AN AUTOMATED ELISA SYSTEM USING A PIPETTE TIP AS A SOLID-PHASE AND A PH-SENSITIVE FIELD-EFFECT TRANSISTOR AS A DETECTOR

A fully automated ELISA system was constructed using a pipette tip as a solid phase, urease as a detecting enzyme, and a pH-FET as a detecto r of urease activity. The inner wall of the end part of a pipette tip was used as a solid phase, and the urease activity of the conjugate, c aptured after a two-step immunoreaction, was measured by coupling the pipette tip with the pH-FET in a pH-measuring cell. Full automation of the ELISA system was achieved by using a disposable reagent cartridge and three pipetters for all mechanical operations, including sample d ilution and B/F separation. This system can treat 60 samples per hour with an assay time of 21 min for all assay configurations. The system was applied to two-step sandwich assays for AFP, CEA, HBsAg, and HBsAb , a two-step competition assay for HBcAb, and a second antibody assay for HTLV-1 Ab.