Linxian Feng

Surface engineering of poly(DL-lactic acid) by entrapment of alginate-amino acid derivatives for promotion of chondrogenesis

Alginate-amino acid derivatives were explored to engineer poly(DL-lactic acid)(PDL-LA) as glycocalyx-like surface to promote cell adhesion and growth. Four different kinds of alginate-amino acid derivatives were synthesized to mimic the glycocalyx of cell membrane to promote chondrogenesis. The alginate-amino acid derivatives were characterized by FT-IR, 1H NMR and UV spectra and the amino acid content on alginate-amino acid derivatives was given by ninhydrin-UV method. A new strategy, entrapment, was then employed to modify PDL-LA membranes with alginate and its amino acid derivatives. The results of XPS, ATR-FTIR and contact angle confirmed that a stable thin film of alginate and its amino acid derivatives can be entrapped on the surface of PDL-LA membrane. The chondrocyte cytocompatibility test and MTT assays indicated that the alginate-amino acid derivatives modified PDL-LA membranes could promote chondrogenesis. The novel surface treatment method may have potentials for tissue engineering and other biomedical applications.

Surface photo-grafting of polyurethane with 2-hydroxyethyl acrylate for promotion of human endothelial cell adhesion and growth

Cytocompatible polyurethane (PU)surface was prepared by photo-grafting 2-hydroxyethyl acrylate (HEA) onto the membrane surface. Graft polymerization was conducted by combining the use of the photo-oxidation and irradiation grafting. PU membrane was photo-oxidized to introduce the hydroperoxide groups onto the surface, then the membrane, immersed previously in monomer solution, was irradiated under UV light. The ATR-FTIR spectra, element spectroscopy for chemical analysis (ESCA), scanning electron microscopy (SEM) and water contact angle characterized the grafted copolymers and verified the occurrence of graft polymerization. The results showed that UV irradiation could realize the graft polymerization effectively and the grafting was confined within the surface layer. The grafted membrane showed minimal surface morphology. Human umbilical vein endothelial (HUVE) cells were seeded on the grafted surface. The performance of the surface in cell attachment and growth correlated with the oxygen content and mainly the carbonyl content on the surface. Cells were spread more extensively and grew faster on the surface with a higher oxygen content.

Stearyl poly(ethylene oxide) grafted surfaces for preferential adsorption of albumin

Abstract An ideal surface for many biomedical applications would resist non-specific protein adsorption while at the same time triggering a specific biological pathway. Based on the approach of selectively binding albumin to free fatty acids, stearyl groups were immobilized onto poly(styrene) backbone via poly(ethylene oxide) side chains. X-ray photoelectron spectroscopy (XPS) analysis indicates substantial surface enrichment of the stearyl poly(ethylene oxide) (SPEO). In an aqueous environment, the surface rearrangement is limited, as proved by dynamic contact angle tests. The comb-like copolymer presents a special hydrophobic surface with high SPEO surface density, which may be due to the ‘tail like’ SPEO architecture at the copolymer/water interface. Protein adsorption tests confirm that the comb-like surfaces adsorb high levels of albumin and resist fibrinogen adsorption very significantly. The surfaces prepared in this research attract and reversibly bind albumin due to the synergistic action of the PEO chains and the stearyl end groups.

Factors controlling surface morphology of porous polystyrene membranes prepared by thermally induced phase separation

