HIGH-SENSITIVITY BIOSENSOR BASED ON LB TECHNOLOGY AND ON NANOGRAVIMETRY

Quartz-resonator nanobalances are utilized here as effective transducers capable of determining with high sensitivity the mass changes due to specific protein-protein, antigen-antibody and ligand-receptor binding or self-assembly of functional complexes. The resulting highly sensitive biosensor is based on two quartz resonators (one active and the second used as a reference) and on Langmuir-Blodgett (LB) protein monolayers. The electronics are composed of two separate blocks, one designed to acquire by a personal computer the data coming from the other card, a 24-bit digital counter directly connected to the two oscillators. In the case of immunosensor application, the active and reference oscillators are covered respectively by antibodies specific to a given antigen and by antibodies non-specific to the antigen, in order to discriminate the physical adsorption effects. Deposition of antibody monolayers is performed by the LB technique in a surface pressure range of 20-35 mN m(-1) onto gluteraldehyde pre-treated quartz resonators. A thermal treatment of the antibody layer up to 150 degrees C results in the reorganization of the film, and significantly improves the sensitivity and the properties of the immunosensor.