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ABSTRACT: Crystallization behavior of water in a concentrated aqueous solution of poly(ethylene glycol) (PEG) with a water content of 37.5 wt% was investigated by temperature variable mid-infrared (mid-IR) spectroscopy in a temperature range of 298-170 K. The mid-IR spectrum of water at 298 K showed that a large water cluster was not formed and that most of the water molecules were associated with the PEG chain. Ice formation, however, occurred as found in previous studies by differential scanning calorimetory. Ice formations were grouped into three types: crystallization at 231 K during cooling, that at 198 K during heating, and that at 210 K during heating. The latter two were just recrystallization. These ice formations were the direct transition from hydration species to ice without condensation, regardless of crystallization or recrystallization. This means that the recrystallized water in the present system was not generated from low-density amorphous solid water. At a low cooling rate, nearly complete crystallization at 231 K during cooling and no recrystallization were observed. At a high cooling rate, no crystallization and two-step recrystallization at 198 K and 210 K were observed. The former and latter recrystallizations were found to be generated from water associated with the PEG chains with ttg and random conformations, respectively. These results indicate that recrystallizable water does not have a single specific water structure.
The Journal of Physical Chemistry B 01/2013; · 3.70 Impact Factor
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ABSTRACT: As a model of lipopeptide, a zwitterionic polymer-lipid conjugate was prepared from carboxymethylbetaine monomer (CMB) using a lipophilic initiator having a cholesteryl or dihexadecylglyceryl end group for atom transfer radical polymerization (ATRP). The polymer-lipid conjugates (Lipid-PCMB) obtained could be dispersed in water, and self-association of the compounds could be characterized by both light scattering (dynamic light scattering, DLS; electrophoretic light scattering, ELS) and small-angle X-ray scattering (SAXS). DLS and ELS measurements showed no secondary aggregation of the self-associated Lipid-PCMB molecules in salt solutions, though their surfaces were almost charge-balanced. The hydrophilic PCMB layer of Lipid-PCMB aggregates gave rise to dispersions under ionic conditions. Furthermore, structural analyses by DLS, ELS and SAXS measurements suggested that Lipid-PCMB aggregates consisted of a hydrophobic lipid core and a hydrophilic PCMB layer, that is, a core-shell structure. To the best our knowledge, this is the first study in which SAXS analyses were performed for zwitterionic polymer-lipid conjugates.
Journal of Colloid and Interface Science 10/2012; · 3.07 Impact Factor
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ABSTRACT: A zwitterionic poly(carboxymethylbetaine) (PCMB) brush was prepared on a fused quartz prism by the surface-initiated atom transfer radical polymerization (SI-ATRP) of CMB monomer. The conformation of PCMB brush and the state of water at the surface of the brush were examined using sum frequency generation (SFG) technique. The C-H stretching band of the brush, indicating the gauche defect of the brush, was affected by the contact medium such as dry nitrogen, water vapor-saturated nitrogen and liquid water. The water molecules at the PCMB-water interfaces were not largely oriented in comparison with the interfacial water of both bare and the ATRP-initiator-modified quartz prisms. The similar tendency was previously observed for water in the vicinity of water-soluble zwitterionic polymers and polymer thin films using Raman and attenuated total reflection (ATR) infrared spectroscopies, respectively. The electrical neutralization between neighboring positive and negative charges might diminish the electrostatic adsorption of water molecules to the vicinity of zwitterionic polymer brushes.
Colloids and surfaces. B, Biointerfaces 05/2012; 100:126-32. · 2.60 Impact Factor
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ABSTRACT: A glycopolymer obtained by living radical polymerization of glucose-carrying vinyl monomer was sulfated and accumulated as a polymer brush on a gold colloid-immobilized glass. Binding processes of various proteins to sulfated glucose residues in the brush were examined by the increase in absorbance with a help of localized surface plasmon resonance. β-Amyloid protein (Aβ) bound to the sulfated glycopolymer brush, whereas no binding to the non-sulfated one. An AFM image of Aβ aggregates on the sulfated brush was ellipsoidal, whereas no-shaped aggregation of Aβ on the poly(methacrylic acid) and poly[2-(dimethylamino)ethyl methacrylate] brushes. The present results indicate the importance of balance between electrostatic attraction and repulsion in the folding-aggregation phenomena of Aβ at the surface of glycopolymers.
