Novel photoinduced grafting-chemical reaction sequence for the construction of a glycosylation surface

Carbohydrates play a major role in many recognition events, such as blood coagulation, immune response, fertilization, cell growth, embryogenesis, and cellular signal transfer, which are essential for the survival of living entities. Synthetic carbohydrate-based polymers, so-called glycopolymers, are emerging as important well-defined tools for investigating carbohydrate-based biological processes and for simulating various functions of carbohydrates. In this work, we present a facile strategy for the formation of glycopolymer tethered on polypropylene microporous membrane surface. Acrylamide was grafted onto the polypropylene microporous membrane surface by photoinduced graft polymerization in the presence of benzophenone. The amide groups of grafted poly(acrylamide) were then transformed to primary amine groups by the Hofmann rearrangement reaction. Quantificational evaluation of the rearrangement reaction was carried out by ninhydrin method and mass weighting. Sugar moieties were coupled with the grafted functional layer to form glycopolymer by the reaction between primary amine groups and carbohydrate lactones. The grafting of acrylamide, the conversion of amide groups to amine groups, and the coupling of sugar moieties were confirmed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy combined with surface morphology observation by scanning electron microscopy.     

Construction of a comb-like glycosylated membrane surface by a combination of UV-induced graft polymerization and surface-initiated ATRP

Carbohydrate residues are found on the extracellular side of the cell membrane. They form a protective coating on the outer surface of the cell and are involved in intercellular recognition. Synthetic carbohydrate-based polymers, so-called glycopolymers, are emerging as important well-defined tools for investigating carbohydrate-based biological processes and for simulating various functions of carbohydrates. In this work, the surface of a polypropylene microporous membrane (PPMM) was modified with comb-like glycopolymer brushes by a combination of UV-induced graft polymerization and surface-initiated atom-transfer radical polymerization (ATRP). 2-Hydroxyethyl methacrylate (HEMA) was first grafted to the PPMM surface under UV irradiation in the presence of benzophenone and ferric chloride. ATRP initiator was then coupled to the hydroxyl groups of poly(HEMA) brushes. Surface-initiated ATRP of a glycomonomer, D-gluconamidoethyl methacrylate, was followed at ambient temperature in aqueous solvent. Water had a significant acceleration effect on the ATRP process; however, loss of control over the polymerization process was also observed. The addition of CuBr2 to the ATRP system largely increased the controllability at the cost of the polymerization rate. The grafting of HEMA, the coupling of ATRP initiator to the hydroxyl groups, and the surface-initiated ATRP were confirmed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy.     

INTERACTION BETWEEN THE SURFACE GLYCOSYLATED POLYPROPYLENE MEMBRANE AND LECTIN

A glycopolymer bearing glucose residues was tethered onto the surface of polypropylene microporous membrane by UV-induced graft polymerization ofα-allyl glucoside.Concanavalin A (Con A),a glucose recognizing lectin,could be specifically adsorbed to the membrane surface.On the other hand,the membrane surface showed no recognition ability to another lectin peanut agglutinin.Moreover,the recognition complex between the glycosylated membrane surface and Con A could be inhibited by glucose and mannose solutio...     

聚丙烯微孔膜表面修饰的葡聚糖固定化研究

糖以各种形式广泛存在于自然界,在人类的许多生理过程中起着不可或缺的重要作用．它具有优良的亲水性和生物特异性．研究表日月,将含糖单体接枝到聚丙烯微孔膜表面或通过共聚引入聚丙烯腈超滤膜,能显著提高常规高分子分离膜的抗污染能力和表面生物相容性,从而扩大其应用范围．     

