Chromogenic Mechanisms of Colorimetric Sensors Based on Gold Nanoparticles.

The colorimetric signal readout method is widely used in visualized analyses for its advantages, including visualization of test results, simple and fast operations, low detection cost and fast response time. Gold nanoparticles (Au NPs), which not only exhibit enzyme-like activity but also have the advantages of tunable localized surface plasmon resonance (LSPR), high stability, good biocompatibility and easily modified properties, provide excellent platforms for the construction of colorimetric sensors. They are widely used in environmental monitoring, biomedicine, the food industry and other fields.

Construction of Aggregation-Induced Emission Molecule-MnO Composite Nanoprobe and Its Application in Alkaline Phosphatase Detection.

Alkaline phosphatase (ALP) is among the most studied enzymes by far, playing an important role in the metabolism of organisms and the regulation of protein activity. Herein, a label-free composite nanoprobe is constructed by combining inorganic nanomaterials and aggregation-induced emission (AIE) molecule to achieve highly sensitive and selective detection of ALP. Negatively charged 9,10-bis [2-(6-sulfonatopropoxyl) naphthylethenyl] anthracene (BSNVA) molecule is synthesized, which has the AIE performance and can be assembled on the surface of amino-SiO nanoparticles through electrostatic interaction for fluorescence enhancement.

Enzymatically Activated Autonomous-Motion DNAzyme Signal Amplification Strategy for Tumor Cell-Specific Molecular Imaging with Improved Spatial Specificity.

Strategies for achieving tumor-specific molecular imaging based on signal amplification hold great potential for evaluating the risk of tumor metastasis and progression. However, traditional amplification strategies are still constrained with limited tumor specificity because of the off-tumor signal leakage. Herein, an endogenous enzyme-activated autonomous-motion DNAzyme signal amplification strategy (E-DNAzyme) was rationally designed for tumor-specific molecular imaging with improved spatial specificity.

Fluorescence-Enhanced Dual-Driven "OR-AND" DNA Logic Platform for Accurate Cell Subtype Identification.

Developing an endogenous stimuli-responsive and ultrasensitive DNA sensing platform that contains a logic gate biocomputation for precise cell subtype identification holds great potential for disease diagnosis and prognostic estimation. Herein, a fluorescence-enhanced "OR-AND" DNA logic platform dual-driven by intracellular apurinic/apyrimidinic endonuclease 1 (APE 1) or a DNA strand anchored on membrane protein Mucin 1 (MUC 1) for sensitive and accurate cell subtype identification was rationally designed. The recognition toehold of the traditional activated probe (TP) was restrained by introducing a blocking sequence containing an APE 1 cleavable site (AP-site) that can be either cleaved by APE 1 or replaced by Mk-apt, ensuring the "OR-AND" gated molecular imaging for cell subtype identification.

From Passive Signal Output to Intelligent Response: "On-Demand" Precise Imaging Controlled by Near-Infrared Light.

"On-demand" accurate imaging of multiple intracellular miRNAs will significantly improve the detection reliability and accuracy. However, the "always-active" design of traditional multicomponent detection probes enables them to passively recognize and output signals as soon as they encounter targets, which will inevitably impair the detection accuracy and, inevitably, result in false-positive signals. To address this scientific problem, in this work, we developed a near-infrared (NIR) light-activated multicomponent detection intelligent nanoprobe for spatially and temporally controlled on-demand accurate imaging of multiple intracellular miRNAs.

More Symmetrical "Hot Spots" Ensure Stronger Plasmon-Enhanced Fluorescence: From Au Nanorods to Nanostars.

Plasmon-enhanced fluorescence (PEF) is considered to be a powerful signal amplification technology to overcome intrinsic shortcomings of photobleaching and brightness of the traditional fluorescent dyes. Nevertheless, exploitation of PEF-based probes for bioimaging application is still at a very early stage. In this work, a simple but powerful gold nanostar (Au NST)@SiO-based PEF probe with 20 symmetric "hot spots" was developed for highly sensitive "lighting up" in situ imaging of intracellular microRNAs (miRNAs).

