Washing-free heterogeneous immunosensor using proximity-dependent electron mediation between an enzyme label and an electrode.
Washing processes, essential in most heterogeneous labeled assays, have been a big hurdle in simplifying the detection procedure and reducing assay time. Nevertheless, less attention has been paid to washing-free heterogeneous labeled assays. We report a purely washing-free immunosensor that allows fast, sensitive, and single-step detection of prostate-specific antigen in serum with low interference. Proximity-dependent electron mediation of ferrocenemethanol (Fc) between an indium-tin oxide (ITO) electrode and a glucose-oxidase (GOx) label allows us to discriminate between a bound and an unbound label: a bound label offers faster electron mediation than an unbound one. The electrooxidation of Fc at a low applied potential (0.13 V vs Ag/AgCl) and a low electrocatalytic ITO electrode and the oxidation of l-ascorbic acid by l-ascorbate oxidase minimize the effect of the interfering species. With a high concentration of glucose (200 mM), the signal and background levels are hardly dependent on the glucose-concentration variation in the sample. The washing-free immunosensor can detect a concentration of ca. 1 pg/mL for mouse IgG in phosphate-buffered saline and a concentration of ca. 10 pg/mL for prostate-specific antigen spiked in female serum after an incubation period of 10 min. The concentrations measured with actual clinical serum samples are in good agreement with the concentrations measured with a commercial instrument, which renders the washing-free heterogeneous immunosensor appealing for practical use.
Department of Chemistry and Chemistry Institute for Functional Materials, Pusan National University , Busan 609-735, Korea.
Gorachand
G
Dutta
Sinyoung
S
Kim
Seonhwa
S
Park
Haesik
H
Yang
D015374:Biosensing Techniques; D004566:Electrodes; D004583:Electrons; D004798:Enzymes / Q000737:chemistry*; D005947:Glucose / Q000737:chemistry; D010084:Oxidation-Reduction; D017430:Prostate-Specific Antigen / Q000097:blood
D004798:Enzymes; D017430:Prostate-Specific Antigen; D005947:Glucose