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Filling the microchannel with negatively charged hydrogel can exhibit microsacle ion current rectification (ICR) behavior, which is attributed to the space negative charge and structural asymmetry of hydrogel. In this study, this character had been applied to develop a trypsin sensor for the first time. A hydrogel synthesized with bovine serum albumin (BSA) and glyoxal (BSAG hydrogel) was filled at the tip of microchannel firstly. Subsequently, the BSAG hydrogel-filled microchannel was immersed in a trypsin solution to hydrolyze the BSA within the BSAG hydrogel. This process changes the space charge density and pore size of the BSAG hydrogel-filled microchannel, leading to a change in microscale ICR, which can be used for quantifying trypsin. Then the key parameters affecting the sensing performance such as the concentration of BSA, strength of the electrolyte, pH and reaction time were optimized. The detection range was from 10.0 ng/mL to 100 μg/mL with a detection limit as low as 2.55 ng/mL (S/N = 3). Due to the distinctive three-dimensional pore structure of the hydrogel and the specificity of trypsin for BSA hydrolysis, the sensor exhibits high sensitivity and specificity, as well as remarkable reproducibility and stability. This sensor has been effectively used to measure trypsin levels in human serum samples.

Owing to the facile fabrication and surface modification, the cost-effective polymer nanopores are widely employed in unimolecular determination of biomacromolecules and selective sensing of small molecules, nanoparticles and biomarkers. However, the documented polymer nanochannels are generally microscale in length with low spatial resolution. We herein synthesized azobenzene side-chain polymer (Azo-PMA) and spin-coated on silicon nitride membrane to obtain a polymer film of nanoscale thickness for further nanopore generation via controlled dielectric breakdown (CDB) approach. The Azo-PMA nanopores demonstrate good ions transporting activities, pH tolerance and stability in high concentration of electrolyte with low ionic current noise. In addition, the azobenzene-containing polymer nanopores exhibit photo-response upon UV/Vis. light irradiation. The Azo-PMA nanopore devices are utilized for linear and quadruple nucleic acids discrimination, sensing of proteins with distinct shapes and sizes, as well as the single amino acid resolution with good capture rate and sensitivity. We established an unimolecular sensing platform using polymer nanopores for nucleic acids and proteins detection with good spatial resolution, which will be an addition for the nanopore-carrier material exploration and applications in potential genomics and proteomics with high spatiotemporal resolution and low cost.

Catechol (CC) is an important environmental pollutant due to its toxicity, non-degradability and widespread distribution. The rapid, sensitive, and selective detection of CC remains a challenging task owing to the coexistence of multiple phenolic pollutants with similar structures and properties in the environment. This article proposed an electrochemical sensing system that combined a molecularly imprinted sensing interface and ratiometric indicator displacement assay (IDA) for sensitive and selective detection of CC. A unique carbon nanotubes (CNTs) interpenetrating ZIF-8 material (CNT@ZIF-8) was successfully prepared and utilized as a support for surface molecular imprinting of CC. As a substrate material, CNT@ZIF-8 increased the electroactive surface area of the electrode, improved electronic conductivity, and promoted the bonding stability of molecularly imprinted polymer (MIP) film on the electrode. The developed sensing interface exhibited excellent adsorption affinity, enrichment ability, and signal transduction ability towards CC. On this basis, a novel IDA method based on ratiometric electrochemical signals was developed using epinephrine (EP) as a competitive indicator. The proposed electrochemical sensing platform had a wide linear range of 1-1000 μM with a detection limit of 0.23 μM and exhibited high anti-interference ability, good repeatability, superior regenerability, and long-term stability. The sensing system was applied to the analysis of CC in tap water and green tea samples, with recoveries of 94.4 %-104 % and 95.7 %-106.7 %, respectively, demonstrating broad practical application prospects. This study not only provides a promising conductive material for surface molecular imprinting and electrochemical sensing but also offers a reliable strategy for the electrochemical detection of CC.

Breast cancer is one of the most prevalent malignancies worldwide, with HER2-overexpressing subtypes exhibiting increased aggressiveness and poorer prognosis. Accurate identification of HER2-positive subtypes is essential for the effective implementation of HER2-targeted therapy. In this study, an electrochemical fluorescence dual-mode strategy was developed for the high sensitive detection of HER2-positive breast cancer cells. Immunofluorescent quantum dot probes (IFQDs) with both fluorescence and enzyme catalysis were constructed. It labelled HER2 sites on the cell membrane to enable fluorescent imaging and cell counting. Furthermore, alkaline phosphatase (ALP) on the probe surface catalyzed the reduction of silver on the surface of the Au NPs@ITO electrode through enzyme-induced metallization, thereby enabling quantitative detection of the cells via stripping voltammetry. The application of two methods, namely enzyme-induced metallization and enrichment of signal species on the electrode surface, significantly enhanced the sensitivity of this analytical strategy. The self-monitoring of dual signals achieved more accurate analytical performance. The dual-mode strategy demonstrated satisfactory results in identifying breast cancer cells with varying HER2 expression levels and even in complex samples. It indicated that the electrochemical fluorescence dual-mode strategy had potential for typing and quantitative detection of cells with varying HER2 expression levels.

