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In this work, we report the fast and ultrasensitive detection of a nerve agent simulant in the gas phase, diethyl chloro-phosphate (DCP), by using carbazole-based nanofibers from 1. When exposed to trace DCP, the formed pyridine-phosphorylated product in 1 nanofibers can cause amplified ratiometric fluorescence responses, i.e., amplified fluores-cence quenching via quenching excitons within the diffusion length of 1 nanofibers and simultaneously amplified turn-on fluorescence responses via harvesting excitons within the diffusion length to give the intramolecular charge transfer (ICT) emission at a longer wavelength. On the basis of these amplified ratiometric fluorescence responses, detection of DCP with fast response (ca. 3 s), ultrasensitivity (4 ppb), and improved selectivity are achieved.

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Owing to the versatility and biocompatibility, a self-polymerized DA (in presence of air at pH 8.5 tris buffer solution) as a polydopamine (pDA) film has been used for a variety of applications. Indeed, instability under electrified condition (serious surface-fouling) and structural ambiguity of the pDA have been found to be unresolved problems. Previously, pDA films (has hygroscopic and insoluble property) prepared by various controlled chemical oxidation methods have been examined for the structural analysis using ex-situ solid-state NMR and Mass Spectroscopic techniques. In this work, a new in-situ approach has been introduced using an electrochemical quartz crystal microbalance (EQCM) technique for the improved structural elucidation of pDA that has been formed by a controlled electrochemical oxidation of DA on a carboxylic acid functionalized multiwalled carbon nanotube-Nafion (cationic perfluoro polymer) modified electrode (f-MWCNT-Nf) system in pH 7 phosphate buffer solution. Key intermediates like 5,6-dihydroxy indole (DHI; 150.7 g mol-1), dopamine (154.1 g mol-1), Na+, PO42- and polymeric product of high molecular weight, 2475 g mol-1 have been trapped on f-MWCNT-Nf surface via - (sp2 carbon of MWCNT and aromatic e-s), covalent (amide-II bonding, minimal), hydrogen and ionic bonding and identified its molecular weights successfully. The new pDA film system showed well-defined peaks at Eo'= 0.25 V and -0.350 vs Ag/AgCl corresponding to the surface-confined dopamine/dopamine quinone and DHI/5,6-indolequinone redox transitions without any surface-fouling complication. As an electroanalytical application of pDA, selective recognition of Pb2+ ion via {(pDA)-hydroquinone-Pb0} complexation with detection limit (signal-to-noise ratio=3) 840 part-per-trillion has been demonstrated.

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Large scale molecular dynamics simulations for bidisperse nanoparticle suspensions with an explicit solvent are used to investigate the effects of evaporation rates and volume fractions on the nanoparticle distribution during drying. Our results show that “small-on-top” stratification can occur when PesΦs ≥ c with c ∼ 1, where Pes is the Péclet number and Φs is the volume fraction of the smaller particles. This threshold of PesΦs for “small-on-top” is larger by a factor of ~ α2 than the prediction of the model treating solvent as an implicit viscous background, where α is the size ratio between the large and small particles. Our simulations further show that when the evaporation rate of the solvent is reduced, the “small-on-top” stratification can be enhanced, which is not predicted by existing theories. This unexpected behavior is explained with thermophoresis associated with a positive gradient of solvent density caused by evaporative cooling at the liquid-vapor interface. For ultrafast evaporation the gradient is large and drives the nanoparticles toward the liquid/vapor interface. This phoretic effect is stronger for larger nanoparticles and consequently the “small-on-top” stratification becomes more distinct when the evaporation rate is slower (but not too slow such that a uniform distribution of nanoparticles in the drying film is produced), as thermophoresis that favors larger particles on the top is mitigated. A similar effect can lead to “large-on-top” stratification for PesΦs above the threshold when Pes is large but Φs is small. Our results reveal the importance of including the solvent explicitly when modeling evaporation-induced particle separation and organization and point to the important role of density gradients brought about by ultrafast evaporation.

