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• A dicyanoisophorone-based fluorescent probe was developed for sensing H 2 S with a large Stokes shift (155 nm). • The probe showed faster time response and high sensitivity for H 2 S. • The probe can be used to detect exdogenous and endogenous H 2 S in living HeLa cells. Due to the importance of hydrogen sulfide (H 2 S) in physiology and pathology, the development of fluorescence probes for the detection of H 2 S has attracted extensive attention of researchers. We developed a H 2 S fluorescence probe (DCN-S) based on dicyanoisopentanone using dithioether and ester groups as the reaction sites. Under the nucleophilic substitution of H 2 S, disulfide bond of DCN-S was broken. Then the probe changed into dicyanoisophorone derivative and emitted an orange fluorescence band from 530 nm to 700 nm (centred 580 nm). Upon response for H 2 S, DCN-S exhibited high sensitivity (88 nM detection limit) and large stokes shift (155 nm). Importantly, the probe also was successfully used for endogenous and exogenous imaging of living cells. [ABSTRACT FROM AUTHOR]

Highlights • A label-free impedimetric immunosensor based on poly (pyrrole-co-pyrrole-1-propionic acid) and reduced graphene oxide polymer was developed. • The pyrrole-based copolymer strengthen sensor conductivity and provide binding sites of antibody for capturing target. • The impedimetric immunosensor exhibits good selectivity and sensitivity towards melamine. Abstract A label-free electrochemical impedimetric immunosensor was developed to monitor melamine, and it was successfully applied for the detection of melamine in spiked dairy samples. The poly (pyrrole-co-pyrrole-1-propionic acid) and reduced graphene oxide polymer layer (rGO-PPYPPA) were co-electrodeposited on the electrode using a one-pot method, thus obtaining a copolymer layer with favorable electrochemical properties. A competitive immunoassay was used for quantitative analysis of melamine. The rGO-PPYPPA copolymer improved the conductivity of the sensor and provided adequate anchor sites for antibody binding, thus enhancing immuno-binding. The specific immune-interactions at the electrode surface that restrict the electron transfer of the redox probe Fe(CN) 6 3−/4− lead to changes in electrochemical impedance, and the changes in impedance correlated to specific concentrations of melamine. The immunosensor displays a wide detection range (10−11−10−2 mol L−1), low limit of detection (1.2 × 10−11 mol L−1) and acceptable recovery (84.6%–100.3%) in real samples. The results provide a simple and versatile impedimetric immunosensing platform, with great potential for real-world applications. [ABSTRACT FROM AUTHOR]

A novel 24-site fluidic micro-array screen printing electrochemical analytical device based on double-deck slide construction and assembled micro-reservoir was fabricated for multiplex and coinstantaneous immunosensing. The mesoporous bimetallic Au@Pt nanoparticles was involved as signal-trigger for effective analysis of typical harmful substances - enrofloxacin (veterinary drug) and melamine (illegal additive) that might exist in one sample. The results revealed this strategy not only supported multi-channel and high-throughout assay but also assisted micro-fluidic detection without crosstalk and interference. The approach displayed a wide linear range (ENR: 0.1–1000 ng mL -1 , MEL: 0.1–500 ng mL -1 ), satisfactory limit of detection (ENR: 18.97 pg mL -1 , MEL: 26.80 pg mL -1 , S/N = 3) and acceptable recovery (ENR: 90.18%–100.76%, MEL: 91.34%–108.81%) in practical sample. Furthermore, the immunosensor showed high specificity for each target, favorable stability for long-term storage and satisfactory reproducibility for several repeated detection. The proposed disposable and versatile analytical platform lends a fresh perspective to further application in the portable analysis of multi-targets and large-amount samples. [ABSTRACT FROM AUTHOR]

• Based 'successive' nucleophilic substitution high selective H 2 S detection was realized. • The probe can target mitochondrial-H 2 S with red light emissive fluorescent. • The probe successfully was applied imaging in living HeLa cells and mice. The research of endogenous hydrogen sulfide (H 2 S) biology function, pathological and pharmacological effects has been active in the field of chemists and biologists in recent years. Especially, consequent H 2 S detection mechanisms and biological applications based on fluorescence probe emerged in endlessly, competing ideas, each had its advantage. In facts, the reaction mechanism and luminescence properties play a decisive role in the biology application of H 2 S fluorescence probe. In this despite booming season, in the process of research we still skillfully conceived, in view of H 2 S with small structure being able to do successive nucleophilic substitution in the same molecules, high selective H 2 S subcellular detection was realized. Specifically, we take the cyanine (Cy7) with positive charge as a red fluorophore, through the introduction of disulfide bond and carbonate to build the specific reaction sites of H 2 S, thus avoiding the interference of other sulfur-containing substances in biological systems. After reaction with H 2 S, the Probe released red fluorophore, realizing mitochondria target H 2 S detection. Because the advantages of red fluorescence emission probe, the Probe successfully was applied imaging in mice. [ABSTRACT FROM AUTHOR]

