Polyacrylamide Ferrogels with Ni Nanowires

Fabrication of ZnO/ZnAl2O4/Au Nanoarrays through DC Electrodeposition Utilizing Nanoporous Anodic Alumina Membranes for Environmental Application

In this study, anodic aluminum oxide membranes (AAOMs) and Au-coated AAOMs (AAOM/Au) with pore diameters of 55 nm and inter-pore spacing of 100 nm are used to develop ZnO/AAOM and ZnO/ZnAl2O4/Au nanoarrays of different morphologies. The effects of the electrodeposition current, time, barrier layer, and Au coating on the morphology of the resultant nanostructures were investigated using field emission scanning electron microscopy. Energy dispersive X-ray and X-ray diffraction were used to analyze the structural parameters and elemental composition of the ZnO/ZnAl2O4/Au nanoarray, and the Kirkendall effect was confirmed. The developed ZnO/ZnAl2O4/Au electrode was applied to remove organic dyes from aqueous solutions, including methylene blue (MB) and methyl orange (MO). Using a 3 cm2 ZnO/ZnAl2O4/Au sample, the 100% dye removal for 20 ppm MB and MO dyes at pH 7 and 25 °C was achieved after approximately 50 and 180 min, respectively. According to the kinetics analysis, the pseudo-second-order model controls the dye adsorption onto the sample surface. AAOM/Au and ZnO/ZnAl2O4/Au nanoarrays are also used as pH sensor electrodes. The sensing capability of AAOM/Au showed Nernstian behavior with a sensitivity of 65.1 mV/pH (R2 = 0.99) in a wide pH range of 2-9 and a detection limit of pH 12.6, whereas the ZnO/ZnAl2O4/Au electrode showed a slope of 40.1 ± 1.6 mV/pH (R2 = 0.996) in a pH range of 2-6. The electrode's behavior was more consistent with non-Nernstian behavior over the whole pH range under investigation. The sensitivity equation was given by V(mV) = 482.6 + 372.6 e-0.2095 pH at 25 °C with R2 = 1.0, which could be explained in terms of changes in the surface charge during protonation and deprotonation.

Electrochemical sensor based on Fe3O4/α-Fe2O3@Au magnetic nanocomposites for sensitive determination of the TP53 gene

Considering the high cost and tedious process of gene sequencing, there is an urgent need to develop portable and efficient sensors for the TP53 gene. Here, we developed a novel electrochemical sensor that detected the TP53 gene using magnetic peptide nucleic acid (PNA)-modified Fe₃O₄/α-Fe₂O₃@Au nanocomposites. Cyclic voltammetry and electrochemical impedance spectroscopy confirmed the successful stepwise construction of the sensor, especially the high-affinity binding of PNA to DNA strands, which induced different electron transfer rates and resulted in current changes. Variations in the differential pulse voltammetry current observed during hybridization at different surface PNA probe densities, hybridization times, and hybridization temperatures were explored. The biosensing strategy obtained a limit of detection of 0.26 pM, a limit of quantification of 0.85 pM, and a wide linear range (1 pM-1 μM), confirming that the Fe₃O₄/α-Fe₂O₃@Au nanocomposites and the strategy based on magnetic separation and magnetically induced self-assembly improved the binding efficiency of nucleic acid molecules. The biosensor was a label-free and enzyme-free device with excellent reproducibility and stability that could identify single-base mismatched DNA without additional DNA amplification procedures, and the serum spiked experiments revealed the feasibility of the detection approach.

Mechanical and Recyclable Properties of Polyimine Enhanced by Biomimetic Modification of Graphene Oxide Sheets/Silicon Carbide Nano-Whiskers

Inspired by the mineral bridge between hard phase layers of natural nacre, the biomimetic modified silicon carbide nano-whiskers (MSiCw)/graphene oxide sheets (MGO) reinforced polyimine (PI) composites (MSiCw-MGO-PI) were successfully prepared by heat-pressing at room temperature, which confirmed by FTIR, XPS, and XRD tests. According to the results of mechanical tests, the composites with filling weights of MSiCw and MGO, which were found to be 1% and 0.3%, presented tensile strength of 94.27 MPa, which was 32% higher than the matrix. With the additional weights amount of 1%MSiCw and 0.2%MGO, the impact strength of the composites reached 17.46 KJ/m², which was increased by 81% compared with the matrix. In addition, the reinforcing mechanisms, such as the bridging principle and mechanism of whiskers pulling out, were investigated by analyzing the fracture surface of MSiCw-MGO-PI composites. The results showed that MSiCw and MGO can synergistically improve the mechanical properties of the composites. In addition, the recyclability of the composites valued by the mechanical properties of the composites from regrinding and heat pressing showed that three generations of MSiCw-MGO-PI composites can still maintain high mechanical properties on account of the better dispersion of the reinforcing phases in the matrix from regrinding.

