Biofouling-resistance expanded poly(tetrafluoroethylene) membrane with a hydrogel-like layer of surface-immobilized poly(ethylene glycol) methacrylate for human plasma protein repulsions

In general, it is a challenge to control the highly polar material grafting from the chemically inert Teflon-based membrane surface. This work describes the surface modification and characterization of expanded poly(tetrafluoroethylene) (ePTFE) membranes grafted with poly(ethylene glycol) methacrylate (PEGMA) macromonomer via surface-activated plasma treatment and thermally induced graft copolymerization. The chemical composition and microstructure of the surface-modified ePTFE membranes were characterized by Fourier transform infrared spectroscopy (FT-IR), contact angle, and bio-atomic force microscopy (bio-AFM) measurements. Biofouling property of the modified membranes was evaluated by the measurements of the plasma protein (γ-globulin, fibrinogen, or albumin) adsorption determined using an enzyme-linked immunosorbent assay (ELISA). In general, the hydrophilicity of the surface of ePTFE membranes increases with increasing the grafting degree of the copolymerized PEGMA. The highly hydrated PEGMA chain on the resulting ePTFE membranes was found to form a surface hydrogel-like layer with regulated coverage in aqueous state, which can be controlled by the content of PEGMA macromonomer in the reaction solution. The relative protein adsorption was effectively reduced with increasing capacity of the hydration for the PEGMA chain grafted on the ePTFE membrane surface. From both results of protein adsorption and platelet adhesion test in vitro, it is concluded that the PEGMA-grafted hydrophilic ePTFE membranes could provide good biofouling resistance to substantially reduce plasma protein and blood platelet fouling on the membrane surface in human body temperature.     

Functionalization of hydrogen-terminated silicon via surface-initiated atom-transfer radical polymerization and derivatization of the polymer brushes

Surface-initiated atom-transfer radical polymerization (ATRP) of poly(ethylene glycol) monomethacrylate (PEGMA) was carried out on the hydrogen-terminated Si(100) substrates with surface-tethered alpha-bromoester initiator. Kinetic studies confirmed an approximately linear increase in polymer film thickness with reaction time, indicating that chain growth from the surface was a controlled "living" process. The "living" character of the surface-grafted PEGMA chains was further ascertained by the subsequent extension of these graft chains, and thus the graft layer. Well-defined polymer brushes of near 100 nm in thickness were grafted on the Si(100) surface in 8 h under ambient temperature in an aqueous medium. The hydroxyl end groups of the poly(ethylene glycol) (PEG) side chains of the grafted PEGMA polymer were derivatized into various functional groups, including chloride, amine, aldehyde, and carboxylic acid groups. The surface-functionalized silicon substrates were characterized by reflectance FT-IR spectroscopy and X-ray photoelectron spectroscopy (XPS). Covalent attachment and derivatization of the well-defined PEGMA polymer brushes can broaden considerably the functionality of single-crystal silicon surfaces.     

Synthesis and properties of polymer brushes composed of poly(diphenylacetylene) main chain and poly(ethylene glycol) side chains

Novel cylindrical polymer brushes consisting of poly(diphenylacetylene) main chain and poly(poly(ethylene glycol) methyl ether monomethacrylate) (PPEGMA) side chains were synthesized by the diphenylacetylene macromonomer or side chain initiated atom transfer radical polymerization (ATRP) of poly(ethylene glycol) methyl ether monomethacrylate (PEGMA) from an bromo isobutyryl-bearing poly(diphenylacetylene) (poly(BrDPA)) method. The diphenylacetylene macromonomer, namely, DPA-PPEGMA, were prepared by the ATRP of PEGMA from bromo isobutyryl-bearing diphenylacetylene. DPA-PPEGMA was polymerized successfully with WCl₆-Ph₄Sn catalyst to give high molecular weight polymer brushes poly(DPA-PPEGMA). Meanwhile, polymer brushes (PDPA-g-PPEGMA) were obtained by ATRP of PEGMA from poly(BrDPA). The molecular weight of the side chains of PPEGMA could be controlled simply by modulating the ATRP time. The macromonomer and polymer brushes are soluble in nonpolar solvents such as toluene and chloroform. The polymers of poly(BrDPA) and poly(DPA-PPEGMA) absorb in the longer wavelength region, with two peaks at around 370 and 414 nm. The polymers are thermally stable and exhibit double crystallization and melting peaks during the cooling and heating scans.     