Recent advances in the preparation of glycopolymer bioconjugates

The significant progress made in understanding the role of carbohydrates and carbohydrates based therapeutics at molecular level has highlighted the importance of carbohydrate bioconjugates in the field of biology, chemistry and therapeutics. The glycosylation of biomolecules is a nature-inspired approach, to impart structural and functional properties to the biomolecules. The availability of facile techniques to synthesize well-defined glycopolymers of varying molecular weights, compositions and shape and their facile conjugation with biomolecules of interest have helped researchers in understanding many aspects of their biological functions at the molecular level. This review focuses on the development of glycopolymer-bioconjugates and provides a comprehensive overview of the present bioconjugation tools for their synthesis. The glycosylation of biomolecules is achieved by either pre or post-polymerization modification approaches. The review highlights the potential of living radical polymerization for the facile synthesis of glycopolymer bioconjugates using both pre and post-polymerization bioconjugation approaches, and without disrupting the native structure and functions of the biological molecules. Non-covalent carbohydrate–carbohydrate and carbohydrate–protein interactions play a significant role in many biological and pathological events. The non-covalent interactions of synthetic glycopolymers with biomolecules are also discussed in this review.     

Fabrication of glycosylated surface on polymer membrane by UV-induced graft polymerization for lectin recognition

Increasingly, carbohydrate-protein interactions are viewed as important mechanisms for many biological processes such as blood coagulation, immune response, viral infection, inflammation, embryogenesis, and cellular signal transfer. However, the weak affinity of the interactions and the structural complexity of carbohydrates have hindered efforts to develop a comprehensive understanding of carbohydrate functions. Fortunately, synthetic polyvalent glycoligands give us a chance to reveal the nature of these biological processes. In this work a sugar-containing monomer (alpha-D-allyl glucoside (AG)) was grafted onto polypropylene microporous membrane (PPMM) by UV-induced graft polymerization to generate a glycosylated porous surface for the first time. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy were employed to confirm the glycosylation. Water contact angle measurement was used to evaluate the hydrophilicity change of the surfaces before and after the graft polymerization of AG. It was found that the grafting density increased reasonably with the increase of AG monomer concentration, and then this increase slowed when the AG concentration exceeded 80 g/L. At the same time a 20-25 min UV irradiation was enough for the grafting polymerization. The photoinitiator concentration also influenced the grafting density obviously, and there was an optimal concentration of the photoinitiator for the grafting process. The water contact angle of the polyAG-tethered membrane surface decreased from 149 degrees to 80 degrees with the increase of grafting density from 0 to 187.76 microg/cm2, which indicated a hydrophilic variation of the membrane surface by the grafting of AG. Results also indicated that the surface-grafted polyAG chains showed weak interaction with Con A when the grafting density was low. However, when the sugar density exceeded 90 microg/cm2, the binding affinity increased dramatically which was the due to the "glycoside cluster effect".     

Buried, covalently attached RGD peptide motifs in poly(methacrylic acid) brush layers: the effect of brush structure on cell adhesion

Iniferter-mediated surface-initiated photopolymerization was used to graft poly(methacrylic acid) (PMAA) brush layers obtained from surface-attached iniferters in self-assembled monolayers to a gold surface. The tethered chains were subsequently functionalized with the cell-adhesive arginine-glycine-aspartic acid (RGD) motif. The modified brushes were extended by reinitiating the polymerization to obtain an additional layer of PMAA, thereby burying the peptide-functionalized segments inside the brush structure. Contact angle measurements and Fourier transform infrared (FTIR) spectroscopy were employed to characterize the wettability and the chemical properties of these platforms. Time of flight secondary ion mass spectroscopy (TOF-SIMS) measurements were performed to monitor the chemical composition of the polymer layer as a function of the distance to the gold surface and obtain information concerning the depth of the RGD motifs inside the brush structure. The brush thickness was evaluated as a function of the polymerization (i.e., UV-irradiation) time with atomic force microscopy (AFM) and ellipsometry. Cell adhesion tests employing human osteoblasts were performed on substrates with the RGD peptides exposed at the surface as well as covered by a PMAA top brush layer. Immunofluorescence studies demonstrated a variation of the cell morphology as a function of the position of the peptide units along the grafted chains.     

