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Abstract: Pyrophosphate (PPi) is involved in lots of anabolism and bioenergetic processes in organisms and possesses important biological functions so that its detection is very significant. Here, we developed a selective fluorometric detection method for PPi with a copper(II) complex of 2,6-bis(2-benzimidazolyl)pyridine (bbimp), and then applied it to the detection of bacterial alarmone ppGpp. bbimp has the fluorescence emission at 395nm, but the bbimp–Cu2+ complex is hardly fluorescent because the intrinsic fluorescence of bbimp is effectively quenched by Cu2+. With the addition of PPi, however, the fluorescence emission of bbimp turns on with a 2nm red-shift, and has a linear relationship with PPi in the range of 3–90μmol/L. This method has good selectivity for PPi over other anions especially those phosphate-containing anions such as ATP, UTP, CTP, GTP, GDP, and PO4 3−. [Copyright &y& Elsevier]

Metal-organic gels (MOGs), a kind of soft materials, were reported as a brand new category of novel solid coreactants for enhancing electrochemiluminescence (ECL) of Ru (bpy) 3 2+ and derivatives. In this work, silver-based MOGs (Ag-MOGs) prepared by a one-step mixing and heating approach were demonstrated as novel efficient solid-state coreactants which differ from the previous research on ECL coreactant nanomaterials. It was discussed that the possible enhancement mechanism was due to the amino-rich groups and the electro-catalytic effect of Ag-MOGs, endowing them promising coreactants for the enhancement of Ru (bpy) 3 2+ ECL. Interestingly, Ag-MOGs can also enhance the ECL signal of Ru (phen) 3 2+, a derivative of Ru (bpy) 3 2+ that can specifically insert into double strand DNA, further manifesting the as-prepared Ag-MOGs can be served as ideal coreactant materials. Based on the Ru (phen) 3 2+/Ag-MOGs system, a label-free signal-on ECL biosensor for detecting of target DNA was constructed to illustrate the potential application of Ag-MOGs. This research presents an effective coreactant for Ru luminophore-based ECL systems, which not only broadens the potential application of MOGs, but also offers a unique insight into the coreactant materials. • A novel coreactant for enhancing electrochemiluminescence was developed. • Ag-MOGs can efficiently enhance the ECL signal of Ru (bpy) 3 2+. • An extremely facile and green strategy was used to synthesis Ag-MOG. • An enhanced detection signal based hybridization chain reaction was obtained. [ABSTRACT FROM AUTHOR]

For the simultaneously visual detection of hepatitis B virus (HBV), hepatitis C virus (HCV) and human immunodeficiency virus type-1 (HIV-1), a qualitative DNA chip method, combining multiplex and nested polymerase chain reaction (PCR) with arrayed anchored primer PCR and a biotin-avidin alkaline phosphatase (Av-AP) indicator system, was developed. After pretreatment of infected blood samples and reverse transcription of the RNA virus genome, PCR was performed in a single tube by using the outer primer pairs. Second round nested multiplex PCR was performed on the DNA chip, on which the primers array had already been prepared. During the arrayed anchored multiplex PCR, 5[N-(N-biotinylaminocaproyl)-ϵ-3-aminoallyl]-2-deoxy-uridine-5-triphosphate (biotin-11-dUTP) was incorporated into the extended DNA chains in order to bind avidin alkaline phosphatase via avidin and biotin. To produce purple precipitates on the chips, the enzyme substrate 5-bromo-4-chloro-3-indolyl phosphate (BCIP) was used in conjunction with the enhancer, nitro blue tetrazolium (NBT). Blood samples containing the three viruses were tested using this DNA chip and about 1 pg of specific viral DNA fragments were detected on the chip wells after nested PCR. [Copyright &y& Elsevier]

