摘要：Scaffolds play a crucial role in tissue engineering. Biodegradable polymers with great processing flexibility are the predominant scaffolding materials. Synthetic biodegradable polymers with well-defined structure and without immunological concerns associated with naturally derived polymers are widely used in tissue engineering. The synthetic biodegradable polymers that are widely used in tissue engineering, including polyesters, polyanhydrides, polyphosphazenes, polyurethane, and poly(glycerol sebacate) are summarized in this article. New developments in conducting polymers, photoresponsive polymers, amino-acid-based polymers, enzymatically degradable polymers, and peptide-activated polymers are also discussed. In addition to chemical functionalization, the scaffold designs that mimic the nano and micro features of the extracellular matrix(ECM) are presented as well, and composite and nanocomposite scaffolds are also reviewed.

摘要：Regulation of osteogenic differentiation of bone mesenchymal stromal cells （BMSCs） plays a critical role in bone regeneration. As small non-coding RNAs, microRNAs （miRNAs） play an important role in stem cell differentiation through regulating target-mRNA expression. Unfortunately, highly efficient and safe delivery of miRNAs to BMSCs to regulate their osteogenic differentiation remains challenging. Conventional inorganic nanocrystals have shown increased toxicity owing to their larger size precluding renal clearance. Here, we developed novel, surface-engineered, ultra-small gold nanoparticles （USAuNPs, 〈10 nm） for use as highly efficient miR-5106-delivery systems to enable regulation of BMSC differentiation. We exploited the effects of AuNPs coated layer-by-layer with polyethylenimine （PEI） and liposomes （Lipo） to enhance miR-5106-delivery activity and subsequent BMSC differentiation capacity. The PEI- and Lipo-coated AuNPs （Au@PEI@Lipo） showed negligible cytotoxicity, good miRNA-5106-binding affinity, highly efficient delivery of miRNAs to BMSCs, and long-term miRNA expression （21 days）. Additionally, compared with commercial Lipofectamine 3000 and 25 kD PEI, the optimized Au@PEI@Lipo-miR-5106 nanocomplexes significantly enhanced BMSC differentiation into osteoblast-like cells through activation of the Sox9 transcription factor. Our findings reveal a promising strategy for the rational design of ultra-small inorganic nanoparticles as highly efficient miRNA-delivery platforms for tissue regeneration and disease therapy.