title: A novel aptasensor based on single-molecule force spectroscopy for highly sensitive detection of mercury ions.
abstract: We have developed a novel aptasensor based on single-molecule force spectroscopy (SMFS) capable of detecting mercury ions (Hg(2+)) with sub-nM sensitivity. The single-strand (ss) DNA aptamer used in this work is rich in thymine (T) and readily forms T-Hg(2+)-T complexes in the presence of Hg(2+). The aptamer was conjugated to an atomic force microscope (AFM) probe, and the adhesion force between the probe and a flat graphite surface was measured by single-molecule force spectroscopy (SMFS). The presence of Hg(2+) ions above a concentration threshold corresponding to the affinity constant of the ions for the aptamer (about 5 × 10(9) M(-1)) could be easily detected by a change of the measured adhesion force. With our chosen aptamer, we could reach an Hg(2+) detection limit of 100 pM, which is well below the maximum allowable level of Hg(2+) in drinking water. In addition, this aptasensor presents a very high selectivity for Hg(2+) over other metal cations, such as K(+), Ca(2+), Zn(2+), Fe(2+), and Cd(2+). Furthermore, the effects of the ionic strength and loading rate on the Hg(2+) detection were evaluated. Its simplicity, reproducibility, high selectivity and sensitivity make our SMFS-based aptasensor advantageous with respect to other current Hg(2+) sensing methods. It is expected that our strategy can be exploited for monitoring the pollution of water environments and the safety of potentially contaminated food.
authors.affiliation: Hybrid Materials Interfaces Group, Faculty of Production Engineering and Center for Environmental Research and Sustainable Technology (UFT) University of Bremen, D-28359 Bremen, Germany. wei@uni-bremen.de.
authors.forename: Qing
authors.initials: Q
authors.lastname: Li
authors.forename: Monika
authors.initials: M
authors.lastname: Michaelis
authors.forename: Gang
authors.initials: G
authors.lastname: Wei
authors.forename: Lucio
authors.initials: L
authors.lastname: Colombi Ciacchi
mesh_terms: D052157:Aptamers, Nucleotide / Q000737:chemistry*; D001483:Base Sequence; D015374:Biosensing Techniques / Q000379:methods; D002413:Cations, Divalent / Q000032:analysis; D060766:Drinking Water / Q000032:analysis*; D006108:Graphite / Q000737:chemistry; D057230:Limit of Detection; D008628:Mercury / Q000032:analysis*; D018625:Microscopy, Atomic Force / Q000379:methods*; D008958:Models, Molecular; D013941:Thymine / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D052157:Aptamers, Nucleotide; D002413:Cations, Divalent; D060766:Drinking Water; D014874:Water Pollutants, Chemical; D006108:Graphite; D008628:Mercury; D013941:Thymine