Photodynamic therapy of human biliary cancer cell line using combination of phosphorus porphyrins and light emitting diode

Abstract

A series of phosphorus porphyrin complexes ([(RO)2P(tpp)]Cl, tpp = tetraphenylporphyrinato group, R = −(CH2CH2O)m(CH2)nH; 1a: m = 2, n = 2; 1b: m = 2, n = 4; 1c: m = 2, n = 6; 1d: m = 3, n = 6) were used for the photodynamic therapy (PDT) of human biliary cancer cell line (NOZ) when exposed to the irradiation of light emitting diodes (LEDs). A Dulbecco’s modified Eagle’s medium (DMEM) containing NOZ cells (2000 cell well−1) and 1 (0–100 nM) was introduced into a 96-well microplate and incubated for 24 h to accumulate 1 into the NOZ cells and to multiply the NOZ cells until the cell number reached 104 cells well−1. After replacing the DMEM medium containing 1 with a fresh DMEM medium without 1, the plates were irradiated for 30 min at 610 nm. After incubation was performed for 24 h in dark conditions, the cell viability of the NOZ cells was determined using the MTT assay. The half maximum inhibitory concentrations 50 (IC50) of 1a–1d were found to be in the range of 33.7–58.7 nM for NOZ. These IC50 values for the NOZ were one hundredth the IC50 value (7.57 μM) for mono-l-aspartyl chlorin e6 (laserphyrin®). Thus, it was found that the PDT activity of 1a–1d was much higher than the mono-l-aspartyl chlorin e6. Similarly, IC50 vales of 1a–1d for HeLa cells were found to be 27.8–52.5 nM. This showed that 1a–1d had high photodynamic activity in cancer cells. At the same time, it was speculated that an LED is a useful light source for deactivating the cancer cells because it can excite the sensitizers with peak width in their absorption spectra using the light of the specified wave length with band width of 10–20 nm; LEDs provide a homogeneous light distribution for the target cells.