Rapid flow-injection sandwich-type immunoassays of proteins using an immobilized antibody reactor and adenosine deaminase-antibody conjugates

A raptd flow-mlectron sandwtch enzyme immunoassay suitabIe for the direct determmatron of proteins m btoIogtcaI sampIes rs described.. ‘The proposed system utihzes fugfify active adenosme deammase-antibody coqugates m conlunctron with a flow-through unmunoreactor and an ammomum ion-sefectrve potentrometnc detector. After appropnate sampfe/.reagent mlectton steps, the enzyme actrvtty bound to the reactor 1s measured by dtvertmg a continuously flowmg stream of substrate (adenosme) through the packed tmmunocolumn and detectmg hberated ammomum ions downstream wtth a tubular ammonium ion-selective electrode. The bound enzyme activity 1s drrectIy proportional to the concentration of analyte m the ongmaI sampIe. By usmg non-eqmhbnum flow-rates of sample and reagent slugs, a smgle protein assay takes less than 12 mm, mcludmg regeneration of the reactor. The proposed method 1s shown to be selecttve, reproducible and capable of determining accurately the model protem (human IgG) at sub-pg ml-’ concentrations.