A New Era of Drug Delivery: Less Pain, Fewer Injections
In the near future, receiving regular injections could become far less painful—and much less frequent.
Many commonly used medications, including contraceptives and treatments for chronic illnesses, require routine injections that can be uncomfortable or even painful. But engineers at MIT have developed a promising alternative: an injectable crystal suspension that forms a slow-releasing drug depot under the skin, potentially lasting for months or even years.
“We showed that we can have very controlled, sustained delivery, likely for multiple months and even years through a small needle,” said Giovanni Traverso, associate professor of mechanical engineering at MIT.
A Self-Assembling Drug Depot
The research primarily aims to improve long-term contraceptive options for women, especially in resource-limited regions. While some injectable suspensions already exist, they tend to be short-acting. Longer-lasting options often require thick formulations loaded with polymers, which can be difficult and painful to inject.
This new approach changes that. The team’s goal was to develop a delivery system that works with a fine needle and can release medication steadily over six months to two years.
To achieve this, the researchers used levonorgestrel—a contraceptive known to form crystals—and suspended it in a biocompatible solvent called benzyl benzoate. Once injected, the crystals naturally cluster together to form a compact depot beneath the skin. Because the solvent doesn’t mix easily with bodily fluids, it enables the crystals to stay put and release the drug over time.
“The solvent is critical because it allows you to inject the fluid through a small needle, but once in place, the crystals self-assemble into a drug depot,” Traverso explained.
Tunable Release and Promising Results
One of the system’s key advantages is its tunability. Researchers found they could control how fast the drug is released by tweaking the formulation. By adding tiny amounts of a biodegradable polymer called polycaprolactone—less than 1.6% by weight—they were able to extend the drug’s release duration while keeping it injectable.
“This demonstrates the tunability of our system, which can be engineered to accommodate a broader range of contraceptive needs as well as tailored dosing regimens for other therapeutic applications,” said MIT graduate student Sanghyun Park.
In early studies with rats, the drug depots remained stable and released medication steadily over three months. Remarkably, about 85% of the drug remained at the end of the study period, suggesting the potential for much longer effectiveness. If needed, the depot can also be surgically removed before the drug is fully depleted.
Looking Ahead
This innovative delivery method could minimize pain, reduce injection frequency, and provide consistent, long-term treatment—all with a simple injection.
“We anticipate that the depots could last for more than a year, based on our post-analysis of preclinical data,” Park said. “Follow-up studies are underway to further validate their efficacy beyond this initial proof-of-concept.”
While the current focus is on contraception, the platform could be adapted for other medical uses, including treatment for HIV, tuberculosis, and neuropsychiatric conditions. The team is now conducting additional preclinical research to better understand how the depots behave in realistic skin environments, with human trials on the horizon.