Oral Presentation Australasian RNA Biology and Biotechnology Association 2026 Conference

Exploring the biological fate of clinical and novel mRNA-lipid nanoparticle delivery systems (147529)

Emily H. Pilkington 1 , Dayangku Nordiyana B. P. Hassanel 2 , Yujia He 1 , Moore Zhe Chen 1 , Colin Pouton 1
  1. Monash Institute of Pharmaceutical Sciences, Parkville, VIC, Australia
  2. Garvan Institute of Medical Research, Darlinghurst, NSW

mRNA therapeutics have revolutionised vaccine platforms through the development and widespread use of Moderna and BioNTech/Pfizer’s lipid nanoparticle (LNP)-formulated Sars-CoV-2 mRNA vaccines during the COVID-19 pandemic.1 Expansion of mRNA-LNP technology beyond infectious disease vaccines, however, necessitates further fundamental understanding of these platforms, so as to inform smart design and delivery.

This talk explores several studies focusing on the LNP platform utilised for mRNA delivery. First, we interrogated the morphology and structural changes LNPs undergo during formulation, through fluorescence resonance energy transfer (FRET), small angle X-ray scattering (SAXS) and cryo-electron microscopy (cryoEM).2 We observed that particle structure changes significantly in the transition from an acidic environment to physiological pH, and demonstrated that ionisable lipid pKa can determine the pH at which these changes occur. Second, we investigated biological clearance of LNPs after repeated administration. Polyethylene glycol (PEG), part of the polymer-lipid component in LNPs required for particle stabilisation and its protein anti-fouling properties, has been known to trigger an immune response against it after repeated dosing.3,4 We developed a mouse model to investigate clearance rates of LNPs formulated with PEG-lipid or alternative hydrophilic polymer-lipids after two weekly doses.5 Our results demonstrated that PEG-LNPs were cleared rapidly from the circulation after a second weekly dose, while several polymer-LNPs, in particular positively-charged POEGMA (POEGMA-2-(dimethylamino)ethyl methacrylate), exhibited minimal clearance after a repeated dose. LNP utilising PDMA (poly(N,N-dimethylacrylamide)) also displayed significantly lower clearance in the presence of anti-PEG antibodies. Lastly, targeted biological delivery of LNPs through development of a novel tLNP system, through collaborative efforts of mRNA Core and CORTx, is highlighted.6

These studies demonstrate the importance of lipid selection and platform design to harness the desired traits of LNP-based mRNA delivery systems and control their biological fate for diverse applications in nanomedicine.

  1. E. H. Pilkington, E. J. A. Suys, N. L. Trevaskis, A. K. Wheatley, D. Zukancic, A. Algarni, H. Al-Wassiti, T. P. Davis, C. W. Pouton, S. J. Kent, N. P. Truong. From influenza to COVID-19: Lipid nanoparticle mRNA vaccines at the frontiers of infectious diseases. Acta Biomaterialia, 131, 16-40.
  2. Y. He, E. H Pilkington, H. J. Kang, W-K. Fong, A. J. Clulow, A. P. R. Johnston, C. W. Pouton. Morphological changes induced by buffer exchange during preparation of mRNA-lipid nanoparticles occur in a stepwise manner as pH is elevated. Molecular Therapy Advances 33, 101578.
  3. T. T. Hoang Thi, E. H. Pilkington, D. H. Nguyen, J. S. Lee, K. D. Park, N. P. Truong. The importance of poly (ethylene glycol) alternatives for overcoming PEG immunogenicity in drug delivery and bioconjugation. Polymers 12, 298.
  4. Y. Ju, W. S. Lee, E. H. Pilkington, H. G. Kelly, S. Li, K. J. Selva, K. M. Wragg, K. Subbarao, T. H. O. Nguyen, L. C. Rowntree, L. F. Allen, K. Bond, D. A. Williamson, N. P. Truong, M. Plebanski, K. Kedzierska, S. Mahanty, A. W. Chung, F. Caruso, A. K. Wheatley, J. A. Juno, S. J. Kent. Anti-PEG antibodies boosted in humans by SARS-CoV-2 lipid nanoparticle mRNA vaccine. ACS Nano, 16, 11769-11780
  5. D. N. B. P. Hassanel, Y. Ju, A. Takanashi, A. Algarni, C. L. Lee, S. J. Kent, C. W. Pouton, E. H. Pilkington. Influence of hydrophilic polymers on the accelerated blood clearance of mRNA lipid nanoparticles upon repeated administration. Nanoscale Horizons, 10, 3396-3404.
  6. M. Z. Chen, D. Yuen, V. M. McLeod, K. W. Yong, C. H. Smyth, B. R. Herling, T. J. Payne, S. A. Fabb, M. J. Belousoff, A. Algarni, P. M. Sexton, C. J. H. Porter, C. W. Pouton, A. P. R. Johnston. A versatile antibody capture system drives specific in vivo delivery of mRNA-loaded lipid nanoparticles. Nature Nanotechnology, 20, 1273-1284.