Color-coded Adrenaline Assay Based on GNP@MnO2 Core-shell Nanoparticles with Dark-field Microscopy

Adrenaline (AD) is an important hormone in central nervous system of mammals, and also works as a medium to transmit signal. The abnormal level of AD in nerve tissues and biological fluids can cause a variety of diseases. In this work, we developed a simple and sensitive dark-field microscopy (DFM)-based single-particle detection (SPD) method for quantitative detection of AD in aqueous solution. MnO2 layer of GNP@MnO2 core-shell nanoparticles could be readily etched due to the reducibility of AD. Since the localized surface plasmon resonance (LSPR) of GNPs was sensitive to the dielectric change of local environment, the etching process resulted in an evident color change of the probe and could be easily observed in real time under dark-field microscope. The AD was thus sensitively detected in a wide linear concentration range (0.02–5 μmol/L) with a limit of detection (LOD) of 7.17 nmol/L. Moreover, this method was used for the analysis of AD content in commercial injection and satisfactory recoveries were acquired. As a consequence, the sensing assay demonstrated herein based on GNP@MnO2 NPs showed great application prospects in molecular recognition and drug quality assay.