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.

We report the development of new biomacromolecule coatings on biodegradable biomaterials based on electrostatic assembly of extracellular matrix-like molecules. Poly (ethylene imine) (PEI) was employed to engineer poly (DL-lactide) (PDL-LA) substrate to obtain a stable positively charged surface. An extracellular matrix-(ECM-) like biomacromolecule, gelatin, was selected as the polyelectrolyte to deposit on the activated PDL-LA substrate via the electrostatic assemble technique. The extracellular matrix-like multilayer on the PDL-LA substrate was investigated by attenuated total reflection (ATR-FTIR), X-ray photoelectron spectrscopy (XPS), contact angle, and atomic force microscopy (AFM). The gradual buildup of the protein layer was investigated by UV-vis spectra, and it was further given a quantitative analysis of the protein layer on the PDL-LA substrate via the radioiodination technique. The stability of the protein layer under aqueous condition was also tested by the radiolabeling method. Chondrocyte was selected as the model system for testing the cell behavior and morphology on modified PDL-LA substrates. The chondrocyte test about cell attachment, proliferation, cell activity and cell morphology by SEM, and confocal laser scanning microscopy (CLSM) investigation on extracellular matrix-like multilayer modified PDL-LA substrate was shown to promote chondrocyte attachment and growth. Comparing conventional coating methods, polyelectrolyte multiplayers are easy and stable to prepare. It may be a good choice for the modification of 3-D scaffolds used in tissue engineering. These very flexible systems allow broad medical applications for drug delivery and tissue engineering.

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.

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

A coupling polymer, abbreviated SPEO-MDI-SPEO (MSPEO), was synthesized by a simple reaction between 4,4'-methylenediphenyl diisocyanate (MDI) and stearylpoly (ethylene oxide) (SPEO, Mn l900), and the blended poly (ether urethane) (PEU) films of PEU-MSPEO were prepared by a solution process. According to the analysis of ATR-FTIR, it was proved that when MSPEO was blended into the PEU matrix, the middle blocks (M-block) of MSPEO could incorporate with the hard blocks of PEU chains through the linkage of a H bond, leading to the improvement in the blending stability. The surface modification was finally accomplished by the self-motion of MSPEO since the elastomeric property of the matrix permits the modifiers to move freely. In the case of air, due to the relatively poor compatibility and rather low surface energy of the stearyl end groups, they migrated to the polymer-air interface, and thus the connected PEO chains were also enriched there by the tow of the end groups. However, in the case of water, the hydrophilic PEO chains migrated to the outermost layer of the surface, and finally they were enriched on the polymer-water interface, while the hydrophobic stearyl end groups would bend down back into the surface. Therefore, a PEO chain-loop structure was finally formed. Furthermore, also based on the mechanism of self-motioned surface modification, even if a part of MSPEO on the surface would have been washed away by water, the continuous makeup from the bulk would still be able to maintain the quantity of the PEO chains on the interface for a long time. All the results were verified by 1H NMR, ATR-FTIR, XPS, and contact angle measurements.