Covalently conjugated polypyrrole-chitosan nanofibrous conductive composites prepared using dialdehyde polysaccharide linkers.

Polypyrrole (PPy) composites, despite their conductivity and bioactivity, are prone to degradation (e.g., exfoliation or delamination) due to the lack of chemical bonds between PPy and the matrix.

Highly catalytically active composite of palladium nanoparticles covalently bound to chitosan nanofibers via dialdehyde cellulose.

This study introduces a novel, sustainable method for synthesizing sub-5 nm palladium nanoparticles (PdNPs) and covalently binding them to chitosan nanofibers (CHITs) using fully oxidized dialdehyde cellulose (DAC). Notably, the DAC acts not only as a reducing and stabilizing agent for PdNPs, but also as a linker for their rapid and spontaneous covalent attachment to CHITs via Schiff base chemistry. This unique approach yields PdNPs with a narrow size distribution (4.

Biocompatibility of colloidal polypyrrole.

The excellent electroconductive properties of polypyrrole (PPy) predetermine its use as cell-instructive or biosensing biomaterial. PPy has potential for application in a physiological environment, and here the cytotoxicity, antioxidant capacity, modulation of neutrophil oxidative burst, antibacterial activity of colloidal PPy stabilized with polyvinylpyrrolidone (PVP), and long-term stability under physiological conditions are reported. Besides, long-term stability under physiological conditions is also provided.

Chitosan/dialdehyde cellulose hydrogels with covalently anchored polypyrrole: Novel conductive, antibacterial, antioxidant, immunomodulatory, and anti-inflammatory materials.

In this work, conductive composite hydrogels with covalently attached polypyrrole (PPy) nanoparticles are prepared. Hydrogels are based on partially re-acetylated chitosan soluble at physiological pH without any artificial structural modifications or need for an acidic environment, which simplifies synthesis and purification. Low-toxic and sustainable dialdehyde cellulose (DAC) was used for crosslinking chitosan and covalent anchoring of PPy colloidal particles.

Highly efficient affinity anchoring of gold nanoparticles on chitosan nanofibers via dialdehyde cellulose for reusable catalytic devices.

Polysaccharides are often utilized as reducing and stabilizing agents and as support in the synthesis of gold nanoparticles (AuNPs). However, using approaches like spin coating or dip coating, AuNPs are generally bound to the support only by weak interactions, which can lead to decreased stability of the composite. Here, a two-stage approach for the preparation of composites with covalently anchored AuNPs is proposed.

Pickering emulsions as an effective route for the preparation of bioactive composites: A study of nanocellulose/polyaniline particles with immunomodulatory effect.

Several studies have reported on application of cellulose particles for stabilizing Pickering emulsions (PE). Here we employ an original approach that involves using these particles as a part of advanced composite colloids made of conducting polymer polyaniline (PANI) and cellulose nanocrystals (CNC) or nanofibrils (CNF). PANI/cellulose particles were prepared using oxidative polymerization of aniline in situ in the presence of CNC or CNF.

The essential role of symmetry in understanding He chemical shifts in endohedral helium fullerenes.

The He atom is an excellent NMR probe, particularly when enclosed in endohedral helium fullerenes. The He chemical shift, (He), in fullerenes spans a range from -50 to +10 ppm, and changes sensitively between different cages, isomers, and external substituents. Reduction of the fullerenes to anions changes the (He) dramatically and unexpectedly, particularly for the most symmetric and also the most abundant C and C cages.

Exact Two-Component TDDFT with Simple Two-Electron Picture-Change Corrections: X-ray Absorption Spectra Near L- and M-Edges of Four-Component Quality at Two-Component Cost.

X-ray absorption spectroscopy (XAS) has gained popularity in recent years as it probes matter with high spatial and elemental sensitivities. However, the theoretical modeling of XAS is a challenging task since XAS spectra feature a fine structure due to scalar (SC) and spin-orbit (SO) relativistic effects, in particular near L and M absorption edges. While full four-component (4c) calculations of XAS are nowadays feasible, there is still interest in developing approximate relativistic methods that enable XAS calculations at the two-component (2c) level while maintaining the accuracy of the parent 4c approach.

Enzyme-Catalyzed Polymerization Process: A Novel Approach to the Preparation of Polyaniline Colloidal Dispersions with an Immunomodulatory Effect.

A green, nature-friendly synthesis of polyaniline colloidal particles based on enzyme-assisted oxidation of aniline with horseradish peroxidase and chitosan or poly(vinyl alcohol) as steric stabilizers was successfully employed. Physicochemical characterization revealed formation of particles containing the polyaniline emeraldine salt and demonstrated only a minor effect of polymer stabilizers on particle morphology. All tested colloidal particles showed antioxidation activity determined via scavenging of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals.