High-Performance pH Sensor Electrodes Based on a Hexagonal Pt Nanoparticle Array-Coated Nanoporous Alumina Membrane

Porous anodic alumina membranes coated with Pt nanoparticles (PAAM/Pt) have been employed as pH sensor electrodes for H⁺ ion detection. The PAAM was designed using a two-step anodization process. Pt nanoparticles were then sputtered onto the membrane at different deposition times. The membrane's morphological, chemical, and optical characteristics were carefully assessed following the fabrication stage using a variety of analytical techniques. The potential of the PAAM/Pt sensor electrode was investigated by measuring the potential using a simple potentiometric method. The effects of depositing Pt nanoparticles for 3-7 min on sensor electrode sensitivity were examined. The optimal potentiometric Nernstian response slope for the PAAM/Pt sensor electrode with 5 min Pt sputter coating is 56.31 mV/decade in the pH range of 3.0 to 10 at 293 K. Additionally, the PAAM/Pt sensor electrode's stability and selectivity in various ions solutions were examined. The sensor electrode had a lifetime of more than six weeks and was kept in a normal air environment.

Bioapplications of Magnetic Nanowires: Barcodes, Biocomposites, Heaters

Magnetic nanowires (MNWs) can have their moments reversed via several mechanisms that are controlled using the composition, length, diameter, and density of nanowires in arrays as-synthesized or as individual nanoparticles in assays or gels. This tailoring of magnetic reversal leads to unique properties that can be used as a signature for reading out the type of MNW for applications as nano-barcodes. When synthesized inside track-etched polycarbonate membranes, the resulting MNW-embedded membranes can be used as biocompatible bandaids for detection without contact or optical sighting. When etched out of the growth template, free-floating MNWs are internalized by cells at 37 °C such that cells and/or exosomes can be collected and detected. In applications of cryopreservation, MNWs can be suspended in cryopreservation agents (CPAs) for injection into the blood vessels of tissues and organs as they are vitrified to -200 °C. Using an alternating magnetic field, the MNWs can then be nanowarmed rapidly to prevent crystallization and uniformly to prevent cracking of specimens, for example, as grafts or transplants. This invited paper is a review of recent progress in the specific bioapplications of MNWs to barcodes, biocomposites, and nanowarmers.

Opportunities and challenges in microwave absorption of nickel-carbon composites

In recent years, the problem of electromagnetic wave (EMW) pollution has attracted more and more attention with the development of science and technology. In order to solve this complex problem, the research and development of EMW-absorbing materials is crucial. The new absorbing materials should have the characteristics of light weight, high efficiency, wide bandwidth, environmental protection, oxidation resistance, and other characteristics. Traditional single-phase Ni materials exhibit remarkable ferromagnetic behavior and double-loss mechanisms (dielectric loss and magnetic loss), and are considered as efficient EMW absorbers. However, under the action of EMWs, especially in the GHz frequency band, Ni materials tend to produce an eddy current effect, which limits their application prospects. For Ni-based materials, there is much interest in modifying the composite materials by designing a hierarchical structure for their preparation. Traditional, single-phase, carbon-based materials have been widely used in related fields because of their light weight and good conductivity. However, a single-loss mechanism will affect the impedance matching of carbon materials, thus affecting their application in the field of absorbing waves. For carbon materials, people use them as a filler or matrix material to fabricate composites with metals, metal oxides, or polymer materials to obtain carbon-containing absorbing materials. This paper reviews the evaluation and design principles of the absorbing properties of EMW-absorbing materials. Then, the progress of modified single-phase Ni-based materials (designed materials with 0D, 1D, 2D, and 3D structures), the development of carbon materials (carbon black, carbon nanotubes, carbon fiber, graphite oxide, reduced graphene oxide, and biomedical carbon), and the research progress of Ni-C composite materials (the composite material formed by nickel and carbon) are reviewed. The ultimate goal is to obtain absorbers with light weight, strong absorbing ability, and a wide frequency band. In particular, Ni-MXene, Ni-biomedical carbon, and Ni-multiphase carbon composites are the target direction for designing new and high efficiency EMW absorbers. Finally, the basic challenges and opportunities in this field are discussed.

