The scientists from the Georgia Institute of Technology say the technology could allow patients to forgo injections and pills, with the implants delivering the active drug for several weeks.
The research, which includes results from studies lookig at insulin release using the microgel films, appears in the 13 September issue of Biomacromolecules.
"We loaded insulin in layers of microgel films in the lab and released bursts of insulin by applying heat to the films. They were extremely stable and could continue to release the drug for more than one month at a time," said Andrew Lyon, associate professor at Georgia Tech's School of Chemistry and Biochemistry.
Crucially, the use of using films assembled from microparticles of the polymer poly(N-isopropylacrylamide-co-acrylic acid) allows more control over drug release than films previously made in monolithic form, according to Lyon.
"Subjection of the film to many thermal cycles enables the embedded peptide to solubilise and subsequently partition through film layers," he said. This means that applying heat could be used to release pulses of insulin to mimic the usual release of this hormone in the body.
The insulin tests, said Lyon, serve as proof of a concept that this method of drug delivery is worth further investigation. Currently, the films release their cargo at 31 C, six degrees below human body temperature, but Lyon's group is working on pushing the release point to a temperature slightly above that of the human body.
Once implanted, the pharmaceutical-loaded films could be placed on chips with resistive heaters and scheduled to release drugs according to a time schedule or another trigger.
Radio control
"One potential use is tying the implant to a blood glucose monitor using radio frequency (RF) technology," said Lyon. "When the monitor detects that a diabetic patient has low blood sugar, it could send a signal to the chip to heat the film and release insulin into the bloodstream."
Aside from insulin dosing in diabetics, other medications that could benefit from being delivered in this way include chemotherapy for cancer, hormonal therapies and drugs that are best administered at particular times of the day, such as high blood pressure medications.
"Of course using these films to deliver medications in humans would require many more trials," said Lyon. "We believe we've taken an important step in new methods of drug delivery."