Bifunctional oxidase-peroxidase mimicking Fe-Ce MOF on paper-based analytical devices to intensify luminol chemiluminescence: Application for measuring different sugars with a smartphone readout.

This study presents a potent paper-based analytical device (PAD) for quantifying various sugars using an innovative bi-nanozyme made from a 2-dimensional Fe/Ce metal-organic framework (FeCe-BTC). The MOF showed excellent bifunctional peroxidase-oxidase activities, efficiently catalyzing luminol's chemiluminescence (CL) reaction. As a peroxidase-like nanozyme, FeCe-BTC could facilitate the dissociation of hydrogen peroxide (H2O2) into hydroxyl radicals, which then oxidize luminol. Additionally, it was also discovered that when reacting with H2O2, the MOF turns into a mixed-valence MOF, and acts as an oxidase nanozyme. This activity is caused by the generated Ce4+ ions in the structure of MOF that can directly oxidize luminol. The MOF was directly synthesized on the PAD and cascaded with specific natural enzymes to establish simple, rapid, and selective CL sensors for the measurement of different sugars. A cell phone was also used to record light intensities, which were then correlated to the analyte concentration. The designed PAD showed a wide linear range of 0.1-10 mM for glucose, fructose, and sucrose, with detection limits of 0.03, 0.04, and 0.04 mM, respectively. It showed satisfactory results in food and biological samples with recovery values ranging from 95.8 to 102.4 %, which makes it a promising candidate for point-of-care (POC) testing for food control and medicinal purposes.

AuNRs attached TiO2 NPs modified by cobalt-imidazolate frameworks as exceptional materials to improve the energy conversion efficiency of dye-sensitized solar cells.

This work reports a significant improvement in both the open-circuit voltage (VOC) and current density (J) of dye-sensitized solar cells (DSSCs) using gold nanorod-modified TiO2 nanoparticles (TiO2/AuNRs) together with a cobalt-imidazolate framework (ZIF-67) as an efficient photoanode. It was demonstrated that adding ZIF-67 (8 wt%) to TiO2 NPs increased the VOC by 160 mV and J by 2.5 times. This observation was described based on the significant increase in the amount of adsorbed dye in the presence of highly porous ZIF-67, which boosts the photoanode's light harvesting. Modifying TiO2 NPs with AuNRs also caused a remarkable enhancement in J (∼ 2.8 times), which can be explained via electron transfer between the TiO2 conduction band and AuNRs. It can result in a more efficient inhibiting effect on the interfacial charge recombination processes in TiO2/AuNRs/ZIF-67 because of the formation of a Schottky barrier at the interface between TiO2 and Au. These effects were confirmed by the reduction in the photoluminescence intensity of TiO2 in the presence of AuNRs. More reduction in the photoluminescence intensity was observed when ZIF-67 was added. The prepared photoanode showed an outstanding improvement in the overall efficiency of the DSSC (η) to 8.38% compared to the bare TiO2-based photoanode (1.83%). The notable improvement in the TiO2/AuNRs/ZIF-67 performance confirmed its practicality for high-efficiency DSSCs.

Novel amino-functionalized magnetic metal-organic framework/layered double hydroxide adsorbent for microfluidic solid phase extraction: Application for vitamin D3.

