Novel human endothelial cell-engineered polyurethane biomaterials for cardiovascular biomedical applications.

A tri-block coupling-polymer composed of 4,4'-methylenediphenyl diisocyanate and poly (ethylene oxide) (PEO), abbreviated MPEO, was used as the template surface-modifying additive (SMA), based on which selected amino acids (lysine, arginine, glycin, and aspartic acid) and RGD peptide were respectively conjugated as functional endgroups of the PEO spacer-arms through sulfonyl chloride-activation routes. After the immobilization of biofunctional factors, the SMA-MPEO derivatives were noncovalently introduced onto the biomedical poly(ether urethane) (PEU) surfaces by physical blending methods. The SMA synthesis and PEU surface modification were monitored and analyzed by nuclear magnetic resonance spectroscopy, attenuated total reflection-infrared spectroscopy, and X-ray photoelectron spectroscopy. The human umbilical vein endothelial cells (HUVECs) were collected and harvested manually by collagenase digestion. The cell culture was performed respectively on the MPEO derivative-modified PEU surfaces and also on the surfaces of the commercially available polystyrene cell-culture plates (TCPS) for control. The cell adhesion rates and cell proliferation rates of the in vitro cultivated HUVEC were measured using flow cytometry. The individual cell viability rates were determined with MTT assay. The cell morphologies of the living HUVECs were investigated by optical inverted microscopy, and more detailed information was acquired from scanning electrical microscopy. The results indicated that the efficacy of SMA functional endgroups was the dominant factor for HUVEC compatibility; the proper-sized PEO spacers (M(w) 2 k) could support and mobilize the functional endgroups, optimizing the surface (interface) environment for the cell growth. As the endgroups of the SMA-MPEO derivatives and the bio-functional factors, the basic amino acids (lysine and arginine) demonstrated similar performances to that of the widely acknowledged cell growth-promoter, RGD peptide, which were superior to TCPS. Therefore, these MPEO derivative-modified PEU materials are promising to serve as novel polymeric permanent implants or interventional devices for cardiovascular biomedical applications.

In situ immobilization of proteins and RGD peptide on polyurethane surfaces via poly(ethylene oxide) coupling polymers for human endothelial cell growth.

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 ((1)H NMR), attenuated total reflection infrared spectroscopy (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 significant impact on the cell responses to the modified surfaces.

Selective adsorption of serum albumin on biomedical polyurethanes modified by a poly(ethylene oxide) coupling-polymer with cibacron blue (F3G-A) endgroups.

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 (125)I-probe and ATR-FTIR were, respectively, employed for the characterization. The competitive adsorption of BSA and bovine serum fibrinogen (Fg) in the BSA-Fg binary solutions was also studied using a (125)I-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.