化学最新文献

The accurate monitoring of the fruit ripening is crucial for maintaining quality and prevention from post-harvest economic losses. Goldenberry, being rich in vitamins, minerals, and carotenoids, yet its ripening assessment relies on variable and often subjective traditional approaches. To address this, the present study utilises rapid and non-destructive techniques using confocal micro-Raman and UV-Vis spectroscopy to track biochemical changes in both the exocarp and mesocarp of goldenberry fruit across five ripening stages: pre-mature, mature, pre-ripe, ripe, and post-ripe. The analysis of Raman spectra of exocarp shows an increase in carotenoid bands up to ripe stage, followed by a decrease at post-ripe stage, while the mesocarp exhibits a continuous increase in carotenoid intensity through stage post-ripe. The UV-Vis spectral analysis supports these observations, indicating increasing carotenoid content alongside a reduction in chlorophyll as ripening progresses. Among different machine learning (ML) approaches, unsupervised clustering demonstrates strong performance of k-means and agglomerative nesting, with high rand index values (>0.97). In supervised domain, support vector machine, logistic regression, random forest, decision tree, and principal component-linear discriminant analysis achieves the highest values of performance metrices including accuracy, precision, recall, F1 score, ROC/AUC values, and cross validation scores. Moreover, partial least squares regression analysis demonstrates excellent predictive power, with R² = 0.93 (calibration) and 0.70 (cross-validation) for exocarp and R² = 0.91 (calibration) and 0.89 (cross-validation) for mesocarp. The combined use of Raman with ML enables a practical and reliable framework for assessing fruit ripening, with promising applications in quality control and post-harvest management.

17α-Ethinylestradiol (EE2) is a phenolic estrogenic endocrine disruptor widely distributed in aquatic environments; therefore, sensitive and reliable analytical methods for its environmental monitoring are required. Herein, an adsorption-regulated electrochemical sensing strategy is proposed for the quantitative determination of EE2 using a Cu@Fe₂O₃ composite-modified glassy carbon electrode. The synergistic Cu-Fe₂O₃ interface effectively enhances interfacial affinity toward EE2 molecules and facilitates proton-coupled electron transfer during electrochemical oxidation, resulting in an analytical signal predominantly governed by interfacial adsorption rather than diffusion. Under optimized conditions, the modified electrode exhibits a good linear response to EE2 in the concentration range of 0.10 -20.00 μM with a detection limit of 0.033 μM. Electrochemical mechanism studies indicate that the oxidation of EE2 is an irreversible, adsorption-controlled process. The proposed sensor shows satisfactory selectivity, good repeatability, and long-term stability. Moreover, it was successfully applied to the determination of EE2 in real water samples with acceptable recovery values. This study highlights the crucial role of interfacial adsorption in electrochemical signal amplification and provides a versatile analytical strategy for the sensitive detection of phenolic endocrine-disrupting compounds in complex water matrices.

Silicate is an essential nutrient in marine ecosystems, exhibiting a dynamic concentration due to complex biogeochemical processes. Accurate and high-frequency monitoring of silicate in marine environments is therefore highly desirable. In this study, a fully automated electrochemical system was developed for online determination of silicate in natural seawater and in diatom incubation experiments. This system integrates flow injection analysis with thin-layer electrochemistry (TLE), using square wave voltammetry (SWV) for silicate measurement. The optimized system achieved a low detection limit of 0.4 μM and demonstrated excellent long-term stability, with a relative standard deviation (RSD) of 7.4% over 90 days of operation. The method was validated using coastal seawater collected from 10 sites spanning a range of salinities, showing good agreement with a reference spectrophotometric method. Moreover, continuous monitoring over 7 days in a Phaeodactylum tricornutum culture captured significant changes in the silicate concentration during its growth cycle. Overall, the system provides sensitive, long-term online monitoring of silicate in laboratory-controlled seawater systems and provides a technical basis for future field-deployable applications.

