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Non-invasive wearable sweat glucose sensors are expected to be highly desirable for personalized diabetes management. Therefore, developing facile, convenient, and scalable manufacturing method of such wearable sensors is urgently needed. Herein, we report a simple and low-cost stamping-vacuum filtration dry transfer (SVFDT) method for construction of a wearable sweat glucose electrochemical sensor. In this patch, a three-electrode array template was made by using a polyvinyl chloride (PVC) stamp, followed by the preparation of multiwalled carbon nanotubes (MWCNTs)/polydimethylsiloxane (PDMS) (MP) film electrode using the vacuum-filtration dry transfer method. In addition, for further enhancing the conductivity of the electrode, another similar stamp with a raised surface dipping carbon nanotubes (CNTs) conductive coating was stamped on the surface of the MP electrode to obtain CNTs/MWCNTs/PDMS (CMP) electrode. CMP electrode was modified with the enzyme-like Ni-Co metal-organic framework (MOF) material which showed good electro-catalytic activity and achieved high sensitivity for glucose detection with a low detection limit of 6.78 μM and a wide linear range of 20 μM - 1.1 mM. More importantly, the Ni-Co MOF modified CMP (NCMP) electrode also displayed high stability under stretching and bending conditions. Finally, the sweat absorbent cloth was combined with the NCMP film electrode to form a wearable flexible electrochemical sensor patch, which could adhere to the skin to enrich sweat and realize real-time detection of sweat glucose with high accuracy. This SVFDT method can also be applied to the fabrication of other electronic devices., 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 © 2023 Elsevier B.V. All rights reserved.)

Metal-organic frameworks (MOFs) show excellent catalytic activity and have been widely applied in diagnosis of diseases and tumors. However, current assay methods usually involve cumbersome configurations and complicated procedures, which inhibit their practical applications. Hence, a Cu-Ni MOF/carbon printed electrode (CPE)-based integrated electrochemical immunosensor was constructed for highly sensitive and efficient determination of carcinoembryonic antigen (CEA). First, highly conductive carbon ink was screen-printed onto a polyethylene terephthalate substrate to manufacture a CPE. Afterward, an aminated Cu-Ni MOF was prepared by a typical solvothermal strategy and modified on the CPE. Owing to its excellent peroxidase activity, the Cu-Ni MOF can catalytically oxidize hydroquinone using hydrogen peroxide, which greatly amplifies the peak current signal. Then the formation of an immune complex inhibited the catalytic activity of the MOF, thus enabling the quantitative determination of CEA content with a wide linear range of 0.5 pg mL -1 -500 ng mL -1 and a low detection limit of 0.16 pg mL -1 . Furthermore, the Cu-Ni MOF/CPE-based integrated portable electrochemical immunosensor also showed satisfactory performance in the detection of CEA in clinical serum samples with excellent accuracy, showing great potential for application in point-of-care disease diagnosis.

Monitoring cortisol, a hormone released by the adrenal cortex in response to stress, is essential to evaluate the endocrine response to stress stimuli. While the current cortisol sensing methods require large laboratory settings, complex assay, and professional personnel. Herein, a novel flexible and wearable electrochemical aptasensor based on a Ni-Co metal-organic frameworks (MOF) nanosheet-decorated carbon nanotubes (CNTs)/polyurethane (PU) film is developed for rapid and reliable detection of cortisol in sweat. First, the CNTs/PU (CP) film was prepared by a modified wet spinning technology, and the CNTs/polyvinyl alcohol (PVA) solution was thermally deposited on the surface of CP film to form the highly flexible CNTs/PVA/CP (CCP) film with excellent conductivity. Then aminated Ni-Co MOF nanosheet prepared by a facile solvothermal method was conjugated with streptavidin and modified on the CCP film. Biofunctional MOF can effectively capture cortisol aptamer due to its excellent specific surface area. In addition, the MOF with peroxidase activity can catalytic oxidization of hydroquinone (HQ) by hydrogen peroxide (H 2 O 2 ), which could amplify the peak current signal. The catalytic activity of Ni-Co MOF was substantially suppressed in the HQ/H 2 O 2 system due to the formation of the aptamer-cortisol complex, which reduced the current signal, thereby realizing highly sensitive and selective detection of cortisol. The sensor has a linear range of 0.1-100 ng/mL and a detection limit of 0.032 ng/mL. Meanwhile, the sensor showed high accuracy for cortisol detection under mechanical deformation conditions. More importantly, the prepared MOF/CCP film based three-electrode was assembled with the polydimethylsiloxane (PDMS) substrate, and the sweat-cloth was used as the sweat collection channel to fabricate a wearable sensor patch for monitoring of cortisol in volunteers' sweat in the morning and evening. This flexible and non-invasive sweat cortisol aptasensor shows great potential for quantitative stress monitoring and management., 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 © 2023 Elsevier B.V. All rights reserved.)

