Multiplex Immunoassays Utilizing Differential Affinity Using Aptamers Generated by MARAS.

Disease diagnosis typically requires to determine concentration of multiple biomarkers in patient serums. Here, a novel method for multiplex immunoassays is proposed and the feasibility is demonstrated. The method utilizes the differential affinity between aptamers and multiple analytes for multiplex immunoassays.

Generation of Aptamers from A Primer-Free Randomized ssDNA Library Using Magnetic-Assisted Rapid Aptamer Selection.

Aptamers are oligonucleotides that can bind to specific target molecules. Most aptamers are generated using random libraries in the standard systematic evolution of ligands by exponential enrichment (SELEX). Each random library contains oligonucleotides with a randomized central region and two fixed primer regions at both ends.

A novel protocol for generating high-affinity ssDNA aptamers by using alternating magnetic fields.

Background: Aptamers that have been generated using a SELEX (Systematic Evolution of Ligands by EXponential enrichment) process have been found to have high specificity and affinity with molecular targets, and, as a result, have found use in diagnostic and therapeutic applications. The SELEX protocol generally requires 5 to 15 rounds of selection to generate high-affinity aptamers; however, the standard protocol is labor-intensive and time-consuming. Here, we propose a method for DNA aptamer screening, in which the evolutionary process is completely abandoned.

Magnetic-assisted rapid aptamer selection (MARAS) for generating high-affinity DNA aptamer using rotating magnetic fields.

A new SELEX protocol for the development of DNA aptamers has been demonstrated, referred to as magnetic-assisted rapid aptamer selection (MARAS). This method uses magnetic beads and an externally applied rotating magnetic field to provide the competitive mechanism for the selection aptamers with different affinities to the molecular target. The MARAS protocol efficiently generated aptamers with high affinity and specificity for C-reactive protein, a common cardiovascular disease indicator.

Anti-CEA-functionalized superparamagnetic iron oxide nanoparticles for examining colorectal tumors in vivo.

Although the biomarker carcinoembryonic antigen (CEA) is expressed in colorectal tumors, the utility of an anti-CEA-functionalized image medium is powerful for in vivo positioning of colorectal tumors. With a risk of superparamagnetic iron oxide nanoparticles (SPIONPs) that is lower for animals than other material carriers, anti-CEA-functionalized SPIONPs were synthesized in this study for labeling colorectal tumors by conducting different preoperatively and intraoperatively in vivo examinations. In magnetic resonance imaging (MRI), the image variation of colorectal tumors reached the maximum at approximately 24 h.

Combined plasma biomarkers for diagnosing mild cognition impairment and Alzheimer's disease.

A highly sensitive immunoassay, the immunomagnetic reduction, is used to measure several biomarkers for plasma that is related to Alzheimer's disease (AD). These biomarkers include Aβ-40, Aβ-42, and tau proteins. The samples are composed of four groups: healthy controls (n=66), mild cognitive impairment (MCI, n=22), very mild dementia (n=23), and mild-to-serve dementia, all due to AD (n=22).

In vivo screening of hepatocellular carcinoma using AC susceptibility of anti-alpha fetoprotein-activated magnetic nanoparticles.

With antibody-mediated magnetic nanoparticles (MNPs) applied in cancer examinations, patients must pay at least twice for MNP reagents in immunomagnetic reduction (IMR) of in vitro screening and magnetic resonance imaging (MRI) of in vivo tests. This is because the high maintenance costs and complex analysis of MRI have limited the possibility of in vivo screening. Therefore, this study proposes novel methods for in vivo screening of tumors by examining the AC susceptibility of bound MNPs using scanning superconducting-quantum-interference-device (SQUID) biosusceptometry (SSB), thereby demonstrating high portability and improved economy.

Use of immunomagnetic reduction for C-reactive protein assay in clinical samples.

Background: Magnetic nanoparticles biofunctionalized with antibodies are able to recognize and bind to the corresponding antigens. In this work, anti-C-reactive protein (CRP) antibody was covalently conjugated onto the surface of magnetic nanoparticles to label CRP specifically in serum.

Methods: The level of serum CRP was detected by immunomagnetic reduction (IMR) assay, which identifies the changes in the magnetic signal representing the level of interaction between antibody-conjugated magnetic nanoparticles and CRP proteins.

Biofunctionalized magnetic nanoparticles for specifically detecting biomarkers of Alzheimer's disease in vitro.

Magnetic nanoparticles biofunctionalized with antibodies against β-amyloid-40 (Aβ-40) and Aβ-42, which are promising biomarkers related to Alzheimer's disease (AD), were synthesized. We characterized the size distribution, saturated magnetizations, and stability of the magnetic nanoparticles conjugated with anti-Aβ antibody. In combination with immunomagnetic reduction technology, it is demonstrated such biofunctionalized magnetic nanoparticles are able to label Aβs specifically.

