Arginine-loaded silica nanoparticles inhibit E. faecalis in root canals

Bacterial infection of the root canal system, especially by Enterococcus faecalis (E. faecalis), is the primary cause of root canal treatment failure, and intracanal medication has been proven to be an effective method for controlling root canal infection. Mesoporous silica nanoparticles (MSNs) with their sponge-like structure, tunable particle size, surface functionalization, and favorable biocompatibility offer promise for intracanal drug delivery. This study evaluated the antibacterial efficacy of an arginine-loaded MSN system (MSN@Arg) against E. faecalis, its effects on osteogenic differentiation in MC3T3-E1 cells, and its ability to control infection within the root canal system. The physicochemical properties and drug release profile of MSN@Arg were assessed using electron microscopy and other analytical techniques. Antibacterial activity was evaluated through bacterial culture assays. Alkaline phosphatase and Alizarin Red staining were performed to evaluate osteogenic differentiation. An E. faecalis-infected root canal model was established in extracted teeth, and the antibacterial efficacy of MSN@Arg, chlorhexidine (CHX), and calcium hydroxide was compared at 3, 7, 14, and 21 days after drug sealing. The synthesized MSNs (diameter < 100 nm) exhibited extensive distribution within dentinal tubules. MSN@Arg enabled sustained and stable release of arginine, inhibited E. faecalis in both planktonic and biofilm states, and promoted ALP expression and mineralized nodule formation in MC3T3-E1 cells, with high biocompatibility. MSN@Arg demonstrated greater antibacterial efficacy than calcium hydroxide on days 3 and 7, was comparable to CHX on day 14, and slightly more effective than CHX on day 21. Given its deep penetration into dentinal tubules and sustained drug release capacity, MSN@Arg represents a promising agent for root canal disinfection.