Bio-based modification of polyhydroxyalkanoates (PHA) towards increased antimicrobial activities and reduced cytotoxicity.

With the increased occurrence of bacteria resistance to conventional antibiotics, the development of novel antimicrobials is urgently needed. Traditional biomaterials used for delivering these agents often struggle to achieve sustained release while maintaining non-cytotoxic properties. In this study, we present an innovative approach using bacterial polyhydroxyalkanoates (PHA) as a carrier for antimicrobial delivery, specifically designed for wound healing applications. Octenidine dihydrochloride (OCT), a widely used antimicrobial agent, served as our model drug. To achieve the desired balance of OCT release and low cytotoxicity, we introduced a novel bio-derived additive, 3-hydroxy-pentadecanoic acid (3OHC15), extracted from bacteria. This additive significantly improved the hydrophilicity of PHA films, resulting in enhanced and sustained release of OCT. Importantly, the additive did not adversely affect the material's tensile strength or thermal properties. The increased OCT release led to improved antibacterial activity against both Gram-negative and -positive strains. Most notably, the incorporation of 3OHC15 in PHA mitigated the cytotoxic effects of the released drug on human fibroblasts, ensuring biocompatibility. This work represents a novel strategy in the design of biomaterials for the delivery of bioactive compounds, achieving a critical balance between efficacy and cytocompatibility, and marks a significant advancement in the field of antimicrobial delivery systems.

Reusable magnetic mixture of CuFe2O4-Fe2O3 and TiO2 for photocatalytic degradation of pesticides in water.

Photocatalysis is a promising treatment method to remove pollutants from water. TiO2-P25 is a commercially available model photocatalyst, which very efficiently degrades organic pollutants under UVA light exposure. However, the collection and the recovery of TiO2-P25 from cleaned water poses significant difficulties, severely limiting its usability. To address this challenge, we have prepared a sintered mixture of TiO2-P25 nanomaterials and magnetic CuFe2O4-Fe2O3 nanocomposites. The mixture material was shown to contain spinel ferrite, hematite and maghemite structures, copper predominantly in Cu2+ and iron predominantly in Fe3+ state. The CuFe2O4-Fe2O3 and TiO2-P25 mixture demonstrated magnetic collectability from processed water and photocatalytic activity, which was evidenced through the successful photodegradation of the herbicide 2,4-D. Our findings suggest that the sintered mixture of CuFe2O4-Fe2O3 and TiO2-P25 holds a promise for improving photocatalytic water treatment, with the potential to overcome current photocatalyst recovery issues.

Ambient Catalytic Spinning of Polyethylene Nanofibers.

A novel single-atom Ni(II) catalyst (Ni-OH) is covalently immobilized onto the nano-channels of mesoporous Santa Barbara Amorphous (SBA)-15 particles and isotropic Anodized Aluminum Oxide (AAO) membrane for confined-space ethylene extrusion polymerization. The presence of surface-tethered Ni complexes (Ni@SBA-15 and Ni@AAO) is confirmed by the inductively coupled plasma-optical emission spectrometry (ICP-OES) and X-ray photoelectron spectroscopy (XPS). In the catalytic spinning process, the produced PE materials exhibit very homogeneous fibrous morphology at nanoscale (diameter: ~50 nm). The synthesized PE nanofibers extrude in a highly oriented manner from the nano-reactors at ambient temperature. Remarkably high Mw (1.62×106  g mol-1 ), melting point (124 °C), and crystallinity (41.8 %) are observed among PE samples thanks to the confined-space polymerization. The chain-walking behavior of surface tethered Ni catalysts is greatly limited by the confinement inside the nano-channels, leading to the formation of very low-branched PE materials (13.6/1000 C). Due to fixed supported catalytic topology and room temperature, the filaments are expected to be free of entanglement. This work signifies an important step towards the realization of a continuous mild catalytic-spinning (CATSPIN) process, where the polymer is directly synthesized into fiber shape at negligible chain branching and elegantly avoiding common limitations like thermal degradation or molecular entanglement.

Synthesis of polar polynorbornenes with high dielectric relaxation strength as candidate materials for dielectric applications.

