Cellular changes after photodynamic therapy on HEp-2 cells using the new ZnPcBr(8) phthalocyanine

This study investigated the effects of photodynamic therapy (PDT) by using the new photosensitizer Octal-Bromide Zinc Phthalocyanine (ZnPcBr(8)) on the nucleus, mitochondria, and cytoskeleton of HEp-2 cells.

PDT has been widely used as a therapeutic method for tumor-selective treatment and for other diseases. The therapy requires a photosensitizer, molecular oxygen, and visible light. Different studies have demonstrated that cellular organelles are potential targets for PDT, and the results are dependent on the photosensitizer used in the treatment. In this study, we investigated changes in the nucleus, mitochondria, and cytoskeleton of HEp-2 cells after PDT with the new ZnPcBr(8) phthalocyanine.

HEp-2 cells were cultivated under standard conditions, and then incubated with ZnPcBr(8) (1 micromol/L) for 1 h, and subsequently irradiated with a diode laser light (676 nm, 30 mW, 4.5 J/cm(2)). The cells were further cultured for 1 and 24 h at 37 degrees C in a 5% CO(2) and analyzed with fluorescence microscopy by using specific probes for the investigated organelles.

Before PDT, the photosensitizer showed a cytoplasmic diffuse distribution. After PDT, cells showed multinucleation, a punctuated mitochondrial distribution in the perinuclear region, and cellular retraction due to the cytoskeleton changes. All those cellular alterations disrupted homeostasis, contributing to cellular death, which is the major goal of PDT.

Based on our results and the characteristics of the new ZnPcBr(8) phthalocyanine, mechanistic and biochemical studies must be performed, but it is tempting to consider the chemical as a promising agent for PDT.