Cantilever-based aptasensor for trace level detection of nerve agent simulant in aqueous matrices

摘要

In this paper, sensitive and specific detections on dimethyl methylphosphonate (DMMP), a representative simulant of sarin and organophosphorus pesticides, are demonstrated by a piezoresistive cantilever-based aptasensor in neutral electrolytic solution. By improving the design and fabrication processes of the cantilever-based sensor, a Hooge factor of 4.8 × 10~(-6) and a surface stress sensitivity of 1.47 ×10~(-3) (N/m)~(-1) have been obtained, and the output fluctuation has been minimized to 1 μV at a 3 V bias voltage. For selective and specific molecular capturing, the sensing cantilevers was functionalized by 78-mer 5'-biotinylated aptamers in a biotin-streptavidin system. The aptasensor was experimentally demonstrated to have a linear behavior in detecting DMMP within the concentrations of 50 nM-1.0 μM. Attributed to the low electrical noise and high sensitivity of the piezoresistive cantilever, a limit of detection of 50 nM for DMMP was well obtained in phosphate buffered saline at neutral pH value. Besides, the aptasensors were also exposed to apple juice with DMMP added, whose detecting results indicate that the existence of biomacromolecular polysaccharides and the regional desorption of mercapto self-assembled layer from the gold film on the sensing cantilevers could result in a decrease of the detecting sensitivity slightly. The proposed cantilevers are promising for low cost, trace level and on-site biological/chemical detections.