Novel biocompatible Cu2+-containing composite hydrogels based on bacterial cellulose and poly-1-vinyl-1,2,4-triazole

Novel composite hydrogels representing interpenetrating polymeric networks (IPN) have been synthesized and consisted of Gluconacetobacter xylinus cellulose (GxC) and poly-1-vinyl-1,2,4-triazole (PVT) with Cu2⁺. The composite hydrogels’ mesostructure has been studied from 1.6 ​nm to 2.5 ​μm by small-angle and ultra-small-angle neutron scattering methods. It has been found that IPN complexes have three types of inhomogeneities: GxC, PVT, and PVT complex with Cu2⁺. The amount of the absorbed ions can be tuned as confirmed by electron paramagnetic spectroscopy. Besides, three hierarchy levels of GxC remained in the supramolecular structure of composite hydrogels. Reveling structure formation in these composite hydrogels is essential in fabricating hybrid polymeric materials for regenerative medicine, involving antibacterial or antifungal applications

Calcifying Bacteria Flexibility in Induction of CaCO3 Mineralization

Microbially induced CaCO3 precipitation (MICP) is considered as an alternative green technology for cement self-healing and a basis for the development of new biomaterials. However, some issues about the role of bacteria in the induction of biogenic CaCO3 crystal nucleation, growth and aggregation are still debatable. Our aims were to screen for ureolytic calcifying microorganisms and analyze their MICP abilities during their growth in urea-supplemented and urea-deficient media. Nine candidates showed a high level of urease specific activity, and a sharp increase in the urea-containing medium pH resulted in efficient CaCO3 biomineralization. In the urea-deficient medium, all ureolytic bacteria also induced CaCO3 precipitation although at lower pH values. Five strains (B. licheniformis DSMZ 8782, B. cereus 4b, S. epidermidis 4a, M. luteus BS52, M. luteus 6) were found to completely repair micro-cracks in the cement samples. Detailed studies of the most promising strain B. licheniformis DSMZ 8782 revealed a slower rate of the polymorph transformation in the urea-deficient medium than in urea-containing one. We suppose that a ureolytic microorganism retains its ability to induce CaCO3 biomineralization regardless the origin of carbonate ions in a cell environment by switching between mechanisms of urea-degradation and metabolism of calcium organic salts

A sol-gel synthesis and gas-sensing properties of finely dispersed ZrTiO4

The transparent titanium-zirconium-containing gel was obtained using heteroligand coordination compounds (namely, alkoxoacetylacetonates) as the precursors. The high-dispersive system “ZrTiO4 – carbon”, formed after drying of such gel and carbonization of the obtained xerogel, was used to study the evolution of microstructure for the product (ZrTiO4) during thermal treatment in air for 1 h in the temperature range from 500 °C to 1000°С. It was stated that the formation of crystalline phase occurred in the narrow range 690-730°С. The thermal treatment at 500 °C and 600°С allowed obtaining micro- and mesoporous X-ray amorphous products of the composition ZrTiO4, with the specific surface area falling in the range 82–150m2/g. At the higher temperatures the single-phase nanocrystalline powder was prepared (the specific surface area amounted to 2.5–15m2/g). Particle coarsening took place more extensively at temperatures ≥700°С was shown. For the ZrTiO4 nanopowder crystallized under the mildest conditions at the temperature of 700 °C, chemoresistive gas-sensitive properties were studied for the first time. The material showed a high reproducible response at 1–20% O2 and 200–10,000 ppm H2 at a relatively low detection operating temperature of 450 °C

Composite Hydrogels Based on Bacterial Cellulose and Poly-1-vinyl-1,2,4-triazole/Phosphoric Acid: Supramolecular Structure as Studied by Small Angle Scattering

New composite hydrogels (CH) based on bacterial cellulose (BC) and poly-1-vinyl-1,2,4-triazole (PVT) doped with orthophosphoric acid (oPA), presenting interpenetrating polymeric networks (IPN), have been synthesized. The mesoscopic study of the supramolecular structure (SMS) of both native cellulose, produced by the strain Komagataeibacter rhaeticus, and the CH based on BC and containing PVT/oPA complex were carried out in a wide range of momentum transfer using ultra- and classical small-angle neutron scattering techniques. The two SMS hierarchical levels were revealed from 1.6 nm to 2.5 μm for the objects under investigation. In addition, it was shown that the native BC had a correlation peak on the small-angle scattering curves at 0.00124 Å−1, with the correlation length ξ being equal to ca. 510 nm. This motive was also retained in the IPN. The data obtained allowed the estimation of the fractal dimensions and ranges of self-similarity and gave new information about the BC mesostructure and its CH. Furthermore, we revealed them to be in coincidence with Brown’s BC model, which was earlier supported by Fink’s results

Crystal and Supramolecular Structure of Bacterial Cellulose Hydrolyzed by Cellobiohydrolase from Scytalidium Candidum 3C: A Basis for Development of Biodegradable Wound Dressings

The crystal and supramolecular structure of the bacterial cellulose (BC) has been studied at different stages of cellobiohydrolase hydrolysis using various physical and microscopic methods. Enzymatic hydrolysis significantly affected the crystal and supramolecular structure of native BC, in which the 3D polymer network consisted of nanoribbons with a thickness T ≈ 8 nm and a width W ≈ 50 nm, and with a developed specific surface SBET ≈ 260 m2·g−1. Biodegradation for 24 h led to a ten percent decrease in the mean crystal size Dhkl of BC, to two-fold increase in the sizes of nanoribbons, and in the specific surface area SBET up to ≈ 100 m2·g−1. Atomic force and scanning electron microscopy images showed BC microstructure “loosening“after enzymatic treatment, as well as the formation and accumulation of submicron particles in the cells of the 3D polymer network. Experiments in vitro and in vivo did not reveal cytotoxic effect by the enzyme addition to BC dressings and showed a generally positive influence on the treatment of extensive III-degree burns, significantly accelerating wound healing in rats. Thus, in our opinion, the results obtained can serve as a basis for further development of effective biodegradable dressings for wound healin