Prompt and personalized perioperative analgesia management relies on sensitive and convenient monitoring of analgesics. We report a strategy for sensitive and reproducible SERS detection of analgesics based on Ag nanocubes, which have abundant intragranular hot spots on sharp corners and interparticle hot spots between gaps. Both theoretical simulations and R6G detection experiments indicated that the enhancement factor of Ag nanocube SERS platform reach to 10⁶ level. Quantitative and reproducible determination capabilities of this platform for six different analgesics with LOD as low as 500 pg mL^-1 were verified. Pharmacokinetic experiment of fentanyl in rat serum samples by SERS detection within 4 h presented consistent results with the UHPLC-MS/MS method. Valid examples of SERS detection for single or multiple analgesics in clinical patients' serums further proved the feasibility of this platform for perioperative analgesic monitoring.

The method of detecting acetone levels in breath presents a promising approach for monitoring diabetes mellitus (DM). Consequently, the detection of acetone in exhaled breath is garnering significant attention. However, using ultraviolet differential optical absorption spectroscopy (UV-DOAS) for detection of the exhaled acetone has rarely been proposed due to the complex composition of exhaled gases and the baseline drift caused by the acetone absorption feature. In this study, we present an optical sensor based on an improved UV-DOAS and spectral upgrading, enabling the detection of exhaled acetone in the sub-200 nm wavelength band for the first time. Firstly, the overall fitting process in the UV-DOAS was improved to segmental fitting to address the issue of baseline drift, resulting in a standard differential absorption spectrum for acetone. Secondly, a spectral upscaling concentration inversion method based on wavelet coefficient matrix is proposed. This helps effectively handle spectral overlaps among oxygen (O₂), ammonia (NH₃), and acetone through the additional time-frequency information provided by spectral upscaling. Laboratory-based results demonstrate that our sensor achieves a detection limit of 14.97 ppb∗m, representing exceptional performances. Tests on human exhaled breath samples revealed that the sensor can detect acetone at ppb levels, with concentrations rising alongside increased lipid metabolism. Our optical sensor offers high accuracy and stability, demonstrating significant potential and value for non-invasive early diabetes diagnosis.

The incorporation of fluorinated amino acids into proteins through natural biosynthesis in E. coli often leads to the production of heterogeneous fluorinated proteins. The stabilities of proteins with different ¹⁹F labelling states can vary, but these differences are challenging to measure due to the difficulty in separating the fluorinated protein mixtures that differ by only a few ¹⁹F atoms. Here, we simultaneously incorporated both fluoro-phenylalanines (3-fluoro-phenylalanine, 3FF; or 4-fluoro-phenylalanine, 4FF) and 5-fluoro-tryptophan (5FW) into GB1 protein. We are able to measure the stability of GB1 protein with different ¹⁹F labelling states without the need for sample separation by taking the advantage of ¹⁹F NMR. The results showed that 4FF-5FW-GB1 with varying ¹⁹F labelling states exhibited significantly different protein stability, with higher 4FF labeling efficiency correlating with decreased stability. Furthermore, residues F₃₀ and F₅₂ show synergistic effects on GB1 stability. In contrast, the 3FF and 5FW substitution exhibits a slightly stabilizing effect on GB1 stability. The present research provides a convenient ¹⁹F NMR method to simultaneously measure fluorine labelling effects on protein stability, favouring precise understanding and analysis of fluorine labelling effects.

Perfluorinated compounds (PFCs), recognized as emerging environmental pollutants of global concern due to their persistence and bioaccumulation, have posed serious threats to human health. This underscores the critical need for developing rapid and accurate detection methods for PFCs. In this study, we proposed a novel electrochemical detection approach for perfluorooctanoic (PFO), a representative PFC, employing a WS₂-AC-modified Cu-MOF(199) electrode integrated with molecularly imprinted polymer (MIP) technology. The MIP, tailored for PFO recognition, was synthesized through electropolymerization of o-phenylenediamine (o-PD) on WS₂-AC@Cu-MOF(199) composites. Selective adsorption of PFO was enabled by hydrogen bonding interactions between the MIP and target molecules, and achieved effective detection after template elution. The method demonstrated high sensitivity with a broad linear detection range from 34 ng/L to 10.20 μg/L and an ultralow detection limit of 15.15 ng/L. Beyond its sensitivity, this technique exhibited advantages including low fabrication‌ costs, strong anti-interference capabilities, and exceptional selectivity and reproducibility. Notably, this method demonstrated a higher spike recovery compared to GC-MS in PFO detection. These combined features position it as a promising solution for monitoring PFO contamination in aquatic environments.