Washing-Free Heterogeneous Immunosensor Using Proximity-Dependent Electron Mediation between an Enzyme Label and an Electrode

다국어 초록 (Multilingual Abstract)

<P>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 <SMALL>l</SMALL>-ascorbic acid by <SMALL>l</SMALL>-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.</P><P><B>Graphic Abstract</B>
<IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancham/2014/ancham.2014.86.issue-9/ac5006487/production/images/medium/ac-2014-006487_0009.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ac5006487'>ACS Electronic Supporting Info</A></P>