A novel label-free dual-mode aptasensor based on the mutual regulation of silver nanoclusters and MoSe nanosheets for reliable detection of ampicillin.

Current methods for the rapid detection of trace antibiotics in the environment remains problems of low accuracy and false negative or false positive, making the development of fast, and accurate, and reliable methods for antibiotic testing a major challenge that needs to be addressed. Herein, we developed a novel label-free colorimetric and fluorescent dual-mode aptasensor assembled by the strong interaction of layered MoSe nanosheets (MoSe NSs) with ampicillin (AMP) aptamer functionalized silver nanoclusters (Apt-AgNCs) that specifically bind AMP to allow the sensitive and selective detection of AMP. Apt-AgNCs could be adsorbed on the surface of MoSe NSs via van der Waals force to form a nanocomposite, Apt-AgNCs/MoSe NSs. Interestingly, Apt-AgNCs/MoSe NSs act together to construct dual mode aptasensor through modulation of the intrinsic peroxidase activity of MoSe NSs and the fluorescence of Apt-AgNCs. In the presence of AMP, Apt-AgNCs could specifically bind AMP, triggering desorption from the MoSe NSs surface, leading to a decrease in the peroxidase activity of the system with the recovery in Apt-AgNCs fluorescence. The dual-signal aptasensor exhibited good linear colorimetric and fluorescence responses in the AMP concentration ranges of 0.115-2.00 μM and 6-100 nM, respectively. Furthermore, the aptasensor was successfully measured AMP levels in commercially-bought milk and lake water with satisfactory results. Unlike single-signal aptasensors, the constructed dual-signal aptasensor could not only improve the detection precision, but also reduce the false positive or false negative results. These promising results suggest that the dual-readout strategy as demonstrated is general mode for the detection of other antibiotics or compounds using various aptamers functionalized AgNCs in concert with MoSe NSs.