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Nanoplastics, widely existing in the environment and organisms, have been proven to cross the blood-brain barrier, increasing the incidence of neurodegenerative diseases like Alzheimer's disease (AD). However, current studies mainly focus on the neurotoxicity of nanoplastics themselves, neglecting their synergistic effects with other biomolecules and the resulting neurotoxicity. Amyloid β peptide (Aβ), which triggers neurotoxicity through its self-aggregation, is the paramount pathogenic protein in AD. Here, employing polystyrene nanoparticles (PS) as a model for nanoplastics, we reveal that 100 pM PS nanoparticles significantly accelerate the nucleation rate of two Aβ subtypes (Aβ 40 and Aβ 42 ) at low concentrations, promoting the formation of more Aβ oligomers and leading to evident neurotoxicity. The hydrophobic surface of PS facilitates the interaction of hydrophobic fragments between Aβ monomers, responsible for the augmented neurotoxicity. This work provides consequential insights into the modulatory impact of low-dose PS on Aβ aggregation and the ensuing neurotoxicity, presenting a valuable foundation for future research on the intricate interplay between environmental toxins and brain diseases., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

A bovine serum albumin (BSA)-assisted ultrasonication strategy was developed for the synthesis of CsPbBr 3 nanocrystals (NCs) with stable fluorescence properties in aqueous solution. Such a preparation method is simple, fast and does not require complex equipment. The results show that the synthesized CsPbBr 3 NCs are homogeneous in particle size and have good solubility and stability in water. The CsPbBr 3 NCs have been utilized as fluorescence probe for rapid detection of hydrogen sulfide (H 2 S) in human serum. The reaction of H 2 S with the lead sites on the surface of CsPbBr 3 NCs produces lead sulfide (PbS), resulting in the decrease of fluorometric intensity of CsPbBr 3 NCs. Our designed fluorescent assay has a linear S 2- detecting range of 10 ~ 800 nM with a detection limit of 7.05 nM. The assay was used to determine H 2 S in human serum with spiked recoveries ranging from 94.98% to 102.69%. This work opens new avenues for the application of halide lead perovskite in different biosensing areas., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

A sandwiched photoelectrochemical (PEC) sensor was developed for sensitive detection of human epidermal growth factor receptor 2 (HER2) based on BiVO 4 -Bi 2 S 3 heterojunction as the photoelectric material accompanied with magnetic nanoparticles for enrichment of HER2 and CdS for signal amplification. The in situ generation of Bi 2 S 3 on the surface of BiVO 4 forming a BiVO 4 -Bi 2 S 3 heterojunction is more conducive to the transit of electron-hole pairs. Antibody-modified MNs are utilized to capture and separate HER2 from samples. After forming a sandwich immune structure, under illumination, the photocurrent shows an increasing trend with the increment of HER2 concentration. The PEC immunosensor displays a good linear concentration range between 1.00 and 1.00 × 10 3  pg·mL -1 and a low limit of detection down to 0.680 pg·mL -1 (S/N = 3) for HER2 under a bias voltage of 0.1 V (vs. Ag/AgCl electrode). Furthermore, the sensor was successfully applied to detect HER2 in serum samples with recoveries that ranged between 96.1 and 114% with RSDs between 1.3 and 5.9%., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

In this work, we developed a photoelectrochemical assay for circulating tumor cells (CTCs) detection based on hexagonal carbon-nitrogen tubes (HCNT) as visible light-sensitive materials. The MCF-7 cell was selected as the model CTC and was captured through specific recognition between epithelial cell adhesion molecules (EpCAM) on the cell surface and anti-EpCAM antibodies. Anti-EpCAM antibody-modified magnetic nanoparticles were used to enrich and separate MCF-7 cells from samples. The detection signal was amplified by Ag 2 S nanocrystals, which can compete with HCNTs for absorbing visible light, leading to a decrease of photocurrent intensity. The linear range of the assay for MCF-7 cells is from 10 to 5000 cells mL -1 , with a detection limit of 3 cells mL -1 (S/D = 3). The assay has good selectivity for MCF-7 detection over HeLa cells. The assay was successfully applied for the detection of MCF-7 in human whole blood, which indicates the potential for clinical application., (© 2021. Springer-Verlag GmbH Germany, part of Springer Nature.)

Hydroxyapatite nanoparticles (HAP-NPs) were rendered fluorescence by doping with Eu(III) ion. The resulting fluorescent NPs are shown to be viable probes for sensitive and selective determination of dipicolinic acid (DPA), a major constituent of bacterial spores as used in bioterrorism. It is found that the addition of DPA to solutions of such HAP-NPs result in an enhancement of fluorescence due to the coordination of DPA with the Eu(III) dopant. The assay allows DPA to be detected in the 0.1 to 40 μM concentration range and with a 77 nM detection limit. The assay was applied to the detection of spores of Bacillus subtilis. The attractive properties of the probe make it a promising candidate for used in rapid detection of pathogenic bacterial spores. Graphical abstract Fluorescent hydroxyapatite nanoparticles (HAP-NPs) are shown to be a viable probe for detection of dipicolinic acid, a major constituent of bacterial spores. The red asterisks represent the fluorescence intensity of the HAP-NPs.

Fluorescent hydroxyapatite nanoparticles (HAP-NPs) were prepared by reacting calcium ion with phosphate in the presence of Eu(III) ion. The HAP-NPs display large Stokes' shift and two strong fluorescence emissions with peaks at 590 nm and 615 nm when excited at 250 nm. The HAP-NPs also have good photostability and water solubility. The HAP-NPs combined with Cu(II) were applied to fluorometric determination of cysteine and homocysteine in biological samples and in living cells. In this detection scheme, the fluorescence of HAP-NPs is initially quenched by Cu(II). The addition of biothiols results in the formation of Cu(II)-thiol complexes and leads to fluorescence recovery. The assay allows cysteine to be detected with a 110 nM detection limit, and homocysteine with a 160 nM detection limit. The assay was successfully applied to the analysis of cysteine in spiked human serum samples and to imaging of cysteine in HeLa cells, and this demonstrates its potential for clinical testing and in biomedical research. Graphical abstract Fluorescent hydroxyapatite nanoparticles were synthesized and combined with Cu 2+ for fluorescence sensing of biothiols (cysteine and homocysteine) in complex biological samples and in living cells.

