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The detection principle of the E. coli based on TMR sensor. (a) Photograph of magnetic label sensing system consisting of the Wheatstone bridge, the “test strip” and the lock-in amplifier circuit. (b) Schematic representation of the Wheatstone bridge based on TMR sensors. (c) Schematic representation of sandwich assay on the “test strip.”
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A rapid method for the sensitive detection of bacteria using magnetic immunoassay, which are measured with a tunneling magnetoresistance (TMR)sensor, is described. For the measurement of Escherichia coli O157:H7 (E. coli O157:H7) bacteria, the target was labeled by magnetic beads through magnetic immunoassay. The magnetic beads produce a weak magne...
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Current solutions to diagnose bacterial infections though reliable are often time-consuming, laborious and need a specific laboratory setting. There is an unmet need for bedside accurate diagnosis of infectious diseases with a short turnaround time. Moreover, low-cost diagnostics will greatly benefit regions with poor resources. Immunoassays and mo...
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... For instance, Li J. et al. (2017) developed a magnetic nanobiosensor utilizing MNPs, fluorescence-activated cell sorting (FACS), and magnetic separation for the rapid clinical diagnosis of cancer patients, particularly in detecting circulating tumor cells (CTCs). MNPs also find applications in diverse biomedical fields, including targeted drug delivery (Guo et al., 2022), bioimaging (Zong et al., 2021), targeted hyperthermia for cancer treatment (Zhao et al., 2019;Dash et al., 2022), as well as the capture, isolation, concentration, and detection of nucleic acids (Zhao et al., 2023), bacteria (Behzad et al., 2022), and viruses (Labib et al., 2021;Xing et al., 2022), They have proven effective in immunoassays and immune sensors (Ha and Kim, 2022;Li et al., 2023). ...
... Wu and colleagues (Wu et al., 2017) developed a rapid and highly sensitive bacterial detection method by combining a magnetic immunoassay with a TMR sensor. Escherichia coli O157:H7 bacteria Frontiers in Bioengineering and Biotechnology frontiersin.org ...
The significance of point-of-care testing (POCT) in early clinical diagnosis and personalized patient care is increasingly recognized as a crucial tool in reducing disease outbreaks and improving patient survival rates. Within the realm of POCT, biosensors utilizing magnetic nanoparticles (MNPs) have emerged as a subject of substantial interest. This review aims to provide a comprehensive evaluation of the current landscape of POCT, emphasizing its growing significance within clinical practice. Subsequently, the current status of the combination of MNPs in the Biological detection has been presented. Furthermore, it delves into the specific domain of MNP-based biosensors, assessing their potential impact on POCT. By combining existing research and spotlighting pivotal discoveries, this review enhances our comprehension of the advancements and promising prospects offered by MNP-based biosensors in the context of POCT. It seeks to facilitate informed decision-making among healthcare professionals and researchers while also promoting further exploration in this promising field of study.
... Lei et al., e.g., demonstrated measurements of low concentrations of magnetic nanoparticles attached to human chorionic gonadotropin using a TMR sensor [128]. In the case of E. coli detection by a TMR biosensor, the bacteria were labeled with magnetic beads, resulting in its high sensitivity and their rapid detection [129]. Similarly, carboxyl-modified Fe 3 O 4 nanoparticles with anti-ricin monoclonal antibodies were used for the TMR-based detection of ricin [130], and other biomarkers with magnetic beads as labels have successfully been detected by TMR sensors [131][132][133]. ...
... using a TMR sensor [128]. In the case of E. coli detection by a TMR biosensor, the bacteria were labeled with magnetic beads, resulting in its high sensitivity and their rapid detection [129]. Similarly, carboxyl-modified Fe3O4 nanoparticles with anti-ricin monoclonal antibodies were used for the TMR-based detection of ricin [130], and other biomarkers with magnetic beads as labels have successfully been detected by TMR sensors [131][132][133]. ...
Magnetic micro and nano sensors can be used in a broad variety of applications, e.g., for navigation, automotives, smartphones and also for health monitoring. Based on physical effects such as the well-known magnetic induction, the Hall effect, tunnel magnetoresistance and giant magne-toresistance, they can be used to measure positions, flow, pressure and other physical properties. In biomedicine and healthcare, these miniaturized sensors can be either integrated into garments and other wearables, be directed through the body by passive capsules or active micro-robots or be implanted, which usually necessitates bio-functionalization and avoiding cell-toxic materials. This review describes the physical effects that can be applied in these sensors and discusses the most recent micro and nano sensors developed for healthcare applications.
... For this reason, many magnetic methods have been studied to detect magnetic nanoparticles and evaluate antigen-antibody reactions using various magnetic sensors. [10][11][12][13][14][15][16][17][18][19][20][21][22][23] In a previous study, we developed a detection system of oral bacteria based on a magnetic immunoassay using a magnetoimpedance (MI) sensor. 24,25 However, the system could not be used to detect several samples simultaneously. ...
