Shape-Memory Polymeric Micro-Patterned Surface For Vascular Tissue Engineering

The application of tissue engineering technology to vascular surgery holds great promise for improving outcomes in patients with vascular diseases. Currently used synthetic vascular grafts have many limitations compared with body’s own vascular tissues. In this paper, we report a method for ECs/SMCs co-culture using shape memory polymer substrates with concentric microgrooves. Then the shape memory micropatterned substrates were prepared into tissue engineering vascular scaffolds, and implanted into the rabbit carotid artery to investigate the vascularization of the vascular scaffolds in the blood vessel.Firstly, crosslinked four arm poly (ethylene glycol)-poly (ε-caprolactone)-acryloyl chloride (c-4 arm PEG-PCL) was prepared by ring-opening polymerization, electrophilic substitutive reaction and UV-light crosslinking. FT-IR and 1H-NMR were done to demonstrate the chemical structure of the 4 arm PEG-PCL-AC. The thermal properties, crystallization properties and shape memory properties of c-4 arm PEG-PCL were analyzed by differential scanning calorimetry (DSC), X-ray diffractometry (XRD) and dynamic mechanical thermal analysis (DMA). The results indicated that the polymer possessed great shape memory effect (SME), including high shape fixity ratio (Rf) and recovery ratio (Rr). And the transition temperature is closely to body temperature.Secondly, the method of thermal embossing microprint lithography was used to prepare shape memory substrates with different micropatterns, they are concentric circular microgrooves and assembled circular microgrooves (composed by concentric circular microgrooves and radial straight microgrooves). Scanning electron microcopy (SEM) images showed that the surface micropatterns also had good microscopic SME. Cell morphology and behavior assay was also performed by culturing ECs/SMCs on the dynamic micropatterned surfaces. The results showed that the micropatterned surfaces accompanying with the dynamic change can regulate the cell distribution between ECs/SMCs more effectively compared with the non-patterned and static patterned surfaces.Finally, the shape memory polymer substrates with micropatterned surfaces were prepared into tubular vascular scaffolds, and implanted into the carotid artery of the New Zealand white rabbits. After 0.5 or 1 month, the scaffolds were taken out and analysised by histological staining and immunofluorescence staining, the results of masson trichrome staining showed that the engineering vascular scaffold constructed by shape memory surface micropatterns (constructed with concentric circular microgrooves and radial straight microgrooves) could promote the formation of relatively homogenous vessel-like tissue with bands of collagen fibers. And from the immunofluorescence staining, we reaffirmed that the substrates with assembled circular microgrooves and the dynamic shape memory process could facilitate neovascularization.