The authors describe a fluorometric method for the determination of the activity and inhibition of protein kinase A (PKA). In the presence of ATP, PKA catalyzes the transfer of phosphate groups from ATP to a peptide, and the generated phosphorylated peptide quenches the fluorescence (measured at excitation/emission peaks of 340/440 nm) of the hydroxyapatite nanoparticles (HAP-NPs). A linear logarithmic relationship of PKA concentrations with fluorescence intensity in the range from 1 to 50 U·L -1 was obtained, and the lower limit of detection (LOD) is 0.5 U·L -1 . This is much lower than LODs reported in the literature. The PKA inhibitor H-89 was studied, and the inhibition plot has a sigmoidal shape with a half-maximal inhibitory concentration of around 750 nM of H-89. At a 4.5 nM level of H-89, fluorescence of HAP-NPs fell to levels of no PKA controls, demonstrating that the assay is a viable tool to screen for kinase inhibitors. An assay with Hela cell lysates in combination with forskolin (an activator of adenylyl cyclase) and IBMX (a phosphodiesterase inhibitor used to activate the cellular activity of PKA) resulted in decreased fluorescence of HAP-NPs. This suggests that the assay can be applied for testing in vitro cell kinase activity. In our perception, this method will enable high-throughput screening for kinase-related drugs and fluorometric enzymatic detection in various areas. Graphical abstract Fluorescence assay based on hydroxyapatite nanoparticles (HAP) fluorescence quenching was developed for analysis of the activity and inhibition of protein kinase A (PKA).

The protease BACE1 (the β-site amyloid precursor protein cleaving enzyme 1) catalyzes the first step in the synthesis of β-amyloids (Aβ), peptides that accumulate in the brain in Alzheimer's disease (AD). Measurement of BACE1 activity is important for the development of BACE1 inhibitors to slow or stop AD. To measure BACE1 cleavage of the electrode-immobilized substrate peptide, we developed a redox-generating hydroxyapatite (HAP) probe which generates electrochemical current by reaction of the nanoparticle with molybdate (MoO 4 ). The probe combines alkaline phosphatase (ALP) for dual signal amplification and Aβ antibody to bind the probe to the immobilized peptide substrate on the surface of the electrode. We measured the activity of BACE1 at concentrations ranging from 0.25 to 100 U/mL. The use of the dual-signal HAP-ALP probe increased the signal by an order of magnitude compared to HAP-only probe, enabling detection limits as low as 0.1 U/mL. To measure the inhibition of BACE1 activity, the BACE1 inhibitor OM99-2 was added to 25 U/mL of BACE1 in concentrations ranging from 5 to 150 nM. The observed detection limit of inhibition is 10 nM of OM99-2. These results demonstrate the capabilities of this novel biosensor to measure BACE1 activity and inhibitors of BACE1 activity. To the best of our knowledge this is the first report that reaction of HAP nanoparticles with molybdate can generate electrochemical current. This dual signal amplification strategy can be extended to other electrochemical assays and adapted for wide applications.2- ). The probe combines alkaline phosphatase (ALP) for dual signal amplification and Aβ antibody to bind the probe to the immobilized peptide substrate on the surface of the electrode. We measured the activity of BACE1 at concentrations ranging from 0.25 to 100 U/mL. The use of the dual-signal HAP-ALP probe increased the signal by an order of magnitude compared to HAP-only probe, enabling detection limits as low as 0.1 U/mL. To measure the inhibition of BACE1 activity, the BACE1 inhibitor OM99-2 was added to 25 U/mL of BACE1 in concentrations ranging from 5 to 150 nM. The observed detection limit of inhibition is 10 nM of OM99-2. These results demonstrate the capabilities of this novel biosensor to measure BACE1 activity and inhibitors of BACE1 activity. To the best of our knowledge this is the first report that reaction of HAP nanoparticles with molybdate can generate electrochemical current. This dual signal amplification strategy can be extended to other electrochemical assays and adapted for wide applications.

