Bioreducible amino acid-derived polymeric nanoparticles for delivery of functional proteins.

We report the preparation of protein encapsulated amino acid derived redox-responsive nanoparticles (NPs) as effective nanocarriers for intracellular delivery of proteins. More specifically, acryloyl derivatives of lysine, ornithine, cystine and cystamine, were employed as monomers and disulfide crosslinkers for non-covalent encapsulation of model protein bovine serum albumin (BSA) and were interfacially crosslinked via free radical polymerization to form redox-responsive protein NPs. Notably, prepared NPs exhibited high protein loading content between 37 and 45%, averaged ∼400 nm in hydrodynamic size and possessed a mean surface charge of -15 mV. Furthermore, blank polymeric NPs displayed exceptional cytocompatibility with cell viability exceeding 92% at concentrations as high as 4 mg/mL, while redox-responsive protein NPs displayed glutathione (GSH)-dependent BSA release behavior in vitro. Additionally, cellular uptake studies confirmed that protein NPs entered MDA-MA-231 cells predominantly via the endocytic pathway. Upon cellular internalization, redox-responsive NPs delivered protein into cytosol of cells within 60 min demonstrating intrinsic endosomolytic characteristics and efficient protein release under cytoplasmic high GSH conditions. Most importantly, insulin analog-loaded NPs significantly increased glucose consumption in HepG2 cultures confirming protein stability and retention of protein function. Cumulatively, our approach presents a simple yet effective strategy for intracellular delivery of biologically active proteins for various biomedical applications.