Dicarboxylated hyaluronate: Synthesis of a new, highly functionalized and biocompatible derivative.

Sequential periodate-chlorite oxidation of sodium hyaluronate to 2,3-dicarboxylated hyaluronate (DCH), a novel biocompatible and highly functionalized derivative bearing additional pair of COOH groups at C2 and C3 carbons of oxidized ᴅ-glucuronic acid units, is investigated. The impact of various reaction parameters (time, oxidizer concentration, and molar amount) on DCH's composition, molecular weight, degree of oxidation, and cytotoxicity are investigated to guide the synthesis of DCH derivatives of desired properties. Subsequently, fully (99%) and partially (70%) oxidized DCH derivatives were compared to untreated sodium hyaluronate in terms of anticancer drug cisplatin loading efficacy, carrier capacity, drug release rates, and cytotoxicity towards healthy and cancerous cell lines.

One-step synthesis of gold nanoparticles for catalysis and SERS applications using selectively dicarboxylated cellulose and hyaluronate.

Properties and applications of gold nanoparticles (AuNPs) depend on their characteristics which are intrinsically connected to the reducing and capping agents used in their synthesis. Although polysaccharides are commonly used for Au salt reduction, the control over the result is often limited. Here, the selectively dicarboxylated cellulose (DCC) and hyaluronate (DCH) with adjustable composition and molecular weight are used for the first time as reducing and capping agents for AuNPs preparation in an environmental friendly one-step synthesis.

Accurate X-ray Absorption Spectra near L- and M-Edges from Relativistic Four-Component Damped Response Time-Dependent Density Functional Theory.

The simulation of X-ray absorption spectra requires both scalar and spin-orbit (SO) relativistic effects to be taken into account, particularly near L- and M-edges where the SO splitting of core p and d orbitals dominates. Four-component Dirac-Coulomb Hamiltonian-based linear damped response time-dependent density functional theory (4c-DR-TDDFT) calculates spectra directly for a selected frequency region while including the relativistic effects variationally, making the method well suited for X-ray applications. In this work, we show that accurate X-ray absorption spectra near L- and M-edges of closed-shell transition metal and actinide compounds with different central atoms, ligands, and oxidation states can be obtained by means of 4c-DR-TDDFT.

Behaviour of Titanium Dioxide Particles in Artificial Body Fluids and Human Blood Plasma.

The growing application of materials containing TiO particles has led to an increased risk of human exposure, while a gap in knowledge about the possible adverse effects of TiO still exists. In this work, TiO particles of rutile, anatase, and their commercial mixture were exposed to various environments, including simulated gastric fluids and human blood plasma (both representing in vivo conditions), and media used in in vitro experiments. Simulated body fluids of different compositions, ionic strengths, and pH were used, and the impact of the absence or presence of chosen enzymes was investigated.

Oxidized polysaccharides for anticancer-drug delivery: What is the role of structure?

Study provides an in-depth analysis of the structure-function relationship of polysaccharide anticancer drug carriers and points out benefits and potential drawbacks of differences in polysaccharide glycosidic bonding, branching and drug binding mode of the carriers. Cellulose, dextrin, dextran and hyaluronic acid have been regioselectively oxidized to respective dicarboxylated derivatives, allowing them to directly conjugate cisplatin, while preserving their major structural features intact. The structure of source polysaccharide has crucial impact on conjugation effectiveness, carrier capacity, drug release rates, in vitro cytotoxicity and cellular uptake.

Design of dialdehyde cellulose crosslinked poly(vinyl alcohol) hydrogels for transdermal drug delivery and wound dressings.

2,3-Dialdehyde cellulose (DAC) was used as an efficient and low-toxicity crosslinker to prepare thin PVA/DAC hydrogel films designed for topical applications such as drug-loaded patches, wound dressings or cosmetic products. An optimization of hydrogel properties was achieved by the variation of two factors - the amount of crosslinker and the weight-average molecular weight (M) of the source PVA. The role of each factor to network parameters, mechanical, rheological and surface properties, hydrogel porosity and transdermal absorption is discussed.

Towards Accurate Predictions of Proton NMR Spectroscopic Parameters in Molecular Solids.

The factors contributing to the accuracy of quantum-chemical calculations for the prediction of proton NMR chemical shifts in molecular solids are systematically investigated. Proton chemical shifts of six solid amino acids with hydrogen atoms in various bonding environments (CH, CH , CH , OH, SH and NH ) were determined experimentally using ultra-fast magic-angle spinning and proton-detected 2D NMR experiments. The standard DFT method commonly used for the calculations of NMR parameters of solids is shown to provide chemical shifts that deviate from experiment by up to 1.