In-situ growth of CsPbBr 3 nanocrystal into Eu-BTC was realized for synthesis of dual-emission CsPbBr 3 @Eu-BTC by a facile solvothermal method, and a novel ratiometric fluorescence sensor based on the CsPbBr 3 @Eu-BTC was prepared for rapid, sensitive and visual detection of Hg 2+ in aqueous solution. The transmission electron microscopy (TEM), X-ray diffraction pattern (XRD), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET) analysis were used to verify the successful incorporation of CsPbBr 3 into the Eu-BTC. Meanwhile, the CsPbBr 3 @Eu-BTC nanocomposite maintained high fluorescence performance and stability in aqueous solution. After adding Hg 2+ , the green fluorescence of CsPbBr 3 was quenched and the red fluorescence of Eu 3+ remained unchanged, while the color changed from green to red obviously. The occurrence of dynamic quenching and electron transfer were verified by fluorescence lifetime, Stern-Volmer quenching constant and XPS analysis. The ratiometric fluorescence sensor shows high analytical performance for Hg 2+ detection with a wide linear range of 0-1 μM and a low detection limit of 0.116 nM. In addition, it also shows high selectivity for the detection of Hg 2+ and can be successfully applied to detect Hg 2+ in environmental water samples. More importantly, a novel paper-based sensor based on the CsPbBr 3 @Eu-BTC ratiometric probe was successfully manufactured for the visual detection of Hg 2+ by naked eyes. This new type of ratiometric fluorescent sensor shows great potential for applications in point-of-care diagnostics., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Using two-dimensional (2D) nickel-based metal organic framework (Ni-MOF) nanosheets as a matrix, Eu 3+ and Ag + were incorporated to synthesize Ag/Eu@Ni-MOF with double luminescence centers of Eu 3+ ion (615 nm) and organic ligand (524 nm). And a ratiometric luminescence sensor is constructed based on Ag/Eu@Ni-MOF for sensitive detection of biothiols in aqueous solutions. The dual-emissive fluorescence properties can be tuned by changing the amounts of Ag + ions doping. The results of temperature and pH effects on the fluorescence of Ag/Eu@Ni-MOF indicates that the Ag/Eu@Ni-MOF is a temperature-sensitive material and the fluorescence of Ag/Eu@Ni-MOF can keep stable over a wide pH range. Due to the binding of -SH in cysteine (Cys) and glutathione (GSH) with Ag + , the ligand luminescence was significantly inhibited by weakening the Ag + influence on the energy transfer process in the MOFs. Therefore, ratiometric fluorescent sensing of biomolecular thiols was realized based on the dual-emission Ag/Eu@Ni-MOF. More importantly, the fluorescence color change can be observed with naked eyes to realize visual detection. The ratiometric fluorescent sensor exhibits high performance for Cys and GSH detection with a wide linear range of 5-250 µM and a relatively low detection limit of 0.20 µM and 0.17 µM, respectively. Furthermore, the biothiols content in human serum was determined with satisfactory results. It proves the Ni-MOF nanosheets can be used as a stable matrix for construction luminescent MOFs for the first time, and validate the great potential of Ag/Eu@Ni-MOF as a ratiometric fluorescent probe for point-of-care testing (POCT) in disease diagnosis., (© 2021. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

