Critical limb ischemia (CLI) is the most extreme form of peripheral artery disease (PAD). CLI mortality rates are as high as 20% in the first six months after diagnosis. Characterized by poor quality of life, 6-month lower limb amputation rates from 10% to 40%, and extremely high costs of treatment and care, there’s not much positive to say about CLI at this time. Endovascular revascularization treatment (EVT) is a minimally invasive procedure for clearing blocked arteries and removing plaque that can help the prognosis for CLI, but monitoring EVT effectiveness is difficult.

Enter Profusa. We first wrote about Profusa’s injectable Lumee oxygen-sensing biosensor in 2016. Funded in part by the Defense Research Project Agency (DARPA) and the U.S. National Institutes of Health, the initial applications under consideration at the time were tracking tissue oxygen levels at various training and acclimation stages. Lumee consists of a single fiber hydrogel with a fluorescent light-emitting molecule that signals the presence of oxygen. A smart device worn on the skin surface detects the light from the injectable and transmits the data to a smartphone.

In late January 2020, Profusa announced the results of a trial that indicated the Lumee Oxygen Platform “may help improve the clinical management of patients with CLI who are undergoing EVT.” In the trial, four Lumee biosensors were injected in each of 35 patients with CLI who had EVT. Three sensors were placed in the foot and one in the arm, the last to serve as a reference point. The trial data showed that tissue oxygen levels were higher in patients who had significant healing than with patients whose wounds from the procedures did not heal. The Lumee indicators were better predictors of wound healing than the conventional ankle or toe brachial index measures.

Further tissue oxygen level testing with Lumee will continue. An even greater outcome of the Profusa study is the potential significance of injectable biosensor tissue monitoring. If injectable sensors can produce more accurate or more meaningful results than blood testing or external tests, injectables may boost patient outcomes for many conditions and treatments. It’s also noteworthy that back in 2016 Profusa stated that the Lumee injectable can continuously monitor blood chemistry of various elements, and is not limited to just oxygen.