Wearable monitors for health and fitness seemed to be everywhere in the exhibit halls and on the conference stages at CES 2016. But while this generation of biometric monitoring devices goes mainstream, a little Silicon Valley company is working on what could be the next generation of body sensing technology: the injectable.

In a small suite high above the CES convention floor, South San Francisco-based Profusa last week demonstrated the Lumee Oxygen Sensing System, the first of what it expects to be a line of biocompatible sensors. This tiny, flexible sensor is about the thickness of a few human hairs and the length of a piece of long-grain rice. It’s made of hydrogel, a substance similar to the material in contact lenses, but is permeated with fluorescent dye. It’s designed to sit under the skin to monitor the levels of oxygen in the surrounding tissue. The company expects to market the device to help people monitor peripheral artery disease, wound healing, and, eventually, for athletes, muscle performance. Profusa has been in stealth mode since 2009, supporting its research with approximately US $10 million in grants and $15 million in venture financing, CEO Ben Hwang told me.

Originally, Profusa planned, Hwang said, to build a better continuous glucose monitor—one that doesn’t trigger a foreign body response that leads to scar tissue buildup—so it can work accurately for years. As a first step, Profusa’s researchers focused on developing the implantable side of the equation rather than the sensing side. They wanted to create an implantable that could be left in the skin forever without triggering the formation of scar tissue or other reactions. They eventually settled on a design that resembles a sponge; it has rounded edges and microscopic holes into which cell tissue grows.

As a test of the prototype, the team embedded the hydrogel sensor with fluorescent dye sensitive to oxygen. The dye glows when excited by particular wavelengths of light; the brightness of the fluorescence diminishes as oxygen binds to chemical receptors in the dye. To read the device, the researchers shine light on the skin above it; an optical reader picks up the emissions. This cycle can happen as quickly as once per second. And while the scanner is currently a handheld device that communicates to a smart phone, Hwang said it could easily be built into a watch or other type of wearable band.

While the oxygen sensing capability was initially planned to be simply a proof of concept (and, perhaps, a method for calibrating other sensors), Hwang said it turned out to have multiple applications of its own. So the company is releasing the oxygen sensor as its first product. Work on the glucose monitor and other sensors—including ones to monitor levels of lactate, creatinine, and urea—continues. Profusa expects its oxygen sensor to receive clearance in Europe for use in monitoring peripheral artery disease within the next few months, with FDA approval on its way. Profusa then expects to seek approval for other applications, including monitoring wound healing and sleep apnea.

To this point, 14 test human test subjects have each had four or so sensors implanted in them for two years; 80 percent of the devices are still working. The company previously conducted tests in rats and pigs. Hwang himself is one of the test volunteers; because you can’t find the sensors by touch, he’s marked his arm to help him quickly find one of them for a demo (though the reader has what Hwang calls a “stud-finder” mode, with colored LEDs that light up to direct you towards a sensor as you scan someone’s body).

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Restoring Hearing With Beams of Light

Gene therapy and optoelectronics could radically upgrade hearing for millions of people

13 min read
A computer graphic shows a gray structure that’s curled like a snail’s shell. A big purple line runs through it. Many clusters of smaller red lines are scattered throughout the curled structure.

Human hearing depends on the cochlea, a snail-shaped structure in the inner ear. A new kind of cochlear implant for people with disabling hearing loss would use beams of light to stimulate the cochlear nerve.

Lakshay Khurana and Daniel Keppeler

There’s a popular misconception that cochlear implants restore natural hearing. In fact, these marvels of engineering give people a new kind of “electric hearing” that they must learn how to use.

Natural hearing results from vibrations hitting tiny structures called hair cells within the cochlea in the inner ear. A cochlear implant bypasses the damaged or dysfunctional parts of the ear and uses electrodes to directly stimulate the cochlear nerve, which sends signals to the brain. When my hearing-impaired patients have their cochlear implants turned on for the first time, they often report that voices sound flat and robotic and that background noises blur together and drown out voices. Although users can have many sessions with technicians to “tune” and adjust their implants’ settings to make sounds more pleasant and helpful, there’s a limit to what can be achieved with today’s technology.

8 channels

64 channels

Since optogenetic therapies are just beginning to be tested in clinical trials, there’s still some uncertainty about how best to make the technique work in humans. We’re still thinking about how to get the viral vector to deliver the necessary genes to the correct neurons in the cochlea. The viral vector we’ve used in experiments thus far, an adeno-associated virus, is a harmless virus that has already been approved for use in several gene therapies, and we’re using some genetic tricks and local administration to target cochlear neurons specifically. We’ve already begun gathering data about the stability of the optogenetically altered cells and whether they’ll need repeated injections of the channelrhodopsin genes to stay responsive to light.

Our roadmap to clinical trials is very ambitious. We’re working now to finalize and freeze the design of the device, and we have ongoing preclinical studies in animals to check for phototoxicity and prove the efficacy of the basic idea. We aim to begin our first-in-human study in 2026, in which we’ll find the safest dose for the gene therapy. We hope to launch a large phase 3 clinical trial in 2028 to collect data that we’ll use in submitting the device for regulatory approval, which we could win in the early 2030s.

We foresee a future in which beams of light can bring rich soundscapes to people with profound hearing loss or deafness. We hope that the optical cochlear implant will enable them to pick out voices in a busy meeting, appreciate the subtleties of their favorite songs, and take in the full spectrum of sound—from trilling birdsongs to booming bass notes. We think this technology has the potential to illuminate their auditory worlds.

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