Smarter drug delivery and ingestible electronics
Early versions of hydrogels were thick and gooey, making it hard to get them inside the body.
“Think of a block of Jell-O. You couldn’t inject something like that,” Dr. Appel said.
But Dr. Appel, whose lab develops new drug delivery systems, has been tinkering with gel formulas for years in hopes that these high-tech globs could someday ferry timed-release drugs to just the right spot in the body.
His new hydrogels start as fully formed gels (which help preserve the drug contents) inside a syringe. But once the plunger is pushed, they magically shape-shift to a liquid thin enough to flow easily through a standard needle. Upon exit, they immediately reform into gels, protecting the inherent cargo from degrading.
This could be a game changer at a time when many cutting-edge drugs – think Humira for arthritis or Ozempic for type 2 diabetes – are made of quickly degrading proteins too large and complex to simply jam into a pill. Instead, they must be injected, often frequently.
“Because the gel takes months to dissolve, it slowly delivers the drug over time,” Dr. Appel said. “You could conceivably go from a shot once a week to once every 4 months.”
Such slow-release hydrogels could make vaccines last longer, in turn teaching the body to better resist emerging virus variants, and deliver tumor-busting therapies more precisely, said Dr. Appel, who has formed a startup and hopes to fast-track the first hydrogel drug delivery system to clinical trials within a few years.
Meanwhile, another team at the Massachusetts Institute of Technology has taken a different approach, developing a standard-sized ingestible hydrogel pill that swells up like a puffer fish in the stomach, lasting a month and slowly releasing drugs all the while. To remove the pill, a patient simply drinks a salt-based solution that shrivels the ping-pong ball–sized device so it can be passed out of the body.
In a paper in Nature Communications, the scientists showed the puffer fish pill could also be loaded with tiny cameras or monitors to track conditions like ulcers or cancer.
“The dream is to have a Jell-O-like smart pill that, once swallowed, stays in the stomach and monitors the patient’s health,” said Xuanhe Zhao, PhD, a researcher on the project and associate professor of mechanical engineering at MIT.
Building joints and regrowing bones
Since the 1970s, researchers have mulled using hydrogels to replace human cartilage, a remarkably strong and flexible tissue made of about 90% water but able to withstand the weight of a car on an area about the size of a coin.
Until recently, those efforts have largely failed. Meaning when knee cartilage wears down, things like cartilage transplants, drilling holes to stimulate new growth, or total joint replacements – all of which require lengthy rehab – are the only options.
But that may be about to change.
Dr. Wiley and his colleagues at Duke recently reported that they’d developed the first gel-based cartilage substitute even stronger and more durable than the real thing.
By attaching their hydrogel to a titanium backing to help stick it in place, they hope to repair damaged cartilage “much like a dentist fills a cavity” long before surgery is necessary.
They too have partnered with industry to bring their hydrogel to market – starting with knees.
“Ultimately, the goal is to do any joint – hips, ankles, fingers, and toes,” Dr. Wiley said.
At the University of Toronto, chemist Karina Carneiro, PhD, and dentist Christopher McCulloch, DDS, are also thinking big.
In a recent paper in Proceedings of the National Academy of Sciences, they describe a hydrogel, designed by Dr. Carneiro and made of DNA, that can be injected, migrate to a defect in bone – an irreparable break, hole from surgery, or jawbone withered by age – and fill in the gap like putty. But not only does it patch the hole, it prompts the bone to regenerate.
In rats with holes in their skulls due to surgery, they found that the treatment did not work as well as the existing gold standard for repairing holes in bone – grafting bone from elsewhere in the body. But it did work.
“These are very early days for DNA hydrogels,” cautioned Dr. McCulloch, a study coauthor and professor in the Faculty of Dentistry, noting that it will likely be a decade or more before such technology could be available to patients. “But there is the potential that DNA hydrogel could someday grow bone without having to have highly invasive surgical procedures. That’s a significant advancement.”