Enhancing the photothermal properties of indocyanine green in melanoma spheroids via encapsulation in Span 80-containing lipid nanocapsules

Indocyanine green (ICG), a well-known photosensitiser, has shown potential in photothermal therapy (PTT) for cancer treatment, but its effectiveness is limited by poor skin penetration and rapid clearance. To address this, lipid nanocapsules (LNCs) were used as nanocarriers to enhance ICG's cellular uptake and photothermal (PT) performance in melanoma cells. Utilising our recently developed Span 80-modified LNCs (LNC100-S8) with high biocompatibility and enhanced cellular uptake in B16F10 melanoma cells, ICG was loaded into LNC100-S8 using the phase inversion temperature method. The results showed that ICG encapsulation at 4.5 mg/mL maintained small LNC sizes (95-105 nm). Moreover, the heating capacity of ICG in LNCs was approximately 1.5 times higher than free ICG, achieving temperature increases over 10 °C post-irradiation. In cell cancer monolayers, LNC100-S8 enhanced ICG uptake by 1.5 times compared to free ICG and reduced cell viability to 50 % following 808 nm laser irradiation. More promisingly, ICG-LNC100-S8 combined with laser irradiation significantly reduced three-dimensional B16F10 spheroids size up to 11 days post-treatment compared to free ICG. Overall, our findings validate LNC100-S8, as promising nanocarriers for enhancing ICG-based PTT, supporting their potential applications in vivo to treat melanoma and other skin cancers.