Rapid detection of tetrodotoxin by aptamer-based gold nanoparticles colorimetric method

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 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. Aptamers (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 test sample detection.

Results The prepared AuNPs had uniform particle size (approximately 15 nm) and a maximum absorption peak at 521 nm. Based on this, a visual TTX detection method using an aptamer-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, aptamer concentration of 80 nmol/L, aptamer incubation time of 25 min, TTX-aptamer incubation time of 20 min, incubation temperature of 10 °C, and 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 (LOD) 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 This study developed an aptamer-based AuNPs colorimetric method for TTX detection, which is expected to provide a simple, rapid, visual, and accurate approach for TTX analysis.