Lipid-Polyhydroxyalkanoate Hybrid Nanoparticles as Sustainable Platform for mRNA delivery

The success of mRNA vaccines for the treatment of COVID-19 has generated enormous interest in mRNA therapeutics for various diseases, highlighting the need for robust delivery platforms. Combining the excellent transfection properties of lipids with the high stability of polymeric nanoparticles in a single hybrid system has become an attractive approach to generate next generation mRNA delivery systems. We introduce a modular lipid-polymer hybrid nanoparticle (LPHNP) design based on medium-chain-length polyhydroxyalkanoates (mcl-PHAs) as sustainable alternative to poly(lactic-co-glycolic acid) (PLGA), and a polymer-lipid (DMG-PEG, or poly(2-ethyl-2-oxazoline-myristic acid (PEtOx-MA)). A small library of LPHNPs containing the cationic lipid DOTAP were synthesized using a scalable microfluidic process. Physico-chemical and biological properties of mRNA-LPHNPs were studied. Results showed that the mcl-PHAs (PHA_F10 and PHA_Glu) derived from Pseudomonas putida can form distinct LPHNPs depending on polymer-to-lipid ratios, and mcl-PHA composition. Cell toxicity, transfection efficiency, serum stability, and the effect of protein interactions was investigated in HeLa cells and human brain endothelial (hCMEC/D3) cells. Importantly, the particles' biophysical properties and transfection efficacies were not affected after lyophilization and storage at various temperatures for two months. Reporter mRNA was identified across all major organs collected after intravenous injection into mice with limited protein expression in the blood, highlighting the excellent stability of hybrid nanoparticles against blood cell interactions. This approach holds promise for accelerating development of a novel sustainable polymer for mRNA delivery that differs from conventional lipid nanoparticle systems.