Highly Selective Detection of Isocarbophos Using an Assay Based on Cationic Polymers and Gold Nanoparticles

This article describes a rapid, simple, and highly selective gold nanoparticle (AuNP)-based colorimetric approach to isocarbophos detection. When isocarbophos is absent, AuNPs in a solution containing the water-soluble polyelectrolyte polydiallyldimethylammonium chloride (PDDA) and an isocarbophos nucleic acid aptamer, PDDA and the aptamer bind electrostatically, and the AuNPs do not aggregate. When isocarbophos is present, it specifically binds to the aptamer, which does not bind PDDA. The free PDDA then induces AuNP aggregation. Effects of buffer solution, pH value, storage time, cationic polymer PDDA concentration, and aptamer concentration on this assay were analyzed, and under optimized conditions, an isocarbophos detection limit of 5.76 nmol/L was achieved, with a linear detection range of 70–480 nmol/L. Recovery tests on lake water samples demonstrated that this method offers good selectivity and anti-interference properties.