Properties of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) films modified with polyvinylpyrrolidone and behavior of MC3T3-E1 osteoblasts cultured on the blended films

A series of composite films of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) modified with polyvinylpyrrolidone (PVP) was prepared by varying the ratio of constituents, and their properties and cytocompatibility were evaluated. The hydrophilicity of the blended materials surfaces increased and the amounts of fibronectin and laminin adsorbed on the materials surface increased remarkably compared with PHBHHx. FT-IR spectra of the blended films showed a new band, implying that a surface physical interpenetrating network structure had formed. Scanning electron microscopy showed that there were dense pits and holes on the blended films surface. For the films of PHBHHx with 20 wt% and 40 wt% PVP, MTT assay indicated that PVP enhanced cell adhesion and proliferation, but that the effects were impaired by excessive PVP. The results suggested that proper addition of PVP increased the cytocompatibility of PHBHHx because the material surface had increased hydrophilicity and presented an appropriate morphology.     

Novel biodegradable films and scaffolds of chitosan blended with poly(3-hydroxybutyrate)

In order to develop a novel biomaterial, films of chitosan blended with poly(3-hydroxybutyrate) (PHB) were prepared by an emulsion blending technique and their properties were characterized. Scanning electron microscopy (SEM) showed that PHB microspheres were formed and were entrapped in chitosan matrices, which made the film surface rough. With increasing PHB content, the roughness of the film surface increased, while the swelling capability of the films decreased. In a wet state, the blended films exhibited a lower elastic modulus, a higher elongation-at-break and a higher tensile strength compared with chitosan films. Cell-culture experiments revealed that the blended films had better cytocompatibility than chitosan films. To explore the potential application of the blended material in tissue engineering, the porous blended scaffolds were fabricated and their pore morphology was observed by SEM. The results revealed that not only pore structure but also pore wall morphology of the blended scaffolds could be controlled by selecting the parameters of the fabrication process. These advantageous properties indicate that the blended chitosan/PHB material is promising for tissue engineering applications.     

Modulating the Activities of Human Mesenchymal Stem Cells (hMSCs) and C3A/HepG2 Hepatoma Cells by Modifying the Surface Characteristics of Poly(3-hydroxybutyrate-co-3-hydroxyhexnoate) (PHBHHx)

The new biodegradable polyester poly(3-hydroxybutyrate-co-3-hydroxyhexnoate) (PHBHHx) has a potential application in tissue engineering. The aim of this study was to present a deeper picture of the relationship between the cellular behavior and the surface characteristics of PHBHHx films. The pristine PHBHHx film was prepared by adopting the compression-molding method, and then the acrylic acid molecules were grafted on PHBHHx membrane surface by UV irradiation. The hydrophilic nature and surface roughness of various PHBHHx films were controlled by adjusting the acrylic acid concentration and the UV irradiation time. Although the surface characteristics of various PHBHHx films could not affect the metabolic activity of hMSCs, the performance of morphology of hMSCs was deeply affected by the hydrophilic nature and the orientation of surface scars. The hydrophilic nature would effectively improve the spread of hMSCs, and the orientation of surface scars would guide the growth direction of cytoskeleton (actin) inside hMSCs. In contrast, the behaviors of C3A/HepG2 hepatoma cells presented an opposite outcomes. Those surface characteristics were obviously associated with the performance of metabolic activity of C3A cells, but not with the morphology of C3A cells. Both hMSCs and C3A cells have unique cellular characteristics; therefore, their responses to environmental stimulations are significantly different.     

Evaluation of three-dimensional scaffolds made of blends of hydroxyapatite and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) for bone reconstruction

Hydroxyapatite (HAP) was blended into poly(3-hydroxybutyrate) (PHB) and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) to make films and scaffolds. After HAP blending, mechanical properties of PHB including compressive elastic modulus and maximum stress showed improvement and osteoblast responses including cell growth and alkaline phosphatase activity were also strengthened. On the other hand, scaffolds made of PHBHHx blended with HAP had an adverse effect. No remarkable change on degradation of PHB or PHBHHx blended with HAP, respectively, was observed in simulated body fluid. Scanning electron microscopy examination revealed that osteoblast responses to HAP incorporation may be related to surface morphology and to the exposed HAP particles on polymer surface. All these results indicated that the blending of HAP particles into PHBHHx scaffolds fabricated by salt leaching was unable to either strengthen its mechanical properties or enhance osteoblast responses. Although HAP is bioactive and osteoconductive, its blending with PHBHHx did not generate a better performance on bone reconstruction.     

