Magnetic Particle Spectroscopy (MPS) with One-stage Lock-in Implementation for Magnetic Bioassays with Improved Sensitivities

TL;DR

This paper introduces a one-stage lock-in magnetic particle spectroscopy system that enhances sensitivity for bioassays by effectively removing feedthrough signals, enabling detection of lower concentrations of magnetic nanoparticles and improving bioassay sensitivity.

Contribution

The study presents a novel one-stage lock-in MPS platform that significantly improves sensitivity and allows for effective detection of magnetic nanoparticles in bioassays.

Findings

Detects as low as 781 ng multi-core MNPs and 78 ng single-core MNPs.

Enables Brownian relaxation-based bioassays with single-core MNPs.

Lower MNP concentrations improve detection sensitivity.

Abstract

In recent years, magnetic particle spectroscopy (MPS) has become a highly sensitive and versatile sensing technique for quantitative bioassays. It relies on the dynamic magnetic responses of magnetic nanoparticles (MNPs) for the detection of target analytes in liquid phase. There are many research studies reporting the application of MPS for detecting a variety of analytes including viruses, toxins, and nucleic acids, etc. Herein, we report a modified version of MPS platform with the addition of a one-stage lock-in design to remove the feedthrough signals induced by external driving magnetic fields, thus capturing only MNP responses for improved system sensitivity. This one-stage lock-in MPS system is able to detect as low as 781 ng multi-core Nanomag50 iron oxide MNPs (micromod Partikeltechnologie GmbH) and 78 ng single-core SHB30 iron oxide MNPs (Ocean NanoTech). In addition, using a streptavidin-biotin binding system as a proof-of-concept, we show that these single-core SHB30 MNPs can be used for Brownian relaxation-based bioassays while the multi-core Nanomag50 cannot be used. The effects of MNP amount on the concentration dependent response profiles for detecting streptavidin was also investigated. Results show that by using lower concentration/amount of MNPs, concentration-response curves shift to lower concentration/amount of target analytes. This lower concentrationresponse indicates the possibility of improved bioassay sensitivities by using lower amounts of MNPs.