Fluorescence polarization immunoassay based on carbon-based nanomaterials for rapid and highly sensitive detection of...

The long-term exposure and easy diffusion of imidacloprid (IMI) pose potential risks to human health and pollinating insects. The sensitivity of conventional fluorescence polarization immunoassay (FPIA) needs enhancement for monitoring trace pesticide residues.

Herein, we developed a novel FPIA by employing carbon nanospheres (CNSs) as antibody carriers for fast and highly sensitive detection of IMI. The CNSs-based assay demonstrated superior performance over those using carbon nanotubes (CNTs) or graphene oxide (GO), achieving a detection limit (LOD) of 0.25 μg/L. This represents a 43-fold improvement compared to traditional mAb-based FPIA. Mechanism study revealed that the quasi-spherical structure of CNSs minimizes rotational diffusion anisotropy, leading to the most significant fluorescence polarization change upon binding events, which is the key to sensitivity enhancement. The CNSs-based FPIA exhibited high specificity and was successfully applied to the detection of IMI in pond water, cabbage, apple, corn, and wheat. Spiked recoveries ranged from 93.69% to 105.23% with relative standard deviations below 9.57%, indicating that CNSs-based FPIA exhibited good accuracy, precision, and practicality.

This CNSs-based FPIA protocol provides a new avenue for rapid and highly sensitive detection of IMI and other pesticide residues in food safety detection.