The importance of protoporphyrin IX efflux for ALA-PDT dosimetry

✍ Scribed by M.C. Milanetto; H. Imasato; J.R. Perussi

• Publisher: John Wiley and Sons
• Year: 2009
• Tongue: English
• Weight: 116 KB
• Volume: 6
• Category: Article
• ISSN: 1612-2011
• DOI: 10.1002/lapl.200910045

✦ Synopsis

One of the major advances in PDT is the use of 5aminolevulinic acid (ALA) to induce the production of an endogenous photosensitizer inside the cells using intracellular enzymatic pathways. ALA is the first intermediate in heme biosynthesis and a precursor of the protoporphyrin IX (PpIX). When activated by light, this efficient photosensitizer accumulated in the target cells can produce cytotoxicity. The aim of this study was to find the best conditions for cell killing using ALA to temporarily increase the concentration of PpIX in two cell lines. It was shown that a considerable efflux of synthesized PpIX occurs. Since this efflux is time-dependent, it is essential to know the optimum time for irradiation after ALA administration. So, the efflux of PpIX from the cells is an important parameter to be considered for ALA-PDT dosimetry. Survival index, % 60 40 20 0 80 100 Δt = 70 min Δt = 40 min Δt = 0 min Influence of the time interval (Δt) between the end of ALA incubation and the cell irradiation on the survival of HEp-2 (red) and VERO (green) cells. Incubation with ALA 1 mmol/L for 4 h. The time interval was 70 min for HEp-2 and 40 min for VERO