Thermal Ultra Short Photodynamic Therapy: Heating Fibroblasts During Sub–30-Minute Incubation of 5-Aminolevulinic Acid Increases Photodynamic Therapy–Induced Cell Death

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Actinic keratoses (AKs) prevalence was estimated at 39.5 million Americans in 2004, and the cost to treat AKs that year was approximately 1 billion dollars. Photodynamic therapy (PDT) is an FDA-approved therapy for the treatment of AK. Recent studies have focused on reducing PDT treatment time while maintaining efficacy.


To investigate the use of thermal modulation to improve the efficacy of ultra short aminolevulinic acid (ALA) incubation PDT.


Human dermal fibroblasts (HDFs) were incubated for 10, 15, or 20 minutes with 0.5-mM ALA at various temperatures (21, 24, 27, 30, 33, 36, 39, and 42°C). After ALA incubation, samples were treated for 1,000 seconds with blue light (417 ± 5 nm) resulting in a fluence of 10 J/cm2. Samples were collected and stained for apoptosis/necrosis with annexin-V and 7-aminoactinomycin D (7-AAD), then analyzed by flow cytometry.


Human dermal fibroblast treated with 10-minute ALA-PDT had no statistically significant changes in apoptosis at all temperatures. Human dermal fibroblast treated with 15- or 20-minute ALA-PDT had statistically significant increases in apoptosis at 39 and 42°C (p < .05).


These results suggest the use of thermal modulation may improve ultra short ALA incubation PDT efficacy.

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