Background Tetrodotoxin (TTX), a potent neurotoxin widely distributed in marine organisms such as pufferfish, poses a significant public health threat caused by accidental consumption of TTX-contaminated aquatic products. This toxin can induce respiratory failure and fatal outcomes, underscoring the urgent need for highly efficient and sensitive detection technologies to ensure food safety.

Objective This study aims to construct a simple, visual colorimetric detection method based on aptamer-modified gold nanoparticles (AuNPs) sensor.

Methods AuNPs were prepared by the sodium citrate reduction method, and characterized by transmission electron microscopy (TEM) and ultraviolet-visible (UV-Vis) absorption spectroscopy. Aptamer (Apt) were adsorbed onto the surface of AuNPs through electrostatic interaction, which protected AuNPs from aggregation and color change in high-salt environments to a certain extent. When TTX existed in the system, it specifically bound to Apt, causing AuNPs to aggregate and change color. After optimizing the experimental conditions, the ratio of A₆₂₀/A₅₂₁ at different TTX concentrations was determined by UV spectroscopy to establish a linear regression equation, calculate the limit of detection, and perform specificity analysis and spike-recovery experiments.

Results The prepared AuNPs had uniform particle size (approximately 15 nm) and a maximum absorption peak at 521 nm. Based on the result, a visual TTX detection method using an Apt-AuNPs colorimetric sensor was constructed. The optimal experimental parameters determined through condition optimization were as follows: AuNPs volume fraction of 45%, NaCl concentration of 300 mmol/L, NaCl reaction time of 10 min, Apt concentration of 80 nmol/L, Apt incubation time of 25 min, TTX-Apt incubation time of 20 min, TTX-Apt incubation temperature of 10 °C, and TTX-Apt pH of 5. Under the optimized conditions, TTX detection showed a good linear relationship between TTX concentration (19.53~312.5 ng/mL) and the corresponding A₆₂₀/A₅₂₁ value, with a linear correlation coefficient (R²) of 0.995 7 and a limit of detection of 12.97 ng/mL. In the spike recovery experiments, the recovery rates of TTX ranged from 104.2% to 108.4%, with relative standard deviations (RSD) of 0.85%~1.77%.

Conclusion The study developes an aptamer-based AuNPs colorimetric method for TTX detection, which is expected to provide a simple, rapid, visual, and accurate approach for TTX analysis.