Construction of a biointerface for glucose oxidase through diazonium chemistry and electrostatic self-assembly technique

In this study, a new procedure for the fabrication of biosensors was developed. The method is based on the covalent attachment of nitrophenyl groups to the electrode surface via diazonium salt reaction followed by their conversion to amine moieties through electrochemical reduction and electrostatic layer-by-layer (LbL) assembly technique. In this procedure, highly stable iron oxide (Fe₃O₄) nanoparticles (IONPs), chitosan (CHIt), GOx, and Nile blue (NB) were assembled on the surface of aminophenyl modified glassy carbon electrode (AP/GCE) by LbL assembly technique. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to characterize the interfaces. The surface coverage of the active GOx and Michaelis–Menten constant (K _M) of the immobilized GOx were Γ?=?3.38?×?10^?11 mol cm^?2 and 2.54 mM, respectively. The developed biosensor displayed a well-defined amperometric response for glucose determination with high sensitivity (8.07 μA mM^?1) and low limit of detection (LOD) of 19.0 μM. The proposed approach allows simple biointerface regeneration by increasing pH which causes disruption of the ionic interactions and release of the electrostatic attached layers. The biosensor can then be reconstructed again using fresh enzyme. Simple preparation, good chemical and mechanical stabilities, and easy surface renewal are remarkable advantages of the proposed biosensor fabrication procedure.     

Natural radioactivity measurements in Pahang State,Malaysia

This study was aimed at providing the baseline data of terrestrial gamma dose rates and natural radioactivity to assess the corresponding health risk in the ambient environment of the Pahang State. Terrestrial gamma radiation (TGR) from 640 locations was measured with the mean value found to be 176?±?5 nGy h^?1. Ninety-eight soil samples were analysed using a high-purity germanium detector (HPGe), and the mean concentrations of the radionuclides ²²⁶Ra, ²³²Th and ⁴⁰K are 110?±?3, 151?±?5 and 542?±?51 Bq kg^?1, respectively.²²⁶Ra and ²³²Th concentrations were found to be three times the world average, while that of ⁴⁰K is quite higher than the world average value. The acid-intrusive geological formation has the highest mean concentrations for ²²⁶Ra (215?±?6 Bq kg^?1), ²³²Th (384?±?12 Bq kg^?1) and ⁴⁰K (1564?±?153 Bq kg^?1). The radium equivalent activities (Req) and the external hazard index (Hex) for the various soil types were also calculated. Some of the soil types were found to have values exceeding the internationally recommended levels of 370 Bq kg^?1 and the unity value, respectively.     

Real-Time pH-Dependent Self-Assembly of Ionisable Lipids from COVID-19 Vaccines and In Situ Nucleic Acid Complexation

Ionisable amino-lipid is a key component in lipid nanoparticles (LNPs), which plays a crucial role in the encapsulation of RNA molecules, allowing efficient cellular uptake and then releasing RNA from acidic endosomes. Herein, we present direct evidence for the remarkable structural transitions, with decreasing membrane curvature, including from inverse micellar, to inverse hexagonal, to two distinct inverse bicontinuous cubic, and finally to a lamellar phase for the two mainstream COVID-19 vaccine ionisable ALC-0315 and SM-102 lipids, occurring upon gradual acidification as encountered in endosomes. The millisecond kinetic growth of the inverse cubic and hexagonal structures and the evolution of the ordered structural formation upon ionisable lipid-RNA/DNA complexation are quantitatively revealed by in situ synchrotron radiation time-resolved small angle X-ray scattering coupled with rapid flow mixing. We found that the final self-assembled structural identity, and the formation kinetics, were controlled by the ionisable lipid molecular structure, acidic bulk environment, lipid compositions, and nucleic acid molecular structure/size. The implicated link between the inverse membrane curvature of LNP and LNP endosomal escape helps future optimisation of ionisable lipids and LNP engineering for RNA and gene delivery.     

Synthesis, characterization and photophysical properties of benzidine-based compounds

The N-alkylation of the 3,3′-diaminobenzidine with innocent substituents leads to unusual properties. The emission of the benzidine core can be fine-tuned by subtle modifications, and the N-substitution with benzylic groups results in photoinduced exciplexes with distinct and increased emission. This compound constitutes the first example of intramolecular exciplex containing benzidine unit. We also show that these photoinduced processes could be modulated by proton input, and that the diprotonation of the benzidine core disrupted the intramolecular communication in the excited states with a concomitant inhibition of the ligand-centred fluorescence. Furthermore, upon photo-irradiation at 254 nm, semiquinone imine and quinone diimine systems are produced in CH₂Cl₂ of which the photolysis generates Cl radicals, which rapidly oxidize the tetraamine compounds.     

Effect of temperature on the performance of proton batteries based on chitosan–NH4NO3–EC membrane

Membranes of chitosan-based proton conductor polymer electrolyte were prepared by dissolving chitosan powder, ammonium nitrate (NH₄NO₃) salt and ethylene carbonate (EC) plasticizer in acetic acid solution. The temperature dependence of the chitosan-based membrane system was found to obey the Arrhenius relationship. The sample with the highest conductance, 18 wt.% CA + 12 wt.% NH₄NO₃ + 70 wt.% EC (CA40N70E), also possesses the lowest activation energy. From linear sweep voltammetry (LSV) results, the membrane is electrochemically stable at a potential of 1.6–1.8 V and a temperature of 298–353 K. The cells were fabricated using zinc powder (Zn) + zinc sulfate heptahydrate (ZnSO₄·7H₂O) + acetylene black (AB) + polytetrafluoroethylene (PTFE)|CA40N70E|manganese (IV) oxide (MnO₂) + AB + PTFE. The open circuit voltages of the cells are decreases as temperature increases, the same trend as that obtained by LSV. The cell performance is excellent at 333 K, with discharge capacity of 42.7 mAh, internal resistance of 16.8 Ω, maximum power density of 14.6 mW cm⁻² and a short-circuit current density of 31.0 mA cm⁻². However, at temperatures above 333 K, decomposition of the membrane degraded the electrochemical properties of the cells.     

Gas-liquid selective oxidations with oxygen under explosive conditions in a micro-structured reactor

The gas-liquid oxidation of cyclohexane is performed at high temperature (>200 degrees C) and pressure (up to 25 bar) using pure oxygen in a Pyrex capped silicon etched microreactor which allows convenient screen reaction conditions well above the flammability limit.     

Reactivity trends of the base hydrolysis of coumarin and thiocoumarin in binary aqueous-methanol mixtures at different temperatures

Rate constants for base hydrolysis of both coumarin and thiocoumarin have been studied in different binary aqueous-methanol mixtures at temperature range from 288 to 313 K. The activation parameters of the reactions were evaluated. Moreover, the change in the activation barrier of the investigated compounds from water to water-methanol mixtures were estimated from the kinetic data.     

Variation of filamentation phenomenon in strongly magnetized plasma with various discharge parameters

Filamentation phenomenon is one of the most important outcomes of applying a strong magnetic field to low-pressure plasmas and dusty plasmas. In this article, the variation of filamentation phenomenon with neutral gas pressure and plasma density will be investigated using numerical simulations. It will be shown through these simulations how the formation of the filamentary patterns in the magnetized plasma results in a localized electric field structure that strongly contributes to the properties of the filamentary patterns. Based on the results of the simulations, a theoretical model is derived that relates the width of the filamentary patterns to the plasma density. The model has been successfully employed to predict the width of the patterns emerging in various simulations of the magnetized plasma.