In Vitro Degradable Alginate Hydrogel Microcarriers

An unmet need for expansion of mesenchymal stem cells (MSC) in three dimensions was a synthetic mimic of the extracellular matrix (ECM) with user-controllable composition that would permit rapid recovery of viable cells under mild, non-enzymatic conditions. In this work, alginate was covalently crosslinked with cystamine in a condensation reaction of -COO- and -NH2 by means of carbodiimide-mediated activation. Thus, the hydrogels with disulfide bonds were prepared. These hydrogels were easily decomposed under physiological conditions using reductants such as L-cysteine by cleavage of disulfide crosslinkage to thiol groups.Chitosan and heparin were adsorbed to the hydrogel surface by the electrostatically driven layer-by-layer (LbL) self-assembly technique to improve the mechanical property and cytocompatibility. Furthermore, bioactive substances, such as fibronectin (FN) and basic fibroblast growth facter (bFGF) were immobilized onto the surface to promote cell adhesion and proliferation. The results indicated that hydrogel membrane exhibit excellent cytocompatibility, and the membrane modificated with FN and bFGF could further promote cell adhesion and proliferation. In addition, it was observed that the degradation process of the hydrogel was shown no obvious cytotoxicity.In vitro degradable alginate hydrogel-based microspheres were synthesized via water-in-oil (W/O) emulsion process. The morphology and diameter of the wet microspheres were examined by optical microscopy. The results indicated that the mean diameter and diameter distribution were determined by the concentration of alginate and the amount of dispersant. Macroporous alginate hydrogel microcarriers were prepared by freeze-drying technique. The SEM photographs showed that the pore size of the microcarrier was approximately 20~100μm. It should be noted that these carriers with organized pore structure have the ability to maintain the structural integrity on handling and culturing, hence resulting in the release of carried cells. The morphology and cytocompatibility of L929 cells cultured on the microcarriers were conducted by fluorescent“Live/Dead”screening and CCK-8 method. Results indicated that the cell spread well and populate rapidly on surfaces and pores of the microcarriers. All these findings suggest that the alginate hydrogel microcarriers were suitable to provide microenvironment for cell proliferation.