Realizing the Principles for Remote and Selective Detection of Cancer Cells Using Magnetic Nanowires

The unmet demand for selective and remote detection of biological entities has urged nanobiotechnology to prioritize the innovation of biolabels that can be remotely detected. Magnetic nanowires (MNWs) have been deemed promising for remote detection as the magnetic fields can deeply and safely penetrate into tissue. However, the overlapping nature of the magnetic signatures has been a long-standing challenge for selective detection, which we resolve here. To do so, 13 types of MNWs with unique irreversible switching field (ISF) signatures were synthesized for labeling canine osteosarcoma (OSCA-8) cancer cells (one set) and polycarbonate biopolymers (12 sets). After characterizing the ISF signature of each MNW type, the MNW-labeled cancer cells were transferred onto MNW-labeled biopolymers to determine the most distinguishable ISF signatures and to discern the principles for reliable selective detection of biological entities. We show that tailoring the ISF of MNWs by tuning their coercivity is a highly effective approach for generating distinct magnetic biolabels for selective detection of cells. These findings smooth the path for the progression of nanobiotechnology by enabling the remote and selective detection of biological entities using MNWs.

Selective Detection of Cancer Cells Using Magnetic Nanowires

The main bottleneck for implementing magnetic nanowires (MNWs) in cell-biology research for multimodal therapeutics is the inapplicability of the current state of the art for selective detection and stimulation of MNWs. Here, we introduce a methodology for selective detection of MNWs in platforms that have multiple magnetic signals, such as future multimodal therapeutics. After characterizing the signatures of MNWs, MNWs were surface-functionalized and internalized into canine osteosarcoma (OSCA-8) cancer cells for cell labeling, manipulation, and separation. We also prepared and characterized magnetic biopolymers as multimodal platforms for future use in controlling the movement, growth, and division of cancer cells. First, it is important to have methods for distinguishing the magnetic signature of the biopolymer from the magnetically labeled cells. For this purpose, we use the projection method to selectively detect and demultiplex the magnetic signatures of MNWs inside cells from those inside magnetic biopolymers. We show that tailoring the irreversible switching field of MNWs by tuning their coercivity is a highly effective approach for generating distinct magnetic biolabels for selective detection of cancer cells. These findings open up new possibilities for selective stimulation of MNWs in multimodal therapeutic platforms for drug delivery, hyperthermia cancer therapy, and mitigating cancer cell movement and proliferation.

Unlocking the decoding of unknown magnetic nanobarcode signatures

Magnetic nanowires (MNWs) rank among the most promising multifunctional magnetic nanomaterials for nanobarcoding applications owing to their safety, nontoxicity, and remote decoding using a single magnetic excitation source. Until recently, coercivity and saturation magnetization have been proposed as encoding parameters. Herein, backward remanence magnetization (BRM) is used to decode unknown remanence spectra of MNWs-based nanobarcodes. A simple and fast expectation algorithm is proposed to decode the unknown remanence spectra with a success rate of 86% even though the MNWs have similar coercivities, which cannot be accomplished by other decoding schemes. Our experimental approach and analytical analysis open a promising direction towards reliably decoding magnetic nanobarcodes to expand their capabilities for security and labeling applications.

Facile decoding of quantitative signatures from magnetic nanowire arrays

Magnetic nanoparticles have been proposed as contact-free minimal-background nanobarcodes, and yet it has been difficult to rapidly and reliably decode them in an assembly. Here, high aspect ratio nanoparticles, or magnetic nanowires (MNWs), are characterized using first-order reversal curves (FORC) to investigate quantitative decoding. We have synthesized four types of nanowires (differing in diameter) that might be used for barcoding, and identified four possible "signature" functions that might be used to quickly distinguish them. To test this, we have measured the signatures of several combination samples containing two or four different MNW types, and fit them to linear combinations of the individual type signatures to determine the volume ratios of the types. We find that the signature which determines the ratios most accurately involves only the slope of each FORC at its reversal field, which requires only 2-4 data points per FORC curve, reducing the measurement time by a factor of 10 to 50 compared to measuring the full FORC.

