Magnetic Separation Research Articles

The Added Value of Copper and Silver Metal from Printed Circuit Boards Waste Using Davis Tube with Variations of Size and Magnetic Intensity

The widespread use of electronic devices has led to a significant increase in electronic waste, including PCB (printed circuit board) waste. PCBs contain valuable metals like copper and silver, which can be reclaimed and reused. Recently, there has been a growing demand for urban mining processes to extract electronic waste PCB Flame Retardant-2 (FR-2) from laptops and computers. During the urban mining process, PCB FR-2 waste undergoes various physical treatments such as dismantling, crushing, and concentration processes. One of the concentration processes involves magnetic separation using a Davis tube. This study aims to investigate the effects of size and magnetic intensity variations on the recovery of copper and silver levels in FR-2 PCB waste. The magnetic concentration process was carried out using different size ranges (-63+100#, -100+150#, -150#) and magnetic intensities (1000 G, 2000 G, 3000 G). The results indicated that the most effective size for separating copper and silver is -63+100# and the optimal magnetic intensity is 1000 G. This resulted in copper and silver content of 45.66% and 0.162%, with recoveries of 80.135% and 62.505% respectively.

Integration of experimental study and neural network modeling for estimating iron recovery in Davis tube tests

Magnetic separation is a common procedure for the enrichment of magnetic iron ores. Davis tube (DT) test is a standard laboratory technique used to determine the optimum magnetic recovery of iron ore using wet low-intensity magnetic separators. However, the DT test is time-consuming and labour-intensive. In this study, based on the results of DT-tests, generalized regression (GRNN) and radial basis function (RBF) neural networks were developed to predict iron recovery through the Fe and FeO content of the feed. First, the DT tests were performed on 613 iron ore samples with varying Fe and FeO content. Then, neural networks were used to model the iron recovery from the DT test, using the Fe and FeO content of the feed as input data. The modeling results showed that GRNN is a better model for predicting iron recovery. The main statistical metrics indicated that GRNN has AAPRE, RMSE, and R2 values of 3.929%, 2.804, and 0.976 respectively for a total of 613 data points. Moreover, sensitivity analysis demonstrated that iron recovery is directly influenced by both Fe and FeO contents, with FeO content having a more pronounced effect. Finally, Leverage analysis showed that GRNN is highly reliable for predicting iron recovery, with only 2.77% of data points flagged as suspicious based on outlier estimation.

Development of an Ultrasensitive Competitive Double-Enzyme Cascade Fluorescence Signal Amplification Method for Factor XIa Inhibitor Screening.

Coagulation factor XIa (FXIa) is associated with a low risk of bleeding and has been identified as an effective and safe target for the development of novel anticoagulant drugs. In this study, we established an ultrasensitive competitive dual-enzyme cascade signal amplification method for the quantitative analysis and screening of FXIa inhibitors. Due to the specific recognition of FXIa's active site by the aptamer AptE40, the AptE40-QDs-EK recognition probe modified with enterokinase (EK) and the aptamer AptE40, was attached to the MNPs-FXIa capture probe. When FXIa inhibitor was present, it competed with AptE40 for binding to FXIa, resulting in the detachment of AptE40-QDs-EK from MNPs-FXIa. After magnetic separation, the enterokinase of AptE40-QDs-EK in the supernatant hydrolyzed N-terminal hexapeptide of trypsinogen, leading to the production of a large amount of trypsin as part of the first-stage signal cascade amplification. Next, trypsin could hydrolyze the hexameric arginine peptide (RRRRRR, R6), leading to the dissociation of RQDs from the R6-RQDs signal probe; this resulted in a dramatic increase in the fluorescence intensity of the supernatant as the second-stage signal cascade was amplified. The feasibility of the method was investigated using the FXIa inhibitor aptamer FELIAP as a positive model drug. Furthermore, the method was applied to screen the FXIa inhibitors in Eupolyphaga sinensis Walker. Two fractions with more active anticoagulated ingredients were successfully identified and validated via the conventional method, and the results were consistent. The established method provides a key technique for the sensitive detection, high-throughput analysis, and screening of the FXIa inhibitors.