Novel biodegradable films and scaffolds of chitosan blended with poly(3-hydroxybutyrate)

In order to develop a novel biomaterial, films of chitosan blended with poly(3-hydroxybutyrate) (PHB) were prepared by an emulsion blending technique and their properties were characterized. Scanning electron microscopy (SEM) showed that PHB microspheres were formed and were entrapped in chitosan matrices, which made the film surface rough. With increasing PHB content, the roughness of the film surface increased, while the swelling capability of the films decreased. In a wet state, the blended films exhibited a lower elastic modulus, a higher elongation-at-break and a higher tensile strength compared with chitosan films. Cell-culture experiments revealed that the blended films had better cytocompatibility than chitosan films. To explore the potential application of the blended material in tissue engineering, the porous blended scaffolds were fabricated and their pore morphology was observed by SEM. The results revealed that not only pore structure but also pore wall morphology of the blended scaffolds could be controlled by selecting the parameters of the fabrication process. These advantageous properties indicate that the blended chitosan/PHB material is promising for tissue engineering applications.     

Physical Properties and Biocompatibility of Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) Blended with Poly(3-hydroxybutyrate-co-4-hydroxybutyrate)

Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) was blended with poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB) to improve physical properties and biocompatibility of PHBHHx for a wide range of biomedical applications. PHBHHx was completely miscible with P3HB4HB in their blends. All the PHBHHx/P3HB4HB blends showed improved physical properties compared with PHBHHx, including higher thermal stability, flexibility and mechanical strength. All the blends had more hydrophilic surface, higher polar component and rougher surface than PHBHHx. The PHBHHx/P3HB4HB blend in 4:2 weight ratio showed the roughest surface and also had the highest chondrocyte viability among all the blends and the polymers tested, which was 59% higher than that on PHBHHx and 32% higher than that on P3HB4HB. The blend with 4:2 weight ratio also had the maximum cartilage-specific collagen II mRNA expression among all the blends and the polymers tested, which was 9-times higher than that on PHBHHx and 8-times higher than that on P3HB4HB. These results demonstrated that PHBHHx had improved physical properties and biocompatibility after blending with P3HB4HB. The blends could be used for cartilage tissue engineering.     

Synthesis,Characterization and Cell Compatibility of Novel Poly(ester urethane)s Based on Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) and Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) Prepared by Melting Polymerization

Novel tailor-made poly(ester urethane)s (PUs) based on microbial polyesters poly(3-hydroxybutyrate-co-4hydroxybutyrate) (P3HB4HB) and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) were synthesized by melting polymerization (MP) using 1,6-hexamethylene diisocyanate (HDI) as a coupling agent. A comprehensive characterization using ¹H-NMR, Fourier transform infrared spectroscopy (FT-IR), gel-permeation chromatography (GPC), differential scanning calorimetry (DSC), mechanical properties, static water contact angles, cell proliferation using smooth muscle cells from rabbit aorta (RaSMCs) and immortalized human keratinocytes (HaCat), and blood coagulation behavior were conducted on the synthesized PUs films. DSC showed that PU samples had a low degree of crystallinity at room temperature and became fully amorphous after a melt-quenched process. The series of tailor-made PUs based on different mass ratios of P3HB4HB and PHBHHx revealed a ductile and flexile mechanical property especially for PHBHHx-rich PU, or a hydrophobic property for 4HB-rich PU. A 4 days incubation experiment showed that all PU films had a better cell proliferation than poly(lactic acid) (PLA), polyhydroxybutyrate (PHB), P3HB4HB and PHBHHx. RaSMCs cultured on PU films had a quiescent contractile phenotype, indicating that they were fully functional. HaCat incubated on tailor-made PU films showed a proliferation approximately equal to tissue-culture plates (TCPs). Blood coagulation behavior tests revealed a strong platelet adhesion and a short coagulation time on PU films. This study demonstrated potential medical applications for P3HB4HB and PHBHHx based polyurethane as a hydrophobic wound-healing and hemostatic materials.     