A quick and easy method to detect the GDF-15 protein (Growth Differentiation Factor-15) has been developed, which utilize the magnetic response of magnetic nanoparticles by switching magnetic fields. The magnetic nanoparticles and GDF-15 are bound by an antigen-antibody reaction and aggregated into a spherical shape using a needle-shaped magnetic yoke. The density of GDF-15 changed as follows: 0, 1 ng/ml, 10 ng/ml, and 100 ng/ml. The increase of GDF-15 aggregated the magnetic nanoparticles and enhanced the signal-to-noise ratio. We also tried the sandwich-type bound method using a primary and secondary antibody with additional magnetic nanoparticles and obtained the enhancement of the magnetic signal in a lower concentration (under 10 ng/ml) of GDF-15. The cross-bridges between magnetic nanoparticle and the protein may strengthen the magnetic couplings of nanoparticles.
... [3][4][5][6][7] Magnetic relaxation and ac susceptibility-based measurement methods have been developed for the detection of biological targets using the detected magnetic fringe field produced by the MNPs. [8][9][10][11][12][13] Although the smaller nanoparticles (NPs) have a greater surface-to-volume ratio to interact with targets, it is well reported that the saturation magnetization of MNPs decreases with decreasing their size. 14 To enhance their magnetic moment without increasing their size, FeCo alloy NPs are proposed recently. ...
In this study, we prepared ultrasmall FeCo nanoparticles (NPs) with a high magnetic moment and examined their antigen-antibody reaction for biodetection applications. The FeCo NPs were collected from the FeCo-BaF 2 nanogranular film with Fe:Co:Ba:F = 14:11:21:54 at.%, by dissolving the film in water since the BaF 2 matrix was deliquescent. The size of FeCo NPs was ∼5 nm and the saturation magnetization was estimated to be ∼15.30 kG (149.0 emu/g). The Candida albicans antibodies (abcam ab53891)-conjugated FeCo NPs were collected by using an ultracentrifugal separation (110 000 rpm, 90 min), they were then reacted with Candida albicans. The obtained result indicates that Candida albicans were absorbed successfully onto FeCo NPs, and the number of Candida albicans bound to FeCo NPs counted from the micrographs of the aggregates of FeCo NPs and Candida albicans increased significantly by adding sonication treatment of the film in water before binding them to the antibodies. The success of antigen-antibody reaction of ultrasmall NPs with high magnetic moment improves detection sensitivity as well as offers potential detection for smaller biomolecules.
... In the past few years researchers attempted different approaches and platform for designing magnetic-based biosensor, from magnetoresistance devices to electromagnetic sensors such as magnetic lateral flow biosensors [14], [18]- [21]. Magnetoresistive sensors such as AMR [20], TMR [23], GMR [24,25] and Hall Effect Sensor [26] have also been widely studied and applied as biosensor. These can detect very weak magnetic fields which results in very high sensitivity suitable for single bead detection, although they are costly. ...
p>Design of rapid technique for magnetic particles detection based on inductive sensing is described in this paper. A fabricated 3D coil, oscillating at few MHz range frequencies, is used as a sensing element with its associated electronics for inductance measurements. Phase locked loop is used for sensor stability and accuracy in the detection system. The induced magnetic field, due to the presence of magnetic particles on the coil, alter the coil inductance and accordingly the output frequency signal. Different concentration and number of magnetic beads (µm to nm sizes) were tested with the sensor while oscillating at two different resonance frequencies and the results were compared together. </p
... In the past few years researchers attempted different approaches and platform for designing magnetic-based biosensor, from magnetoresistance devices to electromagnetic sensors such as magnetic lateral flow biosensors [14], [18]- [21]. Magnetoresistive sensors such as AMR [20], TMR [23], GMR [24,25] and Hall Effect Sensor [26] have also been widely studied and applied as biosensor. These can detect very weak magnetic fields which results in very high sensitivity suitable for single bead detection, although they are costly. ...
p>Design of rapid technique for magnetic particles detection based on inductive sensing is described in this paper. A fabricated 3D coil, oscillating at few MHz range frequencies, is used as a sensing element with its associated electronics for inductance measurements. Phase locked loop is used for sensor stability and accuracy in the detection system. The induced magnetic field, due to the presence of magnetic particles on the coil, alter the coil inductance and accordingly the output frequency signal. Different concentration and number of magnetic beads (µm to nm sizes) were tested with the sensor while oscillating at two different resonance frequencies and the results were compared together. </p
... The detection of bacteria with MR biosensors follows a similar mechanism with the previously discussed MR biosensing platforms. The TMR sensor array has been applied in the detection of E. coli O157:H7 with a LOD at 10 2 CFU/mL [188]. Meanwhile, microfluidics was employed in the GMR biosensing platform for E.coli detection [189]. ...
Magnetoresistance (MR) is the variation of a material’s resistivity under the presence of external magnetic fields. Reading heads in hard disk drives (HDDs) are the most common applications of MR sensors. Since the discovery of giant magnetoresistance (GMR) in the 1980s and the application of GMR reading heads in the 1990s, the MR sensors lead to the rapid developments of the HDDs’ storage capacity. Nowadays, MR sensors are employed in magnetic storage, position sensing, current sensing, non-destructive monitoring, and biomedical sensing systems. MR sensors are used to transfer the variation of the target magnetic fields to other signals such as resistance change. This review illustrates the progress of developing nanoconstructed MR materials/structures. Meanwhile, it offers an overview of current trends regarding the applications of MR sensors. In addition, the challenges in designing/developing MR sensors with enhanced performance and cost-efficiency are discussed in this review.
