Multisignal Biosensors Based on Mn Paramagnetic Relaxation and Nanocatalysis for Norovirus Detection.

A multisignal method for the sensitive detection of norovirus based on Mn paramagnetic relaxation and nanocatalysis was developed. This dual-modality sensing platform was based on the strong relaxation generated by cracked Au@MnO 2 nanoparticles (NPs) and their intrinsic enzyme-like activity. Ascorbic acid rapidly cracked the MnO 2 layer of Au@MnO 2 NPs to release Mn(II), resulting in the relaxation modality being in a "switch-on" state. Under the optimal conditions, the relaxation modality exhibited a wide working range (6.02 × 10 3 -3.01 × 10 7 copies/μL) and a limit of detection (LOD) of 2.29 × 10 3 copies/μL. Using 4,4',4″,4″'-(porphine-5,10,15,20-tetrayl) tetrakis (benzenesulfonic acid) (tpps)-β-cyclodextrin (tpps-β-CD) as a T 1 relaxation signal amplification reagent, a lower LOD was obtained. The colorimetric modality exploited the "peroxidase/oxidase-like" activity of Au@MnO 2 NPs, which catalyzed the oxidation of colorless 3,3',5,5'-tetramethylbenzidine (TMB) to blue oxidized TMB, which exhibited a working range (6.02 × 10 4 -6.02 × 10 6 copies/μL) and an LOD of 2.6 × 10 4 copies/μL. In addition, the rapid amplification reaction of recombinase polymerase enabled the detection of low norovirus levels in food samples and obtained a working range of 10 1 -10 6 copies/mL and LOD of 10 1 copies/mL (relaxation modality). The accuracy of the sensor in the analysis of spiked samples was consistent with that of the real-time quantitative reverse transcription polymerase chain reaction, demonstrating the high accuracy and practical utility of the sensor.