Chitosan-based antibacterial AIE luminogens for bioimaging and dual-mode detecting of nitrite in food samples

The polysaccharides are abundant in nature and are typically considered harmless. They can be chemically modified to exhibit a diverse range of fluorescent behaviors. Moreover, these characteristics render polysaccharides particularly promising future for the development of environmentally friendly materials, such as chemical sensors. In this study, a chitosan-based dual-mode sensor (CS-DAS) with aggregation-induced emission (AIE) properties was designed for both fluorometric and colorimetric detection of nitrite. The unique AIE property of CS-DAS enables enhanced fluorescence in aggregated states, overcoming conventional quenching limitations. CS-DAS also showed high selectivity and sensitivity for nitrite detection. By fluorescence and colorimetry, the limits of detection were calculated to be 0.021 μM (1.45 mg/kg) and 0.027 μM (1.86 mg/kg), respectively. This sensor was successfully utilized for the detection of nitrite in sausage samples. Additionally, it exhibited significant antibacterial activity against typical Gram-positive and Gram-negative bacteria. Moreover, CS-DAS showed low cytotoxicity, demonstrating its potential as an excellent fluorescent probe for cell imaging applications.