃C60 are located on the potential surfaces of the two complexes, respectively. Unexpectedly, besides a floating-configuration (F-[9]CPP⊃C60), another stable inclusion-configuration (I-[9]CPP⊃C60) is also located on the potential surface of [9]CPP⊃C60 host-guest complex. Interaction energies and natural steric analysis show that these complexes are stabilized by balancing concave-convex π-π attractive and steric repulsive host-guest interactions. In contrast, the steric repulsive energy (Es) between host and guest of I-[9]CPP⊃C60 is as high as 233.12 kJ mol(-1), which is much larger than those in other complexes. The movements of C60 guest through the cavities of [n]CPP host (n = 10, 8 and 9) are simulated by calculating the energy profile, and the results interestingly reveal that the encapsulation of C60 by [10]CPP is in the manner of a single-potential well, by [8]CPP in the manner of a double-potential well, and by [9]CPP in the special manner of a three-potential well. We predict that the movement of C60 guest through the cavity of [9]CPP host should be experimentally observable owing to the relatively low energy barrier (<50 kJ mol(-1), M06-2X/6-31G(d)). Charge population analysis shows that an obvious charge transfer between host and guest takes place during the formation of I-[9]CPP⊃C60, which is different from those during the formation of [8]CPP⊃C60, [10]CPP⊃C60 and F-[9]CPP⊃C60. Additionally, the host-guest interaction regions were detected and visualized in real space based on the electron density and reduced density

  15. Ultrasensitive electrochemical immunoassay for CEA through host-guest interaction of β-cyclodextrin functionalized graphene and Cu@Ag core-shell nanoparticles with adamantine-modified antibody.

    PubMed

    Gao, Jian; Guo, Zhankui; Su, Fengjie; Gao, Liang; Pang, Xuehui; Cao, Wei; Du, Bin; Wei, Qin

    2015-01-15

    A novel non-enzymatic immunoassay was designed for ultrasensitive electrochemical detection of carcino-embryonic antigen (CEA) using β-cyclodextrin functionalized Cu@Ag (Cu@Ag-CD) core-shell nanoparticles as labels and β-cyclodextrin functionalized graphene nanosheet (CD-GN) as sensor platform. CD-GN has excellent conductivity which promoted the electric transmission between base solution and electrode surface and enhanced sensitivity of immunosensor. In addition, owing to supramolecular recognition of CD-GN for the guest molecule, quite a few synthesized adamantine-modified primary antibodies (ADA-Ab1) were immobilized on the CD-GN by supramolecular host-guest interaction between CD and ADA. Cu@Ag-CD as a signal tag could be captured by ADA-modified secondary antibody (ADA-Ab2) through a host-guest interaction, leading to a large loading of Cu@Ag nanoparticles with high electrical conductivity and catalytic activity. The fabricated immunosensor exhibits excellent analytical performance for the measurement of CEA with wide range linear (0.0001-20 ng/mL), low detection limit (20 fg/mL), good sensitivity, reproducibility and stability, which provide an enormous application prospect in clinical diagnostics.

  16. Optical tweezers technique and its applications

    NASA Astrophysics Data System (ADS)

    Guo, HongLian; Li, ZhiYuan

    2013-12-01

    Since their advent in the 1980s, optical tweezers have attracted more and more attention due to their unique non-contact and non-invasion characteristics and their wide applications in physics, biology, chemistry, medical science and nanoscience. In this paper, we introduce the basic principle, the history and typical applications of optical tweezers and review our recent experimental works on the development and application of optical tweezers technique. We will discuss in detail several technological issues, including high precision displacement and force measurement in single-trap and dual-trap optical tweezers, multi-trap optical tweezers with each trap independently and freely controlled by means of space light modulator, and incorporation of cylindrical vector optical beams to build diversified optical tweezers beyond the conventional Gaussian-beam optical tweezers. We will address the application of these optical tweezers techniques to study biophysical problems such as mechanical deformation of cell membrane and binding energy between plant microtubule and microtubule associated proteins. Finally we present application of the optical tweezers technique for trapping, transporting, and patterning of metallic nanoparticles, which can be harnessed to manipulate surface plasmon resonance properties of these nanoparticles.

  17. Bright Fluorescence and Host-Guest Sensing with a Nanoscale M₄L₆ Tetrahedron Accessed by Self-Assembly of Zinc-Imine Chelate Vertices and Perylene Bisimide Edges.

    PubMed

    Frischmann, Peter D; Kunz, Valentin; Würthner, Frank

    2015-06-15

    A highly luminescent Zn4L6 tetrahedron is reported with 3.8 nm perylene bisimide edges and hexadentate Zn(II)-imine chelate vertices. Replacing Fe(II) and monoamines commonly utilized in subcomponent self-assembly with Zn(II) and tris(2-aminoethyl)amine provides access to a metallosupramolecular host with the rare combination of structural integrity at concentrations <10(-7) mol L(-1) and an exceptionally high fluorescence quantum yield of Φ(em) =0.67. Encapsulation of multiple perylene or coronene guest molecules is accompanied by strong luminescence quenching. We anticipate this self-assembly strategy may be generalized to improve access to brightly fluorescent coordination cages tailored for host-guest light-harvesting, photocatalysis, and sensing.

  18. Host-Guest Inclusion Complexes between Amlodipine Enantiomers in the Biphasic Recognition Chiral Extraction System using Tartaric Acid and β-Cyclodextrin Derivatives as Positive Confirmation by using their Enantioselective Extraction

    PubMed Central

    Al Azzam, Khaldun M.; Abdallah, Hassan H.; Halim, Hairul N. Abdul; Ahmad, Maizatul Akmam; Shaibah, Hassan

    2015-01-01

    The current work reports an extended theoretical study from our previous experimental work for the enantioselective extraction of amlodipine enantiomers in a biphasic recognition chiral extraction system (BRCES) consisting of hydrophobic D-diisopropyl tartrate dissolved in organic phase (n-decanol) and hydrophilic hydroxypropyl-β-cyclodextrin (HP-β-CD) in aqueous phase (acetate buffer) which preferentially recognize the R-enantiomer and S-enantiomer, respectively. The calculations were simulated using a semi-empirical PM3 method as a part of the Gaussian09 software package and were used to optimize the structures of the hosts, guests, and host-guest complexes in the gas phase without any restrictions. It was found that HP-β-CD has the strongest recognition ability among the three β-CD derivatives studied, namely HP-β-CD, hydroxyethyl-β-cyclodextrin (HE-β-CD), and methylated-β-cyclodextrin (Me-β-CD), due to the large interaction energies (Ecomp = −14.3025 kcal/ mol), while D-diisopropyl tartrate has the strongest ability among the four tartaric acid derivatives studied namely; L-diisopropyl tartrate, D-diisopropyl tartrate, L-diethyl tartrate, and D-diethyl tartrate (Ecomp = −5.9964 kcal/ mol). The computational calculations for the enantioselective partitioning of amlodipine enantiomers rationalized the reasons for the different behaviors for this extraction. The present theoretical results may be informative to scientists who are devoting themselves to developing models for their experimental parts or for enhancing the hydrophobic drug solubility in drug delivery systems. PMID:26839848

  19. A new dual-signalling electrochemical sensing strategy based on competitive host-guest interaction of a β-cyclodextrin/poly(N-acetylaniline)/graphene-modified electrode: sensitive electrochemical determination of organic pollutants.

    PubMed

    Zhu, Gangbing; Wu, Liang; Zhang, Xia; Liu, Wei; Zhang, Xiaohua; Chen, Jinhua

    2013-05-10

    Based on the competitive host-guest interaction between a β-cyclodextrin/poly(N-acetylaniline)/electrogenerated-graphene (β-CD/PNAANI/EG) film and probe or target molecules, a new dual-signalling electrochemical sensing method has been developed for the sensitive and selective determination of organic pollutants. As a model system, rhodamine B (RhB) and 1-aminopyrene (1-AP) were adopted as the probe and target molecules, respectively. Due to the host-guest interaction, RhB molecules can enter into the hydrophobic inner cavity of β-CD, and the β-CD/PNAANI/EG-modified glassy carbon electrode displays a remarkable oxidation peak due to RhB. In the presence of 1-AP, competitive association to β-CD occurs and the RhB molecules are displaced by 1-AP. This results in a decreased oxidation peak current of RhB and the appearance of an oxidation peak current for 1-AP, and the changes of these signals correlate linearly with the concentration of 1-AP. When the value ΔI(1-AP)+∣ΔI(RhB)∣ (ΔI(1-AP) and ΔI(RhB) are the change values of the oxidation peak currents of 1-AP and RhB, respectively) is used as the response signal to quantitatively determine the concentration of 1-AP, the detection limit is much lower than that given by using ΔI(1-AP) or ΔI(RhB) as the response signal. This dual-signalling sensor can provide more sensitive target recognition and will have important applications in the sensitive and selective electrochemical determination of electroactive organic pollutants.

  20. Making light work with optical tweezers

    NASA Astrophysics Data System (ADS)

    Block, Steven M.

    1992-12-01

    Microscopic objects, including biological material, can be remotely manipulated with tightly focused beams of infrared laser light. The use of optical traps, or 'optical tweezers', holds great promise for noninvasive micromanipulation and mechanical measurement in cell biology. Optical tweezers are the 'tractor beams' of today's technology.

  1. Optoelectronic tweezers for medical diagnostics

    NASA Astrophysics Data System (ADS)

    Kremer, Clemens; Neale, Steven; Menachery, Anoop; Barrett, Mike; Cooper, Jonathan M.

    2012-01-01

    Optoelectronic tweezers (OET) allows the spatial patterning of electric fields through selected illumination of a photoconductive surface. This enables the manipulation of micro particles and cells by creating non-uniform electrical fields that then produce dielectrophoretic (DEP) forces. The DEP responses of cells differ and can produce negative or positive (repelled or attracted to areas of high electric field) forces. Therefore OET can be used to manipulate individual cells and separate different cell types from each other. Thus OET has many applications for medical diagnostics, demonstrated here with work towards diagnosing Human African Trypanosomiasis, also known as sleeping sickness.

  2. Cell rotation using optoelectronic tweezers.

    PubMed

    Liang, Yuan-Li; Huang, Yuan-Peng; Lu, Yen-Sheng; Hou, Max T; Yeh, J Andrew

    2010-01-01

    A cell rotation method by using optoelectronic tweezers (OET) is reported. The binary image of a typical OET device, whose light and dark sides act as two sets of parallel plates with different ac voltages, was used to create a rotating electric field. Its feasibility for application to electrorotation of cells was demonstrated by rotating Ramos and yeast cells in their pitch axes. The electrorotation by using OET devices is dependent on the medium and cells' electrical properties, the cells' positions, and the OET device's geometrical dimension, as well as the frequency of the electric field. PMID:21267435

  3. Microcrystal manipulation with laser tweezers

    PubMed Central

    Wagner, Armin; Duman, Ramona; Stevens, Bob; Ward, Andy

    2013-01-01

    X-ray crystallography is the method of choice to deduce atomic resolution structural information from macromolecules. In recent years, significant investments in structural genomics initiatives have been undertaken to automate all steps in X-ray crystallography from protein expression to structure solution. Robotic systems are widely used to prepare crystallization screens and change samples on synchrotron beamlines for macromolecular crystallography. The only remaining manual handling step is the transfer of the crystal from the mother liquor onto the crystal holder. Manual mounting is relatively straightforward for crystals with dimensions of >25 µm; however, this step is nontrivial for smaller crystals. The mounting of microcrystals is becoming increasingly important as advances in microfocus synchrotron beamlines now allow data collection from crystals with dimensions of only a few micrometres. To make optimal usage of these beamlines, new approaches have to be taken to facilitate and automate this last manual handling step. Optical tweezers, which are routinely used for the manipulation of micrometre-sized objects, have successfully been applied to sort and mount macromolecular crystals on newly designed crystal holders. Diffraction data from CPV type 1 polyhedrin microcrystals mounted with laser tweezers are presented. PMID:23793156

  4. Quantum limited particle sensing in optical tweezers

    SciTech Connect

    Tay, J.W.; Hsu, Magnus T. L.; Bowen, Warwick P.

    2009-12-15

    Particle sensing in optical tweezers systems provides information on the position, velocity, and force of the specimen particles. The conventional quadrant detection scheme is applied ubiquitously in optical tweezers experiments to quantify these parameters. In this paper, we show that quadrant detection is nonoptimal for particle sensing in optical tweezers and propose an alternative optimal particle sensing scheme based on spatial homodyne detection. A formalism for particle sensing in terms of transverse spatial modes is developed and numerical simulations of the efficacies of both quadrant and spatial homodyne detection are shown. We demonstrate that 1 order of magnitude improvement in particle sensing sensitivity can be achieved using spatial homodyne over quadrant detection.

  5. A DNA tweezer-actuated enzyme nanoreactor.

    PubMed

    Liu, Minghui; Fu, Jinglin; Hejesen, Christian; Yang, Yuhe; Woodbury, Neal W; Gothelf, Kurt; Liu, Yan; Yan, Hao

    2013-01-01

    The functions of regulatory enzymes are essential to modulating cellular pathways. Here we report a tweezer-like DNA nanodevice to actuate the activity of an enzyme/cofactor pair. A dehydrogenase and NAD(+) cofactor are attached to different arms of the DNA tweezer structure and actuation of enzymatic function is achieved by switching the tweezers between open and closed states. The enzyme/cofactor pair is spatially separated in the open state with inhibited enzyme function, whereas in the closed state, enzyme is activated by the close proximity of the two molecules. The conformational state of the DNA tweezer is controlled by the addition of specific oligonucleotides that serve as the thermodynamic driver (fuel) to trigger the change. Using this approach, several cycles of externally controlled enzyme inhibition and activation are successfully demonstrated. This principle of responsive enzyme nanodevices may be used to regulate other types of enzymes and to introduce feedback or feed-forward control loops.

  6. Steerable optical tweezers for ultracold atom studies.

    PubMed

    Roberts, K O; McKellar, T; Fekete, J; Rakonjac, A; Deb, A B; Kjærgaard, N

    2014-04-01

    We report on the implementation of an optical tweezer system for controlled transport of ultracold atoms along a narrow, static confinement channel. The tweezer system is based on high-efficiency acousto-optic deflectors and offers two-dimensional control over beam position. This opens up the possibility for tracking the transport channel when shuttling atomic clouds along it, forestalling atom spilling. Multiple clouds can be tracked independently by time-shared tweezer beams addressing individual sites in the channel. The deflectors are controlled using a multichannel direct digital synthesizer, which receives instructions on a submicrosecond time scale from a field-programmable gate array. Using the tweezer system, we demonstrate sequential binary splitting of an ultracold 87Rb cloud into 2(5) clouds.

  7. Characterizing conical refraction optical tweezers.

    PubMed

    McDonald, C; McDougall, C; Rafailov, E; McGloin, D

    2014-12-01

    Conical refraction occurs when a beam of light travels through an appropriately cut biaxial crystal. By focusing the conically refracted beam through a high numerical aperture microscope objective, conical refraction optical tweezers can be created, allowing for particle manipulation in both Raman spots, and in the Lloyd/Poggendorff rings. We present a thorough quantification of the trapping properties of such a beam, focusing on the trap stiffness, and how this varies with trap power and trapped particle location. We show that the lower Raman spot can be thought of as a single-beam optical gradient force trap, while radiation pressure dominates in the upper Raman spot, leading to optical levitation rather than trapping. Particles in the Lloyd/Poggendorff rings experience a lower trap stiffness than particles in the lower Raman spot, but benefit from rotational control. PMID:25490654

  8. Artificial neural networks for determination of enantiomeric composition of alpha-phenylglycine using UV spectra of cyclodextrin host-guest complexes: comparison of feed-forward and radial basis function networks.

    PubMed

    Afkhami, Abbas; Abbasi-Tarighat, Maryam; Bahram, Morteza

    2008-03-15

    In this work feed-forward neural networks and radial basis function networks were used for the determination of enantiomeric composition of alpha-phenylglycine using UV spectra of cyclodextrin host-guest complexes and the data provided by two techniques were compared. Wavelet transformation (WT) and principal component analysis (PCA) were used for data compression prior to neural network construction and their efficiencies were compared. The structures of the wavelet transformation-radial basis function networks (WT-RBFNs) and wavelet transformation-feed-forward neural networks (WT-FFNNs), were simplified by using the corresponding wavelet coefficients of three mother wavelets (Mexican hat, daubechies and symlets). Dilation parameters, number of inputs, hidden nodes, learning rate, transfer functions, number of epochs and SPREAD values were optimized. Performances of the proposed methods were tested with regard to root mean square errors of prediction (RMSE%), using synthetic solutions containing a fixed concentration of beta-cyclodextrin (beta-CD) and fixed concentration of alpha-phenylglycine (alpha-Gly) with different enantiomeric compositions. Although satisfactory results with regard to some statistical parameters were obtained for all the investigated methods but the best results were achieved by WT-RBFNs.

  9. Single-molecule force spectroscopy: optical tweezers, magnetic tweezers and atomic force microscopy

    PubMed Central

    Neuman, Keir C.; Nagy, Attila

    2012-01-01

    Single-molecule force spectroscopy has emerged as a powerful tool to investigate the forces and motions associated with biological molecules and enzymatic activity. The most common force spectroscopy techniques are optical tweezers, magnetic tweezers and atomic force microscopy. These techniques are described and illustrated with examples highlighting current capabilities and limitations. PMID:18511917

  10. Magnetic Tweezers for the Measurement of Twist and Torque

    PubMed Central

    Lipfert, Jan; Lee, Mina; Ordu, Orkide; Kerssemakers, Jacob W. J.; Dekker, Nynke H.

    2014-01-01

    Single-molecule techniques make it possible to investigate the behavior of individual biological molecules in solution in real time. These techniques include so-called force spectroscopy approaches such as atomic force microscopy, optical tweezers, flow stretching, and magnetic tweezers. Amongst these approaches, magnetic tweezers have distinguished themselves by their ability to apply torque while maintaining a constant stretching force. Here, it is illustrated how such a “conventional” magnetic tweezers experimental configuration can, through a straightforward modification of its field configuration to minimize the magnitude of the transverse field, be adapted to measure the degree of twist in a biological molecule. The resulting configuration is termed the freely-orbiting magnetic tweezers. Additionally, it is shown how further modification of the field configuration can yield a transverse field with a magnitude intermediate between that of the “conventional” magnetic tweezers and the freely-orbiting magnetic tweezers, which makes it possible to directly measure the torque stored in a biological molecule. This configuration is termed the magnetic torque tweezers. The accompanying video explains in detail how the conversion of conventional magnetic tweezers into freely-orbiting magnetic tweezers and magnetic torque tweezers can be accomplished, and demonstrates the use of these techniques. These adaptations maintain all the strengths of conventional magnetic tweezers while greatly expanding the versatility of this powerful instrument. PMID:24894412

  11. Designing single-beam multitrapping acoustical tweezers.

    PubMed

    Silva, Glauber T; Baggio, André L

    2015-02-01

    The concept of a single-beam acoustical tweezer device which can simultaneously trap microparticles at different points is proposed and demonstrated through computational simulations. The device employs an ultrasound beam produced by a circular focused transducer operating at 1 MHz in water medium. The ultrasound beam exerts a radiation force that may tweeze suspended microparticles in the medium. Simulations show that the acoustical tweezer can simultaneously trap microparticles in the pre-focal zone along the beam axis, i.e. between the transducer surface and its geometric focus. As acoustical tweezers are fast becoming a key instrument in microparticle handling, the development of acoustic multitrapping concept may turn into a useful tool in engineering these devices.

  12. Designing single-beam multitrapping acoustical tweezers.

    PubMed

    Silva, Glauber T; Baggio, André L

    2015-02-01

    The concept of a single-beam acoustical tweezer device which can simultaneously trap microparticles at different points is proposed and demonstrated through computational simulations. The device employs an ultrasound beam produced by a circular focused transducer operating at 1 MHz in water medium. The ultrasound beam exerts a radiation force that may tweeze suspended microparticles in the medium. Simulations show that the acoustical tweezer can simultaneously trap microparticles in the pre-focal zone along the beam axis, i.e. between the transducer surface and its geometric focus. As acoustical tweezers are fast becoming a key instrument in microparticle handling, the development of acoustic multitrapping concept may turn into a useful tool in engineering these devices. PMID:25304994

  13. Micro-objective manipulated with optical tweezers

    SciTech Connect

    Sasaki, M.; Kurosawa, T.; Hane, K.

    1997-02-01

    A microscope is described that uses a {mu}m-sized ball lens, which is here termed micro-objective, manipulated with optical tweezers to image the side view of the arbitrary region of a sample. Since this micro-objective is small in size, it can go into a concave region to produce a local image of the inside which the conventional microscope cannot observe. Preliminary results show good lens performance from the micro-objective when combined with optical tweezers. {copyright} {ital 1997 American Institute of Physics.}

  14. Molecular tweezers targeting transthyretin amyloidosis.

    PubMed

    Ferreira, Nelson; Pereira-Henriques, Alda; Attar, Aida; Klärner, Frank-Gerrit; Schrader, Thomas; Bitan, Gal; Gales, Luís; Saraiva, Maria João; Almeida, Maria Rosário

    2014-04-01

    Transthyretin (TTR) amyloidoses comprise a wide spectrum of acquired and hereditary diseases triggered by extracellular deposition of toxic TTR aggregates in various organs. Despite recent advances regarding the elucidation of the molecular mechanisms underlying TTR misfolding and pathogenic self-assembly, there is still no effective therapy for treatment of these fatal disorders. Recently, the "molecular tweezers", CLR01, has been reported to inhibit self-assembly and toxicity of different amyloidogenic proteins in vitro, including TTR, by interfering with hydrophobic and electrostatic interactions known to play an important role in the aggregation process. In addition, CLR01 showed therapeutic effects in animal models of Alzheimer's disease and Parkinson's disease. Here, we assessed the ability of CLR01 to modulate TTR misfolding and aggregation in cell culture and in an animal model. In cell culture assays we found that CLR01 inhibited TTR oligomerization in the conditioned medium and alleviated TTR-induced neurotoxicity by redirecting TTR aggregation into the formation of innocuous assemblies. To determine whether CLR01 was effective in vivo, we tested the compound in mice expressing TTR V30M, a model of familial amyloidotic polyneuropathy, which recapitulates the main pathological features of the human disease. Immunohistochemical and Western blot analyses showed a significant decrease in TTR burden in the gastrointestinal tract and the peripheral nervous system in mice treated with CLR01, with a concomitant reduction in aggregate-induced endoplasmic reticulum stress response, protein oxidation, and apoptosis. Taken together, our preclinical data suggest that CLR01 is a promising lead compound for development of innovative, disease-modifying therapy for TTR amyloidosis.

  15. A force calibration standard for magnetic tweezers

    NASA Astrophysics Data System (ADS)

    Yu, Zhongbo; Dulin, David; Cnossen, Jelmer; Köber, Mariana; van Oene, Maarten M.; Ordu, Orkide; Berghuis, Bojk A.; Hensgens, Toivo; Lipfert, Jan; Dekker, Nynke H.

    2014-12-01

    To study the behavior of biological macromolecules and enzymatic reactions under force, advances in single-molecule force spectroscopy have proven instrumental. Magnetic tweezers form one of the most powerful of these techniques, due to their overall simplicity, non-invasive character, potential for high throughput measurements, and large force range. Drawbacks of magnetic tweezers, however, are that accurate determination of the applied forces can be challenging for short biomolecules at high forces and very time-consuming for long tethers at low forces below ˜1 piconewton. Here, we address these drawbacks by presenting a calibration standard for magnetic tweezers consisting of measured forces for four magnet configurations. Each such configuration is calibrated for two commonly employed commercially available magnetic microspheres. We calculate forces in both time and spectral domains by analyzing bead fluctuations. The resulting calibration curves, validated through the use of different algorithms that yield close agreement in their determination of the applied forces, span a range from 100 piconewtons down to tens of femtonewtons. These generalized force calibrations will serve as a convenient resource for magnetic tweezers users and diminish variations between different experimental configurations or laboratories.

  16. An optical tweezer for complex plasmas

    SciTech Connect

    Schablinski, Jan; Wieben, Frank; Block, Dietmar

    2015-04-15

    This paper describes the experimental realization of an optical trap for microparticles levitating in the plasma sheath. Single particles can be trapped in a laser beam comparable to optical tweezers known from colloidal suspensions. The trapping mechanism is discussed and two applications of the system are shown.

  17. Optoelectronic Tweezers for Microparticle and Cell Manipulation

    NASA Technical Reports Server (NTRS)

    Wu, Ming Chiang (Inventor); Chiou, Pei-Yu (Inventor); Ohta, Aaron T. (Inventor)

    2014-01-01

    An optical image-driven light induced dielectrophoresis (DEP) apparatus and method are described which provide for the manipulation of particles or cells with a diameter on the order of 100 micromillimeters or less. The apparatus is referred to as optoelectric tweezers (OET) and provides a number of advantages over conventional optical tweezers, in particular the ability to perform operations in parallel and over a large area without damage to living cells. The OET device generally comprises a planar liquid-filled structure having one or more portions which are photoconductive to convert incoming light to a change in the electric field pattern. The light patterns are dynamically generated to provide a number of manipulation structures that can manipulate single particles and cells or group of particles/cells. The OET preferably includes a microscopic imaging means to provide feedback for the optical manipulation, such as detecting position and characteristics wherein the light patterns are modulated accordingly.

  18. Optoelectronic tweezers for microparticle and cell manipulation

    NASA Technical Reports Server (NTRS)

    Wu, Ming Chiang (Inventor); Chiou, Pei Yu (Inventor); Ohta, Aaron T. (Inventor)

    2009-01-01

    An optical image-driven light induced dielectrophoresis (DEP) apparatus and method are described which provide for the manipulation of particles or cells with a diameter on the order of 100 .mu.m or less. The apparatus is referred to as optoelectric tweezers (OET) and provides a number of advantages over conventional optical tweezers, in particular the ability to perform operations in parallel and over a large area without damage to living cells. The OET device generally comprises a planar liquid-filled structure having one or more portions which are photoconductive to convert incoming light to a change in the electric field pattern. The light patterns are dynamically generated to provide a number of manipulation structures that can manipulate single particles and cells or groups of particles/cells. The OET preferably includes a microscopic imaging means to provide feedback for the optical manipulation, such as detecting position and characteristics wherein the light patterns are modulated accordingly.

  19. Exploring unconventional capabilities of holographic tweezers

    NASA Astrophysics Data System (ADS)

    Hernandez, R. J.; Pagliusi, P.; Provenzano, C.; Cipparrone, G.

    2011-06-01

    We report an investigation of manipulation and trapping capabilities of polarization holographic tweezers. A polarization gradient connected with a modulation of the ellipticity shows an optical force related to the polarization of the light that can influence optically isotropic particles. While in the case of birefringent particles an unconventional trapping in circularly polarized fringes is observed. A liquid crystal emulsion has been adopted to investigate the capabilities of the holographic tweezers. The unusual trapping observed for rotating bipolar nematic droplets has suggested the involvement of the lift hydrodynamic force responsible of the Magnus effect, originating from the peculiar optical force field. We show that the Magnus force which is ignored in the common approach can contribute to unconventional optohydrodynamic trapping and manipulation.

  20. Independent trapping and manipulation of microparticles using dexterous acoustic tweezers

    SciTech Connect

    Courtney, Charles R. P.; Demore, Christine E. M.; Wu, Hongxiao; Cochran, Sandy; Grinenko, Alon; Wilcox, Paul D.; Drinkwater, Bruce W.

    2014-04-14

    An electronically controlled acoustic tweezer was used to demonstrate two acoustic manipulation phenomena: superposition of Bessel functions to allow independent manipulation of multiple particles and the use of higher-order Bessel functions to trap particles in larger regions than is possible with first-order traps. The acoustic tweezers consist of a circular 64-element ultrasonic array operating at 2.35 MHz which generates ultrasonic pressure fields in a millimeter-scale fluid-filled chamber. The manipulation capabilities were demonstrated experimentally with 45 and 90-μm-diameter polystyrene spheres. These capabilities bring the dexterity of acoustic tweezers substantially closer to that of optical tweezers.

  1. Tweezers for Chimeras in Small Networks

    NASA Astrophysics Data System (ADS)

    Omelchenko, Iryna; Omel'chenko, Oleh E.; Zakharova, Anna; Wolfrum, Matthias; Schöll, Eckehard

    2016-03-01

    We propose a control scheme which can stabilize and fix the position of chimera states in small networks. Chimeras consist of coexisting domains of spatially coherent and incoherent dynamics in systems of nonlocally coupled identical oscillators. Chimera states are generally difficult to observe in small networks due to their short lifetime and erratic drifting of the spatial position of the incoherent domain. The control scheme, like a tweezer, might be useful in experiments, where usually only small networks can be realized.

  2. Fractal zone plate beam based optical tweezers

    NASA Astrophysics Data System (ADS)

    Cheng, Shubo; Zhang, Xinyu; Ma, Wenzhuo; Tao, Shaohua

    2016-09-01

    We demonstrate optical manipulation with an optical beam generated by a fractral zone plate (FZP). The experimental results show that the FZP beam can simultaneously trap multiple particles positioned in different focal planes of the FZP beam, owing to the multiple foci and self-reconstruction property of the FZP beam. The FZP beam can also be used to construct three-dimensional optical tweezers for potential applications.

  3. The Smallest Tweezers in the World

    ERIC Educational Resources Information Center

    Lewalle, Alexandre

    2008-01-01

    A pair of fine tweezers and a steady hand may well be enough to pick up a grain of sand, but what would you use to hold something hundreds of times smaller still, the size of only one micron? The answer is to use a device that is not mechanical in nature but that relies instead on the tiny forces that light exerts on small particles: "optical…

  4. Interactive approach to optical tweezers control

    SciTech Connect

    Leach, Jonathan; Wulff, Kurt; Sinclair, Gavin; Jordan, Pamela; Courtial, Johannes; Thomson, Laura; Gibson, Graham; Karunwi, Kayode; Cooper, Jon; Laczik, Zsolt John; Padgett, Miles

    2006-02-10

    We have developed software with an interactive user interface that can be used to generate phase holograms for use with spatial light modulators. The program utilizes different hologram design techniques, allowing the user to select an appropriate algorithm. The program can be used to generate multiple beams and can be used for beam steering. We see a major application of the program to be in optical tweezers to control the position, number, and type of optical traps.

  5. Fractal zone plate beam based optical tweezers

    PubMed Central

    Cheng, Shubo; Zhang, Xinyu; Ma, Wenzhuo; Tao, Shaohua

    2016-01-01

    We demonstrate optical manipulation with an optical beam generated by a fractral zone plate (FZP). The experimental results show that the FZP beam can simultaneously trap multiple particles positioned in different focal planes of the FZP beam, owing to the multiple foci and self-reconstruction property of the FZP beam. The FZP beam can also be used to construct three-dimensional optical tweezers for potential applications. PMID:27678305

  6. New approaches in the design of magnetic tweezers-current magnetic tweezers

    NASA Astrophysics Data System (ADS)

    Bessalova, Valentina; Perov, Nikolai; Rodionova, Valeria

    2016-10-01

    The main advantages of the magnetic tweezers are the low price and simplicity of use. However the range of their application is reduced due to shortcomings like, for example, the remanent induction of the core and interaction between ferromagnetic cores. We present the new design of magnetic tweezers-Current Magnetic Tweezers (CMT) that allow particle manipulation by means of the magnetic field generated by the electric currents flowing through the non-magnetic wires. Arranging wires in different geometric shapes allows the particle movement either in two or three dimensions. Forces acting on the magnetic particles with the magnetic moment of 2·10-11 A m2 at distances up to 1 mm had been experimentally measured. It is established that a current of about 1 A at a 1 mm distance generates force of (approximately) 3 pN which is consistent with theoretical estimates.

  7. 21 CFR 878.5360 - Tweezer-type epilator.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Tweezer-type epilator. 878.5360 Section 878.5360 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Therapeutic Devices § 878.5360 Tweezer-type...

  8. 21 CFR 878.5360 - Tweezer-type epilator.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Tweezer-type epilator. 878.5360 Section 878.5360 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Therapeutic Devices § 878.5360 Tweezer-type...

  9. 21 CFR 878.5360 - Tweezer-type epilator.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Tweezer-type epilator. 878.5360 Section 878.5360 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Therapeutic Devices § 878.5360 Tweezer-type...

  10. 21 CFR 878.5360 - Tweezer-type epilator.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Tweezer-type epilator. 878.5360 Section 878.5360 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Therapeutic Devices § 878.5360 Tweezer-type...

  11. 21 CFR 878.5360 - Tweezer-type epilator.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Tweezer-type epilator. 878.5360 Section 878.5360 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Therapeutic Devices § 878.5360 Tweezer-type...

  12. Modular magnetic tweezers for single-molecule characterizations of helicases.

    PubMed

    Kemmerich, Felix E; Kasaciunaite, Kristina; Seidel, Ralf

    2016-10-01

    Magnetic tweezers provide a versatile toolkit supporting the mechanistic investigation of helicases. In the present article, we show that custom magnetic tweezers setups are straightforward to construct and can easily be extended to provide adaptable platforms, capable of addressing a multitude of enquiries regarding the functions of these fascinating molecular machines. We first address the fundamental components of a basic magnetic tweezers scheme and review some previous results to demonstrate the versatility of this instrument. We then elaborate on several extensions to the basic magnetic tweezers scheme, and demonstrate their applications with data from ongoing research. As our methodological overview illustrates, magnetic tweezers are an extremely useful tool for the characterization of helicases and a custom built instrument can be specifically tailored to suit the experimenter's needs.

  13. Optical Tweezers Array and Nimble Tweezers Probe Generated by Spatial- Light Modulator

    NASA Technical Reports Server (NTRS)

    Decker, Arthur J.; Jassemnejad, Baha; Seibel, Robin E.; Weiland, Kenneth E.

    2003-01-01

    An optical tweezers is being developed at the NASA Glenn Research Center as a visiblelight interface between ubiquitous laser technologies and the interrogation, visualization, manufacture, control, and energization of nanostructures such as silicon carbide (SiC) nanotubes. The tweezers uses one or more focused laser beams to hold micrometer-sized particles called tools (sometimes called tips in atomic-force-microscope terminology). A strongly focused laser beam has an associated light-pressure gradient that is strong enough to pull small particles to the focus, in spite of the oppositely directed scattering force; "optical tweezers" is the common term for this effect. The objective is to use the tools to create carefully shaped secondary traps to hold and assemble nanostructures that may contain from tens to hundreds of atoms. The interaction between a tool and the nanostructures is to be monitored optically as is done with scanning probe microscopes. One of the initial efforts has been to create, shape, and control multiple tweezers beams. To this end, a programmable spatial-light modulator (SLM) has been used to modify the phase of a laser beam at up to 480 by 480 points. One program creates multiple, independently controllable tweezer beams whose shapes can be tailored by making the SLM an adaptive mirror in an interferometer (ref. 1). The beams leave the SLM at different angles, and an optical Fourier transform maps these beams to different positions in the focal plane of a microscope objective. The following figure shows two arrays of multiple beams created in this manner. The patterns displayed above the beam array control the intensity-to-phase transformation required in programming the SLM. Three of the seven beams displayed can be used as independently controllable beams.

  14. Reusable acoustic tweezers for disposable devices.

    PubMed

    Guo, Feng; Xie, Yuliang; Li, Sixing; Lata, James; Ren, Liqiang; Mao, Zhangming; Ren, Baiyang; Wu, Mengxi; Ozcelik, Adem; Huang, Tony Jun

    2015-12-21

    We demonstrate acoustic tweezers used for disposable devices. Rather than forming an acoustic resonance, we locally transmitted standing surface acoustic waves into a removable, independent polydimethylsiloxane (PDMS)-glass hybridized microfluidic superstrate device for micromanipulation. By configuring and regulating the displacement nodes on a piezoelectric substrate, cells and particles were effectively patterned and transported into said superstrate, accordingly. With the label-free and contactless nature of acoustic waves, the presented technology could offer a simple, accurate, low-cost, biocompatible, and disposable method for applications in the fields of point-of-care diagnostics and fundamental biomedical studies.

  15. Active laser tweezers microrheometry of microbial biofilms

    NASA Astrophysics Data System (ADS)

    Osterman, N.; Slapar, V.; Boric, M.; Stopar, D.; Babič, D.; Poberaj, I.

    2010-08-01

    Microbial biofilms are present on biotic and abiotic surfaces and have a significant impact on many fields in industry, health care and technology. Thus, a better understanding of processes that lead to development of biofilms and their chemical and mechanical properties is needed. In the following paper we report the results of active laser tweezers microrheology study of optically inhomogeneous extracellular matrix secreted by Visbrio sp. bacteria. One particle and two particle active microrheology were used in experiments. Both methods exhibited high enough sensitivity to detect viscosity changes at early stages of bacterial growth. We also showed that both methods can be used in mature samples where optical inhomogeneity becomes significant.

  16. Reusable acoustic tweezers for disposable devices

    PubMed Central

    Guo, Feng; Xie, Yuliang; Li, Sixing; Lata, James; Ren, Liqiang; Mao, Zhangming; Ren, Baiyang; Wu, Mengxi; Ozcelik, Adem

    2015-01-01

    We demonstrate acoustic tweezers used for disposable devices. Rather than forming an acoustic resonance, we locally transmitted standing surface acoustic waves into a removable, independent polydimethylsiloxane (PDMS)-glass hybridized microfluidic superstrate device for micromanipulation. By configuring and regulating the displacement nodes on a piezoelectric substrate, cells and particles were effectively patterned and transported into said superstrate, accordingly. With the label-free and contactless nature of acoustic waves, the presented technology could offer a simple, accurate, low-cost, biocompatible, and disposable method for applications in the fields of point-of-care diagnostics and fundamental biomedical studies. PMID:26507411

  17. Quantitative Modeling and Optimization of Magnetic Tweezers

    PubMed Central

    Lipfert, Jan; Hao, Xiaomin; Dekker, Nynke H.

    2009-01-01

    Abstract Magnetic tweezers are a powerful tool to manipulate single DNA or RNA molecules and to study nucleic acid-protein interactions in real time. Here, we have modeled the magnetic fields of permanent magnets in magnetic tweezers and computed the forces exerted on superparamagnetic beads from first principles. For simple, symmetric geometries the magnetic fields can be calculated semianalytically using the Biot-Savart law. For complicated geometries and in the presence of an iron yoke, we employ a finite-element three-dimensional PDE solver to numerically solve the magnetostatic problem. The theoretical predictions are in quantitative agreement with direct Hall-probe measurements of the magnetic field and with measurements of the force exerted on DNA-tethered beads. Using these predictive theories, we systematically explore the effects of magnet alignment, magnet spacing, magnet size, and of adding an iron yoke to the magnets on the forces that can be exerted on tethered particles. We find that the optimal configuration for maximal stretching forces is a vertically aligned pair of magnets, with a minimal gap between the magnets and minimal flow cell thickness. Following these principles, we present a configuration that allows one to apply ≥40 pN stretching forces on ≈1-μm tethered beads. PMID:19527664

  18. Quantitative modeling and optimization of magnetic tweezers.

    PubMed

    Lipfert, Jan; Hao, Xiaomin; Dekker, Nynke H

    2009-06-17

    Magnetic tweezers are a powerful tool to manipulate single DNA or RNA molecules and to study nucleic acid-protein interactions in real time. Here, we have modeled the magnetic fields of permanent magnets in magnetic tweezers and computed the forces exerted on superparamagnetic beads from first principles. For simple, symmetric geometries the magnetic fields can be calculated semianalytically using the Biot-Savart law. For complicated geometries and in the presence of an iron yoke, we employ a finite-element three-dimensional PDE solver to numerically solve the magnetostatic problem. The theoretical predictions are in quantitative agreement with direct Hall-probe measurements of the magnetic field and with measurements of the force exerted on DNA-tethered beads. Using these predictive theories, we systematically explore the effects of magnet alignment, magnet spacing, magnet size, and of adding an iron yoke to the magnets on the forces that can be exerted on tethered particles. We find that the optimal configuration for maximal stretching forces is a vertically aligned pair of magnets, with a minimal gap between the magnets and minimal flow cell thickness. Following these principles, we present a configuration that allows one to apply > or = 40 pN stretching forces on approximately 1-microm tethered beads. PMID:19527664

  19. A compact holographic optical tweezers instrument

    NASA Astrophysics Data System (ADS)

    Gibson, G. M.; Bowman, R. W.; Linnenberger, A.; Dienerowitz, M.; Phillips, D. B.; Carberry, D. M.; Miles, M. J.; Padgett, M. J.

    2012-11-01

    Holographic optical tweezers have found many applications including the construction of complex micron-scale 3D structures and the control of tools and probes for position, force, and viscosity measurement. We have developed a compact, stable, holographic optical tweezers instrument which can be easily transported and is compatible with a wide range of microscopy techniques, making it a valuable tool for collaborative research. The instrument measures approximately 30×30×35 cm and is designed around a custom inverted microscope, incorporating a fibre laser operating at 1070 nm. We designed the control software to be easily accessible for the non-specialist, and have further improved its ease of use with a multi-touch iPad interface. A high-speed camera allows multiple trapped objects to be tracked simultaneously. We demonstrate that the compact instrument is stable to 0.5 nm for a 10 s measurement time by plotting the Allan variance of the measured position of a trapped 2 μm silica bead. We also present a range of objects that have been successfully manipulated.

  20. Investigating the potential applications of a Raman tweezer system

    NASA Astrophysics Data System (ADS)

    Wray, John Casey

    This thesis describes the construction of an Optical Tweezer apparatus to be used in conjunction with a confocal Raman spectrometer. The tweezer utilizes an infrared (e=1064 nm) laser directed into an inverted microscope with NA=1.4 oil immersion 100x objective lens that strongly focuses the laser light into a sample to function as a single-beam gradient force trap. The long term goal of this research program is to develop a single molecule Raman tweezers apparatus that allows one to control the position of a Raman nanoplasmonic amplifier. This thesis describes the construction of the Raman tweezer apparatus along with several Raman spectra obtained from optically trapped samples of polystyrene fluorescent orange, amine-modified latex beads. In addition, I explored the Raman spectra of bulk cytochrome c mixed with or injected onto Ag aggregates for SERs enhancement.

  1. Optical tweezers for studying taxis in parasites

    NASA Astrophysics Data System (ADS)

    de Thomaz, A. A.; Fontes, A.; Stahl, C. V.; Pozzo, L. Y.; Ayres, D. C.; Almeida, D. B.; Farias, P. M. A.; Santos, B. S.; Santos-Mallet, J.; Gomes, S. A. O.; Giorgio, S.; Feder, D.; Cesar, C. L.

    2011-04-01

    In this work we present a methodology to measure force strengths and directions of living parasites with an optical tweezers setup. These measurements were used to study the parasites chemotaxis in real time. We observed behavior and measured the force of: (i) Leishmania amazonensis in the presence of two glucose gradients; (ii) Trypanosoma cruzi in the vicinity of the digestive system walls, and (iii) Trypanosoma rangeli in the vicinity of salivary glands as a function of distance. Our results clearly show a chemotactic behavior in every case. This methodology can be used to study any type of taxis, such as chemotaxis, osmotaxis, thermotaxis, phototaxis, of any kind of living microorganisms. These studies can help us to understand the microorganism sensory systems and their response function to these gradients.

  2. Eukaryotic membrane tethers revisited using magnetic tweezers

    NASA Astrophysics Data System (ADS)

    Hosu, Basarab G.; Sun, Mingzhai; Marga, Françoise; Grandbois, Michel; Forgacs, Gabor

    2007-06-01

    Membrane nanotubes, under physiological conditions, typically form en masse. We employed magnetic tweezers (MTW) to extract tethers from human brain tumor cells and compared their biophysical properties with tethers extracted after disruption of the cytoskeleton and from a strongly differing cell type, Chinese hamster ovary cells. In this method, the constant force produced with the MTW is transduced to cells through super-paramagnetic beads attached to the cell membrane. Multiple sudden jumps in bead velocity were manifest in the recorded bead displacement-time profiles. These discrete events were interpreted as successive ruptures of individual tethers. Observation with scanning electron microscopy supported the simultaneous existence of multiple tethers. The physical characteristics, in particular, the number and viscoelastic properties of the extracted tethers were determined from the analytic fit to bead trajectories, provided by a standard model of viscoelasticity. Comparison of tethers formed with MTW and atomic force microscopy (AFM), a technique where the cantilever-force transducer is moved at constant velocity, revealed significant differences in the two methods of tether formation. Our findings imply that extreme care must be used to interpret the outcome of tether pulling experiments performed with single molecular techniques (MTW, AFM, optical tweezers, etc). First, the different methods may be testing distinct membrane structures with distinct properties. Second, as soon as a true cell membrane (as opposed to that of a vesicle) can attach to a substrate, upon pulling on it, multiple nonspecific membrane tethers may be generated. Therefore, under physiological conditions, distinguishing between tethers formed through specific and nonspecific interactions is highly nontrivial if at all possible.

