Cooperative Government-Industry Program Studies Electromagnetic Fields

Aluminium phthalocyanines substituted to different degrees with hydrophilic sulphonic acid and hydrophobic phthalimidomethyl groups were investigated in vivo as new agents for the photodynamic therapy of malignant tumours. Parameters studied included the photodynamic action on EMT-6 mammary tumours in BALB/c mice, the therapeutic window and the potential for direct cell killing, assayed via an in vivo/in vitro test. Although the efficiency of photoinactivation of the EMT-6 tumour increases by a factor of ten with reduction of the number of sulphonic acid groups from four to two, no further effect was seen with the addition of the hydrophobic phthalimidomethyl groups. Addition of the latter groups however increased the potential for direct cell killing by a factor of two and expanded the therapeutic window by a factor of four, thus improving the usefulness of the dye as a photosensitiser for the photodynamic therapy of cancer. Photodynamic therapy of cancer is a treatment which exploits the ability of certain dyes to absorb light and, via an excited state, interact with and cause damage to substrate molecules. If the dye, through differential rates of uptake or release by neoplastic tissue, as compared to normal tissue, concentrates in the tumour, activation with light of appropriate wavelengths can induce selective destruction of the malig