BIOLOGICAL POTENTIAL OF SILICON 2,3-NAPHT HALOCYANINE DERIVATIVES AS SENSITIZERS FOR PHOTODYNAMIC THERAPY OF CANCER

Photodynamic therapy (PDT) of cancer relies upon the activation by red light of systemically administered photosensitisers which have been s electively retained in malignant tissues. Over the past years, several classes of dyes have been proposed as new photosensitisers. Among the m, naphthalocyanines offer a high absorption around 780 nm, where ligh t transmission into tissues is optimal. We therefore prepared four sil icon 2,3-naphthalocyanine derivatives substituted with two axial alkyl siloxy chains of increasing lengths. Their photobiological activity wa s determined in vitro in V-79 Chinese Hamster fibroblasts and in vivo in BALB/c mice bearing the EMT-6 tumour. In spite of the limited photo toxicity observed at the cellular level, in vivo, all dyes injected at 0.1 mu mol/kg, 24 h prior to PDT induced a complete tumour regression in at least 50% of mice. These data demonstrate the potential of sili con naphthalocyanines for the PDT of cancer.