Surface Construction And Bio-compatibility Of A Novel Polyurethane Material For Cardiovascular Biomedical Applications

The destination of this research is to develop and prepare a novel transplantable (intravascular) polymeric material for the application of cardiovascular tissue engineering. A "ABA"-typed coupling-polymer of poly(ethylene oxide) [PEO] and 4,4'-diphenylmethylene diisocyanate [MDI], "PEO-MDI-PEO" [MPEO], was designed and synthesized. Then several kinds of functional groups were employed to react with the reactive hydroxyl endgroups of MPEO, and finally a series of "CABAC'-typed block coupling-polymer with functional endgroups, "endgroup-PEO-MDI-PEO-endgroup", were yielded. The products include MSPEO with stearyl endgroups [C-18], cibaMPEO with Cibacron Blue endgroups [ciba], AA-MPEO with several kinds of amino acid endgroups and RGD-MPEO with Arg-Gly-Asp tri-peptide endgroups, as well as two protein-ended coupling-polymers, Albumin-MPEO and Gelatin-MPEO. The LD50 test and the testing of quasi-chronic toxicity (including the testing in acute stage and convalescence) by mainline were respectively performed on rats to characterize the products' in vivo tissue-compatibility. Ideal results were obtained. Based on the long-term in vivo security of the coupling-polymers, they were used as the surface modifying additives (SMA) for the surface treatment of medical poly(ether urethane) [PEU], Both the methods of blending in the bulk and coating on the surface were developed. The acquired products were tested on the modified surfaces respectively by the experiments of serum protein adsorption, in vitro hemo-compatibility and human endothelial cell-compatibility, through which the modified surfaces' performance of bio-compatibility and cell compatibility was confirmed.First of all, through the analysis of ATR-FTIR, XPS and contact angle measurements, the interaction between the blending components, as well as the surface conformation, was detected. The results indicated that the SMA-M(S)PEO was incorporated with the PEU matrix via some carbonyl-amino hydrogen bonds which were formed between the middle urethane block of SMA-M(S)PEO and the "hard" block of the matrix PEU chains, based on which a model of "Blended Grafting via H-bond" (BGH) was brought up by us. Simultaneously, it was also indicated that the surface modification on the PEU matrix was accomplished by the SMAs' spontaneous migration and enrichment. The corresponding behaviors were on the basis of both the SMA's amphiphilic property and the elastomeric property of the PEU matrix that permitted the relatively free motion of the molecularchains in the bulk. The driving force of the migration was originated from the phase-separation between the SMA and PEU matrix which were incompatible each other, and the orientation of the migration was directed by the SMA's decreasing tendency of surface energy. Based on the analysis above, a model of "Self-motioned Surface Enrichment" (SMSE) was raised, and another phenomenon of "Finite SMA Loss from Surface, Continuous Makeup from Bulk" was also discovered and explained. Up to then, both the realizability and stability of the surface modification through the blending-coating methods were confirmed. Thus, these simple, convenient and effective techniques were founded. Furthermore, the take-off angle-depended XPS technique was also employed to detect the content of the endgroups at different depth in the surface layer of the modified materials, in order to characterize the degree of the effect to surface conformation by the interaction between the endgroups and the various-sized PEO spacer. As a typical example, a "PEO-chain-loop" conformation that was formed by the short-chained MSPEO on the polymer-water interface was discovered and brought up. Compared with the surface system of bulk-blending, within the surface-coating system, the driving force of phase-separation between the SMA-M(S)PEO and the PEU matrix was strengthened, while the kinetic resistance to the "Self-motioned Surface Enrichment" was weakened.On the coating-modified surfaces ctMSPEO and ct-cibaMPEO (with PEU as the film building additives [FBA]), the...