Abstract
The cytotoxicity and photocytotoxicity of methylene blue and several of its derivatives against two pigmented melanoma cell lines (SK-23 murine melanoma and SK-Mel 28 human melanoma) were investigated in culture. The derivatives were all more effective photosensitizers than methylene blue in both cell lines over a range of light doses (3.6-17.6 J cm−2). The increased activity correlated with increased cellular uptake and inherent photosensitizing efficacy. The photosensitizers also showed varying levels of interaction with the biopoly-mer melanin and although this appeared to affect uptake and activity, there was no direct correlation with toxicity.