Green preparation of pH-responsive and dual targeting hyaluronic acid nanogels for efficient protein delivery

PEGylated protein delivery systems that effectively improve the efficiency of protein delivery often suffer limitations of uncontrollable release and non-targeting. In this study, pH-responsive nanogels are developed by forming benzoic imine bonds between hyaluronic acid-graft-methoxy poly(ethylene glycol)-diethylenetriamine (HA-PEG-Diet) copolymers and terephthalaldehyde (TPA) crosslinkers for dual-targeting protein delivery. Cytochrome C (CC), a protein drug, could be facilely encapsulated into the nanogels with a high loading efficiency. Under a physiological environment, these nanogels exhibit excellent stability due to the presence of hydrophobic cores. However, under an acidic tumor microenvironment, the nanogels can undergo pH-induced cleavage of benzoic imines that initiates surface charge conversion from negative to positive, thus promoting cell uptake and protein release. Importantly, confocal images and cytotoxicity results confirm that CC-loaded nanogels can effectively target and eliminate CD44-positive cancer cells via pH-induced surface charge switching and CD44 receptors on cell surfaces. Thus, these pH-responsive dual-targeted nanogels prepared through a green method, have great potential for protein delivery and cancer therapy.