Harnessing volcanic silica nanoparticles for antibacterial applications

Bacterial pollution is a threat to human health and life. Although there are many chemically synthesized antibacterial substances, their use is restricted owing to their hazardous nature to both human health and the environment. Hence, a safer alternative would be antibacterial substances of natural origin. Herein, we used the environmental resource, volcanic silica, to prepare silica nanostructures for antibacterial applications. The silica nanostructures were treated with nitric and sulfuric acids to harness them for antibacterial application. Raw as well as acid-treated silica nanostructures were tested for antibacterial activity against six bacterial strains, including gram-positive and gram-negative species. The raw silica nanostructures did not show any antibacterial activity against any of the tested bacteria, while the 50 mg/mL of acid-treated silica nanostructures showed considerable antibacterial activity, which was comparable to 10 mu g/mL of the antibiotic tetracycline. The antibacterial activity of the acid-treated silica nanostructures could be attributed to the possible reaction of silica with sulfuric acid to form solid silica sulfuric acid, an efficient catalyst. In water, this solid acid forms a hydrated proton, which turns the media highly acidic, thereby inhibiting the growth of the bacteria. Thus, sulfuric acid-treated nanoparticles derived from natural volcanic silica could be used as an effective antibacterial agent. Although this is the first study to harness natural silica for antibacterial applications, this study's findings could open a new horizon by harnessing different rocks as environmental sources for antibacterial applications. (c) 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).