Antibodies amperometry

In amperometry, the current produced by the oxidation or reduction of an electroactive analyte species at an electrode surface is monitored under controlled potential conditions. The magnitude of the current is then related to the quantity of analyte present. However, as both antibody and antigen are not intrinsically electroactive, a suitable label must be introduced to the immunocomplex to promote an electrochemical reaction at the immunosensors. In this respect, enzyme labels including the... 

In amperometry, we measure the electric current between a pair of electrodes that are driving an electrolysis reaction. One reactant is the intended analyte and the measured current is proportional to the concentration of analyte. The measurement of dissolved 02 with the Clark electrode in Box 17-1 is based on amperometry. Numerous biosensors also employ amperometry. Biosensors8-11 use biological components such as enzymes, antibodies, or DNA for highly selective response to one analyte. Biosensors can be based on any kind of analytical signal, but electrical and optical signals are most common. A different kind of sensor based on conductivity—the electronic nose —is described in Box 17-2 (page 360). 

Interleukin 6 (IL-6) Sandwich immunoassay using HRP-labelled antibody with TMB substrate FLA, amperometry... 

Immunoassays, electrochemical — A quantitative or qualitative assay based on the highly selective antibody-antigen binding and electrochemical detection. Poten-tiometric, capacitive, and voltammetric methods are used to detect the immunoreaction, either directly without a label or indirectly with a label compound. The majority of electrochemical immunoassays are based on -> voltammetry (-> amperometry) and detection of redox-active or enzyme labels of one of the immunochemical reaction partners. The assay formats are competitive and noncompetitive (see also -> ELISA). 

Instead of immobilizing the antibody onto the transdueer, it is possible to use a bare (amperometrie or potentiometrie) eleetrode for probing enzyme immunoassay reactions (42). In this case, the eontent of the immunoassay reaction vessel is injected to an appropriate flow system eontaining an eleetroehemical detector, or the electrode can be inserted into the reaetion vessel. Remarkably low (femtomolar) detection limits have been reported in eoimeetion with the use of the alkaline phosphatase label (43,44). This enzyme eatalyzes the hydrolysis of phosphate esters to liberate easily oxidizable phenohe produets. 

Since antibody-antigen binding does not produce a detectable signal by itself, several techniques involve a tag such as an enzyme, radioisotope, or fluoroph-ore to monitor the reaction with a variety of optical and electrochemical detectors. One group of detectors generally uses fluorescence and chemiluminescence while another employs amperometry and potentiometry. Electrochemical immunoassays are emergent alternatives to existing immunochemical... 

Figure 10.345 Separation of monosaccharides of a standard (a) and a monoclonal antibody (b). Separator column CarboPac PA1 eluent 16 mmol/L NaOH flow rate 1 mt/min detection pulsed amperometry on a gold working electrode peaks fucose (1), rhamnose as...

Fig. 9-219. Separation of monosaccharides of a standard (a) and a monoclonal antibody (b). - Separator column CarboPac PAl eluant 16 mmol/L NaOH flow rate 1 mL/ min detection pulsed amperometry on a gold working electrode peaks flicose (1). rhamnose as internal standard (2). galactosamine (3), mannosamine as internal standard (4), glucosamine (5). galactose (6), glucose (7). and mannose (8). (taken from [369]).

Lithographic gold electrodes were modified in two ways (1) formation of a SAM of the bipodal alkanethiol DT2 followed by covalent linking of whole anti F. tularensis antibody and (2) direct chemisorption of F. tularensis antibody fragments Francisella tularensis Step and sweep amperometry 4.5 ng/mL for the lipopolysac-charide antigen isolated from F. tularensis and 31 bacteria/ mL for the F. tularensis bacteria/- Dulay et al. (2014)... 

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