Pheophorbide a-Conjugated pH-Sensitive Nanoparticle Vectors for Highly Efficient Photodynamic Therapy of Cancer

Self-aggregation of zinc bacteriochlorophyll-d analogs with an acylhydrazone moiety as the 13-keto-carbonyl alternative

Zinc methyl 3-hydroxymethyl-pyropheophorbides-a possessing an acylhydrazinylidene group at the 131-position were prepared by chemically modifying chlorophyll-a, which were models of bacteriochlorophyll-d as one of the light-harvesting pigments in photosynthetic green bacteria. Similar to the self-aggregation of natural bacteriochlorophyll-d in the antenna systems called chlorosomes, some of the synthetic models self-aggregated in an aqueous Triton X-100 solution to give red-shifted and broadened visible absorption bands. The newly appeared oligomeric bands were ascribable to the exciton coupling of the chlorin π-systems along the molecular y-axis, leading to intense circular dichroism bands in the red-shifted Qy and Soret regions. The self-aggregation in the aqueous micelle was dependent on the steric size of the terminal substituent at the 13-acylhydrazone moiety. An increase in the length of the oligomethylene chain as the terminal moved the red-shifted Qy maxima to shorter wavelengths, and branched alkyl and benzyl substitutes afforded no more self-aggregates to leave monomeric species in the hydrophobic environment inside the micelle. These results indicated that the acyl groups on the 13-hydrazone as the alternative of the natural 13-ketone regulated the chlorosome-like self-aggregation.

Self-Quenched Polysaccharide Nanoparticles with a Reactive Oxygen Species-Sensitive Cascade for Enhanced Photodynamic Therapy

Tumor microenvironment (TME)-responsive nanocarrier systems that keep the photosensitizer (PS) inactive during systemic circulation and then efficiently release or activate the PS in response to unique TME conditions have attracted much attention. Herein, we report novel TME-responsive, self-quenched polysaccharide nanoparticles (NPs) with a reactive oxygen species (ROS)-sensitive cascade. The PS, pheophorbide A (PhA), was conjugated to a water-soluble glycol chitosan (GC) through an ROS-sensitive thioketal (TK) linker. The amphiphilic GC-TK-PhA conjugates could arrange themselves into NPs and remain photoinactive due to their self-quenching effects. Upon reaching the ROS-rich hypoxic core of the tumor tissue, the NPs release the PS in a photoactive form by efficient, ROS-sensitive TK bond cleavage, thus generating potent phototoxic effects. Following near-infrared irradiation, the increase in locoregional ROS levels further accelerates the release and activation of PS. These cascade reactions caused a significant reduction in the tumor volume, demonstrating good antitumor potential.

Rational design of block copolymer self-assemblies in photodynamic therapy

Photodynamic therapy is a technique already used in ophthalmology or oncology. It is based on the local production of reactive oxygen species through an energy transfer from an excited photosensitizer to oxygen present in the biological tissue. This review first presents an update, mainly covering the last five years, regarding the block copolymers used as nanovectors for the delivery of the photosensitizer. In particular, we describe the chemical nature and structure of the block copolymers showing a very large range of existing systems, spanning from natural polymers such as proteins or polysaccharides to synthetic ones such as polyesters or polyacrylates. A second part focuses on important parameters for their design and the improvement of their efficiency. Finally, particular attention has been paid to the question of nanocarrier internalization and interaction with membranes (both biomimetic and cellular), and the importance of intracellular targeting has been addressed.

Functional Polymer Nanocarriers for Photodynamic Therapy

Photodynamic therapy (PDT) is an appealing therapeutic modality in management of some solid tumors and other diseases for its minimal invasion and non-systemic toxicity. However, the hydrophobicity and non-selectivity of the photosensitizers, inherent serious hypoxia of tumor tissues and limited penetration depth of light restrict PDT further applications in clinic. Functional polymer nanoparticles can be used as a nanocarrier for accurate PDT. Here, we elucidate the mechanism and application of PDT in cancer treatments, and then review some strategies to administer the biodistribution and activation of photosensitizers (PSs) to ameliorate or utilize the tumor hypoxic microenvironment to enhance the photodynamic therapy effect.

Co-delivery of doxorubicin and pheophorbide A by pluronic F127 micelles for chemo-photodynamic combination therapy of melanoma

In this work, doxorubicin (DOX)-loaded pheophorbide A (PheoA) modified Pluronic F127 (F127) micelles (DOX/F127-PheoA micelles) were developed for combined chemo-photodynamic therapy of melanoma.

Redox- and light-responsive alginate nanoparticles as effective drug carriers for combinational anticancer therapy

Nanoparticles have been extensively explored as effective means to deliver chemotherapeutic agents or photosensitizers for chemotherapy or photodynamic therapy (PDT) against cancer. In the present work, pheophorbide A (PheoA), a hydrophobic photosensitizer, was conjugated via a redox-sensitive disulfide linkage to alginate (PheoA-ALG). Anticancer agent, doxorubicin (DOX), was also loaded within the PheoA-ALG nanoparticles (DOX/PheoA-ALG NPs) and used as drug carriers for combinational antitumor treatment. The DOX/PheoA-ALG NPs were spherical in shape with a uniform diameter of approximately 210 nm. Redox-responsive drug releasing properties were shown by the DOX/PheoA-ALG NPs, with an accelerated amount of DOX and PheoA release observed in the presence of a high glutathione level (10 mM). Cellular uptake results showed that DOX/PheoA-ALG NPs were readily taken up by B16 tumor cells (murine melanoma) and enhanced DOX and PheoA uptake were detectable in the DOX/PheoA-ALG NPs-treated B16 cells in comparison to carrier free drugs. DOX/PheoA-ALG NPs also elicited intracellular ROS generation, which leads to enhanced toxicity in B16 cells. In vivo studies using B16 tumor-bearing mice further demonstrated that DOX/PheoA-ALG NPs were preferentially accumulated in tumor tissues, resulting in substantial inhibition of B16 tumor growth by chemotherapy and photodynamic therapy, which is also attributable to DOX/PheoA-ALG NP-elicited increase of serum INF-λ levels. Our results demonstrate a major potential of DOX/PheoA-ALG NPs for combinational cancer therapy.