Comparative study between the photodynamic ability of gold and silver nanoparticles in mediating cell death in breast and lung cancer cell lines

Cancer is one of the dreadest diseases once diagnosed and has severe impacts on health, social and economic global aspects. Nanomedicine is considered an emerging approach for early cancer diagnosis and treatment. The multifunctional effects of silver and gold nanoparticles (Ag and Au NPs) have rendered them to be potent candidates for biomedical applications. The current work presents a comparative study between Au NPs and Ag NPs as possible potent photosensitizers (PS) in photodynamic therapy (PDT). Transmission electron microscopy (TEM) was used to identify and characterize the shape, size, and cellular localization of Au NPs; the absorption properties of Au NPs were determined using ultraviolet-visible spectroscopy (UV-Vis) and zeta potential was used to identify surface charge. Inverted light microscopy (LM), Trypan blue exclusion assay, adenosine triphosphate luminescence (ATP), and lactate dehydrogenase membrane integrity assays (LDH) were used for investigating the photodynamic ability of these nanostructures on breast (MCF-7) and lung (A549) cancer cell lines. Flow cytometry using Annexin V and propidium iodide (PI) dyes was used to determine the cell death pathway induced. The average size of the synthesized Au NPs was 50 nm, having an absorption peak at 540 nm with -7.85 mV surface net charge. MCF-7 and A549 cells were able to absorb the Au NPs. The latter, when irradiated with laser light in the phototherapeutic window, promoted cytotoxicity and a significant reduction in cell viability and proliferation were observed. The photodynamic activity that was observed in both cancer cell lines was found to be less eminent than that observed in case of the Ag NPs when compared to Au NPs. The present study is the first that compares the photodynamic ability of two different nanoparticles, silver and gold, as photosensitizers without any further functionalization. This study extends the possibilities of using such nanostructures in PDT within the therapeutic window wavelength, yet through the conjugation of Au NPs with other photosensitizers to synergize its effect.