Increases in Lipid Nanoparticle-mRNA Particle Size upon Mesh Nebulisation Vary by Aerodynamic Fraction
Hao-Ying Li1, Bhavini Savarn1, Luke Granger2, Francois Hallac3, Muattaz Hussain4, Abhimata Paramanandana1, Liya Chiu5, Yvonne Perrie4, Robin Shattock2, Charalampos Makatsoris3, Ben Forbes1
1 Institute of Pharmaceutical Science, King’s College London, London SE1 9NH, United Kingdom
2 Department of Infectious Diseases, Section of Immunology of Infection, Imperial College London, London W2 1PG
3 Department of Engineering, Faculty of Natural & Mathematical Sciences, King’s College London, London WC2R 2LS
4 Strathclyde Institute of Pharmacy and Biomedical Sciences, The University of Strathclyde, Glasgow G4 0RE
5 Centillion Technology Ltd., 153 Cambridge Science Park, Cambridge CB4 0GN
Summary
In this study, messenger ribonucleic acid (mRNA) was synthesized by in vitro transcription (IVT) and used to prepare lipid nanoparticles (LNP) by combining the charged nucleic acid and lipid vector in a 1:8 ratio (N/P=8). The LNP-mRNA non-viral delivery system was investigated for its suitability for mRNA delivery to the lungs by using a vibrating mesh nebuliser to aerosolize the LNP-mRNA formulation. It was found that, in comparison with their properties before aerosolisation, the aerosolized LNP-mRNA demonstrated increased particle size (120.3 nm vs. 211.1 nm), higher surface charge (6.12 mV vs. 13.94 mV) and enhanced encapsulation efficiency (EE, 90.9% vs. 99.9 %). Collection and analysis of the aerosol fractions impacted on stages 2-6 of Next Generation Impactor (NGI) showed the nanoparticles recovered from the later stages had increased particle size, while there was no obvious difference in the zeta potential and EE for LNP-mRNA on different stages. Overall, these data showed that the aerosolized LNP-mRNA had an average particle size of ~200 nm, surface charge of ~+13 mV, and EE > 90% w/w. The vibrating mesh generated respirable aerosol droplets for pulmonary delivery of LNP-mRNA, with a fine particle (< 5.0 µm) fraction of 49.3 % w/w and mass median aerodynamic diameter of 5.1 µm.