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Kazuhiko Ishihara - One of the best experts on this subject based on the ideXlab platform.
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preparation of a thick Polymer Brush layer composed of poly 2 methacryloyloxyethyl phosphorylcholine by surface initiated atom transfer radical Polymerization and analysis of protein adsorption resistance
Colloids and Surfaces B: Biointerfaces, 2016Co-Authors: Yuuki Inoue, Yuya Onodera, Kazuhiko IshiharaAbstract:The purpose of this study was to prepare a thick Polymer Brush layer composed of poly(2-methacryloyloxyethyl phosphorylcholine (MPC)) and assess its resistance to protein adsorption from the dissolved state of poly(MPC) chains in an aqueous condition. The thick poly(MPC) Brush layer was prepared through the surface-initiated atom transfer radical Polymerization (SI-ATRP) of MPC with a free initiator from an initiator-immobilized substrate at given [Monomer]/[Free initiator] ratios. The ellipsometric thickness of the poly(MPC) Brush layers could be controlled by the Polymerization degree of the poly(MPC) chains. The thickness of the poly(MPC) Brush layer in an aqueous medium was larger than that in air, and this tendency became clearer when the Polymerization degree of the poly(MPC) increased. The maximum thickness of the poly(MPC) Brush layer in an aqueous medium was around 110 nm. The static air contact angle of the poly(MPC) Brush layer in water indicated a reasonably hydrophilic nature, which was independent of the thickness of the poly(MPC) Brush layer at the surface. This result occurred because the hydrated state of the poly(MPC) chains is not influenced by the environment surrounding them. Finally, as measured with a quartz crystal microbalance, the amount of protein adsorbed from a fetal bovine serum solution (10% in phosphate-buffered saline) on the original substrate was 420 ng/cm(2). However, the poly(MPC) Brush layer reduced this value dramatically to less than 50 ng/cm(2). This effect was independent of the thickness of the poly(MPC) Brush layer for thicknesses between 20 nm and about 110 nm. These results indicated that the surface covered with a poly(MPC) Brush layer is a promising platform to avoid biofouling and could also be applied to analyze the reactions of biological molecules with a high signal/noise ratio.
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molecular interaction forces generated during protein adsorption to well defined Polymer Brush surfaces
Langmuir, 2015Co-Authors: Sho Sakata, Yuuki Inoue, Kazuhiko IshiharaAbstract:The molecular interaction forces generated during the adsorption of proteins to surfaces were examined by the force-versus-distance (f–d) curve measurements of atomic force microscopy using probes modified with appropriate molecules. Various substrates with Polymer Brush layers bearing zwitterionic, cationic, anionic, and hydrophobic groups were systematically prepared by surface-initiated atom transfer radical Polymerization. Surface interaction forces on these substrates were analyzed by the f–d curve measurements using probes with the same Polymer Brush layer as the substrate. Repulsive forces, which decreased depending on the ionic strength, were generated between cationic or anionic polyelectrolyte Brush layers; these were considered to be electrostatic interaction forces. A strong adhesive force was detected between hydrophobic Polymer Brush layers during retraction; this corresponded to the hydrophobic interaction between two hydrophobic Polymer layers. In contrast, no significant interaction force...
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Adhesion force of proteins against hydrophilic Polymer Brush surfaces
Reactive and Functional Polymers, 2011Co-Authors: Yuuki Inoue, Tomoaki Nakanishi, Kazuhiko IshiharaAbstract:Protein adsorption occurs on the surface of biomaterials when they are exposed to physiological environments. The protein adsorption layer induces severe biological responses, including cellular reactions. Protein adsorption layers are formed mainly by two distinct processes: monolayer adsorption of proteins on the surface and a subsequent additional adsorption on the first layer to form a multilayer. Therefore, evaluating the first protein adsorption is important to understand the biological responses on the surface of materials. In this study, we applied the atomic force microscopic (AFM) technique to directly measure the adhesion force of proteins against the surface (i.e., the interaction between proteins and surface). We also prepared hydrophilic Polymer Brush surfaces with well-known high repellency against protein adsorption through surface-initiated atom transfer radical Polymerization. Polymer Brush layers have a well-defined surface structure; therefore, it could be a good model for clarifying the relationship between the surface structure and protein adsorption behavior. The influence of chemical structure of monomer unit and thickness of Polymer Brush layers on the adhesion force of proteins was discussed here, while that of graft density was not discussed. The adhesion force of bovine serum albumin (BSA) immobilized on an AFM cantilever against the thin Polymer Brush surfaces differed from the chemical structures of the monomer unit. The adhesion force of BSA decreased with increasing thickness of the Polymer Brush layer, and there was little difference in the adhesion force of BSA against the thick Polymer Brush surfaces regardless of the chemical structure of the monomer unit. The results demonstrate that the thickness of the Polymer Brush layer would be an important parameter that reduced the interaction between proteins and surfaces compared with the chemical structure of the monomer unit.
