Microchimica Acta最新文献

A convenient and sensitive dual-signal visualization method is constructed for detection of trivalent chromium ions (Cr³⁺) based on fluorescent carbon dots (CDs) and glutathione-modified gold nanoparticles (GSH-Au NPs). The fluorescence of CDs can be quenched by GSH-Au NPs due to the inner filter effect. Cr³⁺ induces aggregation of GSH-Au NPs because of the coordination with GSH on the surface of Au NPs, leading to the red shift of surface plasmon resonance absorption of Au NPs that provides a "turn-on" fluorescence and colorimetric assay for Cr³⁺. The fluorescence/colorimetric dual signal detection shows high sensitivity for Cr³⁺ with wide detection linear ranges (0.5-70 μM for fluorescence detection and 2-50 μM for colorimetric detection) and low detection limits (0.31 μM for fluorescence detection and 0.30 μM for colorimetric detection). Besides, the method has high selectivity for Cr³⁺ and can be used for detection of Cr³⁺ in lake water and tap water samples, showing great potential for visual detection of environmental Cr³⁺.

Loofah sponge-like carbon nanofibers (LF-Co,N/CNFs) were utilized as a carrier for Ru(bpy)₃²⁺, and then combined with CdS to create a novel solid-state electrochemiluminescence sensor capable of detecting trace amounts of fenpropathrin. LF-Co,N/CNFs, obtained through the high-temperature pyrolysis of ZIF-67 coaxial electrospinning fibers, were characterized by a loofah-like morphology and exhibited a significant specific surface area and porosity. Apart from serving as a carrier, LF-Co,N/CNFs also functioned as a luminescence accelerator, enhancing the system's luminescence efficiency by facilitating electron transmission and reducing the transmission distance. The inclusion of CdS in the luminescence reaction, in conjunction with Ru(bpy)₃²⁺, further boosted the sensor's luminescence signal. The resulting sensor demonstrated a satisfactory signal, with fenpropathrin causing significant quenching of the ECL signal. Under optimized conditions, a linear relationship between the signal quench value and fenpropathrin concentration in the range 1 × 10^-12 to 1 × 10^-6 M was observed, with a detection limit of 3.3 × 10^-13 M (S/N = 3). This developed sensor is characterized by its simplicity, sensitivity, and successful application in detecting fenpropathrin in real samples. The study not only presents a straightforward detection platform for fenpropathrin but also introduces new avenues for the rapid determination of various food contaminants, thereby expanding the utility of carbon fibers in electrochemiluminescence sensors.

With the increasing demand for fruits and vegetables in the market, the development of cold chain logistics has put forward higher requirements for the quality of fruits and vegetables in storage. To ensure the freshness of fruits and vegetables during storage and transportation and avoid unnecessary loss, it is necessary to conduct real-time detection of their odor to ensure their quality. Therefore, based on nano-composite materials combined with Radio Frequency Identification (RFID) technology, this paper designs an integrated RFID sensor that can simultaneously detect temperature, carbon dioxide, and ethanol concentrations. The test results show that the sensor has a high sensitivity of 0.25 dB/°C, 0.011 dB/ppm, and 0.65 MHz/ppm for detecting temperature, carbon dioxide, and ethanol concentration, respectively. The sensor also uses Printed Circuit Board (PCB) technology to make the sensor base, which has the advantages of low cost, easy portability, and mass production capability. The results obtained evidence that the system meets the requirements of environmental monitoring for fruit and vegetable storage, runs stably, and has a high use value.