Vitamin D deficiency is highly prevalent worldwide, especially with limited sun exposure and sun avoidance. Thus, reliable monitoring of vitamin D levels in food and biological samples is vital for medicinal diagnosis. Herein, a potent method for the extraction and determination of vitamin D3 is presented using a microchip-based solid-phase extraction (SPE) device followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) detection. A new magnetic adsorbent based on Fe3O4 magnetic nanoparticles (MNPs) modified ZnFe layered double hydroxide (LDH)/2-aminoterephthalic acid-Zn2+ metal-organic framework (IRMOF-3) composite (IRMOF-3@MLDH) was successfully synthesized and fixed inside a rectangular micro-column (4 × 2 × 12 mm). The porous structure and high surface area of IRMOF-3@MLDH provide abundant adsorbing sites and make it a potent SPE adsorbent, with an exceptional ability to retain vitamin D3. The adsorption isotherm showed that the composite was highly efficient at extracting vitamin D3 with an extraction capacity of 126 mg g-1. The designed extraction microchip simplified the SPE process, paving the way for automated SPE systems. The developed method presented a broad linear range of 5-2000 ng mL-1, with a detection limit of 1.4 ng mL-1. In comparison to conventional silica-based adsorbents, a higher sensitivity was obtained in the determination of vitamin D3 using the IRMOF-3@MLDH adsorbent. The selectivity of the method was also satisfactory, enabling the measurement of vitamin D3 in food and blood samples with high recovery values in the range from 95.2 to 101%. Thus, the newly developed adsorbent and method offer an efficient alternative to the commonly used C18-based approach.

On paper synthesis of multifunctional CeO2 nanoparticles@Fe-MOF composite as a multi-enzyme cascade platform for multiplex colorimetric detection of glucose, fructose, sucrose, and maltose.

This study reports an economical and portable point-of-care (POC) monitoring device based on artificial multi-enzyme cascade systems for multiple detection purposes. The device was made up of a disposable three dimensional microfluidic paper-based analytical device (3D µPAD) with multiple detection zones and a smartphone readout. On-paper synthesis of a multifunctional mimetic composite, based on the CeO2 nanoparticles embedded in the amino-functionalized Fe metal-organic frameworks (CeO2@NH2-MIL-88B(Fe)), for cascade reactions was the main achievement of this work. The 3D µPAD was applied for simultaneous quantification of glucose, fructose, sucrose and maltose, and the detection process consisted of the enzymatic reaction of each sugar by anchored enzymes on the metal-organic frameworks (MOF) and successive oxidation of 3,3',5,5'-tetramethylbenzidine (TMB). Utilizing the new artificial mimicking system improved the color development uniformity and resulted in a reliable detection tool, with excellent detection limits in the range of 20-280 µM. It was directly applied to analyze the sugars levels of human total blood, urine, semen, honey and juice samples with the relative errors of less than 7.7% compared with the HPLC method. The cost-effective and easy-to-use µPAD has a great potential to be used in either medical diagnostics or the food industry. Also, it can be considered as a competitive POC method for patients in disadvantaged communities or emergencies.

A handheld 3D-printed microchip for simple integration of the H2O2-producing enzymatic reactions with subsequent chemiluminescence detection: Application for sugars.

Herein, a novel lab-on-a-chip (LoC) device fabricated by 3D printing based on H2O2-producing enzymatic reactions with sensitive chemiluminescence (CL) detection was developed to measure different sugars, including glucose, fructose, sucrose, and maltose, in honey, juice, and rice flour samples. The pumpless microchip included two main parts, separated by new cone-shape blocking valves; part A for sample introduction and subsequent enzymatic reaction, besides the CL reagent (luminol) container, and part B for detection. The specific enzyme(s) were embedded into the pores of the zinc zeolite-imidazole framework (ZIF-8) to improve their storage stability. By opening the valves, H2O2 produced by enzymatic reaction and luminol could flow through the designed channels into the detection zone on part B, where a 2D cobalt-imidazole framework was embedded to improve the luminol-H2O2 CL emission. The obtained signal was proportional to the considered sugar concentration, with the detection limits range of 20-268 µM.

On paper synthesis of metal-organic framework as a chemiluminescence enhancer for estimating the total phenolic content of food samples using a smartphone readout.