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reduction of protein adsorption on well characterized Polymer Brush layers with varying chemical structures
Colloids and Surfaces B: Biointerfaces, 2010Co-Authors: Yuuki Inoue, Kazuhiko IshiharaAbstract:To clarify protein adsorption behavior on Polymer Brush layers, surface characteristics and protein adsorption repellency on Polymer Brush layers should be precisely determined. Here, we clearly delineated the chemical structure of the Polymer Brush layers containing various hydrophilic groups, namely, phosphorylcholine, sulfoxybetaine, carboxybetaine (zwitterionic), and hydroxyl group (nonionic) and examined the effects of the chemical structure on initial protein adsorption behavior. Kinetic analysis performed during surface-initiated atom transfer radical Polymerization revealed that graft Polymerization proceeded in a living manner. The graft density of each type of Polymer chain and its surface coverage were high enough to form dense Polymer Brush structures. The hydroxyl group-bearing Polymer Brush structure exhibited the highest graft density. Among the zwitterionic Polymer Brush structures, the graft density and surface coverage of sulfoxybetaine- and carboxybetaine-bearing Polymer chains were higher than those of the phosphorylcholine-bearing Polymer chains. The amount of protein relative to 100% serum adsorbed on Polymer Brush layers was quantified using quartz crystal microbalance with dissipation (QCM-D). Protein adsorption on all zwitterionic Polymer Brush layers apparently decreased with increasing thickness of the grafted Polymer layers. Protein adsorption was highly suppressed on thick Polymer Brush layers bearing phosphorylcholine or sulfoxybetaine groups. However, the amount of proteins adsorbed on thick Polymer Brush layers bearing hydroxyl groups was 10 times more than that adsorbed on Polymer Brush layers bearing phosphorylcholine groups. Thus, we concluded that the chemical structure of the Polymer Brush layer is a significant factor affecting resistance to protein adsorption even for dense Polymer Brush structures.
Christy F. Landes - One of the best experts on this subject based on the ideXlab platform.
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Single molecule spectroscopy reveals heterogeneous transport mechanisms for molecular ions in a polyelectrolyte Polymer Brush.
The journal of physical chemistry. B, 2009Co-Authors: Carmen Reznik, Rigoberto C. Advincula, Nicel C. Estillore, Christy F. LandesAbstract:Single molecule polarization and fluorescence correlation spectroscopy were used to evaluate heterogeneous transport mechanisms of molecular ions within supported polyelectrolyte Brushes. Modes of diffusive transport include periods of significantly restricted rotational motion, often maintained over tens of milliseconds; periods of fast molecular rotation; and occasional adsorption of fluorescent probe molecules in the Brush. The studies reveal rapid switching between orientational states during each observed mode of motion. Through quantitative analysis of state occupation times, the rate constants for transitions from weakly associated to strongly associated states were extracted. Additionally, the pH dependence of the ion transport rates in the Brush exhibits an abrupt, rather than continuous, trend. These single molecule studies demonstrate the presence of dynamic anisotropic interactions between the charged molecular probe and the Polymer Brush and provide experimental evidence of stimuli responsive...
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Single ion diffusive transport within a Poly(styrene sulfonate) Polymer Brush matrix probed by fluorescence correlation spectroscopy.
