Implantable Sensor Relays Real-Time Health Data

Tissue-integrating biosensors may soon allow continuous monitoring of body chemistries and provide early warning of developing health problems.

Under development at Profusa (San Francisco, CA, USA), the sensors, which are smaller than a grain of rice, are made of a proprietary hydrogel scaffold based on poly(2-hydroxyethyl methacrylate), a polymer used to make soft contact lenses. The sensors also lack flat surfaces, allowing cells and capillaries to grow into its porous structure without causing an undesirable immune response. The hydrogel scaffold is festooned with dye molecules that respond to various analytes in the blood, such as oxygen, carbon dioxide, glucose or lactate.

A small detector held against the skin shines near-infrared (nIR) light through the skin, causing the dye molecules to fluoresce in concordance with analyte concentration. The fluorescence is captured by a nIR optical reader, which wirelessly transmits the data to a computer or cell phone so as to record analyte concentrations over time. The data can also be shared securely via digital networks with healthcare providers. A study describing the new sensors was presented at the 255th National Meeting & Exposition of the American Chemical Society (ACS), held during March 2018 in New Orleans (LA, USA).

“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,” said study presenter Natalie Wisniewski, PhD, chief technology officer (CTO) and co-founder of Profusa. “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.”

“The sensors would provide a continuous record of your analytes relative to your personal baseline. Then, if something goes off kilter, it's flagged early, before you feel symptoms, so you can get to the doctor in time for treatment,” concluded Dr. Wisniewski. “Other implantable sensors currently on the market have a significant drawback; they often provoke a 'foreign body' immune response that coats the sensor with inflammatory cells or scar tissue. That coating can wall off the device from capillaries and prevent it from sensing chemical changes accurately, so it stops working after a few weeks or months.”

The Lumee Oxygen Platform, the first medical application of Profusa biosensor technology, was approved for sale in Europe in 2017, helping wound-healing specialists track oxygen in the lower extremities of patients undergoing treatment for chronic limb ischemia (CLI).

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