A covalent organic framework (COF) is a promising type of porous material with customizable surface characteristics. Confining multiple catalytic units within a mesoporous COF can generate abundant active sites and improve the catalytic performance. In this work, a COF with both metalloporphyrin and a metal nanoparticle complex denoted as hemin/TAPB-DMTP-COF/AuNPs (TAPB: 1,3,5-tris(4-amino-phenyl)benzene, DMTP: 2,5-dimethoxyterephaldehyde, AuNPs: Au nanoparticles) has been successfully fabricated through a hierarchical encapsulation method. The as-synthesized composite was then employed to construct an electrochemical sensing platform for the efficient detection of bisphenol A (BPA). Under the optimal conditions, the hemin/TAPB-DMTP-COF/AuNP sensor presented a linear range of 0.01-3 μmol L -1 and a low detection limit of 3.5 nmol L -1 . The satisfactory signal amplification is based on a triple-signaling amplification strategy due to the abundant Fe 3+ sites of Fe-porphyrin, high conductivity of AuNPs and a large specific surface area of the TAPB-DMTP-COF. The proposed method was used to measure the content of BPA in different water samples with a satisfactory recovery from 95.5 to 104.0%, suggesting the great potential of the sensor in practical applications.

It is very important to develop a rapid, simple, low cost point-of-care (POC) method for the early diagnosis of pathogens. In this work, a flexible paper-based electrode based on nickel metal-organic framework (Ni-MOF) composite/Au nanoparticles/carbon nanotubes/polyvinyl alcohol (Ni-Au composite/CNT/PVA) was constructed to detect target human immunodeficiency virus (HIV) DNA by DNA hybridization using methylene blue (MB) as a redox indicator. The CNT/PVA and Ni-Au composite were deposited on the cellulose membrane by vacuum filtration and drop-coating method in turn to obtain Ni-Au composite/CNT/PVA (CCP) film electrode. Compared to the CNT/PVA film electrode, CCP film electrode makes a higher loading of the probe DNA for its large specific surface area and conjugated π-electron system that can provide hydrogen bond sources to achieve interactions between MOF and single-stranded DNA, which improves the sensitivity for detecting target DNA. The variation of peak current for MB molecules adsorbed onto DNA before and after hybridization with HIV DNA was monitored. Electrochemical results proved that the CCP film maintained stable electrochemical property even after bending 200 times or stretching under different strains from 0% to 20%. The flexible paper electrode showed excellent sensing performance with a linear range of 10 nM-1 μM and a low detection limit of 0.13 nM. The target HIV DNA was successfully detected even in complex serum samples using the flexible CCP film electrode. Therefore, the simple and inexpensive flexible paper-based MOF composite film electrode can also be utilized for other pathogens POC diagnosis., (Copyright © 2021. Published by Elsevier B.V.)

Metal-organic frameworks (MOFs), which are a class of coordination polymers constructed by metal ions or clusters with organic ligands, have emerged as exciting inorganic-organic hybrid materials with the superiorities of inherent crystallinity, adjustable pore size, clear structure, and high degree of functionalization. The MOFs have attracted much attention to develop good luminescent functional materials due to their inherent luminescent centers of both inorganic and organic photonic units. Furthermore, the pores within MOFs can also be used to encapsulate a large number of luminescent guest species, which provides a broader luminescent property for MOF materials. MOFs possess the incomparable multifunctional advantages of inorganic and organic luminescent materials. A large number of luminescent MOFs (LMOFs) have been synthesized for applications in sensing, white-light-emitting diodes (LED), photocatalysis, biomedicine, etc. This paper reviews the encapsulation of various luminescent guests such as lanthanide ions, dyes, quantum dots, and luminescent complexes in metal-organic frameworks to construct luminous sensors with single- or double-emission centers, as well as the research progress of these sensors in chemical sensing. Finally, the challenges in these fields were outlined and the prospects for future development were put forward.

Existing electrochemical biosensing platforms, using traditional rigid and unstretchable electrodes, cannot monitor the biological signaling molecules released by cells in a mechanically deformed state in real time. Here, a stretchable and flexible electrochemical sensor was developed based on nickel metal-organic framework composite/Au nanoparticle-coated carbon nanotubes (Ni-MOF composite/AuNPs/CNTs) for sensitive detection of dopamine (DA) released by C6 living cells in real time. A Ni-MOF composite was obtained by introducing Ni, NiO, and a carbon frame onto the surface of two-dimensional (2D) Ni-MOF nanosheets using an efficient one-step calcination method. The hybrid of Ni-MOF composite/AuNPs/CNTs that deposited on the poly(dimethylsiloxane) (PDMS) film endowed the sensor with excellent electrochemical performance with a wide linear range of 50 nM to 15 μM and a high sensitivity of 1250 mA/(cm 2 M) and also provided the sensor with desirable stability against mechanical deformation. Furthermore, the stretchable electrode also displayed good cellular compatibility while C6 living cells can be cultured and proliferated on it with strong adhesion. Then, the DA released by C6 living cells with chemical induction in both natural and stretched states was monitored using our stretchable and flexible electrochemical sensor in real time. This indicates that our new design of flexible Ni-MOF composite/AuNPs/CNTs/PDMS (NACP) film electrodes provides more opportunities for the detection of chemical signals released from cells and soft living organisms even under mechanically deformed states.

