International journal of pharmaceuticsSep 17, 2024

Using RAFT lipopolymers instead of poly(ethylene glycol) in mRNA lipid nanoparticles for improved gene delivery

mRNA Technology Weekly Brief ↗PubMed ↗DOI ↗

Updated Mar 17, 2026

Abstract

The synthesis of five alternative polymers resulted in LNPs that demonstrate comparable or improved in vivo gene expression and antibody production compared to traditional PEG-based formulations.

Lipid nanoparticles (LNPs) are effective carriers for transporting mRNA into cells, as shown in mRNA vaccines for COVID-19.
Current LNP formulations use poly(ethylene glycol) (PEG), which has limited modification options and can trigger immune responses.
Alternative polymers synthesized through reversible addition-fragmentation chain transfer (RAFT) polymerisation could replace PEG while maintaining efficacy.
The new RAFT lipopolymer LNPs enhanced in vivo gene expression due to the introduction of positive charges along their backbone.
This research supports the potential of PEG-free mRNA vaccines and therapeutics using innovative polymer strategies.

Simplified

Lipid nanoparticles (LNPs) have emerged as promising carriers to efficiently transport mRNA into cells for protein translation, as seen with the mRNA vaccines used against COVID-19. However, they contain a widely used polymer - poly(ethylene glycol) (PEG) - which lacks the functionality to be easily modified (which could effectively control the physicochemical properties of the LNPs such as its charge), and is also known to be immunogenic. Thus, it is desirable to explore alternative polymers which can replace the PEG component in mRNA LNP vaccines and therapeutics, while still maintaining their efficacy. Herein, we employed reversible addition-fragmentation chain transfer (RAFT) polymerisation to synthesise five PEG-lipid alternatives that could stabilise LNPs encapsulating mRNA or pDNA molecules. Importantly, the resultant RAFT lipopolymer LNPs exhibit analogous or higher in vivo gene expression and antigen-specific antibody production compared to traditional PEG-based formulations. Our synthesis strategy which allows the introduction of positive charges along the lipopolymer backbone also significantly improved the in vivo gene expression. This work expands the potential of RAFT polymer-conjugated LNPs as promising mRNA carriers and offers an innovative strategy for the development of PEG-free mRNA vaccines and therapeutics.

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Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

PubMed

Using RAFT lipopolymers instead of poly(ethylene glycol) in mRNA lipid nanoparticles for improved gene delivery

Abstract

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Competing interests

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