Tethering hydrophilic polymer brushes onto PPESK membranes via surface-initiated atom transfer radical polymerization

Surface-initiated atom transfer radical polymerization (ATRP) was used to graft hydrophilic comb-like poly((poly(ethylene glycol) methyl ether methacrylate), or P(PEGMA), brushes from chloromethylated poly(phthalazinone ether sulfone ketone) (CMPPESK) membrane surfaces. Prior to ATRP, chloromethylation of PPESK was beforehand performed and the obtained CMPPESK was prepared into porous membranes by phase inversion process. It was demonstrated that the benzyl chloride groups on the CMPPESK membrane surface afforded effective macroinitiators to graft the well-defined polymer brushes. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) confirmed the grafting of P(PEGMA) chains. Water contact angle measurements indicated that the introduction of P(PEGMA) graft chains promoted remarkably the surface hydrophilicity of PPESK membranes. The effects of P(PEGMA) immobilization on membrane morphology, permeability and fouling resistance were investigated. It was found that the comb-like P(PEGMA) grafts brought smaller pore diameters and higher solute rejections to PPESK membranes. The results of dynamic anti-fouling experiments showed the anti-fouling ability of the membranes was significantly improved after the grafting of P(PEGMA) brushes.     

Atom transfer radical polymerization directly from poly(vinylidene fluoride): Surface and antifouling properties

The direct preparation of grafting polymer brushes from commercial poly (vinylidene fluoride) (PVDF) films with surface‐initiated atom transfer radical polymerization (ATRP) is demonstrated. The direct initiation of the secondary fluorinated site of PVDF facilitated grafting of the hydrophilic monomers from the PVDF surface. Homopolymer brushes of 2‐(N,N‐dimethylamino)ethyl methacrylate (DMAEMA) and poly (ethylene glycol) monomethacrylate (PEGMA) were prepared by ATRP from the PVDF surface. The chemical composition and surface topography of the graft‐functionalized PVDF surfaces were characterized by X‐ray photoelectron spectroscopy, attenuated total reflectance/Fourier transform infrared spectroscopy, and atomic force microscopy. A kinetic study revealed a linear increase in the graft concentration of poly[2‐(N,N‐dimethylamino)ethyl methacrylate] (PDMAEMA) and poly[poly(ethylene glycol) monomethacrylate] (PPEGMA) with the reaction time, indicating that the chain growth from the surface was consistent with a controlled or living process. The living chain ends were used as macroinitiators for the synthesis of diblock copolymer brushes. The water contact angles on PVDF films were reduced by the surface grafting of DMAEMA and PEGMA. Protein adsorption experiments revealed a substantial antifouling property of PPEGMA‐grafted PVDF films and PDMAEMA‐grafted PVDF films in comparison with the pristine PVDF surface. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3434–3443, 2006     

Improving hydrophilicity and protein antifouling of electrospun poly(vinylidenefluoride-hexafluoropropylene) nanofiber membranes

<正>Poly(vinylidenefluoride-hexafluoropropylene)(PVDF-HFP) nanofiber membranes with improved hydrophilicity and protein fouling resistance via surface graft copolymerization of hydrophilic monomers were prepared.The surface modification involves atmospheric pressure glow discharge plasma(APGDP) pretreatment followed by graft copolymerization of poly(ethylene glycol) methyl ether methacrylate(PEGMA).The success of the graft modification with PEGMA on the PVDF-HFP fibrous membrane is ascertained by X-ray photoelectron spectroscopy(XPS) and attenuated total reflectance Fourier transform infrared measurements(ATR-FTIR).The hydrophilic property of the nanofiber membranes is assessed by water contact angle measurements.The results show that the PEGMA grafted PVDF-HFP nanofiber membrane has a water contact angle of 0°compared with the pristine value of 132°.The protein adsorption was effectively reduced after PEGMA grafting on the PVDF-HFP nanofiber membrane surface.The PEGMA polymer grafting density on the PVDF-HFP membrane surface is measured by the gravimetric method,and the filtration performance is characterized by the measurement of water flux.The results indicate that the water flux of the grafted PVDF-HFP fibrous membrane increases significantly with the increase of the PEGMA grafting density.     

