# Advances and Future Perspective on Detection Technology of Human Norovirus
## 2 Detection Techniques
### Biosensor
#### 2.4.1 Electrochemical Biosensor
The HuNoV-specific aptamers labelled with ferrocene (as redox probes) and biotin were immobilised on the carbon electrodes modified by graphene-gold nanoparticles and thiolated streptavidin. The HuNoVs were captured by the specific aptamer, which resulted in changes in the electrochemical signal. Then, differential pulse voltammetry analysis was used to determine and analyse the results. Using this method, the LOD for VLPs reached 100 pM. [PERSON] et al. developed an impedance biosensor on the basis of NoroBP-nonFoul (Flexi)\({}_{2}\) peptide-modified gold screen-printed electrode (SPE) for HuNoV GII.4 detection. In oyster samples, the LOD reached 1.7 genomic copies/mL with high sensitivity and good reproducibility [93]. To date, the most reported electrochemical biosensor detection methods use the classic three-electrode system (working electrode, counter electrode and reference electrode). Traditional solid electrodes are large, and they require complicated cleaning steps before use. However, SPE has low cost, less reagents, easy modification, flexible selection for solid-phase carriers (ceramics, paper, films, etc.) and inks (carbon, gold, etc.) and self-designed shape and size, which is suitable for mass production and portable or small devices [104; 105]. Therefore, SPE has greater application advantages than traditional solid electrodes [105]. In addition, the combination of SPE and microfluidic technology can significantly reduce the consumption of reagents and samples. Multiple steps such as sample processing and detection can be integrated through a rational design to achieve a simple, fast and efficient testing [106; 107; 108; 109]. Figure 4: Schematic diagram of electrode functionalization and aptasensing for norovirus detection by screen-printed carbon electrodes. Grp–AuNPs: Graphene–gold nanoparticle composite, Strp-SH: Thiolated streptavidin, Bt-Atp-Fc: Biotin- and ferrocene-tagged aptamer. Figure 3: Schematic diagram of preparation of affinity peptide electrochemical sensor for norovirus detection. **1**, Selection of affinity peptide as molecular binders using phage display technique. **2**, Synthesis and immobilization of peptides. **3**, Addition of norovirus. **4**, Electrochemical detection. Figure 2: Detection of HuNoV using electrochemical biosensor with concanavalin-A. (**a**) The nanostructured gold electrode; (**b**) immobilized with ConA; (**c**) blocked by mercaptohexanol; (**d**) addition of HuNoV; (**e**) addition of detection antibody; (**f**) addition of secondary antibody. The cost for the development of an electrochemical biosensor is important. The gold electrodes have strong electric signals, but they are expensive. On the contrary, carbon electrodes have a lower cost, but the electrical signals are weaker. Therefore, carbon electrodes are often modified by various methods. Gold nanoparticles (AuNPs) have good biocompatibility, excellent conductivity and high surface-to-volume ratio. AuNPs are commonly used modification materials, particularly for electrochemical immunosensors [110; 111]. [PERSON] et al. tested the signal amplification performance of electrochemical biosensors modified by AuNPs. The EIS results indicated that the signal was significantly enhanced [112]. Moreover, the shapes (nanoballs, nanorods, nanoislands, nanocages, etc.) and sizes of the gold nanomaterials can be controlled according to the needs [113].