A novel electrochemical aptasensor involving quantum dots-coated silica nanospheres (QDs/Si) and the screen-printed gold electrodes (SPGE) was developed for the detection of thrombin. The screen-printed electrodes with several advantages, including low cost, versatility, miniaturization, and mechanical regeneration after each measurement cycle, were employed. On the other hand, the gold nanoparticles (AuNPs) were electrodeposited on the surface of SPGE to obtain AuNPs/SPGE. And this sandwich format (Apt/thrombin/Apt-QDs/Si) was fixed on the AuNPs/SPGE to fabricate the electrochemical aptasensor. The bound CdTe QDs were dissolved in an acid-dissolution step and were detected by electrochemical stripping analysis. The proposed aptasensor has excellent performance such as high sensitivity, good selectivity and analytical application in real samples. The combination of nanoparticles with the screen-printed electrode is favorable for amplifying electrochemical signals, and useful for large-scale fabrication of the electrochemical aptasensors, which would lay a potential foundation for the development of the electrochemical aptasensor., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Ultrasensitive sandwich type electrochemical immunosensors for the detection of cancer biomarker prostate specific antigen (PSA) is described which uses graphene sheet (GS) sensor platform and ferrocene functionalized iron oxide (Fe(3)O(4)) as label. To fabricate the labels, dopamine (DA) was first anchored onto Fe(3)O(4) surface followed by conjugating ferrocene monocarboxylic acid (FC) and secondary-antibody (Ab(2)) onto Fe(3)O(4) through the amino groups of DA (DA-Fe(3)O(4)-FC-Ab(2)). The great amount of DA molecules anchored onto Fe(3)O(4) surface increased the immobilization of FC and Ab(2) onto the Fe(3)O(4) nanoparticle, which in turn increased the sensitivity of the immunosensor. GS used as biosensor platform increased the surface area to capture a great amount of primary antibodies (Ab(1)) and the good conductivity of GS enhanced the detection sensitivity to FC. Using the redox current of FC as signal, the immunosensor displays high sensitivity, wide linear range (0.01-40 ng/mL), low detection limit (2 pg/mL), good reproducibility and stability. In addition, this method could be extended to the immobilization of other interesting materials (fluorescence dyes) onto Fe(3)O(4) for preparing various kinds of labels to meet the different requirements in immunoassays., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Norethisterone is one kind of widely used anabolic steroid hormones which can help to promote livestock growth and sometime has been illegally used for livestock breeding. The residues of norethisterone in animal food will harm people's health, therefore, it has been banned to use for the growth promotion purposes in livestock. In this study, amino-group functionalized mesoporous silica nanoparticles (MSN) were prepared and used to immobilize Au nanoparticles, which was further utilized for the adsorption of horseradish peroxidase (HRP) and the secondary antibody (Ab2). The resulting nanoparticles, Au-MSN-HRP-Ab2 were used as labels for immunosensors to detect norethisterone antigen. A sandwich-type protocol was used to prepare the immunosensor with the primary antibody (Ab1) immobilized onto thionine (TH) and graphene sheet (GS) modified glassy carbon electrode surface. The sensitivity of the sandwich-type immunosensor using Au-MSN-HRP-Ab2 as labels for norethisterone antigen detection was much higher than that using either Au-MSN-Ab2 or MSN-HRP-Ab2 as labels. Within norethisterone concentration range (0.01-10 ng/mL), a linear calibration plot (Y=0.55671+8.27101X, r=0.9993) was obtained with a detection limit of 3.58 pg/mL under optimal conditions. The proposed immunosensor shows good reproducibility, selectivity, and acceptable stability. This new type of labels for immunosensors may provide many potential applications for the detection of growth hormone in animal derived food., (Copyright © 2010 Elsevier B.V. All rights reserved.)

A class of immuno-labels based on poly(ethylene glycol)-poly(lactic acid) (PEG-PLA) polymeric vesicles was developed in this study. To fabricate these immune-labels, the uniform Fe(3)O(4) nanoparticles (NPs) were loaded into the vesicles followed by conjugating secondary antibody (Ab(2)) onto the vesicles surface, named Ab(2)-PEG-PLA-Fe(3)O(4). The resulting Ab(2)-PEG-PLA-Fe(3)O(4) demonstrated high catalytic activity towards H(2)O(2), and the sensitivity of the sandwich-type immunosensor using this label for prostate specific antigen (PSA) detection increased greatly. The immunosensor based on this label exhibited high sensitivity, wide linear range (0.005-10 ng/mL), low detection limit (2 pg/mL), good reproducibility, selectivity and stability. These labels for immunosensors may provide many potential applications for the ultrasensitive detection of different cancer biomarkers. In addition, this technique also has the potential to be extended to the loading of other interesting material for preparing various kinds of labels to meet the different requirements in immunoassays.

Labels based on mesoporous silica nanoparticles (MSN) loaded with mediator thionine (TH), enzyme horseradish peroxidase (HRP) and secondary anti-human IgG antibody (Ab(2)) were developed in order to improve the sensitivity and detection limit of an amperometric immunosensor. The sensitivity of the sandwich-type immunosensor using MSN-TH-HRP-Ab(2) as labels for human IgG detection was about 100 times higher than that using either MSN-TH-Ab(2) or MSN-HRP-Ab(2) as labels, indicating the high catalytic efficiency of HRP in the presence of mediator TH toward H(2)O(2). The immunosensor using MSN-TH-Ab(2) as labels exhibited a high sensitivity and showed a linear response within the range of 0.01-10 ng/mL human IgG. It also showed good reproducibility and selectivity and acceptable stability. These labels for immunosensors may provide many potential applications for the detection of different biomolecules., (Copyright 2010 Elsevier Ltd. All rights reserved.)

A simple approach is proposed for the synthesis of cobalt hexacyanoferrate nanoparticles (CoNPs) with uniform shape and size controlled by ethylene diamine tetraacetic acid (EDTA) as a stabilizer. A sensitive amperometric biosensor for insulin has been prepared using glassy carbon electrodes by solubilization of carbon nanotubes (CNTs) in chitosan (CHIT) together with CoNPs synthesized by the new methodology. The CoNP-CNT-CHIT organic-inorganic system exerts a synergistic effect, resulting in the remarkably enhanced insulin currents owing to the superior electron-transfer ability of CNTs and the excellent reversible redox centers of CoNPs. High-resolution transmission electron microscopy (HRTEM) was used to provide closer inspection of the CoNPs. The effects of alkali metal cations and the concentrations of CNTs and CoNPs on the voltammetric behavior of the film-modified electrode were also investigated. In pH 6.98 phosphate buffer (PB) at +0.7 V (vs. SCE) the insulin biosensor exhibits a linear response range of 0.1-3 microM with a correlation coefficient of 0.98, and the detection limit (S/N=3) is determined to be 40 nM, the stability of the biosensor was tested and found satisfactory. There is great promise for in vivo measurements of this important hormone.