Selection of antibacterial aptamers against Pseudomonas plecoglossicida and analysis on their potential binding proteins

Pseudomonas plecoglossicida is one of the main pathogens causing visceral white spot disease of the large yellow croaker (Pseudosciaena crocea). Although antibiotics are used to control P. plecoglossicida infections, the long-term and large-scale use of antibiotics can lead to the development of drug-resistant bacteria as well as environmental pollution. Therefore, it is necessary to develop novel antibacterial agents to treat P. plecoglossicida infections. In this study, we first developed a two-step-centrifugation method to isolate live and dead P. plecoglossicida cells. Subsequently, we used the Systematic Evolution of Ligands by Exponential Enrichment (SELEX) screening based on inhibition rate to directly isolate antibacterial aptamers from the random library without post-processing. We isolated five antibacterial aptamers, namely B1, B2, B4, B8, and B109, which showed good inhibitory effects against P. plecoglossicida. Among these, B4 showed the highest inhibitory effect (62.40 ± 4.17 %). Further analysis revealed no positive correlation between the inhibitory effect of aptamers and their affinities with the target bacterium. The B4- and B109-binding proteins were isolated from P. plecoglossicida by magnetic separation and sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE). Mass spectrometry analysis revealed that the 26 kDa ribosomal protein L2 was the probable B4-binding protein, while the 26 kDa ribosomal protein S3 and 75 kDa ribosomal protein S1 or succinate dehydrogenase flavoprotein subunit were the probable B109-binding proteins. Structural and subcellular localization analyses of these potential B4- and B109-binding proteins were also conducted. Our findings suggest that the inhibitory activity of the antibacterial aptamers against P. plecoglossicida may be mediated via their interaction with the ribosomal proteins, which can interfere with the protein synthesis process in the bacterium, affecting its growth. These findings provide the scientific basis for the development of functional antibacterial aptamers and the elucidation of their mechanisms of action.

Magnetic Separation of Schwann Cells from Mouse Sciatic Nerves

Magnetic Separation of Schwann Cells from Mouse Sciatic Nerves

Magnetic Separation of Schwann Cells from Mouse Sciatic Nerves

Magnetic Separation of Schwann Cells from Mouse Sciatic Nerves

Enhanced removal of nanoplastics from freshwater using in-situ synthesized and anchored nano-Fe3O4 via two-step ferrous oxidation

Magnetic separation is a promising strategy for removing nanoplastics (NPs) from water; however, it often requires complex processeses, such as synthesizing nano-Fe3O4 magnets and attaching them to specific carriers. This study presents an innovative and efficient strategy to in-situ synthesize and anchor nano-Fe3O4 onto polystyrene (PS) NPs through a two-step oxidation of ferrous ions, which significantly enhances NPs removal via magnetic separation. The two-step process involves initial alkalization of a ferrous aqueous solution under anoxic conditions, followed by oxidation in air. In the presence of PS spheres, nano-Fe3O4 forms in-situ on the PS surfaces, promoting sedimentation under a magnetic field. Results demonstrate that two-step ferrous oxidation achieves superior removal rates, with 99.32 % for 500 nm PS spheres (PS-500) and 93.16 % for 100 nm PS spheres (PS-100) using a low Fe2+ dosage of 0.1 mM. In contrast, the conventional one-step method, which simultaneously alkalizes and oxidizes ferrous sulfate in aerobic conditions, fails to form nano-Fe3O4 and results in low removal rates of only 56.49 % for PS-500 and 8.89 % for PS-100, respectively. Furthermore, the turbidity and residual Fe can be reduced to below 1 NTU and 0.1 mg/L by using two-step process, respectively, meeting drinking water safety and hygiene standards. This approach not only simplifies the magnetic nanomaterial preparation process but also substantially improves the NP removal efficiency, offering a promising solution for enhanced water treatment technologies and safer drinking water.

Globular Antifreeze Protein-Inspired Nanoparticle-Based Large-Scale T-Cell Cryoprotection System for Lymphoma Immunotherapy.

