Increase ELISA Sensitivity with the Signal Amplification AMP'D® Technology
The AMP'D® ELISA Signal Amplification system is designed to replace traditional alkaline phosphatase (AP) substrates, such as pNPP (p-Nitrophenyl phosphate), with a combination substrate and amplifier system that results in greater sensitivity when compared to a traditional substrate ELISA.
In a conventional detection system, enzyme bound to the microtiter plate interacts directly with the substrate producing a color change where the resulting absorbance is directly proportional to the amount of captured analyte. In the Amp’d ELISA system, bound AP converts a substrate that is utilized in a second enzyme reaction system which is initiated by addition of the amplifier reagent. It is this amplification step that allows for greater (amplified) color production at lower analyte concentrations resulting in an increase in assay sensitivity.
In the Amp’d ELISA system, the critical substrate component, NADPH, is added to wells containing AP and the AP reduces to NADH via release of a phosphate group. This reaction is allowed to proceed for an amount of time with the accumulated NADH being proportional to the amount of analyte/bound AP-conjugate. Upon the addition of the reconstituted amplifier reagent, this first reaction is quenched and the NADH feeds a second redox enzyme system. Here diaphorase utilizes NADH to reduce the iodonitrotetrazolium salt into formazan (purple color) producing NAD+. A counter enzymatic reaction then occurs where the NAD+ is reduced to NADH while ethanol is oxidized to acetaldehyde via alcohol dehydrogenase. This set of enzymatic reactions is also allowed to proceed for a period of time, recycling the NADH thus amplifying the original AP/substrate reaction. The resulting color intensity is ultimately proportional to the amount of bound analyte.