Semiconducting metal oxides (SMOXs) are used widely for gas sensors. However, the effect of ambient humidity on the baseline and sensitivity of the chemiresistors is still a largely unsolved problem, reducing sensor accuracy and causing complications for sensor calibrations. Presented here is a general strategy to overcome water‐sensitivity issues by coating SMOXs with a hydrophobic polymer separated by a metal–organic framework (MOF) layer that preserves the SMOX surface and serves a gas‐selective function. Sensor devices using these nanoparticles display near‐constant responses even when humidity is varied across a wide range [0–90 % relative humidity (RH)]. Furthermore, the sensor delivers notable performance below 20 % RH whereas other water‐resistance strategies typically fail. Selectivity enhancement and humidity‐independent sensitivity are concomitantly achieved using this approach. The reported tandem coating strategy is expected to be relevant for a wide range of SMOXs, leading to a new generation of gas sensors with excellent humidity‐resistant performance. [ABSTRACT FROM AUTHOR]

Electrocatalysis is an efficient and promising means of energy conversion, with minimal environmental footprint. To enhance reaction rates, catalysts are required to minimize overpotential. Alternatives to noble metal electrocatalysts are essential to address these needs on a large scale. In this context, transition metal nitride (TMN) nanoparticles have attracted much attention owing to their high catalytic activity, distinctive electronic structures, and enhanced surface morphologies. Nickel‐based materials are an ideal choice for electrocatalysts given nickel's abundance and low cost in comparison to noble metals. In this Minireview, advancements made specifically in Ni‐based binary and ternary TMNs as electrocatalysts for the oxygen evolution reaction (OER) are critically evaluated. When used as OER electrocatalysts, Ni‐based nanomaterials with 3 D architectures on a suitable support (e.g. a foam support) speed up electron transfer as a result of well‐oriented crystal structures and also assist intermediate diffusion, during reaction, of evolved gases. 2 D Ni‐based nitride sheet materials synthesized without supports usually perform better than 3 D supported electrocatalysts. The focus of this Minireview is a systematic description of OER activity for state‐of‐the‐art Ni‐based nitrides as nanostructured electrocatalysts. [ABSTRACT FROM AUTHOR]

Transition metal nitride and carbide have several similarities in their preparatory methods, properties, and applications. Synthetic parameters have remained the main factors that determine the effectiveness of nitrides and carbides in electrochemical storage devices, photocatalysis, environmental remediation, gas sensing and medicinal agents. This review addresses aspects of relevance to electronic structure and chemical bonding, and recent advances made in the synthesis approaches. The syntheses approaches that are particularly relevant for reducing (i) production cost, (ii) energy consumption, and (iii) synthesis time for these materials systems are discussed in detail. Furthermore some of the recent techniques like solid-solid state separation, carbothermal, gas-phase, electrochemical, sonochemical, solvothermal, sol-gel reaction and solid state reaction that offer new avenues for researchers (including a sustainability-oriented exploration) are mentioned. We discuss synthetically tunable properties (morphology, electronic characteristics, energy storage capacity, corrosion resistance, catalytic ability and gas sensing properties), heat treatment aspects, and relevant applications of these systems. We expect this review to be useful to the ever growing community of researchers that are interested in nitrides and carbides, and their applications. [ABSTRACT FROM AUTHOR]

Abstract: A new strategy is proposed to fabricate adaptable protein‐based hydrogel networks with both injectable and self‐healable properties. By mixing proteins and metal ions under alkaline conditions, the metal ions can crosslink proteins into protein–metal ion dynamic networks. Subsequently, the metal ions can react with the cysteine residues of protein to in situ form corresponding metal sulfide NPs with ultra‐small size, which leads to nanocomposite hydrogels with adaptable structures. This approach is general and a series of metal sulfide NP in situ embedded nanocomposite hydrogels were obtained. As an example, a Bi2S3–BSA hydrogel with tunable networks is shown to serve as an injectable, self‐healable photothermal agent for the treatment of tumors. Our finding paves a new avenue for the preparation of injectable and self‐healable hydrogels with potential applications in biomedicine. [ABSTRACT FROM AUTHOR]

The authors describe a dual signal amplification strategy for improving the sensitivity of electrochemical aptasensor. Hydroxyapatite nanoparticles (HAP-NPs) serve as the support for deposition of the respective aptamer. Both the HAP-NPs and the aptamer contain phosphate groups which can react with molybdate to form a redox-active molybdophosphate precipitate on the surface of a glassy carbon electrode (GCE). On applying a relatively low voltage of 0.21 V (vs. Ag/AgCl), a current is generated whose intensity depends on the concentration of the analyte. The cancer biomarker platelet-derived growth factor BB (PDGF-BB) is chosen as a model antigen (analyte). The assay works by sequential deposition of antibody against PDGF-BB, analyte (PDGF-BB) and anti-PDGF-BB aptamer modified HAP-NPs on the GCE to form a sandwich structure. The amperometric signal is linear in the 0.1 pg.mL to 10 ng.mL PDGF-BB concentration range, with a detection limit as low as 50 fg.mL. The assay was successfully applied to the determination of PDGF-BB in serum samples. In our perception, this signal amplification strategy has a wide scope in that it can be adapted to the preparation of other aptasensors for biomarkers and related species. [ABSTRACT FROM AUTHOR]

The authors describe a strategy for improving the sensitivity of electrochemical immunoassays that is based on the use of hydroxyapatite nanoparticles (HAP-NPs). Signal generation is based on the reaction of phosphate groups present in HAP-NPs with molybdate to form a redox-active molybdophosphate precipitate on the surface of the electrode that facilitates the generation of an electrochemical current. The cancer biomarker α-fetoprotein (AFP) was chosen as a model antigen (analyte). Antibodies against AFP (Ab) were immobilized on the HAP-NPs to obtain the signal probe. The reaction of HAP-NPs with molybdate and the performance of the immunoelectrode were characterized in detail. Based on this signal amplification approach, an immunoassay was worked out that has a linear range that extends from 0.1 pg·mL to 1 ng·mL and a detection limit as low as 50 fg·mL. The assay was successfully applied to the determination of AFP in serum samples. In our perception, this new signal amplification scheme can be adapted to numerous other immunoassays. [ABSTRACT FROM AUTHOR]