... Figure 17 shows the transfer curves of the proposed sensor in the as-deposited state, after the first annealing and after the second annealing, where the TMR ratios of 52%, 150%, and 160% are achieved, respectively. Researchers have recently developed a rapid bacteria detection method based on a TMR sensor [142]. To measure Escherichia coli bacteria, they labeled the target by magnetic particles producing a magnetic fringe field in an external magnetic field, the signal of which is detected by the TMR sensor. ...
Magnetic nanoparticles have attracted significant attention in various disciplines, including engineering and medicine. Microfluidic chips and lab-on-a-chip devices, with precise control over small volumes of fluids and tiny particles, are appropriate tools for the synthesis, manipulation, and evaluation of nanoparticles. Moreover, the controllability and automation offered by the microfluidic chips in combination with the unique capabilities of the magnetic nanoparticles and their ability to be remotely controlled and detected, have recently provided tremendous advances in biotechnology. In particular, microfluidic chips with magnetic nanoparticles serve as sensitive, high throughput, and portable devices for contactless detecting and manipulating DNAs, RNAs, living cells, and viruses. In this work, we review recent fundamental advances in the field with a focus on biomedical applications. First, we study novel microfluidic-based methods in synthesizing magnetic nanoparticles as well as microparticles encapsulating them. We review both continues-flow and droplet-based microreactors, including the ones based on the cross-flow, co-flow, and flow-focusing methods. Then, we investigate the microfluidic-based methods for manipulating tiny magnetic particles. These manipulation techniques include the ones based on external magnets, embedded micro-coils, and magnetic thin films. Finally, we review techniques invented for the detection and magnetic measurement of magnetic nanoparticles and magnetically labeled bioparticles. We include the advances in anisotropic magnetoresistive, giant magnetoresistive, tunneling magnetoresistive, and magnetorelaxometry sensors. Overall, this review covers a wide range of the field uniquely and provides essential information for designing “lab-on-a-chip” systems for synthesizing magnetic nanoparticles, labeling bioparticles with them, and sorting and detecting them on a single chip.
... High sensitivity and the ability of the weak magnetic field detection (,10 29 to 10 210 T) make TMR sensors or spin-valve read sensors excellent candidates for biosensing applications. Wu et al. described a practical method using TMR sensor for the rapid quantification of Escherichia coli O157:H7 (E. coli O157:H7) bacteria [35]. In the first step, the sensor surface was covered with a 50-nm gold film through the sputtering technique, and then the gold film was functionalized with monoclonal antibodies. ...
Due to their superparamagnetism property as well as the high surface-to-volume ratios, magnetic nanomaterials (MNMs) have been utilized as both sorbents and sensors in analytical chemistry. Different aspects of the application of MNMs in analytical chemistry have widely been reviewed. However, the application of MNMs in the magnetic field sensors has been less investigated. Magnetic field sensors can be generally divided into two categories: magnetoresistive sensors and nonmagnetoresistive sensors. Magnetoresistive sensors rely on the dependence of material resistance to its magnetization state. The nonmagnetoresistive sensors can be utilized under high magnetic fields without being bothered by magnetic saturation. This chapter provides an overview of the application of MNMs in magnetic field sensors along with fundamental principles.
... To detect E. coli O157:H7 while using test strips, capture antibody-conjugated magnetic beads were employed. Signals were measured based on a potential change caused by difference of magnetic field fluctuation pattern due to the contrast between existence and absence of target binding to antibody-conjugated MNPs [127] (see Figure 5C and 5D). Mu et al. also conducted a study of detecting ricin on a test strip with magnetic field generating platform constituting of vertical and horizontal coils [128]. ...
... Inset: magnetic field dependence on the resistance of a TMR sensor. Reproduced with permission from[122,127]. ...
The growing interest in magnetic materials as a universal tool has been shown by an increasing number of scientific publications regarding magnetic materials and its various applications. Substantial progress has been recently made on the synthesis of magnetic iron oxide particles in terms of size, chemical composition, and surface chemistry. In addition, surface layers of polymers, silica, biomolecules, etc., on magnetic particles, can be modified to obtain affinity to target molecules. The developed magnetic iron oxide particles have been significantly utilized for diagnostic applications, such as sample preparations and biosensing platforms, leading to the selectivity and sensitivity against target molecules and the ease of use in the sensing systems. For the process of sample preparations, the magnetic particles do assist in target isolation from biological environments, having non-specific molecules and undesired molecules. Moreover, the magnetic particles can be easily applied for various methods of biosensing devices, such as optical, electrochemical, and magnetic phenomena-based methods, and also any methods combined with microfluidic systems. Here we review the utilization of magnetic materials in the isolation/preconcentration of various molecules and cells, and their use in various techniques for diagnostic biosensors that may greatly contribute to future innovation in point-of-care and high-throughput automation systems.