In this work, a molecularly imprinted electrochemical aptamer sensor (MIEAS) for the detection of enrofloxacin (ENR) was developed using SnO₂-graphene (SnO₂-Gr) and gold nanoparticles (AuNPs) as electrode modification materials. The SnO₂-Gr composite material has a large specific surface area and can enhance the conductivity of the sensing platform. The aptamer, serving as a biofunctional monomer, was immobilized on the electrode surface via Au-S bonds. Using ENR as the template molecule and nicotinamide (NA) as the chemical functional monomer, a molecularly imprinted polymer (MIP) film was prepared by electropolymerization. Benefiting from the synergistic effect of MIP and aptamer, this MIEAS exhibits a good linear relationship with ENR in the range of 10^-14 to 10^-5 M, and the detection limit is as low as 1.65 × 10^-15 M. Satisfactory recovery was obtained in milk and environmental water samples, indicating the potential for application in food and environmental analysis.

The presence of malathion (Mal) residues in food and water environment have garnered widespread public concern. Here, we developed PCN-224-supported Pt nanozymes through an in-situ reduction method, where the porous porphyrin framework and Pt sites jointly promote electron transfer and provide more active centers, leading to drastically enhanced oxidase (OXD)-mimicking activity. The obtained PCN-224@Pt can directly oxidize colorless TMB to blue oxTMB without H₂O₂, while the specific adsorption of Mal on the nanozyme surface will shield active sites and inhibit the catalytic reaction. Accordingly, a colorimetric sensor was then established to achieve sensitive determination of Mal in a linear detection range from 0.01 to 2.5 μg/mL with a low detection limit (LOD) of 6.62 ng/mL. Moreover, this platform displayed high selectivity and stability in food and water samples, with satisfactory recoveries of 90.1 %-107.7 % (RSDs < 9.31 %). This strategy provides a new attempt to construct nanozyme probes for direct detection of Mal, suitable for visual analysis in food and water environments.

The development of predictable and thermodynamically stable DNA nanomachines remains challenging for the monitoring of intracellular microRNAs (miRNAs) in complex biological matrices. In this study, a fluorescent biosensor utilizing a confined-free synergistic configuration is presented for the precise detection of miR-21. To mitigate the thermodynamic limitations of homogeneous catalytic hairpin assembly (CHA), a process in which unconstrained molecular diffusion induces background leakage, the amplification components were spatially partitioned. The sensing platform incorporates a rigid DNA nanosphere (NP), assembled via the annealing of three palindromic sequences, which serves as a sterically hindered scaffold to strictly confine hairpin probe 1 (HP1). Target miR-21 initiates the opening of the anchored HP1, subsequently recruiting freely diffusible auxiliary probes (HP2 and HP3) to form a localized Y-shaped complex. This reaction generates a surrogate miR-21 sequence that detaches and unlocks adjacent HP1 probes, establishing an inter-particle chemical communication network. By integrating nanoscale spatial confinement with this propagated catalytic cascade, the proposed confined-free self-circulating amplifier (CF-SCA) suppresses background leakage while maintaining rapid mass transfer, yielding a limit of detection of 100 pM. Additionally, the dense 3D nanoscaffold provides nuclease resistance. Following liposome-mediated cellular delivery, the confined-free mechanism counteracts macromolecular crowding, facilitating in situ dynamic imaging of miR-21 in living cancer cells. Evaluated through the stratification of clinical serum samples from multiple cancer cohorts, the CF-SCA nanoplatform offers an enzyme-free tool for clinical diagnostics and liquid biopsy applications.

