Emission of nitrous oxide and methane from alluvial soil through incubation

Methane and nitrous oxide emission from alluvial soil under incubation using varying doses of urea and water content were studied for Tangibanta and Sorada. The N2O emission was observed to increase with time and tapers off after attaining the peak. The theoretical emission was evaluated using empirical equations and matches well with the experimental values. The CH4 and N2O emission both increased with the increase in Water Filled Pore Space (WFPS) and urea concentration. The nitrification and denitrification reaction rates were determined with and without acetylene. Michaelis-Menten equation was used to evaluate the Km and Vmax values. The rate of emission of N2O increased with increase of WFPS and urea concentration whereas the emission factor showed a reverse trend. The CH4 emission rate was observed to be comparatively low with respect to N2O emission rate around a factor of 10. First published online: 14 May 201

Functionalization of Biotinylated Polyethylene Glycol on Live Magnetotactic Bacteria Carriers for Improved Stealth Properties

The early removal of drug delivery agents before reaching the affected target remains an area of interest to researchers. Several magnetotactic bacteria (MTB) have been used as self-propelled drug delivery agents, and they can also be controlled by an external magnetic field. By attaching the PEG–biotin polymer, the bacteria are turned into a stealth material that can escape from the phagocy-tosis process and reach the area of interest with the drug load. In the study, we developed a potential drug carrier by attaching the PEG–biotin to the MTB-through-NHS crosslinker to form a MTB/PEG– biotin complex. The attachment stability, efficacy, and bacterial viability upon attachment of the PEG– biotin polymer were investigated. Biological applications were carried out using a cytotoxicity assay of THP-1 cells, and the results indicate that the MTB/PEG–biotin complex is less harmful to cell viability compared to MTB alone. Along with cytotoxicity, an assay for cell association was also evaluated to assess the complex as a potential stealth material. The development of these complexes focuses on an easy, time-saving, and stable technique of polymer attachment with the bacteria, without damaging the cell’s surface, so as to make it a strong and reliable delivery agent. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.1

Performance Validation of a Planar Hall Resistance Biosensor through Beta-Amyloid Biomarker

Magnetic sensors have great potential for biomedical applications, particularly, detection of magnetically-labeled biomolecules and cells. On the basis of the advantage of the planar Hall effect sensor, which consists of improved thermal stability as compared with other magnetic sensors, we have designed a portable biosensor platform that can detect magnetic labels without applying any external magnetic field. The trilayer sensor, with a composition of Ta (5 nm)/NiFe (10 nm)/Cu (x = 0 nm~1.2 nm)/IrMn (10 nm)/Ta (5 nm), was deposited on a silicon wafer using photolithography and a sputtering system, where the optimized sensor sensitivity was 6 μV/(Oe∙mA). The detection of the magnetic label was done by comparing the signals obtained in first harmonic AC mode (1f mode) using an external magnetic field and in the second harmonic AC mode (2f mode) with a self-field generated by current passing through the sensor. In addition, a technique for the β-amyloid biomarker-based antibody-antigen sandwich model was demonstrated for the detection of a series of concentrations of magnetic labels using the self-field mode method, where the signal-to-noise ratio (SNR) was high. The generated self-field was enough to detect an immobilized magnetic tag without an additional external magnetic field. Hence, it could be possible to reduce the device size to use the point-of-care testing using a portable circuit system.1

Facile and scalable preparation of bovine serum albumin stabilized cobalt sulfide nanostructures with various morphologies

We present a protein-assisted method for the facile and scalable synthesis of Cobalt sulfide (CoS) nanostructures with various morphologies using bovine serum albumin (BSA) as a stabilizing agent. The CoS samples prepared from 10:1 volume ratio of Cobalt (Co):Sulfur (S) and 1:10 volume ratio of Co:S at 0.01% w/v amount of BSA shows 3D flowers with an average diameter of 510 nm and hollow spheres about 900 nm in average diameter, respectively. The CoS samples prepared from 0.01, 0.1 and 0.5% w/v amounts of BSA at 1:1 volume ratio of Co:S shows nanosheet based porous clusters, nanosheet based partially porous clusters and aggregated spheres, respectively. Fourier transform infrared spectroscopy study confirms that the obtained BSA stabilized CoS nanostructures are stabilized by hydroxyl and amine groups present in the BSA molecules. © 2021 Elsevier B.V.1

