Label-free ultra-sensitive colorimetric detection of hepatitis E virus based on oxidase-like activity of MnO₂ nanosheets

Hepatitis E virus (HEV) is an evolving infectious entity that causes viral hepatitis infections worldwide. Current routine methods of identifying and diagnosing HEV are someway laborious and costly. Based on the biomimicking oxidase-like activity of MnO₂ nanosheets, we designed a label-free, highly sensitive colorimetric sensing technique for HEV detection. The prepared MnO₂ catalyst displays intrinsic biomimicking oxidase-like catalytic activity and efficiently oxidizes the 3,3′,5,5′-tetramethylbenzidine (TMB) substrate from colorless to blue colored oxidized TMB (oxTMB) product which can be measured at 652 nm by UV–visible spectrum. When the HEV-DNA was added, DNA adsorbed easily on MnO₂ surface through physical adsorption and electrostatic interaction which hinders the oxidase-like catalytic activity of MnO₂. Upon the introduction of target, the HEV target DNA binds with its complementary ssDNA on the surface of MnO₂, the hybridized DNA releases from the surface of MnO₂, which leads to recovery of oxidase-like catalytic activity of MnO₂. This strategy was applied to construct a colorimetric technique for HEV detection. The approach works in the linear range of 1 fM–100 nM DNA concentration with the limit of detection (LOD) of 3.26 fM (S/N = 3) and quantitative limit (LOQ) of 36.08 fM. The TMB-MnO₂ platform was highly selective for HEV target DNA detection when compared with potential interferences. Result of serum sample analysis demonstrates that this sensing system can be used for clinical diagnostic applications. Graphical Abstract: [Figure not available: see fulltext.]