Surface modification of polypropylene microfiltration membranes by graft polymerization of N-vinyl-2-pyrrolidone

A hydrophilic polymer, poly(N-vinyl-2-pyrrolidone), was tethered on the surface of polypropylene microfiltration membrane (PPMM) by UV photo-assisted and γ-ray pre-irradiation induced graft polymerizations. Results revealed that the γ-ray pre-irradiation graft polymerization was more efficient in view of the grafting degree. The chemical changes of the membrane surface were confirmed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Pure water contact angle on poly(N-vinyl-2-pyrrolidone)-grafted PPMM decreased with the increase of grafting degree, which indicated an enhanced hydrophilicity for the modified membrane. Both bovine serum albumin adsorption and static platelets adhesion were measured to evaluate the bio-compatibility of the poly(N-vinyl-2-pyrrolidone)-modified PPMM. The statistical amounts of adsorbed bovine serum albumin and adhered platelets on unit membrane area decreased significantly, which to a certain degree demonstrated that the hemocompatibility of PPMM was improved. The N₂ permeability and the mean pore diameters of different PPMMs increased at first, then decreased after certain grafting degree. The changes of water flux followed a similar tendency. These indicated that at low grafting degree pore degradation induced by γ-ray irradiation had a major impact on permeability, while this was overcompensated by the grafted polymer at high grafting degrees.     

Surface glycosylation of polysulfone membrane towards a novel complexing membrane for boron removal

In this study, a novel complexing membrane was synthesized for boron removal from aqueous solution. A glycopolymer, poly(2-gluconamidoethyl methacrylate) (PGAMA), was grafted onto the chloromethylated polysulfone (CMPSF) microporous membrane via surface-initiated ATRP (SIATRP). The glycosylated PSF (GlyPSF) membrane was characterized by attenuated total refection-Flourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), and field emission scanning electron microscopy (FESEM). It was demonstrated that PGAMA was successfully anchored onto the membrane surface and the grafting yield can be tuned in a wide range up to 5.9 mg/cm(2) by varying the polymerization time. The complexing membrane can adsorb boron rapidly with the equilibrium reached within 2h and has a remarkable high boron adsorption capacity higher than 2.0 mmol/g at optimized conditions. Freundlich, Langmuir, and Dubinin-Radushkevich adsorption isotherms were applied, and the data were best described by Langmuir model. Kinetic data were analyzed, and the data fitted very well to the pseudo-second-order rate expression. The optimal pH for boron uptake is in a wide range of 6-9, and the optimal initial boron concentration is over 300 mg/L. Studies of ionic strength effects indicated the formation of inner-sphere surface complexes. The complexed boron can be leached quantitatively under acid condition.     

Glyco-Modification of Protein With O-Cyanate Chain-End Functionalized Glycopolymer via Isourea Bond Formation

Glycoengineering aimed at the addition of carbohydrates to proteins is an attractive approach to alter the pharmacokinetic properties of proteins, such as enhancing stability and prolonging the duration of action. We report a novel protein glyco-modification of BSA and recombinant thrombomodulin with O-cyanate chain-end functionalized glycopolymer via isourea bond formation. The protein glycoconjugates were confirmed by SDS-PAGE, western blot, and MALDI-TOF mass spectrometry. Protein C activation activity of the glyco-modified recombinant thrombomodulin was confirmed, proving no interference with activity from the glycopolymer modification. The isourea bond formation under mild conditions was demonstrated as an alternative method for protein modification with polymers.     

Surface modification of microporous polypropylene membranes by the grafting of poly(γ-stearyl-l-glutamate)

A polypeptide, poly(γ-stearyl-l-glutamate) (PSLG), was grafted on the surface of hydrophobic polypropylene hollow fiber membranes through the ring opening polymerization of N-carboxyanhydride (NCA) of γ-stearyl-l-glutamate initiated by amino groups which was generated by ammonia plasma. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), together with water contact angle and bovium serum albumin adsorption measurements were used to characterize the modified membrane surface. The XPS and FT-IR spectra demonstrated that polypeptide was actually grafted on the membrane surface despite of the low degree of graft polymerization due to the hydroxyl groups on the membrane surface. To subject the ammonia plasma-treated membrane with γ-(aminopropyl)triethanoxysilane (γ-APS) which can react with hydroxyl groups and leave amino groups, the degree of graft polymerization could be improved. The bovium serum albumin adsorption measurement was conducted to further examine the surface properties of modified and original membranes. Potential applications of the PSLG grafted membranes are expected for enantiomer separation and/or enzyme immobilization.     

