A new method of label free sensing approach with superior selectivity and sensitivity towards virlabel-freeon is presented here, employing the localized surface plasmon resonance (LSPR) behavior of gold nanoparticles (AuNPs) and fluorescent CdSeTeS quantum dots (QDs). Inorganic quaternary alloyed CdSeTeS QDs were capped with -cysteine via a ligand exchange reaction. Alternatively, citrate stabilized AuNPs were functionalized with 11-mercaptoundecanoic acid to generate carboxylic group on the gold surface. The carboxylic group on the AuNPs was subjected to bind covalently with the amine group of-cysteine capped CdSeTeS QDs to form CdSeTeS QDs/AuNPs nanocomposites. The fluorescence of CdSeTeS QDs/AuNPs nanocomposite shows quenched spectrum of CdSeTeS QDs at 640 nm due to the close interaction with AuNPs. However, after successive addition of norovirus-like particles (NoV-LPs), steric hindrance-induced LSPR signal from the adjacent AuNPs triggered the fluorescence enhancement of QDs in proportion to the concentration of the target NoV-LPs. A linear range of 10 to 10 g mL NoV-LPs with a detection limit of 12.1 × 10 g mL was obtained. This method was further applied on clinically isolated norovirus detection, in the range of 10-10 copies mL with a detection limit of 95.0 copies mL, which is 100-fold higher than commercial ELISA kit. The superiority of the proposed sensor over other conventional sensors is found in its ultrasensitive detectability at low virus concentration even in clinically isolated samples. This proposed detection method can pave an avenue for the development of high performance and robust sensing probes for detection of virus in biomedical applications.

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A novel biosensing system based on graphenemediated surface-enhanced Raman scattering (G-SERS) using plasmonic/magnetic molybdenum trioxide nanocubes (mag-MoO 3 NCs) has been designed to detect norovirus (NoV) via a dual SERS nanotag/substrate platform. A novel magnetic derivative of MoO 3 NCs served as the SERS nanotag and the immunomagnetic separation material of the biosensor. Single-layer graphene oxide (SLGO) was adopted as the 2D SERS substrate/capture platform and acted as the signal reporter, with the ability to accommodate an additional Raman molecule as a coreporter. The developed SERS-based immunoassay achieved a signal amplification of up to ∼10 9 -fold resulting from the combined electromagnetic and chemical mechanisms of the dual SERS nanotag/substrate system. The developed biosensor was employed for the detection of NoV in human fecal samples collected from infected patients by capturing the virus with the aid of NoV-specific antibody-functionalized magnetic MoO 3 NCs. This approach enabled rapid signal amplification for NoV detection with this biosensing technology. The biosensor was tested and optimized using NoV-like particles within a broad linear range from 10 fg/mL to 100 ng/mL and a limit of detection (LOD) of ∼5.2 fg/mL. The practical applicability of the developed biosensor to detect clinical NoV subtypes in human fecal samples was demonstrated by effective detection with an LOD of ∼60 RNA copies/mL, which is ∼10 3 -fold lower than that of a commercial enzyme-linked immunosorbent assay kit for NoV.