(102b) 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 (HEX) 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. We successfully expressed the protein monomers, assembled the functional nanocarrier, and investigated its antibody-delivery properties. Results of cellular studies using HeLa, MCF-7, as well as SK-BR-3 cancer cell lines indicate significant delivery of fluorescent antibodies bound to the nanocarriers compared to soluble antibody control, as measured by fluorescent microscopy and flow cytometry. We have also achieved specific targeting of HER-2 positive breast cancer cells with our nanocarrier design through addition of targeting antibodies. This result demonstrates the significant potential of this design as a therapeutic delivery platform. Ongoing experiments are aimed at utilizing the HEX nanocarrier to deliver intracellular therapeutic antibodies that inhibit cell signaling pathways. In addition to efficient cellular uptake, the highly biocompatible and modular nature of our nanocarrier makes it ideal for further expanding the scope of antibody-based therapeutics to the intracellular environment.