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Small-molecule oxoanions are often imprinted noncovalently as carboxylates into molecularly imprinted polymers (MIPs), requiring the use of an organic counterion. Popular species are either pentamethylpiperidine (PMP) as a protonatable cation or tetraalkylammonium (TXA) ions as permanent cations. The present work explores the influence of the TXA as a function of their alkyl chain length, from methyl to octyl, using UV/vis absorption, fluorescence titrations and HPLC, as well as MD simulations. Protected phenylalanines (Z-L/D-Phe) served as templates/analytes. While the influence of the counterion on the complex stability constants and anion-induced spectral changes shows a monotonous trend with increasing alkyl chain length, already at the prepolymerization stage, the cross-imprinting/rebinding studies showed a unique pattern that suggested the presence of adaptive cavities in the MIP matrix, related to the concept of induced-fit of enzyme-substrate interaction. Larger cavities formed in the presence of larger counterions can take up pairs of Z-X-Phe and smaller TXA, eventually escaping spectroscopic detection. Correlation of the experimental data with the MD simulations revealed that counterion mobility, the relative distances between the three partners, and the hydrogen bond lifetimes are more decisive for the response features observed than actual distances between interacting atoms in a complex or the orientation of binding moieties. TBA has been found to yield the highest imprinting factor, also showing a unique dual behavior regarding the interaction with template and fluorescent monomer. Finally, interesting differences between both enantiomers have been observed in both theory and experiment, suggesting true control of enantioselectivity. The contribution concludes with suggestions for translating the findings into actual MIP development.

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The interfacial free energy of a solid, which determines its adsorption properties, depends on interactions between the surface and the fluid. A change in surface composition can completely change the behaviour of the solid. Decades of work have explored adsorption and its effects at solid-fluid interfaces from the macroscopic perspective and using molecular modelling so the concept of the electric double layer (EDL) is well established in the community. However, direct, molecular level, experimental observations of the composition within the interface region, and its change with time and conditions, is not abundant. We used cryogenic X-ray photoelectron spectroscopy (cryoXPS) to observe the composition in the clay mineral-solution interface region as a function of bulk solution composition, on illite and chlorite in MgCl2 and CaCl2 electrolytes, over a range of concentrations (1-125 mM), in situ, on vitrified samples. These samples were prepared from very thin smears of centrifuged wet paste that were instantaneously chilled to liquid N2 temperature. They preserved the adsorbed solution in its amorphous state, maintaining the location of the ions and water with respect to the solid, without the disruption that occurs during drying, or the rearrangement that results as water crystallises during freezing. With decreasing ionic strength, we could directly monitor the loss of negative charge in the interface region, producing an anion deficiency, as predicted by theory. The Cl-/Me2+ ratio dropped below 1 for chlorite at 12-25 mM MeCl2 and for illite at 75-100 mM. In addition to better understanding of clay mineral behaviour in solution, this work demonstrates that only those clay minerals where surface charge density is the same or lower than for chlorite contribute to a low salinity enhanced oil recovery response (LS EOR). This explains many of the contradictory results from studies about the role of clay minerals in LS EOR.

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Two, cyanine based fluorescent probes L [(E)-2-(4-(diethylamino)-2-hydroxystyryl)-3-ethyl-1,1-dimethyl-1H-benzo[e]indol-3-ium iodide] and L1 [(E)-3-ethyl-1,1-dimethyl-2-(4-nitrostyryl)-1H-benzo[e]indol-3-ium iodide] have been designed and synthesized. Among these two probes; TICT (twisted intramolecular charge transfer) based probe L can preferentially self-assemble to form nanoaggregates. L displayed a selective TURN-ON fluorescence response towards HSA and BSA in ~100% aqueous PBS buffer medium which is noticeable through naked eye whereas L1 failed to sense these albumin proteins. The selective TURN-ON fluorescence response of L towards HSA/BSA can be attributed to the selective binding of the probe L with HSA/BSA without interfering with the known drug binding sites. The specific binding of L with HSA led to the disassembly of the self-assemble nanoaggregates of L which is corroborated by DLS (Dynamic light scattering) and TEM (Transmission Electron Microscopy) analysis. The probe L has a limit of detection as low as ~6.5 nM. The sensing aptitude of the probe L to detect HSA in body fluid and artificial urine sample has been demonstrated.

