Synthesis and Characterization of Fluoridated Silver Nanoparticles and Its Potential as a Non-staining Anti-caries Agent

Objectives: 1)To synthesize a solution with silver nanoparticles and sodium fluoride (NaF) with no staining on human dentine, 2) to investigate its antibacterial effect against Streptococcus mutans.
Methods: A solution of polyethylene glycol-coated silver nanoparticles (PEG-AgNPs) with sodium fluoride were developed via reduction of silver acetate with thiolatedpolyethylene glycol and addition of 2.5% NaF. The fluoridated PEG-AgNPs were characterized using transmission electron microscopy (TEM). The fluoridated PEG-AgNPs treated dentine blocks were measured with CIELAB system and the change of the shade (ΔE) was calculated. The cytotoxicity of PEG-AgNPs was assessed using half maximal inhibitory concentration (IC₅₀) against human gingival fibroblasts (HGF-1). The antibacterial properties of PEG-AgNPs and fluoridated PEG-AgNPs were evaluated with minimum inhibitory concentration required to inhibit 50% growth of Streptococcus mutans(MIC₅₀) and fractional inhibitory concentration indexes (FICI).
Results: The TEM analysis revealed the formation of monodispersed spherical fluoridated PEG-AgNPs with diameter at 2.60 ± 0.51 nm. Fluoridated PEG-AgNPs treated dentine blocks yielded ΔE values at 2.8 to 8.5. PEG-AgNPs showed the IC₅₀ of HGF-1 at 42.36 ± 1.12 ppm. AgNO₃ is highly toxic towards HGF-1. Oppositely, NaF did not damage 50% growth of HGF-1 until 1,131 ppm. The MIC₅₀ of PEG-AgNPs against Streptococcus mutans was 21.16 ± 1.08 ppm. NaF had MIC₅₀ at 32.96 ± 2.86 ppm. AgNO₃ and SDF had similar value of MIC₅₀. The fractional inhibitory concentration indexes (FICI) of fluoridated PEG-AgNPs were found between 1.04 to 1.3.
Conclusions: A fluoridated PEG-AgNPs solution with no staining effect on dentine was developed. It has strong antibacterial effect against Streptococcus mutans.