Endosome/lysosome-detained supramolecular nanogels as an efflux retarder and autophagy inhibitor for repeated photodynamic therapy of multidrug-resistant cancer

The presence of drug efflux pumps and endo/lysosomal entrapment phenomena in multidrug-resistant cancer cells leads to insufficient and off-target accumulation of anticancer drugs in the cells, which severely reduces the drugs' therapeutic efficacies. Here, we prepare a novel type of photosensitizer (PS)-loaded supramolecular nanogel, which can utilize the endo/lysosomal entrapment for enhanced photodynamic therapy (PDT) of multidrug-resistant cancer. The PS-loaded nanogels can elude the drug efflux pumps, and be markedly internalized by drug-resistant cancer cells through the endocytic pathway. With their pH-sensitive properties, the internalized nanogels can aggregate in the acidic endosomes/lysosomes, thus retarding their exocytosis from the cells. Moreover, the lysosomes of the nanogel-treated cells are severely damaged after irradiation, which inhibits the protective autophagy and improves the photodynamic therapeutic performance of the nanogels. Besides, the in vivo experiments show that the nanogels significantly prolong the tumor retention of the PSs, thus enabling multiple PDT treatments after a single drug injection.

Facile fabrication of hyaluronated starch nanogels for efficient docetaxel delivery

In this study, we designed and synthesized polysaccharidic nanogels comprising starch cross-linked with hyaluronic acid. These hyaluronated starch nanogels were prepared by cross-linking primary hydroxyl groups in polysaccharides (starch and hyaluronic acid) and epoxide groups in 1,4-butanediol diglycidyl ether (used as a cross-linking agent). The nanogels take advantage of hyaluronic acid as a specific ligand for CD44 receptors overexpressed on tumors and the hyaluronic acid/starch core as a compartment for the encapsulation of docetaxel (as model antitumor drug). Here, hyaluronic acid can be enzymatically degraded by tumor cell–specific enzyme (e.g. hyaluronidase-1), which could significantly accelerate docetaxel release from the nanogels. Our experimental results demonstrate that the nanogels promote the release of docetaxel content in the presence of hyaluronidase-1 enzyme. As a result, the nanogels selectively inhibited MCF-7 (with CD44 receptor and hyaluronidase-1 enzyme) tumor cell growth in vitro, suggesting their therapeutic potential for efficient tumor ablation.

Hydrogels: soft matters in photomedicine

Photodynamic therapy (PDT), a shining beacon in the realm of photomedicine, is a non-invasive technique that utilizes dye-based photosensitizers (PSs) in conjunction with light and oxygen to produce reactive oxygen species to combat malignant tissues and infectious microorganisms. Yet, for PDT to become a common, routine therapy, it is still necessary to overcome limitations such as photosensitizer solubility, long-term side effects (e.g., photosensitivity) and to develop safe, biocompatible and target-specific formulations. Polymer based drug delivery platforms are an effective strategy for the delivery of PSs for PDT applications. Among them, hydrogels and 3D polymer scaffolds with the ability to swell in aqueous media have been deeply investigated. Particularly, hydrogel-based formulations present real potential to fulfill all requirements of an ideal PDT platform by overcoming the solubility issues, while improving the selectivity and targeting drawbacks of the PSs alone. In this perspective, we summarize the use of hydrogels as carrier systems of PSs to enhance the effectiveness of PDT against infections and cancer. Their potential in environmental and biomedical applications, such as tissue engineering photoremediation and photochemistry, is also discussed.