SYNTHESIS OF AN AMPHIPHILIC PPESK-g-P(PEGMA) GRAFT COPOLYMER VIA ATRP AND ITS USE IN BLEND MODIFICATION OF PPESK MEMBRANES

Preparation of an amphiphilic graft copolymer having poly(phthalazinone ether sulfone ketone)(PPESK) as main chains was carried out by atom transfer radical polymerization(ATRP).The precursor,chloromethylated PPESK (CMPPESK),was prepared by using chioromethylether as chloromethylation agent.Then,poly(ethylene glycol) methyl ether methacrylate(PEGMA) was used as monomer to synthesize PPESK-g-P(PEGMA) by ATRP method under the catalysis of a cuprous chloride/2,2'-bipyridyl system.PPESK/PPESK-g-P(PEGMA) blen...     

Surface modification of polydimethylsiloxane with photo-grafted poly(ethylene glycol) for micropatterned protein adsorption and cell adhesion

In this study, we applied photo-induced graft polymerization to micropatterned surface modification of polydimethylsiloxane (PDMS) with poly(ethylene glycol). Two types of monomers, polyethylene glycol monoacrylate (PEGMA) and polyethylene glycol diacrylate (PEGDA), were tested for surface modification of PDMS. Changes in the surface hydrophilicity and surface element composition were characterized by contact angle measurement and electron spectroscopy for chemical analysis. The PEGMA-grafted PDMS surfaces gradually lost their hydrophilicity within two weeks. In contrast, the PEGDA-grafted PDMS surface maintained stable hydrophilic characteristics for more than two months. Micropatterned protein adsorption and micropatterned cell adhesion were successfully demonstrated using PEGDA-micropatterned PDMS surfaces, which were prepared by photo-induced graft polymerization using photomasks. The PEGDA-grafted PDMS exhibited useful characteristics for microfluidic devices (e.g. hydrophilicity, low protein adsorption, and low cell attachment). The technique presented in this study will be useful for surface modification of various research tools and devices.     

Micellar polymerization of amphiphilic poly(vinyl alcohol) macromonomer having a methacrylate end group prepared by aldol‐type group‐transfer polymerization

Amphiphilic and heterotactic‐rich poly(vinyl alcohol) (PVA) macromonomer, that is, PVA having a phenyl or phenoxyethyl methacrylate unit as the polymerizable end group, was synthesized via the aldol‐type group‐transfer polymerization (aldol‐GTP) technique. Aldol‐GTPs of vinyloxytriethylsilane (VOTES) were carried out in dichloromethane with 4‐methacryloylbenzaldehyde and 4‐(2‐methacryloylethoxy)benzaldehyde as the initiators with various Lewis acids. The polymerizations proceeded smoothly to give silylated PVA macromonomers (number‐average molecular weights: 1.3 × 10³–1.96 × 10⁴). Poly(VOTES) was easily desilylated to give heterotactic‐rich PVA macromonomer in good yield. The critical micelle concentration of the PVA macromonomer was determined by surface‐tension measurement. Micellar polymerization of the amphiphilic macromonomer gave comb‐shaped (graft) polymer having PVA side chains effectively (conversion: 80–82%), whereas polymerization in dimethyl sulfoxide (homogeneous state) did not. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4477–4484, 2002     

Thermogravimetric analysis of poly(alkyl methacrylates) and poly(methylmethacrylate-g-dimethyl siloxane) graft copolymers

The thermal stabilities of various poly(alkyl methacrylate) homopolymers and poly(methyl methacrylate-g-dimethyl siloxane) (PMMA-g-PSX) graft copolymers have been determined by thermogravimetric analysis (TGA). As expected, the thermal stabilities of poly(alkyl methacrylates) were a function of the ester alkyl group, and polymerization mechanism. In particular, thermally labile linkages, which result from termination during free radical or nonliving polymerization mechanisms, decrease the ultimate thermal stabilities of the polymers. However, graft copolymers, which were prepared by the macromonomer technique with free radical initiators, exhibited enhanced thermal stability compared to homopolymer controls. A more complex free radical polymerization mechanism for the macromonomer modified polymerization may account for this result. © 1994 John Wiley & Sons, Inc.     