Large-scale biosafe T-cell cryopreservation is required to bring T-cell therapies to the market, but it remains challenging due to the cytotoxicity of common cryoprotectants [e.g., dimethyl sulfoxide (DMSO)] and unavoidable ice injuries to cells. Herein, inspired by natural globular antifreeze proteins, we establish a biocompatible zwitterionic magnetic nanoparticle (ZMNP)-based cryoprotection system, achieving large-scale cryopreservation of T cells for lymphoma immunotherapy. ZMNPs could form a globular hydration shell to inhibit water molecule aggregation as well as ice growth, and the surficial hydration strength-antifreeze performance relationship of ZMNPs was investigated. During the thawing process, ZMNPs possessed a magnetic field-mediated nanowarming property that enabled rapid heating and also facilitated easy magnetic separation for cell recovery. These combined effects resulted in a high post-thaw viability (>80%) of large-scale T-cell cryopreservation (20 mL). Notably, post-thaw T cells exhibited similar transcript profiles to fresh cells, while up- or downregulation of 1050 genes was found in the DMSO group. In a mouse E.G7-OVA lymphoma model, ZMNP-system-cryopreserved T cells achieved a tumor suppression rate of 77.5%, twice as high as the DMSO group. This work holds great promise for the application of advanced cryopreservation techniques in the development of therapeutic cellular products.

How magnetism-based fractional spinels contribute to the bioavailability of geogenic chromium in serpentine soils of Taiwan

Serpentine soils are highly rich in geogenic chromium (Cr), typically associated with spinel minerals. The high resistance of these minerals to weathering has raised concerns regarding their contribution to Cr bioavailability in serpentine soils. This study collected soil horizon samples from two pedons (Entisol and Ultisol) in eastern Taiwan and applied a two-step magnetic separation method to divide the bulk soils into strongly magnetic (SM), weakly magnetic (WM), and nonmagnetic (NM) fractions. The basic characteristics of the bulk soils were examined. To characterize the mineralogy and geochemistry of the fractions and determine their quantitative contribution of bioavailable Cr in serpentine soils, we analyzed their mineral composition, magnetic properties, and elemental composition and valence by using various spectrometric techniques, such as X-ray diffraction, electron probe microanalysis, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy, as well as vibrating sample magnetometry. The results indicated the main Cr-bearing minerals were magnetite and chromite in the SM and WM fractions, with minor occurrences in layer silicates, such as serpentine and chlorite, in the NM fraction. The total Cr content decreased in the following order: SM > WM > NM. The SM fraction had the lowest weight proportion, and this proportion was lower for the Ultisol than the Entisol. This observation indicated that the weathering of Cr spinels is associated with the substantial cation substitution of Al, Ca, Mn, and Ni for Fe and Cr in broken mineral grains and increases in the Fe(III) and Cr(VI) concentrations in magnetite. The SM fraction, mainly consists of magnetite and chromite, exhibited the highest concentration of bioavailable Cr extracted by 0.1 M HCl. However, the Cr-bearing layer silicates represented the largest potential pool of bioavailable Cr in the bulk soils because the weight proportion of the NM fraction was higher than those of the other fractions and increased during pedogenesis.

Cu(II) complex heterogenized on magnetic mesoporous nanocomposite (SBA-16@Fe3O4) as an efficient catalyst for the reduction of nitro compounds

In the present study, a novel magnetic heterogeneous copper catalyst was developed by the immobilization of a Cu(II) complex on the surface of magnetic mesoporous nanocomposite (SBA-16@Fe3O4) through post-synthetic method. The synthesized catalyst was analyzed by various characterization methods including FT-IR, EDS, XRD, Nitrogen physisorption, TEM, TGA, VSM, and ICP-OES. After complete characterization, its catalytic efficiency was evaluated in the hydrogenation of nitroarenes to amines. Taking the nitrobenzene reduction of as an example of a reaction, the reaction conditions were optimized by changing diverse parameters like solvent, temperature, time, amount of catalyst, as well as the type and amount of hydrogen source. The catalyst revealed highly efficient catalytic activity in the hydrogenation of numerous nitroarenes to the corresponding aminoarenes in pure water as the solvent with sodium borohydride as a H2 source at room temperature. Additionally, the catalyst could be simply recovered from the mixture of reaction via magnetic separation and was able to mediate the reaction for multiple times with undiminished catalytic performance.

