Study For Sandwich Immunesensors Based On Inorganic Nanomaterials As Labels

The biosensor can determine the concentrationof biological materials by using electrical signals to denote it. It integrates the knowledge of medicine, chemistry, biologyand other disciplines. Becauseof its low cost, simple preparation and high sensitivity, it is widely used in medicaltesting, environmental monitoring and other fields. The current immunosensor can determine the concentration of biological molecules through reading the changes of the current value before and after the immune response. It can also be used to the online vivo analysis. The most crucial point of the construction of immunosensor is how to immobilize biological molecules to the electrode surface stably and actively, and also get more catalyst signals.Due to their large surface areas, good adsorption capacities, biocompatibilities, electrical catalytic activities and other advantages, nanomaterials have been widely used in recent years of studies. This is based on these advantages of nano-materials. We uses hollow platinum nanospheres, three-dimensional clusters of gold nanoparticles, gold nanoparticles/silica composite nano-materials, nano-gold/chitosan composite film, multi-walled carbon nanotubes and other nano-materials to construct a series of excellent performed sandwich immunosensors. Transmission electron microscopy (TEM) and electrochemical technology are also usedto characterizethe preparation process of the electrode, the optimization process and the properties. The main work is carried out as follows:1. The Study of Sandwich Immunosensors which Based on Gold-clusters as Substrates and Glucoseoxidase Modified Pt Hollow Nano-clusters as the Indicators.The hollow microspheres platinum nanoparticles are deoxidized with sodium borohydrides. Carboxyl ferrocenes are used as the electron mediator. When using carboxyl ferrocenes as the electron mediator, the catalytic signal of the enzyme glucose oxidaseis performed better than other enzymes. The solid matrixis using the PC templateto electrode posit gold chlorideacidson glassy carbon electrodes. The gold nanoparticle clusters cancontain more protein molecules. It is proved that the sensitivity of immunosensor is thus improved. Using the sensor to detect human chorionic gonadotropin, the linear range is from 0.06 mIU·mL-1 to 200 mIU·mL-1. and the detection limitis down to 0.01 mIU·mL-1. In addition, the immunosensor has good selectivity, reproducibility and stability.2. The Study of Sandwich Immunoassay Sensor Based on Multi-walled Carbon Nanotubes in Situ Reduction of Gold for the Tag Positive Nanoparticles.The author labels glucose oxidase and antibodies as the second antibody by using the PEI in situ to reduce the positively charged gold nanoparticles on multi-walled carbon nanotubes. The first antibody of the solid matrix is the composite film of layers of chitosan and gold nanoparticles electrode posited on the glassy carbon electrode. Thus CEA sandwich immunosensor is prepared. Using the composite film of chitosan and gold nanoparticles as the first antibody of the solid matrix, it not only has the strong adsorption capacity and electron transport capacity of gold nanoparticles, but also has a good film forming capacity and biocompatibility of chitosan. The markers of the second anti-body is using the PEI in situ to reduce the positively charged gold nanoparticles on multi-walled carbon nanotubes, while the isoelectric point of the glucose oxidase and carcinoembryonic antibody molecules is less than 5.0. When the pH is higher than 5.0, they are both negative charged.so you can mark more enzymes and antibody protein molecules through the electrostatic interaction. By comparing the catalysis of the carbon nanotube/ glucose oxidase, gold nanoparticles/glucose oxidase, it is proved that multi-walled carbon nanotubes and nano-gold complexes are more effictivethan glucose oxidase in synergistic catalysis. And the sensitivity of immunosensor is highly improved. The detection of CEA is from 0.4 to 20 ng·mL-1, and the detection limit is 0.05 ng·mL3. The Study Based on the Hollow Nanoparticles Platinum Microspheres Labeled Enzyme-linked Antibody to Amplify the Signal of Sandwich Immunosensors.This study proposes the hollow nanoparticles platinum microspheres labeled enzyme-linked antibody to amplify the signal of sandwich immunosensors. Using sodium borohydride reduction to prepare hollow nanoparticles platinum microspheres, and then connect the mand the horseradish peroxidase with secondary antibody particles to amplify the current signal. The solidmatrix is based on the nano-gold and silica complex to absorb the biological protein molecules. It increases the amount of immobilized antibody, maintains its biological activity, and also improves the electron transfer rate. Comparing the hydrogen peroxide electrocatalytic activity, the hollow nano-platinum is better than the platinum nanoparticles on solid. The results also show the increased sensitivity of the electrode. The linear range of the electrode is from 0.02 to 120 ng-mL-1, and the detection limit is 12 pg-mL-1. the result shows a wider linear range and a lower detection limit.