Chitosan-tethered poly(acrylonitrile-co-maleic acid) hollow fiber membrane for lipase immobilization

A protocol was used to prepare a dual-layer biomimetic membrane as support for enzyme immobilization by tethering chitosan on the surface of poly(acrylonitrile-co-maleic acid) (PANCMA) ultrafiltration hollow fiber membrane in the presence of 1-ethyl-3-(dimethylaminopropyl) carbodiimide hydrochloride (EDC)/N-hydroxylsuccin-imide (NHS). The chemical change of the chitosan-modified PANCMA membrane surface was confirmed with Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Lipase from Candida rugosa was immobilized on this dual-layer biomimetic membrane using glutaraldehyde (GA), and on the nascent PANCMA membrane using EDC/NHS as coupling agent. The properties of the immobilized enzymes were assayed and compared with those of the free one. It was found that both the activity retention of the immobilized lipase and the amount of bound protein on the dual-layer biomimetic membrane (44.5% and 66.5 mg/m2) were higher than those on the nascent PANCMA membrane (33.9% and 53.7 mg/m2). The kinetic parameters of the free and immobilized lipases, Km and Vmax, were also assayed. The Km values were similar for the immobilized lipases, while the Vmax value of the immobilized lipase on the dual-layer biomimetic membrane was higher than that on the nascent PANCMA membrane. Results indicated that the pH and thermal stabilities of lipase increased upon immobilization. The residual activity of the immobilized lipase after 10 uses was 53% on the dual-layer biomimetic membrane and 62% on the nascent PANCMA membrane.     

Hydrophilic, semipermeable membranes fabricated with poly(ethylene oxide)-polysulfone block copolymer

Semipermeable membranes may be fabricated from mixtures of poly(ethylene oxide)/polysulfone block copolymer (PEO-b-PSF) and polysulfone. Membranes fabricated with PEO-b-PSF possess a hydrophilic surface. PEO-b-PSF segregates to the membrane surface during phase inversion fabrication of the membrane rendering the surface hydrophilic. Changes in surface hydrophilicity were demonstrated by a dramatic reduction in the dynamic contact angle in water. With regard to the similar microporous hollow fiber membranes, a PEO-b-PSF membrane had a dynamic water contact angle of 33 degrees +/- 2 compared to a 111 degrees +/- 3 for a polysulfone membrane. Studies on porcine platelet-rich plasma in vitro demonstrated that the hydrophilic PEO-b-PSF membrane was resistant to platelet adhesion compared to a polysulfone membrane. An order of magnitude fewer adherent platelets were observed on a PEO-b-PSF membrane compared to a polysulfone membrane. The hydrophilicity of PEO-b-PSF makes it a unique material for the fabrication of membranes for medical devices.     

Biocompatibility of modified polyethersulfone membranes by blending an amphiphilic triblock co-polymer of poly(vinyl pyrrolidone)-b-poly(methyl methacrylate)-b-poly(vinyl pyrrolidone)

An amphiphilic triblock co-polymer of poly(vinyl pyrrolidone)-b-poly(methyl methacrylate)-b-poly(vinyl pyrrolidone) (PVP-b-PMMA-b-PVP) was synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. The block co-polymer can be directly blended with polyethersulfone (PES) using dimethylacetamide (DMAC) as the solvent to prepare flat sheet and hollow fiber membranes using a liquid-liquid phase separation technique. The PVP block formed a brush on the surface of the blended membrane, while the PMMA block mingled with the PES macromolecules, which endowed the membrane with permanent hydrophilicity. After adding the as-prepared block co-polymer the modified membranes showed lower protein (bovine serum albumin) adsorption, suppressed platelet adhesion, and a prolonged blood coagulation time, and thereby the blood compatibility was improved. Furthermore, the modified PES membranes showed good cytocompatibility, ultrafiltration and protein anti-fouling properties. These results suggest that surface modification of PES membranes by blending with the amphiphilic triblock co-polymer PVP-b-PMMA-b-PVP allows practical application of these membranes with good biocompatibility in the field of blood purification, such as hemodialysis and bioartificial liver support.     

