Development of a novel LED color-switching type biosensor system for the visualization of fish stress responses
Some biosensor systems have been developed these days for monitoring fish stress responses, through measuring blood glucose concentration (stress indicator) in real-time, even when the fish is swimming freely. However, it is hard to make an instant judgment of fish stress level. In this study, we aimed to develop a new visualization system that can make a natural judgment by visual observation on 3 different levels for fish stress responses. This judgment was achieved through the color change of a multi-color LED to help people make a better understanding of fish stress response. The principle of the sensor system is based on converting a sensor output value obtained by a glucose biosensor corresponding to the stress response into a voltage value and accordingly changing the color of the LED (red, yellow, green). First, interstitial fluid near the sensor insertion point was sampled from the test fish and adjusted to concentrations used to define the yellow and red LED by adding a standard glucose solution. When the glucose level in the collected sample changed to the pre-setted threshold, it was successful in switching the color to green, yellow, and red. Furthermore, we attempted to insert the proposed sensor into an actual sample of fish and monitor the color change of the LED in real-time in vivo while providing stressor to the fish. When applying this system to the real test fish in vivo, a color change corresponding to the sensor response was observed successfully. Therefore, fish stress responses can be visually grasped by using our proposed system.