Self-Assembled Magnetic Nanoparticle–Graphene Oxide Nanotag for Optomagnetic Detection of DNA

Abstract

In this work, a two-dimensional self-assembled magnetic nanoparticle–graphene oxide (MNP-GO) nanocomposite is reported for the detection of DNA. Single-stranded DNA (ssDNA) coils, generated through a rolling circle amplification (RCA) reaction triggered by the hybridization of target oligos and padlock probes, have a strong interaction with MNP-GO nanotags through several mechanisms including π–π stacking, hydrogen bonding, van der Waals, electrostatic, and hydrophobic interactions. This interaction leads to a hydrodynamic size increase or aggregation of MNP-GO nanotags, which can be detected by a simple optomagnetic setup. Due to the high shape anisotropy, MNP-GO nanotags provide stronger optomagnetic signal than individual MNPs. Moreover, the avoidance of DNA probes (i.e., short ssDNA sequences as the biosensing receptor) provides easier material preparation and lower measurement cost. From real-time measurements of interactions between MNP-GO and RCA products amplified from a highly conserved Escherichia coli 16S rDNA sequence, a limit of detection of 2 pM was achieved with a total assay time of 90 min. Although the nonspecific binding force between GO and ssDNA is much weaker than the specific base-pairing force in a DNA duplex, the proposed method provides a detection limit similar to DNA probe-based magnetic biosensors, which can be ascribed to the abundant binding sites between GO and ssDNA. In addition, for target concentrations higher than 100 pM, the MNP-GO nanotags can be applied for a qualitative naked eye detection strategy based on nanotag–ssDNA flocculation.

Ultrasensitive Real-Time Rolling Circle Amplification Detection Enhanced by Nicking-Induced Tandem-Acting Polymerases

“…Conventional RCA was employed for several of end-point magnetic detection systems, typically involving a hybridization step after amplification to form amplicon coil-aggregated MNPs (Table S3). For reported end-point magnetic biosensors using RCA coils to aggregate MNPs, LODs of 1, 2, 2, 3, and 4 pM were achieved by a ferromagnetic resonance sensor, 35 anisotropic magnetoresistance sensors, 36 an optomagnetic sensor, 37 a superconducting quantum interference device, 38 and an alternating current susceptometer, 39 respectively. The similar LODs achieved by these systems indicate that picomolar sensitivity is typical for conventional RCAbased end-point MNP detection strategies.…”

Magnetic Nanomaterials in Microfluidic Sensors for Virus Detection: A Review

“…The obtained frequency spectra provide information regarding the size of the MNMs in the suspension. Thus, the measurement of the second harmonic component of the transmitted light intensity enables the correlation of optical signals with MNMs size (the optomagnetic signal is stronger in the presence (absorbed to MNMs) than in the absence of analyte) allowing for quantitative and precise assessment of analyte concentrations. − The ability of an external AC magnetic field to rotate the magnetic moment of MNMs and change their size in the presence of target analyte deems the use of optomagnetic sensors a suitable tool for the detection of biomolecules …”

Studying Ni(II) Adsorption of Magnetite/Graphene Oxide/Chitosan Nanocomposite

“…From these experimental results, the concentration of the remaining Ni(II) ions in the solution has been calculated by using the calibration curve, Figure 1(b). Then the amount of Ni(II) ions uptake by FGC (q e , mg.g −1 ) was calculated by using (3).…”

“…However, the disadvantages of graphene sheets are that, in the water environment, they are poorly soluble and tend to aggregate, which significantly reduces the surface area and adsorption capacity. Thus, graphene oxide (GO), the intermediate product of oxidation of graphite, with many oxygen-rich functional groups (epoxy, hydroxyl, and carbonyl groups), is an attractive object for many research areas such as detection of DNA [3], matrix composite membranes, or film [4][5][6], especially in removal of heavy metal ions and organic pollutants from aqueous solutions. In recent years, a number of reports have been published on the adsorption of heavy metal ions by using GO and GO-based materials as an adsorbent.…”