Click Reaction-Mediated Immunosensor for Ultrasensitive Detection of Pesticide Residues via Brush-like Nanostructure-Triggered Coordination Chemistry.

We develop an ultrasensitive -mediated immunosensor based on the coordination chemistry and Cu(I)-catalyzed 1,3-dipolar cycloaddition of azide andalkyne (CuAAC) and apply it for the detection of pesticide residues. We functionalize polyglutamic acid (PGA) on polystyrene to form a brush-like nanostructure that has a large loading capacity of Cu(II) through the coordination chemistry between PGA and Cu(II). Such a brush-like nanostructure could be used to chelate Cu(II) to modulate the CuAAC between azide-functionalized 1000 nm polystyrene (PS) and alkyne-functionalized 30 nm magnetic nanoparticles (MNP), and the MNP-PS conjugate as a product of CuAAC can act as a magnetic probe in this -based immunosensor. This click chemistry and coordination chemistry-mediated immunosensor allows for an ultrasensitive detection for chlorpyrifos residue (0.022 ng/mL), a 58-fold enhancement compared with that of enzyme-linked immunosorbent assay (1.28 ng/mL), providing a promising platform for detection of trace small molecules.