Porphyrinic Metal-Organic Frameworks (porph-MOFs) are attracting attention due to the redox activity in the porphyrin subunit. Herein, we report the design of a novel core-shell structure hybrid material with a sea-cucumber morphology, namely PMeTh, containing the poly(3-methythiophene) conducting polymer coated on the surface of iron-based porph-MOFs PCN-222(Fe) via in-situ oxidative chemical polymerization. The porous PCN-222(Fe) serves as the electrocatalytic sites, while the poly(3-methythiophene) conducting polymer functions as the charge collector to facilitate the charge transport to the redox active sites. The resulting PMeTh composite demonstrates an excellent electrochemical response towards the levodopa detection. The sensitivity towards the L-dopa detection is estimated to be 1.868 μA ⋅ μM -1 ⋅ cm -2 in the linear concentration of 0.05-7.0 μmol ⋅ L -1 and 0.778 μA ⋅ μM -1 ⋅ cm -2 in the linear concentration of 7.00-100 μmol ⋅ L -1 , respectively. Additionally, the levodopa sensor exhibits a low detection limit of 2 nmol L -1 as well as excellent stability after 120 cycles in 10 μmol L -1 levodopa. The feasibility of this novel L-dopa sensor was evaluated in human urine samples by standard addition. The satisfactory recoveries were in the range of 97.0-104.5% with the R.S.D. value lower than 4.4%. The method of intergrating porph-MOFs and conducting polymers can efficiently expand the porph-MOFs based composites in bioanalysis., (Copyright © 2019 Elsevier B.V. All rights reserved.)

A two-dimensional (2D) Ni based metal-organic framework (MOF) nanosheets were synthesized using a one-step solvent-thermal method. The as-prepared nanosheets were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), powder X-ray diffraction (XRD) and energy disperse spectroscopy (EDS) mapping. Ni-MOF nanosheet was first time found to used as a peroxidase mimetic with catalytic activities and could catalyze the oxidation of the substrate 3,3,5,5-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H 2 O 2 ). Catalytic mechanism analysis suggested the enzymatic kinetics of Ni-MOF nanosheets followed typical Michaelis-Menten theory and Ni-MOF nanosheets possess a higher affinity for two substrates (TMB and H 2 O 2 ) than horseradish peroxidase (HRP). Furthermore, Ni-MOF nanosheet was applied to establish an H 2 O 2 colorimetric sensor which deserves a wide linear range of 0.04 ~ 160 μM and a low detection limit of 8 nM. Also the application of this sensor for H 2 O 2 detection in human serum and disinfectant was demonstrated and satisfactory results were obtained. Thus, the simple and sensitive Ni-MOF/TMB/H 2 O 2 colorimetric system has great promising applications in clinical medicine and food environment analysis., (Copyright © 2018. Published by Elsevier B.V.)

A nonenzymatic glucose electrochemical sensor was constructed based on Au nanoparticles (AuNPs) decorated Ni metal-organic-framework (MOF)/Ni/NiO nanocomposite. Ni-MOF/Ni/NiO nanocomposite was synthesized by one-step calcination of Ni-MOF. Then AuNPs were loaded onto the Ni-based nanocomposites' surface through electrostatic adsorption. Through characterization by transmission electron microscopy (TEM), high resolution TEM (HRTEM) and energy disperse spectroscopy (EDS) mapping, it is found that the AuNPs were well distributed on the surface of Ni-based nanocomposite. Cyclic voltammetric (CV) study showed the electrocatalytic activity of Au-Ni nanocomposite was highly improved after loading AuNPs onto it. Amperometric study demonstrated that the Au-Ni nanocomposites modified glassy carbon electrode (GCE) exhibited a high sensitivity of 2133.5 mA M -1 cm -2 and a wide linear range (0.4-900 μM) toward the oxidation of glucose with a detection limit as low as 0.1 μM. Moreover, the reproducibility, selectivity and stability of the sensor all exhibited outstanding performance. We applied the as-fabricated high performance sensor to measure the glucose levels in human serum and obtained satisfactory results. It is believed that AuNPs decorated Ni MOF/Ni/NiO nanocomposite provides a new platform for developing highly performance electrochemical sensors in practical applications., (Copyright © 2018 Elsevier B.V. All rights reserved.)

