Analysis & sensing最新文献

The construction of fluorescence sensor L1 for cyanazine (CNZ) by using calix[4]arene scaffold allied with 9-Aminoacridine moiety has been reported. The recognized triazine herbicide CNZ decreased the fluorescence intensity of L1 by exhibiting “turn-off” phenomenon having detection limit to be 7.79 μM obtained from emission study. The quenching response of L1: CNZ was observed between the range of 5–105 μM possessing binding constant calculated to be 9.201×10⁶ M⁻¹. The spiking experiment of CNZ into L1 has also been performed to evaluate potency of L1 using vegetables and cereals. Also, a paper-based device has been prepared in order to implement this strategy for on-spot monitoring of CNZ. The L1:CNZ binding has been confirmed by conducting electrochemical studies like cyclic voltammetry, differential pulse voltammetry, ¹H NMR, FT-IR, MALDI-TOF, ¹H NMR titration, PXRD investigation and computational analysis.

Kanamycin A is a widely used antibiotic, although it has a narrow therapeutic window demanding highly accurate monitoring. The sensing of kanamycin A using aptamers is of great interest since aptamers can be used for continuous monitoring with a rapid response. While kanamycin has been the target for at least four previous aptamer selections, the binding affinities of the reported DNA aptamers are still sub-optimal. All the previous aptamer selections were performed at pH 7.5 or higher. Given that kanamycin A has four amino groups with pK_a values close to 7, we herein selected DNA aptamers for kanamycin A at both pH 6 and pH 8. The selection at pH 6 enriched aptamers although the pH 8 selection library remained highly diverse in the end. The best aptamer named KAN6-1 showed a dissociation constant of around 320 nM measured using isothermal titration calorimetry in the selection buffer. In buffers without salt, binding can happen from pH 6 to 8. Specific binding was confirmed using mutation studies. A strand displacement assay was developed with a limit of detection (LOD) of 100 nM in buffer. Similar LOD values were also obtained in lake water and in 10 % human serum. Comparisons were also made with some previously reported DNA aptamers. This study shows the importance of pH value on the selection of aptamers and provides a new aptamer for kanamycin A detection.

Nano biosensors based on MXenes have been emerging as a promising tool in the detection of biomarkers, for the discrimination of diseases and in the detection of environmental pollutants. Their potential in sensing applications has also drawn a lot of attention to their unique qualities such as their high conductivity, huge surface area, outstanding hydrophilicity, biocompatibility, and simplicity of surface functionalization. The development of scalable synthesis techniques is essential to the large-scale manufacturing and broad application of MXene-based sensors. Furthermore, the stability of the MXene layers in diverse environmental circumstances continues to be a difficulty for their practical application. To increase the dependability and precision of MXene-based sensors, their selectivity must be increased through functionalization and tuning. With innovative technologies like machine learning, MXene biosensor is now taken advantage of new opportunities. Personalized healthcare solutions, remote data analysis, and real-time monitoring are all possible when MXene sensors and AI algorithms work together. Herein, the optical properties, synthesis approaches, role of MXene biosensors in machine learning, its significant challenges and future prospects of MXene-based nano(bio)sensors are deliberated.

In this study, a solvothermal method was used to synthesize a composite of iron oxide nanostructures on carbon nanotubes (CNTs), which was applied as a resistive sensor for hydrogen gas (H2) detection. The nanocomposite was produced with three different iron oxide concentrations (Fe1@CNT, Fe2@CNT, and Fe3@CNT) to investigate the effect of iron species on CNTs and their interaction with hydrogen. Electron microscopy revealed that increasing iron oxide content led to the deterioration of the CNT walls. Raman and FTIR spectra confirmed the predominant presence of α-Fe2O3 (hematite) on the CNTs, while XPS analysis verified the presence of multiple iron oxides species. High-resolution XPS of the Fe 2p region indicated the existence of Fe3O4 (magnetite), Fe2O3 (hematite), and FeO (iron(II) oxide) associated with the CNTs. The sample with the lowest iron oxide concentration (Fe1@CNT) showed a 45 % sensor response to hydrogen in a dry air atmosphere and the longest recovery time, suggesting a stronger interaction between hydrogen and the nanocomposite. Density functional theory calculations further revealed that the presence of iron oxide on the CNT surface significantly altered its electronic properties, particularly by introducing more electronic states near the Fermi level, which enhanced electronic exchange between H2 and the carbon nanotube containing iron oxide.

This review gives an overview of using microfluidics in conjunction with molecularly imprinted polymers (MIP), which covers two aspects: on the one hand, on-chip synthesis of polymer and MIP particles on the nano and the micro scale. This comprises both approaches using two different immiscible solvents and homogeneous matrices to obtain the desired particle morphologies. On the other hand, especially paper-based microfluidic systems have attracted increasing interest as low-cost analytical tools that are inherently useful for applying at the point of care. By now, there have been several successful attempts to combine them with MIP (instead of biological recognition systems) and to successfully apply them in environmental samples, food matrices, and for diagnostic applications.

