**2.4 MTT assay**

The MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) test was used to investigate the cytotoxic effects of Ag NPs and Au NPs on A549 (lung) and HCT116 (colon) cancer cells. In a 96-well plate, the cell lines were plated at a density of 1 × 104 cells/well in DMEM/1% FBS. For 24 h, cells were incubated at 37°C in an environment of air and CO2 (95% + 5%). When the cells had reached around 80% confluence, they were treated with Ag NPs and Au NPs in various concentrations of 25, 50, 75, 100, and 125 M. MTT assay was used to determine cell vitality after 24 h. MTT solution was added to each cell in a volume of 20 L and incubated for 3–4 h. The formazan was then diffused in dimethyl sulfoxide (DMSO), and optical densities were measured on an ELISA plate reader at 550 nm. As a control, cells were grown

without nanoparticles. The ratio of mean optical density to the control was calculated after the measurements were repeated twice. The following calculation was used to calculate cell viability for each well: CV = optical density (OD) of treated well/OD value of nontreated control well) × 100%. The cytotoxicity of Ag NPs and Au NPs was compared to a positive control drug, Oxaliplatin (OXP).

### **2.5 Antibacterial test**

Antibacterial activities of Ag and Au NPs against Gram-negative (Acinetobacter *baumannii*) and Gram-positive (*E. coli*) bacteria were tested using the well diffusion method. Before the experiment, bacterial cultures were produced to 0.5McFarland standards. Pure bacterial cultures were subcultured on Luria-Bertani (LB) agar medium and swabbed onto individual plates in a uniform manner. The wells were filled with 10 mL, 20 mL, and 30 mL Ag NPs solutions, which were then left to diffuse and incubated for 24 h at 37°C. To examine the antibacterial activity, the diameter of the zone of inhibition was employed. For the sake of reproducibility, the experiments were repeated twice.