Colloids and surfaces. B, Biointerfaces 05/2012; 93:219-25. · 2.60 Impact Factor
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ABSTRACT: Drying patterns of colloidal crystals of colloidal silica spheres coated with the brushes of zwitterionic poly(carboxymethyl
betaine) (SiP-PCMB) and their parent silica spheres (SiP) were studied on a cover glass, a watch glass, and a Petri glass
dish. Crystal structures kept the whole process of dryness of the suspensions of SiP-PCMB and SiP. Crystal structures of the
dried films of SiP-PCMB were kept stable even when the initial suspensions contained 5mM of sodium chloride, which is the
important role of the excluded volume effects of the shells of the polymer brushes. On the other hand, crystal structures
of SiP spheres in the dried films were much unstable and melted in the presence of 5mM sodium chloride. In the suspension
state, colloidal crystallization of SiP-PCMB took place stably by the contribution of the excluded volume effects besides
the extended electrical double layers compared with that of SiP spheres, where only the double layer effect contributes to
the crystallization. The fractal patterns of the complexation of SiP-PCMB or SiP spheres with sodium chloride were observed
microscopically in the dried films. Several kinds of dissipative crystallization such as array and/or accumulation of the
crystallites were observed, and the importance of the convectional and sedimentation processes during the course of dryness
was demonstrated.
KeywordsDrying dissipative structure-Colloidal crystal-Polymer brush-Poly(carboxymethyl betaine)-Broad ring
Colloid and Polymer Science 04/2012; 288(12):1233-1243. · 2.33 Impact Factor
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ABSTRACT: Change in the state of water sorbed into four kinds of non-water-soluble poly(meth)acrylates with low water content by temperature (T) perturbation was examined on the basis of T variable mid-infrared (MIR) spectroscopy. Many studies using differential scanning calorimetry suggested that there was no change in the state. T dependence of their MIR spectra, however, clearly demonstrated various changes in the state. Furthermore, recrystallization, which was crystallization during heating, was observed in all four polymers. The recrystallization observed in this study was not devitrification, which is the change in the state from glassy water to crystalline water, but vapor deposition during heating (vapor re-deposition). There were only two reports about recrystallization of water in a non-water-soluble polymer before this report; therefore, it might be considered to be a rare phenomenon. However, as demonstrated in this study, it is not a rare phenomenon. Recrystallization (vapor re-deposition) of water in the polymer matrices is related to a balance between flexibility and strength of the electrostatic interaction sites of polymer matrices but might not be related to the biocompatibility of polymers.
The Journal of Physical Chemistry B 02/2012; 116(6):1850-7. · 3.70 Impact Factor
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ABSTRACT: A random copolymer of zwitterionic monomer, carboxymethylbetaine (CMB), and 3-methacryloyloxypropyl trimethoxysilane was prepared in ethanol using 2,2'-azobisisobutyronitrile as initiator. The incubation of ethanol solution of the copolymer with a glass plate gave a layer of the copolymer with a thickness of about 2-3 nm. The copolymer-modified glass substrate became highly hydrophilic upon immersion in water, and showed a resistance against non-specific adsorption of proteins, and the degree of resistance increased with the content of CMB residues in the copolymer and leveled off. The adhesion of various cells to the glass substrate was also strongly suppressed by the surface modification with the copolymer layer. Further introduction of PolyCMB graft chains on the surface of the layer enhanced the suppression of cell adhesion due to the steric hindrance for the cells to approach the layer. The usefulness of the combination of zwitterionic polymer layer and graft chains to afford anti-biofouling properties to a solid surface of metal oxides was shown.
Colloids and surfaces. B, Biointerfaces 02/2012; 94:107-13. · 2.60 Impact Factor
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ABSTRACT: A polyampholyte brush was prepared on the surface of a quartz prism by surface-initiated reversible addition-fragmentation chain-transfer polymerization of methacrylic acid (MA) and 2-(dimethylamino)ethyl methacrylate (DMAEMA) at a monomer ratio of 1:1. The sum frequency generation method indicated that water molecules at the amphoteric polymer brush-water interfaces were not greatly oriented in comparison with those at the surfaces of bare quartz prisms, and negatively charged PolyMA and positively charged PolyDMAEMA brushes. The small perturbation effect of an amphoteric polymer brush on the structure of vicinal water was in accordance with the tendency of aqueous solution and thin films of amphoteric polymers observed by using Raman and infrared spectroscopies, respectively.