Surface characteristics and biocompatibility of lactide-based poly(ethylene glycol) scaffolds for tissue engineering

Novel lactide-based poly(ethylene glycol) (PEG) polymer networks (GL9-PEGs) were prepared by UV copolymerization of a glycerol-lactide triacrylate (GL9-Ac) with PEG monoacrylate (PEG-Ac) to use as scaffolds in tissue engineering, and the surface properties and biocompatibility of these networks were investigated as a function of PEG molecular weight and content. Analysis by ATR-FTIR and ESCA reveled that PEG was incorporated well within the GL9-PEG polymer networks and was enriched at the surfaces. From the results of SEM, AFM, and contact angle analyses, GL9-PEG networks showed relatively rough and irregular surfaces compared to GL9 network, but the mobile PEG chains coupled at their termini were readily exposed toward the aqueous environment when contacting water such that the surfaces became smoother and more hydrophilic. This reorientation and increase in hydrophilicity were more extensive with increasing PEG molecular weight and content. As compared to GL9 network lacking PEG, protein adsorption as well as platelet and S. epidermidis adhesion to GL9-PEG networks were significantly reduced as the molecular weight and content of PEG was increased, indicating that GL9-PEG networks are more biocompatible than the GL9 network due to PEG's passivity. Based on the physical and biological characterization reported, the GL9-PEG materials would appear to be interesting candidates as matrices for tissue engineering.     

Biocompatibility of poly(epsilon-caprolactone)/poly(ethylene glycol) diblock copolymers with nanophase separation

In this study, we prepared diblock copolymers of poly(epsilon-caprolactone) (PCL) and poly(ethylene glycol) (PEG) by aluminum alkoxide catalysts. The biological responses to the spin cast surface of different PCL/PEG diblock copolymers were investigated in vitro. Our results showed that surface hydrophilicity improved with the increased PEG segments in diblock copolymers and that bacteria adhesion was inhibited by increased PEG contents. PCL-PEG 23:77 showed nanotopography on the surface. The number of adhered endothelial cells, platelets and monocytes on diblock copolymer surfaces was inhibited in PCL-PEG 77:23 and enhanced in PCL-PEG 23:77. Nevertheless, the platelet and monocyte activation on PCL-PEG 23:77 was reduced. PCL-PEG 23:77 had better cellular response as well as lower degree of platelet and monocyte activation. The current study was the first one to demonstrate that surface nanotopography could influence not only cell adhesion and growth but also platelet and monocyte activation.     

Biodegradable block poly(ester-urethane)s based on poly(3-hydroxybutyrate-co-4-hydroxybutyrate) copolymers

A series of block poly(ester-urethane)s (abbreviated as PU3/4HB) based on biodegradable poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3/4HB) segments were synthesized by a facile way of melting polymerization using 1,6-hexamethylene diisocyanate (HDI) as the coupling agent and stannous octanoate (Sn(Oct)(2)) as catalyst, with different 4HB contents and segment lengths. The chemical structure, molecular weight and distribution were systematically characterized by (1)H nuclear magnetic resonance spectrum (NMR), Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC). The thermal property was studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The hydrophilicity was investigated by static contact angle of deionized water and CH(2)I(2). DSC curves revealed that the PU3/4HB polyurethanes have their T(g) from -25.6?°C to -4.3?°C, and crystallinity from 2.5% to 25.3%, being almost amorphous to semi-crystalline. The obtained PU3/4HBs are hydrophobic (water contact angle 77.4°-95.9°), and their surface free energy (SFE) were studied. The morphology of platelets adhered on the polyurethane film observed by scanning electron microscope (SEM) showed that platelets were activated on the PU3/4HB films which would lead to blood coagulation. The lactate dehydrogenase (LDH) assay revealed that the PU3/4HBs displayed higher platelet adhesion property than raw materials and biodegradable polymer polylactic acid (PLA) and would be potential hemostatic materials. Crystallinity degree, hydrophobicity, surface free energy and urethane linkage content play important roles in affecting the LDH activity and hence the platelet adhesion. CCK-8 assay showed that the PU3/4HB is non-toxic and well for cell growth and proliferation of mouse fibroblast L929. It showed that the hydrophobicity is an important factor for cell growth while 3HB content of the PU3/4HB is important for the cell proliferation. Through changing the composition and the chain-length of P3/4HB-diol prepolymers, the biocompatibility of the poly(ester-urethane)s can be tailored.     

