Melanoma remains a major public health concern that is highly resistant to standard therapeutic approaches.
Photodynamic therapy (
PDT) is an underutilised
cancer therapy with an increased potency and negligible side effects, and it is non-invasive compared to traditional treatment modalities. Three-dimensional multicellular tumour spheroids (MCTS) closely resemble in vivo avascular tumour features, allowing for the more efficient and precise screening of novel
anticancer agents with various treatment combinations. In this study, we utilised A375 human
melanoma spheroids to screen the phototoxic effect of
zinc phthalocyanine tetrasulfonate (
ZnPcS4) conjugated to
gold nanoparticles (AuNP). The
nanoconjugate was synthesised and characterised using ultraviolet-visible spectroscopy, a high-resolution transmission electron microscope (TEM), dynamic light scattering (DLS), and zeta potential (ZP). The
phototoxicity of the
nanoconjugate was tested on the A375 MCTS using
PDT at a fluency of 10 J/cm2. After 24 h, the cellular responses were evaluated via microscopy, an MTT viability assay, an
ATP luminescence assay, and cell death induction using
annexin propidium iodide. The MTT viability assay demonstrated that the photoactivated
ZnPcS4, at a concentration of 12.73 µM, caused an approximately 50% reduction in the cell viability of the spheroids. When conjugated to AuNPs, the latter significantly increased the cellular uptake and cytotoxicity in the
melanoma spheroids via the induction of apoptosis. This novel
Zinc Phthalocyanine Nanoconjugate shows promise as a more effective
PDT treatment modality.