Metabolic MRI is a powerful new molecular imaging modality, and parahydrogen-based SABRE technology presents a promising approach to hyperpolarize metabolites with high throughput, low cost, and minimal methodological and instrumental burden. In the Concept Article by Andreas B. Schmidt, Stephan Knecht, and co-workers key advances are reviewed that have recently enabled the first in vivo metabolic imaging with hyperpolarized pyruvate using SABRE.

Given high levels of both K⁺ and H⁺ in the tumor microenvironment, G-quadruplex (G4) and i-motif can in principle be utilized as two cooperative modules to build logic-gated DNA nanodevices for microenvironment recognition and targeting. Combined use of G4 and i-motif in DNA nanoassemblies, however, usually causes the uncontrolled DNA aggregation. To address this trouble, we well design a novel i-motif/G-quadruplex (iG4) hybrid structure that integrates two four-stranded DNA helices in a folding topology, with a parallel mini-duplex flanking at the 5’ end to provide a binding site for fluorescent ligands. This design enables that the folded and lighting-up DNA structure is favored by H⁺ and K⁺ together, consistent with a two-input AND gate behavior. We then employ the iG4 structure to guide a DNA nanotweezer that is clamped by an altered split ATP aptamer, which brings a proximity effect contributing to the proper folding of iG4 in slightly acidic microenvironments and enables the sensitive detection of endogenous ATP in cancer cell lysates.

Single domain antibodies (sdAbs) provide versatile binding reagents that offer advantages over conventional antibodies for use in immunoassays. SdAbs consist of the ~15 kDa variable heavy domain from the heavy chain-only antibodies found in camelids and can be engineered for integration in a variety of immunoassay formats. The Luminex MAGPIX instrument is a high-throughput platform that uses color-coded MagPlex beads to enable multiplexed immunoassays and is relatively fast and simple. We developed a MagPlex bead-based assay for the detection of influenza A virus (IAV), using sdAbs against IAV nucleoprotein (NP). To provide sensitive detection, the sdAbs were formatted into bivalent constructs; and the capture reagent was tailored to provide oriented immobilization on the bead. Using the best capture and reporter pair, we achieved detection of recombinant NP down to 1 ng/mL. Finally, we demonstrated that the developed immunoassay showed promise in detecting IAV in clinical samples.

An electrochemical sensing platform for the detection of paracetamol is proposed in this work. The sensor (Asp-MWCNTs/IL/ITO) is based on Indium Tin Oxide (ITO) electrode loaded with asparagine functionalised Multi Walled Carbon Nanotubes (MWCNTs) and Ionic Liquid (IL). Initially, in-silico studies were performed to check the favourable interaction of the drug with the nanocomposite. The potential energy surface of Asp-MWCNTs and paracetamol complexes were explored using density functional theory and single-point energy coupled cluster calculations. The analysis of non-covalent interactions showed hydrogen bonding interactions predominantly stabilising the complex. The interaction process between Asp-MWCNTs and paracetamol is spontaneous due to negative value of binding energy (−0.75 eV). The functionalised MWCNTs were characterised through different techniques. Asp-MWCNTs/IL/ITO electrode showed good sensitivity with a linear range from 20–300 μgL⁻¹ and limit of detection of 0.0194 μM for paracetamol in phosphate buffer as supporting electrolyte. The sensor showed excellent repeatability and reproducibility with a relative standard deviation of 1.45 % at 60 μgL⁻¹ concentration. The chemical functionalization resulted in providing extra stability as it retained 95 % of its signal response even after 45 days. The sensor's applicability was tested in real water samples with the help of spiking study which showed good recovery >95 %.”

Despite the soaring popularity of e-cigarettes among teenagers and young adults, our understanding of the full extent of their health hazards have remained limited. This is due to the vast complexities of e-cigarette aerosols and the difficulty in their full characterisation. Conventional mass spectrometry methods of e-cigarette analysis, though pioneering in driving political and medical discourse, have been limited in their capabilities to uncover all compounds in its emissions due to prominent limitations in experimental setup. To overcome this major hurdle, we have developed a setup for puff-by-puff analysis of electronic and conventional cigarette emissions by concentric dielectric barrier discharge ionisation mass spectrometry. In this pilot study, the simple setup of in-line dilution and high-resolution mass spectrometry analysis allowed us to directly uncover 225 compounds in e-cigarette puffs across a wide spectrum of chemical classes in two sequential 5-minute runs. These include acids, carbonyls, aromatic cyclics, heterocyclics, unsaturated and saturated hydrocarbons, alcohols, esters, alkaloids, sulfur-containing compounds, oxides, and nitriles. As a result, our setup provided a significant improvement in rapid compound identification, and demonstrated a much broader chemical landscape in e-cigarette emissions than previously reported.