Microchimica Acta最新文献

A label-free electrochemical biosensor is presented for the detection of miRNA-223, a host immune-derived biomarker upregulated in early mastitis. The biosensor consists of porous anodic alumina (pAAO) membranes featuring high-aspect-ratio porous structure, functionalized with ssDNA probes. This nanochannel-based design increases surface area for probe immobilization and enhances sensitivity by amplifying hybridization-induced changes in ionic transport.

Upon hybridization with miRNA-223 to the immobilized ssDNA probe, partial pore blockage impedes the diffusion of a redox probe added to the measuring solution. This change in diffusion is quantified via square wave voltammetry. The biosensor enables direct miRNA detection in raw milk, eliminating the need for RNA extraction or amplification.

The biosensor was systematically optimized for pore diameter, probe concentration, and blocking conditions, and demonstrated consistent signal suppression in the presence of synthetic miRNA-223 across a dynamic range from 0.1 pM to 1 nM in both phosphate buffer and 0.1% raw milk. Application to milk collected from clinically classified cows showed clear discrimination between healthy and subclinical samples, with an area under the receiver operating characteristic curve of 0.96. Statistical analysis across 30 replicate sensor readings confirmed significant group-level discrimination (p = 0.016, Mann–Whitney U test). The biosensor’s high sensitivity and specificity are attributed to its diffusion-limited pore-based architecture and stable surface functionalization, which together enable selective and reproducible hybridization responses. Its demonstrated compatibility with raw milk furthers its robustness and analytical reliability under real sample conditions. The ability to detect early-stage, immune-derived miRNAs in minimally processed milk (0.1% v/v raw milk in phosphate buffer) supports the deployment of this biosensor in on-farm, real-time surveillance systems. By eliminating reliance on pathogen detection and enabling pre-symptomatic classification, this work aims to contribute to improved livestock health management, antimicrobial stewardship, and broader one-health objectives.

Extracellular vesicles (EVs) are central mediators of intercellular communication and disease progression, with important implications for diagnostics and therapeutics. EV concentration often increases in disease, making it not only a measure of experimental reliability and reproducibility but also a potential biomarker. Conventional techniques such as nanoparticle tracking analysis (NTA) and tunable resistive pulse sensing (TRPS) are widely used but are time-consuming, require specialized equipment, and are limited by EV heterogeneity. Thus, a faster, more scalable, and cost-effective method for EV quantification is needed. In this study, we developed an Extracellular Vesicle-Induced Silver-nanoparticle Aggregation (EVISA) assay for rapid and accessible measurement of EV concentration based on plasmonic nanoparticle aggregation with visible colour change. We screened multiple nanoparticles for aggregation upon mixing with EVs, assessed by naked-eye colour change and quantified with a standard ELISA plate reader. Transmission electron microscopy (TEM) confirmed nanoparticle aggregation, and zeta potential analysis demonstrated that EV-induced aggregation arose from destabilization of colloidal stability. Silver nanoparticles exhibited EV-induced plasmon coupling, evidenced by localized surface plasmon resonance (LSPR) shifts, resulting in increased absorbance at 450 nm as detected by the plate reader. Together, these findings establish EVISA as a rapid, cost-effective, and scalable EV quantification platform that leverages widely available biological laboratory instrumentation, enabling broader adoption across the EV research community.

Gold nanoclusters (AuNCs), ultrasmall aggregates of gold atoms with unique molecular-like electronic structures and excellent photoluminescent properties, have emerged as promising candidates for fluorescence-based bioanalytical applications. However, the fluorescence intensity of AuNCs is relatively low, which significantly restricts their practical applications in high sensitivity fluorescence detection and imaging. This study successfully designed a fluorescent probe by encapsulating AuNCs in zinc-glutamate metal organic frameworks (ZG-MOF). Notably, the fluorescence intensity of the encapsulated AuNCs was significantly enhanced by nearly one-third owing to the confined pore size of ZG-MOF. This probe exhibits high specificity for ferric ions recognition with a rapid response. Furthermore, it shows an excellent linear correlation with ferric ions concentrations in the range 5.0–1000.0 µM. Moreover, the probe has been successfully applied to real-time fluorescence imaging of ferric ions in zebrafish embryos, and can monitor ferroptosis in zebrafish embryos induced by exogenous agents, achieving in vivo visualization of ferric ions distribution.

