Fluorescence evaluations for porphyrin formation during topical PDT using ALA and methyl-ALA mixtures in pig skin models.
BACKGROUND
Photodynamic Therapy (PDT) using Aminolevulinic acid (ALA) and derivative molecules as topical medication and as a precursor of protoporphyrin (PPIX), is limited due to low permeation through skin or efficiency in porphyrin production. This behavior affects the production and homogeneity of PPIX distribution on superficial skin and in the deeper skin layers. Many authors propose alternatives to solve this such as, modification in the ALA and derivativemolecules, modifying the chemical properties of emulsion external phase or incorporating a delivery system to the emulsion. The goal of this study is to discuss what proportion of ALA and Methyl aminolevulinate (MAL) on mixtures increase the amount and uniformity of PPIX formation at superficial skin by fluorescence evaluations.


METHODS
The study was conducted in vivo using a pig skin model. PPIX production was monitored using fluorescence spectroscopy and widefield fluorescence imaging on skin surface. 20% of ALA and MAL cream were done mixing the following proportions: ALA, M2 (80% ALA-20% MAL), M3 (60% ALA-40% MAL), M4 (50% ALA-MAL), M5 (40% ALA-60% MAL), M6 (20% ALA-80% MAL) and MAL.


RESULTS
Mixtures M3, M4, and M5 showed the most PPIX production on skin by widefield fluorescence imaging and fluorescence spectroscopy in 3h of incubation. These results suggest that 50% of ALA and MAL in the same mixture increase the PPIX production in amount, homogeneity and time production when compared to ALA and MAL. This has a positive impact on photodynamic damage optimizing the PDT treatment.
São Carlos Institute of Physics, University of São Paulo, PO Box 13560-970, Sao Carlos, SP, Brazil. Electronic address: alessandra.keiko@gmail.com.
Alessandra Keiko Lima
AK
Fujita
São Carlos Institute of Physics, University of São Paulo, PO Box 13560-970, Sao Carlos, SP, Brazil.
Phamilla Gracielli Sousa
PG
Rodrigues
São Carlos Institute of Physics, University of São Paulo, PO Box 13560-970, Sao Carlos, SP, Brazil.
Michelle Barreto
MB
Requena
Department of Veterinary Clinic and Surgery, Faculty of Agriculture and Veterinary Sciences, São Paulo State University (UNESP), Jaboticabal, SP, Brazil.
André
A
Escobar
Department of Veterinary Clinic and Surgery, Faculty of Agriculture and Veterinary Sciences, São Paulo State University (UNESP), Jaboticabal, SP, Brazil.
Rozana Wendler
RW
da Rocha
Department of Veterinary Clinic and Surgery, Faculty of Agriculture and Veterinary Sciences, São Paulo State University (UNESP), Jaboticabal, SP, Brazil.
Andrigo Barboza de
AB
Nardi
São Carlos Institute of Physics, University of São Paulo, PO Box 13560-970, Sao Carlos, SP, Brazil.
Cristina
C
Kurachi
São Carlos Institute of Physics, University of São Paulo, PO Box 13560-970, Sao Carlos, SP, Brazil.
Priscila Fernanda Campos
PF
de Menezes
São Carlos Institute of Physics, University of São Paulo, PO Box 13560-970, Sao Carlos, SP, Brazil.
Vanderlei S
VS
Bagnato
D000279:Administration, Cutaneous; D000818:Animals; D005456:Fluorescent Dyes / Q000008:administration & dosage / Q000493:pharmacokinetics; D006801:Humans; D007982:Levulinic Acids / Q000008:administration & dosage / Q000493:pharmacokinetics*; D008297:Male; D008856:Microscopy, Fluorescence / Q000379:methods*; D010778:Photochemotherapy / Q000379:methods; D017319:Photosensitizing Agents / Q000008:administration & dosage / Q000493:pharmacokinetics; D011524:Protoporphyrins / Q000378:metabolism*; D012867:Skin / Q000187:drug effects* / Q000378:metabolism*; D012869:Skin Absorption / Q000187:drug effects / Q000502:physiology*; D013552:Swine; D000622:Aminolevulinic Acid
D005456:Fluorescent Dyes; D007982:Levulinic Acids; D017319:Photosensitizing Agents; D011524:Protoporphyrins; D000622:Aminolevulinic Acid; C028025:protoporphyrin IX
5-ALA; 5-MAL; Fluorescence spectroscopy; Photodynamic therapy; Porphyrin; Widefield fluorescence imaging