Study Of The Mount Amplified Piezoelectric Biosensor Based On Enzymatic Catalysis

Use of biosensing techniques to detect the meaningful bio-markers for the accurate and rapid diagnosis of clinical diseases as well as for the field screening and mass monitoring of the epidemic diseases has been a novel, attractive and hot topic in the current medical studies. Piezoelectric TSM immunosensing technique, which incorporates high sensitivity of piezoelectric response and high specificity of antibody-antigen immunoreaction, is sensitive to multiple signals such as the surface mass, and the density, viscosity, conductivity, and dielectric effect of solution. It presents some outstanding advantages including desirable simplicity, high sensitivity, rapid response, wide detection range, effective cost, real-time digital output, and free from tracer labeling and sample purification etc. This technique may breakthrough some bottlenecks of the traditional analytical methodologies, showing an attractive future of potential applications in the biochemical diagnosis of clinical diseases. In this paper, on the one hand, the diagnostic piezoelectric immunosensores are fabricated by nanoparticle-enhanced bio-molecular modification techniques. On the other hand, based on the emzymatically amplified system and the dynamic analysis technique of the piezoelectricity, a series of piezoelectric immunosensoes for the diagnosis of some clinical diseases including liver cancer, Schistosomiasis etc. have been developed. The detailed matericals are shown as foolows:(1) The magnetic nanoparticles were used as the mediator of the immunoreaction to sense the human thymidine kinase. The horseradish peroxidase labeled with antibody was then bound to the hTK by competitive pattern and was used as a biocatalyst for the oxidative precipitation of 4-chloro-1-naphthol by H2O2 to yield the insoluble product benzo-4-chlorohexadienone, amplifying the mass sensing of antigen-antibody interaction. The amount of the precipitate accumulated on the quartz crystal was controlled by the antigene concentration. The hTK can be linearly determined in the range of 0.23～5.0 ng/mL and the detection limit reaches as low as 0.12 ng/mL, the sensor can differentiate the liver cancer from the clinical samples availably.(2) A mercapto schistosoma-japonicum antigen was self-assembled onto the quartz crystal surface via an Au nanoparticle mediator monolayer to sense the schistosoma-japonicum antibody (SjAb). And the horseradish peroxidase labeled protein A conjugate which was bounded to the SjAb by a"sandwich"format was used as a biocatalyst for the oxidative precipitation of 4-chloro-1-naphthol by H2O2 to yield the insoluble product benzo-4-chlorohexadienone, resulting in an amplified mass sensing of antigen-antibody interaction. The amount of the precipitate accumulated on the quartz crystal is controlled by the antibody concentration. The SjAb can be linearly determined in the range of 10～100 ng/mL and the detection limit reaches as low as 5 ng/mL.(3) The H2O2-mediated enlargement of Au nanoparticles (AuNPs) and the growth mechanism were described. In addition to the deposition of gold on the NP faces, the formation of nanocrystalline clusters at the intersection of the faces is observed. The detachment of the latter nanoclusters provides additional seeds for the deposition of gold. The biocatalyzed generation of H2O2 in the presence of O2/glucose and glucose oxidase enabled the development of a piezoeletric biosensor for glucose. The glucose can be linearly determined in the range of 6.1×10-6 M～1.2×10-4 M and the detection limit reaches as low as 5.2×10-7 M.