An optical aptasensor for real-time quantification of endotoxin: From ensemble to single-molecule resolution

Endotoxin is a deadly pyrogen, rendering it crucial to monitor with high accuracy and efficiency. However, current endotoxin detection relies on multistep processes that are labor-intensive, time-consuming, and unsus-tainable. Here, we report an aptamer-based biosensor for the real-time optical detection of endotoxin. The en-dotoxin sensor exploits the distance-dependent scattering of gold nanoparticles (AuNPs) coupled to a gold nanofilm. This is enabled by the conformational changes of an endotoxin-specific aptamer upon target binding. The sensor can be used in an ensemble mode and single-particle mode under dark-field illumination. In the ensemble mode, the sensor is coupled with a microspectrometer and exhibits high specificity, reliability (i.e., linear concentration to signal profile in logarithmic scale), and reusability for repeated endotoxin measure-ments. Individual endotoxins can be detected by monitoring the color of single AuNPs via a color camera, achieving single-molecule resolution. This platform can potentially advance endotoxin detection to safeguard medical, food, and pharmaceutical products.

Automated summary

Here, we introduce an aptamer-based biosensor for real-time optical detection of endotoxin. The sensor utilizes the scattering of gold nanoparticles (AuNPs) coupled to a gold nanofilm, which is controlled by the conformational changes of an endotoxin-specific aptamer. It can be used in ensemble mode with a microspectrometer or single-particle mode with a color camera, achieving high sensitivity and resolution. This platform has the potential to enhance endotoxin detection and ensure the safety of medical, food, and pharmaceutical products.