Exosomes derived from mesenchymal stem cells (MSCs) have been studied as vital components of regenerative medicine. Typically, various isolation methods of exosomes from cell culture medium have been developed to increase the isolation yield of exosomes. Moreover, the exosome-depletion process of serum has been considered to result in clinically active and highly purified exosomes from the cell culture medium. Our aim was to compare isolation methods, ultracentrifuge (UC)-based conventional method, and tangential flow filtration (TFF) system-based method for separation with high yield, and the bioactivity of the exosome according to the purity of MSC-derived exosome was determined by the ratio of Fetal bovine serum (FBS)-derived exosome to MSC-derived exosome depending on exosome depletion processes of FBS. The TFF-based isolation yield of exosome derived from human umbilical cord MSC (UCMSC) increased two orders (92.5 times) compared to UC-based isolation method. Moreover, by optimizing the process of depleting FBS-derived exosome, the purity of UCMSC-derived exosome, evaluated using the expression level of MSC exosome surface marker (CD73), was about 15.6 times enhanced and the concentration of low-density lipoprotein-cholesterol (LDL-c), known as impurities resulting from FBS, proved to be negligibly detected. The wound healing and angiogenic effects of highly purified UCMSC-derived exosomes were improved about 23.1% and 71.4%, respectively, with human coronary artery endothelial cells (HCAEC). It suggests that the defined MSC exosome with high yield and purity could increase regenerative activity.

Allyl-amino thioxanthone derivatives as new visible-light photoinitiators for efficient free-radical, cationic and thiol–ene polymerizations.

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Current approaches of biomaterials for the repair of critical-sized bone defects still require immense effort to overcome numerous obstacles. The biodegradable polymer-based scaffolds have been required to expand further function for bone tissue engineering. Poly(lactic-co-glycolic) acid (PLGA) is one of the most common biopolymers owing to its biodegradability for tissue regenerations. However, there are major clinical challenges that the byproducts of the PLGA cause an acidic environment of implanting site. The critical processes in bone repair are osteogenesis, angiogenesis, and inhibition of excessive osteoclastogenesis. In this study, the porous PLGA (P) scaffold was combined with magnesium hydroxide (MH, M) and bone-extracellular matrix (bECM, E) to improve anti-inflammatory ability and osteoconductivity. Additionally, the bioactive polydeoxyribonucleotide (PDRN, P) was additionally incorporated in the existing PME scaffold. The prepared PMEP scaffold has pro-osteogenic and pro-angiogenic effects and inhibition of osteoclast due to the PDRN, which interacts with the adenosine A2A receptor agonist that up-regulates expression of vascular endothelial growth factor (VEGF) and down-regulates inflammatory cytokines. The PMEP scaffold has superior biological properties for human bone-marrow mesenchymal stem cells (hBMSCs) adhesion, proliferation, and osteogenic differentiation in vitro. Moreover, the gene expressions related to osteogenesis and angiogenesis of hBMSCs increased and the inflammatory factors decreased on the PMEP scaffold. In conclusion, it provides a promising strategy and clinical potential candidate for bone tissue regeneration and repairing bone defects.