Study Of Superoxide Anion Related Biosensing Technologies

Biosensing technologies based on the biomaterials recognition and the chemical signal magnification function take the advantages of high-sensitivity, nice-selectivity, and simple-operation and have the potential application in clinic diagnoses, biological analysis, environmental monitoring and so on. Since the superoxide anion (O2-?) is closely related to many kinds of human diseases and body aging, it have been attacted wide attentions. This research aimed to develop the fluorescent and piezoelectrical methods for the analysis of superoxide anion (O2-?) and materials correlative with life science, which is meaningful for the development of new biosensing technologies and bioassays. The details are summarized as following:1. An enzymatic assay for superoxide anion (O2-?) has been developed by using a new H2O2 fluorescent probe, 3', 6'-bis(pinacolatoboron)fluoran, as the fluorescent substrate of superoxide dismutase (SOD). The superoxide anion in xanthine/xanthine oxidase system (XA/XOD) was catalyzed by SOD to form H2O2 product, resulting in a clear increase in the fluorescence intensity of the fluorescent probe. The experimental results show that there is a linear relationship between the fluorescence intensity and the concentration of superoxide anion in the range of 2.4×10-7 ~ 1.5×10-5 mol/L, which indicate the high sensitivity and detection ability of this method.2. With the catalysis of magnetic-Au complex nanoparticles (NPs), a new mass amplified piezoelectrical sensor for xanthine based on reduction of AuCl4- on NPs was developed. The magnetic-Au nanoparticles were obtained by electrostatic combining Au nanoparticles with magnetic nanoparticles (MNPs) which were modified with amino-groups. With the help of a permanent magnet, the magnetic-Au nanoparticles formed were attached to the surfaces of quartz crystal, and these magnetic-Au nanoparticle seeds acted as catalysts for reduction of AuCl4- by O2- in the XA/XOD system, resulting in the enlargement of the particles and the enhanced mass response. The piezoelectrical sensor can determine xanthine in the range of 5.0×10-8 ~ 1×10-5 mol/L with a detection limit of 2.0×10-8 mol/L. This method has high-stability, nice-sensitivity and credibility.3. Using magnetic nanoparticles as the immobiliztion materials, a new mass amplified piezoelectrical immunosensor was proposed for Schistosoma-Japonicum antibody (SjAb), which was based on the catalysis of enzyme labeled antibody (HRP-Ab). The Schistosoma-Japonicum agtigen (SjAg) was first covalently immobilized to MNPs which were modified with amine groups. The SjAg was then combined with SjAb, which can be linked with HRP-Ab for the catalyzing oxidization of 4-Chloro-1-naphthol by H2O2, resulting in the produce of deposite and the enlarged frequency change of the piezoelectric crystal. With this method, the immunosensor can detect the SjAb in the range of 10 ~ 100 ng/mL, and the detection limit reaches 8.6 ng/mL. This method ensures high sensitivity, selectivity and is expected to be used in the clinical immunoassay.