title: Aptamer-based potentiometric measurements of proteins using ion-selective microelectrodes.
abstract: We here report on the first example of an aptamer-based potentiometric sandwich assay of proteins. The measurements are based on CdS quantum dot labels of the secondary aptamer, which were determined with a novel solid-contact Cd2+-selective polymer membrane electrode after dissolution with hydrogen peroxide. The electrode exhibited cadmium ion detection limits of 100 pM in 100 mL samples and of 1 nM in 200 microL microwells, using a calcium-selective electrode as a pseudoreference electrode. As a prototype example, thrombin was measured in 200 microL samples with a lower detection limit of 0.14 nM corresponding to 28 fmol of analyte. The results show great promise for the potentiometric determination of proteins at very low concentrations in microliter samples.
authors.affiliation: Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, USA.
authors.forename: Apon
authors.initials: A
authors.lastname: Numnuam
authors.forename: Karin Y
authors.initials: KY
authors.lastname: Chumbimuni-Torres
authors.forename: Yun
authors.initials: Y
authors.lastname: Xiang
authors.forename: Ralph
authors.initials: R
authors.lastname: Bash
authors.forename: Panote
authors.initials: P
authors.lastname: Thavarungkul
authors.forename: Proespichaya
authors.initials: P
authors.lastname: Kanatharana
authors.forename: Ernö
authors.initials: E
authors.lastname: Pretsch
authors.forename: Joseph
authors.initials: J
authors.lastname: Wang
authors.forename: Eric
authors.initials: E
authors.lastname: Bakker
mesh_terms: D052158:Aptamers, Peptide / Q000737:chemistry*; D015374:Biosensing Techniques / Q000295:instrumentation / Q000379:methods*; D019187:Cadmium Compounds / Q000737:chemistry; D007118:Immunoassay; D017736:Ion-Selective Electrodes; D011199:Potentiometry / Q000295:instrumentation / Q000379:methods*; D011506:Proteins / Q000032:analysis* / Q000737:chemistry; D045663:Quantum Dots; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013194:Staining and Labeling; D013440:Sulfides / Q000737:chemistry; D013917:Thrombin / Q000032:analysis / Q000737:chemistry
chemical_list: D052158:Aptamers, Peptide; D019187:Cadmium Compounds; D011506:Proteins; D013440:Sulfides; C034939:cadmium sulfide; D013917:Thrombin