Ultrasensitive detection of microRNA-21 based on plasmon-coupling-induced electrochemiluminescence enhancement

Noble metal nanoparticles possess excellent optical and electrical properties, and have been widely used in the construction of biosensors and in surface-enhanced spectroscopy. Herein, we describe an enzyme-assisted ultra-sensitive biosensor with gold nanoparticle (GNP) dimers, based on a localized surface plasmon resonance (LSPR)-enhanced electrochemiluminescence (ECL) mechanism. CdS nanocrystals (NCs) acted as ECL emitters, and the GNP dimers were constructed by hybridization of DNA strands on the surface of an electrode modified with CdS NCs after an enzyme-assisted cyclic amplification process. The plasmon-coupling-induced electromagnetic field enhancement effects of the GNP dimers resulted in an increase in ECL intensity of as much as 6.3-fold under optimized conditions. Based on this LSPR-ECL sensor platform, the detection limit for microRNA-21 is as low as 3.6 fM with a wide linear range from 10 fM to 20 pM with good sensitivity and selectivity.