Rapid Immunoassay Method And System Based On Magnetic Nanoparticles Labeling

Rapid immunoassay methods are of great importance in fields such as biomedicine,while the immunoassay method based on magnetic nanoparticles labeling is expected to achieve this goal.In this thesis,a rapid immunoassay method and system based on magnetic nanoparticles labeling is proposed for liquid-phase detection of biological targets using magnetic labeling.Based on the magnetic response properties of magnetic nanoparticles,combined with a dual-frequency excitation model,used Tunnel Magnetoresistance(TMR)sensors as magnetic probes to detect the harmonic response signal,and distinguish biological targets by detecting difference in magnetic labeling response between bound and unbound states.Firstly,a dual-frequency excitation model for magnetic nanoparticles is developed in this thesis.Based on an in-depth analysis of the magnetic response characteristics of magnetic nanoparticles,the amplitude expression of the harmonic response of magnetic nanoparticles under a dual-frequency excitation field is derived,and it is found that the mixed-frequency third harmonic has a higher signal-to-noise ratio than the single-frequency third harmonic under certain conditions,which is more suitable as a detection indicator for biological target identification.Compared with the traditional single-frequency excitation model,this model can effectively improve the sensitivity of biological target detection.Secondly,a fast immunoassay system based on magnetic nanoparticles labeling was designed in this thesis.The detection part of the system uses TMR sensors as magnetic probes,making the system easy to integrate and providing ideas and directions for the instrumental application of rapid immunoassay methods.In addition,the excitation part of the system uses closed-loop feedback control to ensure the stability of the excitation field,and the signal processing part of the system uses residual magnetism elimination technology to further improve the signal-to-noise ratio of signal detection.Finally,the system was tested experimentally.Magnetic nanoparticles labeling used streptavidin-modified magnetic beads with 100 nm particle size,and biological targets used biotin-modified polystyrene microspheres with 100 nm particle size.Aiming at maximizing the variation of the amplitude of the third harmonic mixing before and after combining with the biological targets,the excitation parameters of the dual-frequency excitation model were optimized,and then the system was tested for lower limit of response detection and labeling of the biological targets.The results showed that the detection limit of magnetic bead particle number is better than 6.15 fmol,and the system is able to achieve 3.1fmol biological targets detection within 1 minute.The experimental results show that the rapid immunoassay method based on magnetic nanoparticles labeling is feasible.