An ultra-sensitive capacitive biosensor is utilized to monitor trace amounts of toxic bacterial-related contaminants. The gold transducer surface covered with a self-assembled monolayer (SAM) of alkylthiols is modified by immobilizing a biomolecule, e.g. antibodies directed towards the contaminant, covalently to reactive head groups of the SAM. A capacitance decrease is then registered and measured when target molecules bind selectively to the sensor surface. The sensor is mounted in a flow injection system, and a continuous stream of liquid is passed over the sensing surface. After binding and washing, the registration takes place prior to the forced dissociation of the affinity complex by a regeneration solution and the system is reconditioned for still another assay. The assays are sensitive. In several cases a detection limit in the order of 10-18 moles per liter has been achieved, and quantification to at least 10-17. The type of analytes that have been monitored by this technique are e.g. endotoxin, endotoxins, host cell proteins from a preparation of an expressed cloned product, plasmids, protein A. The assay system is sensitive and is possible to use in continuous monitoring and it may therefore be of interest for developing PAT (process analytical techniques).

Supervisors: Bo Mattiasson, Martin Hedström
Researchers: Ally Mahadhy, Alvaro Gutierrez