Silver ion toxicity in commercial colloidal silver: molecular insights from high-content imaging in Huh-7 cells

Colloidal silver is marketed as a dietary supplement, despite lacking essential mineral properties, scientific health benefits and potential toxicity. Therefore, we aimed to evaluate the effects of two commercially available colloidal silver formulations, Almacura (AL) and Prata Vida (PV), on the human hepatoma cell line Huh-7. We determined the IC₅₀ values for the AL formulation as 0.69 µg/mL (cell viability by MTT assay), 0.79 µg/mL (cell count via PI/Hoechst nuclear staining), and 0.93 µg/mL (membrane integrity by PI uptake assay). Similarly, the IC50 values for the PV formulation were 0.62 µg/mL (cell viability by MTT assay), 0.86 µg/mL (cell count via PI/Hoechst nuclear staining), and 1.02 µg/mL (membrane integrity by PI uptake assay). We also examined the contributions of the supernatant, enriched in Ag⁺ ions, and the pellet, mainly composed of AgNPs, to cytotoxicity. Using the MTT assay, we found IC50 values of 0.80 µg/mL for AL and 0.85 µg/mL for PV, indicating that the supernatant is the primary driver of the observed cytotoxicity. High-content imaging (HCI) was performed using the Live Cell Painting assay to evaluate dose-response effects, revealing that both formulations showed cellular changes at lower concentrations compared to MTT assays. In conclusion, this study raises important concerns regarding the safety of commercial colloidal silver, highlighting the need for regulatory standards that consider nanoparticle characteristics and their biological interactions.