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Two types of zwitterionic polymer-modified magnetic nanoparticles (NPs) are fabricated by conjugating pSBMA onto PEI-precoated NPs via either one-step method (1S NPs) or two-step method (2S NPs). For both methods, divinyl sulfone is used as linker molecule. Although 1S NPs were capable of resisting both IgG and BSA, 2S NPs exhibited specificity toward IgG adsorption in complex biological fluids, e.g. mixture of serums and IgG. The moderate interactions (Kd ~1.2 µM) between IgG and 2S NPs are three orders of magnitude lower than IgG binding with Protein A (Kd 10nM). Through complementary characterizations and analyses, we rationalize that the surface developed herein with IgG specificity contains two key components: polyzwitterions with short chain length and sulfone groups with high density.

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Minimizing the foreign body reaction to polyimide-based implanted devices has a pivotal role for several biomedical applications. In this work we propose materials exhibiting non-biofouling properties and a Young’s modulus reflecting the one of soft human tissues. We describe the synthesis, characterization and in vitro validation of poly(carboxybetaine) hydrogel coatings covalently attached to polyimide substrates via a photolabile 4-azidophenyl group, incorporated in poly(carboxybetaine) chains at two concentrations of 1.6 and 3.1 mol.%. The presence of coatings was confirmed by attenuated total reflectance Fourier-transform infrared spectroscopy. White light interferometry was used to evaluate coating continuity and thickness (resulting between 3 and 6 µm in dry conditions). Confocal laser scanning microscopy allowed to quantify the thickness of the swollen hydrogel coatings that ranged between 13 and 32 µm. The different hydrogel formulations resulted in stiffness values ranging from 2 to 19 kPa, and led to different fibroblasts and macrophages responses tested in vitro. Both cell types showed a minimum adhesion on the softest hydrogel type. In addition, both the overall macrophage activation and cytotoxicity were observed to be negligible for all the tested material formulations. These results are a promising starting point towards future advanced implantable systems. In particular, such technology paves the way to novel neural interfaces able to minimize the fibrotic reaction, once implanted in vivo, and to maximize their long-term stability and functionality.

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In our preceding paper (Part 1), we identified three 1,5-bis-diaryl-1,2,4-triazole-based compounds that merited evaluation as potential PET radioligands for selectively imaging COX-1 in monkey and human brain, namely (1,5-bis-(4-methoxyphenyl)-3-(alkoxy)-1 H -1,2,4-triazoles bearing a 3-methoxy (PS1), a 3-(2,2,2-trifluoroethoxy) (PS13), or a 3-fluoromethoxy substituent (PS2). PS1 and PS13 were labeled by O -11C-methylation reactions with [11C]iodomethane, and PS2 by O -18F-fluoroalkylation with [ d 2-18F]fluorobromomethane. Here, we evaluated these PET radioligands in monkey. All three radioligands gave moderately high uptake in brain, although [2H2-18F]PS2 also showed undesirable radioactivity uptake in skull. [11C]PS13 was selected for further evaluation, mainly based on more favorable brain kinetics than [11C]PS1 among other considerations. Pharmacological challenge experiments showed that ~ 55% of the radioactivity uptake in brain was specifically bound to COX-1. An index of enzyme density, V T, was well identified from serial brain scans and from the concentrations of parent radioligand in arterial plasma. In addition, V T values were stable within 80 min, suggesting that brain uptake was not contaminated by radiometabolites. [11C]PS13 successfully images and quantifies COX-1 in monkey brain, and merits further investigation for imaging COX-1 in monkey models of neuroinflammation and in human subjects.

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Antimicrobial resistance (AMR) has been recognised as an urgent health priority, both nationally and internationally. Australian hospitals are required to have an antimicrobial stewardship (AMS) program, yet the necessary resources may not be available in regional, rural or remote hospitals. This review will describe models for AMS programs that have been introduced in regional, rural or remote hospitals internationally and showcase achievements and key considerations that may guide Australian hospitals in establishing or sustaining AMS programs in the regional, rural or remote hospital setting.