• Biosensor based on Pt nanoparticles modified MXene is developed for analysis of pyruvate. • Pyruvate oxidase oxidizes pyruvate to produce H 2 O 2. • H 2 O 2 was detected by PtNPs-modified MXene to generate electrochemical signals. • The sensor was applied for determination of pyruvate in human serum. In this study, we developed a biosensor based on Pt nanoparticles (PtNPs) modified 2D MXene for sensitive analysis of pyruvate in human serum. The pyruvate oxidase oxidizes pyruvate to produce H 2 O 2 , which is catalyzed by PtNPs-modified MXene, generating electrochemical signals for pyruvate detection, with a linear range of 10–1000 μM and a detection limit of 0.7 μM. The practical application of the sensor was verified by the determination of pyruvate in human serum. The utilization of MXene as biosensing materials may find wide application in the design of different biosensors. [ABSTRACT FROM AUTHOR]

Abstract: A facile method for the preparation of ferrocene (FC) loaded porous polyelectrolyte nanoparticles (FC-PPN) using CaCO3 as template was reported. Polyelectrolyte, ferrocene and CaCO3 nanoparticles were dispersed in ethanol/water solution. After the evaporation of solution under stirring, the FC-PPN was prepared with the polyelectrolyte layer adsorbed onto CaCO3 surface during the solution evaporation process, and FC encapsulated within the polyelectrolyte framework. The resulted FC-PPN showed high FC loading and good stability. Sensitive electrochemical immunosensor for the detection of oral cancer biomarker interleukin-6 (IL-6) using this FC-PPN as label was prepared. Using the redox current of FC as signal, the immunosensor displays high sensitivity, wide linear range (0.002–20ng/mL), low detection limit (1pg/mL) and good reproducibility. In addition, this porous nanoparticle preparation method could be extended to the incorporation of different interesting materials onto nanoparticles and find wide applications in various areas, such as bioassay, drug delivery and catalysis. [Copyright &y& Elsevier]

Abstract: Platinum nanoparticles (PtNPs) were prepared by seed-mediated growth method with Au nanoparticles (AuNPs) playing the role of seeds. Carbon nanotubes (CNTs) and AuNPs were first dropped onto the surface of glassy carbon (GC) electrode, and then the electrode was immersed into growth solution which contains H2PtCl6 and ascorbic acid. PtNPs were successfully grown onto the CNT surface due to the chemical reduction of Pt(IV). The electrode modified with AuNPseed/PtNP/CNT film displayed excellent electrochemical response to H2O2 at 0.45V versus saturated calomel electrode (SCE) with sensitivity much larger than that of PtNP/CNT and AuNPseed/PtNP modified electrodes. Glucose oxidase was selected as a model enzyme and electrodeposited onto the AuNPseed/PtNP/CNT modified electrode in the presence of a detergent. The resulting biosensor enabled selective determination of glucose with high sensitivity of 4.49μAmM−1, quick response time about 2s, low-detection limit of 0.5μM and wide linear range from 1μM to 4mM with a correlation coefficient 0.9998. Thus, the modified electrode proved to be a nice electrochemical biosensing platform for the fabrication of oxidase-based biosensors. [Copyright &y& Elsevier]

Abstract: By exploring the properties of histidine, functional histidine/nickel hexacyanoferrate nanotube assembly was prepared using nanopore alumina template via a sequential deposition strategy and demonstrated for improved biosensing. The vertically oriented nanotube assembly has a nanotube density ∼8×108 cm−2 and can be stably attached to the glassy carbon electrode surface. The nanotube assembly formed provides an ordered well-defined three-dimensional (3D) structure with good electron transfer efficiency and a large specific surface area with abundant electroactive sites. Gold nanoparticles were then absorbed onto nanotube surfaces through amino group provided by histidine, and were used for further absorption of glucose oxidase into the 3D matrix. The histidine and gold nanoparticles on the nanotube surface provide a favorable microenvironment to keep the bioactivity of the enzymes with a low apparent Michaelis–Menten constant (K Mapp) of 2.15mm, and the ordered orientation of the nanotube assembly facilitated enzyme–substrate contact. The biosensor was sensitive and selective toward glucose with a linear range covered from 2μm to 20mm of glucose. The biosensor was used to determine glucose concentration in real blood samples with satisfactory results. [Copyright &y& Elsevier]

Abstract: The successful attachment of nickel hexacyanoferrate nanoparticles to carbon nanotubes through a simple, two-step procedure is reported. Histidine can be covalently linked to the carbon nanotube surface, which can then be used as interlinker for the binding of nickel hexacyanoferrate nanoparticles. A detailed investigation by Fourier transform infrared spectra (FT-IR), transmission electron microscopy, UV–vis and electrochemistry was performed in order to elucidate the preparation process and properties of the nanocomposites. Abundant nanoparticles were found attached onto the carbon nanotube surface and the nanocomposites are highly stable. Additionally, the nanostructure exhibits more efficient electron transfer ability and larger electrochemical response towards hydrogen peroxide as compared to the nanoparticles and carbon nanotubes physically mixed together. With the immobilization of cholesterol oxidase onto the nanostructure modified electrode surface, a biosensor that responds sensitively to cholesterol has been constructed. In pH 6.98 phosphate buffer, an almost interference free determination of cholesterol has been observed at −0.2V versus SCE with a linear range from 0.005 to 3mM and response time <20s. [Copyright &y& Elsevier]

Abstract: Cobalt hexacyanoferrate nanoparticles (CoNP) can be easily prepared by mixing hexacyanoferrate and cobalt chloride solution at room temperature. The nanoparticles were solubilized in aqueous solution of a biopolymer chitosan (CHIT). With the introduction of carbon nanotubes (CNT), the CoNP–CNT–CHIT system formed shows synergy between CNT and CoNP with the significant improvement of redox activity of CoNP due to the excellent electron-transfer ability of CNT. The CoNP–CNT–CHIT film modified glassy carbon electrode allows low potential detection of hydrogen peroxide with high sensitivity and fast response time. In particular, with the introduction of CNT, it amplified the H2O2 sensitivity by ∼70 times compared to film of CoNP–CHIT. With the immobilization of glucose oxidase onto the electrode surface using glutaric dialdehyde, a biosensor that responds sensitively to glucose has been constructed. In pH 6.98 phosphate buffer, interference free determination of glucose has been realized at −0.2V versus saturated calomel electrode (SCE) with a linear range from 0.01 to 10mM and response time <10s. The detection limit was 5μM glucose (S/N=3). [Copyright &y& Elsevier]

