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.

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 signifi cantly. 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.

A tri-block-coupling polymer, "PEO-MDI-PEO" ["poly (ethylene oxide)-4,4'-methylene diphenyl diisocyanate-poly (ethylene oxide)", abbreviated "MPEO"], was used to react with a triazine dye, Cibacron Blue F3G-A (ciba), in an alkaline environment. The product of this nucleophilic reaction was a penta-block-coupling polymer, "ciba-PEO-MDI-PEO-ciba" (abbreviated "cibaMPEO"). The cibaMPEO-modified poly (ether urethane) (PEU) surfaces were prepared by dip-coating and detected by XPS. The surface enrichment of both ciba endgroups and poly (ethylene oxide) spacer-arms was revealed. On the modified surfaces, bovine serum albumin (BSA)-adsorbing experiments were carried out, respectively, in the low and high BSA bulk-concentration solutions, and accordingly, the methods of radioactive 1251-probe and ATR-FTIR were, respectively, employed for the characterization. The competitive dsorption of BSA and bovine serum fibrinogen (Fg) in the BSA-Fg binary solutions was also studied using a 125I-probe, and through which the reversibly BSA-selective adsorption on cibaMPEO-modified PEU surfaces was confirmed. Finally, the improvement of blood-compatibility on the modified surfaces was verified by the plasma recalcification time (PRT) test.

Poly (vinyl chlorides)-graft-[v-stearylpoly (ethylene oxide)] (PVC-g-SPEO), which has a poly (vinyl chloride) (PVC) backbone, poly (ethylene oxide) (PEO) side chain, and stearyl end groups, has been synthesized. Selforganizing blends of the amphiphilic comb polymer in poly-(vinyl chlorides) have been examined as a means to create albumin preferential surfaces on polymer films. X-ray hotoelectron spectroscopy (XPS) analysis indicates substantial surface segregation of the PVC-g-SPEO. A surface concentration of 59.9 EO wt % is achieved by the solution casting and heat treatment of a film with a bulk concentration of only 3.78 EO wt %. In the aqueous environment, the surface rearrangement of PVC-g-SPEO/PVC blend film is limited (to J.J.) and presents a high interfacial energy and high epolar component of interfacial energy due to the "tail-like" SPEO side chain. Protein adsorption tests confirm that PVC-g-SPEO/PVC blend films absorb high levels of albumin and dramatically resist fibrinogen adsorption. Surfaces to attract and reversibly bind albumin, which might diminish the occurrence of thrombosis, inflammation, and infection, are developed by self-organizing blends of the amphiphilic comb polymer in poly (vinyl chlorides).

Summary: Novel biomimetic surfactants based on cholesterol as the hydrophobic segment and poly[2-(methacryloyloxy) ethyl phosphorylcholine] (pMPC) as the hydrophilic segment were synthesized in the present study by atom transfer radical polymerization (ATRP) of 2-(methacryloyloxy)-ethyl phosphorylcholine (MPC) using a cholesterol-based macroinitiator. The association behavior of cholesterolblock-poly[2-(methacryloyloxy)ethyl phosphorylcholine] (Chol-pMPCs) in aqueous solution was studied by 1H NMR spectroscopy, fluorescence probe technique, and atomic force microscopy (AFM). The 1HNMRspectrum of the polymer in CD3OD showed both the cholesterol group and the phosphorylcholine group while the cholesterol group did not appeared in the 1H NMR spectrum of the polymer in D2O, which implied the formation of a micelle structure. Fluorescence excitation spectra of a pyrene probe solubilized in the aggregates of Chol-pMPCs suggested the presence of a critical micelle concentration (cmc) in water. The critical micelle concentrations of the polymers CMPC10, CMPC20 and CMPC40 were determined to be 7.27×10-3, 13.47×10-3, and 20.77×10-3mg•mL-1, respectively. AFM images of the aggregates on mica suggested that the pMPC block formed the biocompatible micelle coronas and the cholesterol block formed the hydrophobic micelle cores. These newbiomimetic diblock copolymers were evaluated as "stealthy" nanocapsules for the delivery of hydrophobic drugs. The anti-cancer drug adriamycin (ADR) was chosen as a hydrophobic drug to be incorporated into the inner core of the micelles and the morphology of the drug-loaded micelles were observed by AFM. Schematic of the biomimetic block copolymers and their micellization, and an AFM image of the micelles deposited on mica.

A "CBABC"-type pentablock coupling polymer, mesylMPEO, was designed and synthesized to promote human endothelial cell growth on the surfaces of polyurethane biomaterials. The polymer was composed of a central 4,4'-methylenediphenyl diisocyanate (MDI) coupling unit and poly(ethylene oxide) (PEO) spacer arms with methanesulfonyl (mesyl) end groups pendent on both ends. As the presurface modifying additive (pre-SMA), the mesylMPEO was noncovalently introduced onto the poly(ether urethane) (PEU) surfaces by dip coating, upon which the protein/peptide factors (gelatin, albumin, and arginine-glycine-aspartic acid tripeptide [RGD]) were covalently immobilized in situ by cleavage of the original mesyl end groups. The pre-SMA synthesis and PEU surface modification were characterized using nuclear magnetic resonance spectroscopy (1H NMR), attenuated total reflection infrared pectroscopy (ATR-FTIR), and X-ray photoelectron spectroscopy (XPS). Human umbilical vein endothelial cells (HUVEC) were harvested manually by collagenase digestion and seeded on the modified PEU surfaces. Cell adhesion ratios (CAR) and cell proliferation ratios (CPR) were measured using flow cytometry, and the individual cell viability (ICV) was determined by MTT assay. The cell morphologies were investigated by optical inverted microscopy (OIM) and scanning electrical microscopy (SEM). The gelatin- and RGD-modified surfaces were HUVEC-compatible and promoted HUVEC growth. The albumin-modified surfaces were compatible but inhibited cell adhesion. The results also indicated that, for HUVEC in vitro cultivation, the cell adhesion stage was of particular importance and had a ignificant impact on the cell responses to the modified surfaces.