A special device for preparing porous polymer membranes through a thermally induced phase separation (TIPS) process was designed and machined; it included a solution container, a membrane-forming platform, a coldplate, a temperature-decreasing system and a temperature-supervising system. Polystyrene was selected as the model polymer from which to prepare porous membranes using the device due to its better understood TIPS and good biocompatibility with cells. The major factors controlling surface morphology and cell size, ie volume fraction of polystyrene (ϕ2), quench rate and solvent-removing methods, were studied. Fixing the coldplate temperature, when ϕ2 is as low as 0.045, provokes the formation of round pores on both the bottom and top surfaces of the membrane; when ϕ2 = 0.16 no pores are formed on either surface; when ϕ2 = 0.087 pores form on the top surface, but not on the bottom surface. When ϕ2 = 0.087 the cell size is very small or no pores are formed on the bottom surface, whereas the top surface shows a regular decrease of the pore sizes and an increase of the pore number and pore area, along with a decrease of the coldplate temperature. The side near the coldplate is dense, and the dense layer aligns along the coldplate, while the side away from the coldplate is like a porous foam, the shape of which is isotropic and the surfaces are interconnected with each other three dimensionally. On the top surface of a membrane obtained by ethanol extraction, the cell size is enlarged and the cell number reduced, but the surface morphology and the whole area remained almost the same when compared to samples obtained by freeze drying in the same membrane-forming conditions. The isotropic, uniformly distributed and round pores suggest that the mechanism of phase separation is a spinodal liquid–liquid decomposition under our research conditions. © 2000 Society of Chemical Industry

Surface modification of polyurethane for promotion of cell adhesion and growth 1: surface photo-grafting with N,N-dimethylaminoethyl methacrylate and cytocompatibility of the modified surface.

Functional polyurethane (PU) surface was prepared by photo-grafting N,N-dimethylaminoethyl methacrylate (DMAEM) onto the membrane surface. Grafting copolymerization was conducted by the combined use of the photo-oxidation and irradiation grafting. PU membrane was photo-oxidized to introduce the hydroperoxide groups onto the surface, then the membrane previously immersed in monomer solution was irradiated by UV light. The X-ray photoelectron spectroscopy and water contact angle characterized the grafted copolymers and verified the occurrence of graft copolymerization. The results showed that UV irradiation could realize the graft copolymerization effectively. The grafted membrane showed minimal surface morphology. Human umbilical vein endothelium (HUVE) cells were seeded on the grafted surfaces. The performance of the surface in cell attachment correlated with the content of oxygen and nitrogen. Cells were spread more extensive and grown faster on the surface with lower degree of grafting.

A novel urethane containing copolymer as a surface modification additive for blood contact materials

Surface modification to develop a biomolecules-presenting surface is of interest, both from a scientific and an industrial point of view. In this research, a penta-block-coupling polymer of warfarin–PEO–MDI–PEO–warfarin was specially designed as the surface modifying additive (SMA). The warfarin-modified polyurethane surfaces were then prepared by dip-coating method. Attenuated total reflection fourier transform infra-red (ATR-FTIR) spectra revealed that the urethane segments in the SMA could penetrate into the hard block of segmented polyurethane (SPU) via intermolecular hydrogen bonds. The X-ray photoelectron spectroscopy (XPS) results indicated that the intermolecular hydrogen bonds were strong enough to form stable warfarin-PEO composite surfaces in an aqueous environment. Fibrinogen and albumin adsorption onto unmodified and SMA-modified SPU was investigated by the 125I-labeled method. The surface for attracting and reversibly binding albumin, which was proved to suppress the platelet adhesion and prolong the clotting time, has been developed by the simple coating of the novel SMA in SPU.

Selective binding of albumin on stearyl poly(ethylene oxide) coupling polymer-modified poly(ether urethane) surfaces.

A tri-block-coupling polymer of stearyl poly(ethylene oxide)-4,4′-methylene diphenyl diisocyanate-stearyl poly(ethylene oxide)(MSPEO), was used as a surface modifying additive (SMA) and the MSPEO-modified poly(ether urethane) (PEU) surfaces were prepared by the process of dipcoating. The surface analysis by XPS revealed the surface enrichment of poly(ethylene oxide) (PEO). On the coating-modified surfaces, the bovine serum albumin (BSA) adsorption, respectively, from the low and high BSA bulk concentration solutions was correspondingly characterized by the methods of radioactive 125I-probe and ATR-FTIR. The bovine serum fibrinogen (Fg)-adsorption from the Fg bulk solution and the BSA-Fg competing adsorption from the BSA-Fg binary solutions were also characterized by radioactive 125I-probe. The reversible BSA-selective in situ adsorption on MSPEO-modified PEU surfaces were achieved, and the performance of blood compatibility on the coating-modified surfaces was also confirmed, respectively, by plasma recalcification time (PRT) and prothrombin time (PT) tests.