"Hedgehog Ball"-Shaped Nanoprobes for Multimodal Detection and Imaging of Inflammatory Markers in Osteosarcoma Using Fluorescence and Electrochemiluminescence.

Inflammation can affect the progression of cancer at tumor sites, such as in osteosarcoma, by intensifying metastasis and complicating outcomes. The current diagnostic methods lack the specificity and sensitivity required for early and accurate detection, particularly in differentiating between inflammation-induced changes and tumor activities. To address this, a novel "hedgehog ball"-shaped nanoprobe, Fe3O4@Au-pep-CQDs, was developed and designed to enhance the detection of caspase-1, a key marker of inflammation. This magnetic nanoprobe facilitates simultaneous fluorescence (FL) and electrochemiluminescence (ECL) detection. Magnetic separation minimizes the quenching of nanoparticles in solution and eliminates the need for frequent electrode replacement in ECL tests, thereby simplifying diagnostic procedures. The experimental results showed that in the detection of caspase-1, the nanoprobe had a detection limit of 0.029 U/mL (FL) and 0.033 U/mL (ECL) and had a dynamic range of 0.05 to 1.0 U/mL. Additionally, the nanoprobe achieved high recovery rates of 94.36 to 102.44% (FL) and 94.36-100.12% (ECL) in spiked biological samples. Furthermore, the nanoprobe's capabilities were extended to in vivo bioimaging to provide direct, intuitive visualization of biological processes. These novel nanoprobes were able to significantly enhance the accurate detection of inflammation at tumor sites, thereby optimizing both diagnostic and therapeutic strategies.

Magnetic field simulation and analysis of superconducting magnetic separator with different magnetic matrices

Superconducting magnetic separation technology leverages strong magnetic fields to separate magnetic from non-magnetic materials, vital for industries like mining, recycling, and water treatment. This study aims to elucidate the impact of various magnetic gathering media on the magnetic field distribution within superconducting magnetic separators through detailed modeling and simulation. Using Infolytica MagNet software, we simulate the magnetic field distribution of a JS-6-102 pilot-scale superconducting magnetic separator, both without media and with different magnetic matrices, such as mesh and rod media. Our results reveal that the presence of magnetic matrices significantly alters the magnetic field distribution, enhancing magnetic induction intensity and affecting field uniformity. We demonstrate that smaller mesh sizes yield more uniform magnetic fields, while larger rod diameters increase magnetic field distortion. These findings contribute to optimizing the design and efficiency of superconducting magnetic separation systems.

Automated ECL Aptasensing Platform from an Intrarticular Radical Annihilation Route for Distinguishing Glioma Stages.

Nowadays, continuous efforts have been devoted to designing stable and high-efficiency electrochemiluminescence (ECL) emitters as alternatives for tris(2,2'-bipyridine)-ruthenium(II) (Ru(bpy)32+) in medical research. Herein, a novel ECL emitter was obtained by coordinating crystalline covalent triazinyl frameworks (cCTFs) with Ru2+ (termed Ru-cCTFs), which exhibited strong ECL emission by the ligand to metal charge transfer (LMCT) route. After its integration with 4-mercaptopyridine (SH-Py), the resultant SH-Py-Ru-cCTFs achieved 2.3-fold enhancement in the ECL efficiency by employing Ru(bpy)32+ as a standard, which involved a dynamic "intrarticular radical annihilation" ECL pathway. On such foundation, an automated ECL (A-ECL) aptasensor was constructed with an "on-off-on" model and magnetic separation upon linkage of the SH-Py-Ru-cCTFs with streptavidin (SA) magnetic beads (MBs). This automatic assay of miRNA-182 showed a wider linear range from 1.0 to 100.0 fM with a correlation coefficient (R2) of 0.994, a lower limit of detection (LOD) down to 0.28 fM, and faster operation within 41 min. Impressively, this bioassay facilely distinguished the stages of glioma disease from clinical blood samples with high accuracy. Hence, this research sheds light on how to develop advanced ECL luminophores and an automatic method, showing substantial insights into pathogenesis research of gliomas.

