Assessment of the Cytotoxicity of Nano Gallium Liquid Metal Droplets for Biomedical Applications

Gallium-based liquid metals (LMs) have emerged as novel materials for biomedical applications. Gallium (Ga) is considered significantly less toxic than other LMs, such as mercury. However, Ga droplets have not been thoroughly assessed for their cytotoxicity. Here, we report the concentration-dependent cytotoxic effects of Ga nano- and microdroplets on HaCaT cells, a human keratinocyte cell line. We found that Ga droplets demonstrated substantial cytotoxic effects at 1000 μg/mL after 24 h exposure, while lower concentrations such as 500 μg/mL indicated only a slight reduction in cell viability at longer exposure times. At higher concentrations, it was observed that the cells were unable to form confluent layers and the cytoplasmic membrane became damaged. The formation of a protein corona on the Ga droplets in cell media is also described, which will be an important consideration for future research on Ga droplets for bio-applications. Importantly, this work provides an indication of the concentration at which Ga droplets become damaging to human cells, which will be useful information for a wide range of researchers and regulatory bodies.