Analytical Methods最新文献

A pyrene-incorporated BODIPY-based sensor (L1) was prepared as an efficient colorimetric and fluorometric chemodosimeter for detecting the cyanide anion in acetonitrile/HEPES buffer (5 mM, pH 7.2, 1 : 9 v/v) at room temperature. The probe L1 exhibited a distinct visual color change and selectively showed a fluorogenic "turn-off" response to cyanide ions in acetonitrile/HEPES buffer. Mechanistic investigations indicated that nucleophilic addition of cyanide at the α-position of the dicyanovinyl moiety inhibited the intramolecular charge transfer of L1 and induced significant shifts in absorption and emission. Various techniques, including optical spectroscopy, NMR titration, HRMS analysis, and theoretical simulations, were used to investigate L1's sensing mechanism. The presence of competing anions had minimal or no impact on this cyanide identification process. The probe achieved an outstanding detection limit of 4.33 × 10^-8 M. Furthermore, L1-impregnated filter paper strips enabled a visual, colorimetric, strip-based test that shifted from dark yellow to colorless upon exposure to cyanide. In addition, a smartphone-based technique was developed to capture the color shift, showing immense promise for cyanide detection without the need for sophisticated equipment. The formulation of L1 into an INHIBIT logic gate for facilitating cyanide identification using electronic devices is one of the significant applications. More significantly, L1 has been effectively used for fluorescence bioimaging in HeLa cells and for detecting cyanide anions in food samples, serving as an affordable and selective fluorescent sensor.

Tau protein is an important biomarker which is associated with neurodegenerative disorders, particularly Alzheimer's disease, where abnormal tau aggregation and hyperphosphorylation contribute to neuronal dysfunction and cognitive decline. The sensitive and early detection of tau protein is therefore crucial for the diagnosis, prognosis and therapeutic monitoring of neurodegenerative diseases. Owing to its clinical significance, the development of rapid, highly sensitive and reliable analytical platforms for tau detection has gained considerable attention in biomedical diagnostics. In this work, a Ru(II) based homogeneous sandwich ECL immunosensor was developed for the turn-on detection of tau. A polyclonal antibody was conjugated with Ru(II)@AuNP, which served as the ECL signal probe, and further integrated with monoclonal antibody conjugated L-Cys-CuNC to construct the ECL immunoassay system. Upon the addition of tau protein, the ECL intensity was enhanced due to the specific antigen-antibody interaction. The probe is selective and sensitive towards tau with a limit of detection of 0.23 pg mL^-1. Also, the probe is validated with spiked human serum samples with a recovery percentage of 90 to 104%.

Plastic-mulched soils contain mineral particles, organic matter and weathered polymer fragments that complicate the joint measurement of microplastics and co-occurring antibiotics. We developed a matrix-adaptive workflow combining sequential Fenton-enzymatic digestion, ZnCl₂/NaI cascade density separation, silver-membrane collection, µ-Raman chemical imaging and isotope-dilution LC-MS/MS. Performance was evaluated with four agricultural soils, four mulch-relevant polymers, two particle-size fractions, pristine and aged surfaces, and tetracycline, ciprofloxacin and sulfamethoxazole. Across 2304 independent particle-spike observations, mean microplastic recovery was 93.72 ± 3.17% (95% confidence interval, 93.59-93.85%), within-laboratory relative standard deviations were 2.5-3.4%, and Raman classification accuracy was 96.25%. Antibiotic recovery across 432 observations was 95.31 ± 3.61%; matrix effects ranged from -14.2 to 5.3%, while matrix-matched calibration gave R² values of 0.9995-0.9998. Pyrolysis GC-MS confirmed Raman-derived mass estimates (R² = 0.9897), with a mean inter-platform bias of 0.022 mg. Aging increased XPS O/C ratios, AFM roughness and BET area and nearly doubled Langmuir capacities; aged polyamide reached 32.66 mg g^-1 for tetracycline. In saturated columns, pristine polyethylene slightly advanced breakthrough, whereas aged polyethylene and polyamide shifted the 50% breakthrough point from 2.34 pore volumes without microplastics to 2.86 and 3.22 pore volumes, respectively. Factorial and mixed-effects analyses, multiplicity-controlled contrasts, grouped cross-validation and an uncertainty budget supported the method's cross-matrix robustness. The workflow provides a quantitative basis for linking analytical recovery, particle surface chemistry and contaminant migration in complex agricultural soils.

