title: A label-free aptamer-fluorophore assembly for rapid and specific detection of cocaine in biofluids.
abstract: We report a rapid and specific aptamer-based method for one-step cocaine detection with minimal reagent requirements. The feasibility of aptamer-based detection has been demonstrated with sensors that operate via target-induced conformational change mechanisms, but these have generally exhibited limited target sensitivity. We have discovered that the cocaine-binding aptamer MNS-4.1 can also bind the fluorescent molecule 2-amino-5,6,7-trimethyl-1,8-naphthyridine (ATMND) and thereby quench its fluorescence. We subsequently introduced sequence changes into MNS-4.1 to engineer a new cocaine-binding aptamer (38-GC) that exhibits higher affinity to both ligands, with reduced background signal and increased signal gain. Using this aptamer, we have developed a new sensor platform that relies on the cocaine-mediated displacement of ATMND from 38-GC as a result of competitive binding. We demonstrate that our sensor can detect cocaine within seconds at concentrations as low as 200 nM, which is 50-fold lower than existing assays based on target-induced conformational change. More importantly, our assay achieves successful cocaine detection in body fluids, with a limit of detection of 10.4, 18.4, and 36 μM in undiluted saliva, urine, and serum samples, respectively.
authors.affiliation: Department of Chemistry and Biochemistry, Florida International University , 11200 SW Eighth Street, Miami, Florida 33199, United States.
authors.forename: Daniel
authors.initials: D
authors.lastname: Roncancio
authors.forename: Haixiang
authors.initials: H
authors.lastname: Yu
authors.forename: Xiaowen
authors.initials: X
authors.lastname: Xu
authors.forename: Shuo
authors.initials: S
authors.lastname: Wu
authors.forename: Ran
authors.initials: R
authors.lastname: Liu
authors.forename: Joshua
authors.initials: J
authors.lastname: Debord
authors.forename: Xinhui
authors.initials: X
authors.lastname: Lou
authors.forename: Yi
authors.initials: Y
authors.lastname: Xiao
mesh_terms: D052157:Aptamers, Nucleotide / Q000737:chemistry*; D001826:Body Fluids / Q000737:chemistry*; D003042:Cocaine / Q000032:analysis*; D005453:Fluorescence; D005456:Fluorescent Dyes / Q000737:chemistry*; D006801:Humans; D009287:Naphthyridines / Q000737:chemistry*; D013997:Time Factors
chemical_list: C528376:2-amino-5,6,7-trimethyl-1,8-naphthyridine; D052157:Aptamers, Nucleotide; D005456:Fluorescent Dyes; D009287:Naphthyridines; D003042:Cocaine