A portable magnetic particle spectrometer for future rapid and wash-free bioassays

Kai Wu, Vinit K Chugh, Arturo di Girolamo, Jinming Liu, Renata Saha, Diqing Su, Venkatramana D. Krishna, Abilash Nair, Will Davies, Yongqiang Andrew Wang, Maxim C.J. Cheeran, Jian Ping Wang

Research output: Contribution to journalArticlepeer-review

17 Scopus citations


Nowadays, there is an increasing demand for more accessible routine diagnostics for patients with respect to high accuracy, ease of use, and low cost. However, the quantitative and high accuracy bioassays in large hospitals and laboratories usually require trained technicians and equipment that is both bulky and expensive. In addition, the multistep bioassays and long turnaround time could severely affect the disease surveillance and control especially in pandemics such as influenza and COVID-19. In view of this, a portable, quantitative bioassay device will be valuable in regions with scarce medical resources and help relieve burden on local healthcare systems. Herein, we introduce the MagiCoil diagnostic device, an inexpensive, portable, quantitative, and rapid bioassay platform based on the magnetic particle spectrometer (MPS) technique. MPS detects the dynamic magnetic responses of magnetic nanoparticles (MNPs) and uses the harmonics from oscillating MNPs as metrics for sensitive and quantitative bioassays. This device does not require trained technicians to operate and employs a fully automatic, one-step, and wash-free assay with a user friendly smartphone interface. Using a streptavidin-biotin binding system as a model, we show that the detection limit of the current portable device for streptavidin is 64 nM (equal to 5.12 pmole). In addition, this MPS technique is very versatile and allows for the detection of different diseases just by changing the surface modifications on MNPs. Although MPS-based bioassays show high sensitivities as reported in many literatures, at the current stage, this portable device faces insufficient sensitivity and needs further improvements. It is foreseen that this kind of portable device can transform the multistep, laboratory-based bioassays to one-step field testing in nonclinical settings such as schools, homes, offices, etc.

Original languageEnglish (US)
Pages (from-to)7966-7976
Number of pages11
JournalACS Applied Materials and Interfaces
Issue number7
StatePublished - Feb 24 2021

Bibliographical note

Funding Information:
This study was financially supported by the Institute of Engineering in Medicine, the Robert F. Hartmann Endowed Chair professorship, the University of Minnesota Medical School, and the University of Minnesota Physicians and Fairview Health Services through COVID-19 Rapid Response Grant. This study was also financially supported by the U.S. Department of Agriculture-National Institute of Food and Agriculture (NIFA) under award no. 2020-67021-31956. Research reported in this publication was supported by the National Institute Of Dental & Craniofacial Research of the National Institutes of Health under award no. R42DE030832. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. Portions of this work were conducted in the Minnesota Nano Center, which is supported by the National Science Foundation through the National Nano Coordinated Infrastructure Network (NNCI) under award no. ECCS-1542202.

Publisher Copyright:
© 2021 American Chemical Society


  • Bioassay
  • Magnetic particle spectrometer
  • Point-of-care
  • Portable
  • Wash-free


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