  3. Eukaryotic membrane tethers revisited using magnetic tweezers.

    PubMed

    Hosu, Basarab G; Sun, Mingzhai; Marga, Françoise; Grandbois, Michel; Forgacs, Gabor

    2007-04-19

    Membrane nanotubes, under physiological conditions, typically form en masse. We employed magnetic tweezers (MTW) to extract tethers from human brain tumor cells and compared their biophysical properties with tethers extracted after disruption of the cytoskeleton and from a strongly differing cell type, Chinese hamster ovary cells. In this method, the constant force produced with the MTW is transduced to cells through super-paramagnetic beads attached to the cell membrane. Multiple sudden jumps in bead velocity were manifest in the recorded bead displacement-time profiles. These discrete events were interpreted as successive ruptures of individual tethers. Observation with scanning electron microscopy supported the simultaneous existence of multiple tethers. The physical characteristics, in particular, the number and viscoelastic properties of the extracted tethers were determined from the analytic fit to bead trajectories, provided by a standard model of viscoelasticity. Comparison of tethers formed with MTW and atomic force microscopy (AFM), a technique where the cantilever-force transducer is moved at constant velocity, revealed significant differences in the two methods of tether formation. Our findings imply that extreme care must be used to interpret the outcome of tether pulling experiments performed with single molecular techniques (MTW, AFM, optical tweezers, etc). First, the different methods may be testing distinct membrane structures with distinct properties. Second, as soon as a true cell membrane (as opposed to that of a vesicle) can attach to a substrate, upon pulling on it, multiple nonspecific membrane tethers may be generated. Therefore, under physiological conditions, distinguishing between tethers formed through specific and nonspecific interactions is highly nontrivial if at all possible.

  4. Optical manipulation of lipid and polymer nanotubes with optical tweezers

    NASA Astrophysics Data System (ADS)

    Reiner, Joseph E.; Kishore, Rani; Pfefferkorn, Candace; Wells, Jeffrey; Helmerson, Kristian; Howell, Peter; Vreeland, Wyatt; Forry, Samuel; Locascio, Laurie; Reyes-Hernandez, Darwin; Gaitan, Michael

    2004-10-01

    Using optical tweezers and microfluidics, we stretch either the lipid or polymer membranes of liposomes or polymersomes, respectively, into long nanotubes. The membranes can be grabbed directly with the optical tweezers to produce sub-micron diameter tubes that are several hundred microns in length. We can stretch tubes up to a centimeter in length, limited only by the travel of our microscope stage. We also demonstrate the cross linking of a pulled polymer nanotube.

  5. Laser tweezers Raman spectroscopy of single cells

    NASA Astrophysics Data System (ADS)

    Chen, De

    Raman scattering is an inelastic collision between the vibrating molecules inside the sample and the incident photons. During this process, energy exchange takes place between the photon and the scattering molecule. By measuring the energy change of the photon, the molecular vibration mode can be probed. The vibrational spectrum contains valuable information about the disposition of atomic nuclei and chemical bonds within a molecule, the chemical compositions and the interactions between the molecule and its surroundings. In this dissertation, laser tweezers Raman spectroscopy (LTRS) technique is applied for the analysis of biological cells and human cells at single cell level. In LTRS, an individual cell is trapped in aqueous medium with laser tweezers, and Raman scattering spectra from the trapped cell are recorded in real-time. The Raman spectra of these cells can be used to reveal the dynamical processes of cell growth, cell response to environment changes, and can be used as the finger print for the identification of a bacterial cell species. Several biophysical experiments were carried out using LTRS: (1) the dynamic germination process of individual spores of Bacillus thuringiensis was detected via Ca-DPA, a spore-specific biomarker molecule; (2) inactivation and killing of Bacillus subtilis spores by microwave irradiation and wet heat were studied at single cell level; (3) the heat shock activation process of single B. subtilis spores were analyzed, in which the reversible transition from glass-like state at low temperature to liquid-like state at high temperature in spore was revealed at the molecular level; (4) the kinetic processes of bacterial cell lysis of E. coli by lysozyme and by temperature induction of lambda phage were detected real-time; (5) the fixation and rehydration of human platelets were quantitatively evaluated and characterized with Raman spectroscopy method, which provided a rapid way to quantify the quality of freeze-dried therapeutic

  6. Characterization of periodic cavitation in optical tweezers.

    PubMed

    Carmona-Sosa, Viridiana; Alba-Arroyo, José Ernesto; Quinto-Su, Pedro A

    2016-03-10

    Microscopic vapor explosions or cavitation bubbles can be generated repeatedly in optical tweezers with a microparticle that partially absorbs at the trapping laser wavelength. In this work we measure the size distribution and the production rate of cavitation bubbles for microparticles with a diameter of 3 μm using high-speed video recording and a fast photodiode. We find that there is a lower bound for the maximum bubble radius R(max)∼2  μm which can be explained in terms of the microparticle size. More than 94% of the measured R(max) are in the range between 2 and 6 μm, while the same percentage of the measured individual frequencies f(i) or production rates are between 10 and 200 Hz. The photodiode signal yields an upper bound for the lifetime of the bubbles, which is at most twice the value predicted by the Rayleigh equation. We also report empirical relations between R(max), f(i), and the bubble lifetimes. PMID:26974779

  7. Constructing Dual Beam Optical Tweezers for Undergraduate Biophysics Research

    NASA Astrophysics Data System (ADS)

    Daudelin, Brian; West-Coates, Devon; Del'Etoile, Jon; Grotzke, Eric; Paramanathan, Thayaparan

    Optical tweezing, or trapping, is a modern physics technique which allows us to use the radiation pressure from laser beams to trap micron sized particles. Optical tweezers are commonly used in graduate level biophysics research but seldom used at the undergraduate level. Our goal is to construct a dual beam optical tweezers for future undergraduate biophysical research. Dual beam optical tweezers use two counter propagating laser beams to provide a stronger trap. In this study we discuss how the assembly of the dual beam optical tweezers is done through three main phases. The first phase was to construct a custom compressed air system to isolate the optical table from the vibrations from its surroundings so that we can measure pico-newton scale forces that are observed in biological systems. In addition, the biomaterial flow system was designed with a flow cell to trap biomolecules by combining several undergraduate semester projects. During the second phase we set up the optics to image and display the inside of the flow cell. Currently we are in the process of aligning the laser to create an effective trap and developing the software to control the data collection. This optical tweezers set up will enable us to study potential cancer drug interactions with DNA at the single molecule level and will be a powerful tool in promoting interdisciplinary research at the undergraduate level.

  8. How safe is gamete micromanipulation by laser tweezers?

    NASA Astrophysics Data System (ADS)

    Koenig, Karsten; Tromberg, Bruce J.; Tadir, Yona; Berns, Michael W.

    1998-04-01

    Laser tweezers, used as novel sterile micromanipulation tools of living cells, are employed in laser-assisted in vitro fertilization (IVF). For example, controlled spermatozoa transport with 1064 nm tweezers to human egg cells has been performed in European clinics in cases of male infertility. The interaction of approximately 100 mW near infrared (NIR) trapping beams at MW/cm2 intensity with human gametes results in low mean less than 2 K temperature increases and less than 100 pN trapping forces. Therefore, photothermal or photomechanical induced destructive effects appear unlikely. However, the high photon flux densities may induce simultaneous absorption of two NIR photons resulting in nonlinear interactions. These nonlinear interactions imply non-resonant two-photon excitation of endogenous cellular chromophores. In the case of less than 800 nm tweezers, UV- like damage effects may occur. The destructive effect is amplified when multimode cw lasers are used as tweezer sources due to longitudinal mode-beating effects and partial mode- locking. Spermatozoa damage within seconds using 760 nm traps due to formation of unstable ps pulses in a cw Ti:Sa ring laser is demonstrated. We recommend the use of greater than or equal to 800 nm traps for optical gamete micromanipulation. To our opinion, further basic studies on the influence of nonlinear effects of laser tweezers on human gamete are necessary.

  9. Graded-index optical fiber tweezers with long manipulation length.

    PubMed

    Gong, Yuan; Huang, Wei; Liu, Qun-Feng; Wu, Yu; Rao, Yunjiang; Peng, Gang-Ding; Lang, Jinyi; Zhang, Ke

    2014-10-20

    Long manipulation length is critical for optical fiber tweezers to enhance the flexibility of non-contact trapping. In this paper a long manipulation distance of more than 40 μm is demonstrated experimentally by the graded-index fiber (GIF) tweezers, which is fabricated by chemically etching a GIF taper with a large cone angle of 58°. The long manipulation distance is obtained by introducing an air cavity between the lead-in single mode fiber and the GIF as well as by adjusting the laser power in the existence of a constant background flow. The influence of the cavity length and the GIF length on the light distribution and the focusing length of the GIF taper is investigated numerically, which is helpful for optimizing the parameters to perform stable optical trapping. This kind of optical fiber tweezers has advantages including low-cost, easy-to-fabricate and easy-to-use. PMID:25401560

  10. Optical tweezers force measurements to study parasites chemotaxis

    NASA Astrophysics Data System (ADS)

    de Thomaz, A. A.; Pozzo, L. Y.; Fontes, A.; Almeida, D. B.; Stahl, C. V.; Santos-Mallet, J. R.; Gomes, S. A. O.; Feder, D.; Ayres, D. C.; Giorgio, S.; Cesar, C. L.

    2009-07-01

    In this work, we propose a methodology to study microorganisms chemotaxis in real time using an Optical Tweezers system. Optical Tweezers allowed real time measurements of the force vectors, strength and direction, of living parasites under chemical or other kinds of gradients. This seems to be the ideal tool to perform observations of taxis response of cells and microorganisms with high sensitivity to capture instantaneous responses to a given stimulus. Forces involved in the movement of unicellular parasites are very small, in the femto-pico-Newton range, about the same order of magnitude of the forces generated in an Optical Tweezers. We applied this methodology to investigate the Leishmania amazonensis (L. amazonensis) and Trypanossoma cruzi (T. cruzi) under distinct situations.

  11. Optical tweezers reveal how proteins alter replication

    NASA Astrophysics Data System (ADS)

    Chaurasiya, Kathy

    Single molecule force spectroscopy is a powerful method that explores the DNA interaction properties of proteins involved in a wide range of fundamental biological processes such as DNA replication, transcription, and repair. We use optical tweezers to capture and stretch a single DNA molecule in the presence of proteins that bind DNA and alter its mechanical properties. We quantitatively characterize the DNA binding mechanisms of proteins in order to provide a detailed understanding of their function. In this work, we focus on proteins involved in replication of Escherichia coli (E. coli ), endogenous eukaryotic retrotransposons Ty3 and LINE-1, and human immunodeficiency virus (HIV). DNA polymerases replicate the entire genome of the cell, and bind both double-stranded DNA (dsDNA) and single-stranded DNA (ssDNA) during DNA replication. The replicative DNA polymerase in the widely-studied model system E. coli is the DNA polymerase III subunit alpha (DNA pol III alpha). We use optical tweezers to determine that UmuD, a protein that regulates bacterial mutagenesis through its interactions with DNA polymerases, specifically disrupts alpha binding to ssDNA. This suggests that UmuD removes alpha from its ssDNA template to allow DNA repair proteins access to the damaged DNA, and to facilitate exchange of the replicative polymerase for an error-prone translesion synthesis (TLS) polymerase that inserts nucleotides opposite the lesions, so that bacterial DNA replication may proceed. This work demonstrates a biophysical mechanism by which E. coli cells tolerate DNA damage. Retroviruses and retrotransposons reproduce by copying their RNA genome into the nuclear DNA of their eukaryotic hosts. Retroelements encode proteins called nucleic acid chaperones, which rearrange nucleic acid secondary structure and are therefore required for successful replication. The chaperone activity of these proteins requires strong binding affinity for both single- and double-stranded nucleic

  12. Tunable optical tweezers for wavelength-dependent measurements

    PubMed Central

    Hester, Brooke; Campbell, Gretchen K.; López-Mariscal, Carlos; Filgueira, Carly Levin; Huschka, Ryan; Halas, Naomi J.; Helmerson, Kristian

    2012-01-01

    Optical trapping forces depend on the difference between the trap wavelength and the extinction resonances of trapped particles. This leads to a wavelength-dependent trapping force, which should allow for the optimization of optical tweezers systems, simply by choosing the best trapping wavelength for a given application. Here we present an optical tweezer system with wavelength tunability, for the study of resonance effects. With this system, the optical trap stiffness is measured for single trapped particles that exhibit either single or multiple extinction resonances. We include discussions of wavelength-dependent effects, such as changes in temperature, and how to measure them. PMID:22559522

  13. Using laser tweezers to measure twitching motility in Neisseria.

    PubMed

    Maier, Berenike

    2005-06-01

    Dynamic properties of type IV pili are essential for their function in bacterial infection, twitching motility and gene transfer. Laser tweezers are versatile tools to study the molecular mechanism underlying pilus dynamics at the single molecule level. Recently, these optical tweezers have been used to monitor pilus elongation and retraction in vivo at a resolution of several nanometers. The force generated by type IV pili exceeds 100 pN making pili the strongest linear motors characterized to date. The study of pilus dynamics at the single molecule level sheds light on kinetics, force generation, switching and mechanics of the Neisseria gonorrhoeae pilus motor. PMID:15939360

  14. Marker-free cell discrimination by holographic optical tweezers

    NASA Astrophysics Data System (ADS)

    Schaal, F.; Warber, M.; Zwick, S.; van der Kuip, H.; Haist, T.; Osten, W.

    2009-06-01

    We introduce a method for marker-free cell discrimination based on optical tweezers. Cancerous, non-cancerous, and drug-treated cells could be distinguished by measuring the trapping forces using holographic optical tweezers. We present trapping force measurements on different cell lines: normal pre-B lymphocyte cells (BaF3; "normal cells"), their Bcr-Abl transformed counterparts (BaF3-p185; "cancer cells") as a model for chronic myeloid leukaemia (CML) and Imatinib treated BaF3-p185 cells. The results are compared with reference measurements obtained by a commercial flow cytometry system.

  15. Magnetic tweezers for manipulation of magnetic particles in single cells

    NASA Astrophysics Data System (ADS)

    Ebrahimian, H.; Giesguth, M.; Dietz, K.-J.; Reiss, G.; Herth, S.

    2014-02-01

    Magnetic tweezers gain increasing interest for applications in biology. Here, a setup of magnetic tweezers is introduced using micropatterned conducting lines on transparent glass slides. Magnetic particles of 1 μm diameter were injected in barley cell vacuoles using a microinject system under microscopic control. Time dependent tracking of the particles after application of a magnetic field was used to determine the viscosity of vacuolar sap in vivo relative to water and isolated vacuolar fluid. The viscosity of vacuolar sap in cells was about 2-fold higher than that of extracted vacuolar fluid and 5 times higher than that of water.

  16. Airy acoustical-sheet spinner tweezers

    NASA Astrophysics Data System (ADS)

    Mitri, F. G.

    2016-09-01

    The Airy acoustical beam exhibits parabolic propagation and spatial acceleration, meaning that the propagation bending angle continuously increases before the beam trajectory reaches a critical angle where it decays after a propagation distance, without applying any external bending force. As such, it is of particular importance to investigate its properties from the standpoint of acoustical radiation force, spin torque, and particle dynamics theories, in the development of novel particle sorting techniques and acoustically mediated clearing systems. This work investigates these effects on a two-dimensional (2D) circular absorptive structure placed in the field of a nonparaxial Airy "acoustical-sheet" (i.e., finite beam in 2D), for potential applications in surface acoustic waves and acousto-fluidics. Based on the characteristics of the acoustic field, the beam is capable of manipulating the circular cylindrical fluid cross-section and guides it along a transverse or parabolic trajectory. This feature of Airy acoustical beams could lead to a unique characteristic in single-beam acoustical tweezers related to acoustical sieving, filtering, and removal of particles and cells from a section of a small channel. The analysis developed here is based on the description of the nonparaxial Airy beam using the angular spectrum decomposition of plane waves in close association with the partial-wave series expansion method in cylindrical coordinates. The numerical results demonstrate the ability of the nonparaxial Airy acoustical-sheet beam to pull, propel, or accelerate a particle along a parabolic trajectory, in addition to particle confinement in the transverse direction of wave propagation. Negative or positive radiation force and spin torque causing rotation in the clockwise or the anticlockwise direction can occur depending on the nondimensional parameter ka (where k is the wavenumber and a is the radius) and the location of the cylinder in the beam. Applications in

  17. Assembling silver nanowires using optoelectronic tweezers

    NASA Astrophysics Data System (ADS)

    Zhang, Shuailong; Cooper, Jonathan M.; Neale, Steve L.

    2016-03-01

    Light patterned dielectrophoresis or optoelectronic tweezers (OET) has been proved to be an effective micromanipulation technology for cell separation, cell sorting and control of cell interactions. Apart from being useful for cell biology experiments, the capability of moving small objects accurately also makes OET an attractive technology for other micromanipulation applications. In particular, OET has the potential to be used for efficiently and accurately assembling small optoelectronic/electronic components into circuits. This approach could produce a step change in the size of the smallest components that are routinely assembled; down from the current smallest standard component size of 400×200 μm (0402 metric) to components a few microns across and even nanostructured components. In this work, we have demonstrated the use of OET to manipulate conductive silver nanowires into different patterns. The silver nanowires (typical diameter: 60 nm; typical length: 10 μm) were suspended in a 15 mS/m solution of KCL in water and manipulated by positive dielectrophoresis force generated by OET. A proof-of-concept demonstration was also made to prove the feasibility of using OET to manipulate silver nanowires to form a 150-μm-long conductive path between two isolated electrodes. It can be seen that the resistance between two electrodes was effectively brought down to around 700 Ω after the silver nanowires were assembled and the solution evaporated. Future work in this area will focus on increasing the conductivity of these tracks, encapsulating the assembled silver nanowires to prevent silver oxidation and provide mechanical protection, which can be achieved via 3D printing and inkjet printing technology.

  18. Plasmon enhanced optical tweezers with gold-coated black silicon

    PubMed Central

    Kotsifaki, D. G.; Kandyla, M.; Lagoudakis, P. G.

    2016-01-01

    Plasmonic optical tweezers are a ubiquitous tool for the precise manipulation of nanoparticles and biomolecules at low photon flux, while femtosecond-laser optical tweezers can probe the nonlinear optical properties of the trapped species with applications in biological diagnostics. In order to adopt plasmonic optical tweezers in real-world applications, it is essential to develop large-scale fabrication processes without compromising the trapping efficiency. Here, we develop a novel platform for continuous wave (CW) and femtosecond plasmonic optical tweezers, based on gold-coated black silicon. In contrast with traditional lithographic methods, the fabrication method relies on simple, single-step, maskless tabletop laser processing of silicon in water that facilitates scalability. Gold-coated black silicon supports repeatable trapping efficiencies comparable to the highest ones reported to date. From a more fundamental aspect, a plasmon-mediated efficiency enhancement is a resonant effect, and therefore, dependent on the wavelength of the trapping beam. Surprisingly, a wavelength characterization of plasmon-enhanced trapping efficiencies has evaded the literature. Here, we exploit the repeatability of the recorded trapping efficiency, offered by the gold-coated black silicon platform, and perform a wavelength-dependent characterization of the trapping process, revealing the resonant character of the trapping efficiency maxima. Gold-coated black silicon is a promising platform for large-scale parallel trapping applications that will broaden the range of optical manipulation in nanoengineering, biology, and the study of collective biophotonic effects. PMID:27195446

  19. Spin dynamics and Kondo physics in optical tweezers

    NASA Astrophysics Data System (ADS)

    Lin, Yiheng; Lester, Brian J.; Brown, Mark O.; Kaufman, Adam M.; Long, Junling; Ball, Randall J.; Isaev, Leonid; Wall, Michael L.; Rey, Ana Maria; Regal, Cindy A.

    2016-05-01

    We propose to use optical tweezers as a toolset for direct observation of the interplay between quantum statistics, kinetic energy and interactions, and thus implement minimum instances of the Kondo lattice model in systems with few bosonic rubidium atoms. By taking advantage of strong local exchange interactions, our ability to tune the spin-dependent potential shifts between the two wells and complete control over spin and motional degrees of freedom, we design an adiabatic tunneling scheme that efficiently creates a spin-singlet state in one well starting from two initially separated atoms (one atom per tweezer) in opposite spin state. For three atoms in a double-well, two localized in the lowest vibrational mode of each tweezer and one atom in an excited delocalized state, we plan to use similar techniques and observe resonant transfer of two-atom singlet-triplet states between the wells in the regime when the exchange coupling exceeds the mobile atom hopping. Moreover, we argue that such three-atom double-tweezers could potentially be used for quantum computation by encoding logical qubits in collective spin and motional degrees of freedom. Current address: Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA.

  20. Unraveling chromatin structure using magnetic tweezers

    NASA Astrophysics Data System (ADS)

    van Noort, John

    2010-03-01

    The compact, yet dynamic organization of chromatin plays an essential role in regulating gene expression. Although the static structure of chromatin fibers has been studied extensively, the controversy about the higher order folding remains. The compaction of eukaryotic DNA into chromatin has been implicated in the regulation of all DNA processes. To understand the relation between gene regulation and chromatin structure it is essential to uncover the mechanisms by which chromatin fibers fold and unfold. We used magnetic tweezers to probe the mechanical properties of individual nucleosomes and chromatin fibers consisting of a single, well-defined array of 25 nucleosomes. From these studies five major features appeared upon forced extension of chromatin fibers: the elastic stretching of chromatin's higher order structure, the breaking of internucleosomal contacts, unwrapping of the first turn of DNA, unwrapping of the second turn of DNA, and the dissociation of histone octamers. These events occur sequentially at the increasing force. Neighboring nucleosomes stabilize DNA folding into a nucleosome relative to isolated nucleosomes. When an array of nucleosomes is folded into a 30 nm fiber, representing the first level of chromatin condensation, the fiber stretched like a Hookian spring at forces up to 4 pN. Together with a nucleosome-nucleosome stacking energy of 14 kT this points to a solenoid as the underlying topology of the 30 nm fiber. Surprisingly, linker histones do not affect the length or stiffness of the fibers, but stabilize fiber folding up to forces of 7 pN. The stiffness of the folded chromatin fiber points at histone tails that mediate nucleosome stacking. Fibers with a nucleosome repeat length of 167 bp instead of 197 bp are significantly stiffer, consistent with a two-start helical arrangement. The extensive thermal breathing of the chromatin fiber that is a consequence of the observed high compliance provides a structural basis for understanding the

  1. Single-sided lateral-field and phototransistor-based optoelectronic tweezers

    NASA Technical Reports Server (NTRS)

    Ohta, Aaron (Inventor); Chiou, Pei-Yu (Inventor); Hsu, Hsan-Yin (Inventor); Jamshidi, Arash (Inventor); Wu, Ming-Chiang (Inventor); Neale, Steven L. (Inventor)

    2011-01-01

    Described herein are single-sided lateral-field optoelectronic tweezers (LOET) devices which use photosensitive electrode arrays to create optically-induced dielectrophoretic forces in an electric field that is parallel to the plane of the device. In addition, phototransistor-based optoelectronic tweezers (PhOET) devices are described that allow for optoelectronic tweezers (OET) operation in high-conductivity physiological buffer and cell culture media.

  2. A microscopic steam engine implemented in an optical tweezer.

    PubMed

    Quinto-Su, Pedro A

    2014-01-01

    The introduction of improved steam engines at the end of the 18th century marked the start of the industrial revolution and the birth of classical thermodynamics. Currently, there is great interest in miniaturizing heat engines, but so far traditional heat engines operating with the expansion and compression of gas have not reached length scales shorter than one millimeter. Here, a micrometer-sized piston steam engine is implemented in an optical tweezer. The piston is a single colloidal microparticle that is driven by explosive vapourization of the surrounding liquid (cavitation bubbles) and by optical forces at a rate between a few tens of Hertz and one kilo-Hertz. The operation of the engine allows to exert impulsive forces with optical tweezers and induce streaming in the liquid, similar to the effect of transducers when driven at acoustic and ultrasound frequencies. PMID:25523395

  3. A microscopic steam engine implemented in an optical tweezer.

    PubMed

    Quinto-Su, Pedro A

    2014-12-19

    The introduction of improved steam engines at the end of the 18th century marked the start of the industrial revolution and the birth of classical thermodynamics. Currently, there is great interest in miniaturizing heat engines, but so far traditional heat engines operating with the expansion and compression of gas have not reached length scales shorter than one millimeter. Here, a micrometer-sized piston steam engine is implemented in an optical tweezer. The piston is a single colloidal microparticle that is driven by explosive vapourization of the surrounding liquid (cavitation bubbles) and by optical forces at a rate between a few tens of Hertz and one kilo-Hertz. The operation of the engine allows to exert impulsive forces with optical tweezers and induce streaming in the liquid, similar to the effect of transducers when driven at acoustic and ultrasound frequencies.

  4. A microscopic steam engine implemented in an optical tweezer

    NASA Astrophysics Data System (ADS)

    Quinto-Su, Pedro A.

    2014-12-01

    The introduction of improved steam engines at the end of the 18th century marked the start of the industrial revolution and the birth of classical thermodynamics. Currently, there is great interest in miniaturizing heat engines, but so far traditional heat engines operating with the expansion and compression of gas have not reached length scales shorter than one millimeter. Here, a micrometer-sized piston steam engine is implemented in an optical tweezer. The piston is a single colloidal microparticle that is driven by explosive vapourization of the surrounding liquid (cavitation bubbles) and by optical forces at a rate between a few tens of Hertz and one kilo-Hertz. The operation of the engine allows to exert impulsive forces with optical tweezers and induce streaming in the liquid, similar to the effect of transducers when driven at acoustic and ultrasound frequencies.

  5. Mechanical force characterization in manipulating live cells with optical tweezers.

    PubMed

    Wu, Yanhua; Sun, Dong; Huang, Wenhao

    2011-02-24

    Laser trapping with optical tweezers is a noninvasive manipulation technique and has received increasing attentions in biological applications. Understanding forces exerted on live cells is essential to cell biomechanical characterizations. Traditional numerical or experimental force measurement assumes live cells as ideal objects, ignoring their complicated inner structures and rough membranes. In this paper, we propose a new experimental method to calibrate the trapping and drag forces acted on live cells. Binding a micro polystyrene sphere to a live cell and moving the mixture with optical tweezers, we can obtain the drag force on the cell by subtracting the drag force on the sphere from the total drag force on the mixture, under the condition of extremely low Reynolds number. The trapping force on the cell is then obtained from the drag force when the cell is in force equilibrium state. Experiments on numerous live cells demonstrate the effectiveness of the proposed force calibration approach.

  6. Cluster formation in ferrofluids induced by holographic optical tweezers.

    PubMed

    Masajada, Jan; Bacia, Marcin; Drobczyński, Sławomir

    2013-10-01

    Holographic optical tweezers were used to show the interaction between a strongly focused laser beam and magnetic nanoparticles in ferrofluid. When the light intensity was high enough, magnetic nanoparticles were removed from the beam center and formed a dark ring. The same behavior was observed when focusing vortex or Bessel beams. The interactions between two or more separated rings of magnetic nanoparticles created by independent optical traps were also observed. PMID:24081086

  7. Electromagnetic tweezers with independent force and torque control

    NASA Astrophysics Data System (ADS)

    Jiang, Chang; Lionberger, Troy A.; Wiener, Diane M.; Meyhofer, Edgar

    2016-08-01

    Magnetic tweezers are powerful tools to manipulate and study the mechanical properties of biological molecules and living cells. In this paper we present a novel, bona fide electromagnetic tweezer (EMT) setup that allows independent control of the force and torque applied via micrometer-sized magnetic beads to a molecule under study. We implemented this EMT by combining a single solenoid that generates force (f-EMT) with a set of four solenoids arranged into a symmetric quadrupole to generate torque (τ-EMT). To demonstrate the capability of the tweezers, we attached optically asymmetric Janus beads to single, tethered DNA molecules. We show that tension in the piconewton force range can be applied to single DNA molecules and the molecule can simultaneously be twisted with torques in the piconewton-nanometer range. Furthermore, the EMT allows the two components to be independently controlled. At various force levels applied to the Janus bead, the trap torsional stiffness can be continuously changed simply by varying the current magnitude applied to the τ-EMT. The flexible and independent control of force and torque by the EMT makes it an ideal tool for a range of measurements where tensional and torsional properties need to be studied simultaneously on a molecular or cellular level.

  8. Optical tweezers theory near a flat surface: a perturbative method

    NASA Astrophysics Data System (ADS)

    Flyvbjerg, Henrik; Dutra, Rafael S.; Maia Neto, Paolo A.; Nussenzveig, H. Moyses

    We propose a perturbative calculation of the optical force exercised by a focused laser beam on a microsphere of arbitrary radius that is localized near a flat glass surface in a standard optical tweezers setup. Starting from the Mie-Debye representation for the electric field of a Gaussian laser beam, focused by an objective of high numerical aperture, we derive a recursive series that represents the multiple reflections that describe the reverberation of laser light between the microsphere and the glass slide. We present numerical results for the axial component of the optical force and the axial trap stiffness. Numerical results for a configuration typical in biological applications--a microsphere of 0.5 µm radius at a distance around 0.25 µm from the surface--show a 37 [1] Viana N B, Rocha M S. Mesquita O N, et al. (2007) Towards absolute calibration of optical tweezers. Phys Rev E 75:021914-1-14. [2] Dutra R S, Viana N B, Maia Neto P A, et al. (2014) Absolute calibration of forces in optical tweezers. Phys Rev A 90:013825-1-13. Rafael S. Dutra thanks the Brazilian ``Science without Borders'' program for a postdoctoral scholarship.

  9. Electromagnetic tweezers with independent force and torque control.

    PubMed

    Jiang, Chang; Lionberger, Troy A; Wiener, Diane M; Meyhofer, Edgar

    2016-08-01

    Magnetic tweezers are powerful tools to manipulate and study the mechanical properties of biological molecules and living cells. In this paper we present a novel, bona fide electromagnetic tweezer (EMT) setup that allows independent control of the force and torque applied via micrometer-sized magnetic beads to a molecule under study. We implemented this EMT by combining a single solenoid that generates force (f-EMT) with a set of four solenoids arranged into a symmetric quadrupole to generate torque (τ-EMT). To demonstrate the capability of the tweezers, we attached optically asymmetric Janus beads to single, tethered DNA molecules. We show that tension in the piconewton force range can be applied to single DNA molecules and the molecule can simultaneously be twisted with torques in the piconewton-nanometer range. Furthermore, the EMT allows the two components to be independently controlled. At various force levels applied to the Janus bead, the trap torsional stiffness can be continuously changed simply by varying the current magnitude applied to the τ-EMT. The flexible and independent control of force and torque by the EMT makes it an ideal tool for a range of measurements where tensional and torsional properties need to be studied simultaneously on a molecular or cellular level. PMID:27587135

  10. Magnetic Forces and DNA Mechanics in Multiplexed Magnetic Tweezers

    PubMed Central

    van Loenhout, Marijn T. J.; Burnham, Daniel R.; Dekker, Cees

    2012-01-01

    Magnetic tweezers (MT) are a powerful tool for the study of DNA-enzyme interactions. Both the magnet-based manipulation and the camera-based detection used in MT are well suited for multiplexed measurements. Here, we systematically address challenges related to scaling of multiplexed magnetic tweezers (MMT) towards high levels of parallelization where large numbers of molecules (say 103) are addressed in the same amount of time required by a single-molecule measurement. We apply offline analysis of recorded images and show that this approach provides a scalable solution for parallel tracking of the xyz-positions of many beads simultaneously. We employ a large field-of-view imaging system to address many DNA-bead tethers in parallel. We model the 3D magnetic field generated by the magnets and derive the magnetic force experienced by DNA-bead tethers across the large field of view from first principles. We furthermore experimentally demonstrate that a DNA-bead tether subject to a rotating magnetic field describes a bicircular, Limaçon rotation pattern and that an analysis of this pattern simultaneously yields information about the force angle and the position of attachment of the DNA on the bead. Finally, we apply MMT in the high-throughput investigation of the distribution of the induced magnetic moment, the position of attachment of DNA on the beads, and DNA flexibility. The methods described herein pave the way to kilo-molecule level magnetic tweezers experiments. PMID:22870220

  11. Magnetic tweezers: micromanipulation and force measurement at the molecular level.

    PubMed Central

    Gosse, Charlie; Croquette, Vincent

    2002-01-01

    Cantilevers and optical tweezers are widely used for micromanipulating cells or biomolecules for measuring their mechanical properties. However, they do not allow easy rotary motion and can sometimes damage the handled material. We present here a system of magnetic tweezers that overcomes those drawbacks while retaining most of the previous dynamometers properties. Electromagnets are coupled to a microscope-based particle tracking system through a digital feedback loop. Magnetic beads are first trapped in a potential well of stiffness approximately 10(-7) N/m. Thus, they can be manipulated in three dimensions at a speed of approximately 10 microm/s and rotated along the optical axis at a frequency of 10 Hz. In addition, our apparatus can work as a dynamometer relying on either usual calibration against the viscous drag or complete calibration using Brownian fluctuations. By stretching a DNA molecule between a magnetic particle and a glass surface, we applied and measured vertical forces ranging from 50 fN to 20 pN. Similarly, nearly horizontal forces up to 5 pN were obtained. From those experiments, we conclude that magnetic tweezers represent a low-cost and biocompatible setup that could become a suitable alternative to the other available micromanipulators. PMID:12023254

  12. Endohedral metallofullerenes: a unique host-guest association.

    PubMed

    Rodríguez-Fortea, Antonio; Balch, Alan L; Poblet, Josep M

    2011-07-01

    In this tutorial review taking X-ray crystallographically characterized compounds as a starting point a walk is taken through the electronic and structural properties of endohedral metallofullerenes. After classification of the fullerenes according to the encapsulated guest, particular attention is given to identifying factors that determine the selection of a particular carbon cage network by the internal metal cluster. Some of the physical rules that determine which particular fullerene cage is formed will be discussed. Concepts such as charge transfer between the cage and the guest metal ions, the topology of the cage, the separations between the 12 pentagons on the fullerene surface, and the effect of entropic factors are used to rationalize the selection of a particular cage. The roles of electrochemistry and vibrational spectroscopy in combination with theoretical calculations are considered in understanding the structures of the endohedral fullerenes.

  13. Host-guest supramolecular nanosystems for cancer diagnostics and therapeutics.

    PubMed

    Wang, Lei; Li, Li-li; Fan, Yun-shan; Wang, Hao

    2013-07-26

    Extensive efforts have been devoted to the construction of functional supramolecular nanosystems for applications in catalysis, energy conversion, sensing and biomedicine. The applications of supramolecular nanosystems such as liposomes, micelles, inorganic nanoparticles, carbon materials for cancer diagnostics and therapeutics have been reviewed by other groups. Here, we will focus on the recent momentous advances in the implementation of typical supramolecular hosts (i.e., cyclodextrins, calixarenes, cucurbiturils and metallo-hosts) and their nanosystems in cancer diagnostics and therapeutics. We discuss the evolutive process of supramolecular nanosystems from the structural control and characterization to their diagnostic and therapeutic function exploitation and even the future potentials for clinical translation.

  14. Photoresponsive vesicle permeability based on intramolecular host-guest inclusion.

    PubMed

    Kauscher, Ulrike; Samanta, Avik; Ravoo, Bart Jan

    2014-01-28

    This article describes light-responsive vesicles that can release their contents in response to a light-sensitive molecular trigger. To this end, liposomes were equipped with amphiphilic β-cyclodextrin that was covalently labeled with azobenzene. Using dye encapsulation and confocal laser scanning microscopy, we show that the permeability of these vesicles strongly increases upon UV irradiation (λ = 350 nm) with concomitant isomerization of apolar trans-azobenzene to polar cis-azobenzene on the liposome surface. PMID:24287588

  15. Reversible Guest Exchange Mechanisms in Supramolecular Host-GuestAssemblies

    SciTech Connect

    Pluth, Michael D.; Raymond, Kenneth N.

    2006-09-01

    Synthetic chemists have provided a wide array of supramolecular assemblies able to encapsulate guest molecules. The scope of this tutorial review focuses on supramolecular host molecules capable of reversibly encapsulating polyatomic guests. Much work has been done to determine the mechanism of guest encapsulation and guest release. This review covers common methods of monitoring and characterizing guest exchange such as NMR, UV-VIS, mass spectroscopy, electrochemistry, and calorimetry and also presents representative examples of guest exchange mechanisms. The guest exchange mechanisms of hemicarcerands, cucurbiturils, hydrogen-bonded assemblies, and metal-ligand assemblies are discussed. Special attention is given to systems which exhibit constrictive binding, a motif common in supramolecular guest exchange systems.

  16. Host-Guest Self-assembly in Block Copolymer Blends

    PubMed Central

    Park, Woon Ik; Kim, YongJoo; Jeong, Jae Won; Kim, Kyungho; Yoo, Jung-Keun; Hur, Yoon Hyung; Kim, Jong Min; Thomas, Edwin L.; Alexander-Katz, Alfredo; Jung, Yeon Sik

    2013-01-01

    Ultrafine, uniform nanostructures with excellent functionalities can be formed by self-assembly of block copolymer (BCP) thin films. However, extension of their geometric variability is not straightforward due to their limited thin film morphologies. Here, we report that unusual and spontaneous positioning between host and guest BCP microdomains, even in the absence of H-bond linkages, can create hybridized morphologies that cannot be formed from a neat BCP. Our self-consistent field theory (SCFT) simulation results theoretically support that the precise registration of a spherical BCP microdomain (guest, B-b-C) at the center of a perforated lamellar BCP nanostructure (host, A-b-B) can energetically stabilize the blended morphology. As an exemplary application of the hybrid nanotemplate, a nanoring-type Ge2Sb2Te5 (GST) phase-change memory device with an extremely low switching current is demonstrated. These results suggest the possibility of a new pathway to construct more diverse and complex nanostructures using controlled blending of various BCPs. PMID:24217036

  17. Interferometer-Controlled Optical Tweezers Constructed for Nanotechnology and Biotechnology

    NASA Technical Reports Server (NTRS)

    Decker, Arthur J.

    2002-01-01

    A new method to control microparticles was developed in-house at the NASA Glenn Research Center in support of the nanotechnology project under NASA's Aerospace Propulsion and Power Base Research Program. A prototype interferometer-controlled optical tweezers was constructed to manipulate scanning probe microscope (SPM) tips. A laser beam passed through a Mach-Zehnder interferometer, and a microscope objective then produced an optical trap from the coaxial beams. The trap levitated and generated the coarse motion of a 10-mm polystyrene sphere used to simulate a SPM tip. The interference between the beams provided fine control of the forces and moments on the sphere. The interferometer included a piezoelectric-scanned mirror to modulate the interference pattern. The 10-mm sphere was observed to oscillate about 1 mm as the mirror and fringe pattern oscillated. The prototype tweezers proved the feasibility of constructing a more sophisticated interferometer tweezers to hold and manipulate SPM tips. The SPM tips are intended to interrogate and manipulate nanostructures. A more powerful laser will be used to generate multiple traps to hold nanostructures and SPM tips. The vibrating mirror in the interferometer will be replaced with a spatial light modulator. The modulator will allow the optical phase distribution in one leg of the interferometer to be programmed independently at 640 by 480 points for detailed control of the forces and moments. The interference patterns will be monitored to measure the motion of the SPM tips. Neuralnetwork technology will provide fast analysis of the interference patterns for diagnostic purposes and for local or remote feedback control of the tips. This effort also requires theoretical and modeling support in the form of scattering calculations for twin coherent beams from nonspherical particles.

  18. A simple optical tweezers for trapping polystyrene particles

    NASA Astrophysics Data System (ADS)

    Shiddiq, Minarni; Nasir, Zulfa; Yogasari, Dwiyana

    2013-09-01

    Optical tweezers is an optical trap. For decades, it has become an optical tool that can trap and manipulate any particle from the very small size like DNA to the big one like bacteria. The trapping force comes from the radiation pressure of laser light which is focused to a group of particles. Optical tweezers has been used in many research areas such as atomic physics, medical physics, biophysics, and chemistry. Here, a simple optical tweezers has been constructed using a modified Leybold laboratory optical microscope. The ocular lens of the microscope has been removed for laser light and digital camera accesses. A laser light from a Coherent diode laser with wavelength λ = 830 nm and power 50 mW is sent through an immersion oil objective lens with magnification 100 × and NA 1.25 to a cell made from microscope slides containing polystyrene particles. Polystyrene particles with size 3 μm and 10 μm are used. A CMOS Thorlabs camera type DCC1545M with USB Interface and Thorlabs camera lens 35 mm are connected to a desktop and used to monitor the trapping and measure the stiffness of the trap. The camera is accompanied by camera software which makes able for the user to capture and save images. The images are analyzed using ImageJ and Scion macro. The polystyrene particles have been trapped successfully. The stiffness of the trap depends on the size of the particles and the power of the laser. The stiffness increases linearly with power and decreases as the particle size larger.

  19. Single molecule studies of helicases with magnetic tweezers.

    PubMed

    Hodeib, Samar; Raj, Saurabh; Manosas, M; Zhang, Weiting; Bagchi, Debjani; Ducos, Bertrand; Allemand, Jean-François; Bensimon, David; Croquette, Vincent

    2016-08-01

    Helicases are a broad family of enzymes that perform crucial functions in DNA replication and in the maintenance of DNA and RNA integrity. A detailed mechanical study of helicases on DNA and RNA is possible using single molecule manipulation methods. Among those, magnetic tweezers (or traps) present a convenient, moderate throughput assay (tens of enzymes can be monitored simultaneously) that allow for high resolution (single base-pair) studies of these enzymes in various conditions and on various substrates (double and single stranded DNA and RNA). Here we discuss various implementation of the basic assay relevant for these studies. PMID:27371121

  20. Single optical tweezers based on elliptical core fiber

    NASA Astrophysics Data System (ADS)

    Zhang, Yu; Zhao, Li; Chen, Yunhao; Liu, Zhihai; Zhang, Yaxun; Zhao, Enming; Yang, Jun; Yuan, Libo

    2016-04-01

    We propose and demonstrate a new single optical tweezers based on an elliptical core fiber, which can realize the trapped yeast cell rotation with a precise and simple control. Due to the elliptical shape of the fiber core, the LP11 mode beam can propagate stably. When we rotate the fiber tip, the LP11 mode beam will also rotate along with the fiber tip, which helps to realize the trapped micro-particle rotation. By using this method, we can easily realize the rotation of the trapped yeast cells, the rotating angle of the yeast cell is same as the elliptical core fiber tip.

  1. pH microprobe manipulated in microchannels using optical tweezers

    NASA Astrophysics Data System (ADS)

    Sinclair, Gavin S.; Klauke, Norbert; Monaghan, Paul; Padgett, Miles J.; Cooper, Jon

    2005-03-01

    SNARF-1 fluorochrome was used to functionalize 3μm diameter latex spheres making them sensitive to the pH of their environment, manifested as a change in their fluorescence. The fluorescence emission at 580nm was excited using a filtered xenon arc lamp at 515nm. A solution of functionalized latex spheres was placed between gold microelectrodes in a microfluidic channel. Optical tweezers were used to trap and manipulate the spheres in the vicinity of the microelectrodes, to map out the pH profile in the electrolyte solution, induced by passing 20 microsecond transient current pulses through the microelectrodes.

  2. Optical Tweezers for Sample Fixing in Micro-Diffraction Experiments

    SciTech Connect

    Amenitsch, H.; Rappolt, M.; Sartori, B.; Laggner, P.; Cojoc, D.; Ferrari, E.; Garbin, V.; Di Fabrizio, E.; Burghammer, M.; Riekel, Ch.

    2007-01-19

    In order to manipulate, characterize and measure the micro-diffraction of individual structural elements down to single phospholipid liposomes we have been using optical tweezers (OT) combined with an imaging microscope. We were able to install the OT system at the microfocus beamline ID13 at the ESRF and trap clusters of about 50 multi-lamellar liposomes (< 10 {mu}m large cluster). Further we have performed a scanning diffraction experiment with a 1 micrometer beam to demonstrate the fixing capabilities and to confirm the size of the liposome cluster by X-ray diffraction.

  3. Single molecule studies of helicases with magnetic tweezers.

    PubMed

    Hodeib, Samar; Raj, Saurabh; Manosas, M; Zhang, Weiting; Bagchi, Debjani; Ducos, Bertrand; Allemand, Jean-François; Bensimon, David; Croquette, Vincent

    2016-08-01

    Helicases are a broad family of enzymes that perform crucial functions in DNA replication and in the maintenance of DNA and RNA integrity. A detailed mechanical study of helicases on DNA and RNA is possible using single molecule manipulation methods. Among those, magnetic tweezers (or traps) present a convenient, moderate throughput assay (tens of enzymes can be monitored simultaneously) that allow for high resolution (single base-pair) studies of these enzymes in various conditions and on various substrates (double and single stranded DNA and RNA). Here we discuss various implementation of the basic assay relevant for these studies.

  4. Combining confocal microscopy with precise force-scope optical tweezers

    NASA Astrophysics Data System (ADS)

    Richardson, Andrew C.; Reihani, Nader; Oddershede, Lene B.

    2006-08-01

    We demonstrate an example of 'confocal-tweezers' wherein confocal images and precise optical force measurements, using photodiodes, are obtained simultaneously in the x-y plane without moving the objective lens. The optical trap is produced using a 1.064μm cw laser and is combined with Leica's TCS SP5 broadband confocal microscope to trap and image living cells. The unique method by which the confocal images are created facilitates the acquisition of images in areas far from the trapping location. In addition, because the scanning process involves moving galvanic mirrors independently of the objective, the trap is held stable in position and is not subject to any error in position for the x-y scan. We have successfully trapped and confocally imaged 80nm gold colloids, 150nm gold colloids and 1μm polystyrene beads whilst making quantitative measurements of the force applied by the trap on each bead. To the best of our knowledge this is the first time that anyone has combined precise force measuring optical tweezers with confocal microscopy. We also discuss some of the technical challenges involved in advancing the experimental set up to make quantitative force measurements in combination with 3D stacking. Having proven the potential of this system in 2D, we hope to develop it further to investigate the nano-mechanics of cell division through the attachment of gold beads to fluorescently labelled organelles in S. pombe yeast cells.