• A QCM sensor based on AuNPs doped molecularly imprinted layer and COFs-AuNPs composite was developed. • The sensitive and selective detection was attributed to the employment of COFs-AuNPs and crosslinked imprinting recognition sites. • The COFs-AuNPs composite and three-dimensional structure of imprinted matrix provided more recognition sites for sensing. In this study, for the first time a quartz crystal microbalance (QCM) sensor based on gold nanoparticles (AuNPs) doped molecularly imprinted layer and covalent organic frameworks composite (COFs-AuNPs) was developed for the detection of aflatoxin B1. The AuNPs doped molecularly imprinted layer involved in the crosslinking of o- aminothiophenol functionalized AuNPs (o- ATP@AuNPs) in the present of the templates on electrode surface. The imprinting recognition sites obtained by eluting the templates from imprinted polymer of poly(o- ATP) with AuNPs formed the specific three-dimensional imprinted contours toward the targets. A kind of porous lightweight material–CTpBD COFs and AuNPs were employed jointly to yield the COFs-AuNPs composite which provided large surface area for o- ATP@AuNPs crosslinking. The introduction of COFs-AuNPs substrate and three-dimensional structure of imprinted matrix endowed the sensor with more recognition sites. The sensitive and selective detection was attributed to the loading capacity of the COFs-AuNPs composite and the specific recognition effect of molecularly imprinted polymer of poly(o- ATP) with AuNPs. Under optimal conditions, the proposed sensor showed a wide linear range from 0.05 to 75 ng mL−1, low limit of detection (LOD = 2.8 pg mL−1) and the acceptable recoveries (87.0%−101.7%) in real samples analysis. [ABSTRACT FROM AUTHOR]

[Display omitted] • A label-free Immune-co-Chemical ECL-sensor based on poly(DVB-Co-PBA) and high luminous-efficiency Ti,Mg@N-CDs was developed. • The Ti,Mg@N-CDs-based ECL-reagent enhanced biosensor signal and provide binding sites of antibody for capturing target. • The dual-recognition Immune-co-Chemical ternary-system exhibits good selectivity and sensitivity towards AFP. • By changing AFP recognition unit, this method can be extended to determination of other disease biomarkers. In this paper, a high-efficiency electrochemiluminescence (ECL) ternary immune-system was firstly constructed for ultrasensitive assay of alpha-fetoprotein (AFP) based on the Ti, N/Mg co-doped carbon dots (Ti,Mg@N-CDs) as brand-new nanocomposite emitter, Poly(DVB-Co-PBA) as novel AFP-signal reporter and coreaction accelerator. A fluorescent microspheres Poly(DVB-Co-PBA), synthesizing based on 4-vinylphenylboronic acid (4-MPBA) and divinylbenzene (DVB), was used as a signal indicator-probe via the specific carbohydrate-AFP interaction to fabricate a dual-recognition label-free immune-co-chemical biosensor. The as-prepared Ti,Mg@N-CDs exhibited high ECL emission of 3.7-folds compared with CDs. Moreover, the large surface area, promising biocompatibility and nitrogen-rich functional group bearing on the nanohybrid was helpful for the antibody adsorption immobilization of Anti AFP /Ti,Mg@N-CDs/GCE. The successful synthesis and enhancement mechanism of the nanomaterials were also characterized through a serious of techniques including HR-TEM, SEM, EDS, FT-IR, UV–vis, PL and CV. With an immune-co-chemical ECL-assay format, target and signal reporter-probe (Poly(DVB-Co-PBA)) were introduced in sequence via specific reaction. Based on multiple signal amplification and dual recognition strategy, a largely linear detection ranges from 2.25 × 10−6 to 2250 ng mL-1 with a low detection limit (1.55 × 10-7 ng mL-1) were obtained via the resultant ECL ternary (Poly(DVB-Co-PBA)-AFP/Anti AFP /Ti,Mg@N-CDs/GCE) system. This proposed new method was applied to detect human serum samples with satisfactory results and acceptable recovery (96.04 % ∼ 111.22 %), indicating a potential application in clinical monitoring of disease biomarkers. [ABSTRACT FROM AUTHOR]