Breast cancer is one of the most prevalent cancers worldwide and a leading cause of cancer-related mortality. However, early detection of the disease can significantly reduce the mortality rate of cancer patients. The current detection methods of breast cancer are expensive, time consuming, invasive and require professional assistance. To overcome these challenges, a minimally invasive low-cost paper-based point-of-care (POC) electrochemical sensing platform has been developed for early-stage detection of breast cancer. The proposed sensor is fabricated using a screen-printing technique, incorporating two-dimensional Ti₃C₂ (MXene) nanosheets onto the working electrode. These nanosheets provide enhanced electrochemical performance, enabling an exceptionally low limit of detection (LOD) ∼ 4 cells mL^-1) attributed to their high conductivity and large surface area. The electrode surface is further functionalized with specific aptamers, facilitating selective target recognition. The proof-of-concept study was validated using multiple cell lines, including A549 (lung cancer cells), NIH3T3 (fibroblast), and HEK293 (kidney cells), and MDA-MB-231(breast cancer cell line), to evaluate the specificity of the developed aptasensor. The sensing mechanism relies on the selective binding of aptamers to Mammaglobin A proteins expressed on circulating tumor cells (CTCs). This interaction induces conformational changes in the aptamer, resulting in measurable alterations in the electrochemical properties at the electrode interface. The conjugation of the biomarker with the aptamer upon aptamer-protein interaction, results in a change in current, which is sensed by cyclic voltammogram (CV). The resulting signal is used to plot a calibration curve for quantitative analysis. Further, these sensing experiments are validated using in vitro experiments with human blood serum as a proof of concept. Overall, the developed paper-based electrochemical POC device offers significant advantages, including affordability, ease of use, rapid response, and quantitative detection capability.

Kanamycin (Kana) residues released into aquatic environments due to its extensive use have raised increasing concerns because of their potential risks to ecosystems and human health. In this work, we report a label-free split aptamer-modified gold nanoflower (AuNF)-based aptasensing platform with colorimetric and electrochemical readouts for the determination of Kana in water. Two thiolated split aptamer fragments (SPA1 and SPA2) were immobilized on AuNFs through Au-S bonds. The flower-like AuNFs provided a high-surface-area scaffold for aptamer loading, while the DNA modification further enhanced the peroxidase-like activity of AuNFs toward TMB oxidation. In the presence of Kana, target-induced assembly of SPA1 and SPA2 promoted the aggregation of AuNFs, which inhibited their catalytic activity toward TMB oxidation, thereby reducing oxTMB formation and the resulting colorimetric and electrochemical signals. Based on this signal-off mechanism, the platform enabled quantitative detection of Kana with linear ranges of 100-3000 nM for colorimetry and 50-2000 nM for chronoamperometry, with limits of detection of 0.51 and 0.074 nM, respectively. The method also showed satisfactory selectivity, reproducibility, and storage stability. In spiked environmental water samples, recoveries ranged from 87.7% to 106.2% with relative standard deviations below 5.0%, and the electrochemical results were in acceptable agreement with those obtained by HPLC-MS. This study provides a simple and effective dual-readout aptasensing strategy for Kana determination in environmental water samples.

Exosomes are regarded as cancer-associated biomarkers for early diagnosis and prognosis in clinical bioassays. Nevertheless, it remains a challenge to develop an approach that can achieve ultra-sensitive and quantitative detection of exosomes. Herein, an innovative dual-mode immunoassay dependent on surface-enhanced Raman scattering (SERS) and upconversion luminescence (UCL) was developed to detect prostate cancer-derived exosomes. A novel SERS-active immunosubstrate was constructed by combining black phosphorus (BP) with Ag nanoparticles, which exhibited an enhancement factor (EF) of about 3.69 × 10⁹, due to the synergistic electromagnetic and chemical effects. Meanwhile, an immunoprobe with stable and visually distinguishable UCL was developed based on Yb/Er co-doped NaGdF₄ nanoparticles with an intrinsic two-photon process. The specific capture of exosomes was achieved through antigen-antibody binding within the sandwich immunostructure, achieving limits of detection (LOD) as low as 93 and 172 particles/mL based on the dual-modal detection, respectively. Furthermore, the recognition of different derived exosomes was simply realized by visually observing the green fluorescence with different intensities, which paves the way for efficient preliminary identification of prostate cancer. Finally, the validation with clinical serum samples proved that the proposed approach holds significant promise for rapid cancer screening and diagnosis.