Fig. 6

Reduction of hydrogen peroxide by over-expression of catalase catalase attenuates Ag⁺ but not AgNP mediated cell death. A Catalase expression was determined by western blot in parental SUM159, SUM159^Cat (-)Dox, and SUM159^Cat (⁺)Dox cells. B SUM159^Cat cells cultured with or without doxycycline were incubated with PBS containing PO1 and fluorescence was measured using confocal microscopy. C, D SUM159^Cat cells cultured with or without doxycycline were exposed to increasing concentrations of C AgNPs or E Ag⁺ for 72 h. Cell viability was quantified by MTT assay. IC₅₀’s were calculated for D AgNPs or F Ag⁺ using GraphPad prism. Data used to calculate IC50s were obtained from 6 technical replicates and 3 independent experiments (biological replicates). Statistical analysis was performed by Students T-test. Statistical differences are indicated (*p < 0.05). G, H Long-term proliferative potential was assessed via clonogenic assay after 24 h exposure to G AgNPs or H Ag⁺ in SUM159^Cat cells cultured with or without doxycycline. Data are presented as relative surviving fraction based upon clonogenic growth normalized to plating efficiency. Statistical analysis was performed by two-way ANOVA followed by post-hoc Tukey Test. Statistical differences are indicated (*p < 0.05)