| Giant magneto-impedance effect(GMI)has caused great interest of many international scholars due to its huge application prospect,since its discovery in 1992 by professor Gross Margin(Nagoya university,Japan).Because of its high sensitivity,fast response and other unique advantages,the GMI sensor quickly occupy a position in the field of magnetic sensor.Besides,with the development of microelectromechanical system(MEMS)technology and large scale integrated circuit technology,make the GMI sensor miniaturization,integration,intelligent and more suitable for applications in biomedical field.GMI Biosensor using magnetic nanoparticles or magnetic beads as labels,is based on the high sensitivity of GMI magnetic sensor to detect biological information of biological sample.By now,the GMI biosensor is still in its initial stage,a lot of effort is need to pay for the exploration of the application of GMI biosensor.So far the main challenges for the applications of GMI sensor in biomedical field are the manufacture of GMI sensor with high performance and some questions in testing,such as stability and reliability.There are some basic problems such as linearity,detection limit,etc.In the past years,many studies showed there was a huge difference between the experimental results and theoretical results,so it's still need a lot of research for the basic theory of GMI effect.To explore the best preparation conditions of GMI materials and manufacture high performance GMI sensor,the selection and preparation technics of GMI materials is very important,such as annealing treatment,geometry size and so on.So that,it is possible to detect biological molecules with lower concentration.E.coli O157: H7 is the main serotype of EHEC,which can cause peritonitis,hemorrhagic enteritis,cholecystitis,appendicitis and urethritis disease,and even death in some serious cases.Most outbreak of the bacteria is due to eat the pollution food,and high sensitivity check method for E.coli O157: H7 is of great significance.C-reactive protein(CRP)is synthesized by liver cells,and can be detected in human serum,cerebrospinal fluid(CSF)and other body fluids.Microbial invasion,inflammation and tissue damage can make the CRP levels rise rapidly,its only need 48 hours to reach peak value(even 3000 times higher),so the detection of CRP is of great importance for disease diagnose.Myoglobin(Mb)is a kind of red iron porphyrins protein,its function is to transport and storage of oxygen.Myoglobin exists in myocardial and skeletal muscles(molecular mass is 17800),is an old markers which cause some new view in recent years,by now Myoglobin is widely used for the early diagnosis of acute myocardial infarction(AMI).Based on the above consideration,this thesis mainly including theory research of GMI effect of meander-shaped ribbon,MEMS fabrication and performance research of GMI sensor,studies of biological molecular self-assembly membrane technology and study of detection assay for biomarkers based on GMI effect,including E.coli O157:H7?c-reactive protein and myoglobin detection.The main work is as follows:[1] From the contribution of both resistance and inductance to the impedance,GMI theoretical model of amorphous alloy ribbons with meander structure is established.Effects of the size(length and width)for the single and multi-turn meander structure,and the effects of the number of turns,spacing and meander structure on the GMI effect are investigated.The results showed that the size,turns of meander structure,spacing and meander structure have great impact both on the GMI peak and field sensitivity;[2] GMI sensor was made with the commercial Co-based amorphous ribbons.The amorphous ribbons were annealed with different ways of annealing.The amorphous alloy ribbons with different structure and size are fabricated by micro-processing technique and the GMI effect of them are studied.Besides,three layers NiFe/Cu/NiFe films GMI sensor with 10 turns was fabricated combined with micro electroplating process.The results showed that different magnetic field annealing temperature and different ways of magnetic field annealing has a significant effect on GMI effect.The effect of length and the width on GMI effect for a single structure and meander structure of is the same.Increases with the increase of length,GMI effect increased.With the increase of width,GMI effect decreased.In addition,the influence of spacing on GMI effect for meander structure is not obvious.With the increase of number of turns,GMI effect increased.But the size is too big for too many turns,it is not very ideal for biosensing test.Therefore,when the multi-turn meander structure of ribbon with transverse magnetic field annealing temperature is 380 ?,the designed smaller line width,an appropriate length and spacing is more suitable for biosensor testing.Due to the differences in the properties of electroplated