Messenger RNA (mRNA) is a class of biological molecules that allows ribosomes to synthesize proteins by moving the information encoded by genes from the nucleus to the cytoplasm. The best-known example of how mRNA sequences can be engineered to encode particular proteins is the mRNA vaccine for COVID-19. Since mRNA molecules are big and chemically unstable, mRNA must be delivered to cells using a vector. Lipid nanoparticles (LNPs), which are made of ionizable lipids, cholesterol, helper lipids, and polyethylene glycol, are one of the most cutting-edge methods for delivering mRNA.
Researchers at the Faculty of Pharmaceutical Sciences at Hokkaido University, under the direction of Assistant Professor Yusuke Sato and Professor Hideyoshi Harashima, and at the Nitto Denko Corporation, under the direction of Kazuki Hashiba, have created a novel branched ionizable lipid that, when added to LNPs, significantly improves the efficiency of mRNA delivery. The journal Small Science published their findings.
Ionizable lipids with branching tails have been demonstrated to boost the effectiveness of mRNA distribution by LNPs in prior research. However, a thorough examination of the impact of branching ionizable lipids has been hampered by two significant problems. First, tail branching results in a huge variety of compounds, and second, there are only a small number of branching ionizable lipids that are commercially available. To get over these obstacles, the researchers created a systematic library of branching ionizable lipids and then restricted this library to a certain subset of branching lipids that could be defined by merely the total carbon number and symmetry. The stability of LNPs containing mRNA was then examined for each of the 32 lipids in this library (LNP-RNA).
The team found that the microviscosity of LNP-RNAs with highly symmetric branching lipids was higher and that this higher microviscosity was positively connected with an increase in the stability of LNP-RNAs in storage. In LNP-RNAs, highly symmetric branching lipids are positively linked with mouse liver and spleen protein expression. They discovered that organ selectivity is influenced by the length of the branching chain.
The branching lipid CL4F 8-6 was able to distribute and store mRNA with the greatest stability and effectiveness. With just one dose of LNPs, the authors showed that this specific lipid could be employed in LNPs intended for gene editing, successfully suppressing the target gene in mice by 77%.
This study showed that the best LNP properties for effective intracellular delivery and stable formulations were largely influenced by branched lipids with a high degree of symmetry. Future research will concentrate on creating enlarged lipid libraries to comprehend the characteristics of other branched lipids, which could result in the creation of new lipids.