Improved blood compatibility of poly(ethylene terephthalate) films modified with L-arginine

In order to improve the blood compatibility of the commonly used blood-contacting biomaterial poly(ethylene terephthalate) (PET), in this study PET films were chemically modified with L-arginine (L-Arg) by a three-step-procedure using glutaraldehyde (GA) as a cross-linker. The composition and chemical structure of PET and its change with surface modification were examined by X-ray photoelectron spectroscopy (XPS) and attenuated total reflection Fourier transform infrared (ATR-FT-IR) spectroscopy, while the change in hydrophilicity was judged by water contact angles measurement. The result of water contact measurement indicated that the modified films became more hydrophilic than PET with the contact angle decreasing from 78.5 degrees for PET to 43.7 degrees for PET-Arg. The protein adsorption on the film surface was evaluated by bicinchoninic acid assay (BCA) method, and the result showed that the L-Arg-modified films decreased the amount of protein adsorption by about 25%. The in vitro blood compatibility such as platelet adhesion (observed by scanning electron microscopy) and thrombus formation was also investigated, and the results demonstrated that the L-Arg-modified films significantly suppressed platelet adhesion and aggregation and reduced the thrombus formation by about 67% compared with PET.     

Fabrication and characterization of hydrophilic electrospun membranes made from the block copolymer of poly(ethylene glycol-co-lactide)

To improve the hydrophilicity, pliability, and egradability of some biodegradable polymers such as polylactide (PLA), a triblock copolymer, and poly(ethylene glycol-co-lactide) (PELA) has been electrospun into fibrous membranes in the fiber sizes of 7.5 microm to 250 nm. The relationship between electrospinning parameters (such as voltage, concentration, and feeding rate) and the fiber diameters has been investigated. The characterizations for the structure and morphology of electrospun membranes were carried out using differential scanning calorimetry (DSC), (1)H NMR, and scanning electron microscopy (SEM). The hydrophilicity of the membrane was determined by contact angle measurements in bi-distilled water, and it was shown that the hydrophilicity of the copolymer could be adjusted by the content of the poly (ethylene glycol) (PEG) segment in the copolymer. The results of in vitro degradation study showed that the submicrostructure of the fibrous membrane and the incorporation of hydrophilic PEG into PLA block could accelerate the degradation of the membrane in regards to the changes of inherent viscosity, tensile strength, and weight loss.     

聚乙二醇在聚砜膜上的接枝与表征

对用紫外辐照法在聚砜膜表面接枝的聚乙二醇作了初步的研究。通过静态水接触角测定、X射线-光电子能谱分析以及原子力学显微镜等测试手段，对接枝前后聚砜膜表面的性能进行了测定，证明采用同步接枝法和二步接枝法在聚砜材料表面接上了聚乙二醇，表面亲水性大大提高，两种接枝方法的接枝覆盖率分别为77．3％和41．9％，表面形貌、相位图等参数较接枝前变化明显，说明用同步法在聚砜膜表面产生了分枝的聚乙二醇层，而二步法在聚砜膜表面产生了薄煎饼状的聚乙二醇层。这一研究为下一步拟在聚砜中空纤维膜表面接上聚乙二醇刷分子层打下了基础。     

Immobilization of poly(ethylene glycol) or its sulfonate onto polymer surfaces by ozone oxidation.

A novel surface modification method has been developed to improve biocompatibility of polymeric biomaterials. This approach involves ozonation and then followed by graft polymerization with acrylates containing PEG, sulfonated PEG or by coupling of PEG derivatives. All the reactions were confirmed by ATR FT-IR and ESCA. The degree of ozonation measured by the iodide method was dependent on the ozone permeability of the polymers used. Surface hydrophilicity was investigated by measuring the contact angles. Ozonation itself yielded a slight increase in hydrophilicity and a decrease in platelet adhesion, but PEG immobilization showed a significant effect on surface hydrophilicity and platelet adhesion to confirm well-known PEG's passivity which minimize the adhesion of blood components on polymer surfaces. Both graft polymerization and coupling were effective for PU. In contrast, only grafting gave enough yields for PMMA and silicone. Platelet adhesion results demonstrated that all PEG modified surfaces adsorbed lower platelet adhesion than untreated or ozonated ones. Polymers coupled with sulfonated PEG exhibited the lowest platelet adhesion when compared with control and PEG coupled ones by virtue of the synergistic effect of non-adhesive PEG and negatively charged SO3 groups. This PEG or sulfonated PEG immobilization technology using ozonation is relatively simple for introducing uniform surface modification and therefore very useful for practical application of blood contacting medical devices.     

