Development of flexible glucose biosensor for fish stress monitoring

Stress in farmed fish is a major risk and its control is an important challenge due to its association with disease and water quality issues. Disease caused by Aeromonas hydrophila infection and elevated ammonia levels can lead to high mortality and stress among cultured fish. Glucose monitoring is valuable tool to assess the stress status of fish since blood glucose levels are elevated in the stress condition. In this study, we monitored glucose levels in the abdominal interstitial fluid (AISF) because AISF is prevalent in various fish species and the glucose levels in the AISF correlate with blood glucose levels. We developed a novel flexible biosensor based on polyethylene film capable of continuously monitoring glucose levels in fish in real time without the need for highly invasive procedures. Subsequently, we demonstrated the versatility and durability of this flexible biosensor through successful glucose level measurements in controlled laboratory conditions (in vitro) and in real-world living environments of fish (in vivo). This breakthrough technology has proven effective in monitoring stress responses in various fish species, including freshwater species like Nile tilapia and saltwater species like the Nibe croaker and Largescale blackfish. These promising results provide valuable insights into enhancing aquaculture practices, promoting the well-being of farmed fish, and advancing the long-term sustainability of the aquaculture industry.