Colloids and surfaces. B, Biointerfaces 11/2011; 91:215-8. · 2.60 Impact Factor
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ABSTRACT: An amphoteric copolymer brush of methacrylic acid (MA) and 2-(dimethylamino)ethyl methacrylate (DMAEMA) was prepared by reversible addition-fragmentation chain-transfer (RAFT) polymerization using both a free chain transfer agent (n-butylsulfanylthiocarbonylsulfanyl-2-methyl propionic acid) and a radical initiator (4,4'-azobis(4-cyanopentanoic acid)) covalently fixed to a glass substrate. An aqueous solution of the copolymer, Poly(MA-r-DMAEMA), which was simultaneously obtained in liquid phase, had a sufficiently small polydispersity in its molecular weight. The copolymer brush showed effective suppression of non-specific adsorption of bovine serum albumin and egg white lysozyme to the brush. In contrast, both negatively charged PolyMA and positively charged PolyDMAEMA brushes significantly adsorbed the proteins irrespective of their net charges. Upon ion beam irradiation, furthermore, a hollow space with a designed shape could be made on the glass substrate, and both HEK293 and HepG2 cells non-specifically adhered to the space, forming aggregates, while no adhesion to the non-treated area on the brush was observed. These results suggest that the amphoteric polymer brushes will be useful materials for biomedical applications.
Colloids and surfaces. B, Biointerfaces 07/2011; 88(1):455-62. · 2.60 Impact Factor
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ABSTRACT: Silica particles (SiP) were modified with 2-bromoisobutyryl group-carrying silane coupling reagent, and a polymer brush of carboxymethylbetaine, poly[1-carboxy-N,N-dimethyl-N-(2'-methacryloyloxyethyl)methanaminium inner salt] (PolyCMB), was introduced onto surface of the particles using surface-initiated atom transfer radical polymerization (ATRP). After purification by simple ultrafiltration, the layer of the PolyCMB brush-carrying silica particle (SiP-PolyCMB) in aqueous medium showed a clear iridescence at the bottom of a quartz cell upon a slow sedimentation, indicating the formation of colloidal crystals due to both electrostatic and steric repulsion between the particles. The peak of the reflection spectra gradually shifted to a smaller wavelength region due to the formation of more densely packed ordered structure of the SiP-PolyCMB. Moreover, SiP-PolyCMBs dispersed in water showed neither salt- nor freeze-thaw cycle-induced coagulation, and were resistant against the non-specific adsorption of proteins such as bovine serum albumin and egg white lysozyme, which is in contrast with the noticeable adsorption of the proteins to the bare silica particles.
Colloids and surfaces. B, Biointerfaces 05/2011; 84(1):111-6. · 2.60 Impact Factor
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ABSTRACT: A CMB monomer was polymerized on a glass plate with a surface-confined ATRP initiator containing a 2-bromoisobutyryl group. The glass plate modified with a PCMB brush was highly hydrophilic and showed a strong resistance against non-specific adsorption of proteins and cell adhesion. Upon ion beam irradiation, furthermore, the PCMB brush was ablated and a hollow space with a designed shape could be made to which HEK293 cells (from human embryonic kidney) and Hep G2 (from human hepatoma) cells non-specifically adhered, while no adhesion of these cells to the non-treated area on the brush was observed. The present results clearly indicate the usefulness of ion beam-printed patterns of anti-biofouling zwitterionic polymer brushes in the biomedical field.