Surface‐initiated polymerization from poly(ethylene terephthalate)

The free‐radical polymerization of styrene initiated from a functionalized poly(ethylene terephthalate) (PET) surface yielded a tethered polymer layer. The anchoring of the initiator species on the PET surface was performed from surface‐reactive groups easily generated by an alkaline hydrolysis of PET. After each surface modification, PET films were characterized by X‐ray photoelectron spectroscopy, measurements of water contact angles, and time‐of‐flight secondary‐ion mass spectrometry. The influence of the polymerization duration, the grafted initiator density, and the grafting mode on the efficiency of the surface‐initiated polymerization of styrene was investigated. In some cases, the tethering of the polystyrene layer on PET could be a reversible process. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1347–1359, 2003     

甲基丙烯酸2-(N-吖啶酮基)乙酯的合成及其敏化的烯类单体光聚合

我们曾报道过4-甲基丙烯酰氧基二苯甲酮(MABP)与甲基丙烯酸N,N-二甲氨基乙酯(DMAEMA)构成的氧化还原引发体系敏化丙烯腈的光聚合。由于MABP及DMAEMA是可聚合的二芳基酮和脂肪叔胺,因而既能参与引发又能参与聚合而进入聚合物链中。一般二苯甲酮要同三级胺,如三乙胺等一起在紫外光照条件下形成光氧化还原引发体系才能有较好的引发效果。同一分子中既含二苯甲酮基又含三级胺基的光敏剂,     

甲基丙烯酸2-(N-吖啶酮基)乙酯的合成及其敏化的烯类单体光聚合

A novel acrylic monomer having acridonechromophore, 2-(N-acridonono)ethyl methacry-late (AEMA) was prepared from methacryloyl chloride and N-hydroxyethyl acridone (HEA), which was obtained by reaction of acridone with ethylene carbonate. Both the monomer and its polymer can initiate the photopolymerization of vinyl monomers, such as AN, MMA etc, but P(AEMA) has higher initiation ability than monomeric AEMA does. The effects of oxygen and aliphatic tertiary amine on the polymerization rate were also revealed. The UV-analysis indicates that AEMA not only initiates photopolymerization of vinyl monomers,but also enters into the polymer chains.     

Synthesis of membrane adsorbers via surface initiated ATRP of 2-dimethylaminoethyl methacrylate from microporous PVDF membranes

Surface-initiated atom transfer radical polymerization(SI-ATRP) was used to tether poly(2-dimethylaminoethyl methacrylate)(PDMAEMA) onto microporous PVDF membranes in order to synthesize membrane adsorbers for protein adsorption. The alkaline treatment and bromine addition reaction were used to anchor ATRP initiators on membrane surface. Then PDMAEMA was grafted from the membrane surface via SI-ATRP. Fourier transform infrared spectroscopy(FTIR), X-ray photoelectron spectroscopy(XPS) and scanning electron microscopy(SEM) revealed the chemical composition and surface topography of the PVDF-g-PDMAEMA membrane surfaces. These results showed that PDMAEMA was grafted from the membrane surface successfully and a grafting yield as high as 1500 μg/cm2 was achieved. The effects of the grafting time and the density of initiators on the static and dynamic binding capacity of bovine serum albumin(BSA) were systematically investigated. Both the static and dynamic binding capacities increase with the bromination and polymerization time. However, the benefits of the initiator density on binding capacities are limited by the graft density of PDMAEMA chains.     

