DNAzyme-catalyzed etching process of Au/Ag nanocages visualized via dark-field imaging with time elapse for ultrasensitive detection of microRNA

Abstract Dark-field imaging techniques based on the localized surface plasmon resonance (LSPR) of metal nanoparticles provide new insights for real-time monitoring of dynamic reaction processes at single particle level. In this work, the Au/Ag nanocages (NCs) are employed as optical plasmon probes for microRNA detection based on visualized scattering signal changes. Induced by DNAzyme-catalyzed etching process, the scattering signals of plasmon probe “turns-off” due to the decreased silver proportion of Au/Ag NCs with time elapse. The dynamic process is monitored under dark-field microscopy, in which the waiting time that elapsed before a nanocage stochastically disappeared is found directly related to the concentration of the target microRNA. Combined with the strand displacement and hybridization cascade amplification strategy, the concentration of microRNA-21 in cell lysate is determined by statistical analysis with high sensitivity and selectivity. The proposed dark-field scattering biosensing based on nanocage probes is convenient for accurately judging end-point during real time monitoring over time, and provides a novel strategy for the development of biosensing at single particle level.