Antimicrobial and physico-mechanical properties of a universal adhesive loaded with L-arginine-containing mesoporous silica nanoparticles (ArgC18@MSNs).

Objectives: To evaluate the effect of adding L-arginine-containing mesoporous silica nanoparticles (ArgC18@MSNs) to a commercial universal adhesive for anti-caries purposes, focusing on antimicrobial/physico-mechanical properties.

Methods: ArgC18@MSNs were synthesized using N-oleoyl-L-arginine as a drug-structure-directing agent and characterized by TEM, N adsorption-desorption, FTIR, XRD, TGA, and DLS. Drug release was monitored by UV-Vis for 7 days. Nanoparticles (2 wt% and 5 wt%) were incorporated into a universal adhesive and its original version served as control. Antimicrobial activity against a dental plaque-derived polymicrobial suspension was assessed by adenosine triphosphate quantification (ATP; adhered/planktonic microorganisms after 4/6 weeks) and confocal laser scanning microscopy assay (CLSM; intact adhered microorganisms after 3 weeks). Physico-mechanical properties analyzed included: degree of conversion (DC), Vickers microhardness (VHN), softening in ethanol (SE); water sorption (Wsp), solubility (Wsl), and mass change (MC) after 7 days and 4 months; ultimate tensile strength (UTS), flexural strength (FS), and elastic modulus (E) after 24 h and 4 months. Data were analyzed with Kruskal-Wallis/ANOVA (α=0.05).

Results: Spherical nanoparticles (126 nm) showed progressive drug release. 5 wt% ArgC18@MSNs adhesive reduced planktonic and intact adhered microorganisms (ATP/CLSM), with no impact on adhered microorganisms (ATP). Nanoparticles did not alter DC, VHN, MC, UTS, or FS; however, 2 wt% reduced Wsp, 5 wt% decreased SE and increased E and both lowered Wsl. Water storage increased Wsl, UTS, FS, and E, regardless of concentration.

Significance: Adding ArgC18@MSNs to a commercial universal adhesive at 5 wt% enhances its antimicrobial activity against a microbial consortium while preserving its physico-mechanical properties.