A disposable electrochemical sensor based on a competitive surface-blocking mechanism driven by covalent epoxide–amine coupling is reported for the selective voltammetric determination of fosfomycin (Fos). The sensing strategy employs ferrocen (Fc)-tagged surface chemistry as a redox reporter, where Fc surface occupancy inversely reflects Fos binding to cysteamine-derived amine groups. Screen-printed carbon electrodes (SPCEs) modified with a reduced graphene oxide/gold nanoparticle (rGO/AuNP) nanocomposite provide enhanced electroactive surface area and improved electron-transfer kinetics. Increasing Fos concentrations progressively consume surface amines, reducing Fc labeling and leading to a concentration-dependent decrease of the differential pulse voltammetric oxidation signal. Under optimized conditions, the sensor exhibits a linear response from 50 to 2000 µM with a limit of detection of 10 µM, matching the clinically relevant mid-therapeutic range of intravenous fosfomycin therapy (≈ 7–276 mg L⁻¹). Matrix effects are effectively minimized by controlled serum dilution, enabling accurate Fos quantification with recoveries of 97.8–103.7% and without extensive sample pretreatment. The platform retains stable performance for at least 15 days at 4 °C. Rather than replacing chromatographic techniques, this proof-of-concept platform is positioned as a rapid, low-cost, and portable electrochemical tool for routine therapeutic drug monitoring and point-of-care screening.

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A novel photoelectrochemical (PEC) aptasensor based on high-entropy sulfide (CdZnMnCrCo)_xS for ultrasensitive ampicillin (AMP) detection has been developed. The sulfide, synthesized by a simple one-pot solvothermal method, featured abundant heterointerfaces and rich grain boundaries, which enhanced charge separation/transport, amplifying the PEC signals. Integrated with methylene blue (MB, as a photosensitizer) and exonuclease Exo-1-mediated recycling, the sensor achieved a broad linear range (0.1–1×10⁶ pg mL^-1) and a low detection limit (0.09 pg mL^-1) with strong anti-interference characteristic. Spike-recovery tests on actual water samples at 10 and 50 pg mL^-1 produced excellent recoveries of 97.4–103.8%. This work highlights the high-entropy sulfide’s potential as versatile sensing platforms for advancing PEC-based environmental monitoring. Future research will integrate multiplexed aptamer arrays with flexible printable electrodes for on-site detection in medical wastewater.

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A platform is presented based on electrosynthesis of pyramidal Cu nanoparticles (p-CuNPs), in a three-dimensional structure on an indium tin oxide (ITO) electrode. The electrochemical sensing utility of this structure was evaluated for detection of methadone. A key advantage of current approach is the ultra-fast synthesis of the p-CuNPs on the ITO, which is accomplished in only 120 s. The SEM images showed that the p-CuNPs were arranged in cubic blocks to form 3D Cu pyramids on the ITO electrode substrate named p-CuNPs/ITO electrode. In optimal condition, the p-CuNPs expose a wider area, effective mass transport, and more electroactive sites for the interaction of the target analyte that improved the current signals: a ~ 6072-fold increase compared to bare ITO and a 3.3-fold enhancement over a metallic Cu plate. It was observed that the p-CuNPs/ITO sensor platforms exhibit a linear response over a concentration range from 0.005 to 120 μM methadone, with a detection limit of 1.4 nM. The sensor selectivity was investigated across a wide range of drugs and biological compounds, and the sensor showed high selectivity for detecting methadone. The detection of methadone in urine and blood samples with excellent recoveries confirms exceptional response of the sensor in biological assays.

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A fast fluorescent dual-emission platform for sensitive detection of sodium dehydroacetate (SDHA) in food is established utilizing bimetallic organic frameworks (Eu@Zr-MOFs). Eu@Zr-MOFs show two fluorescent emissions at 430 nm and 616 nm under single excitation wavelength of 290 nm. Two peaks separated by 180 nm help to eliminate environmental interference and improve the accuracy. In the presence of SDHA, fluorescent intensity at 430 nm and 616 nm shows fluorescent quenching within 1 min. Fluorescent lifetime results show that fluorescent quenching is a static quenching mode. Fluorescent quenching may be ascribed to the diketone structure of SDHA coordinated with Eu³⁺ and internal filtering effect. The logarithm of fluorescent intensity (lgI_{430 nm} * I_{616 nm}) has linear relationship with the concentration of SDHA from 0.1 µM to 200 µM with a limit of detection of 31.6 nM. More conveniently, it also achieves visual detection of SDHA through fluorescent color by portable UV lamp and smartphone “color capture” mode. The platform is applied to detect SDHA in fermented and baked food samples. Thus it is an efficient and sensitive fluorescent ratio method for SDHA detection with fast response, high selectivity and accuracy. 