CsPbX3 perovskite nanocrystal (NC) is considered as an excellent optical material and is widely applied in optoelectronics. However, its poor water stability impedes its study in enzyme‐like activity, and further inhibits its application in biomimetic cascade catalysis. Herein, for the first time, the oxidase‐like and ascorbate oxidase‐like activities of an amphiphilic polymer capped CsPbX3 are demonstrated, and its catalytic mechanism is further explored. Furthermore, an all‐nanozyme cascade system (multifunctional CsPbBr3@Zr‐metal organic framework (Zr‐MOF) and Prussian blue as oxidase‐like and peroxidase‐like nanozyme) is constructed with a portable paper‐based device for realizing the dual‐mode (ratiometric fluorescence and colorimetric) detection of ascorbic acid in a point‐of‐care (POC) fashion. This is the first report on the utilization of all‐inorganic CsPbX3 perovskite NC in biomimetic cascade catalysis, which opens a new avenue for POC clinical disease diagnosis. [ABSTRACT FROM AUTHOR]

Using two-dimensional (2D) nickel-based metal organic framework (Ni-MOF) nanosheets as a matrix, Eu3+ and Ag+ were incorporated to synthesize Ag/Eu@Ni-MOF with double luminescence centers of Eu3+ ion (615 nm) and organic ligand (524 nm). And a ratiometric luminescence sensor is constructed based on Ag/Eu@Ni-MOF for sensitive detection of biothiols in aqueous solutions. The dual-emissive fluorescence properties can be tuned by changing the amounts of Ag+ ions doping. The results of temperature and pH effects on the fluorescence of Ag/Eu@Ni-MOF indicates that the Ag/Eu@Ni-MOF is a temperature-sensitive material and the fluorescence of Ag/Eu@Ni-MOF can keep stable over a wide pH range. Due to the binding of -SH in cysteine (Cys) and glutathione (GSH) with Ag+, the ligand luminescence was significantly inhibited by weakening the Ag + influence on the energy transfer process in the MOFs. Therefore, ratiometric fluorescent sensing of biomolecular thiols was realized based on the dual-emission Ag/Eu@Ni-MOF. More importantly, the fluorescence color change can be observed with naked eyes to realize visual detection. The ratiometric fluorescent sensor exhibits high performance for Cys and GSH detection with a wide linear range of 5-250 µM and a relatively low detection limit of 0.20 µM and 0.17 µM, respectively. Furthermore, the biothiols content in human serum was determined with satisfactory results. It proves the Ni-MOF nanosheets can be used as a stable matrix for construction luminescent MOFs for the first time, and validate the great potential of Ag/Eu@Ni-MOF as a ratiometric fluorescent probe for point-of-care testing (POCT) in disease diagnosis. [ABSTRACT FROM AUTHOR]

The fabrication of chemically stable metal–organic frameworks for electrochemical sensors is essential to broaden their applications. In this study, the integration of a Zr-based metal–organic framework (UiO-66-NH2) with multi-walled carbon nanotubes (MWCNTs) was achieved by a one-pot solvothermal reaction. This composite was then characterized by scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, Fourier transform infrared spectroscopy, and contact angle measurements. The porous structure and unreacted amine groups provided by UiO-66-NH2 frameworks accompanied by the excellent conductivity of MWCNTs have made this composite an ideal electrode material for lead detection. After the optimization of MWCNT content and the detection conditions, the oxidation peak currents were proportional to lead concentrations in the range of 0.001–0.8 μmol L−1 with a low detection limit of 0.5 nmol L−1 (S/N = 3). More importantly, the well-preserved crystallinity of MWCNTs@UiO-66-NH2 after 80 cycles and after being soaked in different pH aqueous solutions indicates the promising application of this sensor for real samples. Satisfactory recoveries were achieved when this sensor was used to detect lead in real samples. Furthermore, the excellent stability of this composite makes it possible to be employed in other fields, including extreme acidic media. [ABSTRACT FROM AUTHOR]

