Penn Engineers have modified lipid nanoparticles (LNPs) — the revolutionary know-how behind the COVID-19 mRNA vaccines — to not solely cross the blood-brain barrier (BBB) but additionally to focus on particular sorts of cells, together with neurons. This breakthrough marks a big step towards potential next-generation therapies for neurological illnesses like Alzheimer’s and Parkinson’s.
In a brand new paper in Nano Letters, the researchers exhibit how peptides — quick strings of amino acids — can function exact focusing 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 essential advance in delivering mRNA to the cell sorts that will be key in treating neurodegenerative illnesses; any such therapies might want to be sure that mRNA arrives on the appropriate 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 regulate which cells the LNPs focused.
“Our first paper was a proof-of-concept lipid nanoparticle design,” says Michael J. Mitchell, Affiliate Professor in Bioengineering (BE) and the paper’s senior writer. “It was like displaying we may ship a bundle from Pennsylvania to California, however we had no thought the place in California it will find yourself. Now, with peptides, we are able to handle the bundle to particular locations with shared options, like each home with a pink mailbox.”
The Problem of Accessing the Mind
Crossing the BBB is tough 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 prescribed drugs. The BBB additionally actively expels supplies it deems hazardous.
“You possibly can inject a therapy straight into the mind or backbone, however these are extremely invasive procedures,” says Emily Han, a doctoral scholar within the Mitchell Lab and the paper’s first writer.
As a result of the BBB permits fat-soluble molecules by means of (like alcohol and THC, which is why these substances have an effect on the mind), sure formulations of LNPs, that are partially made from the identical household of fatty compounds present in on a regular basis oils, can sneak by means of into the mind.
Peptides vs. Antibodies
Till now, most analysis on focusing on particular organs with LNPs has targeted on combining them with antibodies, giant proteins that perform like organic nametags. “Whenever you put antibodies onto LNPs, they may grow to be unstable and bigger in dimension, which makes it actually laborious to squeeze by means of the barrier,” says Han.
In distinction to antibodies, which could be a whole bunch of amino acids in size, peptides are simply dozens of amino acids lengthy. Their smaller dimension 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 doubtless 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 towards 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 one in all our most promising focusing on peptides,” Han says, a molecule referred to as RVG29, a 29-amino-acid phase 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 fancy combination of nucleic acids, lipids and peptides,” says Han. “We needed to optimize quantification strategies to pick the peptides towards 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 tough to arrange,” says Han, “as a result of within the mind, you’ve so many alternative cell sorts and a whole lot of fats that may intrude 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 crew goals to find out what fraction of neurons have to 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 pink 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 therapies for Alzheimer’s, Parkinson’s and different mind illnesses nearer to actuality.
This examine was performed on the College of Pennsylvania College of Engineering and Utilized Science and supported by the U.S. Nationwide Institutes of Well being (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 embody 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 Kids’s Hospital of Philadelphia.