Herein, a novel paper-based chemiluminescence (CL) assay is reported using a smartphone readout for on-site and reliable analytical applications. The CL system was based on the high-performance improving effect of cobalt-imidazole metal-organic framework (CoMOF) on luminol-hydrogen peroxide (H2O2) CL emission. The CoMOF was grown on paper and used as a support for the CL reaction, which led to an intense CL emission and good reproducibility. More importantly, the stability of luminol, as the CL reagent, was greatly improved in the presence of CoMOF. This high stability, along with the high-yield CL emission, makes the device highly suitable for commercialization. Furthermore, using a smartphone as the detector for the developed device made the process easier and more accessible for public usage. In this work, the new paper-based CL smartphone device was used for the detection of the total phenolic content of food samples. Phenolic compounds (PC) are hydroxyl radical scavengers that can effectively quench the CL emission of the luminol-H2O2-CoMOF system. After optimizing the reaction conditions, the system could detect PC at the µg mL-1 level. Detection limits of 0.12, 0.28, 0.46, 0.85, and 1.23 µg mL-1 were obtained for gallic acid, quercetin, catechin, kaempferol, and caffeic acid, respectively. This work is the first report on the practical application of smartphone CL assays for the estimation of PC. The proposed assay is an easy-to-use, low-cost, portable, and suitable assay for on-site screening purposes.

Magnetic zinc based 2D-metal organic framework as an efficient adsorbent for simultaneous determination of fluoroquinolones using 3D printed microchip and liquid chromatography tandem mass spectrometry.

Herein, a two dimensional metal-organic framework (2D MOF) is introduced as an efficient adsorbent for simultaneously extraction of fluoroquinolones (FQs) from milk samples. The proposed MOF was synthesized by solvothermal method. The high surface area and high accessible sites of prepared MOF offered a unique adsorbent for solid phase extraction (SPE). The experiments showed the great ability of 2D MOF for the retention of ofloxacin (OF), ciprofloxacin (CIP) and norfloxacin (NOR). It was also found that acetic acid (ACA) solution can effectively elute the adsorbed FQs with a high recovery, eliminating the need for other toxic organic elution solvents, which are utilized for the common C18 cartridges. A 3D printed microchip containing a microcolumn was also examined for the SPE process using magnetic composite of 2D MOF, which was fix inside the column using simple magnet. The extracted analytes were gathered to be analyzed by high performance liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS), as the potent detection system. The results demonstrated the great ability of MOF toward the extraction of tested FQs with a breakdown point of 1200 ng mL-1 for each analyte in their mixed solution. The method showed an acceptable selectivity toward the FQs and no interfering effect was observed by other compounds. It was able to detect OF, NOR and CIP in the range of 0.5-1000 ng mL-1 in milk samples and the detection limits were 0.012, 0.009 and 0.016 ng mL-1, respectively.

Simultaneous determination of total phenolic acids and total flavonoids in tea and honey samples using an integrated lab on a chip device.

A microfluidic device for simultaneous analysis of total flavonoids and total phenolic acids is presented for the first time. The process was based on the utilization of magnetic zinc-imidazole frameworks (ZIF-4), as a highly efficient media for on-line separation of phenolic acids and flavonoids, which were subsequently detected by a sensitive chemiluminescence (CL) method. Acrylate-based polymeric microchips containing a separation column (12.5 mm length, 3 mm width and 1 mm depth) were fabricated using a 3D-printer, and magnetic ZIF-4 was fixed into the column. The high porosity of the magnetic ZIF-4 made it a suitable adsorbent, guaranteeing an effective separation. The detection limits were in the range of 0.04-0.10 µg mL-1 with relative standard deviation values of (2.19-4.38%). The system was successfully applied for the analysis of flavonoids and phenolic acids in tea and honey samples. The recovery was from 95.4 to 104.1%, indicating a good accuracy of the developed method.

Application of surface molecular imprinted magnetic graphene oxide and high performance mimetic behavior of bi-metal ZnCo MOF for determination of atropine in human serum.

