Lipid nanoparticles are tiny engineered droplets of fat-like molecules that can carry fragile medicines through the body. They became widely known because they help deliver mRNA vaccines safely into human cells. Without protection, mRNA would be quickly broken down by enzymes before it could be useful.
The nanoparticle acts like a nanoscale delivery device that shields the message and helps it reach the right place.
Key Facts
- A typical lipid nanoparticle is about 50 to 150 nm in diameter.
- mRNA is negatively charged, so ionizable lipids help bind and package it inside the particle.
- The lipid shell protects mRNA from RNases, which are enzymes that break down RNA.
- After uptake by endocytosis, the nanoparticle must escape the endosome so mRNA can enter the cytoplasm.
- Once in the cytoplasm, ribosomes read the mRNA and make the encoded protein.
- Drug loading efficiency can be written as percent loading = 100 x mass of mRNA inside particles / total mRNA added.
Vocabulary
- Lipid nanoparticle
- A nanoscale particle made mostly of lipid molecules that can carry genetic or drug cargo into cells.
- mRNA
- Messenger RNA is a temporary genetic instruction that ribosomes read to build a specific protein.
- Ionizable lipid
- An ionizable lipid is a lipid that changes charge with pH, helping bind mRNA during production and release it inside cells.
- Endocytosis
- Endocytosis is the process by which a cell surrounds and takes in material from outside the cell.
- Endosome
- An endosome is a membrane-bound compartment inside a cell that forms after endocytosis.
Common Mistakes to Avoid
- Thinking the nanoparticle is a living organism, which is wrong because it is a nonliving engineered particle made of molecules.
- Assuming mRNA enters the nucleus, which is wrong because vaccine mRNA is translated by ribosomes in the cytoplasm and does not need to enter DNA storage areas.
- Forgetting the need for endosomal escape, which is wrong because mRNA trapped inside an endosome may be degraded instead of translated.
- Treating all lipids in the particle as identical, which is wrong because different lipids provide different functions such as structure, stability, charge control, and circulation time.
Practice Questions
- 1 A lipid nanoparticle has a diameter of 100 nm. What is its radius in nanometers and in meters?
- 2 During formulation, 80 micrograms of mRNA are added and 60 micrograms are successfully packaged inside lipid nanoparticles. Calculate the percent loading efficiency using percent loading = 100 x packaged mRNA / total mRNA.
- 3 Explain why a lipid nanoparticle must both protect mRNA outside the cell and release it after entering the cell.