A New Platform of Iron Oxide-Based Nanoparticles Assay Using GMR Chip-Based Sensor With Microcontroller

The low-cost, simple, and fast quantitative assay of magnetic nanoparticles (MNPs) is important for the development of magnetic-based immunoassay applications. However, the bulky sensing element and instruments of the recent iron oxide-based MNPs assays are still concerns that should be resolved. This article reports the new platform of an iron oxide-based MNPs label assay using the commercial giant magnetoresistance (GMR) chip AAL024, manufactured by Nonvolatile Electronics (NVE) Corporation, complemented with a basic differential amplifier circuit and Arduino microcontroller (AM) to acquire the digital output voltage. The as-prepared Fe3O4@Ag label possessed (15 ± 2.6) nm of average size and behaved as soft ferromagnetic with 52.1 emu/g of saturation magnetization, and 0.15 kOe of coercive field. Sensor performance for magnetic field detection, as well as Fe3O4@Ag nanoparticles label assay, was evaluated. The results show the implementation of a basic differential amplifier op-amp circuit succeed to magnify the sensor’s response to the magnetic field up to 23 times with the output voltage in the order of volt. The employment of the AM as a voltage supply of the GMR chip, an analog-to-digital converter, and a voltage gauge simplifies the data acquisition without the additional measuring instrument. Meanwhile, for the purpose of the Fe3O4@Ag nanoparticles label assay, the sensor revealed promising performance due to the high signal linearity and the rapid detection which is only 30 s with acceptable signal stabilities.