It is an advantageous way to quickly identify the toxicity of Bacillus anthracis (B. anthracis) by detecting the transcription product of the atxA gene. Herein, a novel ultrasensitive ratiometric electrochemiluminescence (ECL) biosensor with competitive mechanism and double amplified signal ways was proposed for detecting the atxA mRNA. The K 2 S 2 O 8 was used as cathodic emitter and silver metal-organic gels (AgMOG) was used as ECL enhancer. The AgMOG could accelerate the electro-catalytic reduction of S 2 O 8 2− to SO 4 ˙ˉ, which reacted with dissolved oxygen, resulting in strong cathodic ECL. Meanwhile, luminol was encapsulated in liposome as anodic amplified signal labels and the luminol anion radical also reacted with dissolved oxygen to create the anodic ECL emission. We immobilized luminol-encapsulated liposomes on the surface of AgMOG through the hybridization of DNA and mRNA. This would provide a competitive mechanism involving dissolved oxygen between K 2 S 2 O 8 and luminol. Benefiting from the competitive mechanism and amplified signal ways, this ratiometric biosensor achieved a wide linear relationship range from 10 to 300 fM with a low limit of detection (8.13 fM). Considering the accessible operation, favorable performance, and high universality of this strategy, this work may be used to analyze other mRNAs of bacteria. •A novel ultrasensitive ratiometric electrochemiluminescence (ECL) biosensor was proposed. •This is the first time that ECL platform was used to detect atxA mRNA. •The ECL biosensor with competitive mechanism involving the dissolved oxygen between K 2 S 2 O 8 and luminol was described in detail. • The atxA mRNA was detected with a detection limit as low as 8.13 fM. [ABSTRACT FROM AUTHOR]

Hematin plays a crucial role in various physiological functions, and the determination of hematin in complex biological matrixes is a significant but difficult issue. Considering the unique photophysical/photochemical properties of carbon quantum dots (CQDs) prepared with p-aminobenzoic acid (PABA) and ethanol, a new strategy for the design of fluorescent probes for hematin has been achieved. The proposed sensor array is fabricated based on the inner filter effect (IFE) between hematin and CQDs with phenomenon of selective fluorescence quenching of CQDs which results from the strong absorption of the excitation and emission spectrum of CQDs by hematin. The fluorescence quenching of CQDs is closely related to the amount of hematin and there is a good linear relationship over the range of 0.5–10 μM with a detection limit of 0.25 μM. What's more, the fluorescence assay has been successfully applied for hematin sensing in healthy human red cells showing this sensing assay has a great potential prospect for detection of hematin in the complex matrixes. [ABSTRACT FROM AUTHOR]

A facile one-pot method was proposed to synthesis cysteamine capped CdTe QDs with a high quantum yield 30%. In the synthesis process, nitrogen protection, ultrasonic treatment, and light irradiation were unnecessary. Additionally, potassium tellurite was used instead of Te powder as Te source, avoiding of the time-consuming Te powder dissolution process. The prepared QDs were found to be Hg 2+ sensitive. The detection linear range for Hg 2+ was from 5 to 300 nM, and the detection limit was calculated to be 1 nM. The detection mechanism was mainly ascribed to the electron transfer from cysteamine capped QDs to Hg 2+ , resulting in a fluorescence quenching phenomenon. In addition, we developed a portable RGB sensing gadget with the QDs as fluorescence probe for Hg 2+ detection, and the linear range was from 5 to 200 nM. Furthermore, the gadget was applied for Hg 2+ detection in tap water sample. The results showed that the average recoveries in real tap water sample were in the range from 97.2% to 115.3%, which indicated that accuracy and precision were satisfactory for practical application requirements. [ABSTRACT FROM AUTHOR]

As an integral part of many important enzymes, Cu 2+ is involved in a number of vital biological processes, which is linked to the oxidative damage and environmental contamination when Cu 2+ is excessive. In this work, Cu 2+ can be captured by the amino groups of carbon dots (CDs) to form complexes, resulting in a strong fluorescence quenching of CDs via a nonradiative electron transfer process, which offered a rapid, visual, and selective methodology for Cu 2+ detection. The probe exhibited a wide response concentration range (0.01–2 μM) to Cu 2+ with a detection limit of 6.7 nM. Significantly, the CDs presented excellent biocompatibility and high photostability, which were applicable for the visualization of Cu 2+ dynamic invasion into living cells and Tilapia mossambica. Furthermore, the toxicity of Cu 2+ ions to living cells could be inhibited with CDs by the formation of complexes. [ABSTRACT FROM AUTHOR]

