The development of in-body sensors capable of continuous, long-term monitoring of body chemistry has been constrained by the formation of local inflammation and scar tissue from the so-called “foreign body response.” Biosensors engineered by South San Francisco-based Profusa overcome this barrier by use of a tissue-like hydrogel, similar to a soft contact lens, which is 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, 
Small and soft, these sensors are designed to track body chemistry for months to years when inserted under the skin. Source: Profusa Inc.comprised of a porous scaffold that induces capillary and cellular ingrowth from surrounding tissue. The hydrogel, a formulation based on poly(2-hydroxyethyl methacrylate), 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 biomolecules of interest.
Adhered to the skin’s surface or held by hand, a separate optical reader is used to read the fluorescent signal from the embedded biosensor. The reader sends excitation signals through the skin to the biosensor, which then emits fluorescent light in response to the biomolecule present. The data is relayed to a smartphone for an encrypted personal record and historical tracking. Data can be shared securely via digital networks with healthcare providers.
The company is seeking U.S. Food & Drug Administration approval for its devices in the U.S. Already approved for marketing in Europe, the devices have been shown to report tissue oxygen levels in patients under treatment for peripheral artery disease.
The research was presented at the 255th National Meeting & Exposition of the American Chemical Society in New Orleans, March 18-22.
