Combination of cyclodextrin complexation and iontophoresis as a promising strategy for the cutaneous delivery of aluminum-chloride phthalocyanine in photodynamic therapy

Abstract

Topical application of aluminum-chloride phthalocyanine (AlClPc) is a challenge because of the drug's extremely low solubility, which prevents its absorption into deeper skin layers and causes molecule aggregation, reducing the photophysical effect. The goal of this study was to obtain a formulation applied in a certain condition that would allow homogeneous accumulation of AlClPc in cutaneous tissues, meaning a safer and non-invasive topical treatment for skin tumors based on photodynamic therapy. We first prepared and characterized AlClPc complexes with cyclodextrin to increase the photosensitizing agent solubility. The inclusion complex of AlClPc with hydroxypropyl-β-cyclodextrin (HP-βCD) amplified its loading dose in aqueous medium and maintained its photosensitizing properties in terms of reactive oxygen species production. Assays to determine the complex's in vitro cytotoxicity against murine melanoma skin cancer cells showed that when irradiated, the complex significantly reduced cell viability, whereas the absence of irradiation did not affect cell viability. Three physical techniques for permeation enhancement (i.e., tape-stripping abrasion, microneedle pretreatment and iontophoresis) were then evaluated. When applied in impaired skin, the complex could not increase drug penetration. The skin penetration of AlClPc, however, increased 2.3-fold following iontophoresis application in a shorter period compared to passive permeation. Therefore, these results suggest the administration of complexed AlClPc mediated by iontophoresis, followed by application of photodynamic therapy, might be an effective and non-invasive alternative for topical treatment of cutaneous tumors.