Apple Tree Root‐Derived Biochar/Iron Oxide Triphasic Nanocomposite for Wastewater Treatment and Microwave Absorption

AbstractIn this work, two major sources of pollution: (1) Water pollution due to heavy metals, and (2) Electromagnetic wave (EMW) pollution, often regarded as the fourth category of pollution (after air, water, and soil pollution) are addressed. A unique bio‐based triphasic nanocomposite (Fe3O4/α‐Fe2O3/carbon) is synthesized and its superior properties are demonstrated to address both types of environmental pollution. The nanocomposite, derived from lightweight apple tree roots, is used for Pb (II) ion removal from aqueous solutions via adsorption and magnetic separation. The biomass‐derived highly porous biochar decorated with iron‐oxide showed adsorption efficiency of nearly 100% and corresponding capacity of 149 mg.g−1 under optimal conditions for initial Pb (II) concentration of 50 mg.L−1. Furthermore, a remarkable adsorption capacity of 731 mg.g−1 is achieved using lower amount of the adsorbent for a slightly lower efficiency (97%). In addition, the mesoporous composite showed excellent EMW absorption efficiency with effective absorption bandwidth of 7.8 GHz and reflection loss of −61.7 dB, arising from very good impedance matching, and high dielectric and magnetic losses. This work establishes the multifunctional properties of the synthesized composite, and addresses the UN Sustainable Development Goal (SDG) 6 (Clean water and sanitation) and SDG 13 (Climate action, including pollution management).

Flash combustion prepared Sm and Co doped Sr hexaferrite for environmental applications

Nanotechnology is offering solutions to water contamination issues, as new techniques are needed to improve the removal of harmful compounds from water bodies. Despite previous reviews on this topic, nanotechnology is paving the way for more effective water treatment methods. Understanding the substitute influence of divalent Co2+ and rare earth elements Sm3+ on the structure, magnetic, and removal efficiency of hexagonal ferrites requires an understanding of a sequence of SrFe12O19, SrFe11.5Co0.5O19, Sr0.95Sm0.05Fe12O19, and Sr0.95Sm0.05Fe11.5Co0.5O19 M-type hexagonal ferrites were prepared using the flash technique. The XRD examination revealed that the crystallized material formed a single M-type hexagonal phase. The characteristics of M-type hexagonal ferrites include absorption bands with low wavenumbers in the FTIR curves between 400 to 1000 cm−1. There was a variation in magnetic characteristics with the replacement of Sm3+ and Co2+ doping, possibly due to the spin canting impact created by rare earth Sm3+ and Co2+ ions. The goal of the research is to explore the potential of doping magnetic hexaferrites and its influence in wastewater treatment. Various parameters, such as pH and contact duration, that influence the adsorption of lead ions from aqueous solutions were also examined. At pH 7 and 25 °C after 70min, the maximal removal efficiency of the Sr0.95Sm0.05Fe11.5Co0.5O19 was found to be 99%. Magnetic separation was carried out by applying an external magnetic field using a permanent magnet. The strong magnetization of the ferrites (51–58 emu/g) enabled the rapid separation of the magnetic particles from the solution, with over 95% of the ferrite particles being recovered within 10 to 70 min. The Freundlich isotherm model fitted all the isotherm data. Adsorption kinetics were explained by the pseudo-first-order, pseudo-second order, and intraparticle diffusion models. The investigated samples’ adsorption capacity remained efficient till 5 cycles.

