title: Sub-attomolar detection of cholera toxin using a label-free capacitive immunosensor.
abstract: A label-free immunosensor for the direct detection of cholera toxin (CT) at sub-attomolar level has been developed based on potential-step capacitance measurements. Anti-CT antibody was adsorbed on gold nanoparticles (AuNPs) incorporated on a polytyramine-modified gold electrode. The concentration of CT was determined by detecting the change of capacitance caused by the formation of antibody-antigen complexes. By using AuNPs adsorbed to the sensing surface, the signal was dramatically increased leading to a significantly more sensitive assay. In fact, under optimum conditions the immunosensor could detect CT concentration with a limit of detection of 9 x 10(-20)M or 0.09 aM, with a dynamic range between 0.1 aM and 10 pM. Good analytical reproducibility could be obtained by injecting CT up to 36 times with an RSD of 2.5%. In addition, good performance of the developed immunosensor was achieved when applied to turbid water samples collected from a local stream that were spiked with CT.
authors.affiliation: Trace Analysis and Biosensor Research Center, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand.
authors.forename: S
authors.initials: S
authors.lastname: Loyprasert
authors.forename: M
authors.initials: M
authors.lastname: Hedström
authors.forename: P
authors.initials: P
authors.lastname: Thavarungkul
authors.forename: P
authors.initials: P
authors.lastname: Kanatharana
authors.forename: B
authors.initials: B
authors.lastname: Mattiasson
mesh_terms: D000907:Antibodies, Bacterial / Q000737:chemistry* / Q000276:immunology; D015374:Biosensing Techniques / Q000295:instrumentation*; D002772:Cholera Toxin / Q000032:analysis* / Q000737:chemistry / Q000276:immunology; D003217:Conductometry / Q000295:instrumentation*; D025802:Electric Capacitance; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007118:Immunoassay / Q000295:instrumentation*; D008832:Microchemistry / Q000295:instrumentation*; D036103:Nanotechnology / Q000295:instrumentation*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D000907:Antibodies, Bacterial; D002772:Cholera Toxin