Abstract: Platinum nanoparticle-doped chitosan (CHIT) solution can be easily prepared by treating the CHIT solution with aqueous H2PtCl6 solution followed by chemical reduction of Pt(IV) with NaBH4. Multiwalled carbon nanotubes (MWCNT) are then dispersed in the nanoparticle-doped solution. The resulting Pt-CNT-CHIT material brings new capabilities for electrochemical devices by using the synergistic action of Pt nanaoparticles and CNT. Positively charged Pt-CNT-CHIT solution and negatively charged poly(sodium-p-styrenesulfonate) salt (PSS) have been employed to fabricate stable ultrathin multilayer films on gold electrode and quartz glass slides in a layer-by-layer fashion. Cyclic voltammetric and UV–vis adsorption spectroscopy confirms the consecutive growth of the multilayer films. The modified gold electrode allows low-potential detection of hydrogen peroxide with high sensitivity and fast response time. With the immobilization of cholesterol oxidase onto the electrode surface using glutaric dialdehyde, a biosensor that responds sensitively to cholesterol has been constructed. In pH 6.98 phosphate buffer, almost interference free determination of cholesterol has been realized at 0.1V vs. SCE with a linear range from 0.01 to 3mM and response time&#60;30s. With the immobilization of another cholesterol esterase enzyme layer, the biosensor was used to determine total cholesterol in serum samples with satisfactory results. [Copyright &y& Elsevier]

Abstract: Platinum nanoparticle-doped sol–gel solution is prepared and used as a binder for multi-walled carbon nanotubes (CNT) for the fabrication of electrochemical sensors. Amine group containing sol–gel solution is selected to utilize the affinity of –NH2 groups toward metal nanoparticles for stabilization the nanoparticles in solution. The resulting CNT-silicate material brings new capabilities for electrochemical devices by using the synergistic action of the electrocatalytic activity of Pt nanoparticles and CNT. The combined electrocatalytic activity permits low-potential detection of hydrogen peroxide with remarkably improved sensitivity. With the incorporation of glucose oxidase within the Pt-CNT-silicate matrix, a Pt-CNT paste-based biosensor has been constructed that responds more sensitively to glucose than CNT-based biosensor. The influences of the composite of the sol–gel solution, the quantity of the solution and the Pt nanoparticles loading are examined. In pH 6.98 phosphate buffer, almost interference free determination of glucose is realized at 0.1V versus SCE with a linear range from 1 to 25mM, a response time <15s, and the sensitivity is 0.98μAmM−1 cm−2. The sensitivity of the Pt-CNT paste-based biosensor is almost four times larger than that of the CNT-based biosensor (0.27μAmM−1 cm−2 at 0.1V). The improved electrocatalytic activity and surface renewability made the Pt-CNT-silicate system a potential platform to immobilize different enzymes for other bioelectrochemical applications. [Copyright &y& Elsevier]

This study reports on a simple approach for the fabrication of an electrode modified with biocompatible C-dot wrapped ZnO nanoparticles for selective photoelectrochemical monitoring of H2O2 released from living cells. The biocompatibility of the ZnO nanoparticles was confirmed through in-vitro cellular testing using the MTT assay on Huh7 cell lines. The ZnO nanoparticles wrapped with dopamine-derived C-dots possess numerous catalytically active sites, excessive surface defects, good electrical conductivity, and efficient separation ability of photo-induced electrons and holes. These properties offer highly sensitive and selective non-enzymatic photo-electrochemical monitoring of H2O2 released from HeLa cells after stimulation with N-formylmethionyl-leucyl-phenylalanine. The sensor has a wide linear range (20-800 nM), low detection limit (2.4 nM), and reliable reproducibility, this implying its suitability for biological and biomedical applications.Schematic of the fabrication of ZnO nanoparticles by using a plant extract as a reducing agent. Wrapping of ZnO with C-dots enhances the photoelectrocatalytic efficacy. Sensitive and selective photoelectrochemical monitoring of H2O2 released from cancer cells is demonstrated. [ABSTRACT FROM AUTHOR]

The intrinsic peroxidase-like activity of hollow Prussian Blue nanoparticle-loaded with gold nanoparticles (Au@HMPB NPs) were applied to oxidize the substrate 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of H2O2 to give a blue-green coloration. The morphology of the Au@HMPB NPs and its peroxidase-mimicking activity was characterized in detail. The catalytic activity follows Michaelis-Menten kinetics and is higher than that of HMPB NPs not loaded with gold nanoparticles. The NPs were employed to detect L-lactic acid colorimetrically (at 450 nm) via detection of H2O2 that is generated during enzymatic oxidation by L-lactate oxidase (LOx). The limit of detection is 4.2 μM. The assay was successfully applied to the quantitation of L-lactic acid in spiker human serum samples.Gold nanoparticle-loaded hollow Prussian Blue nanoparticles (Au@HMPB NPs) with peroxidase-like catalytic activity can oxidize the substrate 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of H2O2. The nanoparticles were applied for the detection of L-lactic acid through detection of H2O2 that is generated by L-lactate oxidase (LOx) catalyzed oxidation of L-lactic acid. [ABSTRACT FROM AUTHOR]