Isolation of Cancer-Derived Exosomes Using a Variety of Magnetic Nanostructures: From Fe3O4 Nanoparticles to Ni Nanowires

Isolating and analyzing tumor-derived exosomes (TEX) can provide important information about the state of a tumor, facilitating early diagnosis and prognosis. Since current isolation methods are mostly laborious and expensive, we propose herein a fast and cost-effective method based on a magnetic nanoplatform to isolate TEX. In this work, we have tested our method using three magnetic nanostructures: (i) Ni magnetic nanowires (MNWs) (1500 × 40 nm), (ii) Fe3O4 nanorods (NRs) (41 × 7 nm), and (iii) Fe3O4 cube-octahedral magnetosomes (MGs) (45 nm) obtained from magnetotactic bacteria. The magnetic response of these nanostructures has been characterized, and we have followed their internalization inside canine osteosarcoma OSCA-8 cells. An overall depiction has been obtained using a combination of Fluorescence and Scanning Electron Microscopies. In addition, Transmission Electron Microscopy images have shown that the nanostructures, with different signs of degradation, ended up being incorporated in endosomal compartments inside the cells. Small intra-endosomal vesicles that could be precursors for TEX have also been identified. Finally, TEX have been isolated using our magnetic isolation method and analyzed with a Nanoparticle tracking analyzer (NanoSight). We observed that the amount and purity of TEX isolated magnetically with MNWs was higher than with NRs and MGs, and they were close to the results obtained using conventional non-magnetic isolation methods.

A Guideline for Effectively Synthesizing and Characterizing Magnetic Nanoparticles for Advancing Nanobiotechnology: A Review

The remarkable multimodal functionalities of magnetic nanoparticles, conferred by their size and morphology, are very important in resolving challenges slowing the progression of nanobiotechnology. The rapid and revolutionary expansion of magnetic nanoparticles in nanobiotechnology, especially in nanomedicine and therapeutics, demands an overview of the current state of the art for synthesizing and characterizing magnetic nanoparticles. In this review, we explain the synthesis routes for tailoring the size, morphology, composition, and magnetic properties of the magnetic nanoparticles. The pros and cons of the most popularly used characterization techniques for determining the aforementioned parameters, with particular focus on nanomedicine and biosensing applications, are discussed. Moreover, we provide numerous biomedical applications and highlight their challenges and requirements that must be met using the magnetic nanoparticles to achieve the most effective outcomes. Finally, we conclude this review by providing an insight towards resolving the persisting challenges and the future directions. This review should be an excellent source of information for beginners in this field who are looking for a groundbreaking start but they have been overwhelmed by the volume of literature.

Projection method as a probe for multiplexing/demultiplexing of magnetically enriched biological tissues

The unmet demand for cheap, accurate, and fast multiplexing of biomarkers has urged nanobiotechnology to prioritize the invention of new biomarkers that make feasible the remote detection, identification, and quantification of biological units, such as regenerative tissues. Here, we introduce a novel approach that highlights magnetic nanowires (MNWs) with such capabilities. This method employs the stable magnetization states of MNWs as a unique characteristic that can be realized by projecting the MNWs' switching field on the backward field (P_Hb), also known as the irreversible switching field. Experimentally, several types of MNWs were directly synthesized inside polycarbonate tissues and their P_Hb characteristics were measured and analyzed. Our results show that the P_Hb gives an excellent identification and quantification characteristic for demultiplexing MNWs embedded in these tissues. Furthermore, this method significantly improves the characterization speed by a factor of 50×–100× that makes it superior to the current state of the art that ceased the progression of magnetic nanoparticles in multiplexing/demultiplexing applications.

Different polycarbonate tissues were enriched using magnetic nanowires with diverse magnetic signatures. Projection method successfully identifies and quantifies the complex combinations of the magnetically enriched polycarbonate tissues.