L-arginine-containing mesoporous silica nanoparticles embedded in dental adhesive (Arg@MSN@DAdh) for targeting cariogenic bacteria

Abstract

Dental caries is the major biofilm-mediated oral disease in the world. The main treatment to restore caries lesions consists of the use of adhesive resin composites due to their good properties. However, the progressive degradation of the adhesive in the medium term makes possible the proliferation of cariogenic bacteria allowing secondary caries to emerge. In this study, a dental adhesive incorporating a drug delivery system based on L-arginine-containing mesoporous silica nanoparticles (MSNs) was used to release this essential amino acid as a source of basicity to neutralize the harmful acidic conditions that mediate the development of dental secondary caries. The in vitro and bacterial culture experiments proved that L-arginine was released in a sustained way from MSNs and diffused out from the dental adhesive, effectively contributing to the reduction of the bacterial strains Streptococcus mutans and Lactobacillus casei. Furthermore, the mechanical and bonding properties of the dental adhesive did not change significantly after the incorporation of L-arginine-containing MSNs. These results are yielding glimmers of promise for the cost-effective prevention of secondary caries.

Keywords: Dental adhesive; Dental caries; Drug delivery systems; L-arginine; Mesoporous silica nanoparticles.

Fig. 1

Molecular structures of A) L-arginine (Arg) and B) the N-oleoyl-L-arginine DSDA

Fig. 2

Scheme of the synthesis of Arg@MSNs using N-oleoyl-L-arginine as DSDA

Fig. 3

Structural and textural characterization of Arg@MSNs. TEM micrograph (A), N₂ adsorption–desorption isotherm and pore size distribution (B), low-angle X-ray diffraction pattern (C) and thermogravimetric analysis (D)

Fig. 4

Release of the N-oleyl-L-arginine DSDA from the Arg@MSN nanoparticles

Fig. 5

Release of the DSDA of L-arginine from the experimental adhesives with concentrations of 0.5 wt% (black), 1 wt% (red) and 2 wt% (blue) Arg@MSNs

Fig. 6

Mean reduction percentage of RLUs with the ATP assay after 1 h of adhesive contact with the bacteria. n = 16/group (Mean values of RLUs control: S. mutans 2167; S. gordonii 2426; L. casei:2022.)

Fig. 7

Mean reduction percentage of RLUs with the ATP assay after 7 days of adhesive contact with the bacteria. n = 16/group. (The same letters indicate no differences between experimental adhesives for each bacterial strain (P < 0.05). Mean values of RLUs control: S. mutans 5524; S. gordonii 5246; L. casei: 6131)