Self-assembled cationic nanogels for intracellular protein delivery

An effective intracellular protein delivery system with self-assembled cationic nanogels is reported. Interaction of proteins with self-assembled nanogels of cationic cholesteryl group-bearing pullulans (CHPNH2) was investigated by dynamic light scattering (DLS), transmission electron micrograph (TEM), fluorescence resonance energy transfer (FRET), and fluorescence correlation spectroscopy (FCS). The cationic nanogels strongly interacted with bovine serum albumin (BSA) and formed monodispersed nanoparticels (<50 nm). The complex more effectively internalized into HeLa cells than cationic liposomes and a protein transduction domain (PTD) based carrier even in the presence of serum. The higher efficiency of the nanogel carrier is probably due to the formation of colloidally stable nanoparticles with the protein. The enzymatic activity of beta-galactosidase (beta-Gal) was retained after internalization into cells. The nanogel carrier promoted nuclear delivery of a GFP-conjugated nuclear localization signal and Tat as a PTD (Tat-NLS-GFP). A blocking experiment with chemical inhibitors revealed the possible involvement of macropinocytosis in the uptake of the nanogel complex. After cellular uptake, the complex of the nanogel-protein was dissociated and the protein was released inside the cell. Such a self-assembled cationic nanogel system should create opportunities for novel applications of protein delivery.