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To monitor the deteriorating mercury emissions, it is imperative to propose methods for detecting mercury ions (Hg2+) with sensitivity and selectivity. The SERS spectral-resolved single-particle detection approach can be carried out using dark-field optical microscopy (DFM) combined with Raman spectroscopy. Herein, we have designed a novel yet convenient single-particle detection assay for quantifying Hg2+ using DFM-correlated Raman spectroscopy. In the assay, a tetrahedral DNA-directed core-satellite nanostructure is used as the SERS probe. Especially, one edge of the tetrahedron is made up of a single-stranded DNA containing a Hg2+ aptamer, which reconfigures upon the specific recognition of Hg2+. As a result, the interparticle distance reduces from 4.5 to 1.2 nm, thus generating Raman signal enhancement. As a proof of concept, Hg2+ was detected in a linear range from 1 to 100 nM based on the variation in SERS intensity. Furthermore, the experimental results were supported by the finite difference time domain (FDTD) calculations. Owing to its high sensitivity and selectivity, this method was further employed to detect Hg2+ in practical tap water and lake water samples, revealing that the single-particle detection strategy holds great promise for Hg2+ analysis in real environment analysis. [ABSTRACT FROM AUTHOR]

Well-dispersed chiral Ag2S quantum dots (Ag2S QDs) were facilely synthesized by using N-acetyl- L -cysteine (NALC) as the chiral ligand and loaded onto nanosheets of two-dimensional (2D) few-layer carbon nitride (C3N4). The resultant nanocomposite (Ag2S QDs/few-layer C3N4) shows enhanced electrochemiluminescence (ECL) while maintaining the chirality of Ag2S QDs, which can be used for the chiral discrimination of the enantiomers of tyrosine (Tyr). Due to the higher affinity of chiral Ag2S QDs toward L -Tyr than toward its enantiomer, the ECL intensity of Ag2S QDs/few-layer C3N4 is significantly decreased after its incubation with L -Tyr, and thus the Tyr enantiomers can be discriminated. The developed ECL chiral sensor exhibits high stability and reproducibility. The universality of the ECL chiral sensor for the discrimination of other chiral amino acids is also studied, and the results indicate that it can work only in the case of chiral aromatic amino acids. [ABSTRACT FROM AUTHOR]

In this work, bovine serum albumin (BSA)–Au nanoclusters were used to coat a paper-based microfluidic device. This device acted as a Cu2+ biosensor that showed fluorescence quenching on detection of copper ions. The detection limit of this sensor could be adjusted by altering the water absorbing capacity of the device. Qualitative and semi-quantitative results could be obtained visually without the aid of any advanced instruments. This sensor could test Cu2+ rapidly with high specificity and sensitivity, which would be useful for point-of-care testing (POCT). [ABSTRACT FROM AUTHOR]

A novel strategy for the quantitative determination of human colon cancer DLD-1 cells utilizing an electrochemical aptasensor was developed by effective surface recognition between Mucin 1 glycoprotein over-expressed on the cell membrane and MUC-1 aptamer (MUC-1) bound on carbon nanospheres (CNSs). An MTT assay revealed that the as-prepared CNSs by green route exhibited satisfactory biocompatibility for cell viability, providing a suitable platform for the cell adhesion study. Furthermore, using CNSs as a sensing layer accelerated electron transfer and provided a highly stable matrix for the convenient conjugation of target MUC-1 aptamer, considerably amplifying the electrochemical signals. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were applied to assess the optimal conditions and detection performance of the as-fabricated aptasensor. The attachment of colon cancer DLD-1 cells onto the MUC-1 aptamer immobilized CNSs led to increased EIS responses, which changed linearly in cell concentration ranging from 1.25 × 102 to 1.25 × 106 cells per mL with a lower detection limit of 40 cells per mL. With this method, colon cancer DLD-1 cells can be easily distinguished from normal cells, Human astrocytes 1800. The novel aptasensor revealed high specificity to DLD-1 cells. Furthermore, the aptasensor described here showed good reproducibility and high stability because of the CNSs of high stability and biocompatibility. The proposed protocols are a promising technique for the early monitoring of human colon cancer, and might have potential clinical applications such as cancer diagnosis, drug screening. [ABSTRACT FROM AUTHOR]

Well-dispersed chiral Ag 2 S quantum dots (Ag 2 S QDs) were facilely synthesized by using N -acetyl-L-cysteine (NALC) as the chiral ligand and loaded onto nanosheets of two-dimensional (2D) few-layer carbon nitride (C 3 N 4 ). The resultant nanocomposite (Ag 2 S QDs/few-layer C 3 N 4 ) shows enhanced electrochemiluminescence (ECL) while maintaining the chirality of Ag 2 S QDs, which can be used for the chiral discrimination of the enantiomers of tyrosine (Tyr). Due to the higher affinity of chiral Ag 2 S QDs toward L-Tyr than toward its enantiomer, the ECL intensity of Ag 2 S QDs/few-layer C 3 N 4 is significantly decreased after its incubation with L-Tyr, and thus the Tyr enantiomers can be discriminated. The developed ECL chiral sensor exhibits high stability and reproducibility. The universality of the ECL chiral sensor for the discrimination of other chiral amino acids is also studied, and the results indicate that it can work only in the case of chiral aromatic amino acids.

In this work, bovine serum albumin (BSA)-Au nanoclusters were used to coat a paper-based microfluidic device. This device acted as a Cu(2+) biosensor that showed fluorescence quenching on detection of copper ions. The detection limit of this sensor could be adjusted by altering the water absorbing capacity of the device. Qualitative and semi-quantitative results could be obtained visually without the aid of any advanced instruments. This sensor could test Cu(2+) rapidly with high specificity and sensitivity, which would be useful for point-of-care testing (POCT).