Preparation Of Multifunctional Polyzwitterionic Hydrogels And Study Of Their Biological Performance

The excellent resistance of non-specific protein adsorption of polyzwitterionic materials results in their excellent resistant capacity of cell adhesion and the foreign-body reaction.In this study,versatile anti-adhesive hydrogels based on zwitterionic polymer or zwitterion modified natural polysaccharide were prepared and were used for the establishment of “blank platform” for the cell culture,in vitro expansion of stem cells and the development of high strength hydrogels to resist the foreign-body reaction.Based on the good biocompatibility of the natural starch and the excellent resistant property of non-specific protein adsorption of zwitterionic polymers,sulfobetaine etherifying reagent(DCAPS),zwitterion modified starch(SB-ST),acrylate modified SB-ST(SB-ST-A)and di-thiols functionalized polyethylene glycol(PEG-SH)were successively synthesized.The rapid crosslinking of SB-ST-A and PEG-SH could rapidly occur under the physiological conditions via the Michael-type “thiol-ene” nucleophilic addition “click” reaction and the S/P hydrogels were then formed in situ.After the characterization of the structure,their physical and chemical properties were also analyzed.The results suggest that S/P hydrogels were endowed with the excellent resistant ability of non-specific protein adsorption.Moreover,their gelation times,mechanical strength and swelling behaviors can be precisely regulated via changing the concentration of their precursor solutions and the ratio of functional groups.Providing abundant stem cells is the bottleneck problem in the field of cell therapy and the tissue engineering.The “stemness” maintenance during the expansion of stem cells is the key that affects the expansion efficiency.In this study,based on the special non-specific adsorption resistant property of zwitterionic polymers,“blank platform” for stem cell culture was established,which set brown adipose derived stem cells(BADSCs)from rats as model cells and S/P hydrogels as culture carriers.The relationship between the proliferation and “stemness” maintenance of BADSCs and the physical and chemical signals of the hydrogels,such as the composition,mechanical properties and RGD,etc.,was studied.The results of LIVE/DEAD staining,Alamar Blue assay and the immunofluorescence staining of Ki67 suggest the capacious cell proliferation.The expression of cardiac specific proteins c Tn T,?-actinin and GATA-4 demonstrates the restrain of spontaneous cardiac differentiation and the maintenance of the cardiac differentiative potentiality of cells.After hydrogel dissociation and cell release,expanded cells were tested by the flow cytometry and re-cultured on the tissue plates.The results suggest that expanded cells by the hydrogel can well maintain their original “stemness” and the capacity of cardiac differentiation.The prevailing materials for elastic cartilage alternatives in clinical practice cannot meet the needs of both mechanical strength and the resistant property of the foreign-body reaction.In this study,zwitterionic double-network(ZDN)hydrogels based on polycarboxybetaine and polysulfobetaine(p CB/p SB)were fabricated via the strategy of double-network hydrogels.The results of mechanical tests suggest that ZDN hydrogels have high mechanical strength and their mechanical response also bears an elastomeric behavior.The “lock” effect derived from the p SB second network not only strengthens the hydrogel but also prevents it from further swelling.ZDN hydrogels have excellent resistant capacity of non-specific protein adsorption,platelets adhesion and cells adhesion.After subcutaneous implantation in mice for 24 weeks,results of the histological staining suggest that the ZDN hydrogel did not trigger any foreign-body reaction and further collagenous fibrous capsule formation.