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My buddy recently bought an e-bike on the internet. It has an enormous battery, goes pretty fast, and is salt air resistant – an important feature at the beach. It’s the perfect bike. Or at least it would be, except it is still on a dock in China, waiting for a cargo ship to deliver it. The bike is no good if it can’t get to where it needs to be. The same is true of drugs: a drug is only as good as its delivery system.
Usually, the “buyer” of a drug is a cell somewhere in the body. Sometimes they are in specific areas, and sometimes they’re all over the place. Regardless, getting the drug to the target cells has always been a challenge. Our main delivery routes currently are swallowing, inhalation, skin absorption, and injection. Each has different uses, benefits, and drawbacks, but the route isn’t enough. Ingested medicines, for example, need to survive the harsh stomach acid but still be absorbable by the intestines. Injected medications are cleared by the liver at high speeds, reducing the effectiveness of a drug. Effective drug delivery means getting medicine to the right place at the right time, intact.
One of the best-known developments in medications has been the use of mRNA in COVID vaccines. Actually getting the delicate molecules inside cells for an immune response was one of the unsung heroes of this vaccine. Scientists implemented lipid nanoparticles to get the job done. This was no easy challenge. Lipid nanoparticles are teeny packages of fat that protect the mRNA vaccine until it can get into target cells. They are small and strong to enter cells without disintegrating in the bloodstream. The development of lipid nanoparticles was just in time for the COVID pandemic and has shown to be very effective. The drawbacks are that they must be produced perfectly every time for billions of doses and must be kept extremely cold, at least currently.
A much less widespread development has been the creation of microneedles. These are already in use for cosmeceutical applications. Microneedles are generally smaller than one or two millimeters and don’t puncture the skin all the way to the blood layer. This allows for simpler delivery and at-home administration of some medicines. Microneedles can also be coated with a dry version of medicines, allowing for shelf-stable drug delivery. This could be particularly helpful in areas with inadequate infrastructure and a lack of medical personnel.
Researchers are developing many other new and exciting delivery methods. Targeted organ delivery is the practice of delivering medicine to specific organs. One example is coating a medicine in a urine-resistant coating for injection into the bladder. Cellular delivery uses living cells to carry medication to the target site. These living cells may be red blood cells or beneficial cyanobacteria. Attaching medicine to red blood cells can help drugs resist the powerful cleanup mechanism of the liver. This may allow for lower doses to have bigger effects. Attaching to beneficial spirulina platensis cyanobacteria may help medicines cross the stomach intact and deliver medicine straight to the intestines. This can allow for targeted organ delivery or for longer release of medicines. Finally, some scientists are experimenting with physically squeezing cells. This opens temporary pores for direct drug delivery. Such a system could enable scientists to deliver medicine to billions of cells per minute.
All these exciting new delivery systems will have a big impact. Medicines of the future may be delivered in lower doses and with fewer side effects. We can also expect new uses for old medicines, as they will be able to be used in new ways and able to target new organs. Several of our clinical trials at Encore Research Group use these new methods. It’s an exciting time to help be on the cutting edge of what new medicine delivery will look like in the future. With luck, these new delivery methods will open new doors for medicines to help save lives and heal conditions. With even more luck, my buddy might get his bike by the end of the year.
Written by: Benton Lowey-Ball, B.S. Behavioral Neuroscience
May, M. (2022). Why drug delivery is the key to new medicines. Nature Medicine, 28(6), 1100-1102.
National Institute of Health, National Institute of Biomedical Imaging and Bioengineering. (October, 2016). Drug delivery systems. U.S. Department of Health and Human Services. https://www.nibib.nih.gov/science-education/science-topics/drug-delivery-systems-getting-drugs-their-targets-controlled-manner