Analytical Chemistry最新文献

The combination of diuron (DU) and thidiazuron (TDZ) is commonly used in cotton production for its excellent adaptability to low temperatures, which may lead to increased crop and soil pollution. The simultaneous detection of DU and TDZ poses significant challenges due to their weak and overlapping signals, along with an unclear electrochemical detection mechanism for TDZ. This study developed a dual-channel multifunctional molecularly imprinted electrochemical (MMIP-EC) sensing platform by optimizing the substrate material and MIP layer for high performance. First, amino-functionalized graphene-based poly(pyrrole)-poly(3,4-ethylenedioxythiophene) (NH₂-rGO/PPy-PEDOT) with high conductivity was synthesized as the substrate. Subsequently, MMIPs were prepared in one step using electropolymerization by introducing chloroauric acid (HAuCl₄) and bifunctional monomers (dopamine and thiophene). This method not only enhanced specific binding capacity of the MMIP layer but also amplified the signal through the synergistic effect of reduced AuNPs and bifunctional monomers. Furthermore, two independent modules (MMIP-DU and MMIP-TDZ) were integrated into a dual-channel EC platform for simultaneous transmission of DU and TDZ responses to separate windows. Finally, based on high-performance liquid chromatography–mass spectrometry (HPLC-MS) and electrochemical kinetics studies, it was speculated that the electrochemical oxidation of TDZ via the carbonylation of a secondary amine under strongly acidic conditions, followed by hydrolysis to form a carboxyl group, reveals the electrochemical oxidation mechanism of TDZ. The developed sensor exhibited excellent performance in selectivity and sensitivity, with low detection limits of 26.6 pg/mL (DU) and 39.2 pg/mL (TDZ). In conclusion, this sensing platform presents a novel perspective for the cost-effective and highly efficient detection of diverse environmental pollutants.

Individually addressable microelectrode arrays (MEAs) enable the simultaneous and independent measurement of multiple analytes and benefit from a small size scale, which enables highly localized electrochemical detection. In this work, we describe a new methodology to fabricate low-cost and tunable MEA probes in which the number, spatial arrangement, and spacing of the electrodes and electrode material can be changed and controlled. This was achieved using a 3D printed support assembly to position wires of the electrode material into designated positions and a mold to seal the electrodes in place using epoxy resin. After curing of the epoxy, mechanical polishing exposed the surface of closely spaced disk microelectrodes embedded in the insulating material, which formed the MEA. The individual electrodes of the array were characterized using electrochemical methods and optical and electron microscopy to evaluate the surface quality and the integrity of the seal with the insulating epoxy. To validate the fabrication method and to demonstrate the controlled electrode spacing, we used a dual-disk electrode device, while four-, five-, and seven-electrode probes were used to demonstrate some of the different numbers and geometric arrangements of electrodes that are possible. While the developed probes have numerous potential applications, including as probes or substrates in scanning electrochemical microscopy, we fabricated electrochemical aptamer-based sensors on the individual electrodes, for the simultaneous detection of adenosine triphosphate and dopamine in phosphate-buffered saline solution, with and without 10% fetal bovine serum.

Short-chain fatty acids (SCFAs) have attracted considerable interest as potential biomarkers, therapeutic targets, and nutritional factors in athletic training. SCFAs are typically produced by the intestinal microbiome and exhibit various structural forms, including linear- and branched-chain types. In particular, branched-chain SCFAs have been associated with muscle metabolism during exercise loading. Consequently, accurate and efficient analytical methods are essential for identifying these biomarkers. Liquid chromatography–tandem mass spectrometry is a suitable and accurate technique for SCFA analysis; however, stable isotope calibrations are required for all analytes. Because of technological limitations, the available species are restricted to certain types of SCFAs. To address this issue, this study performed a simple conversion reaction involving the incorporation of ¹⁸O into the carboxyl group. Specifically, oxygen atoms in the carboxyl groups were substituted with ¹⁸O sourced from commercially available H₂¹⁸O. An SCFA mixture standard solution was successfully labeled under optimized conditions, and the SIL purity and amount were sufficient for isotope dilution (95.2–96.9%, 250 assays using 10 μL of H₂¹⁸O). Moreover, no reversion to ¹⁶O was observed during storage or analysis. Analytical validation was performed in human serum using the substituted isotopic standard mixture, achieving good accuracy (90–110%) and precision (<10% relative standard deviation) across three concentration levels. Finally, changes in SCFA patterns were examined in athletes during exercise loading.

Circulating tumor cells (CTCs) have emerged as critical biomarkers in liquid biopsy for noninvasive tumor diagnosis and real-time monitoring of cancer progression. However, the isolation of CTCs is often required before detection due to their ultralow abundance in peripheral blood. These isolation processes are typically time-consuming and prone to cell loss, which limits the utility of CTC-based liquid biopsy. Herein, we present a DNA network-based diagnostic system that enables specific recognition, selective enrichment, and accurate detection of CTCs directly from blood samples. The DNA network comprises ultralong DNA chains embedded with polyvalent aptamers and fluorescence detection modules. The polyvalent aptamers selectively bind to the epithelial cell adhesion molecule (EpCAM) on a CTC membrane, facilitating their enrichment through base pairing-driven DNA network formation. This system semiquantitatively detects the expression level of cancer-associated microRNA within CTCs using ratiometric fluorescence imaging based on the chemical assembly of two fluorescence modules. In clinical blood samples, this diagnostic system achieves 100% precision and 96% accuracy in distinguishing breast cancer patients from healthy donors, highlighting its promising potential for clinical breast cancer diagnosis.