Mechanism analysis of enhanced desulfurization of pulverized coal through high-gradient magnetic separation with microwave radiation

Dry high gradient magnetic separation technology is a low-carbon green technology. It can be embedded in a power plant to remove coal pyrite with a high-efficiency magnetic separator and remarkable magnetic properties difference between coal pyrite and coal matrix. This study selected the microwave radiation method to improve the magnetic properties difference and carried out a desulfurization experiment with a self-developed high-gradient permanent magnetic separator using the tapered iron auxiliary magnetic pole. The results demonstrate that the pyrite content and specific magnetic susceptibility increase with the decrease in particle size. The desulfurization rate did not change significantly at 25 °C. The coal sample began to appear in the thermal reaction at 450 °C, and the pyrite can become a strong magnetic property pyrrhotite. The desulfurization rate can achieve 58.70 % at 700 °C, and is equivalent to the wet washing index, due to the supply of high magnetic field force. The dynamic characteristic response of magnetic particles becomes more obvious with short time adsorption, and the probability of carrying non-magnetic particles is reduced. This study demonstrates that the high-gradient magnetic separation technology of pulverized coal enhanced by microwave irradiation is feasible.

A review of the engineered treatment of red mud: Construction materials, metal recovery, and soilization revegetation

Red mud, known as bauxite residue, is an alkaline solid waste generated during alumina production. Globally, the stockpile of red mud is about 3 billion tons and is increasing at a rate of 150 million tons per year. The global production of red mud is mainly distributed in China (28.2 %), Oceania region (22.4 %), South America (14.6 %), Europe (12.9 %), and North America (8.8 %). The increasing stockpile of red mud has posed a huge challenge to safe disposal while restricting the development of the alumina industry. The comprehensive utilization of red mud still needs green, efficient, and massive consumption methods. This work gives a review of the engineered treatment of red mud, including the characteristics and threats, as well as the engineered application through construction materials, metal recovery, and soilization revegetation. For red mud with a high content of metals, resource recovery of valuable metals and rare earth elements is a preferred choice, meeting the circular economy concept. Recovery of valuable metals from red mud can be achieved by magnetic separation, hydrometallurgy, and bioleaching. Hydrometallurgy is promising for recovering valuable metals such as Fe, Al, V, Ti, and rare earth elements, and the recovery is up to 99 %. Construction materials such as cement, geopolymers, and ceramics is an efficient alternative for the massive consumption of red mud, and the high-performance concrete with the compressive strength (129.5 MPa) can be obtained. This strategy is limited by the low price of construction materials, the lowered quality by alkaline components, and potential threats of toxic elements in red mud. Soilization of red mud with ecological restoration is promising for the sustainable management of red mud dam. To accelerate the process of red mud soilization, amendments such as gypsum, organic matter, and microorganisms can be added to neutralize red mud (lowering pH from 10 to 12 to near 7), promote the formation of agglomerates, and provide nutrients, promote the conversion of red mud into soil-like substrate. The phytoremediation of red mud can be realized after effective regulation, finally realizing vegetation establishment of red mud. This work provides technological and practical guidance for the engineered disposal of red mud.

Phage LysSA163-CBD mediated specific recognition coupled with ATP bioluminescence for the sensitive detection of viable Staphylococcus aureus in food matrices

BackgroundStaphylococcus aureus is a significant foodborne pathogen, commonly detected in milk and meat products. Conventional detection methods have limited sensitivity and specificity, which are time-consuming and susceptible to background interference from complex samples, and cannot effectively distinguish live and dead bacteria. ResultsHerein, we developed a novel adenosine triphosphate (ATP) bioluminescence method coupled with magnetic separation, which is based on phage-encoded endolysin LysSA163-CBD (CBD 163) for rapid and specific detection of viable Staphylococcus aureus. The expressed protein (CBD 163) was derived from the phage LSA2301 and was successfully expressed in Escherichia coli BL21 following an induction period of 4 h at 37 °C, with a molecular weight approximating 40 kDa. The optimal conditions for CBD-magnetic beads (cMBs) to capture S. aureus cells were determined to be 100 μL/mL cMBs at 25 °C for 30 min. The viable S. aureus cells were disrupted by the Cetyl trimethyl ammonium bromide (CTAB) to release intracellular ATP. Then, the ATP reacted with the firefly luciferase and D-Luciferin-based bioluminescence (BL) reagents solution to generate intensive BL signal. The CBD-magnetic separation-ATP bioluminescence (cMS-BL) assay was able to quickly detect viable S. aureus via ATP bioluminescence in 45 min, with a detection range from 5 × 103 to 5 × 107 CFU/mL and limit of detection (LOD) of 190 CFU/mL. Additionally, the cMS-BL method exhibited high specificity and anti-interference ability, which has been successfully applied to quantify S. aureus cells in crayfish-tail, chicken, and skim milk. Significance and noveltyThese results demonstrate the potential of CBD 163 as a versatile and robust biorecognition element for rapid and specific detection of viable S. aureus in food matrices. The proposed phage-derived bacteria-binding proteins-based protocol for BL detection shows various advantages, including high sensitivity, simple operation, and the capability to distinguish live bacteria, providing a strategy for designing high-quality biorecognition element toward foodborne pathogens.