We describe a sensitive photoelectrochemical (PEC) sensor for the determination of the herbicide clethodim. The PEC sensor was constructed by using amino-MIL-125/TiO (MIL stands for Materials from Institute Lavoisier), an amino-functionalized metal-organic framework (MOF) modified with TiO. The amino-MIL-125/TiO was synthesized by a simple one-step solvothermal method and placed on a glassy carbon electrode where it displays photoelectrocatalytic activity. Scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy and X-ray diffractometry (XRD) were used to characterize the amino-MIL-125/TiO. In the sensing process, amino-MIL-125/TiO is illuminated by visible light to produce electrons. These excited electrons are delivered to the glassy carbon electrode, leaving positively charged holes (h) on the surface of the amino-MIL-125/TiO. The holes react with HO to generate hydroxy radicals (•OH). Clethodim rapidly attacks the hydroxy radicals and improves the efficiency of charge separation, this leading to an enhanced photocurrent. Under the optimal experimental conditions, this photoelectrochemical method enables clethodim to be quantified in the concentration range from 0.2 to 25 μmol L, with a detection limit (3 S/N) of 10 nmol L. The assay was applied to the determination of clethodim in soil samples, and results were in acceptable agreement with data obtained by liquid chromatography/mass spectrometry. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

We report on the synthesis of FeO-functionalized metal-organic framework (m-MOF) composite from Zn(II) and 2-aminoterephthalic acid by a hydrothermal reaction. The magnetic composite is iso-reticular and was characterized by FTIR, X-ray diffraction, SEM, magnetization, and TGA. The m-MOF was then applied as a sorbent for the solid-phase extraction of trace levels of copper ions with subsequent quantification by electrothermal AAS. The amount of sorbent applied, the pH of the sample solution, extraction time, eluent concentration and volume, and desorption time were optimized. Under the optimum conditions, the enrichment factor is 50, and the sorption capacity of the material is 2.4 mg g. The calibration plot is linear over the 0.1 to 10 μg L Cu(II) concentration range, the relative standard deviation is 0.4 % at a level of 0.1 μg L (for n = 10), and the detection limit is as low as 73 ng L. We consider this magnetic MOF composite to be a promising and highly efficient material for the preconcentration of metal ions. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

A photoelectrochemical (PEC) sensor was constructed for the detection of non-electroactive malathion. It is based on the use of a hierarchical CuO material derived from a Cu-BTC metal-organic framework (where BTC stands for benzene-1,3,5-tricarboxylic acid). The modified CuO was obtained by calcination of Cu-BTC at a high temperature (300 °C) and possesses a high photocurrent conversion efficiency. Under irradiation with visible light and in the presence of malathion, the formation of the CuO-malathion complex on the CuO gave rise to an increase in steric hindrance. This results in a decrease in photocurrent. This novel PEC detection method has a lower detection limit of 8.6 × 10−11 mol L−1 and a wide linear range (1.0 × 10−10 ~ 1.0 × 10−5 mol L−1). [ABSTRACT FROM AUTHOR]

A facile and efficient synthesis of hemin containing metal–organic framework (MOF) nanocomposite was reported. Two dimensional (2D) Ni–MOF nanosheets have been used as a new type of matrix material to immobilize hemin. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS)–mapping, thermal gravity analysis (TGA) suggest the hemin is uniformly distributed in the Ni–MOF nanosheets. Ultraviolet–visible spectroscopy (UV–vis) analysis shows that hemin molecules are combined with MOFs nanosheets through π–π interaction. Electrochemical study indicates the Ni–MOFs/Hemin nanocomposite exhibits high electro–catalytic activities for H 2 O 2 reduction and the biosensor offers high performance with a low detection limit of 0.2 μM and a wide linear range of 1 μM–0.4 mM. Furthermore, the Ni–MOFs/Hemin nanocomposite based biosensor displays high selectivity and stability owing to the protective effect of the 2D MOF nanosheets. More importantly, the biosensor was used to determine the H 2 O 2 levels in human serum and disinfectant samples with satisfactory results. [ABSTRACT FROM AUTHOR]

