Dynamic control of photodynamic therapy (PDT) by FluoDerm
Since 1990, when 5-ALA was introduced as a topical photosensitizing agent - a pro-drug which is transformed into (PpIX) - Photodynamic Therapy (PDT) has been used for treatment of malignant or pre-malignant skin conditions such as actinic keratosis (AK).
If PpIX is present in high concentrations inside the skin cells, illumination of the skin surface with light of specific visible wavelengths results in formation of free oxygen radicals leading in turn to cell necrosis.
As malignant cells have a higher metabolism than normal cells, the PpIX concentration in these cells will increase faster than in normal cells, and a selective cell necrosis will be obtained.
By dynamically controlling the added fluorescence with the FluoDerm, and thereby the amount of transformed PpIX, the PDT light exposure can be started as soon as the PpIX level has reached the appropriate level. This will ensure higher efficacy of the treatment with minimum time consumption and a reduced risk of side effect.
Fig. 1: Fluorescence after A: 0.5, B: 1, C: 2 and
D: 3 hours appplication of 20% 5-ALA in cream
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