Adsorption of albumin,collagen, and fibronectin on the surface of poly(hydroxybutyrate-hydroxyvalerate) (PHB/HV) and of poly(ε-caprolactone) (PCL) films modified by an alkaline hydrolysis and of poly(ethylene terephtalate) (PET) track-etched membranes

The effect of alkaline hydrolysis on several surface properties of poly(hydroxybutyratehydroxyvalerate) (92/8) (PHB/HV) and poly(ε-caprolactone) (PCL) films and of poly(ethylene terephtalate) (PET) track-etched membranes have been characterized, as well as the adsorption of three proteins normally encountered by mammalian cells in vivo, namely albumin, collagen, and fibronectin. The water contact angle decreases and the number of -COOH functions accessible to a chemical reaction at the surface of PCL increases with alkaline hydrolysis. Analysis by atomic force microscopy pictures reveals a change in surface morphology. The modifications of surface properties are correlated with a two times increase of the adsorption of three radiolabelled proteins. The hydrolysis results in a slight increase in the water contact angle of one face of the PHB/HV film and a sharp increase in the number of -COOH functions. Important morphology changes are also induced. The adsorption of the radiolabelled proteins is almost 100 times higher on the hydrolyzed polymer than on the native surface. The increase in hydrophilicity of different PET batches correlates to an increase in the number of -COOH functions. Nevertheless, the surface chemical composition and rugosity are constant and no significant difference in the amount of radiolabelled fibronectin adsorbed on the different surfaces is detectable. In conclusion, the effect of hydrolysis on the surface properties of each of the polyesters studied as well as the proteins adsorption on the different surfaces are different. The results strongly support the hypothesis that, in the system studied, parameters other than hydrophilicity influence protein adsorp     

Modification of HTPB-based polyurethane with temperature-sensitive poly(N-isopropyl acrylamide) for biomaterial usage

Hydroxyl-terminated polybutadiene (HTPB)-based polyurethane with dimethyol propionic acid (DPA) as chain extender was synthesized by solution polymerization. The HTPB-based polyurethane was modified by UV radiation with N-isopropyl acrylamide monomer to get poly(N-isopropyl acrylamide)-modified polyurethane (PUDPANIPAAm). The cohesive energy (E(coh)), molar volume (V), solubility parameter (delta), molecular weight (W(M)), volume per gram (V(g)), and the density (1/V(g)) of PUDPANIPAAm were calculated by group contribution methods. To evaluate the application of PUDPANIPAAm for wound dressing and transplantation of cell sheet, the measurement of water content, water vapor transmission rate, and gas permeation on the PUDPANIPAAm membrane was evaluated. The biocompatibility of these membranes, cell adhesion, and proliferation assay were conducted in the cell culture. The effect of thermosensitivity of poly(N-isopropyl acrylamide) on cell detachment was also evaluated in the primary study. The results showed that these PUDPANIPAAm membranes are thermosensitive. The modification of PU with poly(N-isopropyl acrylamide) reduced the water vapor transmission rate and permeability of gas through PUDPANIPAAm membrane. PUDPANIPAAm membranes could support cell adhesion and growth. Owing to the thermosensitive nature of poly(N-isopropyl acrylamide), the relative cell numbers detached from PUDPANIPAAm membranes were larger than those detached from the polystyrene dish.     

Interactions of poly(ethylene glycol)-grafted cellulose membranes with proteins and platelets.

The interactions of proteins and platelets with cellulose membranes grafted with poly(ethylene glycol) were studied. The poly(ethylene glycol) grafting was carried out using poly(ethylene glycol)-monoacid and poly(ethylene glycol)-diacid, which have one and two terminal carboxyl groups, respectively. The grafting operates through esterification between the carboxyl groups of poly(ethylene glycol) and the hydroxyl groups on the membrane surface. Both of the poly(ethylene glycol) grafted membranes reduced the complement activation. Adsorption of bovine serum albumin and gamma-globulin increased when the membrane was grafted with poly(ethylene glycol)-diacid, but did not change when it was grafted with poly(ethylene glycol)-monoacid. When platelets were incubated with serum proteins, the platelet adhesion to the membranes slightly decreased by grafting both the poly(ethylene glycol)-diacid and poly(ethylene glycol)-monoacid. The poly(ethylene glycol)-diacid grafted surface showed more clotting than the poly(ethylene glycol)-monoacid grafted and original surfaces.     

