Proof-of-concept study in mice reports that focused ultrasound imaging can be used to release drugs in real-time from a temperature-sensitive implanted gel called iTAG
Implantable devices are common in medicine, from heart pacemakers to artificial eye lenses. Many of these devices, however, require special coatings to combat the foreign body response, contain electronics or wires, or require a continuous power source that limits their lifespan and utility.
A group of researchers have developed an implantable device called iTAG (implantable thermally actuated gel) that is a biocompatible, thermally-responsive, electronic and battery-free gel in which drug-containing capsules can be embedded for on-demand release. When stimulated by focused ultrasound that causes an increase in body temperature, iTAG contracts to locally release of compounds through an opening in the gel and into the body.
In their study, an iTAG device embedded with a fluorescent dye gel capsule was implanted in 4 pairs of mice subcutaneously. One to three days after implantation, iTAG devices in the mice were either triggered experimentally by focused ultrasound (FUS) for 5 minutes, or not in controls. Upon analysis, it was discovered that FUS stimulation caused an increased in the fluorescent signal compared to control mice. Stimulation did not produce any significant tissue damage, and there was no sign of damage to the iTAG device itself after explantation.
This novel method of local compound delivery from a gel using FUS has the potential to facilitate tailored drug dosing, and is noted by the research group to be advantageous over other strategies that involve drug-containing carriers and lipid-based agents. The iTAG device and triggering system has immense promise in personalized medicine as it is relatively cost effective, portable, and does not require large equipment. Potential applications include the release of chemotherapeutic drugs to avoid systemic toxicity, and local release of hormones. Indeed, iTAG will be an interesting technology to follow when it progresses to human clinical trial stages of research.
Written by Fiona Wong, PhD