[Display omitted] • An ultrasensitive DBP PEC sensor was developed based on dual recognition mechanism. • MOF and Cu 2 O hybrid was combined with aptamer and MIP to improve the sensitivity. • This sensor showed a very wide linear range and an extremely low detection limit. • The new sensor has been successfully applied to DBP detection in real samples. Dibutyl phthalate (DBP) is one of the main phthalate plasticizer pollutants in the environment, which can seriously affect the endocrine and immune systems of animals and plants, and raise the risk of cancer, mutagenesis, reproductive malformation and other diseases. The present work aimed to develop a simple, rapid and ultrasensitive photoelectrochemical (PEC) sensor for DBP detection. By incorporating aptamer recognition mechanism with molecular imprinted technology (MIT), a dual identification strategy was proposed based on metal organic framework (MOF) and Cu 2 O heterostructure, which was synthesized in situ by electrodeposition and a simple immersion method. Specially, the novel PEC sensor was exploited by controllable self-polymerization of dopamine with the complex formed by Aptamer [DBP] and DBP incubation on the surface of Cu 3 (BTC) 2 /Cu 2 O/ITO. Owing to the strong light adsorption ability, good stability and enhanced photocurrent of Cu 3 (BTC) 2 /Cu 2 O hybrid under visible light irradiation, and also to the double recognition mechanism of aptamer and MIT, the PEC sensor exhibited highly specific determination of DBP. Under optimal experimental conditions, the designed sensor achieved a linear range from 0.1 pM to 1.0 nM and an extremely low detection limit of 0.035 pM. Moreover, it showed good reliability and practicability in real samples assay. This study extended the development of PEC sensor in plasticizer contaminant detection. [ABSTRACT FROM AUTHOR]

Ultrasensitive determination of tumor marker (TM) is of great significance in cancer prevention and diagnosis. Traditional TM detection methods involve large instrumentation and professional manipulation, which complicate the assay procedures and increase the cost of investment. To resolve these problems, an integrated electrochemical immunosensor based on the flexible polydimethylsiloxane/gold (PDMS/Au) film with Fe–Co metal-organic framework (Fe–Co MOF) as a signal amplifier was fabricated for ultrasensitive determination of alpha fetoprotein (AFP). First, gold layer was deposited on the hydrophilic PDMS film to form the flexible three-electrode system, and then the thiolated aptamer for AFP was immobilized. Afterward, the aminated Fe–Co MOF possessing high peroxidase-like activity and large specific surface area was prepared by a facile solvothermal method, and subsequently the biofunctionalized MOF could effectively capture biotin antibody (Ab) to form MOF-Ab as a signal probe and amplify the electrochemical signal remarkably, thereby realizing highly sensitive detection of AFP with a wide linear range of 0.01–300 ng/mL and a low detection limit of 0.71 pg/mL. In addition, the PDMS based-immunosensor showed good accuracy for assaying of AFP in clinical serum samples. The integrated and flexible electrochemical immunosensor based on the Fe–Co MOF as a signal amplifier demonstrates great potential for application in the personalized point-of-care (POC) clinical diagnosis. [ABSTRACT FROM AUTHOR]