The journal of physical chemistry. B, 2008Co-Authors: Carmen Reznik, Qusai Darugar, Andrea Wheat, Tim Fulghum, Rigoberto C. Advincula, Christy F. LandesAbstract:Diffusive transport within complex environments is a critical piece of the chemistry occurring in such diverse membrane systems as proton exchange and bilayer lipid membranes. In the present study, fluorescence correlation spectroscopy was used to evaluate diffusive charge transport within a strong polyelectrolyte Polymer Brush. The fluorescent cation rhodamine-6G was used as a counterion probe molecule, and the strong polyelectrolyte poly(styrene sulfonate) was the Polymer Brush. Such strong polyelectrolyte Brushes show promise for charge storage applications, and thus it is important to understand and tune their transport efficiencies. The Polymer Brush demonstrated preferential solvation of the probe counterion as compared to solvation by the aqueous solvent phase. Additionally, diffusion within the Polymer Brush was strongly inhibited, as evidenced by a decrease in diffusion constant of 4 orders of magnitude. It also proved possible to tune the transport characteristics by controlling the solvent pH, and thus the ionic strength of the solvent. The diffusion characteristics within the charged Brush system depend on the Brush density as well as the effective interaction potential between the probe ions and the Brush. In response to changes in ionic strength of the solution, it was found that these two properties act in opposition to each other within this strong polyelectrolyte Polymer Brush environment. A stochastic random walk model was developed to simulate interaction of a diffusing charged particle with a periodic potential, to show the response of characteristic diffusion times to electrostatic field strengths. The combined results of the experiments and simulations demonstrate that responsive diffusion characteristics in this Brush system are dominated by changes in Coulombic interactions rather than changes in Brush density. More generally, these results support the use of FCS to evaluate local charge transport properties within polyelectrolyte Brush systems, and demonstrate that the technique shows promise in the development of novel polyelectrolyte films for charge storage/transport materials.
Chao Wang - One of the best experts on this subject based on the ideXlab platform.
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Polymer Brush graft modified starch based nanoparticles as pickering emulsifiers
Langmuir, 2019Co-Authors: Xiaopeng Pei, Kankan Zhai, Chao Wang, Yukun Deng, Ying Tan, Baichao Zhang, Yungang BaiAbstract:We study biosourced core–shell particles with a starch-based core and thermo-responsive Polymer Brush shell using surface-initiated single-electron transfer living radical Polymerization (SI-SET-LR...
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Polymer Brush Graft-Modified Starch-Based Nanoparticles as Pickering Emulsifiers
2019Co-Authors: Xiaopeng Pei, Kankan Zhai, Chao Wang, Yukun Deng, Ying Tan, Baichao Zhang, Yungang Bai, Pixin WangAbstract:We study biosourced core–shell particles with a starch-based core and thermo-responsive Polymer Brush shell using surface-initiated single-electron transfer living radical Polymerization (SI-SET-LRP) as a Pickering stabilizer. The shell endows the Pickering stabilizer with reversible emulsification/demulsification of oil and water properties. The initiator attached to the starch-based nanosphere (Br-SNP) core particle was first fabricated using the precipitation method. Subsequently, dense poly(N-isopropylacrylamide) (PNIPAM) Brush graft-modified starch-based nanoparticles (SNP-g-PNIPAM) were obtained via the SI-SET-LRP process. Interfacial properties of the resultant particles were analyzed by interfacial tensiometer measurements, as were the effects of the grafted Polymer chain length and temperature on the interfacial activity. Pickering emulsion was obtained using SNP-g-PNIPAM particles as the stabilizer. The effect of the concentration of the Pickering stabilizer on the size of emulsion droplets was analyzed. The emulsification/demulsification process of the Pickering emulsion can be reversed and easily repeated by changing the temperature
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a water soluble phosphorescent conjugated Polymer Brush for tumor targeted photodynamic therapy
Polymer Chemistry, 2017Co-Authors: Pengfei Sun, Chao Wang, Gaina Wang, Huanzhi Hou, Pengcheng Yuan, Weixing Deng, Quli Fan, Wei HuangAbstract:Photodynamic therapy (PDT) has become a promising treatment approach against cancer due to low side effects and high therapeutic efficacy. However, the limitations of photosensitizers such as poor water solubility and lack of targeting ability hindered the clinical application of PDT. Here, we synthesized a phosphorescent conjugated Polymer Brush (PPF-Ir-g-(POEGMA-b-PGal)) in which a small photosensitizer iridium(III) complex was covalently attached to the conjugated backbone. A further hydrophilic Polymer (POEGMA) and glycoPolymer polygalactose (PGal), which has a specific binding ability with Hep G2 tumors, were grafted from the conjugated backbone via atom transfer radical Polymerization (ATRP) and click reaction. The Brush structure rendered PPF-Ir-g-(POEGMA-b-PGal) exhibited excellent water solubility. Meanwhile, PPF-Ir-g-(POEGMA-b-PGal) showed efficient properties of producing singlet oxygen. The photodynamic effect of the PPF-Ir-g-(POEGMA-b-PGal) photosensitizer was evaluated in Hep G2 cells via the MTT assay and flow cytometry and the results indicated that this photosensitizer can efficiently cause the death of cancer cells. Additionally, an antitumor study of PPF-Ir-g-(POEGMA-b-PGal) was conducted in vivo with Hep G2 tumor bearing nude mice, and the results show that the xenograft tumors were significantly inhibited. In summary, PPF-Ir-g-(POEGMA-b-PGal) exhibited fine water solubility and high PDT efficiency both in vitro and in vivo. Our study may further encourage the applications of conjugated Polymer Brush based photosensitizers for PDT in tumor treatment.
