Photothermal sensitization of amelanotic melanoma cells by Ni(II)-octabutoxy-naphthalocyanine

Incubation of B78H1 amelanotic melanoma cells with a potential photothermal sensitizer, namely, liposome-incorporated Ni(II)-octabutoxy-naphthalocyani ne (NiNc), induces an appreciable cellular accumulation of the naphthalocya nine, which is dependent on both the NiNc concentration and the incubation time. No detectable decrease in cell survival occurs upon red-light irradia tion (corresponding to the longest-wavelength absorption bands of NiNc) in a continuous-wave (c.w.) regime of the naphthalocyanine-loaded cells. On th e other hand, 850 nm irradiation with a Q-switched Ti:sapphire laser operat ing in a pulsed mode (30 ns pulses, 10 Hz, 200 mJ/pulse) induces an efficie nt cell death. Thus, ca. 98% decrease in cell survival is obtained upon 5 m in irradiation of cells that have been incubated for 48 h with 5.1 mu M NiN c. The efficiency of the photoprocess is strongly influenced by the NiNc ce ll incubation time prior to irradiation. Photothermal sensitization with Ni Nc appears to open new perspectives for therapeutic applications, as sugges ted by preliminary in vivo studies with C57/BL6 mice bearing a subcutaneous ly implanted amelanotic melanoma. (C)1999 Elsevier Science S.A. All rights reserved.