• A novel substoichiometric photothermal conversion materials MoO3-x nanoparticles was first prepared. • A highly sensitive thermal immunosensor for the detection of pathogens E. coli O157:H7 was developed. • Semi-quantitatively detecting the E. coli O157:H7 by visual colorimetry. • Quantitatively detecting the E. coli O157:H7 by infrared thermal imaging under 808 nm laser with infrared camera. A novel substoichiometric photothermal conversion materials MoO 3-x nanoparticles (4-MBA MoO 3-x NPs) was first prepared by 4-mercaptobenzoic acid modified based on the oxygen vacancy defects of molybdenum oxide and used to develop a thermal immunosensor for the detection of pathogens E. coli O157:H7. 4-mercaptobenzoic acid (4-MBA) being selected as the reducing agent functionalized surface modifier to prepare 4-MBA MoO 3-x NPs, which was an excellent photothermal conversion materials and had 42.9 % photothermal conversion efficiency under 808 nm laser. Photothermal sensor probes prepared by 4-MBA-MoO 3-x NPs being coupled with antibodies was used to develop the immunoassay for the detection of E. coli O157:H7 by means of immunomagnetic separation technology. The method could be used for semi-quantitative and quantitative determine of the E. coli O157:H7 by visual colorimetry and infrared thermal imaging. For the quantitative determination, the E. coli O157:H7 was quantified by recording the temperature response of the target bacteria combined with the nanomaterial under 808 nm laser with infrared camera. Under the optimal conditions, the low limit of detection (LOD) of the method was 14 CFU/mL with a linearity range of 1.4 × 101-1.4 × 106 CFU/mL, and the recoveries was 82.45 %−105.08 % in real samples analysis. [ABSTRACT FROM AUTHOR]

• An integrated dual-signal aptasensor was constructed for point-of-use tests. • A naked-eye colorimetric unit and an electrochemical unit were covered in the dual-signal aptasensor. • A miniaturized workstation coupled with a home-made magneto-detection module was used for electrochemical measurements. • This versatile strategy is promising to be extended to the fast screening of other targets by using appropriate aptamers. A novel dual-signal sensing system was developed for on-site analysis. A custom-built miniaturized workstation coupled with a home-made magneto-electrochemical detection module was employed for electrochemical sensing. The miniaturized workstation could be controlled by smartphone and all devices and tools in this integrated dual-signal biosensing platform were portable, which applies to on-site analysis. Meanwhile, by simple separation, color responses could be captured by naked-eye observation to detect target even in the absence of any instrument. The differences in target amounts were converted into the color change of AuNPs dispersion and the current change on solid electrode. A particularly objective in developing such versatile dual-signal strategy is to offer an user-friendly, portable, time-saving and cost-effective analysis strategy. The feasibility of the naked-eye colorimetric/magneto-electrochemical biosensing strategy was exemplified by using ATP and Hg2+ as model target. The LOD of two targets in electrochemical unit were 5.203 pmol L−1 and 1.597 pmol L−1 (S/N = 3), respectively. More importantly, the versatile dual-signal platform possesses favorable extensibility and could realize on-demand fast screening of other targets by using appropriate aptamers. [ABSTRACT FROM AUTHOR]

• An universal fluorescent encoding strategy was presented. • The encoding process was compatible for different polarity of quantum dots. • Five single-color and 10 dual-color fluorescent systems were obtained. • The fluorescent MIPs performed excellent specific adsorption for dopamine in PBS. • Dual mode fluorescent sensors were successful applied for dopamine detection. As the promising analytical strategy, multi-mode quantum dots (QDs) encoded molecularly imprinted fluorescent sensors have attracted considerable attention. Here, a novel encoding strategy for water-dispersed QDs molecularly imprinted polymers microspheres (MIPMs) with a high-performance fluorescence intensity and multi-color signal was established. The water-compatible MIPMs were firstly synthesized via integrating the reversible addition-fragmentation chain transfer and precipitation polymerization (RAFT-PP), which could improve the water compatibility by grafting the hydrophilic groups of poly(2-hydroxyrthyl methacrylate) (PHEMA). Then the water-compatible MIPMs were used as embedding matrix to separately incorporate with five different QDs, and a series of multi-color QDs encoded MIPs (five single-color and 10 dual-color fluorescent systems) were obtained. The fluorescent characterization of encoded MIPMs was studied in detail. Further, dual-mode fluorescence systems were fabricated as fluorescence sensors for the quantitative detection of dopamine; good linear response in the range of 5-300 μg L-1 and 1-100 μg L-1 and the limit of detection (LOD) with 2 μg L-1 and 0.5 μg L-1 were obtained for monochromatic and ratiometric sensor, respectively. It is the first time to introduce the optical encoding strategy into the fabrication of fluorescent MIPs, which not only greatly simplifies the preparation process of fluorescent imprinted sensor, but also provides more alternatives for the detection method of analyte and the potential of high-throughput multiple analytes at one time. [ABSTRACT FROM AUTHOR]