Layer-by-Layer Assembly Of Biomacromolecules To Improve The Cytocompatibility Of PET Artificial Blood Vessels

Poly(ethylene terephthalate) (PET) has been used successfully in treating the pathology of large diameter arteries (>6 mm, inner diameter), but has not been proven to be successful in replacing small diameter blood vessels (<6 mm). Incomplete coverage of endothelial cells (ECs) on the vascular graft surfaces and the subsequent myointimal hyperplasia are the main reasons for the long-term failure of the small-diameter vascular graft. Endothelialization is one approach to solve this problem. In order to carry out the endothelialization of vascular graft, surface modification is needed to produce cytocompatible interfaces.The destination of this study is to fabricate cytocompatible surface or interface on PET material via surface modification. Fristly, using the typical method of hydrolysis, carboxyl groups were introduced onto the surface of PET film. The occurrence of hydrolysis was confirmed by X-ray photoelectron spectroscopy (XPS) characterization. The existence of carboxyl groups on the hydrolyzed PET film surface was verified quantitatively by a toluidine blue O (TBO) method. By changing the concentration of NaOH solution, the temperature and time of the reaction, the density of carboxyl groups, as well as the hydrophilicity and surface roughness can be changed.Introduction of carboxyl groups increases the hydrophilicity of the PET film. Moreover, it also provides the possibility to modify the PET surface in a simple manner, as examplified here, with layer-by-layer (LBL) assembly of charged species, since the hydrolyzed PET can be used as a negatively charged substrate. Assembly of positively charged chitosan and negatively charged chondroitin sulfate (CS) was then conducted in a LBL manner to create multilayers on the hydrolyzed PET film. The process of layer growth and oscillation of surface wettability were monitored by UV-vis spectroscopy and water contact angle measurement, respectively. In vitro cell culture revealed that the adherence of endothelial cells was significantly enhanced on the biomacromolecules-modified PET film with preserved endothelial cell function, in particular on those assembled with larger number of chitosan/CS layers. However, with regard to cell proliferation and viability properties after cultured for 4 days, minor difference was determined between the modified and the unmodified PET films.In order to improve the cell proliferation, collagen type I and chondroitin sulfate were chosen to be deposited onto the hydrolyzed PET film. Unlike the chitosan/CS system, the collagen/CS multilayers grew nonlinearly on the PET film surface. Human endothelial cells culture in vitro demonstrated that five layers of collagen/CS modified PET film had the most cytocompatible surface with the potency to improve cell proliferation.Using the method of hydrolysis and further LBL assembly of biomacromolecules, PET fiber fabric vascular graft was modified to enhance cell-material interaction. The "S" shaped growth curve of endothelial cells indicated that the cells grew well on the modified graft. SEM observation also showed the normal spreading endothelial cell morphology. Therefore, a novel modification technique, i.e. LBL self-assembly, on materials with complicated shape has been developed. It is believed to attract more and more attention in tissue engineering due to its simplicity and versatility.