  5. Use of optical tweezers to probe epithelial mechanosensation

    NASA Astrophysics Data System (ADS)

    Resnick, Andrew

    2010-01-01

    Cellular mechanosensation mechanisms have been implicated in a variety of disease states. Specifically in renal tubules, the primary cilium and associated mechanosensitive ion channels are hypothesized to play a role in water and salt homeostasis, with relevant disease states including polycystic kidney disease and hypertension. Previous experiments investigating ciliary-mediated cellular mechanosensation have used either fluid flow chambers or micropipetting to elicit a biological response. The interpretation of these experiments in terms of the ``ciliary hypothesis'' has been difficult due the spatially distributed nature of the mechanical disturbance-several competing hypotheses regarding possible roles of primary cilium, glycocalyx, microvilli, cell junctions, and actin cytoskeleton exist. I report initial data using optical tweezers to manipulate individual primary cilia in an attempt to elicit a mechanotransduction response-specifically, the release of intracellular calcium. The advantage of using laser tweezers over previous work is that the applied disturbance is highly localized. I find that stimulation of a primary cilium elicits a response, while stimulation of the apical surface membrane does not. These results lend support to the hypothesis that the primary cilium mediates transduction of mechanical strain into a biochemical response in renal epithelia.

  6. Full-field OCT combined with optical tweezer

    NASA Astrophysics Data System (ADS)

    Choi, Woo June; Park, Kwan Seob; Eom, Tae Joong; Oh, Myung-Kyu; Lee, Byeong-Ha

    2012-03-01

    We present an optical tweezer technique assisted full-field optical coherence tomography (FF-OCT) system. The proposed scheme enables ultrahigh-resolution OCT imaging of a floating object optically trapped by single-beam gradient force in medium. The set up consists of a Linnik type of white light interference microscope combined with an optical tweezer system. The optical trap is formed by tightly focusing a 1064 nm Q-switching pulsed laser beam with a microscope objective lens of high numerical aperture (1.0 NA) in sample arm of the OCT interferometer. This co-sharing of probe channel between two of systems enables concurrent actions of trapping and OCT imaging for the sample. OCT imaging of the sample in depth can achieve by positioning the coherence gating with displacement of reference arm in the OCT interferometer. To demonstrate the efficacy of the system, micron-sized dielectric particles and living cells in solution are simultaneously trapped and optically sliced with cellular resolution.

  7. Determination of motility forces on isolated chromosomes with laser tweezers

    PubMed Central

    Khatibzadeh, Nima; Stilgoe, Alexander B.; Bui, Ann A. M.; Rocha, Yesenia; Cruz, Gladys M.; Loke, Vince; Shi, Linda Z.; Nieminen, Timo A.; Rubinsztein-Dunlop, Halina; Berns, Michael W.

    2014-01-01

    Quantitative determination of the motility forces of chromosomes during cell division is fundamental to understanding a process that is universal among eukaryotic organisms. Using an optical tweezers system, isolated mammalian chromosomes were held in a 1064 nm laser trap. The minimum force required to move a single chromosome was determined to be ≈0.8–5 pN. The maximum transverse trapping efficiency of the isolated chromosomes was calculated as ≈0.01–0.02. These results confirm theoretical force calculations of ≈0.1–12 pN to move a chromosome on the mitotic or meiotic spindle. The verification of these results was carried out by calibration of the optical tweezers when trapping microspheres with a diameter of 4.5–15 µm in media with 1–7 cP viscosity. The results of the chromosome and microsphere trapping experiments agree with optical models developed to simulate trapping of cylindrical and spherical specimens. PMID:25359514

  8. Use of optical tweezers to probe epithelial mechanosensation.

    PubMed

    Resnick, Andrew

    2010-01-01

    Cellular mechanosensation mechanisms have been implicated in a variety of disease states. Specifically in renal tubules, the primary cilium and associated mechanosensitive ion channels are hypothesized to play a role in water and salt homeostasis, with relevant disease states including polycystic kidney disease and hypertension. Previous experiments investigating ciliary-mediated cellular mechanosensation have used either fluid flow chambers or micropipetting to elicit a biological response. The interpretation of these experiments in terms of the "ciliary hypothesis" has been difficult due the spatially distributed nature of the mechanical disturbance-several competing hypotheses regarding possible roles of primary cilium, glycocalyx, microvilli, cell junctions, and actin cytoskeleton exist. I report initial data using optical tweezers to manipulate individual primary cilia in an attempt to elicit a mechanotransduction response-specifically, the release of intracellular calcium. The advantage of using laser tweezers over previous work is that the applied disturbance is highly localized. I find that stimulation of a primary cilium elicits a response, while stimulation of the apical surface membrane does not. These results lend support to the hypothesis that the primary cilium mediates transduction of mechanical strain into a biochemical response in renal epithelia.

  9. Invited article: a review of haptic optical tweezers for an interactive microworld exploration.

    PubMed

    Pacoret, Cécile; Régnier, Stéphane

    2013-08-01

    This paper is the first review of haptic optical tweezers, a new technique which associates force feedback teleoperation with optical tweezers. This technique allows users to explore the microworld by sensing and exerting picoNewton-scale forces with trapped microspheres. Haptic optical tweezers also allow improved dexterity of micromanipulation and micro-assembly. One of the challenges of this technique is to sense and magnify picoNewton-scale forces by a factor of 10(12) to enable human operators to perceive interactions that they have never experienced before, such as adhesion phenomena, extremely low inertia, and high frequency dynamics of extremely small objects. The design of optical tweezers for high quality haptic feedback is challenging, given the requirements for very high sensitivity and dynamic stability. The concept, design process, and specification of optical tweezers reviewed here are focused on those intended for haptic teleoperation. In this paper, two new specific designs as well as the current state-of-the-art are presented. Moreover, the remaining important issues are identified for further developments. The initial results obtained are promising and demonstrate that optical tweezers have a significant potential for haptic exploration of the microworld. Haptic optical tweezers will become an invaluable tool for force feedback micromanipulation of biological samples and nano- and micro-assembly parts.

  10. Invited article: a review of haptic optical tweezers for an interactive microworld exploration.

    PubMed

    Pacoret, Cécile; Régnier, Stéphane

    2013-08-01

    This paper is the first review of haptic optical tweezers, a new technique which associates force feedback teleoperation with optical tweezers. This technique allows users to explore the microworld by sensing and exerting picoNewton-scale forces with trapped microspheres. Haptic optical tweezers also allow improved dexterity of micromanipulation and micro-assembly. One of the challenges of this technique is to sense and magnify picoNewton-scale forces by a factor of 10(12) to enable human operators to perceive interactions that they have never experienced before, such as adhesion phenomena, extremely low inertia, and high frequency dynamics of extremely small objects. The design of optical tweezers for high quality haptic feedback is challenging, given the requirements for very high sensitivity and dynamic stability. The concept, design process, and specification of optical tweezers reviewed here are focused on those intended for haptic teleoperation. In this paper, two new specific designs as well as the current state-of-the-art are presented. Moreover, the remaining important issues are identified for further developments. The initial results obtained are promising and demonstrate that optical tweezers have a significant potential for haptic exploration of the microworld. Haptic optical tweezers will become an invaluable tool for force feedback micromanipulation of biological samples and nano- and micro-assembly parts. PMID:24007046

  11. Structure and dynamics of single DNA molecules manipulated by magnetic tweezers and or flow

    PubMed Central

    Leuba, Sanford H.; Wheeler, Travis B.; Cheng, Chao-Min; LeDuc, Philip R.; Fernández-Sierra, Mónica; Quiñones, Edwin

    2009-01-01

    Here we describe experiments which employ magnetic tweezers and or microfluidics to manipulate single DNA molecules. We describe the use of magnetic tweezers coupled to an inverted microscope as well as the use of a magnetic tweezers setup with an upright microscope. Using a chamber prepared via soft lithography, we also describe a microfluidic device for the manipulation of individual DNA molecules. Finally, we present some past successful examples of using these approaches to elucidate unique information about protein-nucleic acid interactions. PMID:19015032

  12. Holographic optical tweezers: manipulations at an air-liquid interface

    NASA Astrophysics Data System (ADS)

    Jesacher, Alexander; Fürhapter, Severin; Maurer, Christian; Bernet, Stefan; Ritsch-Marte, Monika

    2006-08-01

    By performing experiments at an air-water interface, we operate Holographic Optical Tweezers in a qualitatively new environment. In this regime, trapping and moving of micro particles may allow access to parameters like local viscosity and surface tension. Polystyrene micro beads are naturally stabilized in the interface due to a minimum in surface energy. For this reason, they can also be manipulated by light patterns with small axial field gradients, without causing the particles to escape due to scattering forces. In this manner, the interface provides a true two-dimensional "working environment", where particles can be manipulated with high effciency. For example, we demonstrate different optical "micro tools", which utilize scattering and gradient forces to enable controlled transport of matter within the surface.

  13. Skewed Brownian Fluctuations in Single-Molecule Magnetic Tweezers

    PubMed Central

    Burnham, Daniel R.; De Vlaminck, Iwijn; Henighan, Thomas; Dekker, Cees

    2014-01-01

    Measurements in magnetic tweezers rely upon precise determination of the position of a magnetic microsphere. Fluctuations in the position due to Brownian motion allows calculation of the applied force, enabling deduction of the force-extension response function for a single DNA molecule that is attached to the microsphere. The standard approach relies upon using the mean of position fluctuations, which is valid when the microsphere axial position fluctuations obey a normal distribution. However, here we demonstrate that nearby surfaces and the non-linear elasticity of DNA can skew the distribution. Through experiment and simulations, we show that such a skewing leads to inaccurate position measurements which significantly affect the extracted DNA extension and mechanical properties, leading to up to two-fold errors in measured DNA persistence length. We develop a simple, robust and easily implemented method to correct for such mismeasurements. PMID:25265383

  14. Combined holographic-mechanical optical tweezers: Construction, optimization, and calibration

    SciTech Connect

    Hanes, Richard D. L.; Jenkins, Matthew C.; Egelhaaf, Stefan U.

    2009-08-15

    A spatial light modulator (SLM) and a pair of galvanometer-mounted mirrors (GMM) were combined into an optical tweezers setup. This provides great flexibility as the SLM creates an array of traps, which can be moved smoothly and quickly with the GMM. To optimize performance, the effect of the incidence angle on the SLM with respect to phase and intensity response was investigated. Although it is common to use the SLM at an incidence angle of 45 deg., smaller angles give a full 2{pi} phase shift and an output intensity which is less dependent on the magnitude of the phase shift. The traps were calibrated using an active oscillatory technique and a passive probability distribution method.

  15. Trapping particles using waveguide-coupled gold bowtie plasmonic tweezers.

    PubMed

    Lin, Pin-Tso; Chu, Heng-Yi; Lu, Tsan-Wen; Lee, Po-Tsung

    2014-12-21

    We propose and demonstrate a trapping configuration integrating coupled waveguides and gold bowtie structures to form near-field plasmonic tweezers. Compared with excitation from the top, waves coupled through the waveguide can excite specific bowties on the waveguide and trap particles precisely. Thus this scheme is more efficient and compact, and will assist the circuit design on a chip. With lightning rod and gap effects, the gold bowtie structures can generate highly concentrated resonant fields and induce trapping forces as strong as 652 pN W(-1) on particles with diameters as small as 20 nm. This trapping capability is investigated numerically and verified experimentally with observations of the transport, trapping, and release of particles in the system. PMID:25288366

  16. Probing multiscale mechanics of collagen with optical tweezers

    NASA Astrophysics Data System (ADS)

    Shayegan, Marjan; Rezaei, Naghmeh; Lam, Norman H.; Altindal, Tuba; Wieczorek, Andrew; Forde, Nancy R.

    2013-09-01

    How the molecular structure of the structural, extracellular matrix protein collagen correlates with its mechanical properties at different hierarchical structural levels is not known. We demonstrate the utility of optical tweezers to probe collagen's mechanical response throughout its assembly hierarchy, from single molecule force-extension measurements through microrheology measurements on solutions of collagen molecules, collagen fibrillar gels and gelatin. These experiments enable the determination of collagen's flexibility, mechanics, and timescales and strengths of interaction at different levels of hierarchy, information critical to developing models of how collagen's physiological function and stability are influenced by its chemical composition. By investigating how the viscoelastic properties of collagen are affected by the presence of telopeptides, protein domains that strongly influence fibril formation, we demonstrate that these play a role in conferring transient elasticity to collagen solutions.

  17. Leukocyte-endothelium interaction: measurement by laser tweezers force spectroscopy.

    PubMed

    Wang, Shi-Kang; Chiu, Jeng-Jiann; Lee, Ming-Rou; Chou, Shih-Chin; Chen, Li-Jing; Hwang, Ned H C

    2006-09-01

    Leukocyte adhesion to vascular endothelium is an initial step of many inflammatory diseases. Although the atomic force microscopy (AFM) measurements of leukocyte-endothelial interaction have been recently introduced. with cell adhesion force unbinding curves (CAFUC). We obtained pico-Newton force in the initial interaction between a single living THP-1 cell and HUVEC monolayer using a custom-built laser tweezers (LT) system. The measured quantities included the non-linear force-distance relationship, and the effect of yielding in cell detachment. It is possible to introduce a time scale into the LT cell-detachment experiments for further exploration and more detailed information on the viscoelastic properties of living cells. PMID:16960761

  18. Combined holographic-mechanical optical tweezers: construction, optimization, and calibration.

    PubMed

    Hanes, Richard D L; Jenkins, Matthew C; Egelhaaf, Stefan U

    2009-08-01

    A spatial light modulator (SLM) and a pair of galvanometer-mounted mirrors (GMM) were combined into an optical tweezers setup. This provides great flexibility as the SLM creates an array of traps, which can be moved smoothly and quickly with the GMM. To optimize performance, the effect of the incidence angle on the SLM with respect to phase and intensity response was investigated. Although it is common to use the SLM at an incidence angle of 45 degrees, smaller angles give a full 2pi phase shift and an output intensity which is less dependent on the magnitude of the phase shift. The traps were calibrated using an active oscillatory technique and a passive probability distribution method. PMID:19725658

  19. Mechanical properties of a giant liposome studied using optical tweezers

    NASA Astrophysics Data System (ADS)

    Shitamichi, Yoko; Ichikawa, Masatoshi; Kimura, Yasuyuki

    2009-09-01

    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 σ and the bending rigidity κ of the lipid membrane are obtained from the measured force-extension curve. In a one-phase liposome, it was found that σ increases as the charged component increases but κ 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.

  20. Extending the Range for Force Calibration in Magnetic Tweezers

    PubMed Central

    Daldrop, Peter; Brutzer, Hergen; Huhle, Alexander; Kauert, Dominik J.; Seidel, Ralf

    2015-01-01

    Magnetic tweezers are a wide-spread tool used to study the mechanics and the function of a large variety of biomolecules and biomolecular machines. This tool uses a magnetic particle and a strong magnetic field gradient to apply defined forces to the molecule of interest. Forces are typically quantified by analyzing the lateral fluctuations of the biomolecule-tethered particle in the direction perpendicular to the applied force. Since the magnetic field pins the anisotropy axis of the particle, the lateral fluctuations follow the geometry of a pendulum with a short pendulum length along and a long pendulum length perpendicular to the field lines. Typically, the short pendulum geometry is used for force calibration by power-spectral-density (PSD) analysis, because the movement of the bead in this direction can be approximated by a simple translational motion. Here, we provide a detailed analysis of the fluctuations according to the long pendulum geometry and show that for this direction, both the translational and the rotational motions of the particle have to be considered. We provide analytical formulas for the PSD of this coupled system that agree well with PSDs obtained in experiments and simulations and that finally allow a faithful quantification of the magnetic force for the long pendulum geometry. We furthermore demonstrate that this methodology allows the calibration of much larger forces than the short pendulum geometry in a tether-length-dependent manner. In addition, the accuracy of determination of the absolute force is improved. Our force calibration based on the long pendulum geometry will facilitate high-resolution magnetic-tweezers experiments that rely on short molecules and large forces, as well as highly parallelized measurements that use low frame rates. PMID:25992733

  1. Measuring red blood cell aggregation forces using double optical tweezers.

    PubMed

    Fernandes, Heloise P; Fontes, Adriana; Thomaz, André; Castro, Vagner; Cesar, Carlos L; Barjas-Castro, Maria L

    2013-04-01

    Classic immunohematology approaches, based on agglutination techniques, have been used in manual and automated immunohematology laboratory routines. Red blood cell (RBC) agglutination depends on intermolecular attractive forces (hydrophobic bonds, Van der Walls, electrostatic forces and hydrogen bonds) and repulsive interactions (zeta potential). The aim of this study was to measure the force involved in RBC aggregation using double optical tweezers, in normal serum, in the presence of erythrocyte antibodies and associated to agglutination potentiator solutions (Dextran, low ionic strength solution [LISS] and enzymes). The optical tweezers consisted of a neodymium:yattrium aluminium garnet (Nd:YAG) laser beam focused through a microscope equipped with a minicam, which registered the trapped cell image in a computer where they could be analyzed using a software. For measuring RBC aggregation, a silica bead attached to RBCs was trapped and the force needed to slide one RBC over the other, as a function of the velocities, was determined. The median of the RBC aggregation force measured in normal serum (control) was 1 × 10(-3) (0.1-2.5) poise.cm. The samples analyzed with anti-D showed 2 × 10(-3) (1.0-4.0) poise.cm (p < 0.001). RBC diluted in potentiator solutions (Dextran 0.15%, Bromelain and LISS) in the absence of erythrocyte antibodies, did not present agglutination. High adherence was observed when RBCs were treated with papain. Results are in agreement with the imunohematological routine, in which non-specific results are not observed when using LISS, Dextran and Bromelain. Nevertheless, false positive results are frequently observed in manual and automated microplate analyzer using papain enzyme. The methodology proposed is simple and could provide specific information with the possibility of meansuration regarding RBC interaction.

  2. Extending the range for force calibration in magnetic tweezers.

    PubMed

    Daldrop, Peter; Brutzer, Hergen; Huhle, Alexander; Kauert, Dominik J; Seidel, Ralf

    2015-05-19

    Magnetic tweezers are a wide-spread tool used to study the mechanics and the function of a large variety of biomolecules and biomolecular machines. This tool uses a magnetic particle and a strong magnetic field gradient to apply defined forces to the molecule of interest. Forces are typically quantified by analyzing the lateral fluctuations of the biomolecule-tethered particle in the direction perpendicular to the applied force. Since the magnetic field pins the anisotropy axis of the particle, the lateral fluctuations follow the geometry of a pendulum with a short pendulum length along and a long pendulum length perpendicular to the field lines. Typically, the short pendulum geometry is used for force calibration by power-spectral-density (PSD) analysis, because the movement of the bead in this direction can be approximated by a simple translational motion. Here, we provide a detailed analysis of the fluctuations according to the long pendulum geometry and show that for this direction, both the translational and the rotational motions of the particle have to be considered. We provide analytical formulas for the PSD of this coupled system that agree well with PSDs obtained in experiments and simulations and that finally allow a faithful quantification of the magnetic force for the long pendulum geometry. We furthermore demonstrate that this methodology allows the calibration of much larger forces than the short pendulum geometry in a tether-length-dependent manner. In addition, the accuracy of determination of the absolute force is improved. Our force calibration based on the long pendulum geometry will facilitate high-resolution magnetic-tweezers experiments that rely on short molecules and large forces, as well as highly parallelized measurements that use low frame rates.

  3. Measurement of interaction forces between red blood cells in aggregates by optical tweezers

    SciTech Connect

    Maklygin, A Yu; Priezzhev, A V; Karmenian, A; Nikitin, Sergei Yu; Obolenskii, I S; Lugovtsov, Andrei E; Kisun Li

    2012-06-30

    We have fabricated double-beam optical tweezers and demonstrated the possibility of their use for measuring the interaction forces between red blood cells (erythrocytes). It has been established experimentally that prolonged trapping of red blood cells in a tightly focused laser beam does not cause any visible changes in their shape or size. We have measured the interaction between red blood cells in the aggregate, deformed by optical tweezers.

  4. MatLab program for precision calibration of optical tweezers

    NASA Astrophysics Data System (ADS)

    Tolić-Nørrelykke, Iva Marija; Berg-Sørensen, Kirstine; Flyvbjerg, Henrik

    2004-06-01

    Optical tweezers are used as force transducers in many types of experiments. The force they exert in a given experiment is known only after a calibration. Computer codes that calibrate optical tweezers with high precision and reliability in the ( x, y)-plane orthogonal to the laser beam axis were written in MatLab (MathWorks Inc.) and are presented here. The calibration is based on the power spectrum of the Brownian motion of a dielectric bead trapped in the tweezers. Precision is achieved by accounting for a number of factors that affect this power spectrum. First, cross-talk between channels in 2D position measurements is tested for, and eliminated if detected. Then, the Lorentzian power spectrum that results from the Einstein-Ornstein-Uhlenbeck theory, is fitted to the low-frequency part of the experimental spectrum in order to obtain an initial guess for parameters to be fitted. Finally, a more complete theory is fitted, a theory that optionally accounts for the frequency dependence of the hydrodynamic drag force and hydrodynamic interaction with a nearby cover slip, for effects of finite sampling frequency (aliasing), for effects of anti-aliasing filters in the data acquisition electronics, and for unintended "virtual" filtering caused by the position detection system. Each of these effects can be left out or included as the user prefers, with user-defined parameters. Several tests are applied to the experimental data during calibration to ensure that the data comply with the theory used for their interpretation: Independence of x- and y-coordinates, Hooke's law, exponential distribution of power spectral values, uncorrelated Gaussian scatter of residual values. Results are given with statistical errors and covariance matrix. Program summaryTitle of program: tweezercalib Catalogue identifier: ADTV Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland. Program Summary URL:http://cpc.cs.qub.ac.uk/summaries/ADTV Computer for

  5. Automated multi-parametric sorting of micron-sized particles via multi-trap laser tweezers

    NASA Astrophysics Data System (ADS)

    Kaputa, Daniel S.

    The capabilities of laser tweezers have rapidly expanded since the first demonstration by Ashkin and co-workers in 1970 of the ability to trap particles using optical energy. Laser tweezers have been used to measure piconewton forces in many biological and material science application, sort bacteria, measure DNA bond strength, and even perform microsurgery. The laser tweezers system developed for this dissertation foreshadows the next generation of laser tweezer systems that provide automated particle sorted based upon multiple criteria. Many laser tweezer sorting applications today entail the operator sorting cells from a bulk sample, one by one. This dissertation demonstrates the technologies of pattern recognition and image processing that allow for an entire microscope slide to be sorted without any operator intervention. We already live in an automated world where the cars we drive are built by machines instead of humans. The technology is there, and the only factors limiting the advancements of fully automated biological instrumentation is the lack of developers with the appropriate knowledge sets. This dissertation introduces the concept of sorting particles via a multi-parametric approach where several parameters such as size, fluorescence, and Raman spectra are used as sorting criteria. Since the advent of laser tweezers, several groups have demonstrated the ability to sort cells and other particle by size, or by fluorescence, or by any other parameter, but to our knowledge there does not exist a laser tweezer sorting system that can sort particles based upon multiple parameters. Sorting via a single parameter can be a severe limitation as the method lacks the robustness and class specificity that exists when sorting based upon multiple parameters. Simply put, it makes more sense to determine the worth of a baseball card by considering it's condition as well as it's age, rather then solely upon its condition. By adding another parameter such as the name of

  6. Parallel lipoplex folding pathways revealed using magnetic tweezers

    PubMed Central

    Sun, Zhiqiang; Tikhonova, Elena B.; Zgurskaya, Helen I.; Rybenkov, Valentin V.

    2012-01-01

    Lipid-coated DNA nanoparticles (lipoplexes) are a powerful gene delivery tool with promising therapeutic applications. The mechanism of lipoplex assembly remains poorly understood. We explored DNA packing by a cationic lipid DSTAP (distearoyl trimethylammonium-propane) using magnetic tweezers. DSTAP-induced DNA condensation occurred as a series of bursts with the mean step size of 60 nm to 80 nm. The pause time preceding the steps could be approximated as a bimodal distribution, which reveals at least two distinct condensation pathways. The rapidly condensed DNA was more resilient to force-induced decondensation. The proportion of the stable, fast-formed complexes decreased at high salt concentrations. A similar trend was observed in bulk experiments. Lipoplexes assembled at low salt concentration more efficiently shielded DNA from fluorescent dyes and DNase even after transfer to the high salt conditions. These data reveal that lipoplex folding occurs via two parallel pathways even at the single molecule level. The progress through the two pathways can be monitored in real time using single DNA manipulations. The relative efficiency of the two pathways can be varied by external conditions. PMID:22988939

  7. Manipulating and assembling metallic beads with Optoelectronic Tweezers

    PubMed Central

    Zhang, Shuailong; Juvert, Joan; Cooper, Jonathan M.; Neale, Steven L.

    2016-01-01

    Optoelectronic tweezers (OET) or light-patterned dielectrophoresis (DEP) has been developed as a micromanipulation technology for controlling micro- and nano-particles with applications such as cell sorting and studying cell communications. Additionally, the capability of moving small objects accurately and assembling them into arbitrary 2D patterns also makes OET an attractive technology for microfabrication applications. In this work, we demonstrated the use of OET to manipulate conductive silver-coated Poly(methyl methacrylate) (PMMA) microspheres (50 μm diameter) into tailored patterns. It was found that the microspheres could be moved at a max velocity of 3200 μm/s, corresponding to 4.2 nano-newton (10−9 N) DEP force, and also could be positioned with high accuracy via this DEP force. The underlying mechanism for this strong DEP force is shown by our simulations to be caused by a significant increase of the electric field close to the particles, due to the interaction between the field and the silver shells coating the microspheres. The associated increase in electrical gradient causes DEP forces that are much stronger than any previously reported for an OET device, which facilitates manipulation of the metallic microspheres efficiently without compromise in positioning accuracy and is important for applications on electronic component assembling and circuit construction. PMID:27599445

  8. Bio-syncretic tweezers actuated by microorganisms: modeling and analysis.

    PubMed

    Zhang, C; Xie, S X; Wang, W X; Xi, N; Wang, Y C; Liu, L Q

    2016-09-28

    Advancements in micro-/nano-technology have led to the development of micro-manipulators. However, some challenges remain; for instance, the efficiency, precision and flexibility of micro-manipulators restrain their applications. This paper proposes a bio-tweezer system to flexibly manipulate micro-objects with bio-actuation via local light-induced high-concentration microorganisms in two different manipulation modes: light-spot induced mode and geometric shape-induced mode. Depending on the shape of micro-objects, either 2-dimensional translation or 1-dimensional rotation can be achieved. Based on the Langevin equation, a mathematical model considering both hydrodynamics and mimicked Brownian motion is proposed to analyze the bio-manipulation performance of the microorganisms; the model was validated by experiments to translate micro-particles in a two-dimensional plane and to rotate a micro-gear structure around its axis. This paper will aid in the development of micro-manipulators and the quantitative understanding of micro-/nano-manipulation actuated by microorganisms. PMID:27432020

  9. Magnetic tweezers force calibration for molecules that exhibit conformational switching

    NASA Astrophysics Data System (ADS)

    Jacobson, David R.; Saleh, Omar A.

    2016-09-01

    High spatial and temporal resolution magnetic tweezers experiments allow for the direct calibration of pulling forces applied to short biomolecules. In one class of experiments, a force is applied to a structured RNA or protein to induce an unfolding transition; when the force is maintained at particular values, the molecule can exhibit conformational switching between the folded and unfolded states or between intermediate states. Here, we analyze the degree to which common force calibration approaches, involving the fitting of model functions to the Allan variance or power spectral density of the bead trajectory, are biased by this conformational switching. We find significant effects in two limits: that of large molecular extension changes between the two states, in which alternative fitting functions must be used, and that of very fast switching kinetics, in which the force calibration cannot be recovered due to the slow diffusion time of the magnetic bead. We use simulations and high-resolution RNA hairpin data to show that most biophysical experiments do not occur in either of these limits.

  10. Membrane tether formation from outer hair cells with optical tweezers.

    PubMed Central

    Li, Zhiwei; Anvari, Bahman; Takashima, Masayoshi; Brecht, Peter; Torres, Jorge H; Brownell, William E

    2002-01-01

    Optical tweezers were used to characterize the mechanical properties of the outer hair cell (OHC) plasma membrane by pulling tethers with 4.5-microm polystyrene beads. Tether formation force and tether force were measured in static and dynamic conditions. A greater force was required for tether formations from OHC lateral wall (499 +/- 152 pN) than from OHC basal end (142 +/- 49 pN). The difference in the force required to pull tethers is consistent with an extensive cytoskeletal framework associated with the lateral wall known as the cortical lattice. The apparent plasma membrane stiffness, estimated under the static conditions by measuring tether force at different tether length, was 3.71 pN/microm for OHC lateral wall and 4.57 pN/microm for OHC basal end. The effective membrane viscosity was measured by pulling tethers at different rates while continuously recording the tether force, and estimated in the range of 2.39 to 5.25 pN x s/microm. The viscous force most likely results from the viscous interactions between plasma membrane lipids and the OHC cortical lattice and/or integral membrane proteins. The information these studies provide on the mechanical properties of the OHC lateral wall is important for understanding the mechanism of OHC electromotility. PMID:11867454

  11. Manipulating and assembling metallic beads with Optoelectronic Tweezers.

    PubMed

    Zhang, Shuailong; Juvert, Joan; Cooper, Jonathan M; Neale, Steven L

    2016-09-07

    Optoelectronic tweezers (OET) or light-patterned dielectrophoresis (DEP) has been developed as a micromanipulation technology for controlling micro- and nano-particles with applications such as cell sorting and studying cell communications. Additionally, the capability of moving small objects accurately and assembling them into arbitrary 2D patterns also makes OET an attractive technology for microfabrication applications. In this work, we demonstrated the use of OET to manipulate conductive silver-coated Poly(methyl methacrylate) (PMMA) microspheres (50 μm diameter) into tailored patterns. It was found that the microspheres could be moved at a max velocity of 3200 μm/s, corresponding to 4.2 nano-newton (10(-9) N) DEP force, and also could be positioned with high accuracy via this DEP force. The underlying mechanism for this strong DEP force is shown by our simulations to be caused by a significant increase of the electric field close to the particles, due to the interaction between the field and the silver shells coating the microspheres. The associated increase in electrical gradient causes DEP forces that are much stronger than any previously reported for an OET device, which facilitates manipulation of the metallic microspheres efficiently without compromise in positioning accuracy and is important for applications on electronic component assembling and circuit construction.

  12. Detecting Bacterial Surface Organelles on Single Cells Using Optical Tweezers.

    PubMed

    Zakrisson, Johan; Singh, Bhupender; Svenmarker, Pontus; Wiklund, Krister; Zhang, Hanqing; Hakobyan, Shoghik; Ramstedt, Madeleine; Andersson, Magnus

    2016-05-10

    Bacterial cells display a diverse array of surface organelles that are important for a range of processes such as intercellular communication, motility and adhesion leading to biofilm formation, infections, and bacterial spread. More specifically, attachment to host cells by Gram-negative bacteria are mediated by adhesion pili, which are nanometers wide and micrometers long fibrous organelles. Since these pili are significantly thinner than the wavelength of visible light, they cannot be detected using standard light microscopy techniques. At present, there is no fast and simple method available to investigate if a single cell expresses pili while keeping the cell alive for further studies. In this study, we present a method to determine the presence of pili on a single bacterium. The protocol involves imaging the bacterium to measure its size, followed by predicting the fluid drag based on its size using an analytical model, and thereafter oscillating the sample while a single bacterium is trapped by an optical tweezer to measure its effective fluid drag. Comparison between the predicted and the measured fluid drag thereby indicate the presence of pili. Herein, we verify the method using polymer coated silica microspheres and Escherichia coli bacteria expressing adhesion pili. Our protocol can in real time and within seconds assist single cell studies by distinguishing between piliated and nonpiliated bacteria.

  13. Force measurements with optical tweezers inside living cells

    NASA Astrophysics Data System (ADS)

    Mas, Josep; Farré, Arnau; Sancho-Parramon, Jordi; Martín-Badosa, Estela; Montes-Usategui, Mario

    2014-09-01

    The force exerted by optical tweezers can be measured by tracking the momentum changes of the trapping beam, a method which is more general and powerful than traditional calibration techniques as it is based on first principles, but which has not been brought to its full potential yet, probably due to practical difficulties when combined with high-NA optical traps, such as the necessity to capture a large fraction of the scattered light. We show that it is possible to measure forces on arbitrary biological objects inside cells without an in situ calibration, using this approach. The instrument can be calibrated by measuring three scaling parameters that are exclusively determined by the design of the system, thus obtaining a conversion factor from volts to piconewtons that is theoretically independent of the physical properties of the sample and its environment. We prove that this factor keeps valid inside cells as it shows good agreement with other calibration methods developed in recent years for viscoelastic media. Finally, we apply the method to measuring the stall forces of kinesin and dynein in living A549 cells.

  14. Manipulating and assembling metallic beads with Optoelectronic Tweezers.

    PubMed

    Zhang, Shuailong; Juvert, Joan; Cooper, Jonathan M; Neale, Steven L

    2016-01-01

    Optoelectronic tweezers (OET) or light-patterned dielectrophoresis (DEP) has been developed as a micromanipulation technology for controlling micro- and nano-particles with applications such as cell sorting and studying cell communications. Additionally, the capability of moving small objects accurately and assembling them into arbitrary 2D patterns also makes OET an attractive technology for microfabrication applications. In this work, we demonstrated the use of OET to manipulate conductive silver-coated Poly(methyl methacrylate) (PMMA) microspheres (50 μm diameter) into tailored patterns. It was found that the microspheres could be moved at a max velocity of 3200 μm/s, corresponding to 4.2 nano-newton (10(-9) N) DEP force, and also could be positioned with high accuracy via this DEP force. The underlying mechanism for this strong DEP force is shown by our simulations to be caused by a significant increase of the electric field close to the particles, due to the interaction between the field and the silver shells coating the microspheres. The associated increase in electrical gradient causes DEP forces that are much stronger than any previously reported for an OET device, which facilitates manipulation of the metallic microspheres efficiently without compromise in positioning accuracy and is important for applications on electronic component assembling and circuit construction. PMID:27599445

  15. Numerical study of the properties of optical vortex array laser tweezers.

    PubMed

    Kuo, Chun-Fu; Chu, Shu-Chun

    2013-11-01

    Chu et al. constructed a kind of Ince-Gaussian modes (IGM)-based vortex array laser beams consisting of p x p embedded optical vortexes from Ince-Gaussian modes, IG(e)(p,p) modes [Opt. Express 16, 19934 (2008)]. Such an IGM-based vortex array laser beams maintains its vortex array profile during both propagation and focusing, and is applicable to optical tweezers. This study uses the discrete dipole approximation (DDA) method to study the properties of the IGM-based vortex array laser tweezers while it traps dielectric particles. This study calculates the resultant force exerted on the spherical dielectric particles of different sizes situated at the IGM-based vortex array laser beam waist. Numerical results show that the number of trapping spots of a structure light (i.e. IGM-based vortex laser beam), is depended on the relation between the trapped particle size and the structure light beam size. While the trapped particle is small comparing to the beam size of the IGM-based vortex array laser beams, the IGM-based vortex array laser beams tweezers are suitable for multiple traps. Conversely, the tweezers is suitable for single traps. The results of this study is useful to the future development of the vortex array laser tweezers applications. PMID:24216863

  16. Mapping force of interaction between PLGA nanoparticle with cell membrane using optical tweezers

    NASA Astrophysics Data System (ADS)

    Chhajed, Suyash; Gu, Ling; Homayoni, Homa; Nguyen, Kytai; Mohanty, Samarendra

    2011-03-01

    Drug delivery using magnetic (Fe 3 O4) Poly Lactic-co-Glycolic Acid (PLGA) nanoparticles is finding increasing usage in therapeutic applications due to its biodegradability, biocompatibility and targeted localization. Since optical tweezers allow non-contact, highly sensitive force measurement, we utilized optical tweezers for studying interaction forces between the Fe 3 O4 -PLGA nanoparticles with prostate cancer PC3 cells. Presence of Fe 3 O4 within the PLGA shell allowed efficient trapping of these nanoparticles in near-IR optical tweezers. The conglomerated PLGA nanoparticles could be dispersed by use of the optical tweezers. Calibration of trapping stiffness as a function of laser beam power was carried out using equipartition theorem method, where the mean square displacement was measured with high precision using time-lapse fluorescence imaging of the nanoparticles. After the trapped PLGA nanoparticle was brought in close vicinity of the PC3 cell membrane, displacement of the nanoparticle from trap center was measured as a function of time. In short time scale (30 sec) , whiletheforceofinteractionwaswithin 0.2 pN , theforceincreasedbeyond 1 pNatlongertimescales (~ 10 min). We will present the results of the time-varying force of interactions between PLGA nanoparticles with PC3 cells using optical tweezers.

  17. Surface forces and drag coefficients of microspheres near a plane surface measured with optical tweezers.

    PubMed

    Schäffer, Erik; Nørrelykke, Simon F; Howard, Jonathon

    2007-03-27

    Optical tweezers are widely used to measure molecular forces in biology. Such measurements are often influenced by a nearby surface that can perturb both the calibration of the tweezers as well as the hydrodynamic forces acting on microspheres to which the biomolecules are attached. In this study, we have used a very stable optical tweezers setup employing a recently developed calibration method (Tolić-Nørrelykke, S. F.; Schäffer, E.; Howard, J.; Pavone, F. S.; Jülicher, F.; Flyvbjerg, H. Rev. Sci. Instrum. 2006, 77 (10), 103101) to determine how the calibration of the tweezers and the forces on the microspheres depend on the height above the surface. We show that the displacement sensitivity of the tweezers is modulated by a standing light wave between the microsphere and the surface. We measured the dependence of the drag coefficient on height and compared it to exact and closed-form solutions to the Navier-Stokes equations. Also, we measured the surface force gradients in different salt solutions and for different surface blocking methods. For a given blocking method, our data suggest that microspheres can experience attractive and/or repulsive forces close to surfaces. For example, a Teflon layer reduces attractive interactions, and the presence of casein can lead to long-range repulsive interactions. These measurements are a prerequisite for the accurate measurement of normal forces with respect to an interface that occur in biological molecules held between surfaces.

  18. Numerical study of the properties of optical vortex array laser tweezers.

    PubMed

    Kuo, Chun-Fu; Chu, Shu-Chun

    2013-11-01

    Chu et al. constructed a kind of Ince-Gaussian modes (IGM)-based vortex array laser beams consisting of p x p embedded optical vortexes from Ince-Gaussian modes, IG(e)(p,p) modes [Opt. Express 16, 19934 (2008)]. Such an IGM-based vortex array laser beams maintains its vortex array profile during both propagation and focusing, and is applicable to optical tweezers. This study uses the discrete dipole approximation (DDA) method to study the properties of the IGM-based vortex array laser tweezers while it traps dielectric particles. This study calculates the resultant force exerted on the spherical dielectric particles of different sizes situated at the IGM-based vortex array laser beam waist. Numerical results show that the number of trapping spots of a structure light (i.e. IGM-based vortex laser beam), is depended on the relation between the trapped particle size and the structure light beam size. While the trapped particle is small comparing to the beam size of the IGM-based vortex array laser beams, the IGM-based vortex array laser beams tweezers are suitable for multiple traps. Conversely, the tweezers is suitable for single traps. The results of this study is useful to the future development of the vortex array laser tweezers applications.

  19. Automatic real time evaluation of red blood cell elasticity by optical tweezers

    NASA Astrophysics Data System (ADS)

    Moura, Diógenes S.; Silva, Diego C. N.; Williams, Ajoke J.; Bezerra, Marcos A. C.; Fontes, Adriana; de Araujo, Renato E.

    2015-05-01

    Optical tweezers have been used to trap, manipulate, and measure individual cell properties. In this work, we show that the association of a computer controlled optical tweezers system with image processing techniques allows rapid and reproducible evaluation of cell deformability. In particular, the deformability of red blood cells (RBCs) plays a key role in the transport of oxygen through the blood microcirculation. The automatic measurement processes consisted of three steps: acquisition, segmentation of images, and measurement of the elasticity of the cells. An optical tweezers system was setup on an upright microscope equipped with a CCD camera and a motorized XYZ stage, computer controlled by a Labview platform. On the optical tweezers setup, the deformation of the captured RBC was obtained by moving the motorized stage. The automatic real-time homemade system was evaluated by measuring RBCs elasticity from normal donors and patients with sickle cell anemia. Approximately 150 erythrocytes were examined, and the elasticity values obtained by using the developed system were compared to the values measured by two experts. With the automatic system, there was a significant time reduction (60 × ) of the erythrocytes elasticity evaluation. Automated system can help to expand the applications of optical tweezers in hematology and hemotherapy.

  20. Fiber based optical tweezers for simultaneous in situ force exertion and measurements in a 3D polyacrylamide gel compartment.

    PubMed

    Ti, Chaoyang; Thomas, Gawain M; Ren, Yundong; Zhang, Rui; Wen, Qi; Liu, Yuxiang

    2015-07-01

    Optical tweezers play an important role in biological applications. However, it is difficult for traditional optical tweezers based on objective lenses to work in a three-dimensional (3D) solid far away from the substrate. In this work, we develop a fiber based optical trapping system, namely inclined dual fiber optical tweezers, that can simultaneously apply and measure forces both in water and in a 3D polyacrylamide gel matrix. In addition, we demonstrate in situ, non-invasive characterization of local mechanical properties of polyacrylamide gel by measurements on an embedded bead. The fiber optical tweezers measurements agree well with those of atomic force microscopy (AFM). The inclined dual fiber optical tweezers provide a promising and versatile tool for cell mechanics study in 3D environments.

  1. Fiber based optical tweezers for simultaneous in situ force exertion and measurements in a 3D polyacrylamide gel compartment

    PubMed Central

    Ti, Chaoyang; Thomas, Gawain M; Ren, Yundong; Zhang, Rui; Wen, Qi; Liu, Yuxiang

    2015-01-01

    Optical tweezers play an important role in biological applications. However, it is difficult for traditional optical tweezers based on objective lenses to work in a three-dimensional (3D) solid far away from the substrate. In this work, we develop a fiber based optical trapping system, namely inclined dual fiber optical tweezers, that can simultaneously apply and measure forces both in water and in a 3D polyacrylamide gel matrix. In addition, we demonstrate in situ, non-invasive characterization of local mechanical properties of polyacrylamide gel by measurements on an embedded bead. The fiber optical tweezers measurements agree well with those of atomic force microscopy (AFM). The inclined dual fiber optical tweezers provide a promising and versatile tool for cell mechanics study in 3D environments. PMID:26203364

  2. Optical disassembly of cellular clusters by tunable ‘tug-of-war’ tweezers

    PubMed Central

    Bezryadina, Anna S; Preece, Daryl C; Chen, Joseph C; Chen, Zhigang

    2016-01-01

    Bacterial biofilms underlie many persistent infections, posing major hurdles in antibiotic treatment. Here we design and demonstrate ‘tug-of-war’ optical tweezers that can facilitate the assessment of cell–cell adhesion—a key contributing factor to biofilm development, thanks to the combined actions of optical scattering and gradient forces. With a customized optical landscape distinct from that of conventional tweezers, not only can such ‘tug-of-war’ tweezers stably trap and stretch a rod-shaped bacterium in the observing plane, but, more importantly, they can also impose a tunable lateral force that pulls apart cellular clusters without any tethering or mechanical movement. As a proof of principle, we examined a Sinorhizobium meliloti strain that forms robust biofilms and found that the strength of intercellular adhesion depends on the growth medium. This technique may herald new photonic tools for optical manipulation and biofilm study, as well as other biological applications.

  3. Hong-Ou-Mandel atom interferometry in tunnel-coupled optical tweezers

    NASA Astrophysics Data System (ADS)

    Lester, Brian; Kaufman, Adam; Reynolds, Collin; Wall, Michael; Foss-Feig, Michael; Hazzard, Kaden; Rey, Ana Maria; Regal, Cindy

    2014-05-01

    We present recent work in which we demonstrate near-complete control over all the internal and external degrees of freedom of laser-cooled 87Rb atoms trapped in sub-micron optical tweezers. Utilizing this control for two atoms in two optical tweezers, we implement a massive-particle analog of the Hong-Ou-Mandel interferometer where atom tunneling plays the role of the photon beamsplitter. The interferometer is used to probe the effect of atomic indistinguishability on the two-atom dynamics for a variety of initial conditions. These experiments demonstrate the viability of the optical tweezer platform for bottom-up generation of low-entropy quantum systems and pave the way toward the direct observation of quantum dynamics in more complex finite-sized systems.

