Clickable and Degradable Polycarbonate Vehicles for mRNA Delivery

The development of nucleic acid therapies has enabled access to treatments for several diseases previously thought untreatable, yet effective and safe delivery remains a hurdle. The benefit of synthetic vehicles lies in their modularity in optimizing performance and safety. Herein, we present a novel biodegradable polycarbonate alternative to the nondegradable synthetic and viral vectors often utilized in commercial gene therapies. This PC system leverages ring-opening polymerization of a cyclic carbonate to produce polymers (∼20 kDa) with pendant allyl groups compatible with thiol-ene click post-polymerization modification. The derivatization of the parent polymer enables a direct comparison of the pendant groups without molecular weight and dispersity variables. These pendants include 2-(dimethylamino)ethanethiol hydrochloride (DMA) as the cation and one of three hydrophilic modifiers: mercaptopropanol (OH), thioglycolic acid (COOH), and methoxy polyethylene glycol thiol (PEG), which modulate cellular membrane interaction, charge density, and sheathing properties. This family of vehicles forms stable polymer-mRNA complexes (polyplexes), confirmed via dynamic light scattering and gel electrophoresis. In vitro screening assays showed minimal cytotoxic effects with HEK293T (human embryonic kidney) and A549 (human lung cancer) cells, resulting in a statistically significant viability improvement over the polymer control, JetPEI. Coupling the viability with expression values of EGFP-encoded (enhanced green fluorescent protein) mRNA, in vitro delivery efficiency shows the polycarbonate performance on par with JetPEI in nearly all cases while offering degradation via hydrolysis. Overall, this modular polycarbonate scaffold improves cell viability and maintains performance similar to that of positive controls while featuring modularity and degradability.