LB-BASED PAB IMMUNOSYSTEM - ACTIVITY OF AN IMMOBILIZED UREASE MONOLAYER

A new configuration of the biosensing system named potentiometric alte rnating biosensor (PAB) is analysed. The system is based on an Si/SiO2 /Si3N4 transducer and allows the monitoring of several biochemical eve nts, such as immunoenzymatic reactions and cell metabolism. The utiliz ation of PAB as immunosensor implies the possibility of using a modifi ed Langmuir-Blodgett (LB) technique for the production of an antibody monolayer. In the first stage the activity of an immobilized LB monola yer of an enzyme (urease) is monitored in order to simulate the final step of the immunoenzymatic assay; subsequently, the enzymatic activit y of an immobilized monolayer of antigen (MAb) after incubation with a ntibodies labelled with urease is monitored. Vacuum silanization with glycidoxypropyltrimethoxysilane (GOPTS) is utilized to ensure covalent binding of the protein LB monolayer to a glass substrate. The analysi s with PAB of films thus prepared is preceded by characterization of t he layer by means of nanogravimetric and spectrophotometric techniques , which yield useful information on the surface density and activity, respectively. Furthermore, the operative lifetime of the enzyme layer within a period comparable to the standard time of an immunoassay has been studied.