Detection of Leptin Using Electrocatalyst Mediated Impedimetric Sensing.

Obesity is a complex disorder associated with immense health consequences including high risk of cardiovascular diseases, diabetes, and cancer. Abnormality in the thyroid gland, genetics, less physical activity, uptake of excessive diet, and leptin resistance are critical factors in the development of obesity. To determine the treatment strategy, understanding the pathophysiology of obesity is crucial. For instances, leptin resistance mediated obesity defined by the presence of excessive leptin hormone (Lep) in the systemic circulation is very common in diet induced obesity. Therefore, our hypothesis is that quantitative measurement of Lep from blood can help to identify individuals with Lep resistant mediated obesity and thereby guide toward a proper treatment strategy. In this work, we aim to utilize an electrochemical immunosensing platform for diagnosis of obesity by measuring the Lep content in systemic circulation. A porous carbon confined FeNi bimetallic system was synthesized with three different ratios of Fe and Ni ions using high temperature pyrolysis technique. The suitability of the sensor for detecting Lep was studied using both CV and EIS techniques. The limit of detection (LOD) for GCE was recorded as 157.4 fg/mL with a wide linear concentration range of 500 fg/mL to 80 ng/mL, while for SPCE the LOD was 184.9 fg/mL with a linear range of 500 fg/mL to 50 ng/mL. Finally, the feasibility and applicability of the sensor for Lep detection was tested with serum collected from high fat diet induced obese rats. The selectivity, sensitivity, storage, and experimental stability and reproducibility tests showed potential for this biosensor platform as a point-of-care Lep detection device.

Controlling the Interfacial Charge Polarization of MOF-Derived 0D-2D vdW Architectures as a Unique Strategy for Bifunctional Oxygen Electrocatalysis.

The design of alternative earth-abundant van der Waals (vdW) nanoheterostructures for bifunctional oxygen evolution/reduction (OER/ORR) electrocatalysis is of paramount importance to fabricate energy-related devices. Herein, we report a simple metal-organic framework (MOF)-derived synthetic strategy to fabricate low-dimensional (LD) nanohybrids formed by zero-dimensional (0D) ZrO2 nanoparticles (NPs) and heteroatom-doped two-dimensional (2D) carbon nanostructures. The 2D platforms controlled the electronic structures of interfacial Zr atoms, thus producing optimized electron polarization for boron and nitrogen-doped carbon (BCN)/ZrO2 nanohybrids. X-ray photoelectron spectroscopy (XPS) and theoretical studies revealed the key role of the synergistic couple effect of boron (B) and nitrogen (N) in interfacial electronic polarization. The BCN/ZrO2 nanohybrid showed excellent bifunctional electrocatalytic activity, delivering an overpotential (η10) of 301 mV to reach a current density of 10 mA-cm-2 for the OER process and a half-wave potential (E1/2) of 0.85 V vs reversible hydrogen electrode (RHE) for the ORR process, which are comparable to the state-of-the-art LD nanohybrids. Furthermore, BCN/ZrO2 also showed competitive performances for water-splitting and zinc-air battery devices. This work establishes a new route to fabricate highly efficient multifunctional electrocatalysts by tuning the electronic polarization properties of 0D-2D electrochemical interfaces.

Tissue paper-derived porous carbon encapsulated transition metal nanoparticles as advanced non-precious catalysts: Carbon-shell influence on the electrocatalytic behaviour.

Porous carbon encapsulated non-precious metal nanocatalysts have recently opened the ways towards the development of high-performance water remediation and energy conversion technologies. Herein, we report a facile, scalable and green synthetic methodology to fabricate porous carbon encapsulated transition metal nanocatalysts (M@TP: M = Cu, Ni, Fe and Co) using commercial tissue paper. The morphology, crystalline structure, chemical composition and textural properties of the M@TP nanocatalysts were thoroughly characterized. The catalytic activity of the M@TP nanocatalysts was investigated for the degradation of Congo red (CR) via peroxymonosulfate activation. Co@TP-6 was found to be the most active catalyst allowing 97.68% degradation in 30 min with a higher rate constant of 0.109 min-1. The nanocatalysts also displayed a carbon shell thickness-dependent electrocatalytic hydrogen evolution reaction (HER) activity, most likely due to the shielding effect of the carbon layers over the electron transfer (ET) processes at the metal core/carbon interfaces. Remarkably, the Ni@TP-6 electrocatalyst, with the smaller carbon shell thickness, showed the best electrocatalytic performance. They delivered an ultralow onset potential of -30 mV vs RHE, an overpotential of 105 mV at a current density of 10 mA·cm-2 and an excellent electrochemical stability to keep the 92% of the initial current applied after 25000 s, which is comparable with the HER activity of the state-of-the-art Ni-based catalysts.

Novel method to achieve crystallinity of calcite by Bacillus subtilis in coupled and non-coupled calcium-carbon sources.

Bacteria mineralization is a promising biotechnological approach to apply in biomaterials development. In this investigation, we demonstrate that Bacillus subtilis 168 induces and influences CaCO3 composites precipitation. Crystals were formed in calcium-carbon non-coupled (glycerol + CaCl2, GLY; or glucose + CaCl2, GLC) and coupled (calcium lactate, LAC; or calcium acetate, ACE) agar-sources, only maintaining the same Ca2+ concentration. The mineralized colonies showed variations in morphology, size, and crystallinity form properties. The crystals presented spherulitic growth in all conditions, and botryoidal shapes in GLC one. Birefringence and diffraction patterns confirmed that all biogenic carbonate crystals (BCC) were organized as calcite. The CaCO3 in BCC was organized as calcite, amorphous calcium carbon (ACC) and organic matter (OM) of biofilm; all of them with relative abundance related to bacteria growth condition. BCC-GLY presented greatest OM composition, while BCC-ACE highest CaCO3 content. Nucleation mechanism and OM content impacted in BCC crystallinity.

