Innovative Titanium Implants Coated with miR-21-Loaded Nanoparticle for Peri-Implantitis Prevention

Background/Objectives: Peri-implantitis is a chronic inflammatory condition affecting tissues surrounding dental implants and is characterized by progressive marginal bone loss that can ultimately lead to implant failure. Reduced vascularization and impaired immune clearance in peri-implant tissues contribute to persistent inflammation and limited therapeutic efficacy. MicroRNAs (miRNAs), particularly miR-21, have emerged as key regulators of inflammatory responses and bone remodeling. The objective of this study was to develop a bioactive dental implant coating capable of locally delivering miR-21 to modulate inflammation and promote peri-implant tissue regeneration, thereby preventing peri-implantitis. Methods: Cationic nanoparticles were synthesized using lecithin and low-molecular-weight polyethylenimine (PEI) as a non-viral delivery system for miR-21. Lecithin was employed to enhance biocompatibility, while PEI functionalization provided a positive surface charge to improve miRNA complexation and cellular uptake. The resulting lecithin–PEI nanoparticles (LEC–PEI NPs) were incorporated into a chitosan-based coating and applied to titanium implant surfaces to obtain a sustained miR-21–releasing system (miR21-implant). Transfection efficiency and biological activity were evaluated in human periodontal ligament fibroblasts (hPDLFs) and compared with a commercial transfection reagent (Lipofectamine). Release kinetics and long-term activity of miR-21 from the coating were also assessed. Results: MiR-21-loaded LEC–PEI nanoparticles demonstrated significantly higher transfection efficiency than Lipofectamine and retained marked biological activity in hPDLFs relevant to peri-implantitis prevention. The chitosan-based nanoparticle coating enabled controlled and sustained miR-21 release over time, supporting prolonged modulation of inflammatory and osteogenic signaling pathways involved in peri-implant tissue homeostasis. Conclusions: The miR21-implant system, based on lecithin–PEI nanoparticles incorporated into a chitosan coating, represents a promising therapeutic strategy for peri-implantitis prevention. By enabling sustained local delivery of miR-21, this approach has the potential to preserve peri-implant bone architecture, modulate chronic inflammation, and enhance the osseointegration of titanium dental implants.