Based On The Conductive Nanoparticles And Preparation Of Phytic Acid Self-assembled Biosensor And Its Performance Study

In recent year, nanotechnology got further applications in theelectrochemical biosensors. The immobilization of enzyme is one of themost important technologies in the process of the construction of theelectrochemical biosensor. So far, a lot of reports showed that thestructure and properties of carrier material influence the immobilizing ofenzyme for all kinds of performance in a large extent. So it attractsmany researchers to study of carrier material.Nano materials have the advantages of high specific surface,adsorption ability, more surface activity center and so on. If weintroduce them into the biosensors, they can immobilize more enzymeson the surface so that to increase the adsorption quantity of enzymeand stability, effectively improve the sensitivity and the performance ofbiosensors. And it can promote the transportation of electrons betweenthe enzyme and the electrode. Also can keep the activity of enzymeand make more electrochemical biosensors with excellentperformance.Phytic acid （also called Inositol hexakisphosphoric，IP₆）,is a kindof naturally specie. It presents unique benefits such as biocompatibility,nontoxicity, and “green” to the environment. It is the principal storageform of phosphorus in many plant tissues, especially in wheat bran andseeds. IP₆has six phosphates to react easily with the enzyme. Hence,IP₆should be used to capture enzyme as molecular binder instead ofemploying a polymeric binder. These properties constitute favorableconditions for enzyme or protein immobilization. Quite recently, IP₆molecules have been found to self-assemble into a micelle spherestructure through some phosphates sitting inside and some freephosphates remaining outside of the sphere under boiling condition.This unique structure is very similar to the structure of biological membranes, in which the constituent lipids are arranged in thetail-to-tail configuration with the hydrophilic head groups towardoutside and proteins are adsorbed onto the surface of or imbeddedinto the layers. Therefore, botanical IP₆micelle is expected to offer apromising template for enzyme-based biosensor fabricationbecause of its satisfying biocompatibility and well-distribution in waterfor easy spread onto substrate.In this paper, we used green material phytic acid combined withnanoparticles by self-assembly technology, prepared the following twothird generation of biosensors for the detection of hydrogen peroxide:（1） This chapter introduces a kind of biosensors for the detectionof hydrogen peroxide （H₂O₂） with easy fabrication; throw after usedand low cost. Through the self-assembly technology, hemoglobin （Hb）was successfully fixed in the gold nanoparticles after gold nano seedsgrew in the mixture of IP₆and HAuCl4·3H2O on ITO electrode. Throughthe UV-VIS absorption spectra and electrochemical method, showedthat the gold nanoparticles still have excellent biocompatibility and theability of transferring electrons, and Hb on the surface kept goodbiological activity, and realized the direct transfer of electrons. Throughthe further studies, the biosensor Nafion/Hb/Au/ITO for detection ofH₂O₂has a linear range from3×10^-5 M to8.9×10^-4 M and8.9×10^-4 M to2.39×10^-3 M with the detection limit of6×10?6M （at the ratio of signal tonoise, S/N=3）. The apparent Michaelis-Meten constant （） wasestimated to be0.0995mM.On the same condition, the detection ofthe same concentration of H₂O₂,the relative standard deviation （R.S.D）was about1.73%; The biosensor is simple, low cost, throw after used, andhas a wide range of detection, short response time and better stabilityand reproducibility.（2） Another biosensor for hydrogen peroxide （H₂O₂） based onIP₆micelle, ZnO nanoparticals and hemoglobin through self-assembly technique was fabricated. It was simple, throw after used and lowcost.First, ITO was alternate dipped into the IP₆micelles （IP₆m）, ZnOnanoparticals and hemoglobin （Hb） successfully. Through the UV-VISabsorption spectra and electrochemical method,the results showedthat the IP₆micelle and ZnO nanoparticles played biological affinity forHb,provides a good environment for Hb, and keep the original activityof Hb, realized the direct transfer of electron between Hb and theelectrode. the biosensor Nafion/Hb/ZnO/IP₆m/ITO for detection of H₂O₂has a linear range from3×10^-6 M to5.523×10^-3 M with the detection limitof5×10-7M （at the ratio of signal to noise, S/N=3）. The apparentMichaelis-Meten constant （） was estimated to be1.84mM.On thesame condition, the detection of the same concentration of H₂O₂,therelative standard deviation （R.S.D） was about3.4%; The biosensor issimple, low cost, throw after used, and has a wide range of detection,short response time and better stability and reproducibility.（3） Supplement: Nucleic-acid aptamer is single oligonucleotideclips with high affinity and high specificity of target molecules,compared with conventional recognition molecules （such asantibodies and enzyme）, it has some advantages. Here we prepared alabel-free aptamer electrochemical biosensor for the detection ofadenosine. Firstly, put the cleaned gold electrode to the mixture ofcapture probe and the aptamer, then, immersed with6-MCH to get theMCH/Aptamer-Capture/Au electrode electrochemical biosensor. Itcan specifically identify the adenosine for the detection linear rangefrom1×10^-6 M to2.5×10^-4 M with the detection limit of0.1μM. On thesame condition, the detection of the same concentration ofadenosine,the relative standard deviation （R.S.D） was about2.0%; Thebiosensor of adenosine has a high sensitivity, a wide detection range,production is simple, low cost, and has good selectivity andreproducibility, it has a good development prospect in electrochemical biosensors.