# Optimized Aptamer-Conjugated Gold Nanoparticles for Specific Detection of GII.4 Human Norovirus in Feces

## TL;DR

Researchers developed a sensitive and specific colorimetric biosensor using aptamer-conjugated gold nanoparticles to detect GII.4 human norovirus in fecal samples.

## Contribution

The study introduces a novel aptamer-based biosensor with high specificity and sensitivity for detecting GII.4 human norovirus.

## Key findings

- The biosensor achieved a detection limit of 27.2 copies/mL in fecal matrix with high recovery rates.
- Specific nucleotide bases and a viral capsid residue were confirmed critical for aptamer-virus binding.
- The assay showed minimal cross-reactivity with other diarrheal pathogens.

## Abstract

Human norovirus (HuNoV), particularly the GII.4 genotype, is a leading cause of acute gastroenteritis worldwide, posing a significant public health and economic burden due to its low infectious dose. To address the need for rapid and sensitive detection, we developed a colorimetric biosensor utilizing a structure-optimized aptamer and gold nanoparticles (AuNPs). Biotin-modified aptamers could protect AuNPs from aggregation in salt solution. Upon specific binding to GII.4 HuNoV virus-like particles (VLPs), this protective effect is disrupted, leading to AuNP aggregation and a measurable color shift quantified by the A620/A520 absorbance ratio. Under optimized conditions, the assay demonstrated a linear response (y = 0.004597x + 0.3277, R2 = 0.9922) to GII.4 HuNoV VLP concentrations ranging from 0.1 to 3.0 μg/mL, with the recovery rates between 91.74% and 106.43%. The biosensor exhibited high specificity for GII.4 HuNoV, showing minimal cross-reactivity with other common diarrheal pathogens, and achieved an exceptional detection limit of 27.2 copies/mL in a fecal matrix. Molecular docking and point mutation confirmed the critical roles of specific nucleotide bases (T20, C22, G31, and G44) in the aptamer and the Asn55 residue in the viral capsid for binding. This work establishes a sensitive, rapid, and cost-effective aptamer-based colorimetric platform suitable for the large-scale monitoring of GII.4 HuNoV.