Purpose: VicR is the essential response regulator related to the synthesis of exopolysaccharide (EPS) – one of the main cariogenic factors of S. mutans . An antisense vicR RNA (ASvicR ) could bind to vicR mRNA, hindering the transcription and translation of the vicR gene. We had constructed a recombinant plasmid containing the ASvicR sequence (plasmid-ASvicR ) and proved that it could reduce EPS synthesis, biofilm formation, and cariogenicity. However, the recombinant plasmids are supposed to be protected from enzymatic degradation and possess higher transformation efficiency. The principal objective of the present research was to construct an appropriate vector that can carry and protect the plasmid-ASvicR and investigate the effects of the carried plasmids on the cariogenicity of the S. mutans .
Methods: Aminated dendritic mesoporous silica nanoparticles (DMSNs-NH₂) were synthesized and characterized. The ability of DMSNs-NH₂ to carry and preserve the plasmid-ASvicR (DMSNs-NH₂-ASvicR ) was proved by the loading curve, agarose electrophoresis, DNase I digestion assays, and energy-dispersive spectrometry (EDS) mapping. Transformation assays demonstrated whether the plasmid could enter S. mutans . The effect of DMSNs-NH₂-ASvicR on the 12-hour and 24-hour biofilms of S. mutans was evaluated by biofilm formation experiments and quantitative reverse transcription polymerase chain reaction (qRT-PCR). The cytotoxicity of DMSNs-NH₂-ASvicR was assessed by CCK-8 and live/dead staining assays. The regulation of DMSNs-NH₂-ASvicR on the cariogenicity of S. mutans was also evaluated in vivo.
Results: DMSNs-NH₂ could load approximately 92% of plasmid-ASvicR at a mass ratio of 80 and protect most of plasmid-ASvicR from degradation by DNase I. The plasmid-ASvicR loaded on DMSNs-NH₂ could be transformed into S. mutans , which down-regulated the expression of the vicR gene, reducing EPS synthesis and biofilm organization of S. mutans . DMSNs-NH₂-ASvicR exhibited favorable biocompatibility, laying a foundation for its subsequent biomedical application. In addition, DMSNs-NH₂-ASvicR led to decreased caries in vivo.
Conclusion: DMSNs-NH₂ is a suitable vector of plasmid-ASvicR , and DMSNs-NH₂-ASvicR can inhibit biofilm formation, reducing the cariogenicity of S. mutans . These findings reveal that DMSNs-NH₂-ASvicR is a promising agent for preventing and treating dental caries.
Keywords: biofilm, exopolysaccharides, cariogenicity, mesoporous silica nanoparticles, Streptococcus mutans