Hydrothermal preparation of mesoporous TiO2 powder from Ti(SO4)2 with poly(ethylene glycol) as template

Mesoporous titania powder with anatase structure was prepared by hydrothermal synthesis from low-cost Ti(SO₄)₂ water solution with nontoxic poly ethylene glycol (PEG) as a templating agent. The templating pathway was suggested to use hydrogen bonding interaction between the hydrophilic surfaces of flexible rod- or worm-like micelles and the hydrothermal products of Ti(OH)₄ to assemble an inorganic oxide framework. The mesoporous channel structures with diameters about 3 nm to 18 nm were achieved by adding appropriate amount of PEG with average moelcular weight of 200. The obtained powder showed good performance for the degradation of gaseous formaldehyde. These results suggested that hydrothermal synthesis with PEG templating provided a low-cost and convenient pathway to synthesis mesoporous TiO₂ powder from water solution system.     

Nanostructured antifouling poly(ethylene glycol) films for silicon-based microsystems

The creation of antifouling surfaces is one of the major prerequisites for silicon-based micro-electrical-mechanical systems for biomedical and analytical applications (known as BioMEMS). Poly(ethylene glycol) (PEG), a water-soluble, nontoxic, and nonimmunogenic polymer has the unique ability to reduce nonspecific protein adsorption and cell adhesion and, therefore, is generally coupled with a wide variety of surfaces to improve their biocompatibility. To this end, we have analyzed PEG thin films of various grafting densities (i.e., number of PEG chains per unit area) coupled to silicon using a single-step PEG-silane coupling reaction scheme using variable-angle ellipsometry. Initial PEG concentration and coupling time were varied to attain different grafting densities. These data were theoretically analyzed to understand the phenomenon of PEG film formation. Furthermore, all the PEG films were evaluated for their ability to control biofouling using albumin and fibrinogen as the model proteins. PEG thin films formed by using higher PEG concentrations ( > or = 10 mM PEG) or coupling time ( > or = 1 h) demonstrated enhanced protein fouling resistance behavior. This analysis is expected to be useful to form PEG films of desired grafting density on silicon substrates for appropriate application.     

Poly(ethylene glycol) decorated poly(methylmethacrylate) nanoparticles for protein adsorption

Poly(ethylene glycol) decorated poly(methyl methacrylate) particles were synthesized by means of emulsion polymerization using poly(ethylene glycol) sorbitan monolaurate (Tween-20) as surfactant. PMMA/PEG particles presented mean diameter (195 ± 15) nm, indicating narrow size distribution. The adsorption behavior of bovine serum albumin (BSA) and concanavalin A (ConA) onto PMMA/PEG particles was investigated by means of spectrophotometry. Adsorption isotherms obtained for BSA onto PMMA/PEG particles fitted well sigmoidal function, which is typical for multilayer adsorption. Con A adsorbed irreversibly onto PMMA/PEG particles. The efficiency of ConA covered particles to induce dengue virus quick agglutination was evaluated.     

Biocompatibility and biodegradation of poly(hydroxybutyrate)/poly(ethylene glycol) blend films

Using chloroform as co-solvent, a series of poly(3-hydroxybutyrate) (PHB) and polyethylene glycol (PEG) blend materials with different ratio ranging from 80 : 20 (wt %) to 20 : 80 (wt %) were prepared by solution blend. The blood-compatibility was evaluated by means of platelet clotting time test and exploring its morphological changes. The results showed that PEG played an important role in resisting platelet adhesion. With the increased addition of PEG, the clotting times became longer and the number of platelet adhesion decreased apparently. All platelets were in discrete state, no pseudopodium had been found and no collective phenomenon had been happened. The cell-compatibility was evaluated via Chinese Hamster Lung (CHL) fibroblast cultivation in vitro. The cells cultured on the matrix spread and proliferated well. With the increase of PEG content in the blend films, the number of live cells became more and more. These results indicated that PHB exhibited satisfying cell-compatibility and the addition of PEG also could improve the cell-compatibility of PHB. The biodegradation experiment indicated that the degradation of PHB/PEG was accelerated by enzyme in vitro and the blending of PEG was favorable to degradation.     

