Self-assembly In The Solution And Surface Modification Of The Biocompatible Comb-like Copolymer

The dissertation focuses on the self-assembly of three comb-like copolymers in the water and surface tailoring of the biomedical polyester via comb-like coploymers. Three comb-like amphiphilic copolymers including poly(ethylene glycol)-b-poly(methacrylate stearyl)(PEG-b-PSMA), comb-like PEG(CPEG)and its derivative CPEG-g-cholesterol was prepared. The self-assembly of three comb-like copolymers in the water was investigated. And the biomedical polyester was surface-modified by CPEG for the improving biocompatibility.PEG-b-PSMA with hydrophobic stearyl side chains was synthesized by the atom transfer radical polymerization (ATRP). The results of DSC and XRD showed that the PEG-b-PSMA was side-chain crystalline and appeared α_H packing. The aqueous solution of PEG-b-PSMA was prepared by the dialysis. The critical micelle concentration (CMC) was determined as 3.03×10^-4g/L by fluorescent spectrometer. TEM showed that PEG-b-PSMA in the water formed vesicles. SEM and laser particle diameter analyzer showed that vesicles were dominant in aggregations and with the homogenous diameter. The crystallization of the membrane in vesicles was indicated by the evident endothermic peak of stearyl groups in the DSC curve. The stretching of dense comb-like side chains affected by the crystalline interaction of side chains was important for the dominant number and homogeneous diameter of vesicles.CPEG with hydrophilic PEG side chains end-capped by hydroxyl groups was synthesized by the ATRP. The CPEG was dissolved directly in the double deionzied water to prepare the aqueous solution of CPEG. ¹H-NMR and fluorescence spectrometer indicated the onset of the aggregation of CPEG at 5.76×10^-3g/L. TEM, SEM and AFM indicated that CPEG only formed micelles in the water below 1.13×10^-2g/L, but formed hollow vesicles above 1.13×10^-2g/L. The asymmetric comb-like structure and dense side chains of the highly hydrophilic copolymer was supposed to be important for the vesicles formation.CPEG was also derived into CPEG-g-cholesterol, which began to spontaneouslyaggregate in the water at 2.07×10^-3g/L. TEM indicated that the morphology of vesicles appeared the corrugation different from that of CPEG. The membrane thickness of CPEG-g-cholesterol also increased compared to that of CPEG. The vesicles formation via self-assembly of CPEG-g-cholesterol indicated again the importance of the comb-like structure with dense side chains.The terminal hydroxyl groups in CPEG of the aggregations were cross-linked by divinyl sulfone. The results of XPS and laser particle diameter analyzer showed the resulting aggregations did be cross-linked. TEM indicated that the cross-linking happened in aggregations and did not destroy their morphology. When the hydrophobic doxorubicin was added into the uncross-linked aggregations, the vesicles disappeared. But when the doxorubicin was added into the cross-linked aggregations, vesicles still existed and doxorubicin aggregated in the corona of vesicles, which indicated that the cross-linking improved the stability of the vesicles and the vesicles did form in the water by self-assembly of CPEG.CPEG whose terminal hydroxyl groups in side chains of were oxygenated into aldehyde groups was attached onto the aminolyzed PET then was further functionalized by L-lysine subsequently. XPS showed PET-CPEG-lysine had the higher PEG and the nitrogen content than PET-LPEG10k-lysine. The PET-CPEG resisted the adhesion of platelets efficiently, which showed its good hemo-compatibility. PET-CPEG could resist the cell adhesion, proliferation and spreading. The cells on PET-CPEG had the lower viability. But PET-CPEG-lysine could promote the cell growth, proliferation and higher cell viability.CPEG-gel coating was prepared by dried the CPEG coating on the PET. The stability of CPEG coating was indicated by contact angle and weight analysis. The FT-IR results showed that the intra-chain hydrogen bonds existed in CPEG-gel coating, which might contribute to the gel formation. The result of in vitro platelets adhesion indicated that the CPEG-gel coating resisted the platelets adhesion and so had better hemocompatiblity. The CPEG-gel coating could also resist the cell adhesion, proliferation and spreading efficiently. The cells on CPEG-gel coating had the lower viability. But PET-CPEG-lysine could promote the cell growth and proliferation and higher cell viability.