The toxic plant protein ricin is a potential agent for criminal or bioterrorist attacks due to the wide availability and relative ease of preparation. Herein, we developed a novel strategy for the detection of ricin B-chain (RTB) based on isothermal strand-displacement polymerase reaction (ISDPR) by using aptamer as a recognition element and graphene oxide (GO) as a low background platform. In this method, ricin-binding aptamer (RBA) hybridized with a short blocker firstly, and then was immobilized on the surface of streptavidin-coated magnetic beads (MBs). The addition of RTB could release the blocker, which could hybridize with the dye-modified hairpin probe and trigger the ISDPR, resulting in high fluorescence intensity. In the absence of RTB, however, the fluorescence of the dye could be quenched strongly by GO, resulting in the extremely low background signal. Thus, RTB could be sensitively detected by the significantly increased fluorescence signal. The linear range of the current analytical system was from 0.75 μg/mL to 100 μg/mL and the limit of detection (3σ) was 0.6 μg/mL. This method has been successfully utilized for the detection of both the RTB and the entire ricin toxin in real samples , and it could be generalized to any kind of target detection based on an appropriate aptamer. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) is an excellent fluorescence anisotropy (FA) amplifier. However, in the conventional GO amplified FA strategy, one target can only induce the FA change of one fluorophore on probe, which limits the detection sensitivity. Herein, we developed an exonuclease III (Exo III) aided GO amplified FA strategy by using aptamer as an recognition element and ricin B-chain as a proof-of-concept target. The aptamer was hybridized with a blocker sequence and linked onto the surface of magnetic beads (MBs). Upon the addition of ricin B-chain, blocker was released from the surface of MBs and hybridized with the dye-modified probe DNA on the surface of GO through the toehold-mediated strand exchange reaction. The formed blocker–probe DNA duplex triggered the Exo III-assisted cyclic signal amplification by repeating the hybridization and digestion of probe DNA, liberating the fluorophore with several nucleotides (low FA value). Thus, ricin B-chain could be sensitively detected by the significantly decreased FA. The linear range was from 1.0 μg/mL to 13.3 μg/mL and the limit of detection (LOD) was 400 ng/mL. This method improved the sensitivity of FA assay and it could be generalized to any kind of target detection based on the use of an appropriate aptamer. [ABSTRACT FROM AUTHOR]

DNAzyme motor systems using gold nanoparticles (AuNPs) as scaffolds are useful for biosensing and in situ amplification because these systems are free of protein enzymes, isothermal, homogeneous, and sensitive. However, detecting different targets using the available DNAzyme motor techniques requires redesigns of the DNAzyme motor. We report here a toehold-exchange translator and the translator-mediated DNAzyme motor systems, which enable sensitive responses to various nucleic acid targets using the same DNAzyme motor without requiring redesign. The translator is able to efficiently convert different nucleic acid targets into a specific output DNA that further activates the pre-silenced DNAzyme motor and consequently initiates the autonomous walking of the DNAzyme motor. Simply adjusting the target-binding region of the translator enables the same DNAzyme motor system to respond to various nucleic acid targets. The translator-mediated DNAzyme motor system is able to detect as low as 2.5 pM microRNA-10b and microRNA-21 under room temperature without the need of separation or washing. We further demonstrate the versatility of the translator and the DNAzyme motor by successful construction and operation of four logic gates, including OR, AND, NOR, and NAND logic gates. These logic gates use two microRNA targets as inputs and generate amplified fluorescence signals from the operation of the same DNAzyme motor. Incorporation of the toehold-exchange translator into the DNAzyme motor technology improves the biosensing applications of DNA motors to diverse nucleic acid targets. [Display omitted] • Toehold exchange translators enhanced applicability of DNAzyme motors. • Translator-mediated DNAzyme motors achieved sensitive detection of microRNAs. • Two translators facilitated a DNAzyme motor to operate four logic gates. • OR, AND, NOR, and NAND logic gates responded to input miR10b and miR21. [ABSTRACT FROM AUTHOR]

