Cu_0.89Zn_0.11O, A New Peroxidase-Mimicking Nanozyme with High Sensitivity for Glucose and Antioxidant Detection

Nanomaterial-based enzyme mimetics (nanozymes) is an emerging field of research that promises to produce alternatives to natural enzymes for a variety of applications. The search for the most cost-effective and efficient inorganic nanomaterials, such as metal oxides, cannot be won by pristine CuO. However, unlike CuO, the Zn-doped CuO (Zn-CuO) nanoparticles reported in this paper reveal superior peroxidase-like enzyme activity. This places Zn-CuO in a good position to participate in a range of activities aimed at developing diverse enzyme applications. The peroxidase-like activity was tested and confirmed against various chromogenic substrates in the presence of H₂O₂ and obeyed the Michaelis–Menten enzymatic pathway. The mechanism of enhanced enzymatic activity was proved by employing terephthalic acid as a fluorescence probe and by electron spin resonance. The nanozyme, when tested for the detection of glucose, showed a substantial enhancement in the detection selectivity. The limit of detection (LOD) was also decreased reaching a limit as low as 0.27 ppm. Such a low LOD has not been reported so far for the metal oxides without any surface modifications. Moreover, the nanozyme (Zn-CuO) was utilized to detect the three antioxidants tannic acid, tartaric acid, and ascorbic acid and the relative strength of their antioxidant capacity was compared

SiO₂ Beads Decorated with SrO Nanoparticles for Biodiesel Production from Waste Cooking Oil Using Microwave Irradiation

Energy sources are necessary for human existence, comfort, and progress. Limited crude petroleum resources and increasing awareness of the environmental impacts of using fossil fuels motivate the search for new energy sources and alternate fuels. Herein, a low cost, fast, and green methodology for the synthesis of a hybrid solid base catalyst, strontium oxide coated millimetric silica beads (SrO@SiO₂), is designed for the transesterification of cooking oil into biodiesel in a domestic microwave oven. The cost reduction is due to the effective utilization of the catalyst by the homogeneous dispersion of the active sites on the silica beads and their reusability. The catalyst synthesis process was optimized with respect to the amount of glass beads, microwave irradiation time, calcination time, and calcination temperature. Several methods for synthesizing SrO by minimizing energy consumption were investigated, and an optimized process for designing SrO@SiO₂ was developed. The SrO@SiO₂ catalyst produced under optimum conditions was characterized by TGA, XRD, FTIR, ICP, SEM, and TEM. XRD analysis indicated peaks typical of SrO alone. ICP analysis indicated 41.3 wt % deposition of SrO on silica beads. The novel solid base catalyst thus generated was used for the transesterification of waste cooking oil. Conversion values as high as 99.4 wt % in 10 s irradiation were observed from ¹H NMR analysis using this composite catalyst, indicating the feasibility of economical biodiesel production from cooking oil waste in a very short time

Preparation of Ge@Organosilicon Core–Shell Structures and Characterization by Solid State NMR and Other Techniques

Many core–shell materials having a protecting outer layer have lately been proposed. In such materials it is not uncommon that chemical or thermal stability issues of the core material are resolved by a proper choice of the shell material. We report here the formation of core–shell structures by pyrolysis of a mixture of tetraethyl germanium and tetramethyl silicon at 750 °C in a simple one-step reaction without the use of catalysts under “RAPET” conditions. The composite product, germanium–core/organosilicon–shell (Ge@Organosilicon), is formed in two morphologies, rods and spheroids. The rods radial distribution is rather narrow while the spheroids exhibit a broader distribution due to their tendency to agglomerate. The germanium core phase is crystalline covered by a disordered organosilicon layer. The contribution of each of the precursors to the final product is shown by selected-area EDS and solid state NMR spectroscopy and further corroborated by RAMAN, EPR, and powder X-ray diffraction analysis

Herpes Simplex Virus Type‑1 Attachment Inhibition by Functionalized Graphene Oxide

Graphene oxide and its derivatives have lately been the subject of increased attention in the field of bioscience and biotechnology. In this article, we report on the use of graphene oxide (GO) derivatives to inhibit herpes simplex virus type-1 (HSV-1) infections, mimicking the cell surface receptor heparan sulfate, and the GO derivatives compete with the latter in binding HSV-1. The inhibition does not affect cell-to-cell spreading. Media content has a significant effect on the inhibition properties of the nanomaterials. These have no cytotoxic effect, suggesting that this is a promising approach for the development of antiviral surfaces and for diagnostic purposes

Antiparasitic Ointment Based on a Biocompatibile Carbon Dot Nanocomposite

Toward the development of emerging drugs with high efficacy, nontoxicity, and low drug resistance against Leishmaniasis, this study unravels the potential of carbon dots (CDs) and gallium-doped carbon dots (Ga@CDs). These nanoscale materials ranging in size from 4 to 7 nm prepared by ultrasonication without a catalyst were well dispersed in a commercial ointment. The formulated ointments with CDs and Ga@CDs exhibited higher activity against both <i>Leishmania</i> species, with a minimal concentration of 30 μg/mL for CDs/Ga@CDs, compared with a commercial counterpart. CDs were virtually nontoxic, as attested by in vitro and in vivo experimental data using mice and healthy cells. The “killing” mechanism could be attributed to the leakage of Na and K, whereas for lysosomal bursting and depolarization of mitochondria, ion leakage was ruled out. The ointments could be considered as a new class of emerging drugs to combat Leishmaniasis, a deadly disease that still infects several million people worldwide, especially in Asia and South America

Ruthenium Phosphide Synthesis and Electroactivity toward Oxygen Reduction in Acid Solutions

