The significance of the nature of the photosensitizer for photodynamic therapy: quantitative and biological studies in the colon

Abstract

Summary Photodynamic therapy (PDT) depends on the interaction of light with an administered photosensitiser to produce a local cytotoxic effect. The most widely used photosensitiser is haematoporphyrin derivative (HpD), but newer photosensitisers such as aluminium sulphonated phthalocyanine (AlSPc) are promising. HpD (Barr et al., 1987a). However, this effect was not so evident and less predictable following HpD photosensitisation (Bown et al., 1986). Thus all quantitative studies were performed 1 h after photosensitisation.A continuous-wave argon pumped dye laser (Cooper Laseronics, CA, USA) with the output coupled to a 0.2 mm quartz laser fibre was set to deliver 100 mW. The laser was tuned to 630 nm for treatment of animals photosensitised with HpD, and 675 nm for those treated with AlSPc. A portion of colon on the right side had any faecal matter gently milked away. The laser fibre was inserted into the lumen of the bowel by puncturing the colonic wall. It was threaded along the colon to a convenient point and held in a clamp just touching the colonic wall. The laser was switched on for the time planned for the exposure. The colon was kept moist with occasional irrigation with 0.9% saline. The laser

Photodynamic therapy with WST09 (Tookad): Quantitative studies in normal colon and transplanted tumours

“…The final biological effects of PDT with WST09 on the normal rat colon are very similar to those described with other photosensitisers, particularly mTHPC, AlS2Pc and AlSPc and HpD 7, 8, 12. By varying the experimental conditions, it was possible to limit the effect to the mucosa, to produce full thickness necrosis involving the muscle layer (but with preservation of submucosal collagen) or to destroy all layers including the collagen.…”

Comparing and combining light dose fractionation and iron chelation to enhance experimental photodynamic therapy with aminolevulinic acid

“…The rest of the abdominal viscera were shielded from forward light scatter by a piece of opaque paper positioned so that it did not touch the colon, or affect its light distribution. This is a model that we have used many times successfully in the past [6,35]. The light fluence where the fiber touches the tissue is high (320 W/ cm 2 ) but no thermal effect was observed in the light only control group.…”

Photodynamic parameters in the chick chorioallantoic membrane (CAM) bioassay for topically applied photosensitizers

“…The present study is limited to four compounds: sulfonated chloro-aluminum phthalocyanine (AlPcS n ) [14], benzoporphyrin derivative monoacid ring A (BPD-MA) [15,16], lutetium texaphyrin (Lutex) [17][18][19], and aminolevulinic acid (ALA), a precursor of the endogenous sensitizer protoporphyrin IX (PpIX) [20]. In Table 1 Thursday we present some published results of the PDT efficiency, relative to Photofrin, of these selected sensitizers [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38].…”