In this manuscript, a nanosilver enhanced SERS strategy was successfully constructed for the determination of DNA methyltransferase activity in soulution combined with hybridization chain reaction (HCR). The proposed method was mainly on the basis of excellent separation ability of magnetic microparticles (MMPs), HCR as signal amplification unit and assembled AgNPs as enhancement substrate. In the presence of M. SssI MTase, the duplex sequence (5′-CCGG-3′) tethered to MMPs was methylated, which cannot be cleaved by HpaII endonuclease. The resulted DNA skeleton captured on MMPs then triggered the HCR reaction, generated a polymerized and extended symmetrical sequence, in which more biotin terminal was available for the conjugation of AgNPs-SA, leading to significantly amplified SERS response. When it was used to analyze M. SssI activity, a linear equation ∆ I SERS =1215.32+446.80 c M. SssI was obtained with the M. SssI activity ranged from 0.1 to 10.0 U with the correlation coefficient ( r 2 ) of 0.97. The most important advantage of this method is the combination of SERS and HCR in solution for the first time and its good selectivity, which enabled the detection of even one-base mismatched sequence. The new assay method holds great promising application to be a versatile platform for sensitive, high-throughput detection, and the screening of new anticancer drugs on DNA MTase. [ABSTRACT FROM AUTHOR]

DNA nanomachines, a delicate type of molecular machines, have been a research hotspot in biotechnology and materials. Here a two-dimensional (2D) DNA walking nanomachine with high working efficiency and low cost was easily assembled by using graphene oxide (GO) as the working platform for precisely fluorescent bioassay through the binding of target hepatitis B virus DNA (HBV-DNA) and the driving force of Exonuclease III (Exo III). The presence of HBV-DNA made continuous Exo III digestion of the FAM-modified DNA (FAM-DNA) in double-strand DNA (dsDNA) part in a burnt-bridge mechanism to output a "one-to-more" amplified signal. Accordingly, a 2D DNA walking nanomachine with simple operation and high cost-performance ratio was constructed. The walking speed of nanomachine was found to be regulated by loading DNA density on single sheet of GO. Furthermore, this nanomachine had low background since the dual energy transfer including fluorescence resonance energy transfer (FRET) from FAM to BHQ1 and the long-range resonance energy transfer (LrRET) from FAM to GO, making the biosensing applications highly promising. [ABSTRACT FROM AUTHOR]

DNA logic computing has captured increasing interest due to its ability to assemble programmable DNA computing elements for disease diagnosis, gene regulation, and targeted therapy. In this work, we developed an aptamer -equipped high-integrated DNA biocomputing platform (HIDBP- A) with a dual-recognition function that enabled cancer cell targeting. Dual microRNAs were the input signals and can perform AND logic operations. Compared to the free DNA biocomputing platform (FDBP), the integration of all computing elements into the same DNA tetrahedron greatly improved logic computing speed and efficiency owing to the confinement effect reflected by the high local concentration of computing elements. As a proof of concept, the utilization of microRNA as the input signal was beneficial for improving the scalability and flexibility of the sequence design of the logic nano-platform. Given that the different microRNAs were over-expressed in cancer cells, this new HIDBP- A has great promise in accurate diagnosis and logic-controlled disease treatment. [ABSTRACT FROM AUTHOR]