Preparation and characterization of functional poly(ethylene glycol) surfaces for the use of antibody microarrays

Protein microarrays serve as measurement platforms for multianalytical applications. Small molecules, DNA, proteins, and cells are determined quantitatively. Amino-PEG surfaces can be a smart functional platform for protein microarrays with high signal-to-noise ratios. An effective step-by-step chemistry is developed for uniform presentation of terminal functional groups at each monolayer. Poly(ethelene glycol diamine) 2000 (DAPEG, 2000 g/mol) films were prepared onto silanized glass slides presenting epoxy groups. The uniformity of the grafted DAPEG monolayer is characterized by a chemiluminescence reaction using a chemiluminescence microarray reader with automated reagent supply and a horseradish peroxidase (HRP)/luminol reporter system. An intensity line plot on the horizontal axis was generated. The chemiluminescence intensities vary in a range of 2.6%. Antibodies against HRP as model system were immobilized on N-hydroxysuccinimide activated DAPEG layers by means of a microcontact roboter system. Chemiluminescence signals of bound HRP are detected at each spot with a standard deviation of 2.9%. The maximum antibody concentration that can be immobilized at the surface is determined with 1 mg/mL. Additives for an optimal spotting buffer are also studied. The use of the block-copolymer Pluronic F127 as antibody stabilizer is as well investigated as trehalose for the prevention of spot evaporation. The lowest detectable HRP concentration is 0.08 ng/mL determined on anti-HRP antibody microarrays. This study demonstrates how surfaces and analytical parameters for protein microarray applications can be characterized with a chemiluminescence readout system using a HRP reporter system.     

Controlled ambipolar-to-unipolar conversion in graphene field-effect transistors through surface coating with poly(ethylene imine)/poly(ethylene glycol) films

A controlled ambipolar-to-unipolar (n-type) conversion, along with a maximum fourfold increase in the electron mobility, in graphene field-effect transistors (FETs) is achieved by coating the surface of graphene with a layer of a mixed polymer system, poly(ethylene imine) (PEI) in poly(ethylene glycol) (PEG). The PEG serves as a physisorption adhesion agent for the PEI. Both unipolar and ambipolar n-type doping can be realized by adjusting the thickness of PEI films atop the graphene channel. The observed phenomena are attributed to the doping/dedoping effects of the external PEI film. The study provides a guide to engineering graphene transport properties through chemical modifications.     

Physicochemical characterization of densely packed poly(ethylene glycol) layer for minimizing nonspecific protein adsorption

Modification of the surface with densely packed poly(ethylene glycol) (PEG) brush layer was studied to improve the protein repellent ability of the surface. A PEG-brushed layer was constructed on a gold substrate using a PEG possessing a mercapto group at the chain end. The density of the PEG brushed layer substantially increased with repetitive adsorption/rinse cycles of the PEG on the gold substrate, allowing dramatic reduction of nonspecific protein adsorption. Notably, formation of a short, filler layer of PEG (2 kDa) in the preconstructed longer PEG brushed layer (5 kDa) achieved high density brush and almost complete prevention of nonspecific protein adsorption. On the other hand, surface modification with only long PEG chain (5 kDa) showed lower PEG brush density regardless of repetitive immobilization. Detailed characterization of the PEGylated surface was done from the physicochemical (QCM, contact angle, and SPR) as well as the biological (protein adsorption) point of view to highlight the relation between the PEG brush density and the protein repellent ability. Densely packed PEG surface which showed great protein repellent ability, presented in this study, suggests promising utility as engineered biomaterials including high-throughput screening and clinical diagnostics.     

Effect of surface charge on osteoblastic proliferation and differentiation on a poly(ethylene glycol)-diacrylate hydrogel

