PURPOSE: The photodynamic therapy is a technique by which the tumor cells are selectively sensitized to destruction by light of an appropriate wavelength. The aim of this work is to analyze the biological effectiveness of photochemical reactions induced by laser light in tumor cells exposed to photosensitizers. MATERIAL AND METHODS: The toxicity of the 2 photosensitizers zinc phthalocyanine (ZnPC) and meso-tetrahydroxyphenylchlorine (m-THPC) as well as the biological effect of the combination of sensitizers with laser light were tested in vitro by means of a colony forming assay. In addition, the influence on the photodynamic reaction of a previous exposure of the tumor cells to ionizing radiation has been tested. RESULTS: For both sensitizers doses of 5 micrograms per milliliter of culture medium showed low toxicity, i.e. the survival of the treated cells exceeded 90%. For laser treatments the dose permitting 90% survival was determined to be around 10 J/cm2. With these doses, the combined application of photosensitizers and laser light proved to be very effective and resulted in a nearly complete reduction of survival. As expected, irradiation of the cells with doses of 1 and 2 Gy of X-rays reduced the survival to 66 and 47%, respectively, compared to untreated controls. Cells surviving such treatment showed no changes either in the response to treatments with photosensitizers or to combined applications of photosensitizers and laser light. CONCLUSION: The effects of photodynamic treatment by ionizing radiation seem to be additive and independent of each other. So, our preliminary results are quite encouraging and point out the need of further detailed studies in view of the intended clinical application of this new kind of a local treatment.
PURPOSE: The photodynamic therapy is a technique by which the tumor cells are selectively sensitized to destruction by light of an appropriate wavelength. The aim of this work is to analyze the biological effectiveness of photochemical reactions induced by laser light in tumor cells exposed to photosensitizers. MATERIAL AND METHODS: The toxicity of the 2 photosensitizers zinc phthalocyanine (ZnPC) and meso-tetrahydroxyphenylchlorine (m-THPC) as well as the biological effect of the combination of sensitizers with laser light were tested in vitro by means of a colony forming assay. In addition, the influence on the photodynamic reaction of a previous exposure of the tumor cells to ionizing radiation has been tested. RESULTS: For both sensitizers doses of 5 micrograms per milliliter of culture medium showed low toxicity, i.e. the survival of the treated cells exceeded 90%. For laser treatments the dose permitting 90% survival was determined to be around 10 J/cm2. With these doses, the combined application of photosensitizers and laser light proved to be very effective and resulted in a nearly complete reduction of survival. As expected, irradiation of the cells with doses of 1 and 2 Gy of X-rays reduced the survival to 66 and 47%, respectively, compared to untreated controls. Cells surviving such treatment showed no changes either in the response to treatments with photosensitizers or to combined applications of photosensitizers and laser light. CONCLUSION: The effects of photodynamic treatment by ionizing radiation seem to be additive and independent of each other. So, our preliminary results are quite encouraging and point out the need of further detailed studies in view of the intended clinical application of this new kind of a local treatment.