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ECL-RET in BP/MnO2 nanocomposites coupled with glutathione-loaded liposomes for the immunoassay of proteins.

A spatially resolved ratiometric ECL immunosensor for myoglobin detection was developed via resonance energy transfer for signal amplification.

Molecular logic computation has drawn extensive attention in the fields of bioanalysis, intelligent diagnostics of diseases and other nanotechnology areas. DNA-templated Au nanoclusters (DNA-AuNCs) possess some excellent features, including high luminescence, good photo-stability and easy preparation. Herein, taking these advantages of DNA-AuNCs, we have designed and constructed a universal platform of label-free and enzyme-free multiple molecular logic gates, including NOR, XNOR, IMPLY, OR, AND, and INHIBIT. The experimental results have demonstrated the feasibility of these logic gates operations using Hg2+, Cu2+, biothiols, melamine and pyrophosphate (PPi) as inputs. Thus, the universal platform can be utilized for the determination of biothiols, melamine and pyrophosphate (PPi) via logic outputs. The strategy exhibited low cost, easy operation and versatile design, and can offer a promising platform for the development of functional logic systems.

A novel chemiluminescence (CL) immunosensor using functionalized tungsten disulfide nanosheets (WS2 NSs)–gold nanoparticles (Au NPs)–horseradish peroxidase (WS2–Au–HRP) as multiple signal amplification probe was developed for prostate specific antigen (PSA) analysis. The WS2–Au nanocomposites were synthesized by in situ growth of Au NPs on the surface of WS2 NSs. HRP and antibody for recognizing the target were subsequently functionalized on WS2–Au. Owing to the large loading capacity of the WS2 NSs, the WS2–Au–HRP nanoprobe exhibits synergistic enhancement to the luminol–H2O2 CL system. The kinetics and spectra of CL from the luminol–H2O2–WS2–Au–HRP system were studied and the CL mechanism is discussed. Exemplified by PSA as target, the ultrasensitive CL immunoassay of PSA was achieved owing to the multiple signal amplification of the WS2–Au–HRP nanoprobe. The detection limit is 3.0 × 10−14 g mL−1 with a linear range of 1.0 × 10−13 to 1.0 × 10−8 g mL−1. Furthermore, the method was applied to human serum sample analysis with high selectivity and reproducibility. The method provides a novel ultrasensitive CL detection tool for biomarkers in real samples.

Water splitting into hydrogen (H2) to produce clean energy is of great significance for sustainable development. Transition metal phosphides (e.g., Ni12P5 nanoparticles) may be used as non-precious earth-abundant electrocatalysts for the H2 evolution reaction, but their poor electronic conductivity and small surface area hinder efficient catalytic H2 production. In this research, we demonstrate for the first time the facile synthesis of porous carbon/Ni12P5 (C/NiP-C) composites with the dispersion of Ni12P5 nanoparticles onto a conductive porous carbon support in an ionic surfactant hexadecyl trimethyl ammonium bromide (CTAB)-mediated ethanol solution. The CTAB plays dual roles in the synthesis including (1) the introduction of carbon to increase the conductivity of the synthetic materials and (2) the formation of uniform Ni12P5 phosphides through the interaction between the H2PO2− anion, Ni2+, and C19H42N+ cation dissociated from CTAB. The obtained C/NiP-C composites may function as electrocatalysts for the hydrogen evolution reaction (HER) with excellent HER performance (η: 63 mV, η10: 176 mV, Tafel slope: 100 mV dec−1, wherein η represents the onset overpotential and η10 represents the overpotential required for a current density (j) value of −10 mA cm−2) compared with the NixPy composites synthesized in pure ethanol (η: 160 mV, η10: 392 mV, Tafel slope: 154 mV dec−1), the C/NiP-P composites synthesized in a P123-mediated ethanol solution (η: 75 mV, η10: 286 mV, Tafel slope: 210 mV dec−1), and the C/NiP-F composites synthesized in a F127-mediated ethanol solution (η: 80 mV, η10: 302 mV, Tafel slope: 189 mV dec−1). The enhanced HER performance can be attributed to the synergistic effects resulting from the unique structure of the porous C support and the well dispersed Ni12P5 nanoparticles.

A novel fluorescence (FL) immunosensor for prostate-specific antigen (PSA) detection was developed based on the Forster resonance energy transfer (FRET) between nitrogen and sulfur co-doped carbon dot functionalized silica nanospheres (Si/NS-CDs) and Au@Ag NPs. The strategy utilized the PSA primary antibody labeled luminescent Si/NS-CDs as donors and PSA secondary antibody labeled Au@Ag NPs as acceptors. In the presence of PSA, the bio-affinity of the antigen and antibody caused the Si/NS-CDs and Au@Ag NPs to approach at a close enough distance for the FL intensity of the Si/NS-CDs to decline owing to the FRET effect. By virtue of the excellent optical properties of the Si/NS-CDs nanoprobe, the quantitative analysis of PSA has been successfully realized using both FL spectroscopy and a naked-eye readout. The fluorometric results present the desirable analytical performance for PSA detection in the range from 5.0 pg mL−1 to 10 ng mL−1 with a detection limit of 0.95 pg mL−1 (S/N = 3). Moreover, satisfactory results for the determination of the PSA target in samples of human serum were obtained, showing the great promise of the method for application in biochemical analysis.

