In vivo photodynamic therapy with meso-tetra(m-hydroxyphenyl)chlorin (mTHPC): influence of light intensity and optimization of photodynamic efficiency

Hadjira Rezzoug; Ousama M. A'Amar; Muriel Barberi-Heyob; Jean-Louis Merlin; Francois H. Guillemin

doi:10.1117/12.260755

4 December 1996 In vivo photodynamic therapy with meso-tetra(m-hydroxyphenyl)chlorin (mTHPC): influence of light intensity and optimization of photodynamic efficiency

Hadjira Rezzoug, Ousama M. A'Amar, Muriel Barberi-Heyob, Jean-Louis Merlin, Francois H. Guillemin

Author Affiliations +

Proceedings Volume 2924, Photochemotherapy: Photodynamic Therapy and Other Modalities II; (1996) https://doi.org/10.1117/12.260755
Event: BiOS Europe '96, 1996, Vienna, Austria

Abstract

Photodynamic therapy (PDT) consists in administering a photosensitizer generating cytotoxic radical species when submitted to light irradiation. One of the difficulties encountered in PDT is to find a photosensitizer absorbing at a wavelength penetrating tissues deeply. Meso-tetra(m- hydroxyphenyl)chlorin(mTHPC) presents this characteristic since it is activated at 650 nm. The photodynamic efficiency of mTHPC (0.3 mg/kg) was evaluated 72 hrs after intraperitoneal injection in HT29 human tumor bearing mice. This interval has been determined by a biodistribution study using fluorescence spectroscopy and HPLC. Mice were irradiated at 650 nm, 10 J/cm² using a dye laser. The photodynamic efficiency was evaluated by two methods: tumor growth after photodynamic treatment and macroscopic measurement of necrosis depth after tumoral resection using in vivo staining procedure with Evans blue dye. The normalization of the tumor volume (V equals 1/6 pi D³) to the initial volume showed no significant difference of control and treated mice, no regression was observed. Secondly the necrosis depth was determined 24 hrs after irradiation using Evans blue which circulates in vessels not damaged by the treatment. Only tumors from treated animals presented measurable necrosis area, mostly localized in surface around the irradiated site with a mean depth of 3.0 plus or minus 0.3 mm. No prolonged tumoral regression was observed. Unexpectedly, the photodynamic activity was higher when using a low irradiance (32 mW/cm²) than when using a higher one (160 mW/cm²). These results were not related to intratumoral mTHPC photodestruction. Tumor eradication may occur either in tumors measuring less than 3 mm, with a small light intensity, or through fractionated irradiation.

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Hadjira Rezzoug, Ousama M. A'Amar, Muriel Barberi-Heyob, Jean-Louis Merlin, and Francois H. Guillemin "In vivo photodynamic therapy with meso-tetra(m-hydroxyphenyl)chlorin (mTHPC): influence of light intensity and optimization of photodynamic efficiency", Proc. SPIE 2924, Photochemotherapy: Photodynamic Therapy and Other Modalities II, (4 December 1996); https://doi.org/10.1117/12.260755

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