Modified lipid nanoparticles for targeted mRNA delivery to the brain

Penn Engineers have modified lipid nanoparticles (LNPs) -; the revolutionary expertise behind the COVID-19 mRNA vaccines -; to not solely cross the blood-brain barrier (BBB) but in addition to focus on particular kinds of cells, together with neurons. This breakthrough marks a big step towards potential next-generation remedies for neurological illnesses like Alzheimer’s and Parkinson’s.

In a brand new paper in Nano Letters, the researchers show how peptides -; quick strings of amino acids -; can function exact concentrating on molecules, enabling LNPs to ship mRNA particularly to the endothelial cells that line the blood vessels of the mind, in addition to neurons. 

This represents an necessary advance in delivering mRNA to the cell sorts that will be key in treating neurodegenerative illnesses; any such remedies might want to be sure that mRNA arrives on the right location. Earlier work by the identical researchers proved that LNPs can cross the BBB and ship mRNA to the mind, however didn’t try to manage which cells the LNPs focused.

Our first paper was a proof-of-concept lipid nanoparticle design. It was like displaying we may ship a package deal from Pennsylvania to California, however we had no concept the place in California it could find yourself. Now, with peptides, we are able to deal with the package deal to particular locations with shared options, like each home with a crimson mailbox.”

Michael J. Mitchell, Affiliate Professor in Bioengineering (BE) and the paper’s senior writer

The problem of accessing the mind

Crossing the BBB is troublesome as a result of the construction has advanced to maintain out nearly any harmful or international molecules, together with most medicines; mRNA molecules are too giant to penetrate the barrier, as are most prescription drugs. The BBB additionally actively expels supplies it deems hazardous. 

“You’ll be able to inject a remedy instantly into the mind or spine, however these are extremely invasive procedures,” says Emily Han, a doctoral pupil within the Mitchell Lab and the paper’s first writer. 

As a result of the BBB permits fat-soluble molecules by (like alcohol and THC, which is why these substances have an effect on the mind), sure formulations of LNPs, that are partially fabricated from the identical household of fatty compounds present in on a regular basis oils, can sneak by into the mind. 

Peptides vs. antibodies

Till now, most analysis on concentrating on particular organs with LNPs has centered on combining them with antibodies, giant proteins that perform like organic nametags. “If you put antibodies onto LNPs, they may grow to be unstable and bigger in measurement, which makes it actually laborious to squeeze by the barrier,” says Han. 

In distinction to antibodies, which may be a whole bunch of amino acids in size, peptides are simply dozens of amino acids lengthy. Their smaller measurement means they don’t seem to be solely simpler to put in giant numbers onto LNPs however cheaper to fabricate. Peptides are additionally a lot much less probably than antibodies to mixture throughout LNP formulation or to impress unintended immune responses.

The selection to make use of peptides began with an surprising encounter between Han and a bat that flew into her room, doubtlessly exposing her to rabies. Whereas researching the vaccines she acquired in opposition to the illness, Han realized that one of many methods the rabies virus crosses the BBB is thru the rabies virus glycoprotein. “I then stumbled throughout certainly one of our most promising concentrating on peptides,” Han says, a molecule generally known as RVG29, a 29-amino-acid section of that protein. 

Testing the idea

To substantiate the peptides have been functioning as supposed, the researchers first wanted to confirm they adhered to the LNPs. “Our LNPs are a posh combination of nucleic acids, lipids and peptides,” says Han. “We needed to optimize quantification strategies to pick the peptides in opposition to all these different alerts.” 

As soon as they knew the peptides had adhered to the LNPs, the researchers then needed to decide whether or not or not the peptide-functionalized LNPs (pLNPs) truly reached the supposed targets in animal fashions. “It is actually troublesome to arrange,” says Han, “as a result of within the mind, you will have so many various cell sorts and a variety of fats that may intervene with measurements.” For greater than six months, Han painstakingly developed a protocol to rigorously take aside mind tissue, nearly like a mechanic disassembling an engine. 

Future instructions

Subsequent, the workforce goals to find out what fraction of neurons should be handled with pLNPs to meaningfully alleviate signs or doubtlessly remedy neurological illnesses. “Returning to the identical analogy, do we have to ship these to each home with a crimson mailbox, or simply 10% of them? Would 10% of neurons be sufficient?” asks Mitchell. 

Answering this query will information the event of much more environment friendly supply methods, bringing the promise of mRNA-based remedies for Alzheimer’s, Parkinson’s and different mind illnesses nearer to actuality. 

This research was carried out on the College of Pennsylvania College of Engineering and Utilized Science and supported by the U.S. Nationwide Institutes of Health (DP2 TR002776), the Burroughs Wellcome Fund, the US Nationwide Science Basis (CBET-2145491), and the American Most cancers Society (RSG-22-122-01-ET).

Further co-authors embrace Sophia Tang, Dongyoon Kim, Amanda M. Murray, Kelsey L. Swingle, Alex G. Hamilton, Kaitlin Mrksich, Marshall S. Padilla and Jacqueline Li of Penn Engineering, and Rohan Palanki of Penn Engineering and the Youngsters’s Hospital of Philadelphia.