Biomass carbon dots and fluorescein isothiocyanate based ratio metric fluorescent hydrogel sensor for detecting tetracycline and extending salmon shelf life

This study aimed to develop a composite material with dual functions of detection and preservation. A dual-emission peak ratio fluorescent probe was developed by using the carbon dots of the extract of the Aronia melanocarpa fruits (A-CDs) and fluorescein isothiocyanate (FITC) at a molar ratio of 1:10. A-CDs was used as the tetracycline-responsive sensing element, while FITC was used as the internal reference. This A-CDs@FITC probe exhibited excellent performance in tetracycline detection, showing a linear response of r=0.997 and the detection of limit was 0.195 μmol/L. The A-CDs@FITC probe was then encapsulated in a κ-carrageenan/polyvinyl alcohol hydrogel matrix to create a composite material. The results showed that the composite hydrogel also retains good detection ability, with a linearity of r=0.998 and the detection of limit was 0.219 μmol/L. Furthermore, the composite hydrogel demonstrated significant antioxidant activity (with a free radical scavenging activity of 87.4±1.5%) and good antibacterial effects against E. coli and S. aureus . In the salmon preservation test, the composite hydrogel extended the shelf life of salmon by two days. This work has established a composite hydrogel system capable of simultaneously detecting tetracycline residues and having antioxidant and antibacterial effects, providing a novel comprehensive strategy for food safety monitoring and preservation. • A-CDs and FITC form a dual-emission peak ratio probe, with a better linear relationship and greater stability. • The A-CDs@FITC probe was embedded into the hydrogel based on κ -carrageenan and polyvinyl alcohol to construct the fluorescent hydrogel. • The hydrogel has the dual function of detecting residual tetracycline and extend the shelf life of salmon.