  4. RBCs under optical tweezers as cellular motors and rockers: microfluidic applications

    NASA Astrophysics Data System (ADS)

    Mohanty, Samarendra; Mohanty, Khyati; Gupta, Pradeep

    2006-08-01

    Recently, we have reported self-rotation of normal red blood cells (RBC), suspended in hypertonic buffer, and trapped in unpolarized laser tweezers. Here, we report use of such an optically driven RBC-motor for microfluidic applications such as pumping/centrifugation of fluids. Since the speed of rotation of the RBC-motor was found to vary with the power of the trapping beam, the flow rate could be controlled by controlling the laser power. In polarized optical tweezers, preferential alignment of trapped RBC was observed. The aligned RBC (simulating a disk) in isotonic buffer, could be rotated in a controlled manner for use as a microfluidic valve by rotation of the plane of polarization of the trapping beam. The thickness of the discotic RBC could be changed by changing the osmolarity of the solution and thus the alignment torque on the RBC due to the polarization of the trapping beam could be varied. Further, in polarized tweezers, the RBCs in hypertonic buffer showed rocking motion while being in rotation. Here, the RBC rotated over a finite angular range, stopped for some time at a particular angle, and then started rotating till it was back to the aligned position and this cycle was found repetitive. This can be attributed to the fact that though the RBCs were found to experience an alignment torque to align with plane of polarization of the tweezers due to its form birefringence, it was smaller in magnitude as compared to the rotational torque due to its structural asymmetry in hypertonic solution. Changes in the laser power caused a transition from/to rocking to/from motor behavior of the RBC in a linearly polarized tweezers. By changing the direction of polarization caused by rotation of an external half wave plate, the stopping angle of rocking could be changed. Further, RBCs suspended in intermediate hypertonic buffer and trapped with polarized tweezers showed fluttering about the vertical plane.

  5. Calibration of a dual-trap optical tweezers for single molecule force spectroscopy study

    NASA Astrophysics Data System (ADS)

    Wang, Guoqing; Hu, Chunguang; Gao, Xiaoqing; Su, Chenguang; Wang, Sirong; Lei, Hai; Hu, Xiaodong; Li, Hongbin; Hu, Xiaotang

    2015-10-01

    Optical tweezers has shown its significant advantages in applying pico-Newton force on micro beads and handling them with nanometer-level precision, and becomes a powerful tool for single-molecule biology. Many excellent researching results in use of the optical tweezers have been reported. Most of them focus on the single-trap optical tweezers experiments. However, when a single-trap optical tweezers is applied to biological molecule, there is often an obvious noise from the sample chamber holder to which one end of the sample molecule is tethered. In contrast, a dual-trap optical tweezers can intrinsically avoid this problem because both ends of the sample tethered to microspheres are manipulated with two separate optical traps. In order to force the molecule precisely, it is of importance to do calibrations for both traps. Many approaches have been studied to obtain the stiffness and sensitivity of the trap, but those are not quite suitable for making calibration during experiment. Here, we use a modified method of power spectrum density (PSD) for the calibrations of the stiffness and sensitivity of the traps, which combines a sinusoidal motion of the sample stage. The main strength of the method is that the beads used for the calibration also can be used in experiment later. In addition, the calibration can be performed during experiment. Finally, an experiment using a dsDNA molecule to test the system is presented. The results show that the calibration approach for the dual-trap optical tweezers is efficient and accurate.

  6. Manipulating multiparticles simultaneously with tapered-tip single fiber optical tweezers

    NASA Astrophysics Data System (ADS)

    Zhang, Yu; Wu, Zhongfu; Liu, Zhihai; Yang, Jun; Yuan, Libo

    2008-12-01

    We present a single-core tapered-tip single fiber optical tweezers, which can trap multi-particle simultaneously. In order to test and verify its new function, finite difference time domain (FDTD) method is used to calculate and simulate. The relationship between the trapping force and the particle-parameters, such as the size, refractive index and others of particle are studied. By experimental validation, the tapered-tip single optic fiber tweezers can trap Particle 2nd after the Particle 1st trapped firmly, but can not trap Particle 3rd, which just verifies the theoretical simulation results to be right.

  7. On-site manipulation of single whole-genome DNA molecules using optical tweezers

    NASA Astrophysics Data System (ADS)

    Oana, Hidehiro; Kubo, Koji; Yoshikawa, Kenichi; Atomi, Haruyuki; Imanaka, Tadayuki

    2004-11-01

    In this letter, we describe a noninvasive methodology for manipulating single Mb-size whole-genome DNA molecules. Cells were subjected to osmotic shock and the genome DNA released from the burst cells was transferred to a region of higher salt concentration using optical tweezers. The transferred genome DNA exhibits a conformational transition from a compact state into an elongated state, accompanied by the change in its environment. The applicability of optical tweezers to the on-site manipulation of giant genome DNA is suggested, i.e., lab-on-a-plate.

  8. Mechanical and electrical properties of red blood cells using optical tweezers

    NASA Astrophysics Data System (ADS)

    Fontes, A.; Barjas Castro, M. L.; Brandão, M. M.; Fernandes, H. P.; Thomaz, A. A.; Huruta, R. R.; Pozzo, L. Y.; Barbosa, L. C.; Costa, F. F.; Saad, S. T. O.; Cesar, C. L.

    2011-04-01

    Optical tweezers are a very sensitive tool, based on photon momentum transfer, for individual, cell by cell, manipulation and measurements, which can be applied to obtain important properties of erythrocytes for clinical and research purposes. Mechanical and electrical properties of erythrocytes are critical parameters for stored cells in transfusion centers, immunohematological tests performed in transfusional routines and in blood diseases. In this work, we showed methods, based on optical tweezers, to study red blood cells and applied them to measure apparent overall elasticity, apparent membrane viscosity, zeta potential, thickness of the double layer of electrical charges and adhesion in red blood cells.

  9. Near-field enhanced optical tweezers utilizing femtosecond-laser nanostructured substrates

    SciTech Connect

    Kotsifaki, D. G. Kandyla, M.; Lagoudakis, P. G.

    2015-11-23

    We present experimental evidence of plasmonic-enhanced optical tweezers, of polystyrene beads in deionized water in the vicinity of metal-coated nanostructures. The optical tweezers operate with a continuous wave near-infrared laser. We employ a Cu/Au bilayer that significantly improves dissipation of heat generated by the trapping laser beam and avoid de-trapping from heat convection currents. We investigate the improvement of the optical trapping force and the effective trapping quality factor, and observe an exponential distance dependence of the trapping force from the nanostructures, indicative of evanescent plasmonic enhancement.

  10. Raman tweezers on bacteria: following the mechanisms of bacteriostatic versus bactericidal action

    NASA Astrophysics Data System (ADS)

    Bernatova, Silvie; Samek, Ota; Pilat, Zdenek; Sery, Mojmir; Jezek, Jan; Jakl, Petr; Siler, Martin; Krzyzanek, Vladislav; Zemanek, Pavel; Hola, Veronika; Dvorackova, Milada; Ruzicka, Filip

    2014-05-01

    Raman tweezers represents a unique method for identification of different microorganisms on the basis of Raman scattering. Raman tweezers allows us to fix and sterile manipulate with the trapped object and in the same time check the growth, viability, response to the external environment etc. by Raman signal evaluating. The investigations presented here include distinction of bacteria in general (staphylococcal cells), identification of bacteria strains (biofilm-positive and biofilm-negative) by using principal component analysis (PCA) and monitoring the influence of antibiotics.

  11. Shape deformations of giant unilamellar vesicles with a laser tweezer array

    NASA Astrophysics Data System (ADS)

    Losert, Wolfgang; Poole, Cory; Bradford, Peter; English, Doug

    2004-10-01

    Vesicles are phospholipid bilayers that form a surface enclosing a volume of water or solution. They are of importance as model systems to study cells, as well as having practical applications such as containers for performing nanochemistry and facilitating drug delivery. Their properties have been studied for decades. Using a holographic laser tweezer array (LTA), which converts a single laser beam into many laser tweezer points, we stretch the vesicles in controlled ways from several points at once, measuring each force applied. Here, we present data on shape deformations of simple, spherical vesicles and on membrane fracture.

  12. Two-particle quantum interference in tunnel-coupled optical tweezers.

    PubMed

    Kaufman, A M; Lester, B J; Reynolds, C M; Wall, M L; Foss-Feig, M; Hazzard, K R A; Rey, A M; Regal, C A

    2014-07-18

    The quantum statistics of atoms is typically observed in the behavior of an ensemble via macroscopic observables. However, quantum statistics modifies the behavior of even two particles. Here, we demonstrate near-complete control over all the internal and external degrees of freedom of two laser-cooled (87)Rb atoms trapped in two optical tweezers. This controllability allows us to observe signatures of indistinguishability via two-particle interference. Our work establishes laser-cooled atoms in optical tweezers as a promising route to bottom-up engineering of scalable, low-entropy quantum systems.

  13. Dynamics of multiple trapping by a single-beam laser tweezer.

    PubMed

    Kaputa, Daniel S; Kuzmin, Andrey N; Kachynski, Aliaksandr V; Cartwright, Alexander N; Prasad, Paras N

    2005-07-01

    A multiple-trap single-beam scanning laser tweezer system was developed and characterized. Different stationary and mobile multiple-trap modes were generated for polystyrene beads in a water environment. Trapping efficiency and stability were investigated for several dynamic parameters such as transition time between the sites, waiting time on a single site, number of trapping sites, and IR laser power. Optimal parameters for efficient generation of complex arrays and matrices were determined. We demonstrate an example of a single laser beam multiple-trap application by measuring the trap's stiffness in water for our laser tweezer setup.

  14. Substrate-dependent cell elasticity measured by optical tweezers indentation

    NASA Astrophysics Data System (ADS)

    Yousafzai, Muhammad S.; Ndoye, Fatou; Coceano, Giovanna; Niemela, Joseph; Bonin, Serena; Scoles, Giacinto; Cojoc, Dan

    2016-01-01

    In the last decade, cell elasticity has been widely investigated as a potential label free indicator for cellular alteration in different diseases, cancer included. Cell elasticity can be locally measured by pulling membrane tethers, stretching or indenting the cell using optical tweezers. In this paper, we propose a simple approach to perform cell indentation at pN forces by axially moving the cell against a trapped microbead. The elastic modulus is calculated using the Hertz-model. Besides the axial component, the setup also allows us to examine the lateral cell-bead interaction. This technique has been applied to measure the local elasticity of HBL-100 cells, an immortalized human cell line, originally derived from the milk of a woman with no evidence of breast cancer lesions. In addition, we have studied the influence of substrate stiffness on cell elasticity by performing experiments on cells cultured on two substrates, bare and collagen-coated, having different stiffness. The mean value of the cell elastic modulus measured during indentation was 26±9 Pa for the bare substrate, while for the collagen-coated substrate it diminished to 19±7 Pa. The same trend was obtained for the elastic modulus measured during the retraction of the cell: 23±10 Pa and 13±7 Pa, respectively. These results show the cells adapt their stiffness to that of the substrate and demonstrate the potential of this setup for low-force probing of modifications to cell mechanics induced by the surrounding environment (e.g. extracellular matrix or other cells).

  15. Mechanical properties of stored red blood cells using optical tweezers

    NASA Astrophysics Data System (ADS)

    Fontes, Adriana; Alexandre de Thomaz, Andre; de Ysasa Pozzo, Liliana; de Lourdes Barjas-Castro, Maria; Brandao, Marcelo M.; Saad, Sara T. O.; Barbosa, Luiz Carlos; Cesar, Carlos Lenz

    2005-08-01

    We have developed a method for measuring the red blood cell (RBC) membrane overall elasticity μ by measuring the deformation of the cells when dragged at a constant velocity through a plasma fluid by an optical tweezers. The deformability of erythrocytes is a critical determinant of blood flow in the microcirculation. We tested our method and hydrodynamic models, which included the presence of two walls, by measuring the RBC deformation as a function of drag velocity and of the distance to the walls. The capability and sensitivity of this method can be evaluated by its application to a variety of studies, such as, the measurement of RBC elasticity of sickle cell anemia patients comparing homozygous (HbSS), including patients taking hydroxyrea (HU) and heterozygous (HbAS) with normal donors and the RBC elasticity measurement of gamma irradiated stored blood for transfusion to immunosupressed patients as a function of time and dose. These studies show that the technique has the sensitivity to discriminate heterozygous and homozygous sickle cell anemia patients from normal donors and even follow the course of HU treatment of Homozygous patients. The gamma irradiation studies show that there is no significant change in RBC elasticity over time for up to 14 days of storage, regardless of whether the unit was irradiated or not, but there was a huge change in the measured elasticity for the RBC units stored for more than 21 days after irradiation. These finds are important for the assessment of stored irradiated RBC viability for transfusion purposes because the present protocol consider 28 storage days after irradiation as the limit for the RBC usage.

  16. Dynamic properties of bacterial pili measured by optical tweezers

    NASA Astrophysics Data System (ADS)

    Fallman, Erik G.; Andersson, Magnus J.; Schedin, Staffan S.; Jass, Jana; Uhlin, Bernt Eric; Axner, Ove

    2004-10-01

    The ability of uropathogenic Escherichia coli (UPEC) to cause urinary tract infections is dependent on their ability to colonize the uroepithelium. Infecting bacteria ascend the urethra to the bladder and then kidneys by attaching to the uroepithelial cells via the differential expression of adhesins. P pili are associated with pyelonephritis, the more severe infection of the kidneys. In order to find means to treat pyelonephritis, it is therefore of interest to investigate the properties P pili. The mechanical behavior of individual P pili of uropathogenic Escherichia coli has recently been investigated using optical tweezers. P pili, whose main part constitutes the PapA rod, composed of ~1000 PapA subunits in a helical arrangement, are distributed over the bacterial surface and mediate adhesion to host cells. We have earlier studied P pili regarding its stretching/elongation properties where we have found and characterized three different elongation regions, of which one constitute an unfolding of the quaternary (helical) structure of the PapA rod. It was shown that this unfolding takes place at an elongation independent force of 27 +/- 2 pN. We have also recently performed studies on its folding properties and shown that the unfolding/folding of the PapA rod is completely reversible. Here we present a study of the dynamical properties of the PapA rod. We show, among other things, that the unfolding force increases and that the folding force decreases with the speed of unfolding and folding respectively. Moreover, the PapA rod can be folded-unfolded a significant number of times without loosing its characteristics, a phenomenon that is believed to be important for the bacterium to keep close contact to the host tissue and consequently helps the bacterium to colonize the host tissue.

  17. RBC aggregation dynamics in autologous plasma and serum studied with double-channel optical tweezers

    NASA Astrophysics Data System (ADS)

    Lee, Kisung; Danilina, Anna; Potkin, Anton; Kinnunen, Matti; Priezzhev, Alexander; Meglinski, Igor

    2016-04-01

    Red blood cells aggregating and disaggregating forces were measured in the autologous plasma and serum using the double-channeled optical tweezers. A significant, three-fold decrease of the both forces was observed in the serum compared to the plasma. The results of this study help to better assess the RBC aggregation mechanism.

  18. Research Advances: Nanoscale Molecular Tweezers; Cinnamon as Pesticide?; Recently Identified Dietary Sources of Antioxidants

    NASA Astrophysics Data System (ADS)

    King, Angela G.

    2004-12-01

    This Report from Other Journals surveys articles of interest to chemists that have been recently published in other science journals. Topics surveyed include reports that receptors have been designed to act as molecular tweezers; cinnamon has potential in the fight against mosquitoes; and high levels of antioxidants are found in some surprising foods. See Featured Molecules .

  19. Actin and myosin regulate cytoplasm stiffness in plant cells: a study using optical tweezers.

    PubMed

    van der Honing, Hannie S; de Ruijter, Norbert C A; Emons, Anne Mie C; Ketelaar, Tijs

    2010-01-01

    Here, we produced cytoplasmic protrusions with optical tweezers in mature BY-2 suspension cultured cells to study the parameters involved in the movement of actin filaments during changes in cytoplasmic organization and to determine whether stiffness is an actin-related property of plant cytoplasm. Optical tweezers were used to create cytoplasmic protrusions resembling cytoplasmic strands. Simultaneously, the behavior of the actin cytoskeleton was imaged. After actin filament depolymerization, less force was needed to create cytoplasmic protrusions. During treatment with the myosin ATPase inhibitor 2,3-butanedione monoxime, more trapping force was needed to create and maintain cytoplasmic protrusions. Thus, the presence of actin filaments and, even more so, the deactivation of a 2,3-butanedione monoxime-sensitive factor, probably myosin, stiffens the cytoplasm. During 2,3-butanedione monoxime treatment, none of the tweezer-formed protrusions contained filamentous actin, showing that a 2,3-butanedione monoxime-sensitive factor, probably myosin, is responsible for the movement of actin filaments, and implying that myosin serves as a static cross-linker of actin filaments when its motor function is inhibited. The presence of actin filaments does not delay the collapse of cytoplasmic protrusions after tweezer release. Myosin-based reorganization of the existing actin cytoskeleton could be the basis for new cytoplasmic strand formation, and thus the production of an organized cytoarchitecture.

  20. Molecular tweezers modulate 14-3-3 protein-protein interactions.

    PubMed

    Bier, David; Rose, Rolf; Bravo-Rodriguez, Kenny; Bartel, Maria; Ramirez-Anguita, Juan Manuel; Dutt, Som; Wilch, Constanze; Klärner, Frank-Gerrit; Sanchez-Garcia, Elsa; Schrader, Thomas; Ottmann, Christian

    2013-03-01

    Supramolecular chemistry has recently emerged as a promising way to modulate protein functions, but devising molecules that will interact with a protein in the desired manner is difficult as many competing interactions exist in a biological environment (with solvents, salts or different sites for the target biomolecule). We now show that lysine-specific molecular tweezers bind to a 14-3-3 adapter protein and modulate its interaction with partner proteins. The tweezers inhibit binding between the 14-3-3 protein and two partner proteins--a phosphorylated (C-Raf) protein and an unphosphorylated one (ExoS)--in a concentration-dependent manner. Protein crystallography shows that this effect arises from the binding of the tweezers to a single surface-exposed lysine (Lys214) of the 14-3-3 protein in the proximity of its central channel, which normally binds the partner proteins. A combination of structural analysis and computer simulations provides rules for the tweezers' binding preferences, thus allowing us to predict their influence on this type of protein-protein interactions. PMID:23422566

  1. Red blood cell micromanipulation with elliptical laser beam profile optical tweezers in different osmolarity conditions

    NASA Astrophysics Data System (ADS)

    Spyratou, E.; Makropoulou, M.; Serafetinides, A. A.

    2011-07-01

    In this work optical tweezers with elliptical beam profiles have been developed in order to examine the effect of optical force on fresh red blood cells (RBC) in isotonic, hypertonic and hypotonic buffer solutions. Considering that the optical force depends essentially on the cell surface and the cytoplasmic refractive index, it is obvious that biochemical modifications associated with different states of the cell will influence its behaviour in the optical trap. Line optical tweezers were used to manipulate simultaneously more than one red blood cell. After we have been manipulated a RBC with an elliptical laser beam profile in an isotonic or hypertonic buffer, we noticed that it rotates by itself when gets trapped by optical tweezers and undergoes folding. Further shape deformations can be observed attributed to the competition between alignment and rotational torque which are transferred by laser light to the cell. In hypotonic buffer RBCs become spherical and do not rotate or fold since the resultant force due to rays emerging from diametrically opposite points of the cell leads to zero torque. Manipulation of fresh red blood cells in isotonic solution by line optical tweezers leads to folding and elongation of trapped RBCs. Membrane elasticity properties such as bending modulus can be estimated by measuring RBC's folding time in function with laser power.

  2. Hands-on with optical tweezers: a multitouch interface for holographic optical trapping.

    PubMed

    Grieve, J A; Ulcinas, A; Subramanian, S; Gibson, G M; Padgett, M J; Carberry, D M; Miles, M J

    2009-03-01

    We report the implementation of a multitouch console for control of a holographic optical tweezers system. This innovative interface enables the independent but simultaneous interactive control of numerous optical traps by multiple users, overcoming the limitations of traditional interfaces and placing the full power of holographic optical tweezing into the operators' hands.

  3. Adhesion of nanoparticles to polymer brushes studied with the ghost tweezers method.

    PubMed

    Cheng, Jianli; Vishnyakov, Aleksey; Neimark, Alexander V

    2015-01-21

    Mechanisms of interactions between nanoparticles (NPs) and polymer brushes (PBs) are explored using dissipative particle dynamics simulations and an original "ghost tweezers" method that emulates lab experiments performed with optical or magnetic tweezers. The ghost tweezers method is employed to calculate the free energy of adhesion. Ghost tweezers represents a virtual harmonic potential, which tethers NP with a spring to a given anchor point. The average spring force represents the effective force of NP-PB interaction as a function of the NP coordinate. The free energy landscape of NP-PB interactions is calculated as the mechanical work needed to transfer NP from the solvent bulk to a particular distance from the substrate surface. With this technique, we explore the adhesion of bare and ligand-functionalized spherical NPs to polyisoprene natural rubber brush in acetone-benzene binary solvent. We examine two basic mechanisms of NP-PB interactions, NP adhesion at PB exterior and NP immersion into PB, which are governed by interplay between entropic repulsive forces and enthalpic attractive forces caused by polymer adsorption at the NP surface and ligand adsorption at the substrate. The relative free energies of the equilibrium adhesion states and the potential barriers separating these states are calculated at varying grafting density, NP size, and solvent composition. PMID:25612723

  4. Development of high frequency focused transducers for single beam acoustic tweezers

    NASA Astrophysics Data System (ADS)

    Hsu, Hsiu-Sheng

    Contactless particle trapping and manipulation have found many potential applications in diverse fields, especially in biological and medical research. Among the various methods, optical tweezers is the most well-known and extensively investigated technique. However, there are some limitations for particle manipulation based on optical tweezers. Due to the conceptual similarity with the optical tweezers and recent advances in high frequency ultrasonic transducer, a single beam acoustic tweezer using high frequency (≥ 20 MHz) focused transducer has recently been considered, and its feasibility was theoretically and experimentally investigated. This dissertation mainly describes the development of high frequency focused ultrasonic transducers for single beam acoustic tweezers applications. Three different types of transducers were fabricated. First, a 60 MHz miniature focused transducer (<1 mm) was made using press-focusing technique. The single beam acoustic trapping experiment was performed to manipulate 15 microm polystyrene microspheres using this transducer. In vitro ultrasonic biomicroscopy imaging on the rabbit eye was also obtained with this device. Second approach is to build a 200 MHz self-focused ZnO transducer by sputtering ZnO film on a curved surface of the aluminum backing material. An individual 10 microm microsphere was effectively manipulated in two dimensions by this type of transducer. Another ultrahigh frequency focused transducer based on silicon lens design has also been developed, where a 330 MHz silicon lens transducer was fabricated and evaluated. Microparticle trapping experiment was carried out to demonstrate that silicon lens transducer can manipulate a single microsphere as small as 5 microm. The realization of single beam acoustic tweezers using high frequency focused transducers can offer wide range of applications in biomedical and chemical sciences including intercellular kinetics studies and cell stimulation. Additionally, we

  5. Oscillating optical tweezer-based 3-D confocal microrheometer for investigating the intracellular micromechanics and structures

    NASA Astrophysics Data System (ADS)

    Ou-Yang, H. D.; Rickter, E. A.; Pu, C.; Latinovic, O.; Kumar, A.; Mengistu, M.; Lowe-Krentz, L.; Chien, S.

    2005-08-01

    Mechanical properties of living biological cells are important for cells to maintain their shapes, support mechanical stresses and move through tissue matrix. The use of optical tweezers to measure micromechanical properties of cells has recently made significant progresses. This paper presents a new approach, the oscillating optical tweezer cytorheometer (OOTC), which takes advantage of the coherent detection of harmonically modulated particle motions by a lock-in amplifier to increase sensitivity, temporal resolution and simplicity. We demonstrate that OOTC can measure the dynamic mechanical modulus in the frequency range of 0.1-6,000 Hz at a rate as fast as 1 data point per second with submicron spatial resolution. More importantly, OOTC is capable of distinguishing the intrinsic non-random temporal variations from random fluctuations due to Brownian motion; this capability, not achievable by conventional approaches, is particular useful because living systems are highly dynamic and often exhibit non-thermal, rhythmic behavior in a broad time scale from a fraction of a second to hours or days. Although OOTC is effective in measuring the intracellular micromechanical properties, unless we can visualize the cytoskeleton in situ, the mechanical property data would only be as informative as that of "Blind men and the Elephant". To solve this problem, we take two steps, the first, to use of fluorescent imaging to identify the granular structures trapped by optical tweezers, and second, to integrate OOTC with 3-D confocal microscopy so we can take simultaneous, in situ measurements of the micromechanics and intracellular structure in living cells. In this paper, we discuss examples of applying the oscillating tweezer-based cytorheometer for investigating cultured bovine endothelial cells, the identification of caveolae as some of the granular structures in the cell as well as our approach to integrate optical tweezers with a spinning disk confocal microscope.

  6. Fullerene recognition with molecular tweezers made up of efficient buckybowls: a dispersion-corrected DFT study.

    PubMed

    Josa, Daniela; Rodríguez-Otero, Jesús; Cabaleiro-Lago, Enrique M

    2015-05-28

    In 2007, Sygula and co-workers introduced a novel type of molecular tweezers with buckybowl pincers that have attracted the substantial interest of researchers due to their ideal architecture for recognizing fullerenes by concave-convex π∙∙∙π interactions (A. Sygula et al., J. Am. Chem. Soc., 2007, 129, 3842). Although in recent years some modifications have been performed on these original molecular tweezers to improve their ability for catching fullerenes, very few improvements were achieved to date. For that reason, in the present work a series of molecular tweezers have been devised and their supramolecular complexes with C60 studied at the B97-D2/TZVP//SCC-DFTB-D and B97-D2/TZVP levels. Three different strategies have been tested: (1) changing the corannulene pincers to other buckybowls, (2) replacing the tetrabenzocyclooctatetraene tether by a buckybowl, and (3) adding methyl groups on the molecular tweezers. According to the results, all the three approaches are effective, in such a way that a combination of the three strategies results in buckycatchers with complexation energies (with C60) up to 2.6 times larger than that of the original buckycatcher, reaching almost -100 kcal mol(-1). The B97-D2/TZVP//SCC-DFTB-D approach can be a rapid screening tool for testing new molecular tweezers. However, since this approach does not reproduce correctly the deformation energy and this energy represents an important contribution to the total complexation energy of complexes, subsequent higher-level re-optimization is compulsory to achieve reliable results (the full B97-D2/TZVP level is used herein). This re-optimization could be superfluous when quite rigid buckycatchers are studied.

  7. The supramolecular design of low-dimensional carbon nano-hybrids encoding a polyoxometalate-bis-pyrene tweezer.

    PubMed

    Modugno, Gloria; Syrgiannis, Zois; Bonasera, Aurelio; Carraro, Mauro; Giancane, Gabriele; Valli, Ludovico; Bonchio, Marcella; Prato, Maurizio

    2014-05-18

    A novel bis-pyrene tweezer anchored on a rigid polyoxometalate scaffold fosters a unique interplay of hydrophobic and electrostatic supramolecular interactions, to shape carbon nanostructures (CNSs)-based extended architectures.

  8. Study of the Line Optical Tweezers Characteristics Using a Novel Method and Establishing a Model for Cell Sorting

    NASA Astrophysics Data System (ADS)

    Lin, Ho-Chien; Hsu, Long

    2009-07-01

    Optical tweezers have become a powerful tool in cellular and molecule biology. Line optical tweezers enhanced its function in cell sorting. This study presents the line trap model, based on the ray-optics model, and demonstrates its accuracy for the line optical tweezers. The line optical tweezers system is established to produce the optical intensity distribution of a line pattern and to trap the micro-sized beads. The main parameter, optical intensity distribution, is used to calculate the trapping force distribution in the model. The two forces, trapping force and water dragging force, and the equation of motion is used to simulate the trajectory of micro-sized beads as they pass through the line pattern in flowing water in the microchannel. The trajectory is analyzed to determine the effective separation distance between the micro-sized beads or cells. The method will be applied in biological and medical detection.

  9. Neural Network for Image-to-Image Control of Optical Tweezers

    NASA Technical Reports Server (NTRS)

    Decker, Arthur J.; Anderson, Robert C.; Weiland, Kenneth E.; Wrbanek, Susan Y.

    2004-01-01

    A method is discussed for using neural networks to control optical tweezers. Neural-net outputs are combined with scaling and tiling to generate 480 by 480-pixel control patterns for a spatial light modulator (SLM). The SLM can be combined in various ways with a microscope to create movable tweezers traps with controllable profiles. The neural nets are intended to respond to scattered light from carbon and silicon carbide nanotube sensors. The nanotube sensors are to be held by the traps for manipulation and calibration. Scaling and tiling allow the 100 by 100-pixel maximum resolution of the neural-net software to be applied in stages to exploit the full 480 by 480-pixel resolution of the SLM. One of these stages is intended to create sensitive null detectors for detecting variations in the scattered light from the nanotube sensors.

  10. Probing the structural dynamics of proteins and nucleic acids with optical tweezers.

    PubMed

    Ritchie, Dustin B; Woodside, Michael T

    2015-10-01

    Conformational changes are an essential feature of most molecular processes in biology. Optical tweezers have emerged as a powerful tool for probing conformational dynamics at the single-molecule level because of their high resolution and sensitivity, opening new windows on phenomena ranging from folding and ligand binding to enzyme function, molecular machines, and protein aggregation. By measuring conformational changes induced in a molecule by forces applied by optical tweezers, new insight has been gained into the relationship between dynamics and function. We discuss recent advances from studies of how structure forms in proteins and RNA, including non-native structures, fluctuations in disordered proteins, and interactions with chaperones assisting native folding. We also review the development of assays probing the dynamics of complex protein-nucleic acid and protein-protein assemblies that reveal the dynamic interactions between biomolecular machines and their substrates.

  11. Membrane tether formation from voltage-clamped outer hair cells using optical tweezers

    NASA Astrophysics Data System (ADS)

    Qian, Feng; Ermilov, Sergey A.; Murdock, David R.; Brownell, William E.; Anvari, Bahman

    2004-06-01

    Outer hair cells contribute an active mechanical feedback to the vibrations of the cochlear structures resulting in the high sensitivity and frequency selectivity of normal hearing. We have designed and implemented a novel experimental setup that combines optical tweezers with patch-clamp apparatus to investigate the electromechanical properties of cellular plasma membranes. A micron-size bead trapped by the optical tweezers is brought in contact with the membrane of a voltage-clamped cell, and subsequently moved away to form a plasma membrane tether. Bead displacement during tether elongation is monitored by a quadrant photodetector to obtain time-resolved measurements of the tethering force. Salient information associated with the mechanical properties of the membrane tether can thus be obtained. Tethers can be pulled from the cell membrane at different holding potentials, and the tether force response can be measured while changing transmembrane potential. Experimental results from outer hair cells and human embryonic kidney cells are presented.

  12. An Improved Optical Tweezers Assay for Measuring the Force Generation of Single Kinesin Molecules

    PubMed Central

    Nicholas, Matthew P.; Rao, Lu; Gennerich, Arne

    2014-01-01

    Numerous microtubule-associated molecular motors, including several kinesins and cytoplasmic dynein, produce opposing forces that regulate spindle and chromosome positioning during mitosis. The motility and force generation of these motors are therefore critical to normal cell division, and dysfunction of these processes may contribute to human disease. Optical tweezers provide a powerful method for studying the nanometer motility and piconewton force generation of single motor proteins in vitro. Using kinesin-1 as a prototype, we present a set of step-by-step, optimized protocols for expressing a kinesin construct (K560-GFP) in Escherichia coli, purifying it, and studying its force generation in an optical tweezers microscope. We also provide detailed instructions on proper alignment and calibration of an optical trapping microscope. These methods provide a foundation for a variety of similar experiments. PMID:24633799

  13. Identification of individual biofilm-forming bacterial cells using Raman tweezers

    NASA Astrophysics Data System (ADS)

    Samek, Ota; Bernatová, Silvie; Ježek, Jan; Šiler, Martin; Šerý, Mojmir; Krzyžánek, Vladislav; Hrubanová, Kamila; Zemánek, Pavel; Holá, Veronika; Růžička, Filip

    2015-05-01

    A method for in vitro identification of individual bacterial cells is presented. The method is based on a combination of optical tweezers for spatial trapping of individual bacterial cells and Raman microspectroscopy for acquisition of spectral "Raman fingerprints" obtained from the trapped cell. Here, Raman spectra were taken from the biofilm-forming cells without the influence of an extracellular matrix and were compared with biofilm-negative cells. Results of principal component analyses of Raman spectra enabled us to distinguish between the two strains of Staphylococcus epidermidis. Thus, we propose that Raman tweezers can become the technique of choice for a clearer understanding of the processes involved in bacterial biofilms which constitute a highly privileged way of life for bacteria, protected from the external environment.

  14. Raman sorting and identification of single living micro-organisms with optical tweezers

    NASA Astrophysics Data System (ADS)

    Xie, Changan; Chen, De; Li, Yong-Qing

    2005-07-01

    We report on a novel technique for sorting and identification of single biological cells and food-borne bacteria based on laser tweezers and Raman spectroscopy (LTRS). With this technique, biological cells of different physiological states in a sample chamber were identified by their Raman spectral signatures and then they were selectively manipulated into a clean collection chamber with optical tweezers through a microchannel. As an example, we sorted the live and dead yeast cells into the collection chamber and validated this with a standard staining technique. We also demonstrated that bacteria existing in spoiled foods could be discriminated from a variety of food particles based on their characteristic Raman spectra and then isolated with laser manipulation. This label-free LTRS sorting technique may find broad applications in microbiology and rapid examination of food-borne diseases.

  15. In Vivo Quantification of Peroxisome Tethering to Chloroplasts in Tobacco Epidermal Cells Using Optical Tweezers.

    PubMed

    Gao, Hongbo; Metz, Jeremy; Teanby, Nick A; Ward, Andy D; Botchway, Stanley W; Coles, Benjamin; Pollard, Mark R; Sparkes, Imogen

    2016-01-01

    Peroxisomes are highly motile organelles that display a range of motions within a short time frame. In static snapshots, they can be juxtaposed to chloroplasts, which has led to the hypothesis that they are physically interacting. Here, using optical tweezers, we tested the dynamic physical interaction in vivo. Using near-infrared optical tweezers combined with TIRF microscopy, we were able to trap peroxisomes and approximate the forces involved in chloroplast association in vivo in tobacco (Nicotiana tabacum) and observed weaker tethering to additional unknown structures within the cell. We show that chloroplasts and peroxisomes are physically tethered through peroxules, a poorly described structure in plant cells. We suggest that peroxules have a novel role in maintaining peroxisome-organelle interactions in the dynamic environment. This could be important for fatty acid mobilization and photorespiration through the interaction with oil bodies and chloroplasts, highlighting a fundamentally important role for organelle interactions for essential biochemistry and physiological processes.

  16. Multiple Optical Traps with a Single-Beam Optical Tweezer Utilizing Surface Micromachined Planar Curved Grating

    NASA Astrophysics Data System (ADS)

    Kuo, Ju-Nan; Chen, Kuan-Yu

    2010-11-01

    In this paper, we present a single-beam optical tweezer integrated with a planar curved diffraction grating for microbead manipulation. Various curvatures of the surface micromachined planar curved grating are systematically investigated. The planar curved grating was fabricated using multiuser micro-electro-mechanical-system (MEMS) processes (MUMPs). The angular separation and the number of diffracted orders were determined. Experimental results indicate that the diffraction patterns and curvature of the planar curved grating are closely related. As the curvature of the planar curved grating increases, the vertical diffraction angle increases, resulting in the strip patterns of the planar curved grating. A single-beam optical tweezer integrated with a planar curved diffraction grating was developed. We demonstrate a technique for creating multiple optical traps from a single laser beam using the developed planar curved grating. The strip patterns of the planar curved grating that resulted from diffraction were used to trap one row of polystyrene beads.

  17. In Vivo Quantification of Peroxisome Tethering to Chloroplasts in Tobacco Epidermal Cells Using Optical Tweezers.

    PubMed

    Gao, Hongbo; Metz, Jeremy; Teanby, Nick A; Ward, Andy D; Botchway, Stanley W; Coles, Benjamin; Pollard, Mark R; Sparkes, Imogen

    2016-01-01

    Peroxisomes are highly motile organelles that display a range of motions within a short time frame. In static snapshots, they can be juxtaposed to chloroplasts, which has led to the hypothesis that they are physically interacting. Here, using optical tweezers, we tested the dynamic physical interaction in vivo. Using near-infrared optical tweezers combined with TIRF microscopy, we were able to trap peroxisomes and approximate the forces involved in chloroplast association in vivo in tobacco (Nicotiana tabacum) and observed weaker tethering to additional unknown structures within the cell. We show that chloroplasts and peroxisomes are physically tethered through peroxules, a poorly described structure in plant cells. We suggest that peroxules have a novel role in maintaining peroxisome-organelle interactions in the dynamic environment. This could be important for fatty acid mobilization and photorespiration through the interaction with oil bodies and chloroplasts, highlighting a fundamentally important role for organelle interactions for essential biochemistry and physiological processes. PMID:26518344

  18. Identification of individual biofilm-forming bacterial cells using Raman tweezers.

    PubMed

    Samek, Ota; Bernatová, Silvie; Ježek, Jan; Šiler, Martin; Šerý, Mojmir; Krzyžánek, Vladislav; Hrubanová, Kamila; Zemánek, Pavel; Holá, Veronika; Růžička, Filip

    2015-05-01

    A method for in vitro identification of individual bacterial cells is presented. The method is based on a combination of optical tweezers for spatial trapping of individual bacterial cells and Raman microspectroscopy for acquisition of spectral “Raman fingerprints” obtained from the trapped cell. Here, Raman spectra were taken from the biofilm-forming cells without the influence of an extracellular matrix and were compared with biofilm-negative cells. Results of principal component analyses of Raman spectra enabled us to distinguish between the two strains of Staphylococcus epidermidis. Thus, we propose that Raman tweezers can become the technique of choice for a clearer understanding of the processes involved in bacterial biofilms which constitute a highly privileged way of life for bacteria, protected from the external environment.

  19. Optical tweezers and surface plasmon resonance combination system based on the high numerical aperture lens

    NASA Astrophysics Data System (ADS)

    Shan, Xuchen; Zhang, Bei; Lan, Guoqiang; Wang, Yiqiao; Liu, Shugang

    2015-11-01

    Biology and medicine sample measurement takes an important role in the microscopic optical technology. Optical tweezer has the advantage of accurate capture and non-pollution of the sample. The SPR(surface plasmon resonance) sensor has so many advantages include high sensitivity, fast measurement, less consumption of sample and label-free detection of biological sample that the SPR sensing technique has been used for surface topography, analysis of biochemical and immune, drug screening and environmental monitoring. If they combine, they will play an important role in the biological, chemical and other subjects. The system we propose use the multi-axis cage system, by using the methods of reflection and transmiss ion to improve the space utilization. The SPR system and optical tweezer were builtup and combined in one system. The cage of multi-axis system gives full play to its accuracy, simplicity and flexibility. The size of the system is 20 * 15 * 40 cm3 and thus the sample can be replaced to switch between the optical tweezers system and the SPR system in the small space. It means that we get the refractive index of the sample and control the particle in the same system. In order to control the revolving stage, get the picture and achieve the data stored automatically, we write a LabVIEW procedure. Then according to the data from the back focal plane calculate the refractive index of the sample. By changing the slide we can trap the particle as optical tweezer, which makes us measurement and trap the sample at the same time.

  20. Light-induced rotations of chiral birefringent microparticles in optical tweezers.

    PubMed

    Donato, M G; Mazzulla, A; Pagliusi, P; Magazzù, A; Hernandez, R J; Provenzano, C; Gucciardi, P G; Maragò, O M; Cipparrone, G

    2016-01-01

    We study the rotational dynamics of solid chiral and birefringent microparticles induced by elliptically polarized laser light in optical tweezers. We find that both reflection of left circularly polarized light and residual linear retardance affect the particle dynamics. The degree of ellipticity of laser light needed to induce rotations is found. The experimental results are compared with analytical calculations of the transfer of angular moment from elliptically polarized light to chiral birefringent particles. PMID:27601200

  1. A feasibility study of in vivo applications of single beam acoustic tweezers

    NASA Astrophysics Data System (ADS)

    Li, Ying; Lee, Changyang; Chen, Ruimin; Zhou, Qifa; Shung, K. Kirk

    2014-10-01

    Tools that are capable of manipulating micro-sized objects have been widely used in such fields as physics, chemistry, biology, and medicine. Several devices, including optical tweezers, atomic force microscope, micro-pipette aspirator, and standing surface wave type acoustic tweezers have been studied to satisfy this need. However, none of them has been demonstrated to be suitable for in vivo and clinical studies. Single beam acoustic tweezers (SBAT) is a technology that uses highly focused acoustic beam to trap particles toward the beam focus. Its feasibility was first theoretically and experimentally demonstrated by Lee and Shung several years ago. Since then, much effort has been devoted to improving this technology. At present, the tool is capable of trapping a microparticle as small as 1 μm, as well as a single red blood cell. Although in comparing to other microparticles manipulating technologies, SBAT has advantages of providing stronger trapping force and deeper penetration depth in tissues, and producing less tissue damage, its potential for in vivo applications has yet been explored. It is worth noting that ultrasound has been used as a diagnostic tool for over 50 years and no known major adverse effects have been observed at the diagnostic energy level. This paper reports the results of an initial attempt to assess the feasibility of single beam acoustic tweezers to trap microparticles in vivo inside of a blood vessel. The acoustic intensity of SBAT under the trapping conditions that were utilized was measured. The mechanical index and thermal index at the focus of acoustic beam were found to be 0.48 and 0.044, respectively, which meet the standard of commercial diagnostic ultrasound system.

  2. A feasibility study of in vivo applications of single beam acoustic tweezers

    SciTech Connect

    Li, Ying Lee, Changyang; Chen, Ruimin; Zhou, Qifa; Shung, K. Kirk

    2014-10-27

    Tools that are capable of manipulating micro-sized objects have been widely used in such fields as physics, chemistry, biology, and medicine. Several devices, including optical tweezers, atomic force microscope, micro-pipette aspirator, and standing surface wave type acoustic tweezers have been studied to satisfy this need. However, none of them has been demonstrated to be suitable for in vivo and clinical studies. Single beam acoustic tweezers (SBAT) is a technology that uses highly focused acoustic beam to trap particles toward the beam focus. Its feasibility was first theoretically and experimentally demonstrated by Lee and Shung several years ago. Since then, much effort has been devoted to improving this technology. At present, the tool is capable of trapping a microparticle as small as 1 μm, as well as a single red blood cell. Although in comparing to other microparticles manipulating technologies, SBAT has advantages of providing stronger trapping force and deeper penetration depth in tissues, and producing less tissue damage, its potential for in vivo applications has yet been explored. It is worth noting that ultrasound has been used as a diagnostic tool for over 50 years and no known major adverse effects have been observed at the diagnostic energy level. This paper reports the results of an initial attempt to assess the feasibility of single beam acoustic tweezers to trap microparticles in vivo inside of a blood vessel. The acoustic intensity of SBAT under the trapping conditions that were utilized was measured. The mechanical index and thermal index at the focus of acoustic beam were found to be 0.48 and 0.044, respectively, which meet the standard of commercial diagnostic ultrasound system.

  3. Rapid formation of size-controllable multicellular spheroids via 3D acoustic tweezers.

    PubMed

    Chen, Kejie; Wu, Mengxi; Guo, Feng; Li, Peng; Chan, Chung Yu; Mao, Zhangming; Li, Sixing; Ren, Liqiang; Zhang, Rui; Huang, Tony Jun

    2016-07-01

    The multicellular spheroid is an important 3D cell culture model for drug screening, tissue engineering, and fundamental biological research. Although several spheroid formation methods have been reported, the field still lacks high-throughput and simple fabrication methods to accelerate its adoption in drug development industry. Surface acoustic wave (SAW) based cell manipulation methods, which are known to be non-invasive, flexible, and high-throughput, have not been successfully developed for fabricating 3D cell assemblies or spheroids, due to the limited understanding on SAW-based vertical levitation. In this work, we demonstrated the capability of fabricating multicellular spheroids in the 3D acoustic tweezers platform. Our method used drag force from microstreaming to levitate cells in the vertical direction, and used radiation force from Gor'kov potential to aggregate cells in the horizontal plane. After optimizing the device geometry and input power, we demonstrated the rapid and high-throughput nature of our method by continuously fabricating more than 150 size-controllable spheroids and transferring them to Petri dishes every 30 minutes. The spheroids fabricated by our 3D acoustic tweezers can be cultured for a week with good cell viability. We further demonstrated that spheroids fabricated by this method could be used for drug testing. Unlike the 2D monolayer model, HepG2 spheroids fabricated by the 3D acoustic tweezers manifested distinct drug resistance, which matched existing reports. The 3D acoustic tweezers based method can serve as a novel bio-manufacturing tool to fabricate complex 3D cell assembles for biological research, tissue engineering, and drug development. PMID:27327102

  4. Time-shared optical tweezers with a microlens array for dynamic microbead arrays

    PubMed Central

    Tanaka, Yoshio; Wakida, Shin-ichi

    2015-01-01

    Dynamic arrays of microbeads and cells offer great flexibility and potential as platforms for sensing and manipulation applications in various scientific fields, especially biology and medicine. Here, we present a simple method for assembling and manipulating dense dynamic arrays based on time-shared scanning optical tweezers with a microlens array. Three typical examples, including the dynamic and simultaneous bonding of microbeads in real-time, are demonstrated. The optical design and the hardware setup for our approach are also described. PMID:26504619

  5. Dynamic micro-bead arrays using optical tweezers combined with intelligent control techniques.

    PubMed

    Tanaka, Yoshio; Kawada, Hiroyuki; Tsutsui, Shogo; Ishikawa, Mitsuru; Kitajima, Hiroyuki

    2009-12-21

    Dynamic micro-bead arrays offer great flexibility and potential as sensing tools in various scientific fields. Here we present a software-oriented approach for fully automated assembly of versatile dynamic micro-bead arrays using multi-beam optical tweezers combined with intelligent control techniques. Four typical examples, including the collision-free sorting of array elements by bead features, are demonstrated in real time. Control algorithms and experimental apparatus for these demonstrations are also described.