Experimental and Theoretical Evidence of Spin-Orbit Heavy Atom on the Light Atom H NMR Chemical Shifts Induced through H⋅⋅⋅I Hydrogen Bond.

Invited for the cover of this issue is the group of Michal Straka and Martin Dračínský (IOCB Prague, Czech Academy of Sciences). The image depicts a neutron star, which is used to represent the relativistic effects between a heavy element and a hydrogen atom reported in this work. Read the full text of the article at 10.

Relativity or aromaticity? A first-principles perspective of chemical shifts in osmabenzene and osmapentalene derivatives.

We have studied the magnetic response properties and aromaticity of osmium metallacycles by means of scalar-relativistic (1c) and fully relativistic (4c) density functional theory computations. For osmabenzene, whose aromatic character is controversial, a topological analysis of the current density has revealed the presence of a unique σ-type Craig-Möbius magnetic aromaticity. We show that the partially filled osmium valence shell induces a large paratropic current, which may interfere with certain methods commonly used to analyze aromaticity, in particular NICS.

Experimental and Theoretical Evidence of Spin-Orbit Heavy Atom on the Light Atom H NMR Chemical Shifts Induced through H⋅⋅⋅I Hydrogen Bond.

Spin-orbit (SO) heavy-atom on the light-atom (SO-HALA) effect is the largest relativistic effect caused by a heavy atom on its light-atom neighbors, leading, for example, to unexpected NMR chemical shifts of H, C, and N nuclei. In this study, a combined experimental and theoretical evidence for the SO-HALA effect transmitted through hydrogen bond is presented. Solid-state NMR data for a series of 4-dimethylaminopyridine salts containing I , Br and Cl counter ions were obtained experimentally and by theoretical calculations.

Biocompatible dialdehyde cellulose/poly(vinyl alcohol) hydrogels with tunable properties.

Solubilized dialdehyde cellulose (DAC), an efficient crosslinking agent for poly(vinyl alcohol) (PVA), provides less toxic alternative to current synthetic crosslinking agents such as glutaraldehyde, while simultaneously allowing for the preparation of hydrogels with comparably better characteristics. PVA/DAC hydrogels prepared using 0.5, 1 and 1.

Selectively Oxidized Cellulose with Adjustable Molecular Weight for Controlled Release of Platinum Anticancer Drugs.

The synthesis of selectively oxidized cellulose, 2,3-dicarboxycellulose (DCC), is optimized for preparation of highly oxidized material for biological applications, which includes control over the molecular weight of the product during its synthesis. Conjugates of DCC and cisplatin simultaneously offer a very high drug binding efficiency (>90%) and drug loading capacity (up to 50 wt %), while retaining good aqueous solubility. The adjustable molecular weight of the DCC together with variances in drug feeding ratio allows to optimize cisplatin release profiles from delayed (<2% of cisplatin released during 6 h) to classical burst release with more than 60% of cisplatin released after 24 h.

Spectroscopic and Computational Evidence of Intramolecular Au ⋅⋅⋅H -N Hydrogen Bonding.

Despite substantial evidence of short Au⋅⋅⋅H-X contacts derived from a number of X-ray structures of Au compounds, the nature of Au ⋅⋅⋅H bonding in these systems has not been clearly understood. Herein, we present the first spectroscopic evidence for an intramolecular Au ⋅⋅⋅H -N hydrogen bond in a [Cl-Au-L] complex, where L is a protonated N-heterocyclic carbene. The complex was isolated in the gas phase and characterized with helium-tagging infrared photodissociation (IRPD) spectra, in which H -N-mode-derived bands evidence the intramolecular Au ⋅⋅⋅H -N bond.

Reactive Dimerization of an N-Heterocyclic Plumbylene: C-H Activation with Pb.

The N-heterocyclic plumbylene [Fe{(η -C H )NSiMe } Pb:] is in equilibrium with an unprecedented dimer in solution, whose formation involves the cleavage of a strong C-H bond and concomitant formation of a Pb-C and an N-H bond. According to a mechanistic DFT assessment, dimer formation does not involve direct Pb insertion into a cyclopentadienyl C-H bond, but is best described as an electrophilic substitution. The bulkier plumbylene [Fe{(η -C H )NSitBuMe } Pb:] shows no dimerization, but compensates its electrophilicity by the formation of an intramolecular Fe-Pb bond.