Water-soluble carbon dots with blue, yellow and red emissions: mechanism investigation and array-based fast sensing application.

In this study, three kinds of CDs with blue, yellow and red emissions were prepared and their luminescence mechanisms through theoretical calculations together with experimental data were further investigated in depth. Afterwards, a sensor array was constructed by using three kinds of CD-metal ions for rapid discrimination of different types of sulfur-containing species.

Study of the noncovalent interactions of ginsenosides and amyloid-β-peptide by CSI-MS and molecular docking.

Noncovalent interactions between drugs and proteins play significant roles for drug metabolisms and drug discoveries. Mass spectrometry has been a commonly used method for studying noncovalent interactions. However, the harsh ionization process in electrospray ionization mass spectrometry (ESI-MS) is not conducive to the preservation of noncovalent and unstable biomolecular complexes compared with the cold spray ionization mass spectrometry (CSI-MS).

Ultrahighly Efficient and Stable Fluorescent Gold Nanoclusters Coated with Screened Peptides of Unique Sequences for Effective Protein and Serum Discrimination.

Gold nanoclusters (Au NCs) coated with various peptides have been widely used as fluorescent probes, and nowadays the most commonly used are cysteine (C) and tyrosine (Y) based ones. Herein, we report the preparation and clinical application of highly efficient and stable fluorescent Au NCs protected by screened peptides with a specific amino acid sequence Cys-Met-Met-Met-Met-Met (CMMMMM). Compared with traditional C, Y based peptide (CYYYYY) protected Au NCs, the fluorescence intensity of the CMMMMM-Au NCs increased by 230%, and the photobleaching resistance or stability of the CMMMMM-Au NCs increased by about 300% (after continuous ultraviolet irradiation for 60 min, the fluorescence of the CMMMMM-Au NCs remained more than 90% of their initial intensity, while the CYYYYY-Au NCs remained less than 30%).

Core-shell gold nanocubes for point mutation detection based on plasmon-enhanced fluorescence.

Point mutation, with a permanent change in nucleic acid sequences, can affect the expression of genetic information forming the basis for numerous human genetic diseases, which makes its detection crucially important. Here, we reported a simple and sensitive method for point mutation detection, which employs a core-shell gold nanocube (Au NC) based on plasmon-enhanced fluorescence (PEF). For the generation of PEF, a Au NC was chosen as a core and silica as a spacer layer to adjust the distance between the Au NC and the dye of 5-carboxyfluorescein.

Polyphosphonate induced coacervation of chitosan: encapsulation of proteins/enzymes and their biosensing.

Based on the polyphosphonate-assisted coacervation of chitosan, a simple and versatile procedure for the encapsulation of proteins/enzymes in chitosan-carbon nanotubes (CNTs) composites matrix was developed. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), energy dispersive spectrum (EDS) mapping demonstrated the hemoglobin (Hb) uniformly distributed into chitosan-CNTs composites matrix. Raman measurements indicated the CNTs in composites matrix retained the electronic and structural integrities of the pristine CNTs.

Iron(III) diethylenetriaminepentaacetic acid complex on polyallylamine functionalized multiwalled carbon nanotubes: immobilization, direct electrochemistry and electrocatalysis.

A nonenzymatic iron(III) diethylenetriaminepentaacetic acid (Fe(III)-DETPA) complex based amperometric sensor for the analytical determination of hydrogen peroxide was developed. By combining the electrostatic interaction between the Fe(III)-DETPA complex and polyallylamine (PAH) functionalized multiwalled carbon nanotubes (MWCNTs) as well as the ionotropic crosslinking interaction between PAH and ethylenediamine-tetramethylene phosphonic acid (EDTMP), the electroactive Fe(III)-DETPA complex was successfully incorporated within the MWCNT matrix, and firmly immobilized on the Au substrate electrode. The fabricated electrochemical sensor was characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electrochemical methods.