Study On The Preparation Of Giant Magnetoimpedance Biosensor Based On Magnetic Beads

Giant magneto-impedance(GMI)sensor is a new type of sensor based on amorphous magnetic materials with highly sensitive giant magneto-impedance effect. GMI effect was discovered firstly in 1992 by Japanese professor Maori of Nagoya University.The effect is that AC impedance(Z)of some amorphous magnetic materials with soft magnetic properties significantly changes with the external magnetic field(H).The sensitivity(△Z/Z%/ H)reached 40～100%/Oe.Since GMI effect has been found,tremendous prospects for the application attracted a lot of attention of scientific workers,and a lot of study has been done both on experiment and on theory.GMI effect on the giant magneto-impedance sensor has the following characteristics:high sensitivity,need low extemal magnetic field,good stability,good linearity,long life,low cost,easy to miniaturization.In this paper,we used giant magneto-impedance materials with larger GMI effect, to develop the probe with the requirements of biosensors,And designed a small,stable GMI measurement system.We developed a integrated,high sensitive GMI biosensor that can carry out quantitative analysis.As one of application of GMI biosensor,for using the sensors in the analysis of biological immunity,the surface modification of the magnetic particles was studied.We used the amino-terminal bead as matrix,to fix BSA protein.We proposed to use new type of magnetic particles in this giant magneto-impedance biosensors,as markers of sandwich immune response, and at the same time it can captured and enriched the biomolecule in the magnetic separation.If the development of the GMI biosensors is successful,its high sensitivity may meet the various requirements of the study of the life phenomenon by the molecular level.It can be used on the study of the structure and function of protein,the interaction of DNA and protein,the interaction of drug and biological macromolecules,analysis of the fatal disease biomarker,and other fields.It may have important significance and practical application value.This paper studied as follows:1.We developed a non-linear non-diagonal GMI sensor,the pickup coil parameters, including the length,the diameter of coil tube,the number of turns as well as the diameter of the coil wire,in relation to the sensor sensitivity are investigated. The results showed that the sensitivity is directly proportional to the ac driving frequency,and the number of turn density of the pick-up coil.With smaller wire diameter,smaller coil diameter and smaller coil length,the sensor sensitivity improves.Using Co-based glass-coated amorphous microwires 23μm in diameter as sensing element,the sensitivity is up to 2.3mV/mGs(2.3mV/Am^-1).2.We designed and produced a measurement system of GMI biosensor.Using the phase sensitive detection method,the output signal in variation with the external magnetic field was converted to a DC signal.The measuring range of the field is±400 mGs(±400Am^-1).The linearity coefficient is 0.9999,the sensitivity is 5.46 mV/mGs(5.46mV/Am^-1),the resolution response is up to 10^-8T.By using a digit circuit,the signal can be converted to the digital signal.3.In order to conjunct the NdFeB with active -NH₂ groups,the surface modification of NdFeB permanent magnetic particles by 3-aminopropyltriethoxysilane(APES)was studied in this paper.The surface function groups of the modified NdFeB magnetic particles were investigated by FT-IR,DSC-TG,TEM and magnetic hysteresis loop measurements,and the experimental results showed that magnetic particles effectively modified by amino-silane were obtained under the optimum experimental conditions.We fixed bovine serum albumin(BSA)to -NH2 end of magnetic particles,choose different reaction medium,optimize the reaction conditions to reduce the nonspecific adsorption of protein and the magnetic particles,increased coupling efficiency,after coupling,separated the reaction solution and obtained the upper portion and measured the OD₂₈₀values,judgement coupling efficiency.The results show that:under the proper reaction conditions(ionic strength,pH,time), using glutaraldehyde fix protein has higher coupling efficiency.This experiment will help to develop more convenient and efficient methods to use functioned magnetic particles to separate and detect protein by GMI biosensor.