BACKGROUNDWe assessed whether the CaNa2 EDTA could improve the accumulation of protoporphyrin IX (PpIX) and photosensitisation in HEp-2 cells as well as the depth of treatment of skin cancers on the topical 5-Aminolaevulinic acid (5-ALA) PDT.

METHODSHEp-2 cells were incubated with 5-ALA (0-1 mmol/L) and CaNa2EDTA (0-1 mmol/L) for 4 hours, intracellular protoporphyrin IX content was quantified by extraction, and cell viability was assessed by use of the methyl-tetrazolium (MTT) assay four hours after exposure to light. In comparison with the pictures before and after treatment, depth of treatment could be determined using a Acuson Sequioa 512 phase-array system in paired experiments.

RESULTSPpIX accumulation increased with increasing extracellular concentrations of ALA (0-1 mmol/L). Adding 1 mmol/L of CaNa2EDTA increased 30% PpIX accumulation over the same period of incubation in the concentration of 1 mmol/L ALA. Significant difference was observed between the 5-ALA alone group and 5-ALA combined CaNa2 EDTA group in the PpIX accumulation (P < 0.01). Cell viability after exposure to light decreased with adding CaNa2 EDTA, a statistical difference in a same fluence above 1.2 J/cm2 between two groups was demonstrated (P < 0.05, P < 0.01 respectively). Depth of treatment of skin cancers were increased in CaNa2 EDTA-treated group.

CONCLUSIONCaNa2 EDTA could improve the PpIX accumulation and photosensitisation in HEp-2 cells. Clinically, CaNa2 EDTA could increase the depth of treatment in the cutaneous cancers.