  6. Light-induced rotations of chiral birefringent microparticles in optical tweezers

    PubMed Central

    Donato, M. G.; Mazzulla, A.; Pagliusi, P.; Magazzù, A.; Hernandez, R. J.; Provenzano, C.; Gucciardi, P. G.; Maragò, O. M.; Cipparrone, G.

    2016-01-01

    We study the rotational dynamics of solid chiral and birefringent microparticles induced by elliptically polarized laser light in optical tweezers. We find that both reflection of left circularly polarized light and residual linear retardance affect the particle dynamics. The degree of ellipticity of laser light needed to induce rotations is found. The experimental results are compared with analytical calculations of the transfer of angular moment from elliptically polarized light to chiral birefringent particles. PMID:27601200

  7. Magnetic torque tweezers: measuring torsional stiffness in DNA and RecA-DNA filaments.

    PubMed

    Lipfert, Jan; Kerssemakers, Jacob W J; Jager, Tessa; Dekker, Nynke H

    2010-12-01

    We introduce magnetic torque tweezers, which enable direct single-molecule measurements of torque. Our measurements of the effective torsional stiffness C of dsDNA indicated a substantial force dependence, with C = approximately 40 nm at low forces up to C = approximately 100 nm at high forces. The initial torsional stiffness of RecA filaments was nearly twofold larger than that for dsDNA, yet at moderate torques further build-up of torsional strain was prevented. PMID:20953173

  8. Red blood cell membrane viscoelasticity, agglutination and zeta potential measurements with double optical tweezers

    NASA Astrophysics Data System (ADS)

    Fontes, Adriana; Fernandes, Heloise P.; Barjas-Castro, Maria L.; de Thomaz, André A.; de Ysasa Pozzo, Liliana; Barbosa, Luiz C.; Cesar, Carlos L.

    2006-02-01

    The red blood cell (RBC) viscoelastic membrane contains proteins and glycolproteins embedded in, or attached, to a fluid lipid bilayer and are negatively charged, which creates a repulsive electric (zeta) potential between the cells and prevents their aggregation in the blood stream. There are techniques, however, to decrease the zeta potential to allow cell agglutination which are the basis of most of the tests of antigen-antibody interactions in blood banks. This report shows the use of a double optical tweezers to measure RBC membrane viscosity, agglutination and zeta potential. In our technique one of the optical tweezers trap a silica bead that binds strongly to a RBC at the end of a RBCs rouleaux and, at the same time, acts as a pico-Newton force transducer, after calibration through its displacement from the equilibrium position. The other optical tweezers trap the RBC at the other end. To measure the membrane viscosity the optical force is measured as a function of the velocity between the RBCs. To measure the adhesion the tweezers are slowly displaced apart until the RBCs disagglutination happens. The RBC zeta potential is measured in two complimentary ways, by the force on the silica bead attached to a single RBC in response to an applied electric field, and the conventional way, by the measurement of terminal velocity of the RBC after released from the optical trap. These two measurements provide information about the RBC charges and, also, electrolytic solution properties. We believe this can improve the methods of diagnosis in blood banks.

  9. New biodiagnostics based on optical tweezers: typing red blood cells, and identification of drug resistant bacteria

    NASA Astrophysics Data System (ADS)

    Chen, Jia-Wen; Lin, Chuen-Fu; Wang, Shyang-Guang; Lee, Yi-Chieh; Chiang, Chung-Han; Huang, Min-Hui; Lee, Yi-Hsiung; Vitrant, Guy; Pan, Ming-Jeng; Lee, Horng-Mo; Liu, Yi-Jui; Baldeck, Patrice L.; Lin, Chih-Lang

    2013-09-01

    Measurements of optical tweezers forces on biological micro-objects can be used to develop innovative biodiagnostics methods. In the first part of this report, we present a new sensitive method to determine A, B, D types of red blood cells. Target antibodies are coated on glass surfaces. Optical forces needed to pull away RBC from the glass surface increase when RBC antigens interact with their corresponding antibodies. In this work, measurements of stripping optical forces are used to distinguish the major RBC types: group O Rh(+), group A Rh(+) and group B Rh(+). The sensitivity of the method is found to be at least 16-folds higher than the conventional agglutination method. In the second part of this report, we present an original way to measure in real time the wall thickness of bacteria that is one of the most important diagnostic parameters of bacteria drug resistance in hospital diagnostics. The optical tweezers force on a shell bacterium is proportional to its wall thickness. Experimentally, we determine the optical tweezers force applied on each bacteria family by measuring their escape velocity. Then, the wall thickness of shell bacteria can be obtained after calibrating with known bacteria parameters. The method has been successfully applied to indentify, from blind tests, Methicillinresistant Staphylococcus aureus (MRSA), including VSSA (NCTC 10442), VISA (Mu 50), and heto-VISA (Mu 3)

  10. Amyloid β-Protein Assembly: The Effect of Molecular Tweezers CLR01 and CLR03

    PubMed Central

    2015-01-01

    The early oligomerization of amyloid β-protein (Aβ) has been shown to be an important event in the pathology of Alzheimer’s disease (AD). Designing small molecule inhibitors targeting Aβ oligomerization is one attractive and promising strategy for AD treatment. Here we used ion mobility spectrometry coupled to mass spectrometry (IMS-MS) to study the different effects of the molecular tweezers CLR01 and CLR03 on Aβ self-assembly. CLR01 was found to bind to Aβ directly and disrupt its early oligomerization. Moreover, CLR01 remodeled the early oligomerization of Aβ42 by compacting the structures of dimers and tetramers and as a consequence eliminated higher-order oligomers. Unexpectedly, the negative-control derivative, CLR03, which lacks the hydrophobic arms of the tweezer structure, was found to facilitate early Aβ oligomerization. Our study provides an example of IMS as a powerful tool to study and better understand the interaction between small molecule modulators and Aβ oligomerization, which is not attainable by other methods, and provides important insights into therapeutic development of molecular tweezers for AD treatment. PMID:25751170

  11. Measurement of macrophage adhesion using optical tweezers with backward-scattered detection

    NASA Astrophysics Data System (ADS)

    Wei, Sung-Yang; Su, Yi-Jr; Shih, Po-Chen; Yang, Shih-Mo; Hsu, Long

    2010-08-01

    Macrophages are members of the leukocyte family. Tissue damage causes inflammation and release of vasoactive and chemotactic factors, which trigger a local increase in blood flow and capillary permeability. Then, leukocytes accumulate quickly to the infection site. The leukocyte extravasation process takes place according to a sequence of events that involve tethering, activation by a chemoattractant stimulus, adhesion by integrin binding, and migrating to the infection site. The leukocyte extravasation process reveals that adhesion is an important part of the immune system. Optical tweezers have become a useful tool with broad applications in biology and physics. In force measurement, the trapped bead as a probe usually uses a polystyrene bead of 1 μm diameter to measure adhesive force between the trapped beads and cell by optical tweezers. In this paper, using the ray-optics model calculated trapping stiffness and defined the linear displacement ranges. By the theoretical values of stiffness and linear displacement ranges, this study attempted to obtain a proper trapped particle size in measuring adhesive force. Finally, this work investigates real-time adhesion force measurements between human macrophages and trapped beads coated with lipopolysaccharides using optical tweezers with backscattered detection.

  12. Combining optical tweezers and patch clamp for studies of cell membrane electromechanics

    NASA Astrophysics Data System (ADS)

    Qian, Feng; Ermilov, Sergey; Murdock, David; Brownell, William E.; Anvari, Bahman

    2004-09-01

    We have designed and implemented a novel experimental setup which combines optical tweezers with patch-clamp apparatus to investigate the electromechanical properties of cellular plasma membranes. In this system, optical tweezers provide measurement of forces at piconewton scale, and the patch-clamp technique allows control of the cell transmembrane potential. A micron-size bead trapped by the optical tweezers is brought in contact with the membrane of a voltage-clamped cell, and subsequently moved away to form a plasma membrane tether. Bead displacement from the trapping center is monitored by a quadrant photodetector for dynamic measurements of tether force. Fluorescent beads and the corresponding fluorescence imaging optics are used to eliminate the shadow of the cell projected on the quadrant photodetector. Salient information associated with the mechanical properties of the membrane tether can thus be obtained. A unique feature of this setup is that the patch-clamp headstage and the manipulator for the recording pipette are mounted on a piezoelectric stage, preventing relative movements between the cell and the patch pipette during the process of tether pulling. Tethers can be pulled from the cell membrane at different holding potentials, and the tether force response can be measured while changing transmembrane potential. Experimental results from mammalian cochlear outer hair cells and human embryonic kidney cells are presented.

  13. Design and optimization of arrays of neodymium iron boron-based magnets for magnetic tweezers applications.

    PubMed

    Zacchia, Nicholas A; Valentine, Megan T

    2015-05-01

    We present the design methodology for arrays of neodymium iron boron (NdFeB)-based magnets for use in magnetic tweezers devices. Using finite element analysis (FEA), we optimized the geometry of the NdFeB magnet as well as the geometry of iron yokes designed to focus the magnetic fields toward the sample plane. Together, the magnets and yokes form a magnetic array which is the basis of the magnetic tweezers device. By systematically varying 15 distinct shape parameters, we determined those features that maximize the magnitude of the magnetic field gradient as well as the length scale over which the magnetic force operates. Additionally, we demonstrated that magnetic saturation of the yoke material leads to intrinsic limitations in any geometric design. Using this approach, we generated a compact and light-weight magnetic tweezers device that produces a high field gradient at the image plane in order to apply large forces to magnetic beads. We then fabricated the optimized yoke and validated the FEA by experimentally mapping the magnetic field of the device. The optimization data and iterative FEA approach outlined here will enable the streamlined design and construction of specialized instrumentation for force-sensitive microscopy. PMID:26026529

  14. Single-cell optoporation and transfection using femtosecond laser and optical tweezers

    PubMed Central

    Waleed, Muhammad; Hwang, Sun-Uk; Kim, Jung-Dae; Shabbir, Irfan; Shin, Sang-Mo; Lee, Yong-Gu

    2013-01-01

    In this paper, we demonstrate a new single-cell optoporation and transfection technique using a femtosecond Gaussian laser beam and optical tweezers. Tightly focused near-infrared (NIR) femtosecond laser pulse was employed to transiently perforate the cellular membrane at a single point in MCF-7 cancer cells. A distinct technique was developed by trapping the microparticle using optical tweezers to focus the femtosecond laser precisely on the cell membrane to puncture it. Subsequently, an external gene was introduced in the cell by trapping and inserting the same plasmid-coated microparticle into the optoporated cell using optical tweezers. Various experimental parameters such as femtosecond laser exposure power, exposure time, puncture hole size, exact focusing of the femtosecond laser on the cell membrane, and cell healing time were closely analyzed to create the optimal conditions for cell viability. Following the insertion of plasmid-coated microparticles in the cell, the targeted cells exhibited green fluorescent protein (GFP) under the fluorescent microscope, hence confirming successful transfection into the cell. This new optoporation and transfection technique maximizes the level of selectivity and control over the targeted cell, and this may be a breakthrough method through which to induce controllable genetic changes in the cell. PMID:24049675

  15. Acoustic tweezers via sub–time-of-flight regime surface acoustic waves

    PubMed Central

    Collins, David J.; Devendran, Citsabehsan; Ma, Zhichao; Ng, Jia Wei; Neild, Adrian; Ai, Ye

    2016-01-01

    Micrometer-scale acoustic waves are highly useful for refined optomechanical and acoustofluidic manipulation, where these fields are spatially localized along the transducer aperture but not along the acoustic propagation direction. In the case of acoustic tweezers, such a conventional acoustic standing wave results in particle and cell patterning across the entire width of a microfluidic channel, preventing selective trapping. We demonstrate the use of nanosecond-scale pulsed surface acoustic waves (SAWs) with a pulse period that is less than the time of flight between opposing transducers to generate localized time-averaged patterning regions while using conventional electrode structures. These nodal positions can be readily and arbitrarily positioned in two dimensions and within the patterning region itself through the imposition of pulse delays, frequency modulation, and phase shifts. This straightforward concept adds new spatial dimensions to which acoustic fields can be localized in SAW applications in a manner analogous to optical tweezers, including spatially selective acoustic tweezers and optical waveguides. PMID:27453940

  16. Probing orientation and rotation of red blood cells in optical tweezers by digital holographic microscopy

    NASA Astrophysics Data System (ADS)

    Cardenas, Nelson; Yu, Lingfeng; Mohanty, Samarendra K.

    2011-03-01

    Interaction of red blood cells (RBC) with optical tweezers has been found to differ under varied physiological and pathological conditions as compared to its normal conditions. Earlier, we reported difference in rotation of trapped RBC in hypertonic conditions for detection of malaria infection. Disk-like RBC when trapped in optical tweezers get oriented in the vertical plane to maximize interaction with trapping beam. However, classical bright field, phase contrast or epifluorescence microscopy cannot confirm its orientation, thus leading to ambiguous conclusions such as folding of RBC during trapping by some researchers. Now, with use of digital holographic microscopy (DHM), we achieved high axial sensitivity that confirmed orientation of trapped red blood cell. Further, DHM enabled quantitative phase imaging of RBC under hypertonic condition. Dynamic changes of rotating RBC under optical tweezers at different trapping laser power were evaluated by the use of DHM. The deviation from linear dependence of rotation speed of RBC on laser power, was attributed towards deformation of RBC shape due to higher laser power (or speed).

  17. Design and optimization of arrays of neodymium iron boron-based magnets for magnetic tweezers applications

    SciTech Connect

    Zacchia, Nicholas A.; Valentine, Megan T.

    2015-05-15

    We present the design methodology for arrays of neodymium iron boron (NdFeB)-based magnets for use in magnetic tweezers devices. Using finite element analysis (FEA), we optimized the geometry of the NdFeB magnet as well as the geometry of iron yokes designed to focus the magnetic fields toward the sample plane. Together, the magnets and yokes form a magnetic array which is the basis of the magnetic tweezers device. By systematically varying 15 distinct shape parameters, we determined those features that maximize the magnitude of the magnetic field gradient as well as the length scale over which the magnetic force operates. Additionally, we demonstrated that magnetic saturation of the yoke material leads to intrinsic limitations in any geometric design. Using this approach, we generated a compact and light-weight magnetic tweezers device that produces a high field gradient at the image plane in order to apply large forces to magnetic beads. We then fabricated the optimized yoke and validated the FEA by experimentally mapping the magnetic field of the device. The optimization data and iterative FEA approach outlined here will enable the streamlined design and construction of specialized instrumentation for force-sensitive microscopy.

  18. Grating-flanked plasmonic coaxial apertures for efficient fiber optical tweezers.

    PubMed

    Saleh, Amr A E; Sheikhoelislami, Sassan; Gastelum, Steven; Dionne, Jennifer A

    2016-09-01

    Subwavelength plasmonic apertures have been foundational for direct optical manipulation of nanoscale specimens including sub-100 nm polymeric beads, metallic nanoparticles and proteins. While most plasmonic traps result in two-dimensional localization, three-dimensional manipulation has been demonstrated by integrating a plasmonic aperture on an optical fiber tip. However, such 3D traps are usually inefficient since the optical mode of the fiber and the subwavelength aperture only weakly couple. In this paper we design more efficient optical-fiber-based plasmonic tweezers combining a coaxial plasmonic aperture with a plasmonic grating coupler at the fiber tip facet. Using full-field finite difference time domain analysis, we optimize the grating design for both gold and silver fiber-based coaxial tweezers such that the optical transmission through the apertures is maximized. With the optimized grating, we show that the maximum transmission efficiency increases from 2.5% to 19.6% and from 1.48% to 16.7% for the gold and silver structures respectively. To evaluate their performance as optical tweezers, we calculate the optical forces and the corresponding trapping potential on dielectric particles interacting with the apertures. We demonstrate that the enahncement in the transmission translates into an equivalent increase in the optical forces. Consequently, the optical power required to achieve stable optical trapping is significantly reduced allowing for efficient localization and 3D manipulation of sub-30 nm dielectric particles. PMID:27607663

  19. Acoustic tweezers for studying intracellular calcium signaling in SKBR-3 human breast cancer cells.

    PubMed

    Hwang, Jae Youn; Yoon, Chi Woo; Lim, Hae Gyun; Park, Jin Man; Yoon, Sangpil; Lee, Jungwoo; Shung, K Kirk

    2015-12-01

    Extracellular matrix proteins such as fibronectin (FNT) play crucial roles in cell proliferation, adhesion, and migration. For better understanding of these associated cellular activities, various microscopic manipulation tools have been used to study their intracellular signaling pathways. Recently, it has appeared that acoustic tweezers may possess similar capabilities in the study. Therefore, we here demonstrate that our newly developed acoustic tweezers with a high-frequency lithium niobate ultrasonic transducer have potentials to study intracellular calcium signaling by FNT-binding to human breast cancer cells (SKBR-3). It is found that intracellular calcium elevations in SKBR-3 cells, initially occurring on the microbead-contacted spot and then eventually spreading over the entire cell, are elicited by attaching an acoustically trapped FNT-coated microbead. Interestingly, they are suppressed by either extracellular calcium elimination or phospholipase C (PLC) inhibition. Hence, this suggests that our acoustic tweezers may serve as an alternative tool in the study of intracellular signaling by FNT-binding activities.

  20. Design and optimization of arrays of neodymium iron boron-based magnets for magnetic tweezers applications

    NASA Astrophysics Data System (ADS)

    Zacchia, Nicholas A.; Valentine, Megan T.

    2015-05-01

    We present the design methodology for arrays of neodymium iron boron (NdFeB)-based magnets for use in magnetic tweezers devices. Using finite element analysis (FEA), we optimized the geometry of the NdFeB magnet as well as the geometry of iron yokes designed to focus the magnetic fields toward the sample plane. Together, the magnets and yokes form a magnetic array which is the basis of the magnetic tweezers device. By systematically varying 15 distinct shape parameters, we determined those features that maximize the magnitude of the magnetic field gradient as well as the length scale over which the magnetic force operates. Additionally, we demonstrated that magnetic saturation of the yoke material leads to intrinsic limitations in any geometric design. Using this approach, we generated a compact and light-weight magnetic tweezers device that produces a high field gradient at the image plane in order to apply large forces to magnetic beads. We then fabricated the optimized yoke and validated the FEA by experimentally mapping the magnetic field of the device. The optimization data and iterative FEA approach outlined here will enable the streamlined design and construction of specialized instrumentation for force-sensitive microscopy.

  1. High-refractive index particles in counter-propagating optical tweezers - manipulation and forces

    NASA Astrophysics Data System (ADS)

    van der Horst, Astrid

    2006-09-01

    With a tightly focused single laser beam, also called optical tweezers, particles of a few nanometers up to several micrometers in size can be trapped and manipulated in 3D. The size, shape and refractive index of such colloidal particles are of influence on the optical forces exerted on them in the trap. A higher refractive-index difference between a particle and the surrounding medium will increase the forces. The destabilizing scattering force, however, pushing the particle in the direction of the beam, increases more than the gradient force, directed towards the focus. As a consequence, particles with a certain refractive index cannot be trapped in a single-beam gradient trap, and a limit is set to the force that can be exerted. We developed an experimental setup with two opposing high-numerical objectives. By splitting the laser beam, we created counter-propagating tweezers in which the scattering forces were canceled in the axial direction and high-refractive index and metallic particles could also be trapped. With the use of a separate laser beam combined with a quadrant photodiode, accurate position detection on a trapped particle in the counter-propagating tweezers is possible. We used this to determine trap stiffnesses, and show, with measurements and calculations, an enhancement in trap stiffness of at least 3 times for high-index 1.1-micrometer-diameter titania particles as compared to 1.4-micrometer-diameter silica particles under the same conditions. The ability to exert higher forces with lower laser power finds application in biophysical experiments, where laser damage and heating play a role. The manipulation of high-index and metallic particles also has applications in materials and colloid science, for example to incorporate high-index defects in colloidal photonic crystals. We demonstrate the patterning of high-index particles onto a glass substrate. The sample cell was mounted on a high-accuracy piezo stage combined with a long-range stage with

  2. Determining the structure-mechanics relationships of dense microtubule networks with confocal microscopy and magnetic tweezers-based microrheology.

    PubMed

    Yang, Yali; Valentine, Megan T

    2013-01-01

    The microtubule (MT) cytoskeleton is essential in maintaining the shape, strength, and organization of cells. Its spatiotemporal organization is fundamental for numerous dynamic biological processes, and mechanical stress within the MT cytoskeleton provides an important signaling mechanism in mitosis and neural development. This raises important questions about the relationships between structure and mechanics in complex MT structures. In vitro, reconstituted cytoskeletal networks provide a minimal model of cell mechanics while also providing a testing ground for the fundamental polymer physics of stiff polymer gels. Here, we describe our development and implementation of a broad tool kit to study structure-mechanics relationships in reconstituted MT networks, including protocols for the assembly of entangled and cross-linked MT networks, fluorescence imaging, microstructure characterization, construction and calibration of magnetic tweezers devices, and mechanical data collection and analysis. In particular, we present the design and assembly of three neodymium iron boron (NdFeB)-based magnetic tweezers devices optimized for use with MT networks: (1) high-force magnetic tweezers devices that enable the application of nano-Newton forces and possible meso- to macroscale materials characterization; (2) ring-shaped NdFeB-based magnetic tweezers devices that enable oscillatory microrheology measurements; and (3) portable magnetic tweezers devices that enable direct visualization of microscale deformation in soft materials under applied force.

  3. Three-dimensional image and spatial spectrum analysis of behavior of small animal erythrocytes in optical tweezers

    NASA Astrophysics Data System (ADS)

    Chen, Hui Chi; Shen, Wen-Tai; Kong, Yu-Han; Chuang, Chun-Hao

    2008-02-01

    Because of the softness of membrane, erythrocytes (red blood cell, RBC) have different shapes while being immersed in buffer with different osmotic pressure. While affecting by different viruses and illnesses, RBC may change its shape, or its membrane may become rigid. Moreover, RBC will ford and stretch when it is trapped by optical tweezers. Therefore, the behaviors of RBC in optical tweezers raise more discussion. In this report, we set up an optical tweezers to trap RBC of small animals like feline and canine. By adding a long working distance objective to collect the side-viewing image, a 3-D image system was constructed to detect the motion of trapped RBC. To improve the image quality for side-view, an aperture and narrow glass plate were used. From the video of these images and their spatial spectrum, the shape of trapped RBC was studied.

  4. Fluorinated porphyrin tweezer: a powerful reporter of absolute configuration for erythro and threo diols, amino alcohols, and diamines.

    PubMed

    Li, Xiaoyong; Tanasova, Marina; Vasileiou, Chrysoula; Borhan, Babak

    2008-02-13

    A general and sensitive nonempirical protocol to determine the absolute configurations of erythro and threo diols, amino alcohols, and diamines is reported. Binding of diols to the porphyrin tweezer system is greatly enhanced by increasing the Lewis acidity of the metalloporphyrin. Supramolecular complexes formed between the porphyrin tweezer host and chiral substrates exhibited exciton-coupled bisignate CD spectra with predictable signs based on the substituents on the chiral center. The working model suggests that the observed helicity of the porphyrin tweezer is dictated via steric differentiation experienced by the porphyrin ring bound to each chiral center. A variety of erythro and threo substrates were investigated to verify this chiroptical method. Their absolute configurations were unequivocally determined, and thus a general mnemonic is provided for the assignment of chirality.

  5. Magnetic tweezers with high permeability electromagnets for fast actuation of magnetic beads

    SciTech Connect

    Chen, La; Offenhäusser, Andreas; Krause, Hans-Joachim

    2015-04-15

    As a powerful and versatile scientific instrument, magnetic tweezers have been widely used in biophysical research areas, such as mechanical cell properties and single molecule manipulation. If one wants to steer bead position, the nonlinearity of magnetic properties and the strong position dependence of the magnetic field in most magnetic tweezers lead to quite a challenge in their control. In this article, we report multi-pole electromagnetic tweezers with high permeability cores yielding high force output, good maneuverability, and flexible design. For modeling, we adopted a piece-wise linear dependence of magnetization on field to characterize the magnetic beads. We implemented a bi-linear interpolation of magnetic field in the work space, based on a lookup table obtained from finite element simulation. The electronics and software were custom-made to achieve high performance. In addition, the effects of dimension and defect on structure of magnetic tips also were inspected. In a workspace with size of 0.1 × 0.1 mm{sup 2}, a force of up to 400 pN can be applied on a 2.8 μm superparamagnetic bead in any direction within the plane. Because the magnetic particle is always pulled towards a tip, the pulling forces from the pole tips have to be well balanced in order to achieve control of the particle’s position. Active video tracking based feedback control is implemented, which is able to work at a speed of up to 1 kHz, yielding good maneuverability of the magnetic beads.

  6. Dynamic properties of molecular tweezers with a bis(2-hydroxyphenyl)pyrimidine backbone.

    PubMed

    Tsuchido, Yoshitaka; Suzaki, Yuji; Ide, Tomohito; Osakada, Kohtaro

    2014-04-14

    4,6-Bis(2-hydroxyphenyl)-2-alkylpyrimidines with two anthryl or 9-ethylnylanthryl substituents at the positions para to the OH groups prefer a U-shaped conformation supported by two intramolecular OH⋅⋅⋅N hydrogen bonds in the solid state and in CDCl3 solution. The compound with a hexyl substituent on the pyrimidine group and two 9-ethynylanthryl arms at the hydroxyphenyl groups forms a 1:1 complex with 2,4,7-trinitrofluorenone. Its association constant K(a) was estimated to be 2100 M(-1) at 298 K, which is larger than those of other molecular tweezers (K(a) < 1000 M(-1)). DFT calculations suggested that the complex adopts a stable conformation supported by intramolecular hydrogen bonds among the OH groups and the pyrimidine ring as well as by intermolecular π-π interaction between the anthryl groups and 2,4,7-trinitrofluorenone. Addition of nBu4NF to a solution of the molecular tweezers or their complexes causes the cleavage of one or two OH⋅⋅⋅N hydrogen bonds, formation of new O⋅⋅⋅HF hydrogen bonds, and changes in the molecular conformation. The resulting structure of the molecular tweezers contains nonparallel anthryl groups, which do not bind the guest molecule. Photochemical measurements on 4,6-bis(2-hydroxyphenyl)-2-methylpyrimidine with two anthryl substituents showed negligible luminescence (quantum yield ϕ<0.01), owing to photoinduced electron transfer of the molecule with a U-shaped structure. However, the O-hexylated compound exhibits emission from the anthryl groups with ϕ=0.39.

  7. Magnetic tweezers with high permeability electromagnets for fast actuation of magnetic beads.

    PubMed

    Chen, La; Offenhäusser, Andreas; Krause, Hans-Joachim

    2015-04-01

    As a powerful and versatile scientific instrument, magnetic tweezers have been widely used in biophysical research areas, such as mechanical cell properties and single molecule manipulation. If one wants to steer bead position, the nonlinearity of magnetic properties and the strong position dependence of the magnetic field in most magnetic tweezers lead to quite a challenge in their control. In this article, we report multi-pole electromagnetic tweezers with high permeability cores yielding high force output, good maneuverability, and flexible design. For modeling, we adopted a piece-wise linear dependence of magnetization on field to characterize the magnetic beads. We implemented a bi-linear interpolation of magnetic field in the work space, based on a lookup table obtained from finite element simulation. The electronics and software were custom-made to achieve high performance. In addition, the effects of dimension and defect on structure of magnetic tips also were inspected. In a workspace with size of 0.1 × 0.1 mm(2), a force of up to 400 pN can be applied on a 2.8 μm superparamagnetic bead in any direction within the plane. Because the magnetic particle is always pulled towards a tip, the pulling forces from the pole tips have to be well balanced in order to achieve control of the particle's position. Active video tracking based feedback control is implemented, which is able to work at a speed of up to 1 kHz, yielding good maneuverability of the magnetic beads.

  8. Optical macro-tweezers: trapping of highly motile micro-organisms

    NASA Astrophysics Data System (ADS)

    Thalhammer, G.; Steiger, R.; Bernet, S.; Ritsch-Marte, M.

    2011-04-01

    Optical micromanipulation stands for contact-free handling of microscopic particles by light. Optical forces can manipulate non-absorbing objects in a large range of sizes, e.g., from biological cells down to cold atoms. Recently much progress has been made going from the micro- down to the nanoscale. Less attention has been paid to going the other way, trapping increasingly large particles. Optical tweezers typically employ a single laser beam tightly focused by a microscope objective of high numerical aperture to stably trap a particle in three dimensions (3D). As the particle size increases, stable 3D trapping in a single-beam trap requires scaling up the optical power, which eventually induces adverse biological effects. Moreover, the restricted field of view of standard optical tweezers, dictated by the use of high NA objectives, is particularly unfavorable for catching actively moving specimens. Both problems can be overcome by traps with counter-propagating beams. Our 'macro-tweezers' are especially designed to trap highly motile organisms, as they enable three-dimensional all-optical trapping and guiding in a volume of 2 × 1 × 2 mm3. Here we report for the first time the optical trapping of large actively swimming organisms, such as for instance Euglena protists and dinoflagellates of up to 70 µm length. Adverse bio-effects are kept low since trapping occurs outside high intensity regions, e.g., focal spots. We expect our approach to open various possibilities in the contact-free handling of 50-100 µm sized objects that could hitherto not be envisaged, for instance all-optical holding of individual micro-organisms for taxonomic identification, selective collecting or tagging.

  9. Magnetic tweezers with high permeability electromagnets for fast actuation of magnetic beads

    NASA Astrophysics Data System (ADS)

    Chen, La; Offenhäusser, Andreas; Krause, Hans-Joachim

    2015-04-01

    As a powerful and versatile scientific instrument, magnetic tweezers have been widely used in biophysical research areas, such as mechanical cell properties and single molecule manipulation. If one wants to steer bead position, the nonlinearity of magnetic properties and the strong position dependence of the magnetic field in most magnetic tweezers lead to quite a challenge in their control. In this article, we report multi-pole electromagnetic tweezers with high permeability cores yielding high force output, good maneuverability, and flexible design. For modeling, we adopted a piece-wise linear dependence of magnetization on field to characterize the magnetic beads. We implemented a bi-linear interpolation of magnetic field in the work space, based on a lookup table obtained from finite element simulation. The electronics and software were custom-made to achieve high performance. In addition, the effects of dimension and defect on structure of magnetic tips also were inspected. In a workspace with size of 0.1 × 0.1 mm2, a force of up to 400 pN can be applied on a 2.8 μm superparamagnetic bead in any direction within the plane. Because the magnetic particle is always pulled towards a tip, the pulling forces from the pole tips have to be well balanced in order to achieve control of the particle's position. Active video tracking based feedback control is implemented, which is able to work at a speed of up to 1 kHz, yielding good maneuverability of the magnetic beads.

  10. Optical tweezers study of red blood cell aggregation and disaggregation in plasma and protein solutions

    NASA Astrophysics Data System (ADS)

    Lee, Kisung; Kinnunen, Matti; Khokhlova, Maria D.; Lyubin, Evgeny V.; Priezzhev, Alexander V.; Meglinski, Igor; Fedyanin, Andrey A.

    2016-03-01

    Kinetics of optical tweezers (OT)-induced spontaneous aggregation and disaggregation of red blood cells (RBCs) were studied at the level of cell doublets to assess RBC interaction mechanics. Measurements were performed under in vitro conditions in plasma and fibrinogen and fibrinogen + albumin solutions. The RBC spontaneous aggregation kinetics was found to exhibit different behavior depending on the cell environment. In contrast, the RBC disaggregation kinetics was similar in all solutions qualitatively and quantitatively, demonstrating a significant contribution of the studied proteins to the process. The impact of the study on assessing RBC interaction mechanics and the protein contribution to the reversible RBC aggregation process is discussed.

  11. The Cryptococcus neoformans capsule: lessons from the use of optical tweezers and other biophysical tools

    PubMed Central

    Pontes, Bruno; Frases, Susana

    2015-01-01

    The fungal pathogen Cryptococcus neoformans causes life-threatening infections in immunocompromised individuals, representing one of the leading causes of morbidity and mortality in AIDS patients. The main virulence factor of C. neoformans is the polysaccharide capsule; however, many fundamental aspects of capsule structure and function remain poorly understood. Recently, important capsule properties were uncovered using optical tweezers and other biophysical techniques, including dynamic and static light scattering, zeta potential and viscosity analysis. This review provides an overview of the latest findings in this emerging field, explaining the impact of these findings on our understanding of C. neoformans biology and resistance to host immune defenses. PMID:26157436

  12. The Cryptococcus neoformans capsule: lessons from the use of optical tweezers and other biophysical tools.

    PubMed

    Pontes, Bruno; Frases, Susana

    2015-01-01

    The fungal pathogen Cryptococcus neoformans causes life-threatening infections in immunocompromised individuals, representing one of the leading causes of morbidity and mortality in AIDS patients. The main virulence factor of C. neoformans is the polysaccharide capsule; however, many fundamental aspects of capsule structure and function remain poorly understood. Recently, important capsule properties were uncovered using optical tweezers and other biophysical techniques, including dynamic and static light scattering, zeta potential and viscosity analysis. This review provides an overview of the latest findings in this emerging field, explaining the impact of these findings on our understanding of C. neoformans biology and resistance to host immune defenses.

  13. Measuring stall forces in vivo with optical tweezers through light momentum changes

    NASA Astrophysics Data System (ADS)

    Mas, J.; Farré, A.; López-Quesada, C.; Fernández, X.; Martín-Badosa, E.; Montes-Usategui, M.

    2011-10-01

    The stall forces of processive molecular motors have been widely studied previously in vitro. Even so, in vivo experiments are required for determining the actual performance of each molecular motor in its natural environment. We report the direct measurement of light momentum changes in single beam optical tweezers as a suitable technique for measuring forces inside living cells, where few alternatives exist. The simplicity of this method, which does not require force calibration for each trapped object, makes it convenient for measuring the forces involved in fast dynamic biological processes such us intracellular traffic. Here we present some measurements of the stall force of processive molecular motors inside living Allium cepa cells.

  14. Programmable manipulation of motile cells in optoelectronic tweezers using a grayscale image

    NASA Astrophysics Data System (ADS)

    Choi, Wonjae; Nam, Seong-Won; Hwang, Hyundoo; Park, Sungsu; Park, Je-Kyun

    2008-10-01

    This paper describes a grayscale optoelectronic tweezers (OET) which allows adjustment of the electric field strength at each position of OET. A grayscale light image was used to pattern vertical electric field strength on an OET. As an electric field depends on the brightness at each point, the brighter light patterns generate the stronger electric field in the OET. Its feasibility for application to cell manipulation was demonstrated by aligning highly motile protozoan cells in vertical direction. Depending on the brightness of each pixel, the behaviors of aligned cells varied due to the different electric field strength to each cell.

  15. Laser-induced fusion of human embryonic stem cells with optical tweezers

    SciTech Connect

    Chen Shuxun; Wang Xiaolin; Sun Dong; Cheng Jinping; Han Cheng, Shuk; Kong, Chi-Wing; Li, Ronald A.

    2013-07-15

    We report a study on the laser-induced fusion of human embryonic stem cells (hESCs) at the single-cell level. Cells were manipulated by optical tweezers and fused under irradiation with pulsed UV laser at 355 nm. Successful fusion was indicated by green fluorescence protein transfer. The influence of laser pulse energy on the fusion efficiency was investigated. The fused products were viable as gauged by live cell staining. Successful fusion of hESCs with somatic cells was also demonstrated. The reported fusion outcome may facilitate studies of cell differentiation, maturation, and reprogramming.

  16. Laser-induced fusion of human embryonic stem cells with optical tweezers

    NASA Astrophysics Data System (ADS)

    Chen, Shuxun; Cheng, Jinping; Kong, Chi-Wing; Wang, Xiaolin; Han Cheng, Shuk; Li, Ronald A.; Sun, Dong

    2013-07-01

    We report a study on the laser-induced fusion of human embryonic stem cells (hESCs) at the single-cell level. Cells were manipulated by optical tweezers and fused under irradiation with pulsed UV laser at 355 nm. Successful fusion was indicated by green fluorescence protein transfer. The influence of laser pulse energy on the fusion efficiency was investigated. The fused products were viable as gauged by live cell staining. Successful fusion of hESCs with somatic cells was also demonstrated. The reported fusion outcome may facilitate studies of cell differentiation, maturation, and reprogramming.

  17. Fast acoustic tweezers for the two-dimensional manipulation of individual particles in microfluidic channels

    NASA Astrophysics Data System (ADS)

    Tran, S. B. Q.; Marmottant, P.; Thibault, P.

    2012-09-01

    This paper presents a microfluidic device that implements standing surface acoustic waves in order to handle single cells, droplets, and generally particles. The particles are moved in a very controlled manner by the two-dimensional drifting of a standing wave array, using a slight frequency modulation of two ultrasound emitters around their resonance. These acoustic tweezers allow any type of motion at velocities up to few ×10 mm/s, while the device transparency is adapted for optical studies. The possibility of automation provides a critical step in the development of lab-on-a-chip cell sorters and it should find applications in biology, chemistry, and engineering domains.

  18. Optical Tweezers Analysis of Double-Stranded DNA Denaturation in the Presence of Urea

    NASA Astrophysics Data System (ADS)

    Zhu, Chunli; Li, Jing

    2016-09-01

    Urea is a kind of denaturant prone to form hydrogen bonds with the electronegative centers of the nitrogenous bases, threatening the stability of hydrogen bonds between DNA base pairs. In this paper, the stability and stiffness of DNA double helix influenced by urea are investigated at single-molecule level using optical tweezers. Experimental results show that DNA's double helix stability and stiffness both decrease with increasing urea concentration. In addition, the re-forming of ruptured hydrogen bonds between the base pairs is blocked by urea as the tension on DNA is released.

  19. Photovoltaic tweezers an emergent tool for applications in nano and bio-technology

    NASA Astrophysics Data System (ADS)

    Carrascosa, M.; García-Cabañes, A.; Jubera, M.; Elvira, I.; Burgos, H.; Bella, J. L.; Agulló-López, F.; Muñoz-Martínez, J. F.; Alcázar, A.

    2015-05-01

    An overview of the work recently conducted by our group on the development and applications of photovoltaic tweezers is presented. It includes the analysis of the physical basis of the method and the main achievements in its experimental implementation. Particular attention will be paid to the main potential applications and first demonstrations of its use in nano- and bio-technology. Specifically: i) fabrication of metallic nanoestructures for plasmonic applications, ii) development of diffractive components, iii) manipulation and patterning (1D and 2D) of various types of bio-objects (spores or pollen…) and iv) effects of PV fields of LiNbO3 in tumour cells.

  20. Template stripped double nanohole in a gold film for nano-optical tweezers.

    PubMed

    Zehtabi-Oskuie, Ana; Zinck, Aurora A; Gelfand, Ryan M; Gordon, Reuven

    2014-12-12

    Double nanohole (DNH) laser tweezers can optically trap and manipulate objects such as proteins, nanospheres, and other nanoparticles; however, precise fabrication of those DNHs has been expensive with low throughput. In this work, template stripping was used to pattern DNHs with gaps as small as 7 nm, in optically thick Au films. These DNHs were used to trap streptavidin as proof of operation. The structures were processed multiple times from the same template to demonstrate reusability. Template stripping is a promising method for high-throughput, reproducible, and cost efficient fabrication of DNH apertures for optical trapping. PMID:25407447

  1. A journey in bioinspired supramolecular chemistry: from molecular tweezers to small molecules that target myotonic dystrophy

    PubMed Central

    2016-01-01

    Summary This review summarizes part of the author’s research in the area of supramolecular chemistry, beginning with his early life influences and early career efforts in molecular recognition, especially molecular tweezers. Although designed to complex DNA, these hosts proved more applicable to the field of host–guest chemistry. This early experience and interest in intercalation ultimately led to the current efforts to develop small molecule therapeutic agents for myotonic dystrophy using a rational design approach that heavily relies on principles of supramolecular chemistry. How this work was influenced by that of others in the field and the evolution of each area of research is highlighted with selected examples. PMID:26877815

  2. Measurement of the total optical angular momentum transfer in optical tweezers.

    PubMed

    Parkin, Simon; Knöner, Gregor; Nieminen, Timo A; Heckenberg, Norman R; Rubinsztein-Dunlop, Halina

    2006-07-24

    We describe a way to determine the total angular momentum, both spin and orbital, transferred to a particle trapped in optical tweezers. As an example an LG(02) mode of a laser beam with varying degrees of circular polarisation is used to trap and rotate an elongated particle with a well defined geometry. The method successfully estimates the total optical torque applied to the particle. For this technique, there is no need to measure the viscous drag on the particle, as it is an optical measurement. Therefore, knowledge of the particle's size and shape, as well as the fluid's viscosity, is not required.

  3. Nano-bio-optomechanics: nanoaperture tweezers probe single nanoparticles, proteins, and their interactions

    NASA Astrophysics Data System (ADS)

    Gordon, Reuven

    2015-09-01

    Nanoparticles in the single digit nanometer range can be easily isolated and studied with low optical powers using nanoaperture tweezers. We have studied individual proteins and their interactions with small molecules, DNA and antibodies. Recently, using the fluctuations of the trapped object, we have pioneered a new way to "listen" to the vibrations of nanoparticles in the 100 GHz - 1 THz range; the approach is called extraordinary acoustic Raman (EAR). EAR gives unprecedented low frequency spectra of individual proteins in solution, allowing for identification and analysis, as well as probing their role in biological functions. We have also used EAR to study the elastic properties, shape and size of various individual nanoparticles.

  4. Using electrical and optical tweezers to facilitate studies of molecular motors.

    PubMed

    Arsenault, Mark E; Sun, Yujie; Bau, Haim H; Goldman, Yale E

    2009-06-28

    Dielectrophoresis was used to stretch and suspend actin filaments across a trench etched between two electrodes patterned on a glass slide. Optical tweezers were used to bring a motor protein-coated bead into close proximity to a pre-selected, suspended actin filament, facilitating the attachment of the myosin-coated bead to the filament. The clearance beneath the filament allowed the bead to move freely along and around its filamentous track, unhindered by solid surfaces. Using defocused images, the three-dimensional position of the bead was tracked as a function of time to obtain its trajectory. Experiments were carried out with myosin V and myosin X. Both motor proteins followed left-handed helical paths with the myosin X motor exhibiting a shorter pitch than the myosin V. The combined use of electrostatic and optical tweezers facilitates the preparation of motility assays with suspended tracks. Variants of this technique will enable higher complexity experiments in vitro to better understand the behavior of motors in cells. PMID:19506758

  5. Optical tweezers as a tool for the functional analysis of neuronal cell membrane receptors

    NASA Astrophysics Data System (ADS)

    Zahn, Martin; Goetz, Bernhard; Faissner, Andreas; Seeger, Stefan

    1997-12-01

    Recognition molecules play important regulatory roles during pattern formation of the nervous system. We here show that optical tweezers can successfully be used to functionally and quantitatively compare neuron interactions with glycoproteins of the extracellular matrix. We measured the forces of interactions between tenascin-C, laminin-1 and fibronectin coated polystyrol beads and the cell membranes of different nervous cell-types. This was achieved by applying the optical tweezers as picotensometer to pull the adhering beads with varying axial forces. To this aim, the minimal laser powers for capturing polystyrene beads in different solutions were measured. With the corresponding Archimedes Forces the acting forces in the range of pN were calculated. The glycoproteins showed significantly different behavior. Specific binding was shown by antibody experiments, in which the binding forces were significantly reduced for the corresponding antigens but not for the other glycoproteins. Together with experiments concerning the moving within the plane of the membrane and the cleavage with glycosyl-phosphatidyl-inositol-anchors specific phospholipase-C we suggest that these glycoproteins interact with neurons by different mechanisms.

  6. Optical tweezers as a tool for the functional analysis of neuronal cell membrane receptors

    NASA Astrophysics Data System (ADS)

    Zahn, Martin; Goetz, Bernhard; Faissner, Andreas; Seeger, Stefan

    1998-01-01

    Recognition molecules play important regulatory roles during pattern formation of the nervous system. We here show that optical tweezers can successfully be used to functionally and quantitatively compare neuron interactions with glycoproteins of the extracellular matrix. We measured the forces of interactions between tenascin-C, laminin-1 and fibronectin coated polystyrol beads and the cell membranes of different nervous cell-types. This was achieved by applying the optical tweezers as picotensometer to pull the adhering beads with varying axial forces. To this aim, the minimal laser powers for capturing polystyrene beads in different solutions were measured. With the corresponding Archimedes Forces the acting forces in the range of pN were calculated. The glycoproteins showed significantly different behavior. Specific binding was shown by antibody experiments, in which the binding forces were significantly reduced for the corresponding antigens but not for the other glycoproteins. Together with experiments concerning the moving within the plane of the membrane and the cleavage with glycosyl-phosphatidyl-inositol-anchors specific phospholipase-C we suggest that these glycoproteins interact with neurons by different mechanisms.

