Polydopamine-Assisted Surface Modification of Ti-6Al-4V Alloy with Anti-Biofilm Activity for Dental Implantology Applications

Coating the surfaces of implantable materials with various active principles to ensure inhibition of microbial adhesion, is a solution to reduce infections associated with dental implant. The aim of the study was to optimize the polydopamine films coating on the Ti-6Al-6V alloy surface in order to obtain a maximum of antimicrobial/antibiofilm efficacy and reduced cytotoxicity. Surface characterization was performed by evaluating the morphology (SEM, AFM) and structures (Solid-state 13C NMR and EPR). Antimicrobial activity was assessed by logarithmic reduction of CFU/mL, and the antibiofilm activity by reducing the adhesion of Escherichia coli, Staphylococcus aureus, and Candida albicans strains. The release of NO was observed especially for C. albicans strain, which confirms the results obtained for microbial adhesion. Among the PDA coatings, for 0.45:0.88 (KMnO4:dopamine) molar ratio the optimal compromise was obtained in terms of antimicrobial activity and cytotoxicity, while the 0.1:1.5 ratio (KMnO4:dopamine) led to higher NO release and implicitly the reduction of the adhesion capacities only for C. albicans, being slightly cytotoxic but with moderate release of LDH. The proposed materials can be used to reduce the adhesion of yeast to the implantable material and thus inhibit the formation of microbial biofilms.

Modeling of Antioxidant Activity, Polyphenols and Macronutrients Content of Bee Pollen Applying Solid-State 13C NMR Spectra

An application of solid 13C nuclear magnetic resonance (NMR) spectroscopy for the determination of macronutrients, total polyphenols content, antioxidant activity, N C S elements, and pH in commercially available bee pollens is reported herein. Solid-state 13C NMR spectra were recorded for homogenized pollen granules without chemical treatment or dissolution of samples. By combining spectral data with the results of reference analyses, partial least squares models were constructed and validated separately for each of the studied parameters. To characterize and compare the models’ quality, the relative standard errors of prediction (RSEP) were calculated for calibration and validation sets. In the case of the analysis of protein, fat and reducing sugars, these errors were in the 1.8–2.5% range. Modeling the elemental composition of bee pollen on the basis of 13C NMR spectra resulted in RSEPcal/RSEPval values of 0.3/0.6% for the sum of NHCS elements, 0.3/0.4% for C, 1.8/1.9% for N, and 4.2/6.1% for S quantification. Analyses of total phenolics and ABTS antioxidant activity resulted in RSEP values in the 2.7–3.5% and 2.8–3.8% ranges, respectively, whereas they were 1.4–2.1% for pH. The obtained results demonstrate the usefulness of 13C solid-state NMR spectroscopy for direct determination of various important physiochemical parameters of bee pollen.

DETERMINATION OF WOOD COMPOSITION USING SOLID-STATE 13C NMR SPECTROSCOPY

In recent years, solid-state 13C NMR spectroscopy using the technique of cross-polarization (CP) and sample rotation at a magic angle (MAS) has been widely used in the analysis of plant materials, including wood. Knowledge of the composition, structure and behavior of wood components under various conditions is of great importance, since the properties of wood materials depend on this. In this work, differences in the composition of wood belonging to various tree species growing in central Russia (spruce, aspen, birch, oak, linden, pine, poplar and larch) were revealed using CP MAS 13C NMR spectroscopy. The assignment of various peaks in CP MAS 13C NMR spectra to the main components of wood was carried out. It was shown that cellulose is present in its amorphous and crystalline forms, the presence of lignin was unambiguously confirmed by the signals of aromatic carbon atoms, and hemicelluloses were detected by the signals from the carbon atoms of methyl groups of acetylxylose and L-rhamnose. According to the integral intensities, the total ratio of cellulose and hemicelluloses to lignin was determined: the largest amount of lignin was found in coniferous wood (spruce, larch and pine), and the smallest amount of lignin was detected in deciduous species (aspen, oak, linden, birch and poplar).

Insight into humic substances with cotton straw derived amendments by solid state 13C NMR and FTIR spectroscopy

Carbon sequestration of organic materials and biochar in soil is a vital way to increase soil organic carbon (SOC), but the stability of SOC especially the humic substances (HS) is different with these amendments. In this study, cotton straw, compost derived from cotton straw (compost) and biochar derived from cotton straw (biochar) were added with equivalent carbon content into soil and incubated for 180 days. The structural characteristics of humic acid (HA), fulvic acid (FA) and humin (Hu) was studied by solid-state 13C nuclear magnetic resonance (NMR) spectroscopy and Fourier transform infrared (FTIR) spectroscopy. The results showed that the aryl C of Hu and FA increased by biochar treatment or biochar incorporated straw or compost and decreased with low ratio of biochar incorporated straw or compost. In addition, phenolic C of Hu and HA increased by straw treatment or biochar incorporated straw and increased with low ratio of biochar incorporated straw or compost. However, O-alkyl C of Hu and HA increased by compost treatment or biochar incorporated compost and increased with low ratio of biochar incorporated straw or compost. These results suggest that the stability of FA amended with straw or compost can be enhanced by incorporating biochar through increasing aryl functional groups, but the stability of HA amended with straw or compost can be enhanced by incorporating biochar through increasing alkyl groups. Biochar was in favor of aryl C formation of FA and Hu, while straw or compost was beneficial to alkyl C formation of HA and Hu.

Isolated-alkene-linked porous organic polymers (BIT-POPs): Facile synthesis via ROMP and distinguishing overlapped signals in solid-state 13C NMR

Porous organic polymers (POPs) represented a class of promising materials for delivering environmental and energy issues worldwide. However, the nature of amorphous makes their structure characterization in the solid state...

SOLID-STATE 13C NMR SPECTROSCOPY IN POLYSACCHARIDE ANALYSIS

Polysaccharides are high molecular weight compounds represented by long linear and/or branched chains of monosaccharide residues linked by a glycosidic bond. Currently, there is a huge and rapidly-growing interest in the chemistry of polysaccharides due to their widespread use in various spheres of human life. The study of polysaccharide structure is a complex and non-trivial task, and in this area solid-state 13C NMR spectroscopy are widely applied in recent years. The review analyzes the possibilities of solid-state 13C NMR spectroscopy for the study of polysaccharides and natural objects containing polysaccharides. The evolution of 13C solid-state NMR spectroscopy methods is shown with the main focus on the usage of the cross-polarization (CP) technique based on rotating the sample under the magic angle (MAS), since in this case the spectra are obtained without artifacts signals and with the best signal-to-noise ratio and high resolution. The review focuses on cellulose as the most widespread polysaccharide, in addition, the applicability of CP-MAS 13C NMR spectroscopy for the study of other polysaccharides, as well as plant materials, is considered. The represented examples clearly show that CP-MAS 13C NMR spectroscopy is the most powerful experimental method that allows to obtain information on both the composition and structure of polysaccharides, as well as the composition of various plant materials. Moreover, the combination of available equipment and various techniques of solid-state 13C NMR experiment will contribute to the progress of further research in the chemistry of polysaccharides and their derivatives.