A comparative study of a novel lipophilic phthalocyanine incorporated into nanoemulsion formulations: photophysics, size, solubility and thermodynamic stability

Abstract

Lipophilic tetrakis-(1-adamantylsulfanyl)phthalocyaninatozinc(II) was incorporated into two different nanoemulsion formulations with the former emulsion containing isopropyl myristate and Tween 80® and the latter glycerol monocaprylocaprate and Tween 80®. A two- to three-fold increase in water solubility was observed for the zinc phthalocyanine when incorporated into the nanoemulsions in comparison with that observed for water–DMSO (98:2). Morphological evaluation confirmed the formation of thermodynamically stable nanoemulsions in the nanosize range. The zinc phthalocyanine incorporated into the nanoemulsions was photo-stable over the irradiation times studied and both formulations displayed excellent singlet oxygen generation ability with high values of quantum yield of singlet oxygen production of up to 0.58. In addition, the viscosity of the nanoemulsions ranged from 30.2 to 323.9 cP. The foregoing formulations are considered to be strong candidates for parenteral administration of the zinc phthalocyanine in photodynamic therapy clinical trials.