There is a large demand for research to be conducted on the effects of humic acids and sunlight on engineered nanoparticles. In this study TiO2 and ZnO nanoparticles were examined to see how various concentrations of terrestrial and Suwannee humic acids affected their cytotoxicity when present in light and dark conditions. Multiple experiments were performed in order to obtain accurate data that could be compared to in later studies. Experiments were conducted using spread plate counting, LC50 calculations, TEM imaging, and Zetasizer graphs and calculations. The quartz and pyrex test tubes were tested to see if there was any difference between them for conducting the nanotoxicity under light irradiations. Results showed no significant difference. TEM determined that the average particle size was 47-106 nm for ZnO and 17-64 nm for TiO2 nanoparticles. The LC50 values showed that ZnO was the most toxic under both light and dark conditions. The Zetasizer calculated the zeta potentials of S-TiO2 and ZnO at pH 7.5 as being -18 mV and -32 mV, respectively. The TEM images of TiO2 with E. coli and P. fluorescens exhibit nanoparticles surrounding the surface of each bacterium and penetrating each type of bacteria. Terrestrial and river humic acids exhibited significant effect on reducing the cytotoxicity of both TiO2 and ZnO in a dose-dependent pattern. In summary, the presences of the different concentrations of humic acids lead to the decreased cytotoxicity of ZnO and TiO2 nanoparticles to E. coli.Acknowledgement:  The study was supported in part by: (1) The NSF-REU program (National Science Foundation-Research Experiences for Undergraduates) with grant #CHE-1156111. (2) NSF-CREST program (National Science Foundation-Centers of Research Excellence in Science and Technology) with grant #HRD-0833178.

Influence of sunlight and humic acids on the cytotoxicity of engineered zinc oxide and titanium dioxide nanoparticles to Escherichia coli

247th National Meeting (2014)

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