An electrochemical aptasensor was developed by utilizing a DNA walker driven by catalytic hairpin assembly (CHA) with kanamycin as the model analyte. Kanamycin bound to the aptamer, causes the release of DNA walker, triggers the CHA reaction, leads to the cyclic movement of the walker's long arm, and results in cascade amplification of the signal. The guanine-rich sequences of the double-stranded products produced by CHA were folded to form G-quadruplex structures, with electrochemical active molecules Hemin embedded, forms G-quadruplex/Hemin complexes in situ on the electrode surface, thereby achieving sensitive, efficient, and label-free detection of kanamycin with a limit of detection (LOD) of 0.27 pM (S/N = 3). Meaningfully, the aptasensor demonstrated high sensitivity and reliability in the detection of kanamycin in milk and livestock wastewater samples, suggesting that it has great potential for application in detecting antibiotics in food products and water samples from the environment.

Staphylococcus aureus (S. aureus) is a common foodborne pathogen, posing a serious threat to public health. Consequently, it is crucial to establish a platform for sensitive and specific determination of S. aureus in food. Herein, phage SapYZUH₅, isolated by our lab, was covalently immobilized on Co₃O₄ to synthesize SapYZUH₅@Co₃O₄. Notably, SapYZUH₅@Co₃O₄ exhibited remarkable oxidase-like activity, enabling the catalysis of dissolved oxygen to generate superoxide anion free radicals and accelerate the TMB chromogenic reaction. Upon introduction of S. aureus, specific capture by SapYZUH₅@Co₃O₄ resulted in inhibiting its oxidase-like activity and decelerating the 3,3',5,5'-tetramethylbenzidine (TMB) chromogenic reaction. Moreover, S. aureus can be lysed to release the reductive bacterial contents, which can further inhibit the TMB chromogenic reaction. Based on this principle, SapYZUH₅@Co₃O₄ + TMB reaction system was employed for detection with enhanced sensitivity of S. aureus, yielding an equation: A =  - 0.092 Log (C_SA) + 0.79 (R² = 0.987), with an ultralow limit of detection (LOD) of 28 CFU mL^-1. This system exhibited remarkable specificity and anti-interfere towards S. aureus, owing to the excellent affinity of SapYZUH₅ towards S. aureus. In addition, S. aureus in the actual food samples was detected using this system, yielding recoveries ranging from 96.34 to 109.43%, demonstrating its exceptional accuracy. Hence, our proposed covalent immobilization of phage on the nanozyme can realize sensitive and specific colorimetric determination of S. aureus in food samples.

A novel photoelectrochemical (PEC) sensor for the detection of microcystic toxins (MC-LR) was developed on the basis of signal-sensitive change strategy. NiO nanoarray as a basic photoactive material was grown directly on the ITO glass electrode via calcination after hydrothermal reaction, while dye N719 was used to sensitize the electrode for enhancing visible light absorption, and the first signal-on stage was obtained. In the meantime, p-type Cu₂O was applied as the signal probe attached to probe DNA (DNA₂) to improve the sensitivity, and the second "signal-on" stage appeared because of its synergistic effect with NiO nanoarrays. The PEC signal decreases after the target analyte MC-LR is modified on the electrode due to the stronger affinity between MC-LR and its complementary aptamer DNA; part of the Cu₂O-DNA₂ will dissociate from the electrode. This sensitive signal change strategy allows the detection limit of the MC-LR sensor to be as low as 1.7 pM, which offers an optional method for the sensitive and selective detection of other target molecules, with potential applications in environmental monitoring and toxin determination.

A novel sandwich-type electrochemical immunosensor for the detection of the liver cancer marker alpha-fetoprotein (AFP) in human serum is proposed. The two-dimensional MXene material Ti₃C₂T_x was first prepared using etching and ultrasonic stripping, and then Ti₃C₂T_x was used to reduce chloroauric acid to form Ti₃C₂T_x/AuNP composites which were modified on the surface of the glassy carbon electrodes to form probe-type sensors. The Ti₃C₂T_x/AuNPs provide a large number of binding sites for the AFP capture antibody (Ab1) and increase the electrochemical reaction active site. The Ti₃C₂T_x/copper metal-organic frameworks HKUST-1 composite was also prepared by solvothermal method and combined with toluidine blue (TB) and AFP detection antibody (Ab2) to form a labeled sandwich-type electrochemical immunosensor. The sensor achieved trace detection of AFP from 0.1 to 100 ng/mL with a detection limit of 0.073 pg/mL and possesses good selectivity, stability, and reproducibility. The sensor performs well in clinical samples and has good potential for clinical applications.