Ruthenium phosphides are known to be highly stable and conductive materials. A new process was developed to prepare ruthenium phosphide catalysts for oxygen reduction in acid solutions. Several synthesis methods have been applied to form pure RuP and Ru₂P as well as mixed phases of Ru and Ru_<i>x</i>P (<i>x</i> ≥ 1). These methods utilize high-temperature solid-state synthesis and reaction under autogenic pressure at elevated temperature (RAPET). On the basis of rotating ring–disk electrode (RRDE) experiments, oxygen reduction activity was observed on all Ru_<i>x</i>P materials. Characteristic kinetic parameters show specific exchange current densities in the range of 0.4–1.4 mA mg^–1, Tafel slopes of 129–135 mV dec^–1, and %H₂O₂ of 3–11% of the total current. Complementary XPS and Raman spectral analysis reveals a highly oxidized surface with significant presence of PO₄^3– and RuO₂ species. To the best of our knowledge, this is the first report identifying oxygen reduction activity on Ru_<i>x</i>P

Accelerated Bone Regeneration by Nitrogen-Doped Carbon Dots Functionalized with Hydroxyapatite Nanoparticles

We investigated the osteogenic potential of nitrogen-doped carbon dots (NCDs) conjugated with hydroxyapatite (HA) nanoparticles on the MC3T3-E1 osteoblast cell functions and in a zebrafish (ZF) jawbone regeneration (JBR) model. The NCDs–HA nanoparticles were fabricated by a hydrothermal cum co-precipitation technique. The surface structures of NCDs–HA nanoparticles were characterized by X-ray diffraction; Fourier transform infrared (FTIR), UV–vis, and laser fluorescence spectroscopies; and scanning electron microscopy, transmission electron microscopy (TEM), energy-dispersive spectrometry (EDS), and NMR analyses. The TEM data confirmed that the NCDs are well conjugated on the HA nanoparticle surfaces. The fluorescent spectroscopy results indicated that the NCDs–HA exhibited promising luminescent emission in vitro. Finally, we validated the chemical structure of NCDs–HA nanoparticles on the basis of FTIR, EDS, and ³¹P NMR analysis and observed that NCDs are bound with HA by electrostatic interaction and H-bonding. Cell proliferation assay, alkaline phosphatase, and Alizarin red staining were used to confirm the effect of NCDs–HA nanoparticles on MC3T3-E1 osteoblast proliferation, differentiation, and mineralization, respectively. Reverse transcriptase polymerase chain reaction was used to measure the expression of the osteogenic genes like runt-related transcription factor 2, alkaline phosphatase, and osteocalcin. ZF-JBR model was used to confirm the effect of NCDs–HA nanoparticles on bone regeneration. NCDs–HA nanoparticles demonstrated cell imaging ability, enhanced alkaline phosphatase activity, mineralization, and expression of the osteogenic genes in osteoblast cells, indicating possible theranostic function. Further, NCDs–HA nanoparticles significantly enhanced ZF bone regeneration and mineral density compared to HA nanoparticles, indicating a therapeutic potential of NCDs–HA nanoparticles in bone regeneration and fracture healing

Exceptionally Active and Stable Spinel Nickel Manganese Oxide Electrocatalysts for Urea Oxidation Reaction

Spinel nickel manganese oxides, widely used materials in the lithium ion battery high voltage cathode, were studied in urea oxidation catalysis. NiMn₂O₄, Ni_1.5Mn_1.5O₄, and MnNi₂O₄ were synthesized by a simple template-free hydrothermal route followed by a thermal treatment in air at 800 °C. Rietveld analysis performed on nonstoichiometric nickel manganese oxide-Ni_1.5Mn_1.5O₄ revealed the presence of three mixed phases: two spinel phases with different lattice parameters and NiO unlike the other two spinels NiMn₂O₄ and MnNi₂O₄. The electroactivity of nickel manganese oxide materials toward the oxidation of urea in alkaline solution is evaluated using cyclic voltammetric measurements. Ni_1.5Mn_1.5O₄ exhibits excellent redox characteristics and lower charge transfer resistances in comparison with other compositions of nickel manganese oxides and nickel oxide prepared under similar conditions.The Ni_1.5Mn_1.5O₄modified electrode oxidizes urea at 0.29 V versus Ag/AgCl with a corresponding current density of 6.9 mA cm^–2. At a low catalyst loading of 50 μg cm^–2, the urea oxidation current density of Ni_1.5Mn_1.5O₄ in alkaline solution is 7 times higher than that of nickel oxide and 4 times higher than that of NiMn₂O₄ and MnNi₂O₄, respectively

Evaluation of the Potential of Chlorella vulgaris for Bioethanol Production

For bioethanol to be a sustainable transportation fuel, appropriate feedstock needs to be established. The focus of the current work is to evaluate if the microalga Chlorella vulgaris could be the feedstock of choice. Exclusive formation of glucose was observed upon the acid (HCl) hydrolysis of C. vulgaris. Microwave irradiation as well as hydrothermal reaction were employed as heating methods. Under optimal hydrolysis conditions using microwave irradiation (100 °C, 1 M HCl, and 10 min), the glucose yield was 20 ± 3.5 wt % compared to 23 ± 4 wt % under the optimal hydrothermal reaction conditions (120 °C, 1 M HCl, and 60 min). The hydrothermal-based hydrolysis process was further scaled up from a 0.2 g batch to a 2.0 g batch, and the glucose obtained was converted to bioethanol in a fermentation process at 30 °C for 28 h using Saccharomyces cerevisiae. An ethanol yield as high as 13.2 ± 0.5 wt % was obtained from C. vulgaris