A miniaturized giant magnetic resistance system for quantitative detection of methamphetamine.

Point-of-care testing (POCT) systems have been greatly developed in recent years. Among them, lateral flow immunoassay (LFIA) based on magnetic nanoparticles (MNPs) is widely used in various fields due to the advantages of small background noise and good biocompatibility. This paper designed an ultra-sensitive giant magnetic resistance (GMR) system for the quantitative detection of methamphetamine (MET). The system uses GMRs to detect the distribution of the magnetic field intensity of MNPs captured by the test (T) and control (C) lines on LFIA. A special external interference cancellation (EIC) method and a weak-signal waveform reconstruction method were used to improve the accuracy of the detection. Finally, the T/C ratio was calculated to realize the quantitative detection of MET. The result showed good linear performance with a detection limit of 0.1 ng mL-1. The system can also be used in other fields such as disease detection, food analysis, and environmental testing.