Lipid Nanoparticles with Side-Chain Polymer Coating for Targeted mRNA Delivery through Nanobody Attachment

The use of mRNA therapies has innovated the clinical progress of cancer immunotherapy. However, current immunotherapeutic approaches are unable to achieve site- or immune-cell-specific delivery, resulting in adverse immune responses in off-target tissues. In addition, the commercial lipid nanoparticle (LNP) formulations with a poly(ethylene glycol) coating generally undergo significant hepatic accumulation during clearance. To promote site- and immune-cell-specific delivery of therapeutic mRNA-LNPs, we investigated several bioconjugation approaches to attach targeting antibodies onto the surface of polymer-functionalized mRNA-LNPs. Building on our previous work, side-chain sulfoxide polymer-lipid conjugate PMSEA-DSPE was used to incorporate a low-fouling polymeric LNP coating. <i>trans</i>-Cyclooctene functionality was incorporated within PMSEA-DSPE end groups to allow conjugation to the tetrazine-functionalized nanobody 9G8 for EGFR targeting. Bioconjugation methods were compared, including direct conjugation and post-insertion. The results showed that 9G8-attached PMSEA mRNA-LNPs prepared via direct conjugation significantly enhanced cell association and <i>in vitro</i> transfection efficiency with an EGFR-positive cell line, demonstrating the potency of active targeting for mRNA-LNP platforms with side-chain polymer coatings.