A dual-mode aptasensor based on rolling circle amplification enriched G-quadruplex for highly sensitive IFN-γ detection

BackgroundAptasensors have been extensively utilized in target detection due to their advantages of high sensitivity and fast response. However, the reliability of the detection results of the single-mode aptasensor cannot be verified in time. Developing efficient detection methods with cross-validation capability is beneficial to achieving highly reliable detection. This study aims to design a colorimetric and fluorescent dual-mode aptasensor by skillfully engineering G-quadruplex assembly and rolling circle amplification for highly reliable IFN-γ detection. ResultsThe complexes of anti–IFN–γ aptamers and complement sequences (cDNA) were modified on the magnetic beads. In the presence of IFN-γ, the preferential combination of aptamers with IFN-γ resulted in the release of cDNAs. The cDNAs were collected by magnetic separation and then used as primers to trigger rolling circle amplification reaction to generate enriched G-quadruplexes. The G-quadruplex could be utilized to combine with hemin to catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine for colormetric mode or to couple with the fluorogenic dye Thioflavin T for fluorescent mode. The developed dual-mode aptasensor displayed a linear range of 1–10000 pM with a detection limit of 0.406 pM for the colormetric mode and a range of 0.1–10000 pM with a detection limit of 0.037 pM for the fluorescent mode. Further, the designed aptasensor was applied to IFN-γ detection in serum samples and achieved satisfactory recoveries. SignificanceThis innovative dual-mode detection strategy skillfully leverages the effective target-binding ability of aptamer, dual-function of the G-quadruplex and the signal amplifying ability of rolling circle amplification. This approach not only provides a reliable testing tool for the detection of IFN-γ, but also promotes the development of multimode sensing platforms.

Novel synthesis organic–inorganic heterojunctions of protonated g-C3N4/Fe3O4/AgBr/AgCl/AgI quinary magnetic photocatalyst with enhanced visible-light photocatalytic degradation of methylene blue in water

A novel magnetic quinary nanocomposite, protonated g-C3N4/Fe3O4/AgBr/AgCl/AgI, was synthesized using a wet chemical method. The multi-heterojunction photocatalyst with multi-carrier source and multi-channel carrier transport is constructed to enhance the photocatalytic degradation performance of pure g-C3N4. The design of the quinary nanocomposite is also an effective approach to solve the chemical stability problem of silver halides. The photocatalytic degradation efficiency under visible light irradiation was analyzed for methylene blue (MB) as the target organic pollutant. The quinary nanocomposite with 10 % g-C3N4 displayed high photocatalytic performance, with 83 % of MB degraded under 6 h LED white light irradiation. The effective quinary nanocomposite has good magnetic properties and can be magnetically separated to prevent secondary pollution of the photocatalyst in water. Parameters such as initial concentration of pollutant, initial solution pH, and light source were studied. Zeta potential results showed that the quinary nanocomposite could disperse homogenously to decrease aggregation in the solution. The photocatalytic degradation mechanism was investigated, and the mineralization results were analyzed based on liquid chromatography-mass spectroscopy (LC-MS) and total organic carbon (TOC). It was found that the hydroxyl and superoxide radicals were major reactive species by scavenging experiments. Additionally, protonated g-C3N4/Fe3O4/AgBr/AgCl/AgI nanocomposite showed excellent reusability after magnetic separation and regeneration, thus suggesting it to be a promising photocatalyst for treating wastewater containing organic contaminants.