The quantitative detection of tumor biomarkers (TMs) is of great importance in clinical cancer diagnosis and curative effect evaluation. Conventional TM detection methods require bulky equipment and well-trained personnel, resulting in high complexity and cost for diagnostics. To resolve these issues, a paper-based electrochemical immunosensor device coupled with a Ni-Co metal-organic framework (Ni-Co MOF) as a peroxidase mimic was constructed for the label-free detection of alpha-fetoprotein (AFP). First, aminated Ni-Co MOF nanosheets were synthesized by a facile solvothermal method, and then carbon nanotubes and streptavidin-functionalized Ni-Co MOF were successively modified onto a graphene nanosheet-printed polyethylene terephthalate (GNP) electrode. The Ni-Co MOF provided a large specific surface area for capturing the biotin-antibody of AFP efficiently. Afterward, a prepared three-electrode system was assembled with patterned paper to fabricate a highly integrated paper-based electrochemical immunosensor for AFP. Due to the remarkable peroxidase-like activity of the Ni-Co MOF, it was found to amplify the electrode signal obviously. After the formation of the immune complex, the catalytic activity of the MOF was greatly inhibited and led to a reduced current signal, and the highly sensitive and selective detection of AFP with a linear range of 1–200 ng/mL and a detection limit of 0.3 ng/mL was realized. The integrated paper-based immunosensor based on a Ni-Co MOF peroxidase mimic shows great application potential in the personalized point-of-care diagnosis of disease. • Paper-based electrochemical immunosensor for point-of-care (POC) detection of AFP. • Peroxidase-like activity Ni-Co MOF/CNT/GNP electrode used as working electrode. • Prepared three-electrode was assembled with patterned paper to fabricate device. • The high peroxidase-like activity of Ni-Co MOF amplify electrode signal obviously. • The immunosensor realize highly sensitive and selective detection of AFP. [ABSTRACT FROM AUTHOR]

A novel magnetic metal organic frameworks adsorbent modified with mercapto groups was synthesized and developed for extraction and spectrophotometric determination of trace lead. The adsorbent was characterized by Fourier transforms infrared spectrometer, X-ray diffraction, scanning electron microscopy and vibrating sample magnetometry. The results indicated the adsorbents exhibited high adsorption capacities for lead due to the chelation mechanism between metal cations and mercapto groups. Meanwhile, the lead sorption onto the adsorbents could be easily separated from aqueous solution using a magnetic separation method. Under the optimal conditions, a linear calibration curve in the range from 1 to 20 μg L −1 was achieved with an enrichment factor of 100. The limits of detection and quantitation for lead were found to be 0.29 and 0.97 μg L −1 , respectively. The developed method was successfully applied to the determination of trace amounts of lead in food samples and certified reference material with satisfactory results. [ABSTRACT FROM AUTHOR]

A novel solid-phase extraction sorbent, metal-organic frameworks and graphite oxide hybrid composite, was prepared by a solvothermal technique. The morphology and properties of the resultant material were examined by Fourier transform infrared spectroscopy, X-ray diffraction and field emission scanning electron microscopy. To evaluate the extraction performance of the resultant sorbent, luteolin was chosen as a model analyte. The extraction conditions were optimized. Based on these, a convenient and efficient solid-phase extraction procedure for the determination of luteolin was established and the subsequent quantification step was performed by square wave anodic stripping voltammetry. Under the optimal conditions, the oxidation current increased linearly with increasing the concentration of luteolin in the range of 5.0Ã?10−9–5.0Ã?10−7 molL−1 with a correlation coefficient of 0.9983 and a detection limit of 7.9Ã?10−10 molL−1. The relative standard deviation of seven successive scans was 4.20% for 5.0Ã?10−8 molL−1 luteolin. This work not only proposes a useful method for sample pretreatment, but also reveals the great potential of metal-organic frameworks based hybrid materials as an excellent sorbent in solid-phase extraction. [ABSTRACT FROM AUTHOR]

Abstract: Metal–organic framework (MOF) is a relatively new group of interesting materials for specific electrochemical sensing because of its electrocatalytic activity and large surface area. Here, a Zn4O(BDC)3 (MOF-5; BDC2− =1,4-benzenedicarboxylate) modified carbon paste electrode for lead detection was developed. The electroanalytical procedure comprised two steps: chemical accumulation of the adsorbed metal ions at the modified electrode surface, followed by electrochemical detection of the pre-concentrated species using differential pulse stripping voltammetry. It was found that the MOF-5 was capable of adsorbing lead ions from aqueous solutions and could determine the ions prominently at optimum experimental conditions. Many important parameters to acquire the best electrochemical response were carried out, including the amount of MOF-5, different electrolyte solutions, pH, deposition potential, deposition time, and interferences due to other ions. Finally, a calibration graph was obtained with a linear range from 1.0×10−8 to 1.0×10−6 molL−1 (R 2 =0.9981) and detection limit was found to be 4.9×10−9 molL−1. The relative standard deviation (for n =11) was 3.4% at 1.0×10−7 molL−1 of lead level. The proposed method was used for the determination of lead in the real water samples and standard reference materials. [Copyright &y& Elsevier]