The ligand-tethered poly (ethylene oxide-propylene oxide-ethylene oxide) (PEO-PPO-PEO) triblock copolymer was explored to engineer poly (dl-lactic acid) (PDL-LA) material to promote cell attachment and growth. The PEO-PPO-PEO was activated by methyl sulfonyl chloride and the amino acid, and peptide were attached. By blending the PDL-LA with the ligand-tethered PEO-PPO-PEO derivatives, the surface of modified PDL-LA film was investigated by ATR-FTIR, XPS and contact angle. The chondrocytes test on different PDL-LA films indicated that the PEO-PPO-PEO amino acid and RGD derivatives modified PDL-LA films couldpromote chondrocyte attachment andgrowth. This simple surface treatment methodmay have potentials for tissue engineering andother biomedical applications.

Chitosan as an antibacterial agent and heparin as an anti-adhesive agent were alternatively deposited onto aminolyzed poly (ethylene terephthalate) (PET) films to construct anti-adhesive and antibacterial multilayer films. The contact-angle and UV data verified the progressive buildup of the multilayer film by alternate deposition of the polyelectrolytes. The properties of multilayer films were investigated by contact angle, atomic force microscopy (AFM), lateral force microscopy (LFM) and UV spectra. The results of initial adhesion of Escherichia coli (E. coli) on PET substrates showed that the number of E. coli adhered onto the control PET was in a much greater extent than onto the chitosan/heparin multilayer films, and the number of adhesive bacteria decreased with a decrease in assembly pH. The in vitro antibacterial test indicated that a multilayer of chitosan/heparin could kill the bacteria effectively. The number of viable bacteria decreased by 7% after 7h in contact with the control PET films, but by 46-68% for the multilayer-modified PET films. Only 3-8% of the cells were viable for the multilayer-modified PET films after 24 h. It is interesting to find the assembly pH has a remarkable effect on the antibacterial property of the multilayer. The number of viable bacteria on the multilayer assembled at pH1/4 3.8, 2.9 and 6.0 decreased by 68%, 58% and 46%, respectively. Such an easy processing and shape-independent method to prepare an anti-adhesive and antibacterial surface may have good potential for surface modification of cardiovascular devices.

Three types of stearyl poly (ethylene oxide) (SPEO) with Mn of 2300, 6000 and 12000 were ynthesized; accordingly, three types of amphiphilic coupling-polymer SPEO-MDI-SPEO (MSPEO) were prepared by the reactions with 4,4 -methylene diphenyl diisocyanate (MDI). As the surface-modifying additives (SMA), MSPEOs were coated onto the outer wall of the medical guiding catheters. Due to the lack of tability, when coated, MSPEO blended with the film building agent (FBA), poly(ether urethane) (PEL). The process of coating was performed with a lifter. With invariable speed, the PU guiding catheter was vertically dipped into the coating mixture of SMA-MSPEO and FBA-PEL. The surface analysis was carried out by ATR-FTIR and contact angle measurements. It was proved that the surface enrichment of PEO on water interface was much higher than that on air interface. Three kinds of static clotting time tests, PRT, PT and TT, as well as the static platelet adhesion experiment were performed. The results indicated that the coated surface could resist the blood coagulation electively. In order to test the blood compatibility of the coated catheters under a shear of blood #ow, the dynamicexperiment was performed with a closed-loop tubular system under a shear rate of 1500s. The blood regular testing was carried out on the samples taken out at six di!erent times (0, 5,10, 20, 30 and 60min). The results were ideal. Finally, the SMA-MSPEO was proved to be non-acute-toxic by LD

Chitosan and chitosan-amino acid derivatives were explored to engineer poly (D,L-lactic acid) (PDL-LA) as an extracellular matrix-like surface to promote cell adhesion and growth. Four kinds of chitosan-amino acid derivatives were prepared to mimic the carbohydrate moieties of cell matrix glycoprotein. The chitosan-amino acid derivatives were characterized by using Fourier transform infrared and ultraviolet spectra. The amino acid content on chitosan-amino acid derivatives was determined by using a ninhydrin-ultraviolet method. A new strategy, entrapment, was therefore used to modify the PDL-LA membrane with chitosan and chitosan–amino acid derivatives. The results of X-ray photoelectron spectroscopy, attenuated total reflectance-Fourier transform infrared, and contact angle confirmed that a stable thin film of chitosan and its derivatives can be entrapped on the surface of the PDL-LA membrane. From the results of chondrocyte cytocompatibility, MTT [3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide] assays, and cell morphology, the chitosan–amino acid derivative modified PDL-LA membranes were shown to promote chondrogenesis. The novel surface treatment method combines the good mechanical property of PDL-LA with the good ytocompatibility of chitosan derivatives, which may have potential for tissue engineering.

Thin polymer films were formed on poly-(dl-lactide) (PDL-LA) using polyelectrolyte multilayer technique to promote the chondrocyte cytocompatibility. PDL-LA substrates were activated by poly-(ethylenimine) to obtain stable positively charged surface. The polyelectrolytes such as alginate and poly-(l-lysine) were alternatively deposited onto the activated PDL-LA substrates. The multilayer-modified PDL-LA films were investigated by X-ray photoelectron spectroscopy, attenuated total reflection FTIR, contact angle and atomic force microscopy. The in vitro chondrocyte test indicated that the multilayer-modified PDL-LA substrates promoted chondrocyte attachment and growth. In comparison to conventional coating methods, polyelectrolyte multilayers are easy to prepare and the procedure is valid whatever the shape of the solid. It allows broad medical applications for drug delivery and tissue engineering.