  7. Application of optical tweezers and excimer laser to study protoplast fusion

    NASA Astrophysics Data System (ADS)

    Kantawang, Titirat; Samipak, Sompid; Limtrakul, Jumras; Chattham, Nattaporn

    2015-07-01

    Protoplast fusion is a physical phenomenon that two protoplasts come in contact and fuse together. Doing so, it is possible to combine specific genes from one protoplast to another during fusion such as drought resistance and disease resistance. There are a few possible methods to induce protoplast fusion, for example, electrofusion and chemical fusion. In this study, chemical fusion was performed with laser applied as an external force to enhance rate of fusion and observed under a microscope. Optical tweezers (1064 nm with 100X objective N.A. 1.3) and excimer laser (308 nm LMU-40X-UVB objective) were set with a Nikon Ti-U inverted microscope. Samples were prepared by soaking in hypertonic solution in order to induce cell plasmolysis. Elodea Canadensis and Allium cepa plasmolysed leaves were cut and observed under microscope. Concentration of solution was varied to induce difference turgor pressures on protoplasts pushing at cell wall. Free protoplasts in solution were trapped by optical tweezers to study the effect of Polyethylene glycol (PEG) solution. PEG was diluted by Ca+ solution during the process to induced protoplast cell contact and fusion. Possibility of protoplast fusion by excimer laser was investigated and found possible. Here we report a novel tool for plant cell fusion using excimer laser. Plant growth after cell fusion is currently conducted.

  8. Crosstalk elimination in the detection of dual-beam optical tweezers by spatial filtering

    SciTech Connect

    Ott, Dino; Oddershede, Lene B.; Reihani, S. Nader S.

    2014-05-15

    In dual-beam optical tweezers, the accuracy of position and force measurements is often compromised by crosstalk between the two detected signals, this crosstalk leading to systematic and significant errors on the measured forces and distances. This is true both for dual-beam optical traps where the splitting of the two traps is done by polarization optics and for dual optical traps constructed by other methods, e.g., holographic tweezers. If the two traps are orthogonally polarized, most often crosstalk is minimized by inserting polarization optics in front of the detector; however, this method is not perfect because of the de-polarization of the trapping beam introduced by the required high numerical aperture optics. Here we present a simple and easy-to-implement method to efficiently eliminate crosstalk. The method is based on spatial filtering by simply inserting a pinhole at the correct position and is highly compatible with standard back focal plane photodiode based detection of position and force. Our spatial filtering method reduces crosstalk up to five times better than polarization filtering alone. The effectiveness is dependent on pinhole size and distance between the traps and is here quantified experimentally and reproduced by theoretical modeling. The method here proposed will improve the accuracy of force-distance measurements, e.g., of single molecules, performed by dual-beam optical traps and hence give much more scientific value for the experimental efforts.

  9. A novel single fiber optical tweezers based on light-induced thermal effect

    NASA Astrophysics Data System (ADS)

    Zhang, Yu; Liu, Zhihai; Liang, Peibo; Zhang, Yaxun; Zhao, Enming; Yang, Jun; Yuan, Libo

    2015-07-01

    We present and demonstrate a novel single fiber optical tweezers which can trap and launch (clean) a target polystyrene (PS) microsphere (diameter~10μm) with independent control by using two wavelengths beams: 980nm and 1480nm. We employ 980nm laser beam to trap the target PS microsphere by molding the fiber tip into a special tapered-shape; and we employ 1480nm laser beam to launch the trapped PS microsphere with a certain velocity by using the thermophoresis force generated from the thermal effect due to the high absorption of the 1480nm laser beams in water. When the launching force is smaller than the trapping force, the PS microsphere will be trapped near the fiber tip, and the launching force will blow away other PS microspheres in the workspace realizing the cleaning function; When the launching force is larger than the trapping force, the trapped PS microsphere will be launched away from the fiber tip with a certain velocity and towards a certain direction, realizing the launching function. This PS microsphere launching and cleaning functions expanded new features of single fiber optical tweezers, providing for the possibility of more practical applications in the micro manipulation research fields.

  10. Thermal tweezers for manipulation of adatoms and nanoparticles on surfaces heated by interfering laser pulses

    SciTech Connect

    Mason, Daniel R.; Gramotnev, Dmitri K.; Gramotnev, Galina

    2008-09-15

    We conduct the detailed numerical investigation of a nanomanipulation and nanofabrication technique--thermal tweezers with dynamic evolution of surface temperature, caused by absorption of interfering laser pulses in a thin metal film or any other absorbing surface. This technique uses random Brownian forces in the presence of strong temperature modulation (surface thermophoresis) for effective manipulation of particles/adatoms with nanoscale resolution. Substantial redistribution of particles on the surface is shown to occur with the typical size of the obtained pattern elements of {approx}100 nm, which is significantly smaller than the wavelength of the incident pulses used (532 nm). It is also demonstrated that thermal tweezers based on surface thermophoresis of particles/adatoms are much more effective in achieving permanent high maximum-to-minimum concentration ratios than bulk thermophoresis, which is explained by the interaction of diffusing particles with the periodic lattice potential on the surface. Typically required pulse regimes including pulse lengths and energies are also determined. The approach is applicable for reproducing any holographically achievable surface patterns, and can thus be used for engineering properties of surfaces including nanopatterning and design of surface metamaterials.

  11. In situ microparticle analysis of marine phytoplankton cells with infrared laser-based optical tweezers

    NASA Astrophysics Data System (ADS)

    Sonek, G. J.; Liu, Y.; Iturriaga, R. H.

    1995-11-01

    We describe the application of infrared optical tweezers to the in situ microparticle analysis of marine phytoplankton cells. A Nd:YAG laser (lambda=3D 1064 nm) trap is used to confine and manipulate single Nannochloris and Synechococcus cells in an enriched seawater medium while spectral fluorescence and Lorenz-Mie backscatter signals are simultaneously acquired under a variety of excitation and trapping conditions. Variations in the measured fluorescence intensities of chlorophyll a (Chl a) and phycoerythrin pigments in phytoplankton cells are observed. These variations are related, in part, to basic intrasample variability, but they also indicate that increasing ultraviolet-exposure time and infrared trapping power may have short-term effects on cellular physiology that are related to Chl a photobleaching and laser-induced heating, respectively. The use of optical tweezers to study the factors that affect marine cell physiology and the processes of absorption, scattering, and attenuation by individual cells, organisms, and particulate matter that contribute to optical closure on a microscopic scale are also described. (c)1995 Optical Society of America

  12. Analysis of cell mechanics in single vinculin-deficient cells using a magnetic tweezer

    NASA Technical Reports Server (NTRS)

    Alenghat, F. J.; Fabry, B.; Tsai, K. Y.; Goldmann, W. H.; Ingber, D. E.

    2000-01-01

    A magnetic tweezer was constructed to apply controlled tensional forces (10 pN to greater than 1 nN) to transmembrane receptors via bound ligand-coated microbeadswhile optically measuring lateral bead displacements within individual cells. Use of this system with wild-type F9 embryonic carcinoma cells and cells from a vinculin knockout mouse F9 Vin (-/-) revealed much larger differences in the stiffness of the transmembrane integrin linkages to the cytoskeleton than previously reported using related techniques that measured average mechanical properties of large cell populations. The mechanical properties measured varied widely among cells, exhibiting an approximately log-normal distribution. The median lateral bead displacement was 2-fold larger in F9 Vin (-/-) cells compared to wild-type cells whereas the arithmetic mean displacement only increased by 37%. We conclude that vinculin serves a greater mechanical role in cells than previously reported and that this magnetic tweezer device may be useful for probing the molecular basis of cell mechanics within single cells. Copyright 2000 Academic Press.

  13. Laser scanning confocal microscopy and laser tweezers based experiments to understand dentine-bacteria interactions

    NASA Astrophysics Data System (ADS)

    Peng, Sum Chee; Mohanty, Samarendra; Gupta, P. K.; Kishen, Anil

    2007-02-01

    Failure of endodontic treatment is commonly due to Enterococcal infection. In this study influence of chemical treatments of type-I collagen membrane by chemical agents commonly used in endodontic treatment on Enterococcus faecalis cell adherence was evaluated. In order to determine the change in number of adhering bacteria after chemical treatment, confocal laser scanning microscopy was used. For this, overnight culture of E faecalis in All Culture broth was applied to chemically treated type-I collagen membrane. It was found that Ca(OH) II treated groups had statistically significant (p value=0.05) increase in population of bacteria adherence. The change in adhesion force between bacteria and collagen was determined by using optical tweezers (1064 nm). For this experiment, Type-I collagen membrane was soaked for 5 mins in a media that contained 50% all culture media and 50% saturated Ca(OH) II . The membrane was spread on the coverslip, on which diluted bacterial suspension was added. The force of laser tweezers on the bacteria was estimated at different trap power levels using viscous drag method and trapping stiffness was calculated using Equipartition theorem method. Presence of Ca(OH) II was found to increase the cell-substrate adherence force from 0.38pN to >2.1pN. Together, these experiments show that it was highly probable that the increase in adherence to collagen was due to a stronger adhesion in the presence of Ca (OH) II.

  14. In situ calibrating optical tweezers with sinusoidal-wave drag force method

    NASA Astrophysics Data System (ADS)

    Li, Di; Zhou, Jin-Hua; Hu, Xin-Yao; Zhong, Min-Cheng; Gong, Lei; Wang, Zi-Qiang; Wang, Hao-Wei; Li, Yin-Mei

    2015-11-01

    We introduce a corrected sinusoidal-wave drag force method (SDFM) into optical tweezers to calibrate the trapping stiffness of the optical trap and conversion factor (CF) of photodetectors. First, the theoretical analysis and experimental result demonstrate that the correction of SDFM is necessary, especially the error of no correction is up to 11.25% for a bead of 5 μm in diameter. Second, the simulation results demonstrate that the SDFM has a better performance in the calibration of optical tweezers than the triangular-wave drag force method (TDFM) and power spectrum density method (PSDM) at the same signal-to-noise ratio or trapping stiffness. Third, in experiments, the experimental standard deviations of calibration of trapping stiffness and CF with the SDFM are about less than 50% of TDFM and PSDM especially at low laser power. Finally, the experiments of stretching DNA verify that the in situ calibration with the SDFM improves the measurement stability and accuracy. Project supported by the National Natural Science Foundation of China (Grant Nos. 11302220, 11374292, and 31100555) and the National Basic Research Program of China (Grant No. 2011CB910402).

  15. Luminescent nanoparticle trapping with far-field optical fiber-tip tweezers.

    PubMed

    Decombe, Jean-Baptiste; Valdivia-Valero, Francisco J; Dantelle, Géraldine; Leménager, Godefroy; Gacoin, Thierry; Colas des Francs, Gérard; Huant, Serge; Fick, Jochen

    2016-03-01

    We report stable and reproducible trapping of luminescent dielectric YAG:Ce(3+) nanoparticles with sizes down to 60 nm using far-field dual fiber tip optical tweezers. The particles are synthesized by a specific glycothermal route followed by an original protected annealing step, resulting in significantly enhanced photostability. The tweezers properties are analyzed by studying the trapped particles residual Brownian motion using video or reflected signal records. The trapping potential is harmonic in the transverse direction to the fiber axis, but reveals interference fringes in the axial direction. Large trapping stiffness of 35 and 2 pN μm(-1) W(-1) is measured for a fiber tip-to-tip distance of 3 μm and 300 nm and 60 nm particles, respectively. The forces acting on the nanoparticles are discussed within the dipolar approximation (gradient and scattering force contributions) or exact calculations using the Maxwell Stress Tensor formalism. Prospects for trapping even smaller particles are discussed. PMID:26883602

  16. Holographic optical tweezers: microassembling of shape-complementary 2PP building blocks

    NASA Astrophysics Data System (ADS)

    Ksouri, Sarah Isabelle; Mattern, Manuel; Köhler, Jannis; Aumann, Andreas; Zyla, Gordon; Ostendorf, Andreas

    2014-09-01

    Based on an ongoing trend in miniaturization and due to the increased complexity in MEMS-technology new methods of assembly need to be developed. Recent developments show that particularly optical forces are suitable to meet the requirements. The unique advantages of optical tweezers (OT) are attractive due to their contactless and precise manipulation forces. Spherical as well as non-spherical shaped pre-forms can already be assembled arbitrarily by using appropriate beam profiles generated by a spatial light modulator (SLM), resulting in a so called holographic optical tweezer (HOT) setup. For the fabrication of shape-complementary pre-forms, a two-photon-polymerization (2PP) process is implemented. The purpose of the process combination of 2PP and HOT is the development of an optical microprocessing platform for assembling arbitrary building blocks. Here, the optimization of the 2PP and HOT processes is described in order to allow the fabrication and 3D assembling of interlocking components. Results include the analysis of the dependence of low and high qualities of 2PP microstructures and their manufacturing accuracy for further HOT assembling processes. Besides, the applied detachable interlocking connections of the 2PP building blocks are visualized by an application example. In the long-term a full optical assembly method without applying any mechanical forces can thus be realized.

  17. Auto- and cross-power spectral analysis of dual trap optical tweezer experiments using Bayesian inference

    NASA Astrophysics Data System (ADS)

    von Hansen, Yann; Mehlich, Alexander; Pelz, Benjamin; Rief, Matthias; Netz, Roland R.

    2012-09-01

    The thermal fluctuations of micron-sized beads in dual trap optical tweezer experiments contain complete dynamic information about the viscoelastic properties of the embedding medium and—if present—macromolecular constructs connecting the two beads. To quantitatively interpret the spectral properties of the measured signals, a detailed understanding of the instrumental characteristics is required. To this end, we present a theoretical description of the signal processing in a typical dual trap optical tweezer experiment accounting for polarization crosstalk and instrumental noise and discuss the effect of finite statistics. To infer the unknown parameters from experimental data, a maximum likelihood method based on the statistical properties of the stochastic signals is derived. In a first step, the method can be used for calibration purposes: We propose a scheme involving three consecutive measurements (both traps empty, first one occupied and second empty, and vice versa), by which all instrumental and physical parameters of the setup are determined. We test our approach for a simple model system, namely a pair of unconnected, but hydrodynamically interacting spheres. The comparison to theoretical predictions based on instantaneous as well as retarded hydrodynamics emphasizes the importance of hydrodynamic retardation effects due to vorticity diffusion in the fluid. For more complex experimental scenarios, where macromolecular constructs are tethered between the two beads, the same maximum likelihood method in conjunction with dynamic deconvolution theory will in a second step allow one to determine the viscoelastic properties of the tethered element connecting the two beads.

  18. Counter-propagating dual-trap optical tweezers based on linear momentum conservation

    SciTech Connect

    Ribezzi-Crivellari, M.; Huguet, J. M.; Ritort, F.

    2013-04-15

    We present a dual-trap optical tweezers setup which directly measures forces using linear momentum conservation. The setup uses a counter-propagating geometry, which allows momentum measurement on each beam separately. The experimental advantages of this setup include low drift due to all-optical manipulation, and a robust calibration (independent of the features of the trapped object or buffer medium) due to the force measurement method. Although this design does not attain the high-resolution of some co-propagating setups, we show that it can be used to perform different single molecule measurements: fluctuation-based molecular stiffness characterization at different forces and hopping experiments on molecular hairpins. Remarkably, in our setup it is possible to manipulate very short tethers (such as molecular hairpins with short handles) down to the limit where beads are almost in contact. The setup is used to illustrate a novel method for measuring the stiffness of optical traps and tethers on the basis of equilibrium force fluctuations, i.e., without the need of measuring the force vs molecular extension curve. This method is of general interest for dual trap optical tweezers setups and can be extended to setups which do not directly measure forces.

  19. Optical tweezers and non-ratiometric fluorescent-dye-based studies of respiration in sperm mitochondria

    NASA Astrophysics Data System (ADS)

    Chen, Timothy; Shi, Linda Z.; Zhu, Qingyuan; Chandsawangbhuwana, Charlie; Berns, Michael W.

    2011-04-01

    The purpose of this study is to investigate how the mitochondrial membrane potential affects sperm motility using laser tweezers and a non-ratiometric fluorescent probe, DiOC6(3). A 1064 nm Nd:YVO4 continuous wave laser was used to trap motile sperm at a power of 450 mW in the trap spot. Using customized tracking software, the curvilinear velocity (VCL) and the escape force from the laser tweezers were measured. Human (Homo sapiens), dog (Canis lupis familiaris) and drill (Mandrillus leucophaeus) sperm were treated with DiOC6(3) to measure the membrane potential in the mitochondria-rich sperm midpieces. Sperm from all three species exhibited an increase in fluorescence when treated with the DiOC6(3). When a cyanide inhibitor (CCCP) of aerobic respiration was applied, sperm of all three species exhibited a reduction in fluorescence to pre-dye levels. With respect to VCL and escape force, the CCCP had no effect on dog or human sperm, suggesting a major reliance upon anaerobic respiration (glycolysis) for ATP in these two species. Based on the preliminary study on drill sperm, CCCP caused a drop in the VCL, suggesting potential reliance on both glycolysis and aerobic respiration for motility. The results demonstrate that optical trapping in combination with DiOC6(3) is an effective way to study sperm motility and energetics.

  20. Application of laser tweezers Raman spectroscopy techniques to the monitoring of single cell response to stimuli

    NASA Astrophysics Data System (ADS)

    Chan, James W.; Liu, Rui; Matthews, Dennis L.

    2012-06-01

    Laser tweezers Raman spectroscopy (LTRS) combines optical trapping with micro-Raman spectroscopy to enable label-free biochemical analysis of individual cells and small biological particles in suspension. The integration of the two technologies greatly simplifies the sample preparation and handling of suspension cells for spectroscopic analysis in physiologically meaningful conditions. In our group, LTRS has been used to study the effects of external perturbations, both chemical and mechanical, on the biochemistry of the cell. Single cell dynamics can be studied by performing longitudinal studies to continuously monitor the response of the cell as it interacts with its environment. The ability to carry out these measurements in-vitro makes LTRS an attractive tool for many biomedical applications. Here, we discuss the use of LTRS to study the response of cancer cells to chemotherapeutics and bacteria cells to antibiotics and show that the life cycle and apoptosis of the cells can be detected. These results show the promise of LTRS for drug discovery/screening, antibiotic susceptibility testing, and chemotherapy response monitoring applications. In separate experiments, we study the response of red blood cells to the mechanical forces imposed on the cell by the optical tweezers. A laser power dependent deoxygenation of the red blood cell in the single beam trap is reported. Normal, sickle cell, and fetal red blood cells have a different behavior that enables the discrimination of the cell types based on this mechanochemical response. These results show the potential utility of LTRS for diagnosing and studying red blood cell diseases.

  1. A study of red blood cell deformability in diabetic retinopathy using optical tweezers

    NASA Astrophysics Data System (ADS)

    Smart, Thomas J.; Richards, Christopher J.; Bhatnagar, Rhythm; Pavesio, Carlos; Agrawal, Rupesh; Jones, Philip H.

    2015-08-01

    Diabetic retinopathy (DR) is a microvascular complication of diabetes mellitus (DM) in which high blood sugar levels cause swelling, leaking and occlusions in the blood vessels of the retina, often resulting in a loss of sight. The microvascular system requires red blood cells (RBCs) to undergo significant cellular deformation in order to pass through vessels whose diameters are significantly smaller than their own. There is evidence to suggest that DM impairs the deformability of RBCs, and this loss of deformability has been associated with diabetic kidney disease (or nephropathy) - another microvascular complication of DM. However, it remains unclear whether reduced deformability of RBCs correlates with the presence of DR. Here we present an investigation into the deformability of RBCs in patients with diabetic retinopathy using optical tweezers. To extract a value for the deformability of RBCs we use a dual-trap optical tweezers set-up to stretch individual RBCs. RBCs are trapped directly (i.e. without micro-bead handles), so rotate to assume a `side-on' orientation. Video microscopy is used to record the deformation events, and shape analysis software is used to determine parameters such as initial and maximum RBC length, allowing us to calculate the deformability for each RBC. A small decrease in deformability of diabetes cells subject to this stretching protocol is observed when compared to control cells. We also report on initial results on three dimensional imaging of individual RBCs using defocussing microscopy.

  2. A combined double-tweezers and wavelength-tunable laser nanosurgery microscope

    NASA Astrophysics Data System (ADS)

    Zhu, Qingyuan; Parsa, Shahab; Shi, Linda Z.; Harsono, Marcellinus; Wakida, Nicole M.; Berns, Michael W.

    2009-08-01

    In two previous studies we have conducted combined laser subcellular microsurgery and optical trapping on chromosomes in living cells1, 2. In the latter study we used two separate microscopes, one for the trap and one for the laser scissors, thus requiring that we move the cell specimen between microscopes and relocate the irradiated cells. In the former paper we combined the 1064 nm laser trap and the 532 nm laser scissors into one microscope. However, in neither study did we have multiple traps allowing for more flexibility in application of the trapping force. In the present paper we describe a combined laser scissors and tweezers microscope that (1) has two trapping beams (both moveable via rapid scanning mirrors (FSM- 300, Newport Corp.), (2) uses a short pulsed tunable 200 fs 710-990 nm Ti:Sapphire laser for laser microsurgery, and (3) also has the option to use a 337 nm 4 ns UV laser for subcellular surgery. The two laser tweezers and either of the laser ablation beams can be used in a cell surgery experiment. The system is integrated into the robotic-controlled RoboLase system3. Experiments on mitotic chromosomes of rat kangaroo PTK2 cells are described.

  3. Measurement of particle motion in optical tweezers embedded in a Sagnac interferometer.

    PubMed

    Galinskiy, Ivan; Isaksson, Oscar; Salgado, Israel Rebolledo; Hautefeuille, Mathieu; Mehlig, Bernhard; Hanstorp, Dag

    2015-10-19

    We have constructed a counterpropagating optical tweezers setup embedded in a Sagnac interferometer in order to increase the sensitivity of position tracking for particles in the geometrical optics regime. Enhanced position determination using a Sagnac interferometer has previously been described theoretically by Taylor et al. [Journal of Optics 13, 044014 (2011)] for Rayleigh-regime particles trapped in an antinode of a standing wave. We have extended their theory to a case of arbitrarily-sized particles trapped with orthogonally-polarized counter-propagating beams. The working distance of the setup was sufficiently long to optically induce particle oscillations orthogonally to the axis of the tweezers with an auxiliary laser beam. Using these oscillations as a reference, we have experimentally shown that Sagnac-enhanced back focal plane interferometry is capable of providing an improvement of more than 5 times in the signal-to-background ratio, corresponding to a more than 30-fold improvement of the signal-to-noise ratio. The experimental results obtained are consistent with our theoretical predictions. In the experimental setup, we used a method of optical levitator-assisted liquid droplet delivery in air based on commercial inkjet technology, with a novel method to precisely control the size of droplets. PMID:26480368

  4. Natural user interface as a supplement of the holographic Raman tweezers

    NASA Astrophysics Data System (ADS)

    Tomori, Zoltan; Kanka, Jan; Kesa, Peter; Jakl, Petr; Sery, Mojmir; Bernatova, Silvie; Antalik, Marian; Zemánek, Pavel

    2014-09-01

    Holographic Raman tweezers (HRT) manipulates with microobjects by controlling the positions of multiple optical traps via the mouse or joystick. Several attempts have appeared recently to exploit touch tablets, 2D cameras or Kinect game console instead. We proposed a multimodal "Natural User Interface" (NUI) approach integrating hands tracking, gestures recognition, eye tracking and speech recognition. For this purpose we exploited "Leap Motion" and "MyGaze" low-cost sensors and a simple speech recognition program "Tazti". We developed own NUI software which processes signals from the sensors and sends the control commands to HRT which subsequently controls the positions of trapping beams, micropositioning stage and the acquisition system of Raman spectra. System allows various modes of operation proper for specific tasks. Virtual tools (called "pin" and "tweezers") serving for the manipulation with particles are displayed on the transparent "overlay" window above the live camera image. Eye tracker identifies the position of the observed particle and uses it for the autofocus. Laser trap manipulation navigated by the dominant hand can be combined with the gestures recognition of the secondary hand. Speech commands recognition is useful if both hands are busy. Proposed methods make manual control of HRT more efficient and they are also a good platform for its future semi-automated and fully automated work.

  5. Chemotaxis study using optical tweezers to observe the strength and directionality of forces of Leishmania amazonensis

    NASA Astrophysics Data System (ADS)

    Pozzo, Liliana d. Y.; Fontes, Adriana; de Thomaz, André A.; Barbosa, Luiz C.; Ayres, Diana C.; Giorgio, Selma; Cesar, Carlos L.

    2006-08-01

    The displacements of a dielectric microspheres trapped by an optical tweezers (OT) can be used as a force transducer for mechanical measurements in life sciences. This system can measure forces on the 50 femto Newtons to 200 pico Newtons range, of the same order of magnitude of a typical forces induced by flagellar motion. The process in which living microorganisms search for food and run away from poison chemicals is known is chemotaxy. Optical tweezers can be used to obtain a better understanding of chemotaxy by observing the force response of the microorganism when placed in a gradient of attractors and or repelling chemicals. This report shows such observations for the protozoa Leishmania amazomenzis, responsible for the leishmaniasis, a serious tropical disease. We used a quadrant detector to monitor the movement of the protozoa for different chemicals gradient. This way we have been able to observe both the force strength and its directionality. The characterization of the chemotaxis of these parasites can help to understand the infection mechanics and improve the diagnosis and the treatments employed for this disease.

  6. Optical trapping of a spherically symmetric sphere in the ray-optics regime: a model for optical tweezers upon cells.

    PubMed

    Chang, Yi-Ren; Hsu, Long; Chi, Sien

    2006-06-01

    Since their invention in 1986, optical tweezers have become a popular manipulation and force measurement tool in cellular and molecular biology. However, until recently there has not been a sophisticated model for optical tweezers on trapping cells in the ray-optics regime. We present a model for optical tweezers to calculate the optical force upon a spherically symmetric multilayer sphere representing a common biological cell. A numerical simulation of this model shows that not only is the magnitude of the optical force upon a Chinese hamster ovary cell significantly three times smaller than that upon a polystyrene bead of the same size, but the distribution of the optical force upon a cell is also much different from that upon a uniform particle, and there is a 30% difference in the optical trapping stiffness of these two cases. Furthermore, under a small variant condition for the refractive indices of any adjacent layers of the sphere, this model provides a simple approximation to calculate the optical force and the stiffness of an optical tweezers system. PMID:16724154

  7. Optical trapping of a spherically symmetric sphere in the ray-optics regime: a model for optical tweezers upon cells

    SciTech Connect

    Chang Yiren; Hsu Long; Chi Sien

    2006-06-01

    Since their invention in 1986, optical tweezers have become a popular manipulation and force measurement tool in cellular and molecular biology. However, until recently there has not been a sophisticated model for optical tweezers on trapping cells in the ray-optics regime. We present a model for optical tweezers to calculate the optical force upon a spherically symmetric multilayer sphere representing a common biological cell. A numerical simulation of this model shows that not only is the magnitude of the optical force upon a Chinese hamster ovary cell significantly three times smaller than that upon a polystyrene bead of the same size, but the distribution of the optical force upon a cell is also much different from that upon a uniform particle, and there is a 30% difference in the optical trapping stiffness of these two cases. Furthermore, under a small variant condition for the refractive indices of any adjacent layers of the sphere, this model provides a simple approximation to calculate the optical force and the stiffness of an optical tweezers system.

  8. Responsive supramolecular polymers based on the bis[alkynylplatinum(II)] terpyridine molecular tweezer/arene recognition motif.

    PubMed

    Tian, Yu-Kui; Shi, Yong-Gang; Yang, Zhi-Shuai; Wang, Feng

    2014-06-10

    Supramolecular polymers are constructed based on the novel bis[alkynylplatinum(II)] terpyridine molecular tweezer/pyrene recognition motif. Successive addition of anthracene as the diene and cyano-functionalized dienophile triggers the reversible supramolecular polymerization process, thus advancing the concept of utilizing Diels-Alder chemistry to access stimuli-responsive materials in compartmentalized systems.

  9. Host-guest inclusion system of mangiferin with β-cyclodextrin and its derivatives.

    PubMed

    Yang, Xuemin; Zhao, Yulin; Chen, Yunjian; Liao, Xiali; Gao, Chuanzhu; Xiao, Dan; Qin, Qixue; Yi, Dong; Yang, Bo

    2013-05-01

    The characterization, inclusion complexation behavior and binding ability of the inclusion complexes of mangiferin (MGF) with β-cyclodextrin and its derivatives (hydroxypropyl-β-cyclodextrin (HPβCD), sulfobutyl ether β-cyclodextrin (SBEβCD) and mono (6-ethylene-diamino-6-deoxy)-β-cyclodextrin (ENβCD)) were investigated in both solution and solid state by means of PL spectroscopy, (1)H and 2D NMR, XRD, TG and DSC. The results showed that the water solubility and thermal stability of MGF were significantly increased in the inclusion complex with cyclodextrins. The MGF/CDs complexes will be potentially useful for the design of a novel formulation of mangiferin for herbal medicine.

  10. Host-guest interaction of L-tyrosine with β-cyclodextrin

    NASA Astrophysics Data System (ADS)

    Shanmugam, M.; Ramesh, D.; Nagalakshmi, V.; Kavitha, R.; Rajamohan, R.; Stalin, T.

    2008-11-01

    The inclusion complexes of β-cyclodextrin (β-CD) with L-tyrosine ( L-TYN) were investigated by using spectrophotometers. The absorption and fluorescence enhancement occurs with β-CD and L-TYN forms 1:1 inclusion complex. The unusual blue shift of hydroxyl ion in the β-CD medium confirms OH groups present in the interior part of the β-CD cavity and -COOH group present in the upper part of the β-CD cavity. A mechanism is proposed to explain inclusion process. The inclusion interaction was examined and the thermodynamic parameters of inclusion process Δ G, Δ H and Δ S were determined. The results indicated that the inclusion process was an exergonic and spontaneous process. Stable solid inclusion complexes were established and characterized by FT-IR, scanning electron microscope (SEM) methods.

  11. Host-guest interaction of L-tyrosine with beta-cyclodextrin.

    PubMed

    Shanmugam, M; Ramesh, D; Nagalakshmi, V; Kavitha, R; Rajamohan, R; Stalin, T

    2008-11-01

    The inclusion complexes of beta-cyclodextrin (beta-CD) with L-tyrosine (L-TYN) were investigated by using spectrophotometers. The absorption and fluorescence enhancement occurs with beta-CD and L-TYN forms 1:1 inclusion complex. The unusual blue shift of hydroxyl ion in the beta-CD medium confirms OH groups present in the interior part of the beta-CD cavity and -COOH group present in the upper part of the beta-CD cavity. A mechanism is proposed to explain inclusion process. The inclusion interaction was examined and the thermodynamic parameters of inclusion process DeltaG, DeltaH and DeltaS were determined. The results indicated that the inclusion process was an exergonic and spontaneous process. Stable solid inclusion complexes were established and characterized by FT-IR, scanning electron microscope (SEM) methods.

  12. Characterization of folic acid/native cyclodextrins host-guest complexes in solution

    NASA Astrophysics Data System (ADS)

    Ceborska, Magdalena; Zimnicka, Magdalena; Wszelaka-Rylik, Małgorzata; Troć, Anna

    2016-04-01

    The complexation of folic acid (FA) with native cyclodextrins was studied and this process was used for the comparison of 1H NMR, ITC and ESIMS for the evaluation of association constants. The stability increases in the series: α-cyclodextrin/FA < γ-cyclodextrin/FA < β-cyclodextrin/FA. 1H NMR and ITC gave comparable results in regard to association constant values, while results obtained for MS were considerably higher due to different interactions (electrostatic instead of hydrophobic) responsible for the stabilization of the complexes. The dimerization of FA in water was also studied, as well as its impact on the process of complexation with native cyclodextrins.

  13. Insights into the Complexity of Weak Intermolecular Interactions Interfering in Host-Guest Systems.

    PubMed

    Zhang, Dawei; Chatelet, Bastien; Serrano, Eloisa; Perraud, Olivier; Dutasta, Jean-Pierre; Robert, Vincent; Martinez, Alexandre

    2015-10-01

    The recognition properties of heteroditopic hemicryptophane hosts towards anions, cations, and neutral pairs, combining both cation-π and anion-π interaction sites, were investigated to probe the complexity of interfering weak intermolecular interactions. It is suggested from NMR experiments, and supported by CASSCF/CASPT2 calculations, that the binding constants of anions can be modulated by a factor of up to 100 by varying the fluorination sites on the electron-poor aromatic rings. Interestingly, this subtle chemical modification can also reverse the sign of cooperativity in ion-pair recognition. Wavefunction calculations highlight how short- and long-range interactions interfere in this recognition process, suggesting that a disruption of anion-π interactions can occur in the presence of a co-bound cation. Such molecules can be viewed as prototypes for examining complex processes controlled by the competition of weak interactions.

  14. Pyrazine motif containing hexagonal macrocycles: synthesis, characterization, and host-guest chemistry with nitro aromatics.

    PubMed

    Bhowmick, Sourav; Chakraborty, Sourav; Das, Atanu; Nallapeta, Sivaramaiah; Das, Neeladri

    2015-09-21

    The synthesis and characterization of cationic two-dimensional metallamacrocycles having a hexagonal shape and cavity are described. Both macrocycles utilize a pyrazine motif containing an organometallic acceptor tecton with platinum(II) centers along with different donor ligands. While one macrocycle is a relatively larger [6 + 6], the other is a relatively smaller [2 + 2] polygon. A unique feature of the smaller ensemble is that it is an irregular polygon in which all six edges are not of equal length. Molecular modeling of these macrocycles confirmed the presence of hexagonal cavities. The ability of these π-electron rich macrocycles to act as potential hosts for relatively electron deficient nitroaromatics (DNT = 2,4-dinitrotoluene and PA = picric acid) has been studied using isothermal titration calorimetry (ITC) as a tool. Molecular dynamics simulation studies were subsequently performed to gain critical insight into the binding interactions between the nitroaromatic guest molecules (PA/DNT) and the ionic macrocycles reported herein.

  15. Origin of White Electroluminescence in Graphene Quantum Dots Embedded Host/Guest Polymer Light Emitting Diodes

    NASA Astrophysics Data System (ADS)

    Kyu Kim, Jung; Bae, Sukang; Yi, Yeonjin; Jin Park, Myung; Jin Kim, Sang; Myoung, Nosoung; Lee, Chang-Lyoul; Hee Hong, Byung; Hyeok Park, Jong

    2015-06-01

    Polymer light emitting diodes (PLEDs) using quantum dots (QDs) as emissive materials have received much attention as promising components for next-generation displays. Despite their outstanding properties, toxic and hazardous nature of QDs is a serious impediment to their use in future eco-friendly opto-electronic device applications. Owing to the desires to develop new types of nano-material without health and environmental effects but with strong opto-electrical properties similar to QDs, graphene quantum dots (GQDs) have attracted great interest as promising luminophores. However, the origin of electroluminescence from GQDs incorporated PLEDs is unclear. Herein, we synthesized graphene oxide quantum dots (GOQDs) using a modified hydrothermal deoxidization method and characterized the PLED performance using GOQDs blended poly(N-vinyl carbazole) (PVK) as emissive layer. Simple device structure was used to reveal the origin of EL by excluding the contribution of and contamination from other layers. The energy transfer and interaction between the PVK host and GOQDs guest were investigated using steady-state PL, time-correlated single photon counting (TCSPC) and density functional theory (DFT) calculations. Experiments revealed that white EL emission from the PLED originated from the hybridized GOQD-PVK complex emission with the contributions from the individual GOQDs and PVK emissions.

  16. Host-guest interaction between herbicide oxadiargyl and hydroxypropyl-β-cyclodextrin.

    PubMed

    Benfeito, Sofia; Rodrigues, Tiago; Garrido, Jorge; Borges, Fernanda; Garrido, E Manuela

    2013-01-01

    In the face of a growing human population and increased urbanization, the demand for pesticides will simply rise. Farmers must escalate yields on increasingly fewer farm acres. However, the risks of pesticides, whether real or perceived, may force changes in the way these chemicals are used. Scientists are working toward pest control plans that are environmentally sound, effective, and profitable. In this context the development of new pesticide formulations which may improve application effectiveness, safety, handling, and storage can be pointed out as a solution. As a contribution to the area, the microencapsulation of the herbicide oxadiargyl (OXA) in (2-hydroxypropyl)-β-cyclodextrin (HP-β-CD) was performed. The study was conducted in different aqueous media (ultrapure water and in different pH buffer solutions). In all cases an increment of the oxadiargyl solubility as a function of the HP-β-CD concentration that has been related to the formation of an inclusion complex was verified. UV-Vis and NMR experiments allowed concluding that the stoichiometry of the OXA/HP-β-CD complex formed is 1 : 1. The gathered results can be regarded as an important step for its removal from industrial effluents and/or to increase the stabilizing action, encapsulation, and adsorption in water treatment plants. PMID:24396310

  17. Host-guest interaction between pinocembrin and cyclodextrins: Characterization, solubilization and stability

    NASA Astrophysics Data System (ADS)

    Zhou, Shu-Ya; Ma, Shui-Xian; Cheng, Hui-Lin; Yang, Li-Juan; Chen, Wen; Yin, Yan-Qing; Shi, Yi-Min; Yang, Xiao-Dong

    2014-01-01

    The inclusion complexation behavior, characterization and binding ability of pinocembrin with β-cyclodextrin (β-CD) and its derivative 2-hydroxypropyl-β-cyclodextrin (HPβCD) were investigated in both solution and the solid state by means of XRD, DSC, 1H and 2D NMR and UV-vis spectroscopy. The results showed that the water solubility and thermal stability of pinocembrin were obviously increased in the inclusion complex with cyclodextrins. This satisfactory water solubility and high stability of the pinocembrin/CD complexes will be potentially useful for their application as herbal medicines or healthcare products.

  18. A study of supramolecular host-guest interaction of dothiepin and doxepin drugs with cyclodextrin macrocycles

    NASA Astrophysics Data System (ADS)

    Rajendiran, N.; Sankaranarayanan, R. K.; Saravanan, J.

    2014-06-01

    Inclusion complexation behavior of dothiepin (DOT) and doxepin (DOX) with two cyclodextrins (α-CD and β-CD) were studied by absorption, fluorescence, time resolved fluorescence, scanning electron microscope (SEM), transmission electron microscope (TEM), Fourier transformation infrared spectroscopy (FT-IR), differential scanning colorimetry (DSC), powder X-ray diffraction (PXRD), proton nuclear magnetic resonance (1H NMR) and molecular modeling methods. Absorption and fluorescence spectral studies reveal that both drugs form different types of inclusion complexes with α-CD and β-CD. DOT and DOX exhibit short life time in aqueous medium (DOT ∼ 2.29 ns, DOX ∼ 1.89 ns) and higher in CD medium (DOT:α-CD ∼ 3.45 ns, DOT:β-CD ∼ 4.84 ns, DOX:α-CD ∼ 3.55 ns and DOT:β-CD ∼ 4.33 ns). The supramolecular structure of the nano-sized sphere and agglomerate was established by TEM. Alkyl chain and aromatic ring protons of the drug molecule are entrapped in the CD nanocavities. The significant proton chemical shifts give evidence for expected inclusion complex formation. PM3 calculations suggest that the alkyl chain encapsulation is most energetically favored in α-CD. The positive free energy and entropy changes indicated that both inclusion complexation processes are non-spontaneous and entropy driven.

  19. Host-Guest Interaction between Herbicide Oxadiargyl and Hydroxypropyl-β-Cyclodextrin

    PubMed Central

    Benfeito, Sofia; Borges, Fernanda; Garrido, E. Manuela

    2013-01-01

    In the face of a growing human population and increased urbanization, the demand for pesticides will simply rise. Farmers must escalate yields on increasingly fewer farm acres. However, the risks of pesticides, whether real or perceived, may force changes in the way these chemicals are used. Scientists are working toward pest control plans that are environmentally sound, effective, and profitable. In this context the development of new pesticide formulations which may improve application effectiveness, safety, handling, and storage can be pointed out as a solution. As a contribution to the area, the microencapsulation of the herbicide oxadiargyl (OXA) in (2-hydroxypropyl)-β-cyclodextrin (HP-β-CD) was performed. The study was conducted in different aqueous media (ultrapure water and in different pH buffer solutions). In all cases an increment of the oxadiargyl solubility as a function of the HP-β-CD concentration that has been related to the formation of an inclusion complex was verified. UV-Vis and NMR experiments allowed concluding that the stoichiometry of the OXA/HP-β-CD complex formed is 1 : 1. The gathered results can be regarded as an important step for its removal from industrial effluents and/or to increase the stabilizing action, encapsulation, and adsorption in water treatment plants. PMID:24396310

  20. Comparison of host-guest Langmuir-Blodgett multilayer formation by two different amphiphilic cyclodextrins

    SciTech Connect

    Parazak, D.P.; Khan, A.R.; D`Souza, V.T.; Stine, K.J.

    1996-08-07

    We report here our results for Langmuir monolayers of the derivatives of cyclodextrin shown: hexakis(6-deoxy-6-dodecylamino)-{alpha}-cyclodextrin (1a), heptakis(6-deoxy-6-dodecylamino)-{beta}-cyclodextrin (1b), and heptakis(6-deoxy-6-dodecylthio)-{beta}-cyclodextrin (2b ), which was found to be partially substituted. Langmuir films of these derivatives were examined using {Pi}-A isotherm measurements and Brewster angle microscopy. Langmuir-Blodgett (LB) multilayer films of these derivatives were deposited from subphases containing p-nitrophenol to determine the extent of incorporation of the guest molecule in the LB film. The transfer ratios of the film exhibited a noteworthy evolution with the transfer pressure. The variation in the extent of guest molecule incorporation is discussed and compared with the binding behavior in solution of unmodified cyclodextrins. 29 refs., 4 figs.

  1. Bioinspired Molecular Lantern: Tuning the Firefly Oxyluciferin Emission with Host-Guest Chemistry.

    PubMed

    Saleh, Na'il; Suwaid, Abdul Rahman Ba; Alhalabi, Ahmad; Abuibaid, Ahmed Z A; Maltsev, Oleg V; Hintermann, Lukas; Naumov, Panče

    2016-08-11

    Fireflies generate flashes of visible light via luciferase-catalyzed chemiexcitation of the substrate (luciferin) to the first excited state of the emitter (oxyluciferin). Microenvironment effects are often invoked to explain the effects of the luciferase active pocket on the emission; however, the exceedingly complex spectrochemistry and synthetic burdens have precluded elucidation of the nature of these interactions. To decipher the effects of microenvironment on the light emission, here the hydrophobic interior of cucurbit[7]uril (CB7) is used to mimic the nonpolar active pocket of luciferase. The hydrophobic interior of CB7 induces shifts of the ground-state pKas by 1.9-2.5 units to higher values. Upon sequestration, the emission maxima of neutral firefly oxyluciferin and its conjugate monodeprotonated base are blue-shifted by 40 and 39 nm, respectively, resulting in visual color changes of the emitted light. PMID:27442808

  2. Fluorescence detecting of paraquat using host-guest chemistry with cucurbit[8]uril

    NASA Astrophysics Data System (ADS)

    Sun, Shiguo; Li, Fusheng; Liu, Fengyu; Wang, Jitao; Peng, Xiaojun

    2014-01-01

    Paraquat (PQ) is one of the most widely used herbicides in the world, which has a good occupational safety record when used properly. While, it presents high mortality index after intentional exposure. Accidental deaths and suicides from PQ ingestion are relatively common in developing countries with an estimated 300,000 deaths occurring in the Asia-Pacific region alone each year, and there are no specific antidotes. Good predictors of outcome and prognosis may be plasma and urine testing within the first 24 h of intoxication. A fluorescence enhancement of approximately 30 times was seen following addition of PQ to a solution of the supramolecular compound 2MB@CB[8], which comprised two methylene blue (MB) molecules within one cucurbit[8]uril (CB[8]) host molecule. The fluorescence intensity was linearly proportional to the amount of PQ added over the concentration range 2.4 × 10-10 M-2.5 × 10-4 M. The reaction also occurred in living cells and within live mice.

  3. Catalytic polymeric nanocomposites via cucurbit[n]uril host-guest interactions

    NASA Astrophysics Data System (ADS)

    Wu, Yuchao; Lan, Yang; Liu, Ji; Scherman, Oren A.

    2015-08-01

    Polymeric nanocomposites were prepared by using cucurbit[7]uril as a `supramolecular anchor', as well as stabilising ligand to immobilise catalytic transition-metal nanoparticles on the surface of methyl viologen-bearing polymeric colloids. This facile and spontaneous supramolecular approach allows for control over size, morphology and composition of the nanocomposites. The small metallic nanoparticles impart the nanocomposites with great potential in catalysis.Polymeric nanocomposites were prepared by using cucurbit[7]uril as a `supramolecular anchor', as well as stabilising ligand to immobilise catalytic transition-metal nanoparticles on the surface of methyl viologen-bearing polymeric colloids. This facile and spontaneous supramolecular approach allows for control over size, morphology and composition of the nanocomposites. The small metallic nanoparticles impart the nanocomposites with great potential in catalysis. Electronic supplementary information (ESI) available. See DOI: 10.1039/C5NR03647J

  4. Temporal and Triggered Evolution of Host-Guest Characteristics in Amphiphilic Polymer Assemblies.

    PubMed

    Rangadurai, Poornima; Molla, Mijanur Rahaman; Prasad, Priyaa; Caissy, Matthew; Thayumanavan, S

    2016-06-22

    An amphiphilic polymer with cleavable side chain and main chain functional groups has been designed and synthesized. Specific cleavage of either of its functional groups was found to have an effect on the morphology of the assembly. Degradation of the main chain is shown to cause morphology of the supramolecular assembly to evolve with time from a micelle-like assembly to a vesicular assembly. On the other hand, stimulus-induced cleavage of the side chains causes these nanoassemblies to disassemble. These temporal (main chain) and triggered (side chain) degradation processes have implications in the design of degradable polymers as supramolecular scaffolds for biological applications. PMID:27258854

  5. Supramolecular chiral host-guest nanoarchitecture induced by the selective assembly of barbituric acid derivative enantiomers.

