Gold Nanoparticle-DNA conjugates enhanced determination of dopamine by aptamer-based microcantilever array sensor

Aptamer-based microcantilever (ML) array sensor is a recently development method for the analysis of various molecules with free-label, high sensitivity and selectivity. Since its signal-transducing principle is the changes of surface stress or resonance frequency caused by molecules binding on the surface, there have difficulties in determining some low molecular weight substances. Herein, a novel detecting dopamine (DA) method based on aptamers functionalized-ML array using gold nanoparticle (NP)-DNA conjugates as the signal-amplifying strategy was developed. In this method, thiolated DA aptamers were self-assembled on the surface of ML array and then Au NP-DNA conjugates which contained a stretch of complementary sequences for DA aptamers were hybridized to DA aptamers. When DA sample interacted with its aptamer and replaced the Au NP-DNA conjugates, the surface stress of ML array was enhanced about fifteen times and resulted in much more deflection. The deflection was linearly proportional to DA concentration in the range from 0.5 to 4 mu M with a lowest limit of detection 77.3 nM (R-2 = 0.993). Some structural and functional DA analogues did not cause interference for the detection of DA. These results proved that the functionalized-ML array sensor based on Au NP-DNA conjugates could be used as a promising tool to detect low-weight molecules with high sensitivity and selectivity.