A new photonic biosensor can track oxygen levels in real time in organs-on-a-chip to ensure that these systems are mimicking the function of physical organs. Developed at North Carolina State University and the University of North Carolina, Chapel Hill, the biosensor employs a phosphorescent gel that emits IR light after being exposed to IR light, similar to an echo. The lag time between when the gel is exposed to light and when it emits the echoing flash varies, depending on the amount of oxygen in the system’s environment. The more oxygen, the shorter the lag time. By monitoring lag times, the researchers can measure the oxygen concentration in an organ-on-a-chip system down to tenths of a percent. A new biosensor allows researchers to track oxygen levels in real time in 'organ-on-a-chip' systems, making it possible to ensure that such systems more closely mimic the function of real organs. This is essential if organs-on-a-chip hope to achieve their potential in applications such as drug and toxicity testing. The biosensor was developed by researchers at NC State University and UNC-Chapel Hill. Courtesy of Michael Daniele. The biosensor is integrated into a 3D tissue scaffold during fabrication of the organ-on-a-chip, and oxygen concentration is regulated via the control of purging gas flow. The biosensor uses the quenching of palladium-benzoporphyrin by molecular oxygen to transduce the local oxygen concentration in the 3D tissue scaffold. Because IR light can pass through tissue, the researchers can use a reader, which emits IR light and measures the echoing flash from the phosphorescent gel, to monitor oxygen levels in the tissue repeatedly, with lag times measured in the microseconds. The team tested the biosensor successfully in 3D scaffolds using human breast epithelial cells to model both healthy and cancerous tissue. “One of our next steps is to incorporate the biosensor into a system that automatically makes adjustments to maintain the desired oxygen concentration in the organ-on-a-chip,” said professor Michael Daniele. “We’re also hoping to work with other tissue engineering researchers and industry. We think our biosensor could be a valuable instrument for helping to advance the development of organs-on-a-chip as viable research tools.” An organ-on-a-chip is a small-scale, biological structure that mimics a specific organ function, such as transferring oxygen from the air into the bloodstream in the same way the lungs do. Organs-on-a-chip, also called microphysiological models, will be used to expedite high-throughput testing to evaluate the efficacy of new drugs. One obstacle to the use of organs-on-a-chip is the lack of tools designed to retrieve data from the system. The new biosensor will enable data from the organ-on-a-chip to be gathered and analyzed continuously, without affecting the system’s operation, said Daniele. The research was published in Biosensors and Bioelectronics (doi: 10.1016/j.bios.2018.07.035).