Two charge monomers, namely 2-(methacryloyloxy)ethyl-trimethylammonium chloride (MAETAC) and sodium methacrylate (SMA), were incorporated into poly(ethylene glycol)-diacrylate (PEGDA) hydrogels to investigate the effects of surface charge on the proliferation and differentiation of osteoblasts. The physicochemical properties of the polymers were characterized, and MC3T3-E1 cells were seeded on the hydrogels to evaluate the effect of charge polarity and density on osteoblastic proliferation and differentiation. FTIR results revealed that the two charged monomers were successfully incorporated into PEGDA. The zeta potential of the hydrogels became more positive or negative with increasing concentration of MAETAC or SMA. The zeta potential of the charged hydrogels remained constant after immersion in culture medium for different time points. Other physicochemical properties such as surface morphology, swelling ratio in PBS, contact angle, and elastic modulus were not significantly different among each group with different concentrations of charge monomers incorporated into PEGDA. The modification of hydrogels with charge monomers not only improved osteoblastic proliferation but also upregulated alkaline phosphatase activity and the expression of osteogenic marker genes and relative growth factors. These findings indicate that, in contrast to charge polarity, the charge density would be more important to improve osteoblast-like cells proliferation and differentiation on the poly(ethylene glycol)-diacrylate hydrogel. The hydrogel can be designed by controlling the incorporation of charge monomers. This study provides a model to study the effect of charge on cell behavior.     

Preparation of porous polyacrylate/poly(ethylene glycol) interpenetrating network hydrogel and simplification of Flory theory

In this article, we successfully designed and fabricated polyacrylate/poly(ethylene glycol) interpenetrating network (PAC/PEG IPN) hydrogel by a two-step technique. The influences of synthesis parameters, such as crosslinker dosage and neutralization degree of PAC, on the equilibrium swelling ratio (SR) of the PAC/PEG IPN hydrogel were investigated. Based on Flory theory, a simplified experiential formula was proposed. The results revealed that the theoretical SR of the PAC/PEG IPN hydrogel was consistent with experimental value in the presence of univalent salt solution. In this case, the SR of the hydrogel can be calculated without measurement. While for multivalent salt solutions, the theoretical and experimental results are inconsistent owing to chelations between carboxylic and carboxylate groups of the PAC/PEG hydrogels and the cations in the solution.     

Iron-included carbon nanocapsules coated with biocompatible poly(ethylene glycol) shells

Nanoparticles of iron carbides wrapped in multilayered graphitic sheets (carbon nanocapsules) were synthesized by electric plasma discharge in an ultrasonic cavitation field in liquid ethanol and purified by selective oxidation and magnetic separation. The particles had 100–200 nm in diameter after centrifuging for 10 min at 4000 rpm. Carbon nanocapsules were covered by wispy poly(ethylene glycol) PEG coating about 7–10 nm in thickness. The number of PEG chains coated on carbon nanocapsules could be estimated as 9.15%. The values of saturation magnetization Ms and coercivity Hc of purified carbon nanocapsules without PEG coating were 112 emu g⁻¹ and 75 Oe respectively. Magnetically soft carbon nanocapsules with a poly(ethylene glycol) coating on the surface may possibly be used as biocompatible magnetic nanoparticles in medical applications.     

Assembly and degradation of low-fouling click-functionalized poly(ethylene glycol)-based multilayer films and capsules

Nano-/micrometer-scaled films and capsules made of low-fouling materials such as poly(ethylene glycol) (PEG) are of interest for drug delivery and tissue engineering applications. Herein, the assembly and degradation of low-fouling, alkyne-functionalized PEG (PEG(Alk) ) multilayer films and capsules, which are prepared by combining layer-by-layer (LbL) assembly and click chemistry, are reported. A nonlinear, temperature-responsive PEG(Alk) is synthesized, and is then used to form hydrogen-bonded multilayers with poly(methacrylic acid) (PMA) at pH 5. The thermoresponsive behavior of PEG(Alk) is exploited to tailor film buildup by adjusting the assembly conditions. Using alkyne-azide click chemistry, PEG(Alk)/PMA multilayers are crosslinked with a bisazide linker that contains a disulfide bond, rendering these films and capsules redox-responsive. At pH 7, by disrupting the hydrogen bonding between the polymers, PEG(Alk) LbL films and PEG(Alk) -based capsules are obtained. These films exhibit specific deconstruction properties under simulated intracellular reducing conditions, but remain stable at physiological pH, suggesting potential applications in controlled drug release. The low-fouling properties of the PEG films are confirmed by incubation with human serum and a blood clot. Additionally, these capsules showed negligible toxicity to human cells.     

