Optimization of photodynamic therapy using negative pressure
Priscila Fernanda Campos Menezes1, Michelle Barreto Requena, Vanderlei Salvador Bagnato
1Instituto de Física de São Carlos (IFSC), University of São Paulo (USP) , São Carlos - SP, Brazil .
Objective:
The goal of this study is to demonstrate an alternative procedure to perform topical photodynamic therapy (PDT). Here, we propose the combined use of negative pressure and a 5-Aminolevulinic acid (5-ALA) cream occlusion to increase protoporphyrin IX (PPIX) formation.
Background Data:
PDT using topical 5-ALA as a prodrug and precursor of PPIX has been used in the treatment and diagnosis of different types of cancer and skin diseases. The use of 5-ALA offers many advantages as a localized and non-systemic application, but it shows limitations in relation to skin penetration. Many authors have discussed the limitations of 5-ALA penetration through the skin. The skin penetration of 5-ALA can be optimized using mechanical devices associated with typical PDT procedure.
Methods:
For this study, 20% 5-ALA cream was applied to a 9 cm(2) area of skin, and an occlusive dressing was placed. The PPIX production was collected at the skin surface, using fluorescence spectroscopy and widefield fluorescence imaging, for 7 h, and after 24 h.
Results:
We observed that in the presence of negative pressure therapy, the PPIX production, distribution, and elimination are greater and faster than in the control group. The PPIX formation was ∼30% in deeper skin layers, quantified by fluorescence spectroscopy analysis, and ∼20% in surface skin layers, quantified by widefield fluorescence imaging analysis.
Conclusions:
Negative pressure induction can also help PDT application in the case of inefficient PPIX production. These results can be useful for optimizing the PDT.