Trypsin (Try) is involved in various physiological processes in the human body, and its abnormal expression is associated with certain diseases. Therefore, its simple and accurate detection has important practical significance. Herein, a persistent luminescence sensing system is developed for autofluorescence-free detection of Try based on the blue emitting SiO₂/Sr₂MgSi₂O₇:Eu²⁺ (SSMSE) persistent luminescent nanospheres synthesized by the mSiO₂ template method and gold nanoparticle (AuNP) aggregation. Try can specifically hydrolyze peptides in the detection system to produce peptide fragments that can induce the aggregation of AuNPs, which weakens the quenching effect of AuNPs and leads to a decrease in the quenching degree of persistent luminescence of SSMSE, achieving Try detection. The proposed detection system demonstrates a good linear relationship within the range of 1-60 µg L^-1 with a low detection limit of 0.40 µg L^-1 and the ability to detect Try in actual samples with a recovery rate of 91.2%-106%. The developed method has expanded the use of SSMSE and provides new ideas for Try detection, which has certain practical value.

A green one-pot hydrothermal method produces amorphous carbon nanoflowers with a spiky structure and peroxidase-like activity. These nanozymes enhance luminol chemiluminescence 130-fold via generation of reactive oxygen species, which enables dopamine detection with a limit of 5.35 nM, demonstrating the promise of carbon nanozymes in chemiluminescence bioanalysis.

Rapid and sensitive detection of Staphylococcus aureus (S. aureus) is critical for food safety and public health. Herein, this work developed an ABC (aptamer-B-PER-CRISPR) cascade detection platform, where B-PER stands for bidirectional primer exchange reaction, that integrates aptamer-mediated target recognition, B-PER isothermal amplification, and CRISPR/Cas12a trans-cleavage for highly sensitive and specific detection of S. aureus. Upon target recognition, the trigger strand T is released from the aptamer-T duplex, initiating B-PER to generate abundant products containing sequences recognized by the guide RNA (gRNA), which activate Cas12a to cleave the reporter probe, generating a detectable fluorescence signal. Under optimized conditions, the platform exhibited a linear range of 10² to 10¹⁰ CFU per mL with a regression equation of F_{520 nm} = 575.36 log C + 3246.47 (R² = 0.9992) and a limit of detection of 13 CFU per mL. The assay showed excellent specificity for S. aureus, with negligible cross-reactivity toward Vibrio parahaemolyticus and Salmonella. Recovery tests in spiked milk samples yielded average recoveries of 98.9-100.7%. Overall, the ABC platform offers high sensitivity, excellent specificity, robust anti-interference capability, and operational simplicity, demonstrating great potential for rapid and reliable detection of foodborne pathogens in complex matrices.

Clock reactions, characterized by abrupt and time-controlled color transitions, are attractive platforms for analytical sensing, but methylene blue (MB)-based systems under acidic conditions typically rely on external reducing agents or nanostructured catalysts. Herein, we report a simple Cu(0) wire-catalyzed MB clock reaction that operates in acidic media (pH 2.0) without any added reducing agent or shape-controlled nanoparticles. The system exhibits reversible color transitions between MB and leuco-MB, governed by interfacial electron transfer and Cu redox cycling. Notably, at elevated MB concentrations (100 mg L^-1), repeated clock cycles lead to the gradual formation of a brown precipitate, which can compromise analytical performance. Mechanistic investigations (SEM, EDS, and XPS) reveal that the precipitate originates from interactions among Cu species (Cu⁰/Cu⁺/Cu²⁺), Cl^-, and MB, with partial incorporation of MB into CuCl-based solids during redox cycling. Strategies including acid cleaning of the Cu wire and lowering MB concentration effectively suppress precipitate formation and improve system stability. Under optimized conditions, the clock reaction enables quantitative detection of Cr³⁺via modulation of reaction kinetics, affording a linear response with a limit of detection of 3.22 µmol L^-1. The method also demonstrates excellent selectivity and robustness in real water samples. This work establishes a reducing-agent-free MB clock platform and provides new insights into Cu-mediated interfacial redox processes, offering a simple, cost-effective, and practical strategy for metal ion sensing.