Surface modification of natural rubber latex films via grafting of poly(ethylene glycol) for reduction in protein adsorption and platelet adhesion

Natural rubber (NR) latex films with surface grafted poly(ethylene glycol) (PEG) chains were prepared by UV-induced graft copolymerization of methoxy poly(ethylene glycol) monomethacrylate (PEGMA) onto the plasma-pretreated NR latex films. PEGMA macromononers of different molecular weights were used. The UV-induced graft copolymerization of PEGMA onto the plasma-pretreated NR latex films was also explored with PEGMA of different macromonomer concentrations and with different UV graft copolymerization time. The surface microstructures and compositions of the PEG-modified NR latex films were characterized by contact angle, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) measurements. In general, higher macromonomer concentration and longer UV graft copolymerization time led to a higher graft yield. Water contact angle measurements revealed that the hydrophilicity of the NR latex film surface was greatly enhanced by the grafting of the PEG chains. The NR surface with a high density of grafted PEG was very effective in reducing protein adsorption and platelet adhesion. A lower graft concentration of the high-molecular-weight PEG was more effective than a high graft concentration of the low-molecular-weight PEG in reducing protein adsorption and platelet adhesion. © 2001 Kluwer Academic Publishers     

透明质酸/胶原蛋白/聚乙二醇复合水凝胶的研究

针对透明质酸、胶原蛋白水凝胶力学性能差的问题,采用两步交联法将透明质酸、胶原蛋白与聚乙二醇双丙烯酸酯制备成一种兼具生物相容性和高强度的复合水凝胶。研究制备了具有相同胶原蛋白和聚乙二醇双丙烯酸酯质量分数,不同透明质酸质量分数的水凝胶,从微观结构和力学强度调控了复合水凝胶的理化性能,并用L-赖氨酸对复合凝胶进行改性。SEM结果表明,三元复合水凝胶具有蜂窝状的内部结构,孔径范围在80~180μm,赖氨酸浓度达40 mmol/L时,水凝胶的压缩模量达414 k Pa,是改性前模量的19倍。细胞毒性和体内植入实验表明该水凝胶浸提环境对细胞生长无明显抑制作用,产生较低的免疫排斥反应,有望用于软骨等组织的修复。     

DNA directed protein immobilization on mixed ssDNA/oligo(ethylene glycol) self-assembled monolayers for sensitive biosensors

A stable and versatile biosensor surface is prepared by site-directed immobilization of protein-DNA conjugates onto a mixed self-assembled monolayer (SAM) composed of ssDNA thiols and oligo(ethylene glycol) (OEG) terminated thiols. The protein conjugates consist of an antibody chemically linked to a ssDNA target with a sequence complementary to the surface-bound ssDNA probes and are immobilized on the surface via sequence-specific hybridization. Compared to standard antibody immobilization techniques, this approach offers many advantages. The exceptional specificity of DNA hybridization combined with the diversity of potential sequences makes this platform perfect for multichannel sensors. Once a surface is patterned with the appropriate probe sequences, sequence-specific hybridization will sort out the target conjugates and direct them to the appropriate spots on the surface. In addition, the DNA SAMs are very stable and well suited to recycling by dehybdridization of the conjugates from the surface-bound probes. In this work, we demonstrate the specificity, sensitivity, and convenience of using protein-DNA conjugates to convert a DNA/OEG SAM surface into a biosensor surface and apply this platform to the detection of human chorionic gonadotropin using surface plasmon resonance.     

A fluorescence-based glucose biosensor using concanavalin A and dextran encapsulated in a poly(ethylene glycol) hydrogel.