Abstract: A new metal-enhanced fluorescence (MEF) based platform was developed on the basis of distance-dependent fluorescence quenching-enhancement effect, which combined the easiness of Ag-thiol chemistry with the MEF property of noble-metal structures as well as the molecular beacon design. For the given sized AgNPs, the fluorescence enhancement factor was found to increase with a d 6 dependency in agreement with fluorescence resonance energy transfer mechanism at shorter distance and decrease with a d −3 dependency in agreement with plasmonic enhancement mechanism at longer distance between the fluorophore and the AgNP surface. As a proof of concept, the platform was demonstrated by a sensitive detection of mercuric ions, using thymine-containing molecular beacon to tune silver nanoparticle (AgNP)-enhanced fluorescence. Mercuric ions were detected via formation of a thymine–mercuric–thymine structure to open the hairpin, facilitating fluorescence recovery and AgNP enhancement to yield a limit of detection of 1nM, which is well below the U.S. Environmental Protection Agency regulation of the Maximum Contaminant Level Goal (10nM) in drinking water. Since the AgNP functioned as not only a quencher to reduce the reagent blank signal but also an enhancement substrate to increase fluorescence of the open hairpin when target mercuric ions were present, the quenching-enhancement strategy can greatly improve the detection sensitivity and can in principle be a universal approach for various targets when combined with molecular beacon design. [Copyright &y& Elsevier]

Abstract: In this study, a facile strategy for highly selective and sensitive detection of bacterial alarmone, ppGpp, which is generated when bacteria face stress circumstances such as nutritional deprivation, has been established by developing an off–on fluorescent probe of Cu2+-mediated silver nanoclusters (Ag NCs). This work not only achieves highly selective detection of ppGpp in a broad range concentration of 2–200μM, but also improves our understanding of the specific recognitions among DNA–Ag NCs, Cu2+, and ppGpp. The present strategy, together with other reports on the Ag NCs-related analytical methods, has also identified that Ag NCs functionalized with different molecules on their surfaces can be engineered fluorescent probes for a wide range of applications such as biosensing and bioimaging. [Copyright &y& Elsevier]

As the common hepatitis viruses, hepatitis B virus (HBV) and hepatitis C virus (HCV) are important causes of liver diseases, which greatly threaten human health and public hygiene. Furthermore, due to the similar transmission routes of HBV and HCV, it is highly susceptible to suffer from the cross-infection of HBV and HCV when humans are infected by hepatitis viruses. So it is urgent to develop strategies with high sensitivity to distinguish HBV/HCV and detect their overlapping infection. Herein, a new biosensor named "hepatitis virus indicator" for simultaneous detection of HBV and HCV based on the automatic particle enumeration was developed by the combination of Exo III assisted signal amplification strategy and particle counting technology with a dark-field microscopy. The limit of detections (LOD) were as low as 0.194 pM for HBV and 0.169 pM for HCV, respectively. In addition, the proposed method was capable of simultaneously detecting HBV and HCV based on the colorful light scattering from plasmonic nanoparticles. The proposed assay was simple, sensitive and selective for the simultaneous detection of HBV and HCV, which provided a new idea for the early diagnosis of diseases, such as hepatitis A virus (HAV), hepatitis D virus (HDV) and hepatitis E virus (HEV). • An innovative method for simultaneous detection of HBV and HCV was developed with dark-field microscopic imaging. • The sensitivity is improved by combination of single-particle counting technology with Exo III-assisted signal amplification. • The proposed strategy avioded the non-specific adsorption and the accuracy was improved by magnetic separation. • The proposed method is universal, which can be extended to a variety of other types of DNA disease biomarkers. [ABSTRACT FROM AUTHOR]

