Wavelength dependent photo-cytotoxicity to ovarian carcinoma cells using temoporfin loaded tetraether liposomes as efficient drug delivery system

Abstract

5,10,15,20-Tetrakis(3-hydroxyphenyl)chlorin (mTHPC; temoporfin) is one of the most potent second-generation photosensitizers available today for the treatment of a variety of clinical disorders and has a unique capability of being activated at different wavelengths. However, due to its highly lipophilic nature, poor solubility in the aqueous media and poor bioavailability limits its application in anticancer therapies. To overcome these potential issues, we developed three different liposomal formulations with mTHPC encapsulated in hydrophobic milieu thus increasing the bioavailability of the drug. The prepared formulations were characterized in terms of hydrodynamic diameter, surface charge, encapsulation efficiency, and stability studies. The mean size of the liposomes was found to be in the nanoscale range (about 100 nm) with zeta potential ranging from -6.0 to -13.7 mV. mTHPC loaded liposomes were also evaluated for morphology using atomic force microscopy (AFM) and cryo-transmission electron microscopy (cryo-TEM). Data obtained from the hemocompatibility experiments showed that these formulations were compatible with blood showing less than 10% hemolysis and coagulation time lower than 40 s. The results obtained from the single-cell gel electrophoresis assay also demonstrated no incidence of genotoxicity. Photodynamic destruction of SK-OV-3 cells using mTHPC loaded liposomes showed a dose-response relationship upon irradiation with two different wavelength lights (blue λ = 457 nm & red λ = 652 nm). A 10-fold pronounced effect was produced when liposomal formulations were irradiated at 652 nm as compared to 457 nm. This was also evaluated by the quantitative assessment of reactive oxygen production (ROS) using fluorescence microscopy. The qualitative assessment of PDT pre- and post-irradiation was visualized using confocal laser scanning microscopy (CLSM) which demonstrated an intense localization of mTHPC liposomes in the perinuclear region. Chick chorioallantoic membrane assay (CAM) was used as an alternative in-ovo model to demonstrate the localized destruction of tumor microvasculature. Overall, the prepared nanoformulation is a biocompatible, efficient and well characterized delivery system for mTHPC for the safe and effective PDT.

Keywords: Atomic force microscopy; Chorioallantoic membrane; Comet; Cryo-TEM; Hemocompatibility; Photodynamic therapy; ROS.