In Vitro Degradable Alginate Hydrogel Microcarriers

The number of stem cells is limited, which can not satisfy the need of clinicalapplication, so how to expand stem cells in large scale is a problem to study. In recentyears, microcarrier culture technique has been widely applied for the expansion ofanimal cells, it also provides a reference for expansion of stem cells. In this thesis，akind of covalently cross-linked alginate hydrogel microcarrier with disulfide bondswas prepared via water-in-oil (W/O) emulsion process. These hydrogel microcarrierswere easily decomposed under physiological conditions in the presence of reductantssuch as L-cysteine by cleavage of disulfide crosslinkage to thiol groups.Chitosan and heparin were adsorbed to the surface of microcarrier by theelectrostatically driven layer-by-layer (LbL) self-assembly technique to improve themechanical property and cytocompatibility. Furthermore, bioactive substances such asfibronectin (FN) and basic fibroblast growth factor (bFGF) were immobilized onto thesurface of the microcarriers to promote cell adhesion and proliferation. The results ofXPS and ATR-FTIR revealed that the surfaces of microcarriers were entirely coveredby chitosan, whereas merely small amount of heparin was adsorbed to themicrocarrier surfaces.The human hepatocellular carcinoma cell line HepG2was cultured in themicrocarriers to evaluate the cell proliferation, albumin secretion and microcarriercytotoxicity. The results indicated that the alginate hydrogel micocarriers modifiedwith chitosan/fibronectin and modified with chitosan/heparin/bFGF exhibited bettercell adhesion and cell proliferation ability, and the maximum number of living cells inthe microcarriers was almost the same with the commercial Cultispher-Smicrocarriers. The albumin secretion capacity of the HepG2cells cultured in theprepared microcarriers also achieved the commercial microcarriers’ level with lowercytotoxicity. All these findings suggest that the alginate hydrogel microcarriers weresuitable to provide microenvironment for cell proliferation and expansion.