Herein, high performance peroxidase-like activity of zinc and cobalt bi-metal metal-organic framework (ZnCo MOF) is reported and applied for the sensitive measurement of atropine. ZnCo MOF was synthesized by the reaction of 2-methylimidazole with Zn and Co (II) cations in aqueous media. The colorimetric and fluorometric experiments were applied to investigate the catalytic activity of obtained MOF, using o-phenylenediamine (OPD) and terephthalic acid (TA) peroxidase substrates, respectively. The results demonstrated the more efficient mimetic behavior of ZnCo MOF compared with common Zn or Co MOFs. Besides, it was found that atropine hindered the catalytic action of ZnCo MOF and this effect was intensified by increasing the atropine concentration. So, it was considered to design a sensitive analytical assay for atropine detection. To assure a high specific recognition, molecularly imprinted polymer (MIP)-based extraction using magnetic graphene oxide supports was applied to extract atropine before its determination. The combination between the high specific extraction and great catalytic activity of ZnCo MOF led to the ultrasensitive and reliable determination of atropine. The best linear range of calibration graph was achieved using fluorometric detection system for 0.1-45 ng mL-1 atropine concentrations, and detection limit (3Sb/m) was 27 pg mL-1. The relative standard deviations (RSD %) for the determination of 1, and 10 ng mL-1 atropine (n = 5) were 2.13% and 3.08%, respectively. The explained fluorometric assay was examined for the measurement of atropine in biological fluids (Recoveries were in the range of 95.90-103.57%), and the results were validated by an official method.

Synthesis of g-C3N4@CuMOFs nanocomposite with superior peroxidase mimetic activity for the fluorometric measurement of glucose.

Herein, a novel metal-organic framework (MOF) based nanocomposite with efficient catalytic behavior is reported including flake-like copper (II) MOF (CuMOF) and graphitic C3N4 nanosheets (g-C3N4). The g-C3N4@MOF nanocomposite was simply prepared by solvothermal synthesis of CuMOF in the presence of g-C3N4. The characterization analyses using scanning electron microscopy (SEM), X-ray diffractometry (XRD) and some other techniques demonstrated a nano-porous flake-like structure for the synthesized CuMOF, which enveloped the g-C3N4 nanosheets. Furthermore, the investigation of catalytic behavior of synthesized nanomaterial was implemented on H2O2 based reactions. The fluorometric and colorimetric experimentations illustrated that the accompanying of g-C3N4 with CuMOF had a remarkable positive effect on the catalytic behavior of obtained g-C3N4@MOF. This effect was described based on the improved affinity of nanocomposite to adsorb H2O2 and also synergistic action of its components on the dissociation of H2O2 to hydroxyl radicals. Finally, the analytical application of high catalytic activity of new g-C3N4@MOF was designed for the rapid and simple measurement of glucose in blood. After the enzymatic oxidation of glucose, the fluorometric method was applied for the analysis of produced H2O2 using terephthalic acid as peroxidase substrate. The system led to the ultrasensitive glucose determination in the concentration range of 0.1-22 µM, with a detection limit (3S/m) of 59 nM.

Sensitive biosensing of organophosphate pesticides using enzyme mimics of magnetic ZIF-8.

Development of a sensitive detection method for the reliable screening of widely used organophosphorus (OP) toxins is a crucial request to control their side-effects. Herein, a novel fluorometric assay based on the acetylcholinesterase (AChE) inhibited enzymatic activity and the new peroxidase-like Fe3O4 nanoparticles@ZIF-8 composite (Fe3O4 NPs@ZIF-8) was developed for the determination of OPs. Magnetic Fe3O4 NPs were encapsulated into ZIF-8 and the high mimetic activity of produced composite was assessed on the oxidation of substrates. This observation was applied to the rapid detection of diazinon as a model OP compound. The sensing tool contains AChE and choline oxidase (CHO) enzymes, peroxidase colorimetric or fluorometric substrate, and Fe3O4 NPs@ZIF-8 as the catalyst. In the presence of mimic Fe3O4 NPs@ZIF-8, the generated H2O2 from the enzymatic reactions of acetylcholine is decomposed to hydroxyl radicals. The radicals oxidize the peroxidase substrates to generate a detectable signal. However, due to the inhibition effect of OPs on the enzymatic activity of AChE, lower H2O2 amounts are produced in the presence of diazinon. Using the fluorometric detection system, the generated signal is decreased proportionally by increasing diazinon concentration in the range of 0.5-500 nM. The limit of detection was obtained 0.2 nM. Consequently, the usage of high performance peroxidase-mimic Fe3O4 NPs@ZIF-8 provided a sensitive bio-assay with a potential to be applied as screening tool for toxic OP compounds. The developed assay was successfully applied for the determination of diazinon in water and fruit juices.

