Poster S4 - Photothermal Treatment of Infected Melanoma Using Silver Nanoparticles

Introduction: Melanoma has recently been discovered to harbor intracellular bacteria, which affects their migration and metabolism. Silver nanoparticles (AgNPs) are used clinically for their antimicrobial benefits, and they can be tailored for photothermal therapy (PTT). The present work evaluates AgNPs fabricated for PTT as a strategy to eliminate both melanoma cells and intracellular bacteria.

Materials and

Methods: AgNPs were made using the seed-mediated method. Human melanocytes (CRL-4059) and SK-Mel-3 and SK-Mel-28 melanoma cell lines were infected with Staphylococcus aureus (Xen 40). Cell proliferation and migration were measured with and without infection. Cell and bacteria viability were measured following incubation with AgNPs and exposure to 800 nm light (to generate heat).

Results, Conclusions, and Discussions: Results

AgNPs have a triangular shape, and average size of 105nm. Laser powers of 3 and 5W were applied to 10 and 25 µg/mL AgNPs for 60s and 36s, respectively, for laser fluency of 180J. Heat generating ability of 10 µg/mL concentration was roughly 30°C increase for both powers, and 25 µg/mL concentration saw a temperature increase of approximately 50°C for both powers. Cytotoxicity of 0, 10, 25, 50, 100, and 250 µg/mL AgNPs were calculated for both non-infected and infected cells. Infected CRL-4059 cells were more sensitive at concentrations below 100 µg/mL. Non-infected SK-Mel-3 cells saw greater reduction than infected SK-Mel-3 cells at all concentrations. All infected cells saw greater viability reduction than non-infected cell lines, with SK-Mel-3 having the largest reduction. Concentrations of 0, 10, 25, 50, 100, and 250 µg/mL were tested using PTT at 5W for 36s on SK-Mel-3, and infected cells were more resistant to PTT than non-infected. While maintaining fluency of 180J, different powers and application times were tested. Infected cells were more resistant across groups, with the 5W 36s group seeing the greatest viability reduction, and thus was used for all subsequent experiments. Scratch assays saw infected cells filling the created gap more rapidly than non-infected cells, regardless of cell line. Cell counts and colony forming units (CFUs)/cell were found after PTT, and regardless of the cell line, the resultant number of infected cells were larger than their non-infected counterparts. SK-Mel-28 saw the greatest reduction of CFUs/cell while CRL-4059 had the least. Cell regrowth of SK-Mel-3 after PTT was also evaluated using clonogenics, and non-infected were more susceptible to AgNPs alone. However, applying PTT mitigates the survival of infected cells. When PTT was applied, regrowth after 1 week was decreased for both non-infected and infected cell lines as concentration increased to 25 µg/mL.

Conclusion

AgNPs are more cytotoxic to melanoma cells when combined with PTT. Additionally, infected cells are more resistant to both AgNPs and hyperthermia alone, but this can be overcome by increasing the thermal dose.

Acknowledgements (Optional): Wake Forest University School of Medicine Department of Plastic and Reconstructive Surgery for funding