• Electrochemical sensor for the detection of uric acid in serum was reported. • Platinum nanoparticles were synthesized within the porous structure of ZIF-8. • ZIF-8 was carbonized to form platinum nanoparticles modified porous carbon. • The modified porous carbon was able to detect uric acid selectively and sensitively. In this study, we prepared an electrochemical sensor for the detection of uric acid (UA) in serum. Platinum nanoparticles (PtNPs) were synthesized within the porous structure of ZIF-8 and the nanocomposite was then carbonized at high temperatures to improve the adhesion rate of PtNPs in porous carbon. The synthesized materials were characterized by scanning electron microscopy and transmission electron microscopy. The sensor was able to detect uric acid in serum sensitively with good selectivity and stability. [ABSTRACT FROM AUTHOR]

Abstract: A novel catalyst of Pt/Fe3O4–CeO2 is prepared by anchoring Pt nanoparticles onto Fe3O4 coated cerium (CeO2) surface. The catalyst is characterized by TEM and tested for methanol electrooxidation in acid solution. The results demonstrated enhanced catalytic performance of Pt/Fe3O4–CeO2 toward methanol oxidation. The catalytic current of Pt/Fe3O4–CeO2 towards methanol is about 4 times higher than that of Pt–CeO2, indicating the introduction of Fe3O4 significantly improved the catalytic activity of the catalyst. The incaresed catalytic activity can be ascribed to the increased conductivity of the catalyst. [Copyright &y& Elsevier]

A surface treated nanoporous ZrO2/Chitosan composite matrix was developed to fabricate the glucose biosensor. This material combined the advantages of inorganic nanoparticles, ZrO2, and organic polymer, Chitosan. Glucose oxidase immobilized in the material maintained its activity well as the usage of glutaraldehyde was avoided. The activity of enzyme was 5.02 times greater than the cross-linked enzyme. The interaction between ZrO2/Chitosan and enzyme was characterized with FT-IR spectroscopy. The results of transmission electron microscopy of surface-treated ZrO2/Chitosan film showed that the matrix was porous and highly homogeneous. The parameters affecting the fabrication and experimental conditions of biosensors were optimized. The biosensor had a fast response of less than 10s. The linear range was 1.25 × 10-5 to 9.5 × 10-3M with a detection limit of 1.0 × 10-5M at 3σ and a sensitivity of 0.028μAmM-1. The biosensor retained about 75.2% of its original response after one-month storage in a phosphate buffer. [Copyright &y& Elsevier]

Abstract In this study, we report the fabrication of high-performance gas sensor based on a heterojunction structure in which Fe 2 O 3 nanoparticles were used to decorate MoO 3 nanobelts. The pure MoO 3 nanobelts exhibited a response to 100 parts per million (ppm) of xylene (ratio of resistance to air and gas = 9.08), with no obviously lower cross-responses to 100 ppm of ethanol, acetone, benzene, toluene, methanol and butanol. Compared with pristine MoO 3 nanobelts, Fe 2 O 3 nanoparticles decorated nanobelts demonstrated about 2–4 times higher response toward xylene. The enhanced sensing properties of Fe 2 O 3 nanoparticles-decorated MoO 3 heterostructured nanobelts can be attributed to the formation of heterojunction between Fe 2 O 3 and MoO 3. These results, combined with other reported literature, indicate that controlled engineering of surface loading/decorating is an effective strategy for designing highly sensitive and selective semiconducting metal oxide based gas sensors. Highlights • Fe 2 O 3 nanoparticles-decorated MoO 3 nanobelts are synthesized utilizing a two-step hydrothermal method. • Fe 2 O 3 /MoO 3 NBs shows enhanced response to xylene when compared with MoO 3 NBs. • The enhanced sensing performance is attributed to the formation of heterojunction between Fe 2 O 3 and MoO 3. [ABSTRACT FROM AUTHOR]

Abstract: Palladium modified cerium oxide (CeO2 or ceria) nanoparticles (Pd-CeO2) were prepared by depositing palladium nanoparticles with average diameters of 3–5nm on the surface of CeO2 via chemical reduction of the precursor (Pd2+). The electrocatalytic activity of Pd-CeO2 toward the detection of different important compounds (i.e. glucose, ascorbic acid (AA), dopamine (DA) and uric acid (UA)) has been investigated. Compared with the CeO2 or Pd modified electrode, the Pd-CeO2 modified electrode has higher catalytic activity toward the oxidation of glucose, AA, DA, and UA. A nonenzymatic glucose sensor was developed for the sensitive and selective detection of glucose. Moreover, in the mixture of AA, DA and UA, obvious electrochemical potential separations among the three detected peaks were observed, making the simultaneously determination of AA, DA and UA possible. The attractive features of Pd-CeO2 provide potential applications in sensor and biosensor design. [Copyright &y& Elsevier]

Abstract: A novel method to construct amperometric immunosensor for human serum chorionic gonadotrophin (hCG) has been described. In this study, horseradish peroxidase (HRP), Pt nanoparticles and secondary antibody (Ab2) modified MSN (Pt@MSN/HRP/Ab2) was synthesized and the multifunctional MSN was used as label for the preparation of immunosensor. With the hCG primary antibody immobilized onto thionine/graphene modified glassy carbon electrode (GCE) via crosslinking with glutaraldehyde, the electrochemical immunosensor was able to realize a reliable determination of hCG in the range of 0.01–12ngmL−1 with a detection limit of 7.50pgmL−1. This immunoassay system has many desirable merits including high sensitivity, accuracy, and little instrumentation requirement. Significantly, the new method may be quite promising, with potentially broad applications for clinical immunoassays. [Copyright &y& Elsevier]

Abstract: In this study, amino group modified mesoporous silica nanoparticles (MSN) were prepared and used to immobilize both platinum nanoparticles (PtNP) and glucose oxidase (GOx). The prepared MSN–PtNP demonstrated high stability and reactivity for catalyzing H2O2 electro-reduction, mainly due to the large amount of PtNP immobilized, the high surface area of these catalysts and the unique nanostructures formed through the synthetic route. Working at −0.2V, the linear range in response to H2O2 by the prepared MSN–PtNP can be 5×10−7 to 6×10−2 molL−1. After immobilizing GOx onto MSN–PtNP, the resulting MSN–PtNP–GOx was capable of interference-free determination of glucose with the linear range as wide as 1×10−6 to 2.6×10−2 molL−1. Furthermore, the fabricated glucose biosensor can offer significant advantages compared with its conventional counterparts, typically like the high sensitivity, good reproducibility and stability, and rapid response ability as well. The fabricated glucose biosensor demonstrated its potential in clinical applications, so as to enable the determination of glucose in real serum samples. [Copyright &y& Elsevier]