NHS-ester functionalized poly(PEGMA) brushes on silicon surface for covalent protein immobilization

Poly(PEGMA) homopolymer brushes were developed by atom transfer radical polymerization (ATRP) on the initiator-modified silicon surface (Si-initiator). Through covalent binding, protein immobilization on the poly(PEGMA) films was enabled by further NHS-ester functionalization of the poly(PEGMA) chain ends. The formation of polymer brushes was confirmed by assessing the surface composition (XPS) and morphology (atomic force microscopy (AFM), scanning electronic microscopy (SEM)) of the modified silicon wafer. The binding performance of the NHS-ester functionalized surfaces with two proteins horseradish peroxidase (HRP) and chicken immunoglobulin (IgG) was monitored by direct observation. These results suggest that this method which incorporates the properties of polymer brush onto the binding surfaces may be a good strategy suitable for covalent protein immobilization.     

Controlled grafting from poly(vinylidene fluoride) films by surface‐initiated reversible addition–fragmentation chain transfer polymerization

A reversible addition–fragmentation chain transfer (RAFT) polymerization technique was applied to graft polymerize brushes of poly(methyl methacrylate) (PMMA) and poly(poly(ethylene glycol) monomethacrylate) (PPEGMA) from poly(vinylidene fluoride) (PVDF) surfaces. PVDF surfaces were exposed to aqueous LiOH, followed by successive reductions with NaBH₄ and DIBAL‐H to obtain hydroxyl functionality. Azo‐functionalities, as surface initiators for grafting, were immobilized on the PVDF surfaces by esterification of 4,4′‐azobis(4‐cyanopentanoic acid) and the surface hydroxyl groups. The chemical composition and surface topography of the graft‐functionalized PVDF surfaces were characterized by X‐ray photoelectron spectroscopy, attenuated total reflectance‐FTIR spectroscopy, and atomic force microscopy. Kinetics studies revealed a linear increase in the graft concentration of PMMA and PPEGMA with the reaction time, indicating that the chain growth from the surface was consistent with a “controlled” or “living” process. The living chain ends were used as the macroinitiator for the synthesis of diblock copolymer brushes. Water contact angles on PVDF films were reduced by surface grafting of PEGMA and MMA. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3071–3082, 2006     

温度/pH敏感性接枝共聚物水凝胶P(DMAEMA-g-NIPAM)的 合成及性质研究

利用大分子单体技术, 采用自由基溶液聚合合成了温度/pH敏感性聚甲基丙烯酸-N,N-二甲氨基乙酯接枝聚N-异丙基丙烯酰胺[P(DMAEMA-g-NIPAM)]水凝胶. 用红外光谱及扫描电镜对凝胶的组成及形貌进行了表征. 凝胶的去溶胀和溶胀动力学研究表明, 所合成的凝胶具有温度和pH敏感性. 与传统的聚丙烯酸系水凝胶相比, P(DMAEMA-g- NIPAM)具有相反的pH敏感性; P(DMAEMA-g-NIPAM)凝胶在55 ℃时具有较快的去溶胀速率, 随着凝胶中接枝链PNIPAM量的增加, 凝胶的去溶胀速率加快.     

Preparation of P4VP-g-PSt Copolymer Microspheres with Controllable Size by Atom Transfer Radical Polymerization Synthesized Poly(4-vinylpyridine) Macromonomer

Poly(4‐vinylpyridine) macromonomer (St‐P4VP) with a styryl end group was synthesized by atom transfer radical polymerization (ATRP) of 4‐vinylpyridine using p‐(chloromethyl)styrene (CMSt) as functional initiator, CuCl as catalyst and tris[2‐(dimethylamino)ethyl]amine (Me₆TREN) as ligand in 2‐propanol. The structure of St‐P4VP macromonomer was identified by proton nuclear magnetic resonance (¹H NMR). The result of gel permeation chromatography (GPC) illustrated that the number‐average molecular weight of St‐P4VP could be controlled by adjusting polymerization conditions. Poly(4‐vinylpyridine) grafted polystyrene microspheres (P4VP‐g‐PSt) were then prepared by dispersion copolymerization of styrene with St‐P4VP macromonomers. The effects of polymerization reaction parameters such as medium polarity, concentration of St‐P4VP macromonomer and polymerization temperature on the sizes and size distribution of P4VP‐g‐PSt microspheres were investigated. The results of transmission electron microscopy (TEM), scanning electron microscopy (SEM) and laser light scattering (LLS) indicated that mono‐dispersed P4VP‐g‐PSt microspheres with average diameters of 100–200 nm could be obtained when the molar ratio of St to St‐P4VP was 0.25:100 in ethanol/water mixed solvents (V/V=80:20) at 60°C. Such kind of graft copolymer microspheres was expected to be applied to many fields such as drug delivery system and protein adsorption/separation system due to their particular structure.     