Characteristics of magnetic labeling on liver tumors with anti-alpha-fetoprotein-mediated Fe3O4 magnetic nanoparticles.

For preoperative and intraoperative detection of tumor distribution, numerous multimodal contrast agents, such as magnetic nanoparticles (MNPs) with several examination indicators, are currently in development. However, complex materials, configuration, and cost are required for multimodal contrast agents, accompanied by a high possibility of toxicity and low popularity in clinics. Nevertheless, the magnetic labeling of MNPs using bioprobes should be feasible not only in preoperative magnetic resonance imaging (MRI), but also in intraoperative examination based on other magnetic properties.

Feasibility studies for assaying alpha-fetoprotein using antibody-activated magnetic nanoparticles.

Some previous reports have already shown the characterizations of immunomagnetic reduction (IMR). The assay technology involves the utilities of biofunctionalized magnetic nanoparticles to label target biomolecules. However, the detection threshold and interference tests for IMR have not been investigated in detail.

Exploration of the relationship between the tumor burden and the concentration of vascular endothelial growth factor in liver-cancer-bearing animals using immunomagnetic reduction assay.

To achieve early-stage diagnosis, a high-sensitivity assay method is needed. As a biomarker, vascular endothelial growth factor (VEGF) has played a growing role in diagnosing and treating hepatocellular carcinoma (HCC). In this work, an immunomagnetic reduction (IMR) through bio-functionalized magnetic nanoparticles and a high-temperature superconducting-quantum-interference-device magnetometer were utilized for quantitative detection of low-concentration VEGF in serum from rats with HCC.

Magnetically enhanced high-specificity virus detection using bio-activated magnetic nanoparticles with antibodies as labeling markers.

This study describes magnetically driven suppression of cross-reactions among molecules. First, the magnetic nanoparticles are coated with bio-probes and dispersed in liquid. The bio-probes can then bind with homologous or heterologous bio-targets.

Simultaneous identification of the low-field-induced tiny variation of complex refractive index for anisotropic and opaque magnetic-fluid thin film by a stable heterodyne Mach-Zehnder interferometer.

We use a heterodyne Mach-Zehnder interferometer to simultaneously and simply measure the complex refractive index by only normal incidence on the specimen, instead of using a complicated measurement procedure or instrument that only measures the real or imaginary part of the complex refractive index. To study the tiny variation of the complex refractive index, the small complex refractive-index variation of a rare-concentration magnetic-fluid thin film, due to a weak field of less than 200 Oe, was processed by this interferometer. We also present the wavelength trend of the complex refractive index of magnetic fluids to verify the appearance of the slight change in a small wavelength range.

Ultra-highly sensitive and wash-free bio-detection of H5N1 virus by immunomagnetic reduction assays.

A platform for assaying avian influenza H5N1 viruses that involves measuring the ac immunomagnetic reduction of a magnetic reagent mixed with a detected sample is developed. The magnetic reagent contained magnetic nanoparticles coated with antibodies. To achieve an ultra-high sensitivity assay, a system utilizing a high-transition-temperature superconducting quantum interference device was used to sense the immunomagnetic reduction of the reagents.

Wash-free, antibody-assisted magnetoreduction assays of orchid viruses.

This study demonstrates the feasibility of wash-free magnetoreduction assays (MRA) of orchid viruses. A magnetic reagent, consisting of magnetic beads coated with antibodies and dispersed in water, was synthesized. By using a mixed-frequency alternative-current (ac) magnetosusceptometer, differences in the magnetic susceptibilities of the magnetic reagent before and after the addition of orchid solutions were measured.

Focusing concave lens using photonic crystals with magnetic materials.

The guided modes lying in the upper gap-edge band in the photonic band structure of photonic crystals have negative values of refractive index. This feature generates many interesting optical phenomena, and some spectacular photonic devices such as focusing slabs have been developed. We report the design of a photonic-crystal, planoconcave lens for focusing incident parallel light, and theoretically analyze the chromatic aberrations for TM and TE modes.

Designing optical-fiber modulators by using magnetic fluids.

To reduce interface loss between optical fibers and devices in telecommunication systems, the development of an optical-fiber-based device that can be fused directly with fibers is important. A novel optical modulator consisting of a bare fiber core surrounded by magnetic fluids instead of by a SiO2 cladding layer is proposed. Applying a magnetic field raises the refractive index of the magnetic fluid.

Tunable diffraction of magnetic fluid films and its potential application in coarse wavelength-division multiplexing.

When an external magnetic field is applied parallel to the film surface of a magnetic fluid film, a high-quality one-dimensional periodic chain structure is formed when the field strength reaches a certain level. With a periodic chain structure in the magnetic fluid film, an incident light is diffracted onto the magnetic thin film. The results show that the one-dimensional periodic chain structure in the magnetic fluid film can serve as an optical grating.