Polysulfone-graft-poly(ethylene glycol) graft copolymers for surface modification of polysulfone membranes

Amphiphilic graft copolymers having polysulfone (PSf) backbones and poly(ethylene glycol) (PEG) side chains were synthesized via reaction of an alkoxide formed from PEG and a base (sodium hydride) with chloromethylated polysulfone. The resulting polysulfone-graft-poly(ethylene glycol), PSf-g-PEG, materials were hydrophilic but water insoluble, rendering them potentially useful as biomaterial coatings. PSf-g-PEG films exhibited high resistance to protein adsorption and cell attachment. When used as an additive in PSf membranes prepared by immersion precipitation, the graft copolymer preferentially segregates to the membrane surface, delivering enhanced wettability, porosity and protein resistance compared to unmodified PSf membranes. The surface properties of PSf-g-PEG modified membranes render them desirable candidates for hemodialysis.     

Surface modification of poly(tetrafluoroethylene) films via grafting of poly(ethylene glycol) for reduction in protein adsorption

Poly(tetrafluoroethylene) (PTFE) films with surface grafted poly(ethylene glycol) (PEG) chains were prepared by two methods: (1) UV-induced graft copolymerization of methoxy poly(ethylene glycol) monomethacrylate (PEGMA) onto the plasma-pretreated PTFE films; and (2) coupling of the hydroxyl groups of PEG via ester linkages with the carbonyl chloride groups which were introduced onto the acrylic acid (AAc) graft-copolymerized PTFE surface through reaction with thionyl chloride (SOCl₂). The UV-induced graft copolymerization of PEGMA onto the plasma-pretreated PTFE film was explored with different macromonomer concentrations and different UV graft copolymerization time. The coupling reaction, on the other hand, was explored with PEG of different molecular weights. The surface microstructures and compositions of the PEGmodified PTFE films from both processes 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 for the UV-induced graft copolymerization with PEGMA. Contact angle measurements revealed that the hydrophilicity of the PTFE film surface was greatly enhanced by the grafting of the PEG chains. The PTFE surface with a high density of grafted PEG was very effective in preventing bovine serum albumin adsorption.     

Hydrogels based on poly(ethylene oxide) and poly(tetramethylene oxide) or poly(dimethyl siloxane): synthesis, characterization, in vitro protein adsorption and platelet adhesion

In vitro protein adsorption, platelet adhesion and activation on new hydrogel surfaces, composed of poly(ethylene oxide) (PEO) and poly(tetramethylene oxide) (PTMO) or poly(dimethyl siloxane) (PDMS), were investigated. By varying PEO length (MW = 2000 or 3400), hydrophobic components (PTMO or PDMS) or polymer topology (block or graft copolymers), various physical hydrogels were produced. Their structures were verified by 1H NMR and ATR-IR and the molecular weights were determined by gel permeation chromatography. The hydrogels were soluble in a variety of organic solvents, while absorbed a significant amount of water with preserved three-dimensional structure by physical crosslinking. The dynamic contact angle measurement revealed that the surface hydrophilicity increased by incorporating longer PEO, PEO grafting, and adopting PDMS as a hydrophobic segment instead of PTMO. It was observed from in vitro protein adsorption study that the hydrogels exhibited significantly lower adsorption of human serum albumin (HSA), human fibrinogen (HFg), and IgG, when compared with Pellethane, a commercial polyurethane taken as a control. The hydrogels were attractive for HSA but not sensitive to HFg and IgG. And more than 65% of the proteins detected on the surfaces of the hydrogels were reversibly detached by being treated with an SDS solution. It was evident that the hydrogels synthesized in this study were much more resistant to platelet adhesion than the control, which might depend on the composition of proteins adsorbed on the surfaces and their degree of denaturation. Among the hydrogels tested, PEO3,4kPDMS exhibited albumin-rich and platelet-resistant surfaces, implying a potential candidate for biomaterial.     