Effects of surface modification of poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) on physicochemical properties and on interactions with MC3T3-E1 cells

As a new member of the polyhydroxyalkanoate (PHA) family, poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) has better mechanical and processible properties than poly (3-hydroxybutyrate) (PHB). Still, it is difficult to introduce functional groups to the polyester carbon chain of PHBHHx, which restricts the modification of PHBHHx for a wide range. In this study, a procedure for the modification of the surface of PHBHHx films under strongly alkaline conditions was described. Through this kind of modification, carboxyl and hydroxyl groups were introduced to the surface and the total surface free energy was increased, which was mainly due to the increased polar components. Meanwhile, this process makes the surface rougher, resulting in larger total surface areas. After mineralization in simulated body fluids (SBFs), the apatite nucleation and growth on the surface-hydrolyzed PHBHHx films were significantly faster than on the unmodified PHBHHx films. This phenomenon should have a close relationship with the increased carboxyl and hydroxyl groups. The physicochemical properties also influenced the cell response to PHBHHx films. Compared to unmodified PHBHHx, fibronectin adsorption, and MC3T3-E1 cell attachment and proliferation were significantly greater on surface-hydrolyzed PHBHHx, which may be due to the increased surface free energy and rougher surface. Therefore, surface hydrolysis makes PHBHHx more suitable for osteoblast cell response and for application in bone-tissue engineering.     

In vitro study on hemocompatibility and cytocompatibility of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)

Samples of polyhydroxybutyrate (PHB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) containing 4–20% (mol/mol) 3-hydroxyhexanoate (3HHx) were characterized as potential components of blood-contact biomaterials. In an erythrocyte contact hemolysis assay, all tested PHBHHx films had substantially reduced reactivity, typically displaying about 2-fold less hemolytic activity compared with that of PHBV. Both 12% and 20% containing PHBHHx also bound less platelets than other films. After a 120-min exposure to platelet-rich plasma (PRP), few platelets adhered to the 12% and 20% containing PHBHHx films, while numerous platelets were seen on PHBV. Surface properties investigation suggested along with increasing 3HHx content, PHBHHx co-polymer films became smoother and smoother, which may contribute to lower platelet adhesion of PHBHHx containing high HHx content in a short-term contact to platelet-rich plasma. In a long-term contact to PRP, the difference in crystallization of PHBVand PHBHHx can be a critical parameter for platelet adhesion. Human umbilical vein endothelial cells (HUVECs) grew well on PHBHHx containing high content of 3HHx, indicating that both had good biocompatibility with HUVECs. While gelatin-coated or lipase-treated polyesters improved HUVECs proliferation compared with that on uncoated films, platelet adhesion was also decreased on gelatin-coated polyester. The hemocompatibility and biocompatibility of PHBHHx film were markedly improved. Thus, PHBHHx, particularly the surface-modified PHBHHx film, is promising for blood-contact materials.     

Effect of surface treatment on the biocompatibility of microbial polyhydroxyalkanoates.

The biocompatibility of microbial polyesters polyhydroxybutyrate (PHB) and poly(hydroxybutyrate-co-hydroxyhexanoate) (PHBHHx) were evaluated in vitro. The mouse fibroblast cell line L929 was inoculated on films made of PHB, PHBHHx and their blends, polylactic acid (PLA) as control. It was found that the growth of the cells L929 was poor on PHB and PLA films. The viable cell number ranged from 8.8 x 10(2) to 1.8 x 10(4)/cm2 only. Cell growth on the films made by blending PHB and PHBHHx showed a dramatic improvement. The viable cell number observed increased from 9.7 x 10(2) to 1.9 x 10(5) on a series of PHB/PHBHHx blended film in ratios of 0.9/0.1:0/1, respectively, indicating a much better biocompatibility in the blends contributed by PHBHHx. Biocompatibility was also strongly improved when these polymers were treated with lipases and NaOH, respectively. However, the effects of treatment were weakened when PHBHHx content increased in the blends. It was found that lipase treatment had more increased biocompatibility than NaOH. After the treatment biocompatibility of PHB was approximately the same as PLA, while PHBHHx and its dominant blends showed improved biocompatibility compared to PLA.     

