Construction of ratiometric fluorescence sensor and test strip with smartphone based on molecularly imprinted dual-emission quantum dots for the selective and sensitive detection of domoic acid.

Domoic acid (DA), a highly neurotoxic metabolite produced by phytoplankton, contaminates seafood products and threats humankind. Herein, we have proposed a molecular imprinting fluorescence sensor with internal standard ratiometric mode for sensing of DA in seafood and seawater. In this study, the silicon-coated blue luminous carbon dots (B-CDs@SiO2) and CdTe acted as reference probe (430 nm) and response probe (610 nm), respectively. Subsequently, the two probes were assembled and the molecularly imprinted polymer (MIP) was introduced as the recognition element to construct the core component of the sensor (B-CDs@SiO2/CdTe MIP). When DA exists, it can be specifically adsorbed by the amino-rich imprinted sites on surface of B-CDs@SiO2/CdTe MIP and further assembled into the hydrogen-bonds complex, which can lead to the decrease in the fluorescence signal of MIP at 610 nm owing to the electron transfer from CdTe to DA. However, the fluorescence signal of MIP at 430 nm is not affected because of the protection of silica layer. Based on this principle, the designed internal standard ratiometric fluorescence sensor reveals high sensitivity, excellent selectivity, and wide linear range of 0.03-1 µM with a detection limit of 18 nM. Further, the portable fluorescent test strip with smartphone has been designed for semi-quantitative sensing of DA, which has potential application prospects for field analysis.

Development of fluorescence sensor and test paper based on molecularly imprinted carbon quantum dots for spiked detection of domoic acid in shellfish and lake water.

Excessive levels of domoic acid (DA) in edible shellfish and water can seriously threaten human health and even cause death. Herein, we have developed a fluorescence sensor and test paper based on molecularly imprinted carbon quantum dots (B-CDs@MIPs) for DA analysis. In this research, the prepared carbon quantum dots (B-CDs) with good optical properties were used as the sensitive fluorescent signal probes, and the molecularly imprinted polymers (MIPs) instead of biological antibodies were employed as the specific recognition components because of their high stability and low cost. Due to the shielding effect of imprinted silicon layer and the influence of modified groups introduced in the MIPs preparation process, the fluorescence signal of B-CDs in MIPs is inhibited. Interestingly, the DA can cause the partial recovery of the fluorescence intensity of B-CDs@MIPs by passivating the modified groups on the surface of B-CDs in MIPs. According to this principle, the designed fluorescence sensor reveals outstanding stability, super anti-interference ability, and excellent sensitivity, with the detection limit down to 10 nM. The sensor has been successfully applied to the rapid and accurate spiked analysis of DA in edible shellfish and lake water, providing excellent recoveries. More importantly, the designed inexpensive and easy-to-operate fluorescent test paper can realize preliminary qualitative analysis of DA on site by naked eye, indicating its promising application potential in food and environmental analysis.