Tissue distribution of a new photosensitizer ATX-S10Na(II) and effect of a diode laser (670 nm) in photodynamic therapy

The aims of the present study were to analyse the quantitative tissue distribution of ATX-S10Na(II) and to investigate the maximal effect of a diode laser and the irradiation conditions required to obtain this effect in photodynamic therapy (PDT) with ATX-S10Na(II). Spectrofluorometry was used to obtain quantitative tissue distribution of ATX-S10Na(II) in Colon 26 carcinoma-bearing mice as a function of time following administration. Next, transplanted tumours of mice with or without ATX-S10Na(II) were treated with the diode laser under conditions in which power density and irradiation time were varied. Tumour tissue concentrations of ATX-S10Na(II) were higher than in all tissues at all intervals following administration. The uptake of ATX-S10Na(II) by most tissues was rapid, with maximal concentrations occurring 1 h after i.v. injection, and ATX-S10Na(II) was almost excreted within 24 h after administration. The maximal depth of necrosis induced by PDT in the treated tumour was 7.9 mm under conditions in which power density was 160 mW/cm2 and total dose was above 100 J/cm2. PDT with ATX-S10Na(II) and the diode laser is useful for the treatment of superficial cancers.