Antibacterial Efficacy Comparison of Electrolytic and Reductive Silver Nanoparticles Against Propionibacterium acnes

Background: The aim of this study was to develop an electrolysis system to produce silver nanoparticles free from toxic gases, as the most common reduction and electrolysis techniques produce nitrogen dioxide (NO₂) as a byproduct, which is harmful to human health. The new electrolysis system used two identical silver plate electrodes, replacing silver and carbon rods, and used water as the electrolyte instead of silver nitrate (AgNO₃) solution since AgNO₃ is the source of NO₂. Methods: The electrolytic silver nanoparticles (ESNs) produced by the new system were characterized and compared with reductive silver nanoparticles (RSNs). Using UV-Visible spectrophotometry, absorption peaks were found at 425 nm (ESN) and 437 nm (RSN). Using dynamic light scattering, the particle diameters were measured at 40.3 nm and 39.9 nm for ESNs at concentrations of 10 ppm and 30 ppm, respectively, and 74.0 nm and 74.6 nm for RSNs at concentrations of 10 ppm and 30 ppm, respectively. Antibacterial activity against Propionibacterium acnes (P. acnes) was assessed using the Kirby-Bauer method. Results: It was found that the efficacy of ESNs and RSNs was relatively lower than that of 5% chloramphenicol because it was measured in different concentration units (ESNs and RSNs in ppm and chloramphenicol in %). Using the calibration curve, the efficacy of 5% chloramphenicol was comparable to that of 0.005% ESN. It was also found that P. acnes developed a strong resistance to chloramphenicol and showed no resistance to ESNs. Conclusions: This finding underlines the tremendous potential of ESNs as a future antibiotic raw material.