Graft copolymers having hydrophobic backbone and hydrophilic branches. XI. Preparation and thermosensitive properties of polystyrene microspheres having poly (N-isopropylacrylamide) branches on their surfaces

Thermosensitive microspheres with 0.4–1.2 μm diameter consisting of a polystyrene core and poly(N-isopropylacrylamide) (polyNIPAAm) branches on their surfaces were prepared by the free radical polymerization of a polyNIPAAm macromonomer and styrene in ethanol. Electron spectroscopy for chemical analysis (ESCA) of the microsphere surface suggested that polyNIPAAm chains were favorably located on the surface of the microspheres. The morphology of the microspheres was observed by transmission electron micrograph (TEM) and the particle size of was estimated by submicron particle analyzer. The molecular weight of the polyNIPAAm macromonomer, the ratio of the macromonomer and styrene, and the polymerization temperature affected the particle size. Thermosensitive properties of polyNIPAAm-coated polystyrene microspheres were evaluated by the turbidity of their dispersion solutions and the hydrodynamic size of the miocrospheres. The transmittance in dispersion solutions changed clearly, similar to oligoNIPAAm and polyNIPAAm macromonomers. In addition, the particle size of microspheres decreased with rising temperature. These results were explained by the thermosensitivity of polyNIPAAm branches on the microsphere surface. © 1996 John Wiley & Sons, Inc.     

Surface‐initiated atom transfer radical polymerization from porous poly(tetrafluoroethylene) membranes using the C?F groups as initiators

This work reports the surface‐initiated atom transfer radical polymerization (ATRP) from hydrogen plasma‐treated porous poly(tetrafluoroethylene) (PTFE) membranes using the C? F groups as initiators. Hydrogen plasma treatment on PTFE membrane surfaces changes their chemical environment through defluorination and hydrogenation reactions. With the hydrogen plasma treatment, the C? F groups of the modified PTFE membrane surface become effective initiators of ATRP. Surface‐initiated ATRP of poly(ethylene glycol) methacrylate (PEGMA) is carried out to graft PPEGMA chains to PTFE membrane surfaces. The chain lengths of poly(PEGMA) (PPEGMA) grafted on PTFE surfaces increase with increasing the reaction time of ATRP. Furthermore, the chain ends of PPEGMA grown on PTFE membrane surfaces then serve as macroinitiators for the ATRP of N‐isopropylacrylamide (NIPAAm) to build up the PPEGMA‐b‐PNIPAAm block copolymer chains on the PTFE membrane surfaces. The chemical structures of the modified PTFE membranes are characterized using X‐ray photoelectron spectroscopy. The modification increases the surface hydrophilicity of the PTFE membranes with reductions in their water‐contact angles from 120° to 60°. The modified PTFE membranes also show temperature‐responsive properties and protein repulsion features owing to the presence of PNIPAAM and PPEGMA chains. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2076–2083, 2010     

Synthesis and characterization of a poly(GMA)‐graft‐poly(Z‐L‐lysine) graft copolymer with a rod‐like structure

This study applied the macromonomers and glycidyl methacrylate (GMA) to synthesize a series of the graft copolymers, poly(GMA)‐graft‐poly(Z‐L ‐lysine), and investigated the conformation of the graft copolymer. The graft copolymers were synthesized with different GMA monomer ratios (28 to 89%) and different degrees of polymerization (DP) (8 to 15) of the poly(Z‐L ‐lysine) side chain to analyze secondary structure relationships. Atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), and both wide angle and small angle X‐ray scattering spectroscopy (WAXS, SAXS) were used to investigate the relationship between the microstructure and conformation of the graft copolymers and the different monomer ratios and side chain DP. In AFM images, n8‐G89 (the graft copolymer containing 89% GMA units and the macromonomer DP is 8) showed tiny and uniform rod‐like structures, and n14‐G43 (the graft copolymer containing 43% GMA units and the macromonomer DP is 14) showed uniform rod‐like structures. FTIR spectra of the graft copolymers showed that the variations of α‐helix and β‐sheet secondary structures in the graft copolymers relate to the monomer ratios of the graft copolymers. However, the X‐ray scattering patterns indicated that the graft copolymer conformations were mainly dependent on the poly(Z‐L ‐lysine) side chain length, and these results were completely in accordance with the AFM images. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4655–4669, 2009     

