In vitro antimicrobial activity of silver nanoparticles synthesis by lasers against teeth caries bacteria (S-mutans)

Antibacterial activity of silver nanoparticles prepared by lasers was examined on S.mutans bacteria. Using two different lasers mechanisms allows comparative studies to identify the most effective NP properties against S. mutans. Dual-laser synthesis may create synergistic effects, improving antibacterial performance compared to chemically synthesized Ag NPs. Fiber and Nd: YAG lasers were employed to synthesized silver nanoparticles with various size distribution by laser ablation and subsequently laser fragmentation. Pulsed laser ablation was employed in liquid by Nd: YAG with wavelength of 1.06 μm, power density of 2 × 10⁷ W/cm², pulse length of 10 ns and frequency of 10 Hz, then the synthesized Ag NPs was fragmented by fiber laser with the same wavelength, energy density of 12 J/cm², output power ranging from 0.3 to 20 W, pulse length of 127 ns and frequency of 30 kHz. Ultraviolet-visible (UV-Vis) spectroscopy, zeta potential, transmission electron microscopy (TEM), and atomic force microscopy (AFM) were used to examine the optical properties, stability, and morphological characteristics of produced silver nanoparticles (Ag NPs), respectively. The nanoparticles exhibited a spherical shape, with a size distribution indicating an average particle size of around 20 nm, according to the TEM finding. AFM analysis can determine the dimensions, size distribution, and surface roughness of silver nanoparticles. The mean size diameters and roughness rates of silver nanoparticles were observed to be 34 nm and 53.34 nm, as well as 16 nm and 21 nm for nanoparticles created by Nd: YAG and fiber lasers, respectively. It is found that smaller nanoparticle sizes with average diameter (20 nm) have greater influence on S.mutans teeth bacteria with maximum inhibition zone of (25 mm), while minimum effective concentration for these nanoparticles was 6 µg/ml. Moreover, silver nanoparticles have greater influence with aging time of two months due to the oxidation effect of active silver ions.