New design of a commercial chip-based GMR sensor with magnetite nanoparticles for biosensing applications
Harlina Ardiyanti, Ni’matil Mabarroh, Nur Aji Wibowo, Nurul Imani Istiqomah, Rivaldo Marsel Tumbelaka, Moh. Adhib Ulil Absor, Edi Suharyadi
Abstract
The availability of rapid and low-cost instruments to detect magnetic nanoparticles (MNPs) concentrations is vital in giant magnetoresistance (GMR)-based biosensors. This paper reports a new setup for a simple GMR sensor using the commercial chip AAL024 as a transducer. It was combined with a basic differential amplifier and microcontroller to acquire digital output voltages for the detection of green-synthesized (GS)-Fe3O4 MNPs as a label and streptavidin-coated MNPs in biosensor applications. As a characteristic feature of Fe3O4, the GS-Fe3O4 MNPs displayed a cubic inverse spinel structure. The average GS-Fe3O4 particle size was 11 nm and they exhibited soft ferromagnetic behavior with a saturation magnetization (MS) of 55.5 emu/g. Owing to the presence of phytochemical components in the Moringa oleifera (MO) extract, the MS of GS-Fe3O4 was lower than that of Fe3O4. To study sensor performance, the detection of the GS-Fe3O4 MNP labels and streptavidin-coated MNPs assay was investigated. Using the microcontroller as the supply voltage for the AAL024 and an analog-to-digital converter simplified data collection and made any additional measuring instruments unnecessary. The sensor showed promising performance with the GS-Fe3O4 MNP label and streptavidin assay owing to the linear correspondence between the signal and concentration of the MNP label. A small limit-of-detection of 4 mg/mL was achieved for GS-Fe3O4. The sensitivity of GS-Fe3O4 and streptavidin were 2.79 and 1.80 mV/(mg/mL), respectively. Moreover, the excellent stability and reproducibility of the sensor were confirmed by the stable signal for over 30 s with relative signal deviation (RSD) ranges of 2–20% and 2–10% for MNPs and streptavidin, respectively.