    PubMed

    Sun, Xiaonan; Silly, Fabien; Maurel, Francois; Dong, Changzhi

    2016-10-21

    Barbituric acid derivatives are prochiral molecules, i.e. they are chiral upon adsorption on surfaces. Scanning tunneling microscopy reveals that barbituric acid derivatives self-assemble into a chiral guest-host supramolecular architecture at the solid-liquid interface on graphite. The host nanoarchitecture has a sophisticated wavy shape pattern and paired guest molecules are nested insides the cavities of the host structure. Each unit cell of the host structure is composed of both enantiomers with a ratio of 1:1. Furthermore, the wavy patterns of the nanoarchitecture are formed from alternative appearance of left- and right-handed chiral building blocks, which makes the network heterochiral. The functional guest-host nanoarchitecture is the result of two-dimensional chiral amplification from single enantiomers to organizational heterochiral supramolecular self-assembly. PMID:27623155

  6. Bioinspired Molecular Lantern: Tuning the Firefly Oxyluciferin Emission with Host-Guest Chemistry.

    PubMed

    Saleh, Na'il; Suwaid, Abdul Rahman Ba; Alhalabi, Ahmad; Abuibaid, Ahmed Z A; Maltsev, Oleg V; Hintermann, Lukas; Naumov, Panče

    2016-08-11

    Fireflies generate flashes of visible light via luciferase-catalyzed chemiexcitation of the substrate (luciferin) to the first excited state of the emitter (oxyluciferin). Microenvironment effects are often invoked to explain the effects of the luciferase active pocket on the emission; however, the exceedingly complex spectrochemistry and synthetic burdens have precluded elucidation of the nature of these interactions. To decipher the effects of microenvironment on the light emission, here the hydrophobic interior of cucurbit[7]uril (CB7) is used to mimic the nonpolar active pocket of luciferase. The hydrophobic interior of CB7 induces shifts of the ground-state pKas by 1.9-2.5 units to higher values. Upon sequestration, the emission maxima of neutral firefly oxyluciferin and its conjugate monodeprotonated base are blue-shifted by 40 and 39 nm, respectively, resulting in visual color changes of the emitted light.

  7. Single-Molecule Conductance of Viologen-Cucurbit[8]uril Host-Guest Complexes.

    PubMed

    Zhang, Wei; Gan, Shiyu; Vezzoli, Andrea; Davidson, Ross J; Milan, David C; Luzyanin, Konstantin V; Higgins, Simon J; Nichols, Richard J; Beeby, Andrew; Low, Paul J; Li, Buyi; Niu, Li

    2016-05-24

    The local molecular environment is a critical factor which should be taken into account when measuring single-molecule electrical properties in condensed media or in the design of future molecular electronic or single molecule sensing devices. Supramolecular interactions can be used to control the local environment in molecular assemblies and have been used to create microenvironments, for instance, for chemical reactions. Here, we use supramolecular interactions to create microenvironments which influence the electrical conductance of single molecule wires. Cucurbit[8]uril (CB[8]) with a large hydrophobic cavity was used to host the viologen (bipyridinium) molecular wires forming a 1:1 supramolecular complex. Significant increases in the viologen wire single molecule conductances are observed when it is threaded into CB[8] due to large changes of the molecular microenvironment. The results were interpreted within the framework of a Marcus-type model for electron transfer as arising from a reduction in outer-sphere reorganization energy when the viologen is confined within the hydrophobic CB[8] cavity. PMID:27055002

  8. Does Size Really Matter? The Steric Isotope Effect in a Supramolecular Host?Guest Exchange Reaction

    SciTech Connect

    Mugridge, Jeffrey; Bergman, Robert; Raymond, Kenneth

    2010-01-29

    Isotope effects (IEs), which arise from differences in zero point energies (ZPEs) between a parent and isotopically substituted bond, have been used extensively by chemists to probe molecular interactions and reactivity. Due to the anharmonicity of the C-H/D vibrational potential energy function and the lower ZPE of a C-D bond, the average C-D bond length is typically {approx}0.005 {angstrom} shorter than an equivalent C-H bond. It is this difference in size that is often invoked to explain the observation of secondary, inverse kinetic isotope effects (KIEs) in chemical processes which proceed through a sterically strained transition state. This so-called 'steric isotope effect' (SIE) has been observed in processes such as the racemization of ortho-substituted biphenyls[6] and phenanthrenes, ring flipping of cyclophanes, and more recently in the deslipping of rotaxanes, where substitution of the sterically less demanding deuterium for protium results in rate accelerations for these processes. Herein, we use deuterium substitution in a cationic guest molecule to probe the sensitivity limits of the guest exchange process from a highly-charged supramolecular host.

  9. Host-guest interaction manipulated self-assembly of pyridinium-tailored naphthalene.

    PubMed

    Wang, Peiyi; Lin, Yuan; Smith, Mark; Feng, Sheng; Song, Baoan; Yang, Song; Hu, Jun

    2014-10-14

    Host–guest interactions are employed to manipulate the assembled morphology of an amphiphile, 2-NP, which contains an electron-rich naphthalene group and an electron-deficient pyridinium cation linked with a flexible alkyl arm. By encapsulating the pyridinium and the naphthalene group of 2-NP into the cavity of cucurbit[8]uril (CB[8]), fluorescence-enhanced microsheets were formed.

  10. Host-guest encapsulation of materials by assembled virus protein cages

    NASA Astrophysics Data System (ADS)

    Douglas, Trevor; Young, Mark

    1998-05-01

    Self-assembled cage structures of nanometre dimensions can be used as constrained environments for the preparation of nanostructured materials, and the encapsulation of guest molecules, with potential applications in drug delivery and catalysis. In synthetic systems the number of subunits contributing to cage structures is typically rather small,. But the protein coats of viruses (virions) commonly comprise hundreds of subunits that self-assemble into a cage for transporting viral nucleic acids. Many virions, moreover, can undergo reversible structural changes that open or close gated pores to allow switchable access to their interior. Here we show that such a virion - that of the cowpea chlorotic mottle virus - can be used as a host for the synthesis of materials. We report the mineralization of two polyoxometalate species (paratungstate and decavanadate) and the encapsulation of an anionic polymer inside this virion, controlled by pH-dependent gating of the virion's pores. The diversity in size and shape of such virus particles make this a versatile strategy for materials synthesis and molecular entrapment.

  11. Design and comparison of exchange spectroscopy approaches to cryptophane-xenon host-guest kinetics

    NASA Astrophysics Data System (ADS)

    Korchak, Sergey; Kilian, Wolfgang; Schröder, Leif; Mitschang, Lorenz

    2016-04-01

    Exchange spectroscopy is used in combination with a variation of xenon concentration to disentangle the kinetics of the reversible binding of xenon to cryptophane-A. The signal intensity of either free or crytophane-bound xenon decays in a manner characteristic of the underlying exchange reactions when the spins in the other pool are perturbed. Three experimental approaches, including the well-known Hyper-CEST method, are shown to effectively entail a simple linear dependence of the signal depletion rate, or of a related quantity, on free xenon concentration. This occurs when using spin pool saturation or inversion followed by free exchange. The identification and quantification of contributions to the binding kinetics is then straightforward: in the depletion rate plot, the intercept at the vanishing free xenon concentration represents the kinetic rate coefficient for xenon detachment from the host by dissociative processes while the slope is indicative of the kinetic rate coefficient for degenerate exchange reactions. Comparing quantified kinetic rates for hyperpolarized xenon in aqueous solution reveals the high accuracy of each approach but also shows differences in the precision of the numerical results and in the requirements for prior knowledge. Because of their broad range of applicability the proposed exchange spectroscopy experiments can be readily used to unravel the kinetics of complex formation of xenon with host molecules in the various situations appearing in practice.

  12. Origin of White Electroluminescence in Graphene Quantum Dots Embedded Host/Guest Polymer Light Emitting Diodes

    PubMed Central

    Kyu Kim, Jung; Bae, Sukang; Yi, Yeonjin; Jin Park, Myung; Jin Kim, Sang; Myoung, NoSoung; Lee, Chang-Lyoul; Hee Hong, Byung; Hyeok Park, Jong

    2015-01-01

    Polymer light emitting diodes (PLEDs) using quantum dots (QDs) as emissive materials have received much attention as promising components for next-generation displays. Despite their outstanding properties, toxic and hazardous nature of QDs is a serious impediment to their use in future eco-friendly opto-electronic device applications. Owing to the desires to develop new types of nano-material without health and environmental effects but with strong opto-electrical properties similar to QDs, graphene quantum dots (GQDs) have attracted great interest as promising luminophores. However, the origin of electroluminescence from GQDs incorporated PLEDs is unclear. Herein, we synthesized graphene oxide quantum dots (GOQDs) using a modified hydrothermal deoxidization method and characterized the PLED performance using GOQDs blended poly(N-vinyl carbazole) (PVK) as emissive layer. Simple device structure was used to reveal the origin of EL by excluding the contribution of and contamination from other layers. The energy transfer and interaction between the PVK host and GOQDs guest were investigated using steady-state PL, time-correlated single photon counting (TCSPC) and density functional theory (DFT) calculations. Experiments revealed that white EL emission from the PLED originated from the hybridized GOQD-PVK complex emission with the contributions from the individual GOQDs and PVK emissions. PMID:26067060

  13. Supramolecular chiral host-guest nanoarchitecture induced by the selective assembly of barbituric acid derivative enantiomers

    NASA Astrophysics Data System (ADS)

    Sun, Xiaonan; Silly, Fabien; Maurel, Francois; Dong, Changzhi

    2016-10-01

    Barbituric acid derivatives are prochiral molecules, i.e. they are chiral upon adsorption on surfaces. Scanning tunneling microscopy reveals that barbituric acid derivatives self-assemble into a chiral guest-host supramolecular architecture at the solid-liquid interface on graphite. The host nanoarchitecture has a sophisticated wavy shape pattern and paired guest molecules are nested insides the cavities of the host structure. Each unit cell of the host structure is composed of both enantiomers with a ratio of 1:1. Furthermore, the wavy patterns of the nanoarchitecture are formed from alternative appearance of left- and right-handed chiral building blocks, which makes the network heterochiral. The functional guest-host nanoarchitecture is the result of two-dimensional chiral amplification from single enantiomers to organizational heterochiral supramolecular self-assembly.

  14. Ink-jet printing of host-guest systems based on acrylates with fluorescent dopants

    NASA Astrophysics Data System (ADS)

    Bollgruen, Patrick; Gleissner, Uwe; Megnin, Christof; Mager, Dario; Korvink, Jan; Hanemann, Thomas

    2016-04-01

    We present two ink-jet printable, optically active material systems that point towards flexible foil-based optical systems independent of any electrical elements or physical connections. The materials are based on a UV-curable monomer doped with europium and diphenylantracene, resulting in red (610 nm) and blue (430 nm) fluorescence excited by UV light. Additionally, ethylene glycol dimethacrylate (EGDMA) is used to tune the viscosity to 10 mPas via a print-head temperature of 50 °C, as required by the ink-jet print-head. When illuminated with 1.5 W/cm2, the measured intensity of the europium is in the range of 1 mW/cm2. By printing these materials on PMMA foil, we can create fluorescent tracks with a feature size well below 100 μm that could serve as light sources within a planar optronic system.

  15. Optical Detection of Aqueous Phase Analytes via Host-Guest Interactions on a Lipid Membrane Surface

    SciTech Connect

    Sasaki, D.Y.; Waggoner, T.A.

    1999-01-11

    The organization and assembly of molecules in cellular membranes is orchestrated through the recognition and binding of specific chemical signals. A simplified version of the cellular membrane system has been developed using a synthetically prepared membrane receptor incorporated into a biologically derived lipid bilayer. Through an interplay of electrostatic and van der Wards interactions, aggregation or dispersion of molecular components could be executed on command using a specific chemical signal. A pyrene fluorophore was used as an optical probe to monitor the aggregational state of the membrane receptors in the bilayer matrix. The pyrene excimer emission to monomer emission (E/M) intensity ratio gave a relative assessment of the local concentration of receptors in the membrane. Bilayers were prepared with receptors selective for the divalent metal ions of copper, mercury, and lead. Addition of the metal ions produced a rapid dispersion of aggregated receptor components at nano- to micro-molar concentrations. The process was reversible by sequestering the metal ions with EDTA. Receptors for proteins and polyhistidine were also prepared and incorporated into phosphatidylcholine lipid bilayers. In this case, the guest molecules bound to the membrane through multiple points of interaction causing aggregation of initially dispersed receptor molecules. The rapid, selective, and sensitive fluorescence optical response of these lipid assemblies make them attractive in sensor applications for aqueous phase metal ions and polypeptides.

  16. Energy Landscape of Alginate-Epimerase Interactions Assessed by Optical Tweezers and Atomic Force Microscopy.

    PubMed

    Håti, Armend Gazmeno; Aachmann, Finn Lillelund; Stokke, Bjørn Torger; Skjåk-Bræk, Gudmund; Sletmoen, Marit

    2015-01-01

    Mannuronan C-5 epimerases are a family of enzymes that catalyze epimerization of alginates at the polymer level. This group of enzymes thus enables the tailor-making of various alginate residue sequences to attain various functional properties, e.g. viscosity, gelation and ion binding. Here, the interactions between epimerases AlgE4 and AlgE6 and alginate substrates as well as epimerization products were determined. The interactions of the various epimerase-polysaccharide pairs were determined over an extended range of force loading rates by the combined use of optical tweezers and atomic force microscopy. When studying systems that in nature are not subjected to external forces the access to observations obtained at low loading rates, as provided by optical tweezers, is a great advantage since the low loading rate region for these systems reflect the properties of the rate limiting energy barrier. The AlgE epimerases have a modular structure comprising both A and R modules, and the role of each of these modules in the epimerization process were examined through studies of the A- module of AlgE6, AlgE6A. Dynamic strength spectra obtained through combination of atomic force microscopy and the optical tweezers revealed the existence of two energy barriers in the alginate-epimerase complexes, of which one was not revealed in previous AFM based studies of these complexes. Furthermore, based on these spectra estimates of the locations of energy transition states (xβ), lifetimes in the absence of external perturbation (τ0) and free energies (ΔG#) were determined for the different epimerase-alginate complexes. This is the first determination of ΔG# for these complexes. The values determined were up to 8 kBT for the outer barrier, and smaller values for the inner barriers. The size of the free energies determined are consistent with the interpretation that the enzyme and substrate are thus not tightly locked at all times but are able to relocate. Together with the

  17. Energy Landscape of Alginate-Epimerase Interactions Assessed by Optical Tweezers and Atomic Force Microscopy

    PubMed Central

    Håti, Armend Gazmeno; Aachmann, Finn Lillelund; Stokke, Bjørn Torger; Skjåk-Bræk, Gudmund; Sletmoen, Marit

    2015-01-01

    Mannuronan C-5 epimerases are a family of enzymes that catalyze epimerization of alginates at the polymer level. This group of enzymes thus enables the tailor-making of various alginate residue sequences to attain various functional properties, e.g. viscosity, gelation and ion binding. Here, the interactions between epimerases AlgE4 and AlgE6 and alginate substrates as well as epimerization products were determined. The interactions of the various epimerase–polysaccharide pairs were determined over an extended range of force loading rates by the combined use of optical tweezers and atomic force microscopy. When studying systems that in nature are not subjected to external forces the access to observations obtained at low loading rates, as provided by optical tweezers, is a great advantage since the low loading rate region for these systems reflect the properties of the rate limiting energy barrier. The AlgE epimerases have a modular structure comprising both A and R modules, and the role of each of these modules in the epimerization process were examined through studies of the A- module of AlgE6, AlgE6A. Dynamic strength spectra obtained through combination of atomic force microscopy and the optical tweezers revealed the existence of two energy barriers in the alginate-epimerase complexes, of which one was not revealed in previous AFM based studies of these complexes. Furthermore, based on these spectra estimates of the locations of energy transition states (xβ), lifetimes in the absence of external perturbation (τ0) and free energies (ΔG#) were determined for the different epimerase–alginate complexes. This is the first determination of ΔG# for these complexes. The values determined were up to 8 kBT for the outer barrier, and smaller values for the inner barriers. The size of the free energies determined are consistent with the interpretation that the enzyme and substrate are thus not tightly locked at all times but are able to relocate. Together with the

  18. Characterization of the mechanical properties of HL-1 cardiomyocytes with high throughput magnetic tweezers

    SciTech Connect

    Chen, La; Maybeck, Vanessa; Offenhäusser, Andreas; Krause, Hans-Joachim

    2015-08-03

    We characterized the mechanical properties of cardiomyocyte-like HL-1 cells using our recently developed multi-pole magnetic tweezers. With the optimized design, both high force and high throughput are achieved at the same time. Force up to 100 pN can be applied on a 1 μm diameter superparamagnetic bead in a workspace with 60 μm radius, which is encircled symmetrically by 3 sharp magnetic tips. By adjusting the coil currents, both the strength and direction of force can be controlled. The result shows that both viscosity and shear elastic modulus of HL-1 cells exhibit an approximately log-normal distribution. The cells became stiffer as they matured, consistent with a transition from proliferating cells to contractile muscle tissue. Moreover, the mechanical properties of HL-1 cells show high heterogeneity, which agrees well with their physiological structure.

  19. Floating electrode optoelectronic tweezers: Light-driven dielectrophoretic droplet manipulation in electrically insulating oil medium

    NASA Astrophysics Data System (ADS)

    Park, Sungyong; Pan, Chenlu; Wu, Ting-Hsiang; Kloss, Christoph; Kalim, Sheraz; Callahan, Caitlin E.; Teitell, Michael; Chiou, Eric P. Y.

    2008-04-01

    We report an optical actuation mechanism, floating electrode optoelectronic tweezers (FEOET). FEOET enables light-driven transport of aqueous droplets immersed in electrically insulating oil on a featureless photoconductive glass layer with direct optical images. We demonstrate that a 681μm de-ionized water droplet immersed in corn oil medium is actuated by a 3.21μW laser beam with an average intensity as low as 4.08μW/mm2 at a maximum speed of 85.1μm/s on a FEOET device. FEOET provides a promising platform for massively parallel droplet manipulation with optical images on low cost, silicon-coated glass. The FEOET device structure, fabrication, working principle, numerical simulations, and operational results are presented in this letter.

  20. Force versus position profiles of HeLa cells trapped in phototransistor-based optoelectronic tweezers

    NASA Astrophysics Data System (ADS)

    Neale, Steven L.; Ohta, Aaron T.; Hsu, Hsan-Yin; Valley, Justin K.; Jamshidi, Arash; Wu, Ming C.

    2009-02-01

    Phototransistor-based Optoelectronic Tweezers (Ph-OET) enables optical manipulation of microscopic particles in physiological buffer solutions by creating electrical field gradients around them. A spatial light pattern is created by a DMD based projector focused through a microscope objective onto the phototransistor. In this paper we look into what differences there are in the trap stiffness profiles of HeLa cells trapped by Ph-OET compared to previous a-Si based OET devices. We find that the minimum trap size for a HeLa cell using a phototransistor with pixel pitch 10.35μm is 24.06μm in diameter which can move cells at 20μms-1 giving a trap stiffness of 8.38 x 10-7 Nm-1.

  1. Studies of cochlear outer hair cell membrane mechanics using optical tweezers

    NASA Astrophysics Data System (ADS)

    Murdock, David R.; Ermilov, Sergey A.; Brownell, William E.; Anvari, Bahman

    2003-06-01

    An optical tweezers system was used to study the mechanical characteristics of outer hair cell (OHC) and human embryonic kidney (HEK) cell plasma membranes. The effect of the cationic amphipath chlorpromazine (CPZ) on the equilibrium tethering force, (Feq) force relaxation time constant,(τ) and effective membrane viscosity (ηeff) was measured. The Feq for the OHC lateral wall plasma membrane was ~60 pN and was unchanged by addition of CPZ. A significantly greater τ value was observed in CPZ-treated OHCs (30.5 +/- 12.6 s) than in control OHCs (19.0 +/- 13.2 s). The Feq and τ values for control HEK cells were >60% lower than the respective OHC values but increased by ~3 times following CPZ addition. Effective viscosity ranged between 1.49-1.81 pN•s/μm for CPZ-treated OHCs. This represents a decrease from reported control OHC membrane viscosities.

  2. Effect of ionic strength on electrically evoked membrane tether force: an optical tweezers study

    NASA Astrophysics Data System (ADS)

    Qian, Feng; Brownell, William E.; Anvari, Bahman

    2004-10-01

    We have investigated the effect of ionic strength on electrically evoked membrane tether force using optical tweezers. Membrane tethers from cochlear outer hair cells (OHCs) and human embryonic kidney (HEK) cells exhibited mechanical response to applied voltage stimuli over a wide frequency range. The electrically evoked variations in the tether force were probed by an optically-trapped microsphere, the image of which was projected on a quadrant photodiode for dynamic measurement of its displacements. Compared to normal saline (140mM NaCl), low ionic-strength solution (10mM NaCl) blocked the electrically evoked tether force for both OHCs and HEK cells. As the Debye length for membrane bilayer was estimated to increase from approximately 0.75nm to 1.88nm, the internal repulsive pressure of the membrane tethers rose consequently, resulting in the enlargement in the equilibrium tether diameter and the decrease in the tether force.

  3. Tuning the size and configuration of nanocarbon microcapsules: aqueous method using optical tweezers

    PubMed Central

    Frusawa, Hiroshi; Matsumoto, Youei

    2014-01-01

    To date, optical manipulation techniques for aqueous dispersions have been developed that deposit and/or transport nanoparticles not only for fundamental studies of colloidal dynamics, but also for either creating photonic devices or allowing accurate control of liquids on micron scales. Here, we report that optical tweezers (OT) system is able to direct three-dimensional assembly of graphene, graphite, and carbon nanotubes (CNT) into microcapsules of hollow spheres. The OT technique facilitates both to visualize the elasticity of a CNT microcapsule and to arrange a triplet of identical graphene microcapsules in aqueous media. Furthermore, the similarity of swelling courses has been found over a range of experimental parameters such as nanocarbon species, the power of the incident light, and the suspension density. Thanks to the universality in evolutions of rescaled capsule size, we can precisely control the size of various nanocarbon microcapsules by adjusting the duration time of laser emission. PMID:24509866

  4. Rapid feedback control and stabilization of an optical tweezers with a budget microcontroller

    NASA Astrophysics Data System (ADS)

    Nino, Daniel; Wang, Haowei; Milstein, Joshua N.

    2014-09-01

    Laboratories ranging the scientific disciplines employ feedback control to regulate variables within their experiments, from the flow of liquids within a microfluidic device to the temperature within a cell incubator. We have built an inexpensive, yet fast and rapidly deployed, feedback control system that is straightforward and flexible to implement from a commercially available Arduino Due microcontroller. This is in comparison with the complex, time-consuming and often expensive electronics that are commonly implemented. As an example of its utility, we apply our feedback controller to the task of stabilizing the main trapping laser of an optical tweezers. The feedback controller, which is inexpensive yet fast and rapidly deployed, was implemented from hacking an open source Arduino Due microcontroller. Our microcontroller based feedback system can stabilize the laser intensity to a few tenths of a per cent at 200 kHz, which is an order of magnitude better than the laser's base specifications, illustrating the utility of these devices.

  5. Robert Feulgen Prize Lecture. Laser tweezers and multiphoton microscopes in life sciences.

    PubMed

    König, K

    2000-08-01

    Near infrared (NIR) laser microscopy enables optical micromanipulation, piconewton force determination, and sensitive fluorescence studies by laser tweezers. Otherwise, fluorescence images with high spatial and temporal resolution of living cells and tissues can be obtained via non-resonant fluorophore excitation with multiphoton NIR laser scanning microscopes. Furthermore, NIR femtosecond laser pulses at TW/cm2 intensities can be used to realize non-invasive contact-free surgery of nanometer-sized structures within living cells and tissues. Applications of these novel versatile NIR laser-based tools for the determination of motility forces, coenzyme and chlorophyll imaging, three-dimensional multigene detection, non-invasive optical sectioning of tissues ("optical biopsy"), functional protein imaging, and nanosurgery of chromosomes are described.

  6. Evaluating the toxic effect of an antimicrobial agent on single bacterial cells with optical tweezers

    PubMed Central

    Samadi, Akbar; Zhang, Chensong; Chen, Joseph; Reihani, S. N. S.; Chen, Zhigang

    2014-01-01

    We implement an optical tweezers technique to assess the effects of chemical agents on single bacterial cells. As a proof of principle, the viability of a trapped Escherichia coli bacterium is determined by monitoring its flagellar motility in the presence of varying concentrations of ethyl alcohol. We show that the “killing time” of the bacterium can be effectively identified from the correlation statistics of the positional time series recorded from the trap, while direct quantification from the time series or associated power spectra is intractable. Our results, which minimize the lethal effects of bacterial photodamage, are consistent with previous reports of ethanol toxicity that used conventional culture-based methods. This approach can be adapted to study other pairwise combinations of drugs and motile bacteria, especially to measure the response times of single cells with better precision. PMID:25657879

  7. Microfluidic platform combining droplets and magnetic tweezers: application to HER2 expression in cancer diagnosis

    PubMed Central

    Ferraro, Davide; Champ, Jérôme; Teste, Bruno; Serra, Marco; Malaquin, Laurent; Viovy, Jean-Louis; de Cremoux, Patricia; Descroix, Stephanie

    2016-01-01

    The development of precision medicine, together with the multiplication of targeted therapies and associated molecular biomarkers, call for major progress in genetic analysis methods, allowing increased multiplexing and the implementation of more complex decision trees, without cost increase or loss of robustness. We present a platform combining droplet microfluidics and magnetic tweezers, performing RNA purification, reverse transcription and amplification in a fully automated and programmable way, in droplets of 250nL directly sampled from a microtiter-plate. This platform decreases sample consumption about 100 fold as compared to current robotized platforms and it reduces human manipulations and contamination risk. The platform’s performance was first evaluated on cell lines, showing robust operation on RNA quantities corresponding to less than one cell, and then clinically validated with a cohort of 21 breast cancer samples, for the determination of their HER2 expression status, in a blind comparison with an established routine clinical analysis. PMID:27157697

  8. Measurement of PLGA-NP interaction with single smooth muscle cells using optical tweezers

    NASA Astrophysics Data System (ADS)

    Gu, Ling; Mondal, Argha; Homayoni, Homa; Nguyen, Kytai; Mohanty, Samarendra

    2012-10-01

    For intervention of cardiovascular diseases, biodegradable and biocompatible, poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NP) are emerging as agents of choice for controlled and targeted drug delivery. Therefore development of PLGA-NP with optimal physico-chemical properties will allow efficient binding and thus delivery of drug to targeted cells under various patho-physiological conditions. The force kinetics and its dependence on size of the NPs will be crucial for designing the NPs. Since optical tweezers allow non-contact, highly sensitive force measurement with high spatial and temporal resolution, we utilized it for studying interaction forces between magnetic PLGA nanoparticles with smooth muscle cells (SMC). In order to investigate effect of size, interaction force for 200 to 1100nm PLGA NP was measured. For similar interaction duration, the force was found to be higher with increase in size. The rupture force was found to depend on time of interaction of SMC with NPs.

  9. Simultaneous detection of rotational and translational motion in optical tweezers by measurement of backscattered intensity.

    PubMed

    Roy, Basudev; Bera, Sudipta K; Banerjee, Ayan

    2014-06-01

    We describe a simple yet powerful technique of simultaneously measuring both translational and rotational motion of mesoscopic particles in optical tweezers by measuring the backscattered intensity on a quadrant photodiode (QPD). While the measurement of translational motion by taking the difference of the backscattered intensity incident on adjacent quadrants of a QPD is well known, we demonstrate that rotational motion can be measured very precisely by taking the difference between the diagonal quadrants. The latter measurement eliminates the translational component entirely and leads to a detection sensitivity of around 50 mdeg at S/N of 2 for angular motion of a driven microrod. The technique is also able to resolve the translational and rotational Brownian motion components of the microrod in an unperturbed trap and can be very useful in measuring translation-rotation coupling of micro-objects induced by hydrodynamic interactions.

  10. Micro-particle manipulation by single beam acoustic tweezers based on hydrothermal PZT thick film

    PubMed Central

    Zhu, Benpeng; Xu, Jiong; Li, Ying; Wang, Tian; Xiong, Ke; Lee, Changyang; Yang, Xiaofei; Shiiba, Michihisa; Takeuchi, Shinichi; Zhou, Qifa; Shung, K. Kirk

    2016-01-01

    Single-beam acoustic tweezers (SBAT), used in laboratory-on-a-chip (LOC) device has promising implications for an individual micro-particle contactless manipulation. In this study, a freestanding hydrothermal PZT thick film with excellent piezoelectric property (d33 = 270pC/N and kt = 0.51) was employed for SBAT applications and a press-focusing technology was introduced. The obtained SBAT, acting at an operational frequency of 50MHz, a low f-number (∼0.9), demonstrated the capability to trap and manipulate a micro-particle sized 10μm in the distilled water. These results suggest that such a device has great potential as a manipulator for a wide range of biomedical and chemical science applications. PMID:27014504

  11. Custom-Built Optical Tweezers for Locally Probing the Viscoelastic Properties of Cancer Cells

    NASA Astrophysics Data System (ADS)

    Tavano, Federica; Bonin, Serena; Pinato, Giulietta; Stanta, Giorgio; Cojoc, Dan

    2011-07-01

    We report a home built optical tweezers setup to investigate the mechanism of the membrane tether formation from single cells in vitro. Using an optically trapped microbead as probe, we have determined the force-elongation curve during tether formation and extracted several parameters characterizing the viscoelastic behavior of the cell membrane: tether stiffness, force, and viscosity. Breast cancer MDA-MB-231 cells have been studied in two different conditions, at room and physiological temperatures, showing a strong temperature dependence of the visoelastic properties of the cell membrane. To get detailed inside information about the tether formation mechanism we have extended the analysis of the force-elongation curves fitting them with a Kelvin model. These preliminary results are part of a larger project of whose goal is to compare the viscoelastic properties of several types of cancer cell lines, characterized by different aggressiveness and metastatic potential.

  12. Optically-driven red blood cell rotor in linearly polarized laser tweezers

    NASA Astrophysics Data System (ADS)

    Khan, Manas; Mohanty, Samarendra K.; Sood, A. K.

    2005-11-01

    We have constructed a dual trap optical tweezers set-up around an inverted microscope where both the traps can be independently controlled and manipulated in all the three dimensions. Here we report our observations on rotation of red blood cells (RBCs) in a linearly polarized optical trap. Red blood cells deform and become twisted in hypertonic phosphate buffer saline and when trapped, experience an unbalanced radiation pressure force. The torque generated from the unbalanced force causes the trapped RBC to rotate. Addition of Ca^{++} ions in the solution, keeping the osmolarity same, makes the cell membranes stiffer and the cells deform less. Thus the speed of rotation of the red blood cells can be controlled, as less deformation and in turn less asymmetry in shape produces less torque under the radiation pressure resulting in slower rotation at the same laser power.

  13. Micro-rheology on (polymer-grafted) colloids using optical tweezers.

    PubMed

    Gutsche, C; Elmahdy, M M; Kegler, K; Semenov, I; Stangner, T; Otto, O; Ueberschär, O; Keyser, U F; Krueger, M; Rauscher, M; Weeber, R; Harting, J; Kim, Y W; Lobaskin, V; Netz, R R; Kremer, F

    2011-05-11

    Optical tweezers are experimental tools with extraordinary resolution in positioning (± 1 nm) a micron-sized colloid and in the measurement of forces (± 50 fN) acting on it-without any mechanical contact. This enables one to carry out a multitude of novel experiments in nano- and microfluidics, of which the following will be presented in this review: (i) forces within single pairs of colloids in media of varying concentration and valency of the surrounding ionic solution, (ii) measurements of the electrophoretic mobility of single colloids in different solvents (concentration, valency of the ionic solution and pH), (iii) similar experiments as in (i) with DNA-grafted colloids, (iv) the nonlinear response of single DNA-grafted colloids in shear flow and (v) the drag force on single colloids pulled through a polymer solution. The experiments will be described in detail and their analysis discussed.

  14. Trehalose facilitates DNA melting: a single-molecule optical tweezers study.

    PubMed

    Bezrukavnikov, Sergey; Mashaghi, Alireza; van Wijk, Roeland J; Gu, Chan; Yang, Li Jiang; Gao, Yi Qin; Tans, Sander J

    2014-10-01

    Using optical tweezers, here we show that the overstretching transition force of double-stranded DNA (dsDNA) is lowered significantly by the addition of the disaccharide trehalose as well as certain polyol osmolytes. This effect is found to depend linearly on the logarithm of the trehalose concentration. We propose an entropic driving mechanism for the experimentally observed destabilization of dsDNA that is rooted in the higher affinity of the DNA bases for trehalose than for water, which promotes base exposure and DNA melting. Molecular dynamics simulation reveals the direct interaction of trehalose with nucleobases. Experiments with other osmolytes confirm that the extent of dsDNA destabilization is governed by the ratio between polar and apolar fractions of an osmolyte.

  15. Robert Feulgen Prize Lecture. Laser tweezers and multiphoton microscopes in life sciences.

    PubMed

    König, K

    2000-08-01

    Near infrared (NIR) laser microscopy enables optical micromanipulation, piconewton force determination, and sensitive fluorescence studies by laser tweezers. Otherwise, fluorescence images with high spatial and temporal resolution of living cells and tissues can be obtained via non-resonant fluorophore excitation with multiphoton NIR laser scanning microscopes. Furthermore, NIR femtosecond laser pulses at TW/cm2 intensities can be used to realize non-invasive contact-free surgery of nanometer-sized structures within living cells and tissues. Applications of these novel versatile NIR laser-based tools for the determination of motility forces, coenzyme and chlorophyll imaging, three-dimensional multigene detection, non-invasive optical sectioning of tissues ("optical biopsy"), functional protein imaging, and nanosurgery of chromosomes are described. PMID:11052257

  16. Freely orbiting magnetic tweezers to directly monitor changes in the twist of nucleic acids

    PubMed Central

    Lipfert, Jan; Wiggin, Matthew; Kerssemakers, Jacob W.J.; Pedaci, Francesco; Dekker, Nynke H.

    2011-01-01

    The double-stranded nature of DNA links its replication, transcription and repair to rotational motion and torsional strain. Magnetic tweezers (MT) are a powerful single-molecule technique to apply both forces and torques to individual DNA or RNA molecules. However, conventional MT do not track rotational motion directly and constrain the free rotation of the nucleic acid tether. Here we present freely orbiting MT (FOMT) that allow the measurement of equilibrium fluctuations and changes in the twist of tethered nucleic acid molecules. Using a precisely aligned vertically oriented magnetic field, FOMT enable tracking of the rotation angle from straight forward (x,y)-position tracking and permits the application of calibrated stretching forces, without biasing the tether's free rotation. We utilize FOMT to measure the force-dependent torsional stiffness of DNA from equilibrium rotational fluctuations and to follow the assembly of recombination protein A filaments on DNA. PMID:21863006

  17. Measurement of the microscopic viscosities of microfluids with a dynamic optical tweezers system

    PubMed Central

    Zhang, Yuquan; Wu, Xiaojing; Wang, Yijia; Zhu, Siwei; Gao, Bruce Z; Yuan, X-C

    2016-01-01

    Viscosity coefficients of microfluids—Newtonian and non-Newtonian—were explored through the rotational motion of a particle trapped by optical tweezers in a microflute. Unlike conventional methods based on viscometers, our microfluidic system employs samples of less than 30 µl to complete a measurement. Viscosity coefficients of ethanol and fetal bovine serum, as typical examples of Newtonian and non-Newtonian fluids, were obtained experimentally, and found to be in excellent agreement with theoretical predictions. Additionally, a practical application to a DNA solution with incremental ethidium bromide content was employed and the results are consistent with clinical data, indicating that our system provides a potentially important complementary tool for use in such biological and medical applications. PMID:27087769

  18. Characterization of the mechanical properties of HL-1 cardiomyocytes with high throughput magnetic tweezers

    NASA Astrophysics Data System (ADS)

    Chen, La; Maybeck, Vanessa; Offenhäusser, Andreas; Krause, Hans-Joachim

    2015-08-01

    We characterized the mechanical properties of cardiomyocyte-like HL-1 cells using our recently developed multi-pole magnetic tweezers. With the optimized design, both high force and high throughput are achieved at the same time. Force up to 100 pN can be applied on a 1 μm diameter superparamagnetic bead in a workspace with 60 μm radius, which is encircled symmetrically by 3 sharp magnetic tips. By adjusting the coil currents, both the strength and direction of force can be controlled. The result shows that both viscosity and shear elastic modulus of HL-1 cells exhibit an approximately log-normal distribution. The cells became stiffer as they matured, consistent with a transition from proliferating cells to contractile muscle tissue. Moreover, the mechanical properties of HL-1 cells show high heterogeneity, which agrees well with their physiological structure.

  19. Calibrating oscillation response of a piezo-stage using optical tweezers.

    PubMed

    Zhou, Jin-Hua; Li, Di; Hu, Xin-Yao; Zhong, Min-Cheng; Wang, Zi-Qiang; Gong, Lei; Liu, Wei-Wei; Li, Yin-Mei

    2015-09-21

    In optical tweezers, a piezo-stage (PZT) is widely used to precisely position samples for force clamp, calibrating optical trap and stretching DNA. For a trapped bead in solution, the oscillation response of PZT is vital for all kinds of applications. A coupling ratio, actual amplitude to nominal amplitude, can be calibrated by power spectral density during sinusoidal oscillations. With oscillation frequency increasing, coupling ratio decreases in both x- and y-directions, which is also confirmed by the calibration with light scattering of scanning two aligned beads on slide. Those oscillation responses are related with deformability of chamber and the intrinsic characteristics of PZT. If we take nominal amplitude as actual amplitude for sinusoidal oscillations at 50 Hz, the amplitude is overestimated ~2 times in x-direction and ~3 times in y-direction. That will lead to huge errors for subsequent calibrations.

  20. Evaluating cell matrix mechanics using an integrated nonlinear optical tweezer-confocal imaging system

    NASA Astrophysics Data System (ADS)

    Peng, Berney; Alonzo, Carlo A. C.; Xia, Lawrence; Speroni, Lucia; Georgakoudi, Irene; Soto, Ana M.; Sonnenschein, Carlos; Cronin-Golomb, Mark

    2013-09-01

    Biomechanics plays a central role in breast epithelial morphogenesis. In this study we have used 3D cultures in which normal breast epithelial cells are able to organize into rounded acini and tubular ducts, the main structures found in the breast tissue. We have identified fiber organization as a main determinant of ductal organization. While bulk rheological properties of the matrix seem to play a negligible role in determining the proportion of acini versus ducts, local changes may be pivotal in shape determination. As such, the ability to make microscale rheology measurements coupled with simultaneous optical imaging in 3D cultures can be critical to assess the biomechanical factors underlying epithelial morphogenesis. This paper describes the inclusion of optical tweezers based microrheology in a microscope that had been designed for nonlinear optical imaging of collagen networks in ECM. We propose two microrheology methods and show preliminary results using a gelatin hydrogel and collagen/Matrigel 3D cultures containing mammary gland epithelial cells.

  1. Microfluidic platform combining droplets and magnetic tweezers: application to HER2 expression in cancer diagnosis

    NASA Astrophysics Data System (ADS)

    Ferraro, Davide; Champ, Jérôme; Teste, Bruno; Serra, Marco; Malaquin, Laurent; Viovy, Jean-Louis; de Cremoux, Patricia; Descroix, Stephanie

    2016-05-01

    The development of precision medicine, together with the multiplication of targeted therapies and associated molecular biomarkers, call for major progress in genetic analysis methods, allowing increased multiplexing and the implementation of more complex decision trees, without cost increase or loss of robustness. We present a platform combining droplet microfluidics and magnetic tweezers, performing RNA purification, reverse transcription and amplification in a fully automated and programmable way, in droplets of 250nL directly sampled from a microtiter-plate. This platform decreases sample consumption about 100 fold as compared to current robotized platforms and it reduces human manipulations and contamination risk. The platform’s performance was first evaluated on cell lines, showing robust operation on RNA quantities corresponding to less than one cell, and then clinically validated with a cohort of 21 breast cancer samples, for the determination of their HER2 expression status, in a blind comparison with an established routine clinical analysis.

  2. Tuning the size and configuration of nanocarbon microcapsules: aqueous method using optical tweezers

    NASA Astrophysics Data System (ADS)

    Frusawa, Hiroshi; Matsumoto, Youei

    2014-02-01

    To date, optical manipulation techniques for aqueous dispersions have been developed that deposit and/or transport nanoparticles not only for fundamental studies of colloidal dynamics, but also for either creating photonic devices or allowing accurate control of liquids on micron scales. Here, we report that optical tweezers (OT) system is able to direct three-dimensional assembly of graphene, graphite, and carbon nanotubes (CNT) into microcapsules of hollow spheres. The OT technique facilitates both to visualize the elasticity of a CNT microcapsule and to arrange a triplet of identical graphene microcapsules in aqueous media. Furthermore, the similarity of swelling courses has been found over a range of experimental parameters such as nanocarbon species, the power of the incident light, and the suspension density. Thanks to the universality in evolutions of rescaled capsule size, we can precisely control the size of various nanocarbon microcapsules by adjusting the duration time of laser emission.

  3. Optical tweezers assisted imaging of the Z-ring in Escherichia coli: measuring its radial width

    NASA Astrophysics Data System (ADS)

    Carmon, G.; Kumar, P.; Feingold, M.

    2014-01-01

    Using single-beam, oscillating optical tweezers we can trap and rotate rod-shaped bacterial cells with respect to the optical axis. This technique allows imaging fluorescently labeled three-dimensional sub-cellular structures from different, optimized viewpoints. To illustrate our method we measure D, the radial width of the Z-ring in unconstricted Escherichia coli. We use cells that express FtsZ-GFP and have their cytoplasmic membrane stained with FM4-64. In a vertically oriented cell, both the Z-ring and the cytoplasmic membrane images appear as symmetric circular structures that lend themselves to quantitative analysis. We found that D ≅ 100 nm, much larger than expected.

  4. Identification of volume phase transition of a single microgel particle using optical tweezers

    NASA Astrophysics Data System (ADS)

    Karthickeyan, D.; Gupta, Deepak K.; Tata, B. V. R.

    2016-10-01

    Poly (N-isopropyl acrylamide-co-acrylic acid) (PNIPAM-co-Aac) microgel particles are pH responsive and exhibit volume phase transition (VPT) upon variation of pH. Dynamic light scattering (DLS) is used conventionally to identify VPT and requires a dilute suspension with particle concentration ˜107 particles cm-3 and if particles are polydisperse in nature, DLS data interpretation is relatively difficult. Here we show that optical tweezers allow one to measure the VPT of a single microgel particle by measuring the optical trap stiffness, κ of trapped particle as a function of pH. We report here a sudden change in κ at VPT, which is shown to arise from a sudden decrease in particle diameter with a concomitant increase in the refractive index of the particle at VPT.

  5. Nucleosome assembly depends on the torsion in the DNA molecule: a magnetic tweezers study.

    PubMed

    Gupta, Pooja; Zlatanova, Jordanka; Tomschik, Miroslav

    2009-12-16

    We have used magnetic tweezers to study nucleosome assembly on topologically constrained DNA molecules. Assembly was achieved using chicken erythrocyte core histones and histone chaperone protein Nap1 under constant low force. We have observed only partial assembly when the DNA was topologically constrained and much more complete assembly on unconstrained (nicked) DNA tethers. To verify our hypothesis that the lack of full nucleosome assembly on topologically constrained tethers was due to compensatory accumulation of positive supercoiling in the rest of the template, we carried out experiments in which we mechanically relieved the positive supercoiling by rotating the external magnetic field at certain time points of the assembly process. Indeed, such rotation did lead to the same nucleosome saturation level as in the case of nicked tethers. We conclude that levels of positive supercoiling in the range of 0.025-0.051 (most probably in the form of twist) stall the nucleosome assembly process.

  6. Micro-particle manipulation by single beam acoustic tweezers based on hydrothermal PZT thick film

    NASA Astrophysics Data System (ADS)

    Zhu, Benpeng; Xu, Jiong; Li, Ying; Wang, Tian; Xiong, Ke; Lee, Changyang; Yang, Xiaofei; Shiiba, Michihisa; Takeuchi, Shinichi; Zhou, Qifa; Shung, K. Kirk

    2016-03-01

    Single-beam acoustic tweezers (SBAT), used in laboratory-on-a-chip (LOC) device has promising implications for an individual micro-particle contactless manipulation. In this study, a freestanding hydrothermal PZT thick film with excellent piezoelectric property (d33 = 270pC/N and kt = 0.51) was employed for SBAT applications and a press-focusing technology was introduced. The obtained SBAT, acting at an operational frequency of 50MHz, a low f-number (˜0.9), demonstrated the capability to trap and manipulate a micro-particle sized 10μm in the distilled water. These results suggest that such a device has great potential as a manipulator for a wide range of biomedical and chemical science applications.

