Ferromagnetic Resonance Biosensor for Homogeneous and Volumetric Detection of DNA

Abstract

The ability to detect and analyze the state of magnetic labels with high sensitivity is of crucial importance for developing magnetic biosensors. In this work, we demonstrate, for the first time, a ferromagnetic resonance (FMR) based homogeneous and volumetric biosensor for magnetic label detection. Two different isothermal amplification methods, i.e., rolling circle amplification (RCA) and loop-mediated isothermal amplification (LAMP), are adopted and combined with a standard electron paramagnetic resonance (EPR) spectrometer for FMR biosensing. For the RCA-based FMR biosensor, binding of RCA products of a synthetic Vibrio cholerae target DNA sequence gives rise to the formation of aggregates of magnetic nanoparticles. Immobilization of nanoparticles within the aggregates leads to a decrease of the net anisotropy of the system and a concomitant increase of the resonance field. A limit of detection of 1 pM is obtained with a linear detection range between 7.8 and 250 pM. For the LAMP-based sensing, a synthetic Zika virus target oligonucleotide is amplified and detected in 20% serum samples. Immobilization of magnetic nanoparticles is induced by their coprecipitation with MgPO (a byproduct of LAMP) and provides a detection sensitivity of 100 aM. The fast measurement, high sensitivity, and miniaturization potential of the proposed FMR biosensing technology makes it a promising candidate for designing future point-of-care devices.

Characterization of Binding of Magnetic Nanoparticles to Rolling Circle Amplification Products by Turn-On Magnetic Assay

“…In addition, biological samples are generally not magnetic and thus do not affect the sensitivity/signal transduction in the magnetic domain, unlike how fluorescence can in the optical domain. Numerous methods have been developed for sensing the magnetically labelled target analytes in a volume [13] and on a sensor surface and some of which are used for detection of magnetically labeled RCPs including: magneto-resistive sensors [14], superconducting quantum interference devices (SQUIDs) [9,15,16,17], induction coils [18,19], optomagnetic sensors [20,21], and ferromagnetic resonance sensors [22]. The MNPs are conjugated to the RCPs by base pare hybridization forming MNP-RCP complexes which have a larger hydrodynamic size compared to the unbound MNPs.…”

Magnetic Nanoclusters Coated with Albumin, Casein, and Gelatin: Size Tuning, Relaxivity, Stability, Protein Corona, and Application in Nuclear Magnetic Resonance Immunoassay

“…The colloidal stability of magnetic nanoprobes at elevated temperatures is essential for applications in assays based on the isothermal amplification of DNA (e.g., loop-mediated isothermal amplification or rolling circle amplification) [49] or PCR [50], when reaction mixtures can be heated up to +95 °C. The aggregation of nanoparticles can negatively influence assay performance.…”

Magnetic-Nanosensor-Based Virus and Pathogen Detection Strategies before and during COVID-19

“…Tian et al reported ferromagnetic resonance (FMR)-based volumetric and homogeneous biosensors for DNA detection. 148 This method quantifies the target DNA by measuring the FMR field shift of the suspension. The detection strategy for target DNA is based on an isothermal amplification followed by hybridization with detection-antibody-modified MNPs.…”

“…Tian et al reported the volumetric detection of DNA using FMR shifts. 148 Aggregation of MNPs was caused by binding of the V. cholerae target DNA sequence, which gave rise to significant FMR shifts compared to nonaggregated MNPs. However, this technique involves the insertion of MNP samples inside an electromagnetic cavity, which is not nanoscale-frequency detection.…”