Visual detection of peroxide-based explosives using novel mimetic Ag nanoparticle/ZnMOF nanocomposite.

A simple and selective colorimetric method for the detection of perilous peroxide explosives was developed using the peroxidase mimetic activity of silver nanoparticles/flake-like zinc metal-organic framework nanocomposite (Ag@ZnMOF). The synthesis of Ag@ZnMOF contained the formation of silver nanoparticles (AgNPs) inside the fine pores of Zn metal-organic framework (ZnMOF). High reactive AgNPs as well as great surface area of MOFs provided a synergetic and high improved catalytic activity for the composite which was studied as a peroxidase mimic in hydrogen peroxide (H2O2)-based oxidations. The achieved system was used for detection of Triacetone triperoxide (TATP) as one of the most hazardous peroxide explosives. TATP was decomposed in an acidic condition to generate H2O2, which was then applied to oxidize 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of the Ag@ZnMOF as a catalyst. This reaction led to the production of well-known blue colored charge transfer complex (oxTMB), which was recognized by the colorimetric technique. A linear relationship was obtained between the absorption intensity of the produced blue solution and the TATP concentration in the range of 0.4-15 mg L-1, with a detection limit of 0.1 mg L-1. A portable test kit was prepared using the same reagents for TATP measurement in real samples.

Mimetic Ag nanoparticle/Zn-based MOF nanocomposite (AgNPs@ZnMOF) capped with molecularly imprinted polymer for the selective detection of patulin.

Here, Ag nanoparticle/flake-like Zn-based MOF nanocomposite (AgNPs@ZnMOF) with great peroxidase-like activity was applied as an efficient support for molecularly imprinted polymer (MIP) and successfully used for selective determination of patulin. AgNPs@ZnMOF was simply synthesized by creating Ag nanoparticles (Ag NPs) inside the nano-pores of flake-like (Zn)MOF. The high surface area of MOF remarkably improved the catalytic activity of Ag NPs which was assessed by fluorometric, colorimetric and electrochemical techniques. Furthermore, it was observed that patulin could strangely reduce the catalytic activity of AgNPs@ZnMOF, probably due to its electron capturing features. This outcome was the motivation to design an assay for patulin detection. In order to make a selective interaction with patulin molecules, MIP layer was created on the surface of AgNPs@ZnMOF by co-polymerization reaction of 3-aminopropyl triethoxysilane (APTES) and tetraethyl orthosilicate (TEOS) monomers wherein patulin was applied as template agent. Combination between the selective identifying feature of MIP and outstanding peroxidase-like activity of novel AgNPs@ZnMOF nanocomposite as well as the sensitive fluorescence detection system was led to the design of a reliable probe for patulin. The prepared MIP-capped AgNPs@ZnMOF catalyzed the H2O2-terephthalic acid reaction which produced a high florescent product. In the presence of patulin, the fluorescence intensity was decreased proportional to its concentration in the range of 0.1-10µmolL-1 with a detection limit of 0.06µmolL-1. The proposed method was able to selectively measure patulin in a complex media without significant interfering effects from analogue compounds.

The Prevalence of Psychiatric Disorders in Children and Adolescents in Hamadan Province, West of Iran.