NiFe films,there are differences in the properties of the fabricated thin film GMI sensor with 6 turns meander structure.Therefore,high performance thin film GMI sensor is needed in the field of biosensor testing;[3] SEM AFM,XPS were employed in investigating the relationship between the quality of self-assembled monolayers and the self-assembled conditions such as concentration of solutions,temperature,and assembly time for acquiring the optimal conditions.The optimal activating time by EDC and NHS was also studied.In addition,the relation between fixing efficiency of E.coli O157H:H7 monoclonal antibodies and the fixed conditions such as temperature,fixing time,and solution concentration was achieved.The results show the best conditions as follow: 3-mercaptopropionic acid concentration was 20 mmol/L,the self-assembly time was about 2 h,the activation time was 2 h,and the fixing conditions of E.coli O157H:H7 monoclonal antibodies was 24 h at 4?;[4] Au film element and open-surface microfluidic platform contained gold film element were fabricated by MEMS technology.For the open-surface microfluidic platform,only liquid storage chamber was designed and fabricated on the surface of gold film for performing immunoassay.Because this system was simple,the nonimmune beads and waste liquid were easy to wash way,and the system was convenient to clean for reuse,and the distribution of Dynabead on the surface of gold film was conveniently observed by SEM.The GMI sensor involving the sensing elements of NiFe/Cu/NiFe with 10 turns was fabricated by micro electroplate technology and used for detection of E.coli O157H:H7.Combined with sandwich assay,highly sensitive,specific and quantitative detection of Dynabead-labeled E.coli O157H:H7 were realized.In the separable detection model,the E.coli O157:H7 samples with different concentration(100,300,500 cfu/ml)captured and labeled by Dynabeads(the diameter is 1 ?m)were placed on the surface of the sensor.The high sensitivity detection was confirmed by that the GMI ration was up to 27.4% when E.coli O157:H7 sample with concentration 100 cfu/ml was present.In addition,Dynabeads with the diameter of 2.8 ?m were also employed for capturing and labeling the E.coli O157:H7.Immunoassay was accomplish in the open-surface microfluidic platform,the microfluidic platform that employed for preparing E.coli O157:H7 sample with different concentrations was put nearby the GMI sensor for measuring.The quantitative detection was achieved,the linear range was 50-500 cfu/ml with the lower limit of detection was 50 cfu/ml.In addition,specific test was achieved using shigella antigen substitution for the E.coli O157:H7 antigen;results show that,there was a very weak positive signal in tests that confirmed the specificity was good.Although,the application for using GMI sensor in bacteria detection was at the initial stage,this biosensor system can make a promise sight in bacteria detection due to the excellent performance such as high sensitivity,conveniently and rapid;[5] Ribbon GMI sensor integrated with an Au film was fabricated by MEMS technology.Using the GMI sensor,Dynabeads with different size(1?m and 2.8 ?m)and different concentration(1-100 ?g/ml)were detected by in-situ testing method.The results showed that the detection limit of Dynabead with 1 ?m and 2.8 ?m was 5 ?g/ml and 1?g/ml respectively.This result provides the basis for detection of C-reactive protein in the following testing.Combined with sandwich immunoassay,quantitative detection of cardiovascular disease biomarker C-reactive protein and myoglobin was realized based on the GMI biosensor by using in-situ measurement method.The linear detection range was 1 to 10 ng/ml,and the detection limits were different,C-reactive protein was 1 ng/ml and myoglobin was 0.5 ng/ml.In addition,the sealed microfluidic platform fabricated by MEMS technology was used in separable detection of C-reactive protein and myoglobin.Ultrasensitivity combination detecting C-reactive protein and myoglobin was achieved by GMI(NiFe/Cu/NiFe)biosensor,the low detection limits was 1 pg/ml and 0.1 pg/ml,the maximum detectability was 100 ng/ml and 80 ng/ml respectively.The quantitative detection of the two biomarker were achieved in low and high concentration level separately.At the low concentration level,the detection liner range of C-reactive protein was 1 pg/ml-10 ng/ml,and the myoglobin was 0.1 pg/ml-1ng/ml;at the high concentration level,the detection liner range of C-reactive protein was 10-100 ng/ml,and the myoglobin was 1-80 ng/ml.The combination detection of biomaeker can be finished within 30 mins,so this method possesses the advantages of short time and high sensitivity.And,it is possible to use the GMI biosensor in clinical detection,there are some reports on application of GMI biosensor in clinical;... |
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