Influence of free chains on the swelling pressure of PEG-HEMA and dex-HEMA hydrogels

Bioactive factor delivery strategies from engineered polymer hydrogels for therapeutic medicine

Polymer hydrogels have been widely explored as therapeutic delivery matrices because of their ability to present sustained, localized and controlled release of bioactive factors. Bioactive factor delivery from injectable biopolymer hydrogels provides a versatile approach to treat a wide variety of diseases, to direct cell function and to enhance tissue regeneration. The innovative development and modification of both natural-(e.g., alginate (ALG), chitosan, hyaluronic acid (HA), gelatin, heparin (HEP), etc.) and synthetic-(e.g., polyesters, polyethyleneimine (PEI), etc.) based polymers has resulted in a variety of approaches to design drug delivery hydrogel systems from which loaded therapeutics are released. This review presents the state-of-the-art in a wide range of hydrogels that are formed though self-assembly of polymers and peptides, chemical crosslinking, ionic crosslinking and biomolecule recognition. Hydrogel design for bioactive factor delivery is the focus of the first section. The second section then thoroughly discusses release strategies of payloads from hydrogels for therapeutic medicine, such as physical incorporation, covalent tethering, affinity interactions, on demand release and/or use of hybrid polymer scaffolds, with an emphasis on the last 5 years.

Targeted nanogels: a versatile platform for drug delivery to tumors

Although nanoparticle-based drug delivery formulations can improve the effectiveness and safety of certain anticancer drugs, many drugs, due to their chemical composition, are unsuitable for nanoparticle loading. Here, we describe a targeted nanogel drug delivery platform that can (i) encapsulate a wide range of drug chemotypes, including biological, small molecule, and cytotoxic agents; (ii) display targeting ligands and polymeric coatings on the surface; (iii) enhance drug retention within the nanogel core after photo-cross-linking; and (iv) retain therapeutic activity after lyophilization allowing for long-term storage. For therapeutic studies, we used integrin αvβ3-targeted lipid-coated nanogels with cross-linked human serum albumin in the core for carrying therapeutic cargoes. These particles exhibited potent activity in tumor cell viability assays with drugs of distinct chemotype, including paclitaxel, docetaxel, bortezomib, 17-AAG, sorafenib, sunitinib, bosutinib, and dasatinib. Treatment of orthotopic breast and pancreas tumors in mice with taxane-loaded nanogels produced a 15-fold improvement in antitumor activity relative to Abraxane by blocking both primary tumor growth and spontaneous metastasis. With a modifiable surface and core, the lipid-coated nanogel represents a platform technology that can be easily adapted for specific drug delivery applications to treat a wide range of malignant diseases.