In this study, a simple and label-free colorimetric sensing strategy was reported for rapid and selective detection of dopamine by inhibiting the Cu2+-catalyzed oxidation of a 3,3′,5,5′-tetramethylbenzidine (TMB)–H2O2 system. Similar to natural peroxidase, Cu2+ could catalyze the oxidation of the peroxidase substrate TMB to oxidized TMB (ox TMB) in the presence of H2O2, producing a blue color. However, dopamine could chelate with Cu2+ to form stable dopamine–Cu2+ complexes by strong coordination between Cu2+ and dopamine. It was found that the formation of dopamine–Cu2+ complexes hindered the Cu2+-catalyzed oxidation of the TMB–H2O2 system. As a result, in the presence of dopamine, the solution color changed from blue to colorless with a remarkable decrease of absorbance. Under optimized experimental conditions, the colorimetric sensor exhibited a linear range of 1 μM to 50 μM for dopamine detection, with a detection limit of 1 μM. Furthermore, the proposed method was successfully applied to determine the dopamine content in real samples. Compared with other reported methods, the colorimetric method could be performed within several minutes and did not require any complex or time-consuming preparation and purification process. The results suggested that this strategy would have potential applications in biotechnology and clinical diagnosis.

A simple, rapid and label-free fluorescent sensing strategy has been developed for the detection of L-histidine on the basis of the inhibition of double-stranded DNA (ds-DNA) templated copper nanoparticles (Cu NPs) by L-histidine. Fluorescent Cu NPs were formed within 5 min at room temperature by using random ds-DNA as a template. However, the fluorescence intensity decreased obviously in the presence of L-histidine. This was mainly ascribed to the strong interaction between L-histidine and Cu2+, which would hamper the effective formation of fluorescent Cu NPs, leading to low fluorescence intensity. Under the optimized conditions, the strategy exhibited sensitive and selective detection of L-histidine with a detection limit of 20 nM. In addition, the method was successfully applied in the detection of histidine in human urine samples. This method was cost-effective and convenient without any labels or complicated operations. Thus, it could offer a simple, rapid and sensitive fluorescent platform for the detection of L-histidine.

A simple coupled synthesis and encapsulation route was developed to fabricate monodisperse, uniform Ag@C@Ag core–shell structured nanocomposites with excellent electrochemical and catalytic properties, in which Ag nanoparticles were first encapsulated in a carbonaceous shell through the catalyzed dehydration of glucose under hydrothermal conditions, and then the surface-activated Ag@C spheres were subsequently used to accumulate [Ag(NH3)2]+ or Ag+ ions through electrostatic attraction to anchor the Ag coating. The as-prepared nanocomposites were demonstrated to have a great potential for the simultaneous multiplexed detection of thymol and phenol, and exhibited high sensitivity and good reproducibility. In addition, the practical analytical application of the sensing platform was assessed by the determination of thymol and phenol in real honey samples, and satisfactory results were achieved.

In this paper, a novel fluorescence biosensing strategy based on GR-5 DNAzyme has been developed for the simple, rapid, sensitive and selective detection of lead ions (Pb2+) by using gold nanoparticles (AuNPs) as the fluorescence quencher. Data from dynamic light scattering (DLS) and zeta potential measurements demonstrated that GR-5 DNAzyme functionalized AuNPs were successfully prepared with good dispersion in aqueous solution. The carboxyfluorescein (FAM) labeled GR-5 DNAzyme was in close proximity to the AuNPs and the fluorescence signal was quenched, when the DNAzyme was modified on the surface of AuNPs. In the presence of Pb2+ ions, the GR-5 DNAzyme was activated and cleaved the substrate strand at the RNA site (rA) into two parts, which led to a short FAM-linked oligonucleotide fragment being released from the surface of the AuNPs, and the fluorescence intensity was gradually recovered. By taking advantage of the high fluorescence quenching efficiency of AuNPs, our proposed method exhibited a high sensitive detection of Pb2+ ions with a detection limit of 250 pM and a linear range from 1 nM to 100 nM. With the choice of a classic GR-5 DNAzyme instead of 8-17 DNAzyme as the catalytic unit, the selectivity of this strategy was obviously improved compared with previously reported methods. Moreover, this biosensing strategy was also used for the determination of Pb2+ in lake water samples with satisfying results. The strategy would find potential applications in environmental and biomedical fields.