Light has been the subject of medical treatments since the ancient Greeks.
Raab first prescribed photodynamic therapy (PDT) in 1900 by documenting the death of Paramecia with acridine and light, and skin cancer was treated with eosin and light in 1903.
Various chemicals have been examined in efforts to optimise the cytotoxic effect of PDT. Hauseman found that porphyrins, naturally occurring iron- or-magnesium-free respiratory pigments present in the protoplasm of plant and animal cells, promoted photochemically induced cell death.
Studies with the complex porphyrin mixture haematoporphyrin derivative (HPD), revealed that this sensitiser concentrates in tumors, and multiple HPD injections and light exposures were used to treat locally recurrent breast cancer.
Ensuing studies by Dougherty and others explored the use of PDT in the treatment of a wide variety of animal and human malignancies.
PDT is based on the fact that a basic photochemical reaction occurs when a sensitising drug is exposed to light in the presence of oxygen. Absorbed light energy converts the sensitiser to an excited state, which in turn interacts with molecular oxygen to form singlet oxygen or oxygen free radicals. Singlet oxygen is a powerful oxidising agent which damages plasma membranes and other subcellular organelles. PDT is of no value unless all three components of a photochemical reaction light, oxygen, and sensitiser are simultaneously present when treating disease.
Raab first prescribed photodynamic therapy (PDT) in 1900 by documenting the death of Paramecia with acridine and light, and skin cancer was treated with eosin and light in 1903.
Various chemicals have been examined in efforts to optimise the cytotoxic effect of PDT. Hauseman found that porphyrins, naturally occurring iron- or-magnesium-free respiratory pigments present in the protoplasm of plant and animal cells, promoted photochemically induced cell death.
Studies with the complex porphyrin mixture haematoporphyrin derivative (HPD), revealed that this sensitiser concentrates in tumors, and multiple HPD injections and light exposures were used to treat locally recurrent breast cancer.
Ensuing studies by Dougherty and others explored the use of PDT in the treatment of a wide variety of animal and human malignancies.
PDT is based on the fact that a basic photochemical reaction occurs when a sensitising drug is exposed to light in the presence of oxygen. Absorbed light energy converts the sensitiser to an excited state, which in turn interacts with molecular oxygen to form singlet oxygen or oxygen free radicals. Singlet oxygen is a powerful oxidising agent which damages plasma membranes and other subcellular organelles. PDT is of no value unless all three components of a photochemical reaction light, oxygen, and sensitiser are simultaneously present when treating disease.
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