Characterization and Optimization of Monobody Proteins for Targeting of Polymeric Nanoparticles to Endothelial Cells

The conjugation of antibodies (Abs) to nanoparticles (NPs) is often used to target NPs to specific cell populations. However, there are issues with the methods of Ab attachment to the NP, and the effectiveness of the targeting varies with different conjugation methods. Site-specific conjugation of monobody (Mb) proteins to NPs help address the effectiveness of Ab attachment by controlling the Ab orientation on the NPs to improve targeting to cells. Here, we expand upon previous work showing the effectiveness of the Mb attachment system by providing a more in-depth characterization of Mb proteins. We investigated impacts on NP stability and in vitro cell binding of protein amounts (Mb and Ab), different Mb proteins (targeting mouse immunoglobulin G1 and human intercellular adhesion molecule 2), polymeric NP types (based on polylactic acid and poly amine-co-ester), and a conjugation method optimization. The results suggest that while Mb proteins are effective in targeting NPs to cells, different Mb proteins and different polymer NPs have different binding and stability profiles, highlighting the importance of characterization when adapting the system to NPs of different chemistry.