A fluorescence biosensor is described that is based on a photopolymerized poly(ethylene glycol) (PEG) hydrogel incorporating fluorescein isothiocyanate dextran (FITC-dextran) and tetramethylrhodamine isothiocyanate concanavalin A (TRITC-Con A) chemically conjugated into the hydrogel network using an alpha-acryloyl, omega-N-hydroxysuccinimidyl ester of PEG-propionic acid. In the absence of glucose, TRITC-Con A binds with FITC-dextran, and the FITC fluorescence is quenched through fluorescence resonance energy transfer. Competitive glucose binding to TRITC-Con A liberates FITC-dextran, resulting in increased FITC fluorescence proportional to the glucose concentration. In vitro experiments of hydrogel spheres in a solution of 0.1 M phosphate-buffered saline (pH 7.2) and glucose were conducted for multiple TRITC-Con A/FITC-dextran ratios. Hydrogels were characterized on the basis of the percent change in fluorescence intensity when FITC-dextran was liberated by increasing glucose concentrations. The optimum fluorescent change between 0 and 800 mg/dL was obtained with a TRITC-Con A/FITC-dextran mass ratio of 500:5 micrograms/mL PEG. Fluorescent response was linear up to 600 mg/dL. At higher concentrations, the response saturated due to the displacement of the majority of the FITC-dextran and to concentration quenching by free FITC-dextran. Dynamic fluorescent change upon glucose addition was approximately 10 min for a glucose concentration step change from 0 to 200 mg/dL.     

An acrylate-based quasi-solid polymer electrolyte incorporating a novel dinitrile poly(ethylene glycol) plasticizer for lithium-ion batteries

Journal of Materials Science - The performance of solid polymer electrolytes is characterized by lower ionic conductivity than conventional liquid electrolytes but provides advantages in terms of...     

Synthesis and properties of a novel methoxy poly(ethylene glycol)-modified galactosylated chitosan derivative

Chitosan and its derivatives are attractive non-viral vectors. To produce target-cell specificity and improve the solubility of chitosan, a novel chitosan derivative, modified with galactose and methoxy poly(ethylene glycol) (mPEG) was synthesized, and structure changes of chitosan and its derivatives were characterized. Compared to chitosan, the solution viscosity of the novel chitosan derivative drastically decreased. And, the degree of substitution (DS) of chitosan by galactose and mPEG were calculated as 0.09 and 0.30. The average diameter and zeta potential of mPEGylated galactosylated chitosan (GaC) nanoparticle containing VRMFat plasmid were 178 nm and +2.93 mV, suggesting suitable properties for gene delivery system. The gel electrophoresis confirmed that the plasmid DNA was remained completely by the mPEGylated GaC nanoparticle. And, the cytotoxic effect of mPEGylated GaC nanoparticles on human embryonic kidney (HEK 293) cells was negligible in comparison with that of control chitosans. Therefore, it is expected that the mPEGylated GaC will have the potential as a targeting gene delivery system for a further application. Tao Zhang and Dong Li equally contributed to this research.     

Chemical characterization of diaspirin cross-linked hemoglobin polymerized with poly(ethylene glycol)

A lack of specificity associated with chemical modification methods used in the preparation of certain hemoglobin (Hb)-based oxygen carriers (HBOCs) may alter Hb structure and function, as amino acids located in critical regions (e.g., alpha-beta interfaces and the 2,3-DPG binding pocket) may unintentionally be targeted. Hb protein surface modifications with various poly(ethylene glycol) (PEG) derivatives have been used as conjugating and polymerizing agents with the intent of improving reaction site specificity/reproducibility and ultimately reducing the untoward hypertensive response due to nitric oxide scavenging by smaller molecular size tetrameric species (i.e., 64 kDa) in HBOC solutions. Previous experiments performed in our laboratory have evaluated the influence of polymerization of diaspirin alpha-alpha cross-linked Hb (alphaalpha-DBBF-Hb) with a bifunctional modified PEG, bis(maleoylglycylamide) PEG (BMAA-PEG), in terms of oxygen carrying capacity, redox properties, hypertensive response, and renal clearance in rats. The data presented in this paper specifically evaluate the influence of BMAA-PEG on alphaalpha-DBBF-Hb (Poly-alphaalpha-DBBF-Hb) to identify molecular weight distribution, protein conformation, and site-specific modification, as well as to provide insight into the previously determined in vitro and in vivo functional and vasoactive characteristics of this HBOC. Chemical analysis performed herein reveals nonspecific modifications induced by BMAA-PEG that result in the full modification of alphaalpha-DBBF-Hb leaving no tetrameric cross-linked starting material in solution. These data are inconsistent with the continuing assumption that molecular size (i.e., 64 kDa) has a direct influence on HBOC-mediated vasoactivity and that other protective strategies should be considered to control blood pressure imbalances.