title: Contactless Measurement of Magnetic Nanoparticles on Lateral Flow Strips Using Tunneling Magnetoresistance (TMR) Sensors in Differential Configuration.
abstract: Magnetic nanoparticles (MNPs) are commonly used in biomedical detection due to their capability to bind with some specific antibodies. Quantification of biological entities could be realized by measuring the magnetic response of MNPs after the binding process. This paper presents a contactless scanning prototype based on tunneling magnetoresistance (TMR) sensors for quantification of MNPs present in lateral flow strips (LFSs). The sensing unit of the prototype composes of two active TMR elements, which are parallel and closely arranged to form a differential sensing configuration in a perpendicular magnetic field. Geometrical parameters of the configuration are optimized according to theoretical analysis of the stray magnetic field produced by the test line (T-line) while strips being scanned. A brief description of our prototype and the sample preparation is presented. Experimental results show that the prototype exhibits the performance of high sensitivity and strong anti-interference ability. Meanwhile, the detection speed has been improved compared with existing similar techniques. The proposed prototype demonstrates a good sensitivity for detecting samples containing human chorionic gonadotropin (hCG) at a concentration of 25 mIU/mL. The T-line produced by the sample with low concentration is almost beyond the visual limit and produces a maximum stray magnetic field some 0.247 mOe at the sensor in thexdirection.
authors.affiliation: Department of Instrument Science and Engineering, Shanghai Jiaotong University, Shanghai 200240, China. hmlei@sjtu.edu.cn.|Shanghai Engineering Research Center for Intelligent Diagnosis and Treatment Instrument, Shanghai 200240, China. hmlei@sjtu.edu.cn.
authors.forename: Huaming
authors.initials: H
authors.lastname: Lei
authors.affiliation: Department of Instrument Science and Engineering, Shanghai Jiaotong University, Shanghai 200240, China. wk_xa@sjtu.edu.cn.|Shanghai Engineering Research Center for Intelligent Diagnosis and Treatment Instrument, Shanghai 200240, China. wk_xa@sjtu.edu.cn.
authors.forename: Kan
authors.initials: K
authors.lastname: Wang
authors.affiliation: Department of Instrument Science and Engineering, Shanghai Jiaotong University, Shanghai 200240, China. jxj127@sjtu.edu.cn.|Shanghai Engineering Research Center for Intelligent Diagnosis and Treatment Instrument, Shanghai 200240, China. jxj127@sjtu.edu.cn.
authors.forename: Xiaojun
authors.initials: X
authors.lastname: Ji
authors.affiliation: Department of Instrument Science and Engineering, Shanghai Jiaotong University, Shanghai 200240, China. dxcui@sjtu.edu.cn.|Shanghai Engineering Research Center for Intelligent Diagnosis and Treatment Instrument, Shanghai 200240, China. dxcui@sjtu.edu.cn.
authors.forename: Daxiang
authors.initials: D
authors.lastname: Cui
keywords: differential sensing; lateral flow strip (LFS); magnetic biosensor; magnetic nanoparticles; tunneling magnetoresistance (TMR) sensor