Response of Human Mesenchymal Stem Cells (hMSCs) to the Topographic Variation of Poly(3-Hydroxybutyrate-co-3-Hydroxyhexanoate) (PHBHHx) Films

The influence of the topographic morphology of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) films on human mesenchymal stem cells (hMSCs) was investigated in this study. PHBHHx films with various surface characteristics were prepared by compression-molding, solvent-casting and electrospinning. The adhesion, proliferation and differentiation behaviors of hMSCs were significantly modulated by the surface characteristics of these films. HMSCs could aggregate and form cellular clusters on the cast PHBHHx films, and the time to form cellular aggregates increased as the surface roughness increased. The aggregated hMSCs on the cast films kept their original surface markers and presented much higher viability during the regular culture and lower differentiation ability upon osteogenic induction than the spread cells on the compression-molded films and TCPS. HMSCs spread well and showed a specific orientation on the surface of the random electrospun fibrous films, they were not able to migrate into the interior of electrospun fibrous films, and they revealed the highest viability during the regular culture but a lower differentiation activity upon osteogenic induction. The electrospun fibrous PHBHHx films could serve as a suitable substrate for large quantity culturing of hMSCs when undifferentiated hMSCs are desired.     

In vitro investigation of maleated poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) for its biocompatibility to mouse fibroblast L929 and human microvascular endothelial cells

Poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx), a polyester with strong mechanical properties and biocompatibility, is a member of microbial polyhydroxyalkanoates (PHA) family. Maleic anhydride was used to graft PHBHHx to form maleated PHBHHx (Ma-PHBHHx). Ma-PHBHHx with a graft degree of 0.59% was found to be more thermo-stable in comparison with PHBHHx. In vitro study demonstrated that the biocompatibility to mouse fibroblast L929 and human microvascular endothelial cells (HMEC) was improved in different degrees on Ma-PHBHHx films and scaffolds. Compared with their growth on PHBHHx, L929 and HMEC grown on Ma-PHBHHx films and scaffolds showed approximately 120% and 260% more in proliferation rates, respectively. Morphology study suggested that fine whorl-like surface structures with porosities on Ma-PHBHHx films attributed to MA grafting would be better for cell attachment and proliferation. Ma-PHBHHx scaffolds prepared by thermally induced phase separation (TIPS) with increased porosity, hydrophilicity, surface energy, and charges also were more favorable for cell growth. In addition, Ma-PHBHHx showed an accelerated degradation incubation in SBF at 37 degrees C, losing 21.4% of its original weight after 21 weeks while PHBHHx just lost 7.3%. Based on the improved biocompatibility, reasonable mechanical properties as well as accelerated biodegradation, Ma-PHBHHx has shown advantages over PHBHHx as a biomaterial for biomedical applications.     

Banded Spherulitic Morphology in Blends of Poly (propylene fumarate) and Poly(ϵ‐caprolactone) and Interaction with MC3T3‐E1 Cells

The thermal properties, morphological development, crystallization behavior, and miscibility of semicrystalline PCL and its 25, 50, and 75 wt% blends with amorphous PPF in spin‐coated thin films crystallized at various crystallization temperatures (T_c) from 25 to 52 °C are investigated. The surface roughness of PPF/PCL (?_PCL = 75%) films increases with increasing T_c and consequently the adsorption of serum proteins is also increased. No significant variance is found in surface hydrophilicity or in mouse MC3T3‐E1 cell attachment, spreading, and proliferation on PPF/PCL (?_PCL = 75%) films crystallized isothermally at 25, 37, and 45 °C, because of low ridge height, nonuniformity in structures, and PPF surface segregation.     

