Abstract
Nanoscale techniques for silver production may assist a resurgence of the medical use of silver. Traditional methods for chemically synthesizing colloidal silver (CS) may lead to the presence of toxic chemical species or chemical residues, which may inhibit the effectiveness of CS as an antibacterial agent. The purpose of this study was to investigate the bactericidal effects of CS at different concentrations against key oral pathogens and the cytotoxicity to adult human gingival and periodontal ligament fibroblasts (HGF and HPDL). Streptococcus mutans (ATCC25175), Aggregatibacter actinomycetemcomitans (ATCC29522), Porphyromonas gingivalis (W83, ATCC33277), Prevotella intermedia (ATCC25611) and Fusobacterium nucleatum (ATCC25586) were selected for the bactericidal tests. HGF and HPDL were obtained from the gingival tissue around extracted adult human teeth. Each genus of bacteria (initial concentration of 1×106 cell/ml) was incubated with CS for one minute at room temperature and their survival rates were measured by colony counting. Cytotoxicity of CS against HGF and HPDL was studied by cell proliferation assessment with Alamar Blue assay. The results demonstrated that a CS concentration of over 3 ppm had complete bactericidal effects on all tested bacteria. Compared with distilled water, CS concentration of 30 ppm showed significant inhibition of HGF and HPDL proliferation. However, such effects were not found when the concentration was lower than 20 ppm. The cytotoxicity (LD50) of CS determined by Alamar Blue assay was not found when the concentration was lower than 100 ppm. These results suggested that 20 ppm CS has ideal bactericidal effects against periodontal pathogens without significant cytotoxicity against host cells.
