Pharmacokinetic and phototherapeutic properties of axially substituted Si(IV)-tetradibenzobarreleno-octabutoxyphthalocyanines

Recent applications of phthalocyanines and naphthalocyanines for imaging and therapy

With high extinction coefficients and long absorption wavelengths in the near infrared region, phthalocyanines (Pcs) and naphthalocyanines (Ncs) are well-suited for optical imaging and phototherapies in biological tissues. Pcs and Ncs have been used in a range of theranostic applications. Peripheral and axial substituents can be introduced to Pcs and Ncs for chemical modification. Seamless metal chelation of Pcs or Ncs can expand their possibilities as medical therapeutic and imaging agents. Nanoparticulate approaches enable unique ways to deliver Pcs and Ncs to target tissues and improve their solubility, biocompatibility, biodistribution and stability. Herein, we highlight some recent Pc or Nc nanoscale systems for theranostic applications. WIREs Nanomed Nanobiotechnol 2017, 9:e1420. doi: 10.1002/wnan.1420 For further resources related to this article, please visit the WIREs website.

Mechanisms of porphyrinoid localization in tumors

The photosensitizing and pharmacokinetic properties of porphyrin-type compounds have been investigated for nearly a century. In the last decade, two porphyrin derivatives were approved in the U.S.A. and in several other countries for the photodynamic treatment of various lesions. An overview of the different mechanisms for preferential porphyrinoid localization in malignant tumors is presented herein. Several uptake pathways are possible for each photosensitizer, which are determined by its structure, mode of delivery and tumor type. Comparisons of the different mechanisms and correlations with the structure of the sensitizer are presented. Current delivery systems for porphyrin sensitizers are described, as well as recent strategies for enhancing their tumor-specificity, including conjugation to a carrier system that selectively targets a tumor-associated receptor or antigen.

Photodynamic activity of BAM-SiPc, an unsymmetrical bisamino silicon(IV) phthalocyanine, in tumour-bearing nude mice

BACKGROUND AND PURPOSE

Ever since the discovery of photodynamic therapy, there has been a continuous search for more potent photosensitizers. Towards that end, we have synthesized a number of novel phthalocyanine derivatives. The unsymmetrical bisamino silicon(IV) phthalocyanine BAM-SiPc is one of the most potent compounds. In in vitro cell culture, it exhibits high phototoxicity against a number of cancer cell lines.

EXPERIMENTAL APPROACH

In the present investigation, the in vivo effect of BAM-SiPc was studied in the tumour-bearing nude mice model. The biodistribution of BAM-SiPc was followed to evaluate its tumour selectivity and rate of clearance. The tumour volume in the hepatocarcinoma HepG2- and the colorectal adenocarcinoma HT29-bearing nude mice was measured after photodynamic therapy. The level of intrinsic toxicity induced was also investigated. Finally, the metabolism of BAM-SiPc in the 'normal' WRL68 liver cells and the hepatocarcinoma HepG2 cells was compared.

KEY RESULTS

The results not only showed significant tumour regression of HepG2 and growth inhibition of HT29 in the tumour-bearing nude mice, but also no apparent hepatic or cardiac injury with the protocol used. Histological analyses showed that apoptosis was induced in the solid tumour. BAM-SiPc could be metabolized by WRL68 liver cells but not by the hepatocarcinoma HepG2 cells. Unfortunately, BAM-SiPc did not show any specific targeting towards the tumour tissue.

CONCLUSIONS AND IMPLICATIONS

The efficiency of BAM-SiPc in inhibiting tumour growth makes it a good candidate for further evaluation. Enhancement of its uptake in tumour tissue by conjugation with biomolecules is currently under investigation.

Photodynamic therapy efficacy and tissue distribution of hypericin in a mouse P388 lymphoma tumor model

The phototherapeutic properties and tissue distribution of hypericin were investigated in DBA/2 mice bearing subcutaneously transplanted P388 lymphoma cells. The efficacy of the photodynamic therapy (PDT) 2 h after administration of hypericin (2, 5, or 20 mg/kg, i.p., 120 J/cm2, 595 nm) was substantially greater than the efficacy after a 24 h interval. PDT with Photofrin (5 mg/kg, i.p., 24-h interval, 120 J/cm2, 630 nm) showed no significant antitumoral effect. The hypericin uptake in some tissues was measured after administration of hypericin (5 or 20 mg/kg, i.p.) up to 168 h. A comparison of the distribution data and the PDT efficacy at various intervals suggests that the plasma concentration of hypericin, and to a lesser extent the tumor uptake, determines the tumor response to PDT with hypericin.

Cytosolic drug delivery using pH- and light-sensitive liposomes

A growing body of literature describes the development and applications of novel targeting and/or contents release triggering schemes to improve the therapeutic index of drugs encapsulated within liposomes. This review focuses on literature appearing between January 1995-December 1997 that report 1) antibody and receptor-mediated targeting approaches for improving drug localization and 2) acid, enzymatic, thermal or photochemical triggering processes that destabilize membranes and improve drug bioavailability via cytoplasmic delivery of liposomal contents.