A simple and efficient dual-signal electrochemical sensor was designed for glyphosate (GLYP) determination based on the one-step electro-synthesized Cu-Hemin MOFs/CNTs nanocrystals. Cu-Hemin MOFs/CNTs were directly modified on the electrode through electrodeposition, avoiding complicated synthesis and modification processes. The incorporation of CNTs greatly boosted the conductivity of Cu-Hemin MOFs and the sensitivity of the electrochemical sensor. Cu active sites in Cu-Hemin MOFs were converted to CuCl, allowing the specific detection of GLYP with the turn of CuCl into non-electroactive Cu-GLYP. Meanwhile, GLYP showed highly effective inhibition effect on the inherent peroxidase-like activity of Cu-Hemin MOFs, therefore generating the second electrochemical signal with Cu-Hemin MOFs-catalyzed o-phenylenediamine (o-PD) + H₂O₂ system. The Cu-Hemin MOFs/CNTs based sensor with two electrochemical signals showed good linearities of 1.0 × 10^-10 M - 3.0 × 10^-6 M and 1.0 × 10^-10 M - 5.0 × 10^-5 M, with detection limits of 5.17 × 10^-12 M and 6.81 × 10^-12 M for the CuCl signal based assay and nanozyme catalyzed o-PD + H₂O₂ procedure, respectively. This simple and robust dual-signal sensor with excellent selectivity, accuracy, and stability allowed GLYP quantification in real samples, highlighting the potential application of this approach for food and environmental monitoring.

A fluorescent and colorimetric dual-mode strategy based on carbon dots (CDs) was rationally designed for sensitive determination of Cu²⁺. Green fluorescent CDs with high absolute quantum yield of 72.9% were synthesized by facile one-step hydrothermal treatment of triethylenetetramine and Rose Bengal. Cu²⁺ could trigger the oxidative and chromogenic reaction of p-phenylenediamine (PPD) to generate chromogenic PPDox, accompanied by the fluorescence quenching of the CDs. The quenching mechanism was identified as the inner filter effect between PPDox and CDs. Therefore, a colorimetric/fluorescent dual-mode detection method for Cu²⁺ recognition was constructed. The limits of detection for Cu²⁺ were 4.14 μM and 1.28 μM for colorimetric and fluorescent mode, respectively. In addition, this method had achieved satisfactory results in the detection of Cu²⁺ in real serum samples.

Using nitrogen-doped graphene quantum dots (N-GQDs) and 3-aminophenylboronic acid (APBA), a novel fluorescence nanosensor was developed. This nanosensor exhibits high selectivity and sensitivity for lysine detection. Its sensing mechanism involves the suppression of electron transfer from APBA to the N-GQDs unit, thereby inhibiting photoinduced electron transfer and initiating internal charge transfer. At an optimal pH of 7, the protonated α-amine and ε-amine groups of lysine interact with the amide and boronic acid moieties, respectively. This interaction results in a redshift of fluorescence, substantially enhancing the response signal. A linear response was observed within a concentration range 0.40-3.01 μM, with the detection limit being 0.005 μM. A similar linear range was also achieved for the determination of lysine in human serum. Density functional theory calculations correlating molecular orbits and geometries support UV-vis and fluorescence findings. Additionally, the nanosensor was successfully applied to detect lysine in living cells and real samples, including milk and honey. For practical application, we construct a lysine-specific sensing platform using a commercial chip (TCS34725) that collects red, blue, and green signals, thereby facilitating the convenient use of the nanosensor. Overall, this study offers new perspectives on the development and application of fluorescent nanosensors for detecting individual amino acids.