Materials with high dielectric permittivity and dielectric relaxation strength are sought for thermal and pressure sensors and electrical energy generators. However, most polymers have either too low dielectric permittivity or are so polar that their glass transition temperature (T g) is too high and thus decomposition and side reactions occur before an electric field can polarize the polar groups. Here, we use the power and versatility of ring-opening metathesis polymerization (ROMP) to synthesize polar polymers with high dielectric relaxation strength and T g significantly below the decomposition temperature. We first synthesized six polar norbornene monomers by conventional esterification, which were then polymerized by ROMP using Grubbs first- and third-generation catalysts. The structure of the polynorbornenes obtained were verified by multinuclear NMR spectroscopy, molecular weights determined by gel permeation chromatography (GPC), and thermal properties evaluated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Additionally, their dielectric permittivity, conductivity, and dielectric losses were measured at different temperatures and frequencies ranging between 0.1 and 106 Hz.

Smart hydrogel-microsphere embedded silver nanoparticle catalyst with high activity and selectivity for the reduction of 4-nitrophenol and azo dyes.

A simple method is reported for the preparation of silver nanoparticle (AgNP) embedded pH-responsive hydrogel microparticle catalyst via Michael addition gelation and in-situ silver nitrate (AgNO3) reduction. The AgNP-hydrogel microsphere exhibited an efficient reduction of pollutants like 4-Nitrophenol (4-NP) and Congo red (CR) under acidic medium with turn over frequency (TOF) of ~170 h-1 and ~124 h-1 respectively. Interestingly, the activity of the catalysts was turned-OFF under a basic medium (≥ pH 12) due to the deswelling pH-responsive matrix surrounding the AgNPs. On the contrary, turning-OFF the hydrogenation of a cationic pollutant like methylene blue (MB) using high pH (≥ 12) was not possible, due to ionic interaction of MB molecules with the negatively charged catalyst at this pH. This feature was used to demonstrate selective hydrogenation of only MB from a mixture of 4-NP and MB. Finally, five recycling steps confirmed the reusability and practical application potential of the catalyst.

Nano-analytical characterization of endogenous minerals in healthy placental tissue: mineral distribution, composition and ultrastructure.

Despite its crucial role, the placenta is the least understood human organ. Recent clinical studies indicate a direct association between placental calcification and maternal and offspring health. This study reveals distinct characteristics of minerals formed during gestational ageing using cutting-edge nano-analytical characterization and paves the way for investigations focused on the identification of potential markers for disease risks in a clinical setting based on atypical placental mineral fingerprints.

Insight into the Synthesis and Characterization of Organophosphorus-Based Bridged Triazine Compounds.

In this article, we report the synthesis of 2,4,6-substituted s-triazine-based organophosphorus compounds via a two-step process, which enables their production in high yields, and with a high purity as solids. In the first step, a Michaelis-Arbuzov rearrangement of cyanuric chloride with triethyl phosphite afforded 2,4,6-trisdiethoxyphosphinyl-1,3,5-triazine (HEPT). Subsequently, the nucleophilic substitution reaction on the triazine carbon was achieved, owing to the electron-withdrawing ability of the phosphonate groups. This characteristic of HEPT facilitated its derivatization with bi-functional amines, producing novel P-C containing bridged triazine organophosphorus compounds. The molecular structures of all of the compounds were confirmed by NMR spectroscopy, CHN elemental analysis, and single crystal X-ray analysis. In the thermogravimetric analysis in an N2 environment, >33% char formation was observed for the bridged compounds. The chemical composition analysis of the char obtained under the oxidative thermal decomposition of the bridged compounds confirmed the presence of phosphorus- and nitrogen-enriched species, which indicate their function in the condensed phase. Comparatively, the detection of HPO and H-C≡P in the gas phase during the pyrolysis of the bridged compounds can act as a source for PO•, which is known for its gas phase flame inhibition reactions. The synergy of significant char formation and the generation of intermediates leading to PO• during pyrolysis makes these molecules promising flame-retardant additives.

Biotransformation of short-chain chlorinated paraffins (SCCPs) with LinA2: A HCH and HBCD converting bacterial dehydrohalogenase.