Macromolecular Bioscience 01/2011; 11(4):557-64. · 3.89 Impact Factor
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ABSTRACT: A novel vinyl monomer, 3-dimethylamino-6-(p-methacrylamidophenylazo)phenylboronic acid (AzoPBA), which had been prepared by the coupling of p-aminophenyl methacrylamide hydrochloride with m-dimethylaminophenylboronic acid in the presence of sodium nitrite, was polymerized with 3-dimethylaminopropylacrylamide (DMAPAA). The copolymer obtained (Poly(DMAPAA/AzoPBA)) bound to sugars such as fructose and glucose in a weakly alkaline region (8 < pH), which was indicated by the absorbance change of the diphenylazo group at 557 nm. In contrast with this, a copolymer of N,N-dimethylacrylamide (DMAA) and the AzoPBA (Poly(DMAA/AzoPBA)) bound to sugars in a more alkaline region (9 < pH). The larger sensitivity of the former copolymer to the sugars than the latter in a weakly alkaline region is due to the supporting effect of tertiary amino group in the DMAPAA residue to the binding of sugar to the phenylboronic acid moiety. The association constant (K) of boronic acid residue in these copolymers with fructose was larger than that with glucose. These results indicated the usefulness of the DMAPAA/AzoPBA copolymer for the sensing of sugars in the weakly alkaline region near the physiological pH.
Colloids and surfaces. B, Biointerfaces 09/2010; 79(2):434-9. · 2.60 Impact Factor
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ABSTRACT: 3-Sulfo-N,N-dimethyl-N-(2'-methacryloyloxyethyl)propanaminium inner salt (SPB) was polymerized on a glass plate with a surface-confined initiator of atom transfer radical polymerization (ATRP) having a 2-bromoisobutyryl group. The glass plate modified with a brush of sulfobetaine telomer (PSPB) was highly hydrophilic and showed a strong resistance against nonspecific adsorption of proteins such as lysozyme and albumin. Through the polymerization from the free surface of PSPB chain by ATRP, furthermore, N-methacryloyloxysuccinimide (MAOSu) residues were introduced, and the incubation of the telomer (PSPB-b-PMAOSu)-modified glass chip with a lectin (concanavalin A, Con A) gave a glass chip covered with the Con-A-modified PSPB brush. The Con A fixed to the zwitterionic telomer brush pursued specific binding of mannose residues accumulated on the surface of Au colloidal particles, resulting in the increase in absorbance at 550 nm ascribable to localized surface plasmon resonance, while the nonspecific adsorption of proteins to the surface of the glass chip was still largely suppressed. The present results indicate usefulness of the zwitterionic telomer surface with antibiofouling properties as a scaffold for specific sensing devices.
Langmuir 05/2010; 26(9):6767-74. · 4.19 Impact Factor
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ABSTRACT: Possible phase transition of water in polymer-water systems has been understood (assumed) to be only either freezing/melting or nothing, without relation to whether the polymer was soluble in water or whether its water content was high or low. This general understanding of water structure has been structured on the basis of calorimetric analyses such as differential scanning calorimetry, DSC. DSC is one of the most frequently used methods to analyze the water structure in polymer-water systems because the data obtained are relatively easy to interpret. This easiness of interpretation, however, can be accepted only if based on the understanding stated above. Unexpectedly, results of the infrared spectroscopic analysis presented here completely denied the general understanding and provided definite evidence of the existence of all phase transitions among the three states of water in a polymer solid. Furthermore, the impossibility of detection of condensation, deposition, sublimation, and vaporization by calorimetric analysis was revealed.
The Journal of Physical Chemistry B 03/2010; 114(12):4310-2. · 3.70 Impact Factor
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ABSTRACT: A novel disulfide, which carried a specific inhibitor for beta-secretase (KMI360) at both ends, was prepared by the coupling of 11,11'-dithiobisundecanoic acid (DTUA) with the inhibitor. The compound obtained (DTUA-KMI360) formed a self-assembled monolayer (SAM) on a gold electrode as proven by cyclic voltammetry (CV) using hydroquinone as a probe. Furthermore, DTUA-KMI360 could be accumulated as a SAM on a gold colloid deposited on a glass plate (Au colloid-glass chip) as proven by both the red-shift and the increase in absorbance of the gold colloid corresponding to localized surface plasmon resonance (LSPR). When the SAM-modified Au colloid-glass chip was immersed in a solution of aspartyl proteases, pepsin and beta-secretase, the absorbance of the chip at 550nm corresponding to LSPR of the gold colloid further increased and was slightly red-shifted, whereas coexistence of a free inhibitor obstructed these phenomena. Adsorption of the enzymes was promoted by the incorporation of a zwitterionic group into the SAM, while non-specific adsorption to the mixed SAM was significantly reduced. The optimal ratio of omega-zwitterionic alkanethiol, 3-[(6-mercaptohexyl)-N,N-dimethylamino]propane-1-sulfonic acid (C(6)-SPB), and DTUA-KMI360 in the SAM for the binding of enzymes was found to be DTUA-KMI360:C(6)-SPB=1:11 using polarization modulation infrared reflection absorption spectroscopy (PM-IR-RAS). From increasing profiles of absorbance of the Au colloid-glass chip, the association constant (K(assoc)) for pepsin with the inhibitor on the SAM was determined, whereas that for beta-secretase could not be due to the strong binding of the enzyme to the inhibitor, resulting in the absence of the dissociation process. The results suggested that the SAM of the enzyme inhibitor can be used for both investigation of enzymes and removal of target enzymes from biological fluids.
