Autonomous medical devices: running well in your body

In theory, autonomous medical technologies can be used in a diagnostic or therapeutic capacity inside the body under certain conditions. This may not sound like a new invention at first. After all, implantable cardioverter-defibrillators have monitored and fixed abnormal heart rhythm for many years. But by now, autonomous medical devices are being developed to support an increasing number of fields and applications.

A procedure called capsule endoscopy has been around for some time. It allows the examination of the small intestine which is the part of the bowel that cannot be reached by traditional upper endoscopy or by colonoscopy. A physician administers a pill-sized video camera the patient swallows. The camera takes pictures of the small intestine as it passes through and sends them wirelessly to a small recording device outside the body. While this is an autonomous approach, it is not considered "smart" based on the current state of technology, since the tiny capsule only runs a preset program once it is swallowed.

The first autonomous and smart medical device for use in the human body could come in the form of miniaturized robots. These are not physical machines, but structures made of materials that react to conditions within the body. One example of this type of application is the "Theragripper" by the Johns Hopkins University School of Medicine. The device latches onto intestinal mucosa and gradually releases drugs into the body. This is made possible by a heat-sensitive paraffin wax coating that keeps the Theragripper open. Once it has reached the temperature inside the body, the star-shaped microdevice closes autonomously.

Another conceivable application are implants made of smart materials; an approach pursued by Prof. Christine Selhuber-Unkel from the Institute for Molecular Systems Engineering (IMSE) at the Heidelberg University. "These implants incorporate sensing and actuation components to detect and intelligently respond to changes in the environment." Those might be internal stimuli, such as changes in the pH of the surrounding medium, or externally controlled stimuli such as light. "We pursue projects that focus on responsive material-controlled drug release. Other projects emphasize the control of cell growth via materials," Selhuber-Unkel said in an interview with MEDICA-tradefair.com.

Insulin pumps combined with real-time continuous glucose monitoring (CGM) could soon be on the cusp of a "smart" breakthrough. Today's insulin pumps are mostly semi-autonomous by releasing small doses of insulin continuously and requiring the wearer to request additional doses before or after meals if needed. The wearer also still needs to occasionally self-monitor blood glucose levels.

An advanced "hybrid closed loop" system, which uses an algorithm to automatically adjust insulin in response to predicted glucose levels entered the U.S. market in 2019. The system is considered a hybrid since the wearer must still actively confirm insulin delivery after meals and calibrate the blood glucose sensor twice daily. The next step in this development would be an artificial pancreas device system that autonomously monitors and regulates blood glucose levels like a natural pancreas.

In an interview with MEDICA-tradefair.com, Dr. Sebastian Kibler of the Fraunhofer Research Institution for Microsystems and Solid State Technologies EMFT explains how drug delivery pumps can be implanted in the body to facilitate tumor therapy: "This type of system could then be implanted under the skin in the upper chest or lower abdominal area. From there, a catheter can be placed to the delivery site, usually into the tumor tissue or the distributing blood vessels." He also thinks the drug pump could work as an implantable insulin pump for diabetics. "In this case, the minimum life expectancy of the implant is ten years."

Implantable pumps for drug delivery would only be autonomous within the scope of their programming and - like insulin pumps - would deliver a continuous bolus of medication or facilitate on-demand drug delivery. It is unclear when and if fully autonomous medical technology that responds intelligently to changing circumstances becomes available. This is most likely possible with simple mechanisms such as targeted drug delivery and/or controlled release of therapeutic agents.

This type of development is probably not possible or even useful when it comes to more complex applications such as tumor therapy. On the one hand, it is doubtful whether sensor technology advancements will eventually be able to continuously respond to changing tumor biomarker concentrations. On the other hand, this type of treatment also requires medical observation and active surveillance, which makes an intelligent implant redundant. Having said that, these types of implants might be beneficial in bridging the gap between doctor's visits as continuous medication administration facilitates uninterrupted treatment and reduces the stress of systemic chemotherapy for cancer patients.

The Saarland University (Germany) is developing an active implant for complex fractures. It is designed to monitor the healing process of bone fractures and to warn of incorrect loading. The device is based on artificial intelligence, multiple bone fracture measurements, functional gait assessments, and Nitinol, a shape-memory alloy. The first prototype is expected in 2025.