A novel dot-blot DNAzyme-linked aptamer assay for protein detection

In this work, a novel dot-blot DNAzyme-linked aptamer assay (DLAA) for protein detection is developed with thrombin as a model protein. A peroxidase-like DNAzyme which serves as the catalytic label is tethered to a 15-mer thrombin-binding aptamer to form a label-free DNAzyme-linked aptamer probe. Based on specific interaction of the aptamer with target protein immobilized on nitrocellulose membrane, a DNAzyme layer is introduced onto the membrane. The DNAzyme can catalyze the H₂O₂-mediated oxidation of 3,3′,5,5′-tetramethylbenzidine to produce a colored insoluble product that is apt to be adsorbed onto the nitrocellulose membrane. As a result, blue dots appear on the membrane, in contrast to the colorless background. As the concentration of thrombin increases, the color of dots gets deep. Such a protein concentration-dependent color change can be quantified via an image-processing software, with a detection limit of 0.6 μM. Furthermore, this assay has been applied successfully to the detection of thrombin in biological samples (e.g., human serum), indicating its practicality for bioanalysis.     

Ozone-induced graft polymerization onto polymer surface

Ozone-induced graft polymerization was carried out to improve polymer surfaces. The polymers were exposed to ozone and the surface density of peroxides formed was determined by three methods; iodide, DPPH, and peroxidase method. The peroxide production could be readily controlled by the ozone concentration and the ozone exposure time. In addition, it was dependent on the kind of polymer. Further, it seemed probable that the ozone oxidation introduced peroxides not only on the outermost surface but also into a layer deeper from the outermost surface. Such polymeric peroxides were capable of initiating graft polymerization onto PU. All the physical and biological measurements on the grafted surface indicated that ozone-induced graft polymerization has effectively made the PU surface covered with the grafted water-soluble chains, their location being restricted to the film surface region. The interaction of the PU surface with blood components could be greatly reduced by the surface graft polymerization. © 1993 John Wiley & Sons, Inc.     

Synthesis of glycopolymers via click reactions

This mini-review describes recent work in the field of glycopolymer synthesis, with a focus on methods that have employed “click chemistry” and controlled polymerization methodology. A variety of carbohydrates with clickable groups such as azide, alkyne, and thiol moieties provide new routes to glycopolymers. Several studies use copper catalyzed azide-alkyne cycloaddition (CuAAC) reactions to synthesize glycomonomers or to incorporate carbohydrates into a clickable polymeric backbone. Alternatively, there are many thiol based click reactions which provide metal-free synthesis, which are discussed in details.     

原子转移自由基聚合法制备新型亲水开管毛细管柱及在毛细管电色谱上的应用

为了增加开管毛细管柱(OTCC)的相比,提高分离效率,发展了表面引发原子转移自由基聚合法(SI-ATRP)制备葡萄糖聚合物修饰的开管毛细管柱。通过扫描电镜观察,该开管柱内壁上修饰了三维波浪状聚合物,明显增加了内壁比表面积和相比。在pH 3~11范围内,对含糖聚合物修饰的开管柱和空柱的电渗流进行了比较。修饰后开管柱的电渗流仅为空柱的1/2~1/3,且在pH 6~11范围内保持平稳。稳定的电渗流保证了分离的重复性和稳定性。用该开管毛细管柱成功实现了小分子混合物(苯丙氨酸、胸腺嘧啶、腺苷、鸟苷、5-溴尿嘧啶、水杨酸)以及蛋白质大分子(核糖核酸酶B、转铁蛋白和牛血清白蛋白)的有效分离,结果表明葡萄糖聚合物修饰的开管毛细管柱具有良好的重复性和稳定性。     

TFC polyamide membranes modified by grafting of hydrophilic polymers: an FT-IR/AFM/TEM study

Surface modification using grafting of a hydrophilic polymer onto the membrane surface is a possible route to improving the fouling properties of polyamide thin-film composite membranes. The structure of nanofiltration (NF) and reverse osmosis (RO) membranes modified using graft polymerization of acrylic (AA) monomers was visualized and analyzed using attenuated total reflection–Fourier transform infrared spectroscopy, atomic force microscopy and transmission electron microscopy. The results show that a layer of AA polymer is indeed formed on the polyamide surface, which could be accompanied by a change of the surface morphology. It was observed that for the NF membranes studied polymerization could also take place inside the pores of the support as a result of penetration of the monomer through the active layer, particularly for high degrees of grafting. It suggests that the modification procedures should be optimized so that the latter effect is minimized.