Bioconjugated Carbon Dots for Delivery of siTnfα to Enhance Chondrogenesis of Mesenchymal Stem Cells by Suppression of Inflammation

Although a promising strategy, the mesenchymal stem cell (MSC)-based therapy of cartilage defects is sometimes accompanied with chronic inflammation during the remodeling status, which may hinder cartilage regeneration. During this process, the inflammatory cytokine tumor necrosis factor alpha (TNF alpha) plays an important role and may be a potential target. In this study, we investigated the effect of Tnf alpha RNA interference by introducing a functional and highly safe carbon dot (CD)-SMCC nanovector synthesized by bioconjugation of CDs with a protein crosslinker, sulfosuccinimidyl-4-(N-maleimidomethyl) cyclohexane-1-carboxylate (sulfo-SMCC), as the vehicle of the silenced TNF alpha (siTnf alpha) on chondrogenesis of MSCs. The results showed that CD-SMCC displayed intense fluorescence with well-dispersed and positively charged properties, which favored effective binding and delivering of siTnf alpha into the MSCs. CD-SMCC-siTnf alpha nanoformula also exhibited considerably high transfection efficiency and nearly no cytotoxicity, which is preferred over commercial polyethyleneimine. Interference of Tnf alpha by CD-SMCC-siTnf alpha markedly promoted the chondrogenesis of MSCs, as indicated by upregulating cartilage-specific markers. Furthermore, in vivo exploration indicated that CD-SMCC-siTnf alpha transfected MSCs accelerated cartilage regeneration. In conclusion, this study demonstrated that in combination with the novel CD-SMCC nanovector, targeting Tnf alpha may facilitate stem cell-based therapy of cartilage defects. Stem Cells Translational Medicine 2019;8:724&736