Exploration of photophysical and photochemical properties of Zinc phthalocyanine-loaded SDC/TPGS mixed micelles

Abstract

A novel mixed micelles was developed to improve the solubility of Zinc phthalocyanine (ZnPc). Sodium deoxycholate (SDC) and D-alpha tocopheryl polyethylene glycol succinate (TPGS) were utilized as micelles material, mainly based on the design that ZnPc was located inside the hydrophobic core of mixed micelles, which was formed by supramolecular self-assembly of SDC and TPGS. A series of ZnPc loaded mixed micelles containing different quality of SDC were prepared and characterized by means of their physicochemical properties, photodynamic activity, photostability, drug release and cell viability. These mixed micelles appeared spherical, short rod and long rod shape, respectively, with corresponding particle sizes of about 106 nm, 344 nm and 80 nm, respectively. Drug loading efficiencies were higher than 90%. The capacity of ZnPc loaded mixed micelles to produce singlet oxygen (1O2) by irradiation with 650 nm red laser was monitored using 1,3-diphenylisobenzofuran as a probe. The singlet oxygen quantum yields (ΦΔ) for ZnPc loaded mixed micelles were high to that of the standard (ZnPc in DMF), and three of mixed micelles displayed excellent ability to generate 1O2 (the value of ΦΔwere greater than 0.70). These mixed micelles were photostable in the timescale typically used in photodynamic therapy (PDT), and only a small photobleaching event was observed after 20 min of light irradiation. The in vitro drug release studies of ZnPc loaded mixed micelles demonstrated a sustained release profile. Phototoxicity experiments in A549 cells showed that mixed micelles had higher toxicity than that of free ZnPc with the same concentration. Thus, the mixed micelles developed in this work are a promising strategy to be employed in delivery of ZnPc in PDT.