Intracellular Delivery of Proteins by Protein-Recognizing Nanoparticles.

Intracellular delivery of proteins can directly impact dysregulated and dysfunctional proteins and is a key step in the fast growing field of protein therapeutics. The vast majority of protein-delivery systems enter cells through endocytic pathways, but endosomal escape is a difficult and inefficient process, demanding fundamentally different methods of delivery. We report ultrasmall cationic molecularly imprinted nanoparticles that bind protein targets with high specificity through their uniquely distributed surface lysine groups. The nanoparticle-protein complexes enter cells even when energy-dependent endocytic pathways are inhibited. The micromolar binding affinities of the nanoparticle for the proteins are strong enough for the cargos to be bound during loading and transportation but weak enough to be released into cytosol for them to interact with the desired cellular targets. The nanoparticles display low cytotoxicity to cells and can be functionalized with fluorescent labels through click chemistry for easy tracking. Both the molecular imprinting and delivery work well for proteins with a range of molecular weights and isoelectric points, affording a convenient method to manipulate cellular functions and intracellular reactions through delivered proteins.