Improvement of blood compatibility on polysulfone-polyvinylpyrrolidone blend films as a model membrane of dialyzer by physical adsorption of recombinant soluble human thrombomodulin (ART-123)

ART-123 is a recombinant soluble human thrombomodulin (hTM) with potent anticoagulant activity, and is available for developing antithrombogenic surfaces by immobilization. We focused on improving blood compatibility on the dialyzer surface by the physical adsorption of ART-123 as a safe yet simple method without using chemical reagents. The physical adsorption mechanism and anticoagulant activities of adsorbed hTM on the surface of a polysulfone (PSF) membrane containing polyvinylpyrrolidone (PVP) as a model dialyzer were investigated in detail. The PVP content of the PSF-PVP films was saturated at 20 wt% after immersion in Tris-HCl buffer, even with the addition of over 20 wt% PVP. The surface morphology of the PSF-PVP films was strongly influenced by the PVP content, because PVP covered the outermost surface of the PSF-PVP films. The adsorption speed of hTM slowed dramatically with increasing PVP content up to 10 wt%, but the maximum adsorption amount of hTM onto the PSF-PVP film surface was almost the same, regardless of the PVP content. The PSF-PVP film with the physically adsorbed hTM showed higher protein C activity as compared to the PSF film, it showed excellent blood compatibility due to the protein C activity and the inhibition properties of platelet adhesion. The physical adsorption of hTM can be useful as a safe yet simple method to improve the blood compatibility of a dialyzer surface.     

Physicochemical properties and in vitro biocompatibility of PEO/PTMO multiblock copolymer/segmented polyurethane blends

A multiblock copolymer composed of poly(ethylene oxide) (PEO) and poly(tetramethylene oxide) (PTMO) and which forms a physical hydrogel was blended with Pellethane®, a commercial segmented polyurethane (SPU) developed for various biomedical devices, to provide a PEO-rich surface with improved stability. The effect of the copolymer blending was evaluated with respect to surface hydrophilicity, long-term stability, mechanical properties, in vitro protein adsorption, and platelet adhesion. A small amount of the copolymer additive (5 wt%) significantly improved surface hydrophilicity, which was then gradually enhanced by increasing the amount of the copolymer in the blends. The blend films exhibited minimal extraction of the copolymer additive when exposed to a buffer solution for 2 months at 37°C, resulting in less than 1 wt% weight loss of the films even with 30 wt% content of the copolymer in the blends. Although a certain degree of alteration in the mechanical properties was observed by increasing the copolymer content, the mechanical properties were well maintained for up to 10 wt% addition of the copolymer, when compared with the bare SPU. Protein adsorption was significantly reduced with a small amount of copolymer additive as low as 5 wt%. Fibrinogen, an adhesive protein for further cellular adhesion and activation, was effectively repelled by increasing the amount of copolymer additive. The platelet adhesion test revealed that the blend film surface reduced platelet adhesion and the degree of inhibition was proportional to the content of the additive, up to 30 wt%. The high molecular weight (M_w = 66 000) and compatible chemical structure of the copolymer with SPU made the surfaces PEO-rich and stable in an aqueous environment, resulting in an enhancement of the resistance to protein adsorption and platelet adhesion without a significant deterioration in physical properties.     

The mechanical properties and in vitro biodegradation and biocompatibility of UV-treated poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)

Strong mechanical properties and controllable biodegradability, together with biocompatibility, are the important requirement for the development of medical implant materials. In this study, an ultraviolet (UV) radiation method was developed to achieve controlled degradation for bacterial biopolyester poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) which has a low biodegradation rate that limits its application for many implant applications required quick degradation. When UV radiation was applied directly to PHBHHx powder, significant molecular weight (Mw) losses were observed with the powder, Mw reduction depended on the UV radiation time. At the same time, a broad PHBHHx Mw distribution was the result of inhomogeneous radiation. Interestingly, this inhomogeneous radiation helped maintain the mechanical properties of films made of the UV-radiated powder. In comparison, the PHBHHx films subjected to direct UV radiation became very brittle although their degradation was faster than that of the PHBHHx powders subjected to direct UV radiation. After 15 weeks of degradation in simulated body fluid (SBF), films prepared from 8 and 16h UV-treated PHBHHx powders maintained 92% and 87% of their original weights, respectively, while the untreated PHBHHx films lost only 1% of its weight. Significant increases in growth of fibroblast L929 were observed on films prepared from UV-radiated powders. This improved biocompatibility could be attributed to increasing hydrophilic functional groups generated by increasing polar groups C-O and CO. In general, UV-treated PHBHHx powder had a broad Mw distribution, which contributed to fast degradation due to dissolution of low Mw polymer fragments, and strong mechanical property due to high Mw polymer chains. Combined with its improved biocompatibility, PHBHHx is one more step close to become a biomedical implant material.     