Colloids and surfaces. B, Biointerfaces 02/2010; 78(2):155-62. · 2.60 Impact Factor
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ABSTRACT: The water incorporated in a thin film of amphoteric terpolymers composed of various ratios of methacrylic acid (MA), N-[3-(dimethylamino)propyl]methacrylamide (DMAPMA) and n-butyl methacrylate was analyzed using the band shapes of the O-H stretching in the infrared spectra. At an early stage of sorption of water into the polymer film, the O-H stretching band for the water incorporated in the film with comparative contents of MA and DMAPMA residues was similar to that for bulk water. These results clearly indicate that the amphoteric polymers with comparative contents of cationic and anionic groups do not significantly disturb the hydrogen-bonded network structure of water, probably due to the counteraction of the electrostatic hydration effect by the proximity between the anionic and cationic side groups. The number of platelets adhered to the film with comparative contents of MA and DMAPMA residues was relatively the smallest among the examined terpolymer films, which suggested a correlation between the mildness of the charge-balanced polymeric materials to the structure of incorporated water and their blood-compatibilities. In addition, the structure and hydrogen bonding of water in an aqueous solution of co-polymers composed of various ratios of MA and DMAPMA or [3-(methacryloylamino)propyl]trimethylammonium chloride (MAPTAC) were also analyzed using the contours of the O-H stretching in the polarized Raman spectra. The number of hydrogen bonds disrupted due to the presence of one monomer residue (N(corr) value) for PolyMA was largely positive, and with an increase in the content of the DMAPMA or MAPTAC residues, the N(corr) value became smaller, and after passing a minimum (which was still slightly positive) at a roughly equivalent molar ratio, the N(corr) value increased again. This is in a significant contrast with the largely positive N(corr) values for the homo-polymers (PolyMA, PolyDMAPMA and PolyMAPTAC), and other ordinary polyelectrolytes. The effect of the charge-balanced co-polymer on the hydrogen-bonded network structure of vicinal water observed by Raman spectroscopy was in accordance with that of the charge-balanced terpolymer film observed by infrared spectroscopy.
Journal of Biomaterials Science Polymer Edition 01/2010; 21(14):1877-93. · 1.69 Impact Factor
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ABSTRACT: A polymer brush of 2-(2-methoxyethoxy)ethyl methacrylate (MDM) was prepared by atom transfer radical polymerization (ATRP) using a 11-(2-bromoisobutyroyloxy)undecyl moiety-carrying initiator covalently fixed to a glass substrate. An aqueous solution of the MDM polymer (E-PMDM), which had been prepared for comparison, turned to be opaque above certain temperature (26.2°C for E-PMDM (M(n,GPC)=1.84×10(4))), which was corresponding to the lower critical solution temperature (LCST) of the polymer. The PMDM polymer brush accumulated on the glass surface also indicated temperature-responsive changes in contact angle of air bubble in the air-in-water system. Furthermore, non-specific adsorption of various proteins (bovine serum albumin (BSA), human immunoglobulin G (IgG) and bovine plasma fibrinogen (BPF)) to the surface of polymer brush on the glass plate was examined by the bicinchoninic acid method. The PMDM brush did not adsorb IgG and BPF significantly below the LCST of the polymer chain, whereas adsorbed a larger amount of the proteins above the LCST. A similar but less significant temperature-responsive adsorption was observed in the case of BSA. These results suggest usability of the temperature-responsive polymer-brushes with pendent ω-methoxy oligo(ethylene glycol) groups to coat various materials for bio-medical applications.