Magnetophoretic Decoupler for Disaggregation and Interparticle Distance Control

The manipulation of superparamagnetic beads has attracted various lab on a chip and magnetic tweezer platforms for separating, sorting, and labeling cells and bioentities, but the irreversible aggregation of beads owing to magnetic interactions has limited its actual functionality. Here, an efficient solution is developed for the disaggregation of magnetic beads and interparticle distance control with a magnetophoretic decoupler using an external rotating magnetic field. A unique magnetic potential energy distribution in the form of an asymmetric magnetic thin film around the gap is created and tuned in a controlled manner, regulated by the size ratio of the bead with a magnetic pattern. Hence, the aggregated beads are detached into single beads and transported in one direction in an array pattern. Furthermore, the simultaneous and accurate spacing control of multiple magnetic bead pairs is performed by adjusting the angle of the rotating magnetic field, which continuously changes the energy well associated with a specific shape of the magnetic patterns. This technique offers an advanced solution for the disaggregation and controlled manipulation of beads, can allow new possibilities for the enhanced functioning of lab on a chip and magnetic tweezers platforms for biological assays, intercellular interactions, and magnetic biochip systems. © 2021 The Authors. Advanced Science published by Wiley-VCH GmbH1

Tailored Micromagnet Sorting Gate for Simultaneous Multiple Cell Screening in Portable Magnetophoretic Cell-On-Chip Platforms

Conventional magnetophoresis techniques for manipulating biocarriers and cells predominantly rely on large-scale electromagnetic systems, which is a major obstacle to the development of portable and miniaturized cell-on-chip platforms. Herein, a novel magnetic engineering approach by tailoring a nanoscale notch on a disk micromagnet using two-step optical and thermal lithography is developed. Versatile manipulations are demonstrated, such as separation and trapping, of carriers and cells by mediating changes in the magnetic domain structure and discontinuous movement of magnetic energy wells around the circumferential edge of the micromagnet caused by a locally fabricated nano-notch in a low magnetic field system. The motion of the magnetic energy well is regulated by the configuration of the nanoscale notch and the strength and frequency of the magnetic field, accompanying the jump motion of the carriers. The proposed concepts demonstrate that multiple carriers and cells can be manipulated and sorted using optimized nanoscale multi-notch gates for a portable magnetophoretic system. This highlights the potential for developing cost-effective point-of-care testing and lab-on-chip systems for various single-cell-level diagnoses and analyses

A novel approach for the synthesis of ultrathin silica-coated iron oxide nanocubes decorated with silver nanodots (Fe3O4/SiO2/Ag) and their superior catalytic reduction of 4-nitroaniline

A novel sonochemical approach was developed for the synthesis of different core/shell structures of Fe<inf>3</inf>O<inf>4</inf>/SiO<inf>2</inf>/Ag nanocubes and SiO<inf>2</inf>/Ag nanospheres. The total reaction time of the three sonochemical steps for the synthesis of Fe<inf>3</inf>O<inf>4</inf>/SiO<inf>2</inf>/Ag nanocubes is shorter than that of the previously reported methods. A proposed reaction mechanism for the sonochemical functionalization of the silica and the silver on the surface of magnetic nanocubes was discussed in detail. Transmission electron microscopy revealed that the surface of Fe<inf>3</inf>O<inf>4</inf>/SiO<inf>2</inf> nanocubes was decorated with small Ag nanoparticles of approximately 10-20 nm in size, and the energy dispersive spectroscopy mapping analysis confirmed the morphology of the structure. Additionally, X-ray diffraction data were used to confirm the formation of both phases of a cubic inverse spinel structure for Fe<inf>3</inf>O<inf>4</inf> and bcc structures for Ag in the core/shell structure of the Fe<inf>3</inf>O<inf>4</inf>/SiO<inf>2</inf>/Ag nanocubes. The as-synthesized Fe<inf>3</inf>O<inf>4</inf>/SiO<inf>2</inf>/Ag nanocubes showed a high efficiency in the catalytic reduction reaction of 4-nitroaniline to 4-phenylenediamine and a better performance than both Ag and SiO<inf>2</inf>/Ag nanoparticles. The grafted silver catalyst was recycled and reused at least fifteen times without a significant loss of catalytic efficiency. © The Royal Society of Chemistry.