MicroRNAs involved in tumor-related tissues at abnormal expression level present tremendous potential in the early diagnosis of cancers. However, their intrinsic shortcomings, for instance, low abundance and high sequence homology, make it challengeable to quantify them with high sensitivity and selectivity. Herein, a highly sensitive platform with great specificity was developed for microRNA-21 based on the produced-I 2 triggered chemical etching of gold nanorods to a smaller size, resulting in a significant blue shift and a great intensity decrease in the localized surface plasmon resonance (LSPR) scattering. The synergism of strand displacement and enzymatic reaction enabled the proposed strategy with a high sensitivity and selectivity toward microRNA-21 in a dynamic range from 0.1 to 10,000 pM and a low limit of detection of 71.22 fM (3σ/k) by dark-field microscope. Additionally, the remarkable discrimination of single nucleotide difference suggested the superior selectivity towards microRNA-21, which presented a satisfactory recovery in human serum samples. The proposed plasmon platform could also serve as a universal and sensitive detection of cancer biomarkers, presenting the amusing application prospects in the early diagnosis of various cancers by adapting the corresponding nucleic acid sequences. (1) A plasmonic biosensor for the highly sensitive detection of microRNA-21 by dark-field light scattering imaging was proposed with the detection limit as low as 71.22 fM. (2) By means of strand displacement reaction and the combination with efficient magnetic separation, the specificity was satisfactory for microRNA-21 detection. (3) This strategy is a universal platform in detection of different miRNAs for the early diagnosis of caners. [ABSTRACT FROM AUTHOR]

Dynamic DNA nanodevices-based assembly is currently well developed for a broad range of analytical applications. However, some problems persist, such as false positives, nuclease digestions, and exclusive interferences with single signal in complex cellular environment. Herein, we have established a method for imaging cellular miR-155, where it induced assembly of two tetrahedral DNA frameworks (TDFs), TDF-1 and TDF-2, both of which had four fluorescence modified hairpins (Cy3 for TDF-1 and Cy5 for TDF-2, respectively) at each angle, into polymeric tetrahedral DNA frameworks (PTDFs). The formation of PTDFs was greatly dependent on miR-155 overexpressed in breast cancer cells since miR-155 drove catalytic hairpin assembly (CHA) reaction by opening the hairpins at the vertices of TDF-1 to hybridize with TDF-2. Upon the completion of hybridization, the miR-155 was released, starting the next cycle of the CHA reaction. Measurements of atomic force microscopy (AFM) and Förster resonance energy transfer (FRET) showed that the formation of PTDFs occurred owing to the multivalent assembly of TDF-1 and TDF-2. By utilizing the formation of PTDFs, miR-155 was detected in a linear range from 0.5 nM to 30 nM with a 0.35 nM limit of determination, enabling the successful imaging of endogenous miR-155 in live cells through the FRET signal from Cy3 to Cy5. These studies demonstrated that this method significantly strengthened the resistance nuclease to digestion and stable ability with exclusive interference. Our present work has the following three advantages: • A dynamic assembly system that integrated tetrahedral DNA frameworks TDFs with catalytic hairpin assembly reaction was proposed for ratiometric sensing miR-155. • TDFs with higher capacity of hairpins exhibited excellent internalization and nuclease-resistant ability for the enhanced FRET signal, which is favorable for minimizing interferences and keeping stable in biological environment. • Target miR-155 could circularly trigger polyvalence assembly of TDF-1 and TDF-2, which is available for dynamic imaging intracellular miR-155 with higher selectivity and sensitivity. [ABSTRACT FROM AUTHOR]

In this paper, a nonenzymatic glucose biosensor based on perovskite LaTiO3–Ag0.2(LTA) modified electrode was presented. The morphology and the composition of the perovskite LaTiO3–Ag0.2 nanomaterials were characterized by using scanning electron microscopy (SEM) and X-ray diffraction (XRD) respectively. The LaTiO3–Ag0.2(LTA) composite was investigated by electrochemical characterization using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Under optimal conditions, CV and chronoamperometry (I-t) study revealed that, compared with the bare glassy carbon electrode (GCE), the modified electrode showed a remarkable increase in the efficiency of the electrocatalytic oxidation of glucose, starting at around +0.70V (vs. Ag/AgCl). The prepared sensor exhibited a high sensitivity of 784.14µAmM−1 cm−2, a low detection limit of 2.1×10−7 M and a wide linear range from 2.5µM to 4mM (R=0.9997). More importantly, the LTA modified electrode was also relatively insensitive to commonly interfering species such as ascorbic acid (AA), uric acid (UA), dopamine (DA) in high potential. Moreover, the nonenzymatic sensor was applied to the determination of glucose in human serum samples and the results were in good agreement with clinical data. Electrodes modified with perovskite nanomaterials are highly promising for nonenzymatic electrochemical detection of glucose because of their high sensitivity, fast response, excellent stability and good reproducibility. [ABSTRACT FROM AUTHOR]

