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Brown adipose derived stem cells (BADSCs) have become a promising stem cell treatment candidate for myocardial infarction because of their efficiently spontaneous differentiation capacity towards cardiomyocytes . The lack of existing cell passage protocols motivates us to develop a neotype 3D cell expansion technique for BADSCs. In this study, “clickable” zwitterionic starch based hydrogels are developed using methacrylate modified sulfobetaine derived starch with dithiol-functionalized poly (ethylene glycol) as crosslinker via the “thiol-ene” Michael addition reaction . Moreover, CGRGDS peptide is immobilized into the hydrogel via a similar “clickable” approach. Their Young's moduli range from 22.28 to 74.81 kPa depending on the concentration of precursor solutions . Excellent anti-fouling property is also presented owing to the introduction of zwitterionic moieties. BADSCs are homogeneously encapsulated in the hydrogels and then routinely cultured for 10 days. Results suggest a capacious cell proliferation and the extent increases with either the decrease of mechanical strength or the introduction of CGRGDS. More excitingly, the cell “stemness” is well maintained during this period and the expanded cells released from the hydrogels well keep the efficiently spontaneous cardiomyogenic differentiation capacity. Therefore, it is suggested that zwitterionic starch based hydrogel is able for the expansion and “stemness ” maintenance of BADSCs.

The lack of living endothelial cells (ECs) functional layer is one of the major reasons which account for thrombosis of synthetic vascular vessels. To overcome this obstacle, we employed ZNF580 gene complexed with biodegradable microparticles (MPs) to promote the rapid endothelialization by ECs. In order to realize the controlled release of ZNF580 gene from MPs/gene complexes, a series of amphiphilic triblock copolymers with different degradation rate, namely, methoxy-poly(ethylene glycol)-block-poly(3(S)-methyl-morpholine-2,5-dione)-graft-polyethyleneimine (mPEG-b-PMMD-g-PEI), methoxy-poly(ethylene glycol)-block-poly(3(S)-methyl-morpholine-2,5-dione-co-lactide)-graft-polyethyleneimine (mPEG-b-P(MMD-co-LA)-g-PEI) and methoxy-poly(ethylene glycol)-block-poly(3(S)-methyl-morpholine-2,5-dione-co-lactide-co-glycolide)-graft-polyethyleneimine (mPEG-b-P(MMD-co-LA-co-GA)-g-PEI), were synthesized. Then, MPs were formed by self-assembly. The hydrophobic cores of these MPs were composed of PMMD, P(MMD-LA) or P(MMD-co-LA-co-GA) segments, and provided crosslinking points for numbers of PEG and short PEI chains to form a high hydrophilic and positive charged corona/shell structure. Based on their positive charged surface, MPs can compact pEGFP-ZNF580 into MPs/pEGFP-ZNF580 complexes. The cell transfection result demonstrated that pEGFP-ZNF580 could be transported efficiently into ECs by these complexes. The result of western blot showed that the relative ZNF580 protein level can increase to 35.74%-46.11% by the overexpression of ZNF580 gene. Furthermore, the release of pEGFP-ZNF580 could be sustained at least 25 days due to the controllable degradation ability of the hydrophobic MPs' core. The MPs and MPs/pEGFP-ZNF580 complexes showed low cytotoxicity because of the introduction of PEG chains and low molecular weight PEI on the surface of these MPs. Notably, at the low concentration (20 μg/mL), the MPs and their complexes were non-cytotoxicity. The rapid endothelialization was promoted significantly by the expression of pEGFP-ZNF580.

Natural bone is actually an inorganic/organic composite mainly make up of nano-hydroxyapatite (Ca(10)(PO(4))(6)(OH)(2), nHA) and collagen fibers. It is most important to form nHA/polymer composites in order to provide good biocompatibility and integration with bone tissue. In this work, nHA was formed in-situ on the surface of chitosan-gelatin (CG) network films in tris-buffer solution containing Ca(NO(3))(2)-Na(3)PO(4). The interaction between CG network film and nHA crystalline were studided using the diffuse reflectance FT-IR (ATR-FTIR), thermal analysis (TGA) and X-ray diffraction analysis (XRD), and the influence the nHA size factors, e.g. the ratio of chitosan (CS) and gelatin (Gel), concentration of calcium ions and reaction temperature, were elucidated by XRD and transmission electron microscope (TEM). Results suggested that carboxyl groups, CO and amino groups play crucial roles for HA formatting on the surface of CG network films and the average size of nHA crystalline decreasing with enhancing Gel content and increase with the increasing calcium and phosphate concentration, and when the reaction temperature below 50 degrees C the nHA crystalline size is almost fixedness (range from 17.2 to 19.2 nm) but when the temperature arrived at 70 degrees C it increase to 52.3 nm.