Development of photocatalytic paint based on TiO2 and photopolymer resin for the degradation of organic pollutants in water.

While the use of TiO2 nanoparticles in the form of slurry/suspension requires energy-intensive separation processes, its immobilization in solid support may open new opportunities in the area of sustainable water treatment technologies. In this study, a novel method for the development of photocatalytic paint based on TiO2 nanoparticles and acrylate-based photopolymer resin is reported. The paint (TiO2@polymer) was applied on substrates such as plastic petri dish and glass jar, which was polymerized/solidified by ultraviolet light irradiation. The painted petri dish and glass jar were used for the photocatalytic degradation of model organic pollutants viz. methyl orange (MO), methylene blue (MB), and indole in deionized water, simulated fresh drinking water, and tap water matrices. The photocatalytic degradation studies were performed under sunlight and UV-B light were used for. The sunlight-assisted photocatalytic degradation of MO and MB was found to be faster and more efficient than the UV-B light-assisted ones. Under UV-B light irradiation, it took 120 min to degrade about 80% of 6 ppm MB solution, whereas under sunlight irradiation it took 60 min to degrade about 90% of the same MB solution. The photocatalytic paint generated hydroxyl radical (·OH) under the UV-B and sunlight irradiation, which was studied by the terephthalic acid fluorescence tests. Further, the potential release of TiO2 during the exposure to UV irradiation was studied by single particle ICP-MS analysis.

Sucrose-Mediated Fast Synthesis of Zinc Oxide Nanoparticles for the Photocatalytic Degradation of Organic Pollutants in Water.

We report a facile method for the synthesis of zinc oxide nanoparticles (nZnOs) by rapidly heating a paste of zinc nitrate and sucrose on the hot plate at 500 °C. The transmission electron microscopy images revealed the spherical shape of the nZnO with an average size of 35 nm. The band gap and the specific surface area of the nZnO were measured to be about 3.32 eV and 80.11 m2/g, respectively. The nZnO was utilized for the photocatalytic degradation of methyl orange (MO) and methylene blue (MB) in water under the ultraviolet (UV-B) light and sunlight irradiation. Photocatalysis was performed in two types of water matrices, viz., the deionized water and the simulated fresh drinking water. Almost a complete degradation of MO and MB was obtained within 30 min of UV-B light irradiation. Under sunlight irradiation, more than 95% of the MO solution underwent degradation within 30 min. The photocatalytic stability of the nZnO was examined for five cycles, and a similar activity was found throughout the cycles. The photocatalytic generation of the hydroxyl radical (•OH) was confirmed by the terephthalic acid photoluminescence tests. Moreover, the synthesis methodology was validated by triplicating the nZnO synthesis. Every time, the nZnO demonstrated a similar photocatalytic activity, which confirmed the robustness of the synthesis procedure.

Adsorption of methylene blue and tetracycline onto biomass-based material prepared by sulfuric acid reflux.

The adsorptive removal of environmental pollutants is an effective method for the treatment of contaminated water. Thus, the preparation of adsorbents from low-cost, readily available, and renewable resources has garnered immense attention in recent years. In this study, a facile one-step method for the preparation of a high-capacity adsorbent is demonstrated by refluxing pine cones in concentrated sulfuric acid. With sulfuric acid reflux, the pine cones undergone carbonization as well as functionalization with sulfonic acid groups. The adsorbent demonstrated high adsorption capacity for two emerging organic pollutants, methylene blue (MB) and tetracycline (TC). Different variables such as pH, temperature, contact time, and initial concentration of the pollutants were analyzed and showed that the adsorption capacity for MB increased in a basic pH and vice versa for TC. Also, the elevated temperature favored the adsorption for both MB and TC. The maximum adsorption capacity was found to be 1666.66, and 357.14 mg g-1 for MB and TC, respectively. In comparison to the pristine pine cone, the sulfuric acid treated pine cone demonstrated an extraordinary improvement in the adsorption capacity. The adsorption of MB and TC was performed from the tap water matrix and similar adsorption capacities were found. A packed glass column was also prepared to demonstrate the adsorption of MB from tap water under flow conditions.

Inhibition of Urease by Disulfiram, an FDA-Approved Thiol Reagent Used in Humans.

Urease is a nickel-dependent amidohydrolase that catalyses the decomposition of urea into carbamate and ammonia, a reaction that constitutes an important source of nitrogen for bacteria, fungi and plants. It is recognized as a potential antimicrobial target with an impact on medicine, agriculture, and the environment. The list of possible urease inhibitors is continuously increasing, with a special interest in those that interact with and block the flexible active site flap. We show that disulfiram inhibits urease in Citrullus vulgaris (CVU), following a non-competitive mechanism, and may be one of this kind of inhibitors. Disulfiram is a well-known thiol reagent that has been approved by the FDA for treatment of chronic alcoholism. We also found that other thiol reactive compounds (l-captopril and Bithionol) and quercetin inhibits CVU. These inhibitors protect the enzyme against its full inactivation by the thiol-specific reagent Aldrithiol (2,2'-dipyridyl disulphide, DPS), suggesting that the three drugs bind to the same subsite. Enzyme kinetics, competing inhibition experiments, auto-fluorescence binding experiments, and docking suggest that the disulfiram reactive site is Cys592, which has been proposed as a "hinge" located in the flexible active site flap. This study presents the basis for the use of disulfiram as one potential inhibitor to control urease activity.