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The development of a novel, highly sensitive electrochemical sensor for ASP based on an alizarin red S-functionalized zeolitic imidazolate framework-8 (ALZ@ZIF-8) nanocomposite. The nanocomposite was synthesized via a one-pot approach and fabricated on a carbon paste electrode (ALZ@ZIF-8/CPE). Its interaction with ASP was elucidated through density functional theory (DFT) calculations and electrochemical analysis, while its structure was confirmed using SEM, XRD, FT-IR, UV-Vis, and spectrofluorimetric techniques. Under optimized conditions, a square-wave voltammetric (SWV) method was developed and rigorously validated. The sensor demonstrated a wide linear range from 0.01 to 14.0 µM, with exceptional sub-micromolar sensitivity (detection limit: 3.45 nM; quantification limit: 10.46 nM). The method showed high accuracy (recoveries: 99.26–101.62%) and precision (relative standard deviation, RSD ≤ 1.01%). Successful application to spiked human plasma yielded recoveries ≥ 98.84% with RSDs ≤ 1.61%, confirming practical utility. This work presents the first application of the ALZ@ZIF-8 nanocomposite in analysis. The proposed sensor offers a promising and adaptable platform for the sensitive detection of ASP and other target molecules in complex biological media.

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A copper and nitrogen co-doped carbon dots (Cu, N-CDs)-based fluorescent sensor is developed for thiram detection. In detail, with increasing thiram concentration the fluorescence intensity of Cu, N-CDs at 405 nm decreases , while that at 495 nm remains largely unchanged. This phenomenon results from the Cu-induced complex formation, which increases the aggregation of Cu, N-CDs and triggers fluorescence resonance energy transfer. Based on these findings, a good linear correlation is observed ranging from 0 to 100 µM (R² = 0.99489) thiram under the optimized conditions, with a calculated detection limit (LOD) of 38.7 nM. Moreover, a smartphone-integrated optical sensing platform is developed to enable on-site thiram detection, achieving a LOD of 110.8 nM. Furthermore, this platform has been successfully applied to real samples and shows satisfactory relative recoveries for thiram (96.20%-103.40%) with relative standard deviations ranging from 1.47% to 2.54%. Therefore, this novel Cu, N-CDs based platform provides a helpful strategy for detecting thiram residues in the environment.

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Regarding the importance of early diagnosis of ovarian cancer and its progression monitoring, an ultrasensitive sandwich-type electrochemical immunosensor was developed to detect cancer antigen 125 (CA 125) biomarker. A hybrid nanocomposite was synthesized by integrating COOH-functionalized multi-walled carbon nanotubes (MWCNT-COOH) with a trimetallic NiYFe layered double hydroxide (NiYFe-LDH). To further improve the electrochemical activity, gold nanoparticles (AuNPs) were deposited onto the resulting nanohybrid structure. The final Au@LDH/MWCNT nanocomposite was characterized using standard methods and subsequently employed to modify screen-printed carbon electrodes (SPCEs) for capturing the sandwich structure of the immunosensor. The high specific surface area and biocompatibility of the nanocomposite provided an appropriate microenvironment for the effective capture of primary antibodies (Ab1) and preserving the integrity of the sandwich structure during signal analysis. The output response of the immunosensor was measured utilizing differential pulse voltammetry (DPV), revealing a wide linear range of 0.1 U mL^− 1 to 600 U mL^− 1 and a low detection limit of 0.0013 U mL^− 1. The immunosensor demonstrated excellent selectivity, stability, and reproducibility. Furthermore, its reliable performance for the clinical applications was confirmed by evaluating recoveries using the standard addition and the standard enzyme-linked immunosorbent assay (ELISA) methods. Additionally, the results exhibited that the proposed platform can be further developed for the detection of other cancer-related biomarkers.

Graphical Abstract

Illustration of the Au@NiYFe-LDH/MWCNT-based SPCE immunosensor for CA 125 detection. The proposed nanocomposite can effectively provide a large and functional surface for antibody immobilization and subsequent sandwich immunoassay formation, which results in sensitive antigen detection while maintaining compatibility with protein structure. A wide linear range and low detection limit obtained in DPV responses demonstrate a promising potential for timely diagnosis and intervention.