Short-chain chlorinated paraffins (SCCPs) are polyhalogenated hydrocarbons as are hexachlorocyclohexanes (HCHs) and hexabromocyclododecanes (HBCDs). They all have been classified as persistent organic pollutants (POPs) under the UN Stockholm Convention. Per se such compounds are transformed slowly in the environment, transported over long distances and accumulate in biota. Several Sphingomonadacea strains isolated from HCH dump sites have evolved to express enzymes that can transform HCHs and HBCDs. We hypothesized that LinA2, a dehydrohalogenase expressed in such bacteria, may also transform CPs to chlorinated olefins (COs). Three mixtures of penta- to deca-chlorinated undecanes (C11), dodecanes (C12) and tridecanes (C13) were exposed to LinA2. High-resolution full-scan mass spectra (R∼8'000) of CPs and COs were obtained applying a soft ionization method, enhancing chloride-adduct [M+Cl]- formation. A mathematical deconvolution procedure was used to separate interfering spectra to verify that LinA2 indeed catalyzed the conversion of CPs to COs. About 20-40% of the material was transformed in 24 h, about 50-70% was converted in 200 h. A bimodal first-order kinetic model could describe transformations of reactive and persistent CPs. Under the given conditions reactive CPs (τ1/2 = 1.4-6.9 h) were converted 30 to 190-times faster than the persistent ones (τ1/2 = 150-260 h). Proportions of persistent isomers (pp) varied from 60 to 80%. Lower chlorinated homologues contained higher proportions of persistent isomers. In conclusion, SCCP mixtures contain both, material that is readily converted by LinA2, and persistent material that is not or only slowly transformed.

Transformation of chlorinated paraffins to olefins during metal work and thermal exposure - Deconvolution of mass spectra and kinetics.

Chlorinated paraffins (CPs) are high production volume chemicals widely used as additives in metal working fluids. Thereby, CPs are exposed to hot metal surfaces which may induce degradation processes. We hypothesized that the elimination of hydrochloric acid would transform CPs into chlorinated olefins (COs). Mass spectrometry is widely used to detect CPs, mostly in the selected ion monitoring mode (SIM) evaluating 2-3 ions at mass resolutions R < 20'000. This approach is not suited to detected COs, because their mass spectra strongly overlap with CPs. We applied a mathematical deconvolution method based on full-scan MS data to separate interfered CP/CO spectra. Metal drilling indeed induced HCl-losses. CO proportions in exposed mixtures of chlorotridecanes increased. Thermal exposure of chlorotridecanes at 160, 180, 200 and 220 °C also induced dehydrohalogenation reactions and CO proportions also increased. Deconvolution of respective mass spectra is needed to study the CP transformation kinetics without bias from CO interferences. Apparent first-order rate constants (kapp) increased up to 0.17, 0.29 and 0.46 h-1 for penta-, hexa- and heptachloro-tridecanes exposed at 220 °C. Respective half-life times (τ1/2) decreased from 4.0 to 2.4 and 1.5 h. Thus, higher chlorinated paraffins degrade faster than lower chlorinated ones. In conclusion, exposure of CPs during metal drilling and thermal treatment induced HCl losses and CO formation. It is expected that CPs and COs are co-released from such processes. Full-scan mass spectra and subsequent deconvolution of interfered signals is a promising approach to tackle the CP/CO problem, in case of insufficient mass resolution.

Deconvolution of Mass Spectral Interferences of Chlorinated Alkanes and Their Thermal Degradation Products: Chlorinated Alkenes.

Chlorinated paraffins (CPs) are high production volume chemicals and ubiquitous environmental contaminants. CPs are produced and used as complex mixtures of polychlorinated n-alkanes containing thousands of isomers, leading to demanding analytical challenges. Due to their high degree of chlorination, CPs have highly complex isotopic mass patterns that often overlap, even when applying high resolution mass spectrometry. This is further complicated in the presence of degradation products such as chlorinated alkenes (CP-enes). CP-enes are formed by dehydrochlorination of CPs and are expected thermal degradation products in some applications of CPs, for example, as metal working fluids. A mathematical method is presented that allows deconvolution of the strongly interfered measured isotope clusters into linear combinations of isotope clusters of CPs and CP-enes. The analytical method applied was direct liquid injection into an atmospheric pressure chemical ionization source, followed by quadrupole time-of-flight mass spectrometry (APCI-qTOF-MS), operated in full scan negative ion mode. The mathematical deconvolution method was successfully applied to a thermally aged polychlorinated tridecane formulation (Cl5-Cl9). Deconvolution of mass patterns allowed quantifying fractions of interfering CPs and CP-enes. After exposure to 220 °C for 2, 4, 8, and 24 h, fractions of CP-enes within the respective interfering clusters increased from 0-3% at 0 h up to 37-44% after 24 h. It was shown that thermolysis of CPs follows first-order kinetics. The presented deconvolution method allows CP degradation studies with mass resolution lower than 20000 and is therefore a good alternative when higher resolution is not available.