Abstract: In this report, a simple and label-free colorimetric assay was developed for detecting alkaline phosphatase (ALP). Based on the conjugated gold nanoparticle/adenosine triphosphate (AuNP/ATP) sensing system, this assay is highly sensitive and selective. In this system, ATP induces the aggregation of cetyltrimethylammonium bromide (CTAB)-capped AuNPs and ALP stimulates the disaggregation of AuNPs by converting ATP into adenosine through an enzymatic dephosphorylation reaction. Hence, the presence of ALP can be visually observed (gray-to-red color change) and monitored by the shift of the surface plasmon resonance (SPR) absorption band of AuNPs. Furthermore, the dynamic range of the method can be varied by addition of different metal ions (e.g. 100–600unit/L to 5.0–100unit/L and 0.2–20unit/L in the presence of Ca2+ and Pb2+, respectively). The feasibility of this sensitive and specific assay with a tunable dynamic range was demonstrated to be consistent even in human serum samples. [Copyright &y& Elsevier]

In this contribution, a simple, rapid, colorimeteric and selective assay for lysine was achieved by a controllable end-to-end assembly of gold nanorods (AuNRs) in the presence of Eu3+ and lysine. This one-pot end-to-end assembly of 11-mercaptoundecanoic acid (MUA) modified AuNRs was occurred in Britton–Robinson buffer of pH 6.0, which involves the coordination binding between Eu3+ and COO− groups as well as the electrostatic interaction of the COO− groups of MUA with the -NH3+ group of lysine. As monitored by absorption spectra, scanning electron microscopic (SEM) images and dynamic light scattering (DLS) measurement, the end-to-end chain assembly results in large red-shift in the longitudinal plasmon resonance absorption (LPRA), giving red-to-blue color change of AuNRs. Importantly, it was found that the red-shift of LPRA is linearly proportional to the concentrations of lysine in the range of 5.0×10−6–1.0×10−3 M with the limit of detection (LOD) being 1.6×10−6 M (3σ/k). This red-shift of LPRA is highly selective, making it possible to develop a rapid, selective and visual assay for lysine in food samples. [ABSTRACT FROM AUTHOR]

A simple and efficient strategy was developed to fabricate CuO nanoparticles (CuO-NPs) with high surface area by the direct pyrolysis of a metal-organic gel (MOG) precursor for constructing versatile catalytic interfaces. Unexpectedly, the obtained CuO-NPs exhibited excellent electrocatalytic activity for glucose (Glu) oxidation reaction. The linear range of glucose was from 5 μM to 600 with the detection limit of 0.59 μM. Additionally, the CuO-NPs showed distinguished intrinsic peroxidase-mimicking activities, which can be further used as biomimetic nanozymes for sensitively and rapidly detecting cholesterol. A good linearity of cholesterol was performed in the range from 1 μM to 15 μM with the detection limit of 0.43 μM. The as-prepared CuO-NPs could provide a versatile catalytic platform for the application of electrochemical sensors and biomimetic enzyme catalytic systems. This study proved the high potential of MOG-derived nanostructured transition metal oxides (TMOs) with multiple complex functions. Image 1 • Metal-organic gel (MOG) as a novel and potential precursor was utilized to synthesize porous CuO-NPs with high surface area. • The CuO-NPs exhibited excellent electrocatalytic and peroxidase-mimicking activities, which can construct versatile catalytic interfaces for promising applications in electrochemical sensors and biomimetic enzyme catalytic systems. • The novel idea revealed the high potential of MOG-derived nanostructured TMOs with multiple complex functions. [ABSTRACT FROM AUTHOR]