a novel label-free cocaine assay based on aptamer-wrapped single-walled carbon nanotubes

objective(s): this paper describes a selective and sensitive biosensor based on the dissolution and aggregation of aptamer wrapped single-walled carbon nanotubes. we report on the direct detection of aptamer–cocaine interactions, namely between a dna aptamer and cocaine molecules based on near-infrared absorption at λ807. materials and methods: first a dna aptamer recognizing cocaine was non-covalently immobilized on the surface of single walled carbon nanotubes and consequently dissolution of swnts was occurred. vis-nir absorption (a807nm) of dispersed, soluble aptamer-swnts hybrid, before and after incubation with cocaine was measured using a cecil9000 spectrophotometer. results: this carbon nanotube setup enabled the reliable monitoring of the interaction of cocaine with its cognate aptamer by aggregation of swnts in the presence of cocaine. disscusion: this assay system provides a mean for the label-free, concentration-dependent, and selective detection of cocaine with an observed detection limit of 49.5 nm.