In vitro phototoxic effect of chloroaluminum phthalocyanine-loaded nanocapsules on human melanoma cell lines

MP Siqueira-Moura1,2, FL Primo1, EM Espreafico0,3, AC Tedesco1. 1University of São Paulo, Department of Chemistry FFCLRP 14040901, Brazil, 2University of São Paulo, Department of Pharmaceutical Science FCFRP 14040-903, Brazil, 3University of São Paulo, Department of Cellular and Molecular Biology and Pathogenic Bioagents FMRP 14049-900, Brazil

Photodynamic Therapy (PDT) against melanoma has found several limitations due to interference from endogenous chromophores (melanin) in the irradiation of this skin cancer. Photosensitizer agents which absorb at wavelengths above 650 nm may avoid melanin competition. In this context, the chloroaluminum phthalocyanine (ClAlPc) is a promissor photosensitizer with strong absorption between 670-680 nm. However, this molecule is extremely hydrophobic preventing its application in therapy. In order to overcome such problem, efforts have focused on development of drug delivery systems containing hydrophobic photosensitizers. Therefore, the aim of this study was to develop and to assess phototoxic effect of ClAlPc-loaded nanocapsules on WM1552C, WM278, and WM1617 human melanoma cell lines. Colloidal formulations containing ClAlPc were prepared by nanoprecipitation method. The phototoxicity assay was carried out following 3 h cell incubation with ClAlPc nanocapsules at 0.3 µg.ml-1, and the cells were irradiated by a laser (674 nm, 14 mW.cm-2) at light doses of 20, 50, 70, and 150 mJ.cm-2. After 24 h, the cell viability was verified by MTT colorimetric assay. To evaluate the toxicity in darkness condition, the cells were treated with nanocapsules at 0.3, 0.6, and 3.0 µg.ml-1 for 3 h without light. ClAlPc nanocapsules at 0.3 and 0.6 µg.ml-1 did not show chemical dark toxicity while at the highest concentration (3.0 µg.ml-1) used it could be observed a slightly cytotoxicity on WM1617 cells. Then, the lower concentration was chosen to be used throughout assay. The phototoxic effect of the ClAlPc nanocapsules showed to be light dose dependent. For all treated cells there were significant differences compared to the cell control (p < 0.05). WM1552C primary melanoma cells were more sensitive (p < 0.05) to phototoxic effect caused by ClAlPc nanocapsules (0.3 µg.ml-1) under light irradiation of 20 mJ.cm-2. Cell viability decreases with the increase of light dose ranging from 34.1% (±0.5) to 66.3% (±5.9) and from 6.4% (±0.7) to 7.9% (±0.6) for melanoma cells irradiated with 20 and 150 mJ.cm-2, respectively. Such results could be explained by the designed interaction between cells and nanodevices leading to a higher accumulation of ClAlPc into cells with better phototoxic effect due to higher reactive oxygen species generated. In summary, the nanoencapsulation of ClAlPc could enable the application of this hydrophobic photosensitizer using both low sensitizer drug and light doses in PDT against melanoma. Financial support: Grants from FAPESP (M.P.S.M. 07/58809-9) and CAPES.