Microvalve-controlled miniaturized electrochemical lab-on-a-chip based biosensor for the detection of β-amyloid biomarker

Recently, miniaturized electrochemical biosensors have the advantage of real-time monitoring and label-free detection of biomarkers. However, controlled manipulation of reagent samples for specific immobilization of biomarkers remains a challenge to attend high-resolution microfluidic biosensor. Here, we designed a microfluidic channel and valves integrated electrochemical biosensor for the detection of β-amyloid (1–42) biomarker, one of the most neurotoxic peptides present in the cerebrospinal fluid, and a possible marker for the detection of Alzheimer's disease. The formation of the antibody-antigen complexes on gold microelectrode integrated inside the fluidic chambers was presented in the developed biosensor, and all the measurements are carefully controlled using pneumatic valves integrated with the device. The demonstrated microfluidic electrochemical biosensor exhibits a linear response towards various β-amyloid antigen concentrations from 2.2 pM to 22 μM, with an enhanced detection limit of 1.62 pM. The developed technology offers an advantage of minimal reagent sample and suitable environment for miniaturized and sensitive detection of biomarkers, could also be used for the detection of other biomarkers with high efficiency. © 2021 The Korean Society of Industrial and Engineering Chemistry1

Electrochemical synthesis of co-rich nanowires for barcodes

We synthesized three types of magnetic nanowires (Co-Ni-P, Co-Pt-P, and Co-Fe-P) by electrochemical deposition in polycarbonate membranes for use in magnetic barcodes. The nanowires were about 50 nm in diameter and 6 μm in length. The Co-Pt-P nanowires had the highest coercivity and remanence. We used finite elements to calculate the spatial distribution of the stray magnetic fields produced by the barcodes. The Co-Pt-P had the greatest spatial variation which makes it the best composition for the hard magnetic segment of barcode nanowires. These barcode nanowires may be used for magnetic multiplexing detection. © 2010-2012 IEEE.1

Highly sensitive electrochemical biosensor based on naturally reduced rGO/Au nanocomposite for the detection of miRNA-122 biomarker

Herein, we have developed a novel high-resolution electrochemical biosensor for the detection of the microRNA-122 (miRNA-122) using gold nanoparticles dotted reduced graphene oxide (rGO/Au) nanocomposite. The natural soapnut solution was used as a reducing agent for the synthesis of the nanocomposite. The naturally reduced rGO/Au nanocomposite was confirmed through various characterization techniques. When rGO/Au nanocomposite was coated on to the gold electrode and checked the electrochemical performance, the nanocomposite shows superior analytical performance. The probe DNA was anchored onto the binding sites of rGO/Au nanocomposite through thiol linker and recognized the target miRNA-122. The developed rGO/Au based electrochemical biosensor demonstrated a linear response for various target miRNA-122 concentrations with a range from 10 μM to 10 pM and, with a detection limit of 1.73 pM. The developed biosensor also shows good stability and reproducibility, could be used for the detection of miRNA-122 and, also can be used for the basic research and clinical studies. Besides, the demonstrated rGO/Au nanocomposite-based sensing strategy could be used to detect various miRNA and protein biomarkers. Furthermore, the green synthesis approach could also be useful for the synthesis of various nanomaterials and nanocomposites for various biomedical applications. © 2020 The Korean Society of Industrial and Engineering Chemistry1