Immunosensors based on supported lipid membranes, protein films and liposomes modified by antibodies

The comparison of physical properties, sensitivity and reproducibility of v arious detection parameters of several newly developed affinity biosensors for determination of human IgE and herbicide 2,4-D is presented. The protei n film based biosensors were composed of antibody (swine anti-human IgE (Q- SwaHU/IgE) or monoclonal antibody (MAb) against herbicide 2,4-D) attached t o thin gold support through cysteamine or cysteamine-bovine serum albumin. The antigen (Ag)-antibody (Ab) interaction was detected by measurement of c onductivity. The detection limit for human IgE was similar to 1 nM, however , the sign of response depends on the method of antibody attachment to the gold support. This type of design and detection method was not appropriate for detecting small molecules, like 2,4-D. In the case of metal (stainless steel or gold) supported lipid films (s-BLM), the sensor was constructed by means of binding of avidin-modified antibody to s-BLM contained biotinylat ed phospholipids. Measurement of electrical capacitance, C, and elasticity modulus in direction perpendicular to the membrane plane, E-perpendicular t o, allowed to detect the Ag-Ab reaction, that resulted in decrease of C and increase of E-perpendicular to. Most reproducible results have been obtain ed with lipid films supported on thin gold layers with detection limit of d etermination of 2,4-D similar to 1 mu M. The best reproducibility and sensi tivity (0.1-1 nM) have been obtained in liposome immunoassay. The Ag-Ab rea ction was monitored by means of measurement the changes of ultrasound veloc ity in liposome suspension. (C) 1999 Elsevier Science S.A. All rights reser ved.