Journal of Colloid and Interface Science 10/2009; 345(2):325-31. · 3.07 Impact Factor
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ABSTRACT: A thiol-group-carrying telomer with pendent D-glucosylurea groups [poly(glucosylureaethyl methacrylate)-SH (PolyGUMA-SH)] was obtained by reversible addition-fragmentation chain-transfer (RAFT) polymerization of GUMA in the presence of 4,4'-azobis(4-cyanopentanoic acid) (initiator) and 4-cyanopentanoic acid dithiobenzoate (chain-transfer agent) and subsequent reduction with NaBH4. The thiol-carrying telomer was accumulated on both a gold electrode and a colloidal gold-immobilized glass substrate as proven by cyclic voltammetry using hydroquinone as a probe, and the increase in absorbance at 550 nm was ascribable to localized surface plasmon resonance (LSPR), respectively. The adsorption of various proteins to the surface of the telomer brush was examined by the LSPR method, too. The PolyGUMA brush showed a significant resistance against nonspecific adsorption of proteins, such as lysozyme, bovine serum albumin, immunoglobulin G, and fibrinogen. Furthermore, sugar-binding proteins, concanavalin A (Con A, with an affinity for mannose and glucose) and wheat germ agglutinin (WGA, with an affinity for N-acetylglucosamine), were not adsorbed to the GUMA-carrying brush, which is in contrast with the prompt and distinct binding of these proteins to the telomer brushes composed of 2-methacryloyloxyethyl D-glucopyranoside (Con A) and 1-O-(6'-methacrylamido)hexyl-2-N-acetoamido-2-deoxy-D-glucopyranoside residues (WGA). The glucosylurea-group-carrying telomer brush prepared here might be quite useful to provide a "bio-inert (anti-biofouling)" surface in biomedical fields.
Langmuir 07/2009; 25(16):9361-8. · 4.19 Impact Factor
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ABSTRACT: Telechelic poly(n-butyl methacrylate)s (PBMAs) with various end groups were prepared using nonionic, anionic, cationic or zwitterionic azo-type radical initiators and cell adhesion onto the surfaces of the polymers was investigated. The tendency for cell adhesion to the polymers differed with and without pretreatment with phosphate-buffered saline (PBS, pH 7.4). The cell adhesion to polymer surfaces without pretreatment was lower than that with pretreatment. The effect of pretreatment with PBS was significant for PBMA with ionic end groups. Furthermore, cell adhesion to the surface of PBMA with zwitterionic end groups was suppressed compared with that to the surfaces of other polymers. It was presumed that positive and negative charges of zwitterionic groups in the same molecule negated each other at pH 7.4 and that the polymers with zwitterionic end groups had no effective charges. The results clearly indicated that biocompatibility of polymers can be changed by the introduction of functional groups at the ends of the polymer chains. Fabrication of functional material surfaces will be anticipated by the similar method in the future.
Colloids and surfaces. B, Biointerfaces 07/2009; 74(1):45-50. · 2.60 Impact Factor
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ABSTRACT: A disulfide-carrying polymer with many pendent mannose residues (dithiolated poly(2-methacryloyloxyethyl D-mannopyranoside)) was obtained by atom transfer radical polymerization (ATRP) method using 2-(2'-bromoisobutyroyloxy)ethyl disulfide as initiator. The obtained disulfide-carrying glycopolymer (DT-PMEMan) was accumulated as a polymer brush on a colloidal gold-immobilized glass substrate, and the binding processes of a lectin, Concanavalin A (Con A), to mannose residues in the polymer brush were examined using a UV-vis spectrophotometer with the help of a localized surface plasmon resonance. Con A showed a concentration-dependent specific binding to the glycopolymer brush, and the apparent association constant of Con A with mannose residues in the brush was much larger than the association constant for small sugars due to the so-called cluster effect. Furthermore, the glycopolymer brush-coated device had a detection limit lower than 5 nM. The glycopolymer-carrying device examined here is expected to expand our knowledge of recognition phenomena at the surface of polymer brushes.
Colloids and surfaces. B, Biointerfaces 01/2009; 70(1):91-7. · 2.60 Impact Factor