Cellular responses to electrospun membranes made from blends of PLLGA with PEG and PLLGA-b-PEG

Control of cellular responses is crucial for the use of electrospun membranes in biomedical applications, including tissue engineering or biomedical devices. However, it is still unclear whether adhesion and proliferation of fibroblasts is stimulated or inhibited on polyethylene glycol (PEG)-modified electrospun membranes. In this study, poly(L-lactide-co-glycolide) (PLLGA)-PEG copolymer and pure PEG were blended with PLLGA, and then electrospun onto nonwoven membranes. The effects of blending of PLLGA-PEG or pure PEG on the adsorption of proteins, and further on the adhesion and proliferation of L929 fibroblasts on the electrospun membranes were investigated. Addition of PLLGA-PEG or PEG significantly improved the hydrophilicity of the electrospun membranes. Pure PEG had no obvious effects on the growth of L929 fibroblasts; in contrast, PLLGA-PEG significantly inhibited the adsorption of proteins and the proliferations of the cells on the electrospun membranes. In response to diminished protein adsorption, mRNA expression of genes related to cell adhesion and migration was up-regulated. The limited effects of pure PEG were probably caused by its preferential dissolution, whereas membrane-confined PLLGA-PEG displayed excellent performance on the inhibition of protein adsorption and cell proliferation. ? 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 100A:2897-2904, 2012.     

Surface glycosylation of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) membrane for selective adsorption of low-density lipoprotein

A novel method of constructing a glycosylated surface on poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)] membrane surface for the selective adsorption of low-density lipoprotein (LDL) was developed, which involved the photoinduced graft polymerization of acrylic acid followed by the chemical binding of carboxyl groups with glucosamine in the presence of 1-ethyl-3-(dimethyl-aminopropyl) carbodiimide hydrochloride and N-hydroxy-succinimide. The chemical structures of the fabricated membranes were characterized by attenuated total reflectance Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Zeta potential and water contact angle measurements were performed to investigate the surface charge and wettability of the membranes, respectively. An enzyme linked immunosorbent assay was used to measure the LDL adsorption on the plain and modified membrane surfaces. It was found that the surface glycosylation of P(3HB-co-4HB) membrane greatly enhanced the affinity interactions with LDL and the absorbed LDL could be easily desorbed with eluents, indicating a specific and reversible binding of LDL to the surface. Furthermore, the hemocompatibility of glycosylated membrane was improved as examined by platelet adhesion. The results suggest that the glycosylated P(3HB-co-4HB) membrane is promising for application in LDL apheresis therapy.     

Surface modification of poly(tetrafluoroethylene) films via grafting of poly(ethylene glycol) for reduction in protein adsorption

Poly(tetrafluoroethylene) (PTFE) films with surface grafted poly(ethylene glycol) (PEG) chains were prepared by two methods: (1) UV-induced graft copolymerization of methoxy poly- (ethylene glycol) monomethacrylate (PEGMA) onto the plasma-pretreated PTFE films; and (2) coupling of the hydroxyl groups of PEG via ester linkages with the carbonyl chloride groups which were introduced onto the acrylic acid (AAc) graft-copolymerized PTFE surface through reaction with thionyl chloride (SOCl2). The UV-induced graft copolymerization of PEGMA onto the plasma-pretreated PTFE film was explored with different macromonomer concentrations and different UV graft copolymerization time. The coupling reaction, on the other hand, was explored with PEG of different molecular weights. The surface microstructures and compositions of the PEG-modified PTFE films from both processes 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 for the UV-induced graft copolymerization with PEGMA. Contact angle measurements revealed that the hydrophilicity of the PTFE film surface was greatly enhanced by the grafting of the PEG chains. The PTFE surface with a high density of grafted PEG was very effective in preventing bovine serum albumin adsorption.     

Biocompatibility of fluorinated poly(organophosphazene)

We investigated neutrophil and platelet adhesion on a fluorinated poly(organophosphazene) in vitro. The results suggested that neutrophil and platelet adhesion on the poly(organophosphazene) only occurred on a few occasions, as observed by SEM. We demonstrated that the fluorinated poly(organophosphazene) showed excellent biocompatibility compared with the poly(organophosphazene) without the fluorinated side groups or PDMS. Additionally, we estimated the competitive plasma protein adsorption to the fluorinated poly(organophosphazene) using a gold-colloid-labeled immunoassay. Interestingly, the fluorinated poly(organophosphazene) film selectively adsorbed albumin when compared with gamma-globulin and fibrinogen, suggesting that a selective albumin adsorption on the film is responsible for the suppression of platelet adhesion.