  7. Protection of primary neurons and mouse brain from Alzheimer’s pathology by molecular tweezers

    PubMed Central

    Attar, Aida; Ripoli, Cristian; Riccardi, Elisa; Maiti, Panchanan; Li Puma, Domenica D.; Liu, Tingyu; Hayes, Jane; Jones, Mychica R.; Lichti-Kaiser, Kristin; Yang, Fusheng; Gale, Greg D.; Tseng, Chi-hong; Tan, Miao; Xie, Cui-Wei; Straudinger, Jeffrey L.; Klärner, Frank-Gerrit; Schrader, Thomas; Frautschy, Sally A.; Grassi, Claudio

    2012-01-01

    Alzheimer’s disease is a devastating cureless neurodegenerative disorder affecting >35 million people worldwide. The disease is caused by toxic oligomers and aggregates of amyloid β protein and the microtubule-associated protein tau. Recently, the Lys-specific molecular tweezer CLR01 has been shown to inhibit aggregation and toxicity of multiple amyloidogenic proteins, including amyloid β protein and tau, by disrupting key interactions involved in the assembly process. Following up on these encouraging findings, here, we asked whether CLR01 could protect primary neurons from Alzheimer’s disease-associated synaptotoxicity and reduce Alzheimer’s disease–like pathology in vivo. Using cell culture and brain slices, we found that CLR01 effectively inhibited synaptotoxicity induced by the 42-residue isoform of amyloid β protein, including ∼80% inhibition of changes in dendritic spines density and long-term potentiation and complete inhibition of changes in basal synaptic activity. Using a radiolabelled version of the compound, we found that CLR01 crossed the mouse blood–brain barrier at ∼2% of blood levels. Treatment of 15-month-old triple-transgenic mice for 1 month with CLR01 resulted in a decrease in brain amyloid β protein aggregates, hyperphosphorylated tau and microglia load as observed by immunohistochemistry. Importantly, no signs of toxicity were observed in the treated mice, and CLR01 treatment did not affect the amyloidogenic processing of amyloid β protein precursor. Examining induction or inhibition of the cytochrome P450 metabolism system by CLR01 revealed minimal interaction. Together, these data suggest that CLR01 is safe for use at concentrations well above those showing efficacy in mice. The efficacy and toxicity results support a process-specific mechanism of action of molecular tweezers and suggest that these are promising compounds for developing disease-modifying therapy for Alzheimer’s disease and related disorders. PMID

  8. Optoelectronic tweezers for the measurement of the relative stiffness of erythrocytes

    NASA Astrophysics Data System (ADS)

    Neale, Steven L.; Mody, Nimesh; Selman, Colin; Cooper, Jonathan M.

    2012-10-01

    In this paper we describe the first use of Optoelectronic Tweezers (OET), an optically controlled micromanipulation method, to measure the relative stiffness of erythrocytes in mice. Cell stiffness is an important measure of cell health and in the case of erythrocytes, the most elastic cells in the body, an increase in cell stiffness can indicate pathologies such as type II diabetes mellitus or hypertension (high blood pressure). OET uses a photoconductive device to convert an optical pattern into and electrical pattern. The electrical fields will create a dipole within any polarisable particles in the device, such as cells, and non-uniformities of the field can be used to place unequal forces onto each side of the dipole thus moving the particle. In areas of the device where there are no field gradients, areas of constant illumination, the force on each side of the dipole will be equal, keeping the cell stationary, but as there are opposing forces on each side of the cell it will be stretched. The force each cell will experience will differ slightly so the stretching will depend on the cells polarisability as well as its stiffness. Because of this a relative stiffness rather than absolute stiffness is measured. We show that with standard conditions (20Vpp, 1.5MHz, 10mSm-1 medium conductivity) the cell's diameter changes by around 10% for healthy mouse erythrocytes and we show that due to the low light intensities required for OET, relative to conventional optical tweezers, multiple cells can be measured simultaneously.

  9. In Vivo Quantification of Peroxisome Tethering to Chloroplasts in Tobacco Epidermal Cells Using Optical Tweezers1[OPEN

    PubMed Central

    Gao, Hongbo; Teanby, Nick A.; Ward, Andy D.; Coles, Benjamin; Pollard, Mark R.; Sparkes, Imogen

    2016-01-01

    Peroxisomes are highly motile organelles that display a range of motions within a short time frame. In static snapshots, they can be juxtaposed to chloroplasts, which has led to the hypothesis that they are physically interacting. Here, using optical tweezers, we tested the dynamic physical interaction in vivo. Using near-infrared optical tweezers combined with TIRF microscopy, we were able to trap peroxisomes and approximate the forces involved in chloroplast association in vivo in tobacco (Nicotiana tabacum) and observed weaker tethering to additional unknown structures within the cell. We show that chloroplasts and peroxisomes are physically tethered through peroxules, a poorly described structure in plant cells. We suggest that peroxules have a novel role in maintaining peroxisome-organelle interactions in the dynamic environment. This could be important for fatty acid mobilization and photorespiration through the interaction with oil bodies and chloroplasts, highlighting a fundamentally important role for organelle interactions for essential biochemistry and physiological processes. PMID:26518344

  10. Monitoring of spectroscopic changes of a single trapped fission yeast cell by using a Raman tweezers set-up

    NASA Astrophysics Data System (ADS)

    Başar, G.; Kın, S.

    2008-10-01

    We demonstrate an improvement of the sensitivity of a Raman tweezers set-up, which combines optical tweezers with Raman spectroscopy. The system was tested by taking the Raman spectrum of a 4.6 μm diameter polystyrene sphere trapped in an aqueous solution. The improvement of sensitivity of the set-up was achieved by adjusting the trap depth for maximum signal to noise ratio (SNR). The maximum SNR was obtained by investigating the Raman peak of a trapped polystyrene sphere at 1001 cm -1 according to trap depth. With this system, a single trapped living Schizosaccharomyces Pombe yeast cell was sensitively monitored by taking the kinetic Raman spectra for more than 2 h. The relative intensity decrease in amide I and amide III bands, frequency increase in amide I band together with alterations in tyrosine marker band around 850 cm -1 was observed, which indicates alterations in the hydration state of protein by time progressing.

  11. Tethered anthracene pair as molecular tweezers for post-production separation of single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Anderson, Ankoma; Yang, Fengchun; Cao, Li; Li, Huaping; Meziani, Mohammed J.; Sun, Ya-Ping

    2016-07-01

    As-produced single-walled carbon nanotubes (SWNTs) are metallic and semiconducting mixtures. An anthracene mono-derivative with a long alkyl tail and a molecule with a tethered pair of anthracene species (bis-anthracene) in a "molecular tweezers"-like configuration were synthesized and evaluated for the separation of SWNTs. While the mono-derivative was incapable of the noncovalent functionalization-solubilization, the bis-anthracene was found to be very effective. The results suggest that molecular tweezers of a tethered pair of planar aromatic species can be coupled with the selection of a suitable solvent or solvent mixture for effective and efficient post-production separation of metallic and semiconducting SWNTs.

  12. Portable magnetic tweezers device enables visualization of the three-dimensional microscale deformation of soft biological materials.

    PubMed

    Yang, Yali; Lin, Jun; Meschewski, Ryan; Watson, Erin; Valentine, Megan T

    2011-07-01

    We have designed and built a magnetic tweezers device that enables the application of calibrated stresses to soft materials while simultaneously measuring their microscale deformation using confocal microscopy. Unlike previous magnetic tweezers designs, our device is entirely portable, allowing easy use on microscopes in core imaging facilities or in collaborators' laboratories. The imaging capabilities of the microscope are unimpaired, enabling the 3-D structures of fluorescently labeled materials to be precisely determined under applied load. With this device, we can apply a large range of forces (~1-1200 pN) over micron-scale contact areas to beads that are either embedded within 3-D matrices or attached to the surface of thin slab gels. To demonstrate the usefulness of this instrument, we have studied two important and biologically relevant materials: polyacrylamide-based hydrogel films typical of those used in cell traction force microscopy, and reconstituted networks of microtubules, essential cytoskeletal filaments.

  13. Portable magnetic tweezers device enables visualization of the three-dimensional microscale deformation of soft biological materials.

    PubMed

    Yang, Yali; Lin, Jun; Meschewski, Ryan; Watson, Erin; Valentine, Megan T

    2011-07-01

    We have designed and built a magnetic tweezers device that enables the application of calibrated stresses to soft materials while simultaneously measuring their microscale deformation using confocal microscopy. Unlike previous magnetic tweezers designs, our device is entirely portable, allowing easy use on microscopes in core imaging facilities or in collaborators' laboratories. The imaging capabilities of the microscope are unimpaired, enabling the 3-D structures of fluorescently labeled materials to be precisely determined under applied load. With this device, we can apply a large range of forces (~1-1200 pN) over micron-scale contact areas to beads that are either embedded within 3-D matrices or attached to the surface of thin slab gels. To demonstrate the usefulness of this instrument, we have studied two important and biologically relevant materials: polyacrylamide-based hydrogel films typical of those used in cell traction force microscopy, and reconstituted networks of microtubules, essential cytoskeletal filaments. PMID:21781050

  14. Assessment of red blood cell deformability in type 2 diabetes mellitus and diabetic retinopathy by dual optical tweezers stretching technique

    PubMed Central

    Agrawal, Rupesh; Smart, Thomas; Nobre-Cardoso, João; Richards, Christopher; Bhatnagar, Rhythm; Tufail, Adnan; Shima, David; H. Jones, Phil; Pavesio, Carlos

    2016-01-01

    A pilot cross sectional study was conducted to investigate the role of red blood cells (RBC) deformability in type 2 diabetes mellitus (T2DM) without and with diabetic retinopathy (DR) using a dual optical tweezers stretching technique. A dual optical tweezers was made by splitting and recombining a single Nd:YAG laser beam. RBCs were trapped directly (i.e., without microbead handles) in the dual optical tweezers where they were observed to adopt a “side-on” orientation. RBC initial and final lengths after stretching were measured by digital video microscopy, and a Deformability index (DI) calculated. Blood from 8 healthy controls, 5 T2DM and 7 DR patients with respective mean age of 52.4yrs, 51.6 yrs and 52 yrs was analysed. Initial average length of RBCs for control group was 8.45 ± 0.25 μm, 8.68 ± 0.49 μm for DM RBCs and 8.82 ± 0.32 μm for DR RBCs (p < 0.001). The DI for control group was 0.0698 ± 0.0224, and that for DM RBCs was 0.0645 ± 0.03 and 0.0635 ± 0.028 (p < 0.001) for DR group. DI was inversely related to basal length of RBCs (p = 0.02). DI of RBC from DM and DR patients was significantly lower in comparison with normal healthy controls. A dual optical tweezers method can hence be reliably used to assess RBC deformability. PMID:26976672

  15. Linear Supramolecular Polymers via Connecting Telechelic Polycaprolactone through Alkynylplatinum(II) Terpyridine Molecular Tweezer/Pyrene Recognition Motif.

    PubMed

    Liu, Huaqing; Han, Xiaohang; Gao, Zongchun; Gao, Zhao; Wang, Feng

    2016-04-01

    By anchoring alkynylplatinum(II) terpyridine molecular tweezer/pyrene recognition motif on the chain-ends of telechelic polycaprolactone, high-molecular-weight supramolecular polymers have been successfully constructed via noncovalent chain extension, which demonstrate fascinating rheological and thermal properties. Moreover, the resulting assemblies exhibit interesting temperature- and solvent-responsive behaviors, which are promising for the development of adaptive functional materials. PMID:26924177

  16. Normal and system lupus erythematosus red blood cell interactions studied by double trap optical tweezers: direct measurements of aggregation forces

    NASA Astrophysics Data System (ADS)

    Khokhlova, Maria D.; Lyubin, Eugeny V.; Zhdanov, Alexander G.; Rykova, Sophia Yu.; Sokolova, Irina A.; Fedyanin, Andrey A.

    2012-02-01

    Direct measurements of aggregation forces in piconewton range between two red blood cells in pair rouleau are performed under physiological conditions using double trap optical tweezers. Aggregation and disaggregation properties of healthy and pathologic (system lupus erythematosis) blood samples are analyzed. Strong difference in aggregation speed and behavior is revealed using the offered method which is proposed to be a promising tool for SLE monitoring at single cell level.

  17. Blind Predictions of DNA and RNA Tweezers Experiments with Force and Torque

    PubMed Central

    Chou, Fang-Chieh; Lipfert, Jan; Das, Rhiju

    2014-01-01

    Single-molecule tweezers measurements of double-stranded nucleic acids (dsDNA and dsRNA) provide unprecedented opportunities to dissect how these fundamental molecules respond to forces and torques analogous to those applied by topoisomerases, viral capsids, and other biological partners. However, tweezers data are still most commonly interpreted post facto in the framework of simple analytical models. Testing falsifiable predictions of state-of-the-art nucleic acid models would be more illuminating but has not been performed. Here we describe a blind challenge in which numerical predictions of nucleic acid mechanical properties were compared to experimental data obtained recently for dsRNA under applied force and torque. The predictions were enabled by the HelixMC package, first presented in this paper. HelixMC advances crystallography-derived base-pair level models (BPLMs) to simulate kilobase-length dsDNAs and dsRNAs under external forces and torques, including their global linking numbers. These calculations recovered the experimental bending persistence length of dsRNA within the error of the simulations and accurately predicted that dsRNA's “spring-like” conformation would give a two-fold decrease of stretch modulus relative to dsDNA. Further blind predictions of helix torsional properties, however, exposed inaccuracies in current BPLM theory, including three-fold discrepancies in torsional persistence length at the high force limit and the incorrect sign of dsRNA link-extension (twist-stretch) coupling. Beyond these experiments, HelixMC predicted that ‘nucleosome-excluding’ poly(A)/poly(T) is at least two-fold stiffer than random-sequence dsDNA in bending, stretching, and torsional behaviors; Z-DNA to be at least three-fold stiffer than random-sequence dsDNA, with a near-zero link-extension coupling; and non-negligible effects from base pair step correlations. We propose that experimentally testing these predictions should be powerful next steps for

  18. Micromanipulation by laser microbeam and optical tweezers: from plant cells to single molecules.

    PubMed

    Greulich, K O; Pilarczyk, G; Hoffmann, A; Meyer Zu Hörste, G; Schäfer, B; Uhl, V; Monajembashi, S

    2000-06-01

    Complete manipulation by laser light allows precise and gentle treatment of plant cells, subcellular structures, and even individual DNA molecules. Recently, affordable lasers have become available for the construction of microbeams as well as for optical tweezers. This may generate new interest in these tools for plant biologists. Early experiments, reviewed in this journal, showed that laser supported microinjection of material into plant cells or tissues circumvents mechanical problems encountered in microinjection by fragile glass capillaries. Plant protoplasts could be fused with each other when under microscopical observation, and it was no major problem to generate a triple or quadruple fusion product. In the present paper we review experiments where membrane material was prepared from root hair tips and microgravity was simulated in algae. As many plant cells are transparent, it is possible to work inside living, intact cells. New experiments show that it is possible to release by optical micromanipulation, with high spatial resolutions, intracellular calcium from caged compounds and to study calcium oscillations. An example for avian cardiac tissue is given, but the technique is also suitable for plant cell research. As a more technical tool, optical tweezers can be used to spatially fix subcellular structures otherwise moving inside a cell and thus make them available for investigation with a confocal microscope even when the time for image formation is extended (for example at low fluorescence emission). A molecular biological example is the handling of chromosomes and isolated individual DNA molecules by laser microtools. For example, chromosomes can be cut along complex trajectories, not only perpendicular to their long axis. Single DNA molecules are cut by the laser microbeam and, after coupling such a molecule to a polystrene microbead, are handled in complex geometries. Here, the individual DNA molecules are made visible with a conventional

  19. Drug-DNA interactions at single molecule level: A view with optical tweezers

    NASA Astrophysics Data System (ADS)

    Paramanathan, Thayaparan

    Studies of small molecule--DNA interactions are essential for developing new drugs for challenging diseases like cancer and HIV. The main idea behind developing these molecules is to target and inhibit the reproduction of the tumor cells and infected cells. We mechanically manipulate single DNA molecule using optical tweezers to investigate two molecules that have complex and multiple binding modes. Mononuclear ruthenium complexes have been extensively studied as a test for rational drug design. Potential drug candidates should have high affinity to DNA and slow dissociation kinetics. To achieve this, motifs of the ruthenium complexes are altered. Our collaborators designed a dumb-bell shaped binuclear ruthenium complex that can only intercalate DNA by threading through its bases. Studying the binding properties of this complex in bulk studies took hours. By mechanically manipulating a single DNA molecule held with optical tweezers, we lower the barrier to thread and make it fast compared to the bulk experiments. Stretching single DNA molecules with different concentration of drug molecules and holding it at a constant force allows the binding to reach equilibrium. By this we can obtain the equilibrium fractional ligand binding and length of DNA at saturated binding. Fitting these results yields quantitative measurements of the binding thermodynamics and kinetics of this complex process. The second complex discussed in this study is Actinomycin D (ActD), a well studied anti-cancer agent that is used as a prototype for developing new generations of drugs. However, the biophysical basis of its activity is still unclear. Because ActD is known to intercalate double stranded DNA (dsDNA), it was assumed to block replication by stabilizing dsDNA in front of the replication fork. However, recent studies have shown that ActD binds with even higher affinity to imperfect duplexes and some sequences of single stranded DNA (ssDNA). We directly measure the on and off rates by

  20. Spectrin-Level Modeling of the Cytoskeleton and Optical Tweezers Stretching of the Erythrocyte

    PubMed Central

    Li, J.; Dao, M.; Lim, C. T.; Suresh, S.

    2005-01-01

    We present a three-dimensional computational study of whole-cell equilibrium shape and deformation of human red blood cell (RBC) using spectrin-level energetics. Random network models consisting of degree-2, 3, …, 9 junction complexes and spectrin links are used to populate spherical and biconcave surfaces and intermediate shapes, and coarse-grained molecular dynamics simulations are then performed with spectrin connectivities fixed. A sphere is first filled with cytosol and gradually deflated while preserving its total surface area, until cytosol volume consistent with the real RBC is reached. The equilibrium shape is determined through energy minimization by assuming that the spectrin tetramer links satisfy the worm-like chain free-energy model. Subsequently, direct stretching by optical tweezers of the initial equilibrium shape is simulated to extract the variation of axial and transverse diameters with the stretch force. At persistence length p = 7.5 nm for the spectrin tetramer molecule and corresponding in-plane shear modulus μ0 ≈ 8.3 μN/m, our models show reasonable agreement with recent experimental measurements on the large deformation of RBC with optical tweezers. We find that the choice of the reference state used for the in-plane elastic energy is critical for determining the equilibrium shape. If a position-independent material reference state such as a full sphere is used in defining the in-plane energy, then the bending modulus κ needs to be at least a decade larger than the widely accepted value of 2 × 10−19 J to stabilize the biconcave shape against the cup shape. We demonstrate through detailed computations that this paradox can be avoided by invoking the physical hypothesis that the spectrin network undergoes constant remodeling to always relax the in-plane shear elastic energy to zero at any macroscopic shape, at some slow characteristic timescale. We have devised and implemented a liquefied network structure evolution algorithm that

  1. Optical tweezers based measurement of PLGA-NP interaction with prostate cancer cells

    NASA Astrophysics Data System (ADS)

    Blesener, Thea; Mondal, Argha; Menon, Jyothi U.; Nguyen, Kytai T.; Mohanty, Samarendra

    2013-02-01

    In order to quantify the binding capacities of polymeric, biodegradable and biocompatible poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs), conjugated with either R11 peptides or Folic Acid, the strength by detach from prostate cancer cells (PCCs) was measured via optical tweezers based measurements. Specific nanoparticle drug delivery eliminates the previously used diffuse, full-body application of potent cancer drugs by localizing drug delivery to malignant cells. Precise monitoring of NP position in the trap near the PCC membrane using a fluorescence imaging based method enabled calibration of the trap stiffness and subsequent force measurements. By defining the force with which the many diverse conjugates and coatings of different types of NPs bind the vast array of cancer cell types, chemotherapeutic drugs can be delivered in a specific manner with the optimal particle and corresponding conjugates. Further, and most significantly, the rupture force measurements will reveal whether or not targeted nanoparticles can overcome the force of blood attempting to pull the particle from designated cells. Our preliminary study revealed that the binding between PLGA-NPs and prostate cancer cells is enhanced by coating with folic acid or R11 peptides. These conjugates increase the force required to detach the particle thus allowing particles to overcome drag force of the blood in prostate capillary systems.

  2. Ion-selective electrodes based on molecular tweezer-type neutral carriers.

    PubMed

    Shim, Jun Ho; Jeong, In Seok; Lee, Min Hyung; Hong, Hun Pyo; On, Jeung Hoon; Kim, Ki Soo; Kim, Hong-Seok; Kim, Byeong Hyo; Cha, Geun Sig; Nam, Hakhyun

    2004-05-10

    Potentiometric properties of cholic and deoxycholic acid derivatives substituted with various ion-recognizing moieties, such as dithiocarbamate, bipyridyl, glycolic and malonic diamides, urea and thiourea, and trifluoroacetophenons (TFAP), have been studied using solvent polymeric membranes. The dithiocarbamate and bipyridyl group containing ionophores exhibit high silver ion selectivity. The cholic acid derivatized with glycolic diamides exhibited high calcium selectivity, but its complex formulation constant was 10(5) times smaller than that of ETH 1001. The reduced calcium binding ability of the glycolic diamide-substituted ionophore was advantageous for eliminating anionic interference. The bi- or tripodal malonic diamide-substituted ionophores exhibited substantially increased magnesium selectivity. Anion-selective ionophores have been designed by substituting urea and thiourea group containing chains to the hydroxyl linkers of chenodeoxycholic acid frames; their selectivity closely followed the sequence of Hoffmeister series, except the unusually large response of the thiourea-substituted ionophore to sulfate. The most successful examples of cholic or deoxycholic acid frame-based ionophores are those functionalized with two carbonate-selective TFAP groups: bipodal TFAP groups behaves like a tweezers for the incoming carbonate, and exhibit analytically interference free and quantitative responses to the carbonate in serum and seawater samples. PMID:18969404

  3. Disturbance-free rapid solution exchange for magnetic tweezers single-molecule studies

    PubMed Central

    Le, Shimin; Yao, Mingxi; Chen, Jin; Efremov, Artem K.; Azimi, Sara; Yan, Jie

    2015-01-01

    Single-molecule manipulation technologies have been extensively applied to studies of the structures and interactions of DNA and proteins. An important aspect of such studies is to obtain the dynamics of interactions; however the initial binding is often difficult to obtain due to large mechanical perturbation during solution introduction. Here, we report a simple disturbance-free rapid solution exchange method for magnetic tweezers single-molecule manipulation experiments, which is achieved by tethering the molecules inside microwells (typical dimensions–diameter (D): 40–50 μm, height (H): 100 μm; H:D∼2:1). Our simulations and experiments show that the flow speed can be reduced by several orders of magnitude near the bottom of the microwells from that in the flow chamber, effectively eliminating the flow disturbance to molecules tethered in the microwells. We demonstrate a wide scope of applications of this method by measuring the force dependent DNA structural transitions in response to solution condition change, and polymerization dynamics of RecA on ssDNA/SSB-coated ssDNA/dsDNA of various tether lengths under constant forces, as well as the dynamics of vinculin binding to α-catenin at a constant force (< 5 pN) applied to the α-catenin protein. PMID:26007651

  4. Dynamic translocation of ligand-complexed DNA through solid-state nanopores with optical tweezers

    NASA Astrophysics Data System (ADS)

    Sischka, Andy; Spiering, Andre; Khaksar, Maryam; Laxa, Miriam; König, Janine; Dietz, Karl-Josef; Anselmetti, Dario

    2010-11-01

    We investigated the threading and controlled translocation of individual lambda-DNA (λ-DNA) molecules through solid-state nanopores with piconewton force sensitivity, millisecond time resolution and picoampere ionic current sensitivity with a set-up combining quantitative 3D optical tweezers (OT) with electrophysiology. With our virtually interference-free OT set-up the binding of RecA and single peroxiredoxin protein molecules to λ-DNA was quantitatively investigated during dynamic translocation experiments where effective forces and respective ionic currents of the threaded DNA molecule through the nanopore were measured during inward and outward sliding. Membrane voltage-dependent experiments of reversible single protein/DNA translocation scans yield hysteresis-free, asymmetric single-molecule fingerprints in the measured force and conductance signals that can be attributed to the interplay of optical trap and electrostatic nanopore potentials. These experiments allow an exact localization of the bound protein along the DNA strand and open fascinating applications for label-free detection of DNA-binding ligands, where structural and positional binding phenomena can be investigated at a single-molecule level.

  5. The history and evolution of surgical instruments. VII. Spring forceps (tweezers), hooks and simple retractors.

    PubMed Central

    Kirkup, J.

    1996-01-01

    Instruments manufactured by bending a basic metal strip or rod, either about its middle to create spring forceps (tweezers), or towards one extremity to create hooks and retractors are related structures. Spring forceps depend on tension mediated at the bend (hoop) or fixed end which is transmitted as dynamic 'spring' to the jaws, whereas the bend of hooks and retractors remains fixed and static. If such instruments refine the digital postures of pinch, pincer and retraction during surgery, they have not supplanted these manual actions entirely. After a brief historical introduction, the structure, modifications, functions and controls of spring forceps are analysed. Importantly, this instrument enjoys both right and left-handed functions, some of which are ancient, some transient as haemostats and needle-holders, and some, including left-handed dissection, surprisingly recent. Hooks are sharp or blunt and, among other functions, pre-date the left-handed spring forceps for dissection; in general hooks function as retractors. Hand-held retractors are enlarged blunt hooks, the wide retracting contact surface reducing trauma to wound margins and viscera. The physical effort of employing these retractors deep in body cavities is abated by applying them autostatically around a square or circular frame. Images Figure 1 PMID:8943642

  6. Guest encapsulation and coronene-C60 exchange in supramolecular zinc porphyrin tweezers, grids and prisms.

    PubMed

    Samanta, Soumen K; Schmittel, Michael

    2013-05-21

    Using a variant of the HETPHEN concept, heteroleptic 2D and 3D metallosupramolecular structures, such as tweezer T, grid G and tetragonal prism P, were fabricated quantitatively and characterised by (1)H NMR, (13)C NMR, (1)H-(1)H COSY, DOSY as well as ESI-MS. All structures encapsulate C60, with P showing the highest binding affinity (Kassoc = 3.3 × 10(6) M(-1)). The association constant increases along the series T < G < P, most likely due to the enhanced structural rigidity and better coplanarity of the two zinc porphyrin units. In contrast to T and G, the tetragonal prism P shows notable encapsulation of coronene (Kassoc = 1.1 × 10(4) M(-1)). In T and G, on the other hand, complexation of coronene is kinetically inhibited by the bulky mesityl rings at the porphyrin periphery. As illustrated in the facile displacement of coronene by C60 in coronene@P to furnish C60@P, P behaves as a flexible and guest-adaptive host.

  7. Holographic Raman tweezers controlled by multi-modal natural user interface

    NASA Astrophysics Data System (ADS)

    Tomori, Zoltán; Keša, Peter; Nikorovič, Matej; Kaňka, Jan; Jákl, Petr; Šerý, Mojmír; Bernatová, Silvie; Valušová, Eva; Antalík, Marián; Zemánek, Pavel

    2016-01-01

    Holographic optical tweezers provide a contactless way to trap and manipulate several microobjects independently in space using focused laser beams. Although the methods of fast and efficient generation of optical traps are well developed, their user friendly control still lags behind. Even though several attempts have appeared recently to exploit touch tablets, 2D cameras, or Kinect game consoles, they have not yet reached the level of natural human interface. Here we demonstrate a multi-modal ‘natural user interface’ approach that combines finger and gaze tracking with gesture and speech recognition. This allows us to select objects with an operator’s gaze and voice, to trap the objects and control their positions via tracking of finger movement in space and to run semi-automatic procedures such as acquisition of Raman spectra from preselected objects. This approach takes advantage of the power of human processing of images together with smooth control of human fingertips and downscales these skills to control remotely the motion of microobjects at microscale in a natural way for the human operator.

  8. Initiation of bacteriophage Φ29 DNA packaging studied by optical tweezers manipulation of single DNA molecules

    NASA Astrophysics Data System (ADS)

    Rickgauer, John Peter; Fuller, Derek N.; Hu, Bo; Grimes, Shelley; Jardine, Paul J.; Anderson, Dwight L.; Smith, Douglas E.

    2006-08-01

    A key step in the life cycle of many viruses, including bacteriophages, adenoviruses, and herpesviruses, is the packaging of replicated viral genomes into pre-assembled proheads by the action of ATP-dependent portal motor complexes. Here we present a method that allows the initiation of packaging by single complexes to be studied using optical tweezers. A procedure is developed for assembling phage Φ29 prohead-motor complexes, which are demonstrated to bind and begin translocation of a target DNA molecule within only a few seconds. We show that the Φ29 DNA terminal protein (gene product 3), which functions to prime DNA replication, also has a dramatic effect on packaging. The DNA tether length measured immediately after binding varied from ~30-100% of the full length, yet shortened monotonically, indicating that packaging does not strictly begin at the terminal end of the DNA. Removal of the terminal protein eliminated this variability, causing packaging to initiate at or very near the end of the DNA. These findings, taken together with electron microscopy data, suggest that rather than simply threading into the portal, the motor captures and dynamically tensions a DNA loop, and that the function of the terminal protein is to load DNA segments on both sides of the loop junction onto separate DNA translocating units.

  9. STED nanoscopy combined with optical tweezers reveals protein dynamics on densely covered DNA (presentation video)

    NASA Astrophysics Data System (ADS)

    Heller, Iddo; Sitters, Gerrit; Broekmans, Onno D.; Farge, Géraldine; Menges, Carolin; Wende, Wolfgang; Hell, Stefan W.; Peterman, Erwin J.; Wuite, Gijs J.

    2014-09-01

    Dense coverage of DNA by proteins is a ubiquitous feature of cellular processes such as DNA organization, replication and repair. We present a single-molecule approach capable of visualizing individual DNA-binding proteins on densely covered DNA and in the presence of high protein concentrations. Our approach combines optical tweezers with multicolor confocal and stimulated emission depletion (STED) fluorescence microscopy. Proteins on DNA are visualized at a resolution of 50 nm, a sixfold resolution improvement over that of confocal microscopy. High temporal resolution (<50 ms) is ensured by fast one-dimensional beam scanning. Individual trajectories of proteins translocating on DNA can thus be distinguished and tracked with high precision. We demonstrate our multimodal approach by visualizing the assembly of dense nucleoprotein filaments with unprecedented spatial resolution in real time. Experimental access to the force-dependent kinetics and motility of DNA-associating proteins at biologically relevant protein densities is essential for linking idealized in vitro experiments with the in vivo situation.

  10. Single-molecule kinetics under force: probing protein folding and enzymatic activity with optical tweezers

    NASA Astrophysics Data System (ADS)

    Wong, Wesley

    2010-03-01

    Weak non-covalent bonds between and within single molecules govern many aspects of biological structure and function (e.g. DNA base-paring, receptor-ligand binding, protein folding, etc.) In living systems, these interactions are often subject to mechanical forces, which can greatly alter their kinetics and activity. My group develops and applies novel single-molecule manipulation techniques to explore and quantify these force-dependent kinetics. Using optical tweezers, we have quantified the force-dependent unfolding and refolding kinetics of different proteins, including the cytoskeletal protein spectrin in collaboration with E. Evans's group [1], and the A2 domain of the von Willebrand factor blood clotting protein in collaboration with T. Springer's group [2]. Furthermore, we have studied the kinetics of the ADAMTS13 enzyme acting on a single A2 domain, and have shown that physiolgical forces in the circulation can act as a cofactor for enzymatic cleavage, regulating hemostatic activity [2]. References: 1. E. Evans, K. Halvorsen, K. Kinoshita, and W.P. Wong, Handbook of Single Molecule Biophysics, P. Hinterdorfer, ed., Springer (2009). 2. X. Zhang, K. Halvorsen, C.-Z. Zhang, W.P. Wong, and T.A. Springer, Science 324 (5932), 1330-1334 (2009).

  11. Cell manipulation tool with combined microwell array and optical tweezers for cell isolation and deposition

    NASA Astrophysics Data System (ADS)

    Wang, Xiaolin; Gou, Xue; Chen, Shuxun; Yan, Xiao; Sun, Dong

    2013-07-01

    Isolation from rare cells and deposition of sorted cells with high accuracy for further study are critical to a wide range of biomedical applications. In the current paper, we report an automated cell manipulation tool with combined optical tweezers and a uniquely designed microwell array, which functions for recognition, isolation, assembly, transportation and deposition of the interesting cells. The microwell array allows the passive hydrodynamic docking of cells, while offering the opportunity to inspect the interesting cell phenotypes with high spatio-temporal resolution based on the flexible image processing technique. In addition, dynamic and parallel cell manipulation in three dimensions can realize the target cell levitation from microwell and pattern assembly with multiple optical traps. Integrated with the programmed motorized stage, the optically levitated and assembled cells can be transported and deposited to the predefined microenvironment, so the tool can facilitate the integration of other on-chip functionalities for further study without removing these isolated cells from the chip. Experiments on human embryonic stem cells and yeast cells are performed to demonstrate the effectiveness of the proposed cell manipulation tool. Besides the application to cell isolation and deposition, three other biological applications with this tool are also presented.

  12. Acoustical tweezers using single spherically focused piston, X-cut, and Gaussian beams.

    PubMed

    Mitri, Farid G

    2015-10-01

    Partial-wave series expansions (PWSEs) satisfying the Helmholtz equation in spherical coordinates are derived for circular spherically focused piston (i.e., apodized by a uniform velocity amplitude normal to its surface), X-cut (i.e., apodized by a velocity amplitude parallel to the axis of wave propagation), and Gaussian (i.e., apodized by a Gaussian distribution of the velocity amplitude) beams. The Rayleigh-Sommerfeld diffraction integral and the addition theorems for the Legendre and spherical wave functions are used to obtain the PWSEs assuming weakly focused beams (with focusing angle α ⩽ 20°) in the Fresnel-Kirchhoff (parabolic) approximation. In contrast with previous analytical models, the derived expressions allow computing the scattering and acoustic radiation force from a sphere of radius a without restriction to either the Rayleigh (a ≪ λ, where λ is the wavelength of the incident radiation) or the ray acoustics (a ≫λ) regimes. The analytical formulations are valid for wavelengths largely exceeding the radius of the focused acoustic radiator, when the viscosity of the surrounding fluid can be neglected, and when the sphere is translated along the axis of wave propagation. Computational results illustrate the analysis with particular emphasis on the sphere's elastic properties and the axial distance to the center of the concave surface, with close connection of the emergence of negative trapping forces. Potential applications are in single-beam acoustical tweezers, acoustic levitation, and particle manipulation. PMID:26470046

  13. Induction of sustained glycolytic oscillations in single yeast cells using microfluidics and optical tweezers

    NASA Astrophysics Data System (ADS)

    Gustavsson, Anna-Karin; Adiels, Caroline B.; Goksör, Mattias

    2012-10-01

    Yeast glycolytic oscillations have been studied since the 1950s in cell free extracts and in intact cells. Until recently, sustained oscillations have only been observed in intact cells at the population level. The aim of this study was to investigate sustained glycolytic oscillations in single cells. Optical tweezers were used to position yeast cells in arrays with variable cell density in the junction of a microfluidic flow chamber. The microfluidic flow chambers were fabricated using soft lithography and the flow rates in the different inlet channels were individually controlled by syringe pumps. Due to the low Reynolds number, the solutions mixed by diffusion only. The environment in the junction of the chamber could thus be controlled by changing the flow rates in the inlet channels, with a complete change of environment within 2 s. The optimum position of the cell array was determined by simulations, to ensure complete coverage of the intended solution without any concentration gradients over the cell array. Using a DAPI filter set, the NADH auto fluorescence could be monitored in up to 100 cells simultaneously. Sustained oscillations were successfully induced in individual, isolated cells within specific flow rates and concentrations of glucose and cyanide. By changing the flow rates without changing the surrounding solution, it was found that the cell behavior was dependent on the concentration of chemicals in the medium rather than the flow rates in the range tested. Furthermore, by packing cells tightly, cell-to-cell interaction and synchronization could be studied.

  14. Optical tweezers and multiphoton microscopies integrated photonic tool for mechanical and biochemical cell processes studies

    NASA Astrophysics Data System (ADS)

    de Thomaz, A. A.; Faustino, W. M.; Fontes, A.; Fernandes, H. P.; Barjas-Castro, M. d. L.; Metze, K.; Giorgio, S.; Barbosa, L. C.; Cesar, C. L.

    2007-09-01

    The research in biomedical photonics is clearly evolving in the direction of the understanding of biological processes at the cell level. The spatial resolution to accomplish this task practically requires photonics tools. However, an integration of different photonic tools and a multimodal and functional approach will be necessary to access the mechanical and biochemical cell processes. This way we can observe mechanicaly triggered biochemical events or biochemicaly triggered mechanical events, or even observe simultaneously mechanical and biochemical events triggered by other means, e.g. electricaly. One great advantage of the photonic tools is its easiness for integration. Therefore, we developed such integrated tool by incorporating single and double Optical Tweezers with Confocal Single and Multiphoton Microscopies. This system can perform 2-photon excited fluorescence and Second Harmonic Generation microscopies together with optical manipulations. It also can acquire Fluorescence and SHG spectra of specific spots. Force, elasticity and viscosity measurements of stretched membranes can be followed by real time confocal microscopies. Also opticaly trapped living protozoas, such as leishmania amazonensis. Integration with CARS microscopy is under way. We will show several examples of the use of such integrated instrument and its potential to observe mechanical and biochemical processes at cell level.

  15. Calibration of optical tweezers with positional detection in the back focal plane

    SciTech Connect

    Tolic-Noerrelykke, Simon F.; Schaeffer, Erik; Howard, Jonathon; Pavone, Francesco S.; Juelicher, Frank; Flyvbjerg, Henrik

    2006-10-15

    We explain and demonstrate a new method of force and position calibrations for optical tweezers with back-focal-plane photodetection. The method combines power spectral measurements of thermal motion and the response to a sinusoidal motion of a translation stage. It consequently does not use the drag coefficient of the trapped object as an input. Thus, neither the viscosity, nor the size of the trapped object, nor its distance to nearby surfaces needs to be known. The method requires only a low level of instrumentation and can be applied in situ in all spatial dimensions. It is both accurate and precise: true values are returned, with small error bars. We tested this experimentally, near and far from surfaces in the lateral directions. Both position and force calibrations were accurate to within 3%. To calibrate, we moved the sample with a piezoelectric translation stage, but the laser beam could be moved instead, e.g., by acousto-optic deflectors. Near surfaces, this precision requires an improved formula for the hydrodynamical interaction between an infinite plane and a microsphere in nonconstant motion parallel to it. We give such a formula.

  16. Combined optical tweezers and laser dissector for controlled ablation of functional connections in neural networks

    NASA Astrophysics Data System (ADS)

    Difato, Francesco; Dal Maschio, Marco; Marconi, Emanuele; Ronzitti, Giuseppe; Maccione, Alessandro; Fellin, Tommasso; Berdondini, Luca; Chieregatti, Evelina; Benfenati, Fabio; Blau, Axel

    2011-05-01

    Regeneration of functional connectivity within a neural network after different degrees of lesion is of utmost clinical importance. To test pharmacological approaches aimed at recovering from a total or partial damage of neuronal connections within a circuit, it is necessary to develop a precise method for controlled ablation of neuronal processes. We combined a UV laser microdissector to ablate neural processes in vitro at single neuron and neural network level with infrared holographic optical tweezers to carry out force spectroscopy measurements. Simultaneous force spectroscopy, down to the sub-pico-Newton range, was performed during laser dissection to quantify the tension release in a partially ablated neurite. Therefore, we could control and measure the damage inflicted to an individual neuronal process. To characterize the effect of the inflicted injury on network level, changes in activity of neural subpopulations were monitored with subcellular resolution and overall network activity with high temporal resolution by concurrent calcium imaging and microelectrode array recording. Neuronal connections have been sequentially ablated and the correlated changes in network activity traced and mapped. With this unique combination of electrophysiological and optical tools, neural activity can be studied and quantified in response to controlled injury at the subcellular, cellular, and network level.

  17. Simple horizontal magnetic tweezers for micromanipulation of single DNA molecules and DNA–protein complexes

    PubMed Central

    McAndrew, Christopher P.; Tyson, Christopher; Zischkau, Joseph; Mehl, Patrick; Tuma, Pamela L.; Pegg, Ian L.; Sarkar, Abhijit

    2016-01-01

    We report the development of a simple-to-implement magnetic force transducer that can apply a wide range of piconewton (pN) scale forces on single DNA molecules and DNA–protein complexes in the horizontal plane. The resulting low-noise force-extension data enable very high-resolution detection of changes in the DNA tether’s extension: ~0.05 pN in force and <10 nm change in extension. We have also verified that we can manipulate DNA in near equilibrium conditions through the wide range of forces by ramping the force from low to high and back again, and observing minimal hysteresis in the molecule’s force response. Using a calibration technique based on Stokes’ drag law, we have confirmed our force measurements from DNA force-extension experiments obtained using the fluctuation-dissipation theorem applied to transverse fluctuations of the magnetic microsphere. We present data on the force-distance characteristics of a DNA molecule complexed with histones. The results illustrate how the tweezers can be used to study DNA binding proteins at the single molecule level. PMID:26757808

  18. Organic component vapor pressures and hygroscopicities of aqueous aerosol measured by optical tweezers.

    PubMed

    Cai, Chen; Stewart, David J; Reid, Jonathan P; Zhang, Yun-hong; Ohm, Peter; Dutcher, Cari S; Clegg, Simon L

    2015-01-29

    Measurements of the hygroscopic response of aerosol and the particle-to-gas partitioning of semivolatile organic compounds are crucial for providing more accurate descriptions of the compositional and size distributions of atmospheric aerosol. Concurrent measurements of particle size and composition (inferred from refractive index) are reported here using optical tweezers to isolate and probe individual aerosol droplets over extended timeframes. The measurements are shown to allow accurate retrievals of component vapor pressures and hygroscopic response through examining correlated variations in size and composition for binary droplets containing water and a single organic component. Measurements are reported for a homologous series of dicarboxylic acids, maleic acid, citric acid, glycerol, or 1,2,6-hexanetriol. An assessment of the inherent uncertainties in such measurements when measuring only particle size is provided to confirm the value of such a correlational approach. We also show that the method of molar refraction provides an accurate characterization of the compositional dependence of the refractive index of the solutions. In this method, the density of the pure liquid solute is the largest uncertainty and must be either known or inferred from subsaturated measurements with an error of <±2.5% to discriminate between different thermodynamic treatments.

  19. Label-free measurements of membrane tether thickness using optical tweezers combined with SLIM

    NASA Astrophysics Data System (ADS)

    Sarshar, Mohammad; Wong, Winson T.; Anvari, Bahman

    2015-03-01

    Various cellular activities such as motility, division, and endocytosis involve a change in the cell shape. The mechanical interactions between the cell membrane and cytoskeleton play an important role in regulating changes in the cell shape. Tether formation from cell membranes provides a technique to characterize the mechanical properties of cell membranes and membrane-cytoskeleton interactions. Accurate measurement of the nano-scale tether diameter is relevant to quantification of membrane tension, bending modulus, and adhesion energy of the membrane-cytoskeleton structure. We have integrated optical tweezers with quantitative phase imaging, based on spatial light interference microscopy (SLIM), to simultaneously form tethers from HEK-293 cells and measure their diameters. Tether thickness along the illumination axis was measured using the quantitative phase map of the sample, and the refractive index (RI) mismatch between the sample and the surrounding media. The RI of the tethers ranged from 1.354 to 1.368 (cell culture medium RI=1.337). Our SLIM imaging system provided a 38 nm resolution in tether thickness measurements. Tether diameter fluctuations of <100 nm were resolved on tethers that ranged between 600-900 nm in diameter. Our integrated platform also provides the ability to simultaneously manipulate and image cell organelles in a non-contact and marker-free manner at nanometer spatial resolution.

  20. Studying red blood cell agglutination by measuring membrane viscosity with optical tweezers

    NASA Astrophysics Data System (ADS)

    Fernandes, Heloise P.; Fontes, Adriana; de Thomaz, André A.; Barbosa, Luiz C.; Barjas-Castro, Maria L.; Cesar, Carlos L.

    2007-09-01

    The red blood cell (RBC) viscoelastic membrane contains proteins and glycoproteins embedded in a fluid lipid bilayer that are responsible for cell agglutination. Manipulating RBCs rouleaux with a double optical tweezers, we observed that the cells slide easily one over the others but are strongly connected by their edges. An explanation for this behavior could be the fact that when the cells slide one over the others, proteins are dragged through the membrane. It confers to the movement a viscous characteristic that is dependent of the velocity between the RBCs and justifies why is so easy to slide them apart. Therefore, in a first step of this work, by measuring the force as a function of the relative velocity between two cells, we confirmed this assumption and used this viscous characteristic of the RBC rouleaux to determine the apparent membrane viscosity of the cell. As this behavior is related to the proteins interactions, we can use the apparent membrane viscosity to obtain a better understanding about cell agglutination. Methods related to cell agglutination induced by antigen-antibody interactions are the basis of most of tests used in transfusion centers. Then, in a second step of this work, we measured the apparent membrane viscosity using antibodies. We observed that this methodology is sensitive to different kinds of bindings between RBCs. Better comprehension of the forces and bindings between RBCs could improve the sensibility and specificity of the hemagglutination reactions and also guides the development of new potentiator substances.