Researchers develop technology to monitor gout in patients

Researchers at Texas A&M University have developed a minimally-invasive biosensor system that they say could help gout sufferers to monitor their symptoms. 

In the February issue of “Sensors,” they say the technology could help create point-of-care therapies for personal management of gout and other conditions.

"Finding more ways to help patients reduce their risks of gout attacks is an important clinical need that hasn't been looked at in detail," said Dr. Mike McShane, department head and professor in the Department of Biomedical Engineering. "In the future, biosensor technology such as ours can potentially help patients take preemptive steps to reduce the severity of their symptoms and lower their long-term health costs from repeated lab visits."

Gout affects the joints of more than eight million Americans. Those who have gout often have higher levels of urate salts in their blood, and those salt crystals accumulate in the space between joints, causing unbearable pain, as well as deterioration of joints and bones.

Definitive diagnosis of gout requires examination of the fluid between the joints, looking for urate crystals and judging the quantity of crystals. These lab tests can be expensive, time consuming, and difficult for older patients. More often physicians use clinical criteria like location of pain and number of incidents. 

"Maintaining low levels of urate is critical for mitigating gout symptoms," said Tokunbo Falohun, a graduate student in the College of Engineering and the primary author of the study. "And so, we wanted to create a technology that is reliable and user-friendly so that patients can easily self-monitor their blood urate levels."

Urate and oxygen react, with the help of the uricase enzyme, to form allantoin. Researchers developed a system to monitor urate levels indirectly with a molecular oxygen sensor called a benzoporphyrin. They then integrated this technology into an optical device which can both emit and capture light. The technology includes a biocompatible hydrogel platform for the benzoporphyrins and the enzyme required for the chemical reaction.

Benzoporphyrins are complex molecules that have unique optical properties that are valuable in the design of optical biosensors. Collisions with oxygen atoms can quench the phosphorescence  from an energized benzoporphyrin.

“This is the result of local oxygen depletion created by uricase in the presence of urate, which leads to a reduction in the collisional quenching of the phosphor by oxygen and greater luminescence lifetimes,” the paper reads. 

Researchers reasoned that when urate levels are high, urate reacts with and depletes oxygen. The result is that benzoporphyrins last longer since less oxygen is around to quench their phosphorescence. They demonstrated this by putting urate into saline filled chambers with a steady flow of oxygen to monitor the levels while a computer calculated and tracked the lifetime of the benzoporphyrins.

"From a global health perspective, we need to empower people to make informed decisions about their health and well-being. In that regard, our system is a step toward building biomedical technologies for continuous and more frequent monitoring of disease symptoms," said McShane.