General Strategy to Fabricate Electrochemiluminescence Sandwich-Type Nanoimmunosensors Using CdTe@ZnS Quantum Dots as Luminescent Labels and Fe₃O₄@SiO₂ Nanoparticles as Magnetic Separable Scaffolds

This work aims to develop universal sandwich-type electrochemiluminescence (ECL) nanoimmunosensors for quantitative detection of biomarkers. A series of low-toxic CdTe@ZnS QDs with different core sizes have been synthesized via hydrothermal method and characterized by UV–vis spectra, photoluminescence spectra, TEM, EDS, and XRD. Especially, the ECL behaviors of CdTe@ZnS QDs have been investigated carefully. The CdTe@ZnS QDs with the highest ECL quantum yields have been chosen as ECL labels for conjugation with secondary antibodies. The QDs-labeled antibodies have been characterized by agarose gel electrophoresis. Meanwhile, Fe₃O₄@SiO₂ magnetic nanoparticles were utilized as nanocarriers for the immobilization of primary antibodies due to magnetic separation ability, large specific surface area, and ease of amination for biofunctionalization. Successful fabrication of the nanoimmunosensor was confirmed by SEM and electrochemical impedance spectroscopy. Carcinoembryonic antigen was detected as a model to prove the feasibility of the above strategy. Under the optimal conditions, the proposed nanoimmunosensor exhibited a wide linear range of 0.01 to 125 ng mL^–1 for carcinoembryonic antigen determination with a low detection limit of 3.0 pg mL^–1 (S/N = 3). Moreover, the nanoimmunosensor also displayed excellent selectivity, good stability, and acceptable reproducibility, indicating its potential applications in clinical diagnostics and immune research

One-Pot Green Synthesis of High Quantum Yield Oxygen-Doped, Nitrogen-Rich, Photoluminescent Polymer Carbon Nanoribbons as an Effective Fluorescent Sensing Platform for Sensitive and Selective Detection of Silver(I) and Mercury(II) Ions

This work reports on a facile, economical, and green preparative strategy toward water-soluble, fluorescent oxygen-doped, nitrogen-rich, photoluminescent polymer carbon nanoribbons (ONPCRs) with a quantum yield of approximately 25.61% by the hydrothermal process using uric acid as a carbon–nitrogen source for the first time. The as-prepared fluorescent ONPCRs showed paddy leaf-like structure with 80–160 nm length and highly efficient fluorescent quenching ability in the presence of mercury­(II) (Hg²⁺) or silver (Ag⁺) ions due to the formed nonfluorescent metal complexes via robust Hg²⁺-O or Ag⁺-N interaction with the O and N of fluorescent ONPCRs, which allowed the analysis of Hg²⁺ and Ag⁺ ions in a very simple method. By employing this sensor, excellent linear relationships existed between the quenching degree of the ONPCRs and the concentrations of Hg²⁺ and Ag⁺ ions in the range of 2.0 nM to 60 μM and 5.0 nM to 80 μM, respectively. By using ethylenediaminetetraacetate and ammonia as the masking agent of Hg²⁺ and Ag⁺ ions, respectively, Hg²⁺ or Ag⁺ ions were exclusively detected in coexistence with Ag⁺ or Hg²⁺ ions with high sensitivity, and the detection limits as low as 0.68 and 1.73 nM (3σ) were achieved, respectively, which also provided a reusable detection method for Hg²⁺ and Ag⁺ ions. Therefore, the easily synthesized fluorescent ONPCRs may have great potential applications in the detection of Hg²⁺ and Ag⁺ ions for biological assay and environmental protection

Determination of Thiols by Fluorescence using Au@Ag Nanoclusters as Probes

<div><p>A simple and label-free fluorescent assay for the sensitive determination of biological thiols was developed using Au@Ag nanoclusters. The sensing approach was based on the strong affinity of thiols to silver on the surface of the nanoclusters. In the presence of thiol-containing amino acids, the fluorescence of the Au@Ag nanoclusters was quenched due to the formation of a non-fluorescent coordination complex via the robust Ag-S bond, which allowed the determination of thiol-containing amino acids in a very simple and rapid way. Under the optimal conditions, an excellent linear relationship was present due to quenching of the Au@Ag nanoclusters over cysteine concentrations between 20 nM and 80 µM with a low detection limit of 5.87 nM. Glutathione was determined between 2 µM and 70 µM with a detection limit of 1.01 µM. In addition, the results reveal that the fluorescent assay has excellent selectivity toward thiol-containing amino acids compared to non-thiol containing amino acids. Moreover, the assay was successfully used to determine cysteine in human plasma, and thus Au@Ag nanoclusters are a suitable fluorescent probe for biological applications.</p></div

Nonenzymatic Amperometric Aptamer Cytosensor for Ultrasensitive Detection of Circulating Tumor Cells and Dynamic Evaluation of Cell Surface N‑Glycan Expression

Dynamic assessment of glycan expression on the cell surface and accurate determination of circulating tumor cells are increasingly imperative for cancer diagnosis and therapeutics. Herein, a unique and versatile nonenzymatic sandwich-structured electrochemical cytosensor was developed. The cytosensor was constructed based on a cell-specific aptamer, the lectin-functionalized porous core–shell palladium gold nanoparticles (Pd@Au NPs). To establish the cytosensor, amine-modified-SYL3C aptamer was first attached to the surface of aminated Fe₃O₄@SiO₂ nanoparticles (Fe₃O₄@SiO₂–NH₂ NPs) through cross-linked reaction via glutaraldehyde. Besides, in terms of noncovalent assembly of concanavalin A on Pd@Au NPs, a lectin-functionalized nanoprobe was established. This nanoprobe had the capabilities of both the specific carbohydrate recognition and the current signal amplification in view of the Pd@Au NPs as the electrocatalyst for the reduction of hydrogen peroxide (H₂O₂). Herein, we used MCF-7 cells as a model target, and the constructed cytosensor showed a low detection limit (down to three cells), a wide linear detection ranging from 100 to 1 × 10⁶ cells mL^–1. The established method sensitively realized the detection of the amount of cell and exact evaluation of glycan expression on cell surface, demonstrating great application prospects