BACKGROUND: There are numerous reports regarding increasing childhood and adolescent mental health problems. The aim of this study was to determine the prevalence of psychiatric disorders in Hamadan Province, west of Iran from July 2016 to May 2017. STUDY DESIGN: A cross-sectional study. METHODS: The sample included 1025 Hamadan residents selected using multistage cluster sampling. Psychiatric disorders were assessed by semi-structured psychiatric interview Kiddie-Sads-Present and Lifetime Version (K-SADS-PL). The data were analyzed using the SPSS software. We used the multivariable logistic regression to predict the Odds Ratios (ORs). RESULTS: The prevalence of total psychiatric disorder was 8.6%. Psychiatric disorders in boys were higher than girls (12.6% and 4.9%, respectively). The psychiatric disorders were most prevalent in 6-9 yr old age group (11%). The prevalence of behavioral disorder was 3.8% with attention deficit hyperactivity disorder (ADHD) as the most prevalent case (2.0%). The prevalence of anxiety disorder was 2.8% in which the highest prevalence belonged to separation anxiety disorder (SAD) (1.1%). The prevalence of neurodevelopment disorder was 1.5% with the highest prevalence of 1% observed in epilepsy. The prevalence of mood disorder was 1.1% with the depressive disorder as the most prevalent one (1.0%). The prevalence of enuresis was 2.7%. The most common comorbidities were anxiety and mood disorders 5(50.0%). CONCLUSION: The prevalence of these disorders in Hamadan was less than the prevalence in other cities of Iran. These findings can be helpful for large-scale planning for children and adolescents.

Ultrasensitive and Rapid Determination of Folic Acid Using Ag Nanoparticles Enhanced 1, 10-Phenantroline-Terbium (III) Sensitized Fluorescence.

A novel spectrofluorimetric probe based on Ag nanoparticle (AgNPs)-enhanced terbium (III) (Tb) fluorescence was introduced for the sensitive determination of folic acid (FA). The effect of gold and silver nanoparticles in different size was investigated on the well-known Tb sensitized fluorescence emission of 1, 10-phenantroline (Phen). The greatest fluorescence intensity was observed in the presence of AgNPs with a diameter of ~6 nm maybe due to their highest surface area. Furthermore, it's discovered that FA can form Tb-Phen -FA ternary complexes and cause a notable diminution in this enhanced fluorescence system. Based on this finding, a high sensitive and selective method was developed for the determination of FA. Effects of various parameters like Ag NPs, Phen and Tb(3+) concentration and pH of media were investigated. In the optimum circumstances, the fluorescence emission of AgNPs-Phen-Tb collection was declined linearly by increasing the concentration of FA in the range of 0.5 to 110 nmol L(-1). Limits of detection and quantification were achieved to be 0.21 and 0.62 nmol  L(-1), respectively. The method has good linearity, recovery, reproducibility and sensitivity, and was adequately exploited to follow FA content in pharmaceutical, fortified flour and human urine samples.

Inhibition of Rhodamine B-Ferricyanide Chemiluminescence by Gold Nanoparticles and Sensitive Determination of Hazardous Cyanide.

We describe a new turn off-on chemiluminescence (CL) method for the sensitive and selective determination of cyanide based on the inhibiting effect of gold nanoparticles (AuNPs) on rhodamine B (RohB)-ferricyanide (Fe(CN)6(3-)) reaction. Free RohB can generate strong chemiluminescence emission when oxidized with Fe(CN)6(3-), but undergoes an intense extinction in the presence of AuNPs. Energy transfer and collisions between RohB molecules and AuNPs are probably the reason for this decreasing effect. Furthermore, it was found that CL intensity gradually recovered in the presence of cyanide due to its interaction with the AuNPs. The relation between the decreased CL intensity and cyanide concentration was exploited to develop a method for the determination of cyanide in the 16.7 - 1333 nmol L(-1) concentration range, with a detection limit of 13.6 nmol L(-1). In comparison with other nanoparticle-based methods, the presented assay shows good sensitivity and reliability for the determination of cyanide. The method was satisfactorily applied to the determination of cyanide in environmental and biological samples.