Abstract: A novel electrochemical immunosensor for sensitive detection of cancer biomarker prostate specific antigen (PSA) based on nitrodopamine (NDA) functionalized iron oxide nanoparticles (NDA–Fe3O4) is described. NDA–Fe3O4 was used both for the immobilization of primary anti-PSA antibody (Ab1) and as secondary anti-PSA antibody (Ab2) label. For the preparation of the label, mediator thionine (TH) was first conjugated onto NDA–Fe3O4 based on the amino groups of NDA, and then the amino group of TH was used to immobilize horseradish peroxidase (HRP) and Ab2. Due to the high amount of NDA anchored onto Fe3O4 surface, the loading of antibodies as well as mediator and enzyme onto NDA–Fe3O4 was substantially increased, which increased the sensitivity of the immunosensor. The resulting immunosensor displayed a wide range of linear response (0.005–50ng/mL), low detection limit (4pg/mL), good reproducibility and stability. The immunosensor was used to detect the PSA contents in serum samples with satisfactory results. [ABSTRACT FROM AUTHOR]

Abstract: A class of immuno-labels based on poly(ethylene glycol)–poly(lactic acid) (PEG–PLA) polymeric vesicles was developed in this study. To fabricate these immune-labels, the uniform Fe3O4 nanoparticles (NPs) were loaded into the vesicles followed by conjugating secondary antibody (Ab2) onto the vesicles surface, named Ab2–PEG–PLA–Fe3O4. The resulting Ab2–PEG–PLA–Fe3O4 demonstrated high catalytic activity towards H2O2, and the sensitivity of the sandwich-type immunosensor using this label for prostate specific antigen (PSA) detection increased greatly. The immunosensor based on this label exhibited high sensitivity, wide linear range (0.005–10 ng/mL), low detection limit (2 pg/mL), good reproducibility, selectivity and stability. These labels for immunosensors may provide many potential applications for the ultrasensitive detection of different cancer biomarkers. In addition, this technique also has the potential to be extended to the loading of other interesting material for preparing various kinds of labels to meet the different requirements in immunoassays. [ABSTRACT FROM AUTHOR]

• The materials were synthesized by simple hydrothermal and impregnation-calcination method. • The sensor based on PdO-α-Fe 2 O 3 showed excellent sensing performance for dimethyl disulfide (DMDS). • The sensor had excellent reproducibility and good linearity (5–25 ppm) in DMDS detection. Noble metal modification was a very promising way to enhance the gas-sensing properties of semiconductor materials. Therefore, gas sensors based on noble metal modified semiconductor materials had received much attention. In this work, PdO-modified α-Fe 2 O 3 (denoted as PdO-α-Fe 2 O 3) composite nanocrystals were fabricated by simple hydrothermal approach and wet impregnation means. The outcome disclosed that the 1.0 wt% PdO-α-Fe 2 O 3 sensor exhibited better response in detecting dimethyl disulfide (DMDS) than that of pure α-Fe 2 O 3 sensor and other PdO-α-Fe 2 O 3 sensors based on different content of palladium oxide. Specially, the maximum response value in testing 100 ppm DMDS for 1.0 wt% PdO-α-Fe 2 O 3 sensor can reach 113.1, and that of original α-Fe 2 O 3 sensor was 11.1. Moreover, the outstanding selectivity, fast response/recovery time (1 s/68 s), superior repeatability and stable long-term stability toward 100 ppm DMDS distinguished this 1.0 wt% PdO-α-Fe 2 O 3 sensor from pristine α-Fe 2 O 3 sensor. Here, the function and sensing mechanism of 1.0 wt% PdO-α-Fe 2 O 3 were also discussed. [ABSTRACT FROM AUTHOR]

A Ni 3 Fe/Co-N-C bifunctional electrocatalyst is successfully fabricated by a rapid microwave-assisted process for rechargeable Zn-air battery. • A efficient microwave-assisted approach is introduced to fabricate Ni 3 Fe/Co-N-C. • Ni 3 Fe nanoparticles are highly dispersed on ZIF-67 derived matrix. • A Pt/C comparable ORR activity and IrO 2 superior OER performance is achieved. • Ni 3 Fe/Co-N-C exhibits satisfactory performance for the wearable Zn-air battery. Precious metal-free bifunctional catalysts offer scalable possibilities for achieving oxygen cathodes in rechargeable metal-air batteries. Literature thus far suggests that the oxygen reduction and evolution reactions (i.e ORR and OER) take place at different active sites. However, the design and preparation of oxygen electrocatalysts with high-performance is still a great challenge. This work develops a general approach to introduce a nanoparticle that offers oxygen evolution reaction sites onto an oxygen reduction reaction catalyst via rapid microwave treatment. The metal–organic frameworks (Co, ZIF-8) derived Co-N-C with high ORR performance is employed as a support to homogeneously disperse OER active Ni 3 Fe nanoparticles. Potentials of 1.54 V and 0.79 V have been achieved at current densities of 10 mA cm−2 for OER and 3 mA cm−2 toward ORR, respectively. The developed rechargeable Zn-air battery assembled with Ni 3 Fe/Co-N-C as an oxygen-electrode exhibits superior efficiency and robust durability, exceeding that of commercial Pt/C + IrO 2. Furthermore, the satisfactory activity of our fabricated wristband shows the successfully practical application of flexible Zn-air batteries for wearable devices. [ABSTRACT FROM AUTHOR]