The Cytotoxicity of OPA-Modified CdSe/ZnS Core/Shell Quantum Dots and Its Modulation by Silibinin in Human Skin Cells

Quantum dots (QDs) have emerged as alternative or complementary tools to organic fluorescent dyes currently used in bioimaging. QDs hold several advantages over conventional fluorescent dyes including greater photostability and a wider range of excitation/emission wavelengths. However, recent work suggests that QDs exert deleterious effects on cellular processes which could obscure bioassay results. This study examined the toxicity of octylamine-poly(acrylic acid) (OPA) modified CdSe/ZnS quantum dots (QDs) and a pharmacological means of preventing QD-induced cell death. Cell viability and the flow cytometry were used to access the toxicity of OPA-modified CdSe/ZnS QDs to human skin cells following a 24-h exposure. It is found that concentrations leading to a 50% reduction in malignant melanoma cell viability (TC50) for two OPA-QDs (QD545 and QD605) are 102.1, 57.3 nM in A375 cells and 67.2, 55.0 nM in A375. S2 cells, respectively. Moreover, QD545 and QD605 show low cytotoxic response in HaCaT keratinocyte cells with TC50 values of 818.2 nM and 162.0 nM, respectively. Silibinin, a natural product derived from milkweed thistle, is known for its powerful antioxidant and membrane stabilizing properties. Pretreatment of cells with silibinin, significantly reduced QD-induced cell death in A375 and A375-S2 cells. These findings suggest that QD cytotoxicity is sensitive to cell types and that pretreatment with antioxidants, such as the natural product silibinin, can modulate QD-induced cytotoxicity.