Abstract

In recent years, the quantitative detection of biomolecules based on Giant magnetoresistive (GMR) sensors and magnetic nanoparticles have received continuous attention. Researchers try to improve the accuracy of detection by various methods, including using a more sensitive sensor, designing circuit to reduce system noise, and so on. In which, the intrinsic properties of magnetic labels, such as the particle size of labels is a vital aspect for the GMR biosensing technology. In this work, a series of Fe3O4 particles with average particle sizes from 80 to 580 nm were prepared for exploring the effect of particle size on the limit of detection (LOD). An ultra-low LOD of 0.1 ng/mL was obtained for small particles with average sizes from 80 to 200 nm detected by our home-made biodetection device. However, for the ones with large sizes from 330 to 580 nm, the LOD increases with the increase of particle size. The total magnetic moments of all particles attached on the sensor surface Σmm are calculated theoretically and compared with the experimental data of the normalized voltage ratio (Vnvr=|ΔV|/V0×100%) over particle size. It is found that not only the particle size but also the magnetic moment of particles affect the LOD of the concentration.

Highlights

  • In recent years, the quantitative detection of biomolecules has been extensively applied in many fields, including environment monitoring, medicine, biology and drug discovery, and so on

  • A series of Fe3O4 particles with average particle sizes from 80 to 580 nm were prepared for exploring the effect of particle size on the limit of detection (LOD)

  • In order to explore the effect of the particle size and magnetic moment of the labels on the detection, the Fe3O4 superparamagnetic beads (SPMBs) with different sizes were synthesized by a solvothermal method

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Summary

INTRODUCTION

The quantitative detection of biomolecules has been extensively applied in many fields, including environment monitoring, medicine, biology and drug discovery, and so on. The SPMBs can be dispersed in the solution well without aggregation; on the other hand, they exhibit a large magnetization and large stray field. Their controllable wide size range provides a flexibility for detecting various kinds of biomolecules with different size. In 2014, Wang et al studied the effect of particle size on the LOD of GMR biosensors using magnetic nanoparticles with sizes from 10 to 100 nm, which were purchased from three different companies. A series of Fe3O4 particles with average particle sizes from 80 to 580 nm were prepared for exploring the effect of particle size and magnetic moment of particles on the limit of detection (LOD). It was found that the particle size and the magnetic moment of particles affect the LOD essential

GMR detection system
The synthesis of Fe3O4 SPMBs
Preparation of Fe3O4 SPMBs-alcohol solutions
RESULTS AND DISCUSSION
Bias magnetic field for GMR sensor
Detection of different Fe3O4 SPMBs-alcohol solutions
The comparison between experimental and fitting results
CONCLUSIONS

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