Agar Cell Diffusion, a Novel Technique to Evaluate Antimicrobial Potency of Nanoparticles in the Powder State
摘要
Almost all antimicrobial nanoparticles are commercially available as fine powders and are used in powdered form during the production of antimicrobial products. However, standard antimicrobial procedures are conducted on solutions or stable colloids. This means that nanoparticles are tested in a colloidal mono-disperse form, while in the production process, they are utilized as powders that contain aggregated structures. Consequently, existing standard procedures do not accurately reflect the true antimicrobial potency of nanopowders in antimicrobial products. Therefore, there is a need to modify the standard tests to enable antimicrobial testing on nanopowders, incorporating any dispersion or colloidization process. In the current study, the agar cell diffusion method was introduced as a novel approach to address this need. In this method, a well was created on a Muller-Hinton agar plate inoculated with bacteria. Antimicrobial nanopowders were mixed with molten agar and used to fill the well. An agar cell was formed, and after 18 h of incubation, the inhibition zone was measured. Using this method, the antimicrobial potency of Cu(OH)2 and ZnO nanopowders was evaluated. Cu(OH)2 nanopowder was synthesized through a plant-mediated precipitation reaction using Nigella sativa seed extract, while ZnO nanopowder was purchased commercially. It was found that the examined strain of Pseudomonas aeruginosa was resistant to both nanopowders. Cu(OH)2 nanopowder was more effective against Escherichia coli, with a growth inhibition zone of 15 ± 0 mm. Meanwhile, ZnO nanopowder was most effective against Staphylococcus aureus, showing a growth inhibition zone of 12.3 ± 0.58 mm.