LNPs
See our information and related products and suppliers for LNPs
Lipid nanoparticles (LNP) are a key part of RNA vaccine packaging mechanism. Naked mRNA in serum can be immunogenic and struggles to be delivered into the cellular cytoplasm, a prerequisite for production of the immunogenic protein it encodes. Further, naked mRNA in the serum is exposed to nucleases which can leave it with a half life of less than 5 minutes. Although modifications to the mRNA can make it more chemically resistant to nuclease activity, they can also interfere with translation.
Encapsulating the mRNA or siRNA with a lipid nanoparticle not only protects it from nucleases, but also facilitates entry to the cell. The LNP releases the contents into the cytoplasm enabling access for ribosomes to synthesize the protein.
A variety of approaches have been taken to protect mRNA over the years with varying amounts of success. Some have investigated cationic polymers, such as Poly-L-Lysine, polyethylenimine (PEI), DEAE-dextran, Poly (β-amino esters) (PBAE) and chitosan. Today’s Lipid Nanoparticles (LNP) have developed through several generations, and whilst the recent formulations are often proprietary, their predecessors may be of further interest for research.
Stabilized plasmid–lipid particle (SPLP) are formed by combining the ionizable cationic lipid, neutral lipids, cholesterol and PEG-ylated lipid.
| Category | siRNA | Pfizer-BioNTech mRNA vaccine | Moderna mRNA vaccine | Curevac mRNA vaccine candidate |
|---|---|---|---|---|
| Name product Lipid nanoparticle components | Onpattro * patisiran DLin-MC3-DMA: (6Z,9Z,28,31- tetraen-19-yl-4-(dimethylamino)butanoate 1,2-Distearoyl-sn-glycero-3-phosphocholine (DSPC) PEG2000-DMG =Alpha- (3'-{[1,2-di(myrisyloxy) propanoxy]carbonylamino}propyl)-ω-methoxy, polyoxyethylene Cholesterol | BNT162b2; Comirnatry 0.43 mg ALC-0315 = (4-hydroxybutyl) azanediyl)bis (hexane-6,1-diyl)bis (hexane-6,1-diyl)bis(2-hexyldecanoate) 0.05 mg ALC-0159 = 2-[p(polyethylene glycol)-2000]-N,Nditetradecylacetamide 0.09 mg 1,2-Distearoyl-sn-glycero-3- phosphocholine (DSPC) 0.2 mg Cholesterol | mRNA-1273 SM-102 (heptadecan-9-yl 8-((2-hydroxyethyl) (6-oxo -6-(undecyloxy) hexyl amino) octanoate} PEG2000-DMG = 1-monomethoxypoly ethyleneglycol-2,3-dimyristyl glycerol with polyethylene glycol of average molecular weight of 2000 1,2-Distearoyl-sn-glycero-3 phosphocholine (DSPC) Cholesterol | CVnCoV Cationic lipid (Acuitas Therapeutics) Phospholipid Cholesterol PEG-lipid conjugate |
| Molar lipid ratios (%) Ionizable cationic lipid: neutral lipid: cholesterol :PEG-ylated lipid | 50:10:38.5:1.5 | 46.3:9.4:42.7:1.6 | 50:10:38.5:1.5 | 50:10:3805:1.5 |
The ionizable cationic lipid contains ionizable amine groups at low pH to interact with the anionic mRNA during particle formation and also facilitate membrane fusion during internalization. See the full paper here
PEG-lipid is used to control the particle size and act as a steric barrier to prevent aggregation during storage.
It is likely that particle structure and organization and thus stability of the RNA payload may vary depending on the RNA encapsulated. Capsule ratios and stability may need to be determined empirically for each scenario. Current mRNA vaccines can be stored in the freezer but not for long, but only 5-30 days in the refrigerator, however the RNA stability seems to be the current limiting factor.