Xiaopeng Pei - One of the best experts on this subject based on the ideXlab platform.
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Polymer Brush graft modified starch based nanoparticles as pickering emulsifiers
Langmuir, 2019Co-Authors: Xiaopeng Pei, Kankan Zhai, Chao Wang, Yukun Deng, Ying Tan, Baichao Zhang, Yungang BaiAbstract:We study biosourced core–shell particles with a starch-based core and thermo-responsive Polymer Brush shell using surface-initiated single-electron transfer living radical Polymerization (SI-SET-LR...
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Polymer Brush Graft-Modified Starch-Based Nanoparticles as Pickering Emulsifiers
2019Co-Authors: Xiaopeng Pei, Kankan Zhai, Chao Wang, Yukun Deng, Ying Tan, Baichao Zhang, Yungang Bai, Pixin WangAbstract:We study biosourced core–shell particles with a starch-based core and thermo-responsive Polymer Brush shell using surface-initiated single-electron transfer living radical Polymerization (SI-SET-LRP) as a Pickering stabilizer. The shell endows the Pickering stabilizer with reversible emulsification/demulsification of oil and water properties. The initiator attached to the starch-based nanosphere (Br-SNP) core particle was first fabricated using the precipitation method. Subsequently, dense poly(N-isopropylacrylamide) (PNIPAM) Brush graft-modified starch-based nanoparticles (SNP-g-PNIPAM) were obtained via the SI-SET-LRP process. Interfacial properties of the resultant particles were analyzed by interfacial tensiometer measurements, as were the effects of the grafted Polymer chain length and temperature on the interfacial activity. Pickering emulsion was obtained using SNP-g-PNIPAM particles as the stabilizer. The effect of the concentration of the Pickering stabilizer on the size of emulsion droplets was analyzed. The emulsification/demulsification process of the Pickering emulsion can be reversed and easily repeated by changing the temperature
T. Kreer - One of the best experts on this subject based on the ideXlab platform.
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Polymer-Brush lubrication: a review of recent theoretical advances
Soft Matter, 2016Co-Authors: T. KreerAbstract:This review compiles recent theoretical advances to describe compressive and shear forces of Polymer-Brush bilayers, which consist of two opposing Brushes in contact. Such model systems for Polymer-Brush lubrication are frequently used as a benchmark to gain insight into biological problems, e.g., synovial joint lubrication. Based on scaling theory, I derive conformational and collective properties of Polymer-Brush bilayers in equilibrium and out-of-equilibrium situations, such as shear forces in the linear and nonlinear response regimes of stationary shear and under non-stationary shear. Furthermore, I discuss the influence of macromolecular inclusions and electrostatic interactions on Polymer-Brush lubrication. Comparisons to alternative analytical approaches, experiments and numerical results are performed. Special emphasis is given to methods for simulating Polymer-Brush bilayers using molecular dynamics simulations.
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Polymer Brush lubricated surfaces with colloidal inclusions under shear inversion
Physical Review Letters, 2011Co-Authors: L Spirin, T. Kreer, A Galuschko, K Binder, J BaschnagelAbstract:We characterize the response of compressed, sheared Polymer-Brush bilayers with colloidal inclusions to highly nonstationary inversion processes by means of molecular dynamics simulations and scaling theory. Bilayers with a simple (dimeric) solvent reveal an overshoot for the shear stress, while simulations of dry Brushes without explicit solvent molecules fail to display this effect. We demonstrate that mechanical instabilities can be controlled by the inclusion of macromolecular structures, such as colloids of varying softness. Based on a recently developed theory, we suggest a scaling approach to determine a characteristic time for conformational and collective responses.