Reduced mouse fibroblast cell growth by increased hydrophilicity of microbial polyhydroxyalkanoates via hyaluronan coating

The mouse fibroblast cell line L929 was inoculated on 3D scaffolds of microbial polyesters, namely polyhydroxybutyrate (PHB) and poly(hydroxybutyrate-co-hydroxyhexanoate) (PHBHHx) to evaluate their in vitro biocompatibility. It was found that both polyhydroxyalkanoates (PHA) subjected to lipase treatment and hyaluronan (HA) coating decreased the contact angle of water to the material surface approximately 30%, meaning an increased hydrophilicity on the PHA surface. At the same time, both the lipase treatment and the HA coating smoothened the PHA surface. After the lipase treatment or HA coating, the ratio of PHA hydrophilic groups including hydroxyl and carboxyl to carbonyl of PHA was approximately 1:1 or 2:1. Cells grown on scaffolds treated with lipase were approximately 4 x 10(5)/ml, twice in number of the control. However, PHA scaffolds coated with HA were observed with a 40% decrease in cell growth compared with that of the control. HA coating reduced the cell attachment and proliferation on PHA although the materials had increased hydrophilicity. In comparison, lipase treatment promoted the cell growth on PHA although the treatment did not lead to better hydrophilicity compared with HA coating. It appeared that an appropriate combination of hydrophilicity and hydrophobicity was important for the biocompatibility of PHBHHx, especially for the growth of L929 cells on the surface of this material. This may have instructive significance for biomaterial selection and design.     

Polyhydroxyalkanoate (PHA) scaffolds with good mechanical properties and biocompatibility

Blending microbial polyesters polyhydroxyalkanoates containing polyhydroxybutyrate (PHB) and poly(hydroxybutyrate-co-hydroxyhexanoate) (PHBHHx) were turned into films and scaffolds. The films made from blending polyesters showed that the elongation to break of the blending PHBHHx/PHB film increased from 15% to 106% when PHBHHx content in the blend increased from 40% to 60%. Scaffolds made of PHBHHx/PHB consisting of 60 wt% PHBHHx showed strong growth and proliferation of chondrocytes on the blending materials under scanning electron microscope. Energy dispersive X-ray analysis of the extra cellular matrix on the scaffolds demonstrated a high level of calcium and phosphorus elements in a molar ratio of Ca/P at 1.66, this is approximately equal to that of natural material hydroxyapatite which has a Ca/P ratio of 1.67. This suggested that the chondrocyte cells grown on PHBHHx/PHB scaffolds presented effective physiological function for generation of cartilage.     

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.     

Plasma modification of PMMA films: surface free energy and cell-attachment studies

The surface of a material is the most important part determining the acceptance by and compatibility with the environment. In many cases, although the bulk properties are excellent for a specific application, the surface may require to be modified and engineered in the desired direction. This is especially important for materials used in biological media, since the surface charge, hydophilicity and wettability are important for thrombosis formation, cell attachment or cell proliferation. In this study, poly(methyl methacrylate) films were prepared by solvent casting and their surfaces were modified by oxygen plasma treatment by applying powers of 20, 100 and 300 W. The effects of surface chemistry alterations on hydophilicity, work of adhesion, surface free energy and cell adhesion were examined. Cell attachment and proliferation are especially important for the materials used for tissue-engineering purposes. The results demonstrated that there is an optimum value for hydrophilicity and surface free energy which enhance cell attachment.