Micelle formation and sol–gel transition behavior of comb‐like amphiphilic poly((PLGA‐b‐PEG)MA) copolymers

Comb‐like amphiphilic poly(poly((lactic acid‐co‐glycolic acid)‐block‐poly(ethylene glycol)) methacrylate (poly((PLGA‐b‐PEG)MA)) copolymers were synthesized by radical polymerization. (PLGA‐b‐PEG)MA macromonomer was prepared by ring‐opening bulk polymerization of DL ‐lactide and glycolide using purified poly(ethylene glycol) monomethacrylate (PEGMA) as an initiator. (PLGA‐b‐PEG)MA macromonomer was copolymerized with PEGMA and/or acrylic acid (AA) by radical polymerization to produce comb‐like amphiphilic block copolymers. The molecular weight and chemical structure were investigated by GPC and ¹H NMR. Poly((PLGA‐b‐PEG)MA) copolymer aqueous solutions showed gel–sol transition behavior with increasing temperature, and gel‐to‐sol transition temperature decreased as the compositions of the hydrophilic PEGMA and AA increased. The gel‐to‐sol transition temperature of the terpolymers of the poly((PLGA‐b‐PEG)MA‐co‐PEGMA‐co‐AA) also decreased when the pH was increased. The effective micelle diameter obtained from dynamic light scattering increased with increasing temperature and with increasing pH. The critical micelle concentration increased as the composition of the hydrophilic monomer component, PEGMA and AA, were increased. The spherical shape of the hyperbranched polymers in aqueous environment was observed by atomic force microscopy. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1954–1963, 2008     

Enhancing hydrophilicity and protein resistance of silicone hydrogels by plasma induced grafting with hydrophilic polymers

<正>The hydrophilicity of silicone hydrogels used as soft corneal contact lens plays an important role in wearing comfort.In order to enhance hydrophilicity and protein resistance,silicone hydrogel membranes were modified by atmospheric pressure glow discharge plasma(APGDP) induced surface graft polymerization of N-vinyl pyrrolidone(NVP) and poly(oligoethylene glycol methyl ether methacrylate)(PEGMA) in this paper.XPS analysis demonstrated the success of graft polymerization of NVP and PEGMA onto the surface of silicone hydrogel membranes.The hydrophilicity of silicone hydrogels was characterized by the measurement of water contact angle(WCA).The result showed that NVP grafted silicone hydrogel has the WCA of about 68°and PEGMA grafted silicone hydrogel has the lowest WCA of about 62°,while the pristine silicone hydrogel is hydrophobic with the WCA of about 103°.Protein resistance of silicone hydrogels was investigated by the method of bicinchoninic acid assay using bovine serum albumin(BSA) as a model.It's found that the grafted silicone hydrogel has a significant improvement of protein resistance,and PEGMA grafting is more efficient for the reduction of protein adsorption than NVP grafting.The silicone hydrogel membranes grafted with NVP and PEGMA are good candidates of soft corneal contact lenses.     

Atmospheric pressure plasma induced grafting of poly(ethylene glycol) onto silicone elastomers for controlling biological response

This study investigates the role that surface functionalisation of silicone elastomer (SE) by atmospheric pressure plasma induced graft immobilisation of poly(ethylene glycol) methyl ether methacrylate (PEGMA) plays in the attendant biological response. SE is used in modern ophthalmic medical devices and samples of the material were initially plasma treated using a dielectric barrier discharge reactor (DBD) to introduce reactive oxygen functionalities, prior to in situ grafting of two molecular weights of PEGMA (MW 1000 Da: PEGMA(1000), MW 2000 Da: PEGMA(2000)). The variously processed surfaces were characterised by water contact angle analysis, X-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectrometry and atomic force microscopy. Lens epithelial cells were then cultured on the PEGMA grafted SE surfaces. It was found that cells on the pristine surface were not well spread and had shrunken morphology. On the DBD pre-treated surfaces, the cells were well spread. On the PEGMA(1000) surface, the cells displayed evidence of shrinkage and were on the verge of detaching. Remarkably, on the PEGMA(2000) surface, no cell adhesion was detection. Bacterial adhesion to the surfaces was studied using Staphylococcus aureus NTC8325. There was no difference in the number of bacteria adhering to any of the surfaces studied.