This work focuses on the development of a portable ratiometric luminescent sensor device for the detection of picric acid (PA) in aqueous medium. The present study involves the fabrication of a europium MOF-PMMA polymer film into a 3D-printed device, engineered for red fluorescence emission. The probe (Eu-MOF/PMMA film) was thoroughly characterized using various spectroscopic and microscopic techniques, including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). The development of an analytical probe to monitor picric acid (PA), a highly mutagenic substance, is of enormous significance for the environment and health. The probe we developed exhibited strong red fluorescence at an excitation wavelength of 294 nm, which was selectively and sensitively quenched by picric acid. Additionally, the Eu-MOF/PMMA fluorescent strip exhibits a hypsochromic shift from red to green upon the addition of picric acid, making it a ratiometric fluorescent sensor for picric acid. The integration of smartphone-based Red-Green-Blue (RGB) analysis enables fast, portable, real-time detection of PA in real samples by quantifying color intensity variations. The PMMA matrix was deliberately chosen for the composite fabrication due to its excellent UV stability and ability to preserve optical transparency under UV irradiation, and the resulting luminescent detection device was found to be reusable, underscoring its potential as a portable, recyclable, and practically viable sensing platform. The device is easy to fabricate and cost-effective for the detection of picric acid in aqueous media, with a detection limit of 31.16 pM.

To ensure the stability and efficacy of recombinant collagen during development, storage, and application, it is essential to establish systematic and reliable stability assessment methodologies. This study developed and validated an integrated multi-technique analytical strategy for the comprehensive evaluation of the thermal stability of recombinant humanized type III collagen (rhCol III). The strategy combines size exclusion chromatography-multi-angle light scattering (SEC-MALS), dynamic light scattering (DLS), circular dichroism spectroscopy (CD), SDS-PAGE, and µLC-MS/MS to perform correlative analyses of physical aggregation, secondary structure, chemical modifications, and biological functions in samples stored under accelerated degradation conditions (40 °C) and control conditions (4 °C) for three months. The results demonstrate that the established strategy can systematically differentiate and quantify degradation pathways under different temperature conditions. SEC-MALS, SDS-PAGE and DLS revealed that high-temperature storage significantly increased the formation of large aggregates (>100 nm), while circular dichroism spectroscopy confirmed that the secondary structure remained largely intact. The core of the strategy, µLC-MS/MS-based post-translational modification (PTM) analysis, quantitatively elucidated key chemical modifications: oxidation (up to 16.86%) and deamidation (up to 12.31%) levels were markedly elevated, whereas proline-4-hydroxylation, essential for structural stability, was substantially reduced (<6%). Key modification sites (e.g., N425, M131, and P144/P132) were successfully localized and found to be enriched in thermally sensitive regions N- and C-termini. This chemical modification profile was highly consistent with functional assay results: samples stored at 4 °C exhibited significantly superior promotion of cell adhesion (+42% vs. +21%) and migration (45.28% vs. 42.05%) compared to those stored at 40 °C. Moreover, the study found that a higher moisture content in the lyophilized samples not only significantly reduced aggregate formation but also affected the levels of PTMs. The analytical strategy developed in this study enables multidimensional and correlative assessment of protein stability. It not only provides a key stability-indicating methodology for rhCol III but also offers an analytical reference framework for stability studies, process optimization, and quality control of biomacromolecular materials.

Quantifying trace heavy metals in complex food and environmental matrices requires sorbents with exceptional selectivity and matrix tolerance. We synthesized a ternary hybrid matrix (nano-HAP@Tween80@SG) via an ultrasound-assisted secondary coating approach, configuring it for the solid-phase extraction (SPE) of Cu(II) and Mn(II) prior to flame atomic absorption spectrometry (FAAS). Structural analyses (TEM, SEM-EDS, XRD, BET, FT-IR) confirmed the formation of a hierarchical assembly with extended mesoporosity. At an optimal pH of 5.0, metal adsorption followed the Langmuir and Freundlich models. The underlying sequestration mechanism is driven by a complex interplay of physical and chemical interactions: multi-dentate surface complexation and electrostatic attraction operate concurrently with the intrinsic thermodynamic ion-exchange capacity of the hydroxyapatite lattice, while the mesoporous network provides critical spatial confinement. Analytical performance proved highly competitive. Limits of detection were 0.022 µg L^-1 for Cu(II) and 0.024 µg L^-1 for Mn(II). The enrichment factors were 30 for Cu(II) and 29 for Mn(II), with relative standard deviations all below 3.0%. Method accuracy was validated against certified reference materials (wheat, rice) and actual environmental water samples, yielding recoveries between 95.50% and 103.33%. The nano-HAP@Tween80@SG-SPE-FAAS system functions as a practical, cost-effective platform for routine trace metal surveillance.