Photodynamic therapy (PDT) has emerged as an effective treatment modality for various malignant neoplasia
and diseases. In PDT, the photochemical interaction of photosensitizer (PS), light and molecular oxygen
produces singlet oxygen which can lead to tumour cell apoptosis, necrosis or autophagy. The success of PDT
is limited by the hydrophobic characteristic of the PS which hinders treatment administration and efficiency.
To circumvent this limitation, PS can be incorporated in nanostructured drug delivery systems such as gold
nanoparticles (AuNPs). In this study, we investigated the effectiveness of free zinc monocarboxyphenoxy
phthalocyanine (ZnMCPPc) and ZnMCPPc conjugated to AuNPs. Commercially purchased melanoma cancer
cells cultured as cell monolayers were used in this study. Changes in cellular response were evaluated using
cellular morphology, viability, proliferation and cytotoxicity. Untreated cells showed no changes in cellular
morphology, proliferation and cytotoxicity. However, photoactivated free ZnMCPPc and ZnMCPPc conjugated
to AuNPs showed changes in cellular morphology and a dose dependent decrease in cellular viability and
proliferation as well as an increase in cell membrane. ZnMCPPc conjugated to AuNPs showed an improved
efficiency in PDT as compared to free ZnMCPPc, which might be as a result of the vehicle effect of AuNPs.
Both PSs used in this study were effective in inducing cell death with ZnMCPPc conjugated to AuNPs
showing great potential as an effective PS for PDT.