Studies On Construction Of Piezoelectric Immunosensors Based On Mixed Self-Assembled Monolayers

Pizeoelectric immunosensor are widely used for the assay of biological analytes. The advantages of this approach including their simple-design, high-sensitivity and low-cost attract substantial research efforts to the developments of some new piezoelectric immunosensors in the recent years. However, the method of immobilization, the prevention or elimination of nonspecific interactions, the reproducibility and the reusability still remain to be solved in the design and applications of these sensors. Focused on these topics, several new methods for immobilizing immuno-species to construct immunosensor have been developed in the presented paper and described as follows:(1) In the homogeneous SAM, the dense of functional groups is higher and imbedded in a two-dimensional structure and therefore less accessible for activation and/or for immobilization of antigens and resulting in higher nonspecific adsorption. A novel piezoelectric immunosensor based on mixed self-assembled monolayers (mixed SAMs) formed by short-chain amine- and carboxyl-terminated thiols has been developed to immobilize antigens onto gold electrodes for detecting antisperm antibody (AsAb) in human serum samples. There are two kinds of groups on the mixed films. Cysteamine (CE) was used as"dilution reagent"or"blocking reagent"to resist nonspecific adsorption of protein, while the–COOH of 3-mercaptopropionic acid (MPA) was activated in EDC-NHS for linkage with the SpAg. The nonspecific adsorption and the amount of SpAg immobilized on the surfaces were demonstrated to be controllable by changing the dilution ratio of MPA and CE solution during the fabrication of the mixed SAMs. In addition, analytical results of several human serum samples using the developed technique are in satisfactory agreement with those given by the enzyme-linked immunosorbent assay (ELISA) method in the concentration ranging from 32.3 to 300.0mU/ml. It means the procedure proposed in this paper is likely to have a great potential in clinical research.(2) Au nanoparticles are dense with relatively high surface area-to-volume ratio and can affect the adsorbability of the biofunctional molecules which should be immobilized on the surface of a transducer. Therefore, in contrast to the flat metal surface, Au nanoparticles allow proteins to be strongly adsorbed in large quantity...