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 α (TNFα) plays an important role and may be a potential target. In this study, we investigated the effect of Tnfα 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 TNFα (siTnfα) 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 siTnfα into the MSCs. CD-SMCC-siTnfα nanoformula also exhibited considerably high transfection efficiency and nearly no cytotoxicity, which is preferred over commercial polyethyleneimine. Interference of Tnfα by CD-SMCC-siTnfα markedly promoted the chondrogenesis of MSCs, as indicated by upregulating cartilage-specific markers. Furthermore, in vivo exploration indicated that CD-SMCC-siTnfα transfected MSCs accelerated cartilage regeneration. In conclusion, this study demonstrated that in combination with the novel CD-SMCC nanovector, targeting Tnfα may facilitate stem cell-based therapy of cartilage defects. Stem Cells Translational Medicine 2019;8:724&736.