One-Step Detection of Pathogens and Viruses: Combining Magnetic Relaxation Switching and Magnetic Separation

Abstract

We report a sensing methodology that combines magnetic separation (MS) and magnetic relaxation switching (MS-MRS) for one-step detection of bacteria and viruses with high sensitivity and reproducibility. We first employ a magnetic field of 0.01 T to separate the magnetic beads of large size (250 nm in diameter) from those of small size (30 nm in diameter) and use the transverse relaxation time (T2) of the water molecules around the 30 nm magnetic beads (MB30) as the signal readout of the immunoassay. An MS-MRS sensor integrates target enrichment, extraction, and detection into one step, and the entire immunoassay can be completed within 30 min. Compared with a traditional MRS sensor, an MS-MRS sensor shows enhanced sensitivity, better reproducibility, and convenient operation, thus providing a promising platform for point-of-care testing.

Quantitative Detection of MicroRNA in One Step via Next Generation Magnetic Relaxation Switch Sensing

“…We find that the large MM 1000 could be rapidly accumulated toward the vial wall within 3 min under 0.01 T due to its high saturation magnetization, whereas MB 30 is well dispersed even Figure S1). We thus adopt the ΔT 2 value of supernatant containing MN 30 as the signal readout, since the amount of cleaved MN 30 from MM 1000 -DNA-MN 30 conjugates is related to the concentration of miRNA during DSN enzymeassisted TRA. Although previous studies have designed MRS nanoassemblies for screening of DNA-cleaving agents, these methods still measure the T 2 based on the state change between nanoassembly and dispersed nanoparticles.…”

“…In the presence of target miRNA, DNA in formed DNA-RNA heteroduplexes could be specifically cleaved by DSN, resulting in the release of MN 30 and an enhancement of ΔT 2 . This direct assay allows for quantitative and sensitive detection of miR-21 in urine samples and tumor cells, without the conversion of miRNA to cDNA, nor the multiple assay steps.…”

Environmental implications and applications of engineered nanoscale magnetite and its hybrid nanocomposites: A review of recent literature

“…A sensing methodology that combines magnetic separation (MS) and magnetic relaxation switching (MS-MRS) for one-step detection of bacteria and viruses has been reported. Compared with a traditional MRS sensor, an MS-MRS sensor shows enhanced sensitivity, better reproducibility, and convenient operation, thus providing a promising platform for point-of-care testing [129]. A protease-activated ratiometric fluorescent probe based on fluorescence resonance energy transfer between a pH-sensitive fluorescent dye and biocompatible MNPs has been constructed to image the pH of subcutaneous tumor xenografts [130].…”

Blu-ray optomagnetic measurement based competitive immunoassay for Salmonella detection

“…On the other hand, when employing a clinical affinity capture strategy, e.g. a bacterial immunoassay, the sensitivity of those devices (LOD of higher than 10 6 CFU/mL) is inferior compared to that of a miniaturized nuclear magnetic resonance (NMR) system (LOD of 10 3 CFU/mL), which benefits from a built-in signal amplification (since millions of water molecules can be affected by one individual magnetic particle) (Grossman et al, 2004;Chen et al, 2015). Furthermore, all those aforementioned biosensors require expensive instrumentation.…”