Engineering of peptide assemblies for adaptable protein delivery to achieve efficient intracellular biocatalysis

Efficient intracellular delivery of native proteins remains a big challenge, which greatly hinders the development of protein therapy. Here, we report a generalizable peptide vector that can encapsulate and deliver various proteins to achieve efficient intracellular biocatalysis. The peptide was rationally designed to be cationic amphiphilic peptide that consist of four functional fragments, that is, a hydrophobic domain to promote molecular assembly, an enzyme-cleavable fragment to introduce stimuli-responsibility, several cationic arginine (Arg) residues to enhance cell interaction and transmembrane efficiency, and the cystine (Cys) residues with redox sensitivity to adjust the stability of the peptide/protein complexes as needed. The peptide can co-assemble with proteins to form stable complexes in aqueous solution under mild condition. The complexes enter cell mainly through caveolae- and lipid raft-mediated endocytosis, giving a delivery efficiency of up to ∼97.2 %. They can then achieve efficient lysosomal escape and disassociation to release native proteins inside cells in response to intracellular stimuli. More strikingly, the delivered protein's bioactivity can be well maintained and the two model proteins of β-galactosidase (β-Gal) and horseradish peroxidase (HRP) both showed excellent intracellular biocatalytic activity. The study develops a versatile and adjustable peptide carrier platform for protein delivery and highlights impactful structure-function relationships, providing a new chemical guide for the design and optimization of functional protein nanocarriers.