Protein Nanocarrier for Targeted Intracellular Delivery of Functional Antibodies

The cell membrane remains a formidable barrier for antibody-based therapies, and efficient intracellular delivery of functional antibodies would enable modulation of intracellular signaling mechanisms and protein-protein interactions involved in various disorders. This study utilized protein engineering techniques to develop a novel protein nanocarrier that is capable of delivering functional antibodies to the intracellular environment. Each nanocarrier contains six SPAB antibody-binding domains, and is therefore capable of delivering up to six antibodies. The interaction between the SPAB domain of the nanocarrier and the heavy chain constant region of the antibody is noncovalent, thus allowing the nanocarrier to bind different functional antibodies with the same affinity. Three iRGD domains were integrated into the nanocarrier structure to allow for selective targeting of integrins, which are commonly overexpressed in cancer cells. We successfully expressed the protein monomers, assembled the functional nanocarrier, and investigated its antibody-delivery properties. Results of cellular uptake studies involving HeLa, MCF-7, as well as SK-BR-3 cancerous cell lines indicate significant internalization of nanoparticle following 24-hour incubation. Flow cytometry data also indicate substantial cellular uptake of antibody-loaded nanocarrier as compared to soluble antibody control. In addition to efficient cellular uptake, the highly biocompatible and modular nature of our nanocarrier makes it ideal for expanding the scope of antibody-based therapeutics to the intracellular environment.