Injectable Body Sensors
Up until now, local inflammation and scar tissue from the so-called “foreign body response” has prevented the development of in-body sensors capable of continuous, long-term monitoring of body chemistry. But today scientists are presenting results showing tiny biosensors that become one with the body have overcome this barrier, and stream data to a mobile phone and to the cloud for personal and medical use.
“While fitness trackers and other wearables provide insights into our heart rate, respiration and other physical measures, they don’t provide information on the most important aspect of our health: our body’s chemistry,” explained Natalie Wisniewski, Ph.D. “Based on our ongoing studies, tissue-integrated sensor technology has the potential to enable wearables to live up to the promise of personalized medicine, revolutionizing the management of health in wellness and disease.” Dr. Wisniewski, who leads the team of biosensor developers, is the chief technology officer and co-founder of Profusa Inc., a San Francisco Bay Area-based life science company.
The researchers are presenting their results today at the 255th National Meeting & Exposition of the American Chemical Society (ACS). ACS, the world’s largest scientific society, is holding the meeting here through Thursday. It features more than 13,000 presentations on a wide range of science topics.
Overcoming the Foreign Body Response
Conventional sensors, such as those found in continuous glucose monitors, have a sensing electrode wire that penetrates the skin to measure a target chemical in the fluid that surrounds cells. But because the body “sees” the electrode as foreign material, it needs to be removed and replaced within several days at a different location to avoid the effects of inflammation and scar tissue that eventually prevents the electrode from functioning accurately.
The team at Profusa is developing a family of tiny biosensors composed of a tissue-like hydrogel, similar to a soft contact lens, that are painlessly placed under the skin with a single injection. Rather than being isolated from the body, the biosensors work fully integrated within the body’s tissue — without any metal device or electronics, thereby overcoming the body’s attempts to reject it. To date, the injected biosensors have functioned for as long as four years.
Smaller than a grain of rice, each biosensor is a flexible fiber about 5 mm long and half a millimeter wide, comprised of a porous scaffold that induces capillary and cellular ingrowth from surrounding tissue. The hydrogel is linked to light-emitting fluorescent molecules that continuously signal in proportion to the concentration of a body chemical, such as oxygen, glucose, or other biomolecule of interest.
Smaller than a grain of rice, Profusa’s implantable biosensors can continuously measure body chemistries such as oxygen and glucose, and is designed to overcome the ‘foreign body response’ that results in local inflammation or rejection. © Profusa Inc. 2018
The Lumee™ Oxygen Platform, the first medical application of the biosensor technology, was approved for sale last year in Europe, and is helping wound-healing specialists track oxygen in the lower extremities of patients undergoing treatment for chronic limb ischemia. The device is aimed at avoiding amputations by providing information to caregivers about declining oxygen levels in a patient’s limb. In addition to measuring oxygen, Dr. Wisniewski and her colleagues at Profusa are developing biosensors for continuous monitoring of glucose, lactate, carbon dioxide, and other molecules, toward broadening their biosensor applications in health and disease.
