A general approach to cellulosic material with controlled slow release of active substances by derivatization of a cellulosic carrier matrix with trifunctional triazines

Novel trifunctional triazines (“TATORT reagents”) for the modification of cellulosic material were prepared from cyanuric chloride. The compounds employ a cellulose-reactive anchor group for fixation, an active substance showing slow release properties, and a reactivity tuner to facilitate release control. According to this approach, humidity acts as an external trigger to “switch on” the slow-release. While the release-compounds are completely stable under dry conditions, the active substances are released simply by surrounding moisture. The reactivity tuner controls the rate of the release: by choosing an appropriate tuner, the concentration maximum can be set anytime between minutes and several weeks. The release kinetics depends mainly on the structure of reactivity tuner and active substance, but only insignificantly on the type of the (cellulosic) carrier matrix. Apart from the inherent limitation to phenolic and carboxylic active substances, the approach is quite general as the active substances may encompass wide ranges of compounds and applications.     

Lignin Quantification of Papyri by TGA—Not a Good Idea

Papyri belong to the oldest writing grounds in history. Their conservation is of the highest importance in preserving our cultural heritage, which is best achieved based on an extensive knowledge of the materials’ constituents to choose a tailored conservation approach. Thermogravimetric Analysis (TGA) has been widely employed to quantify cellulose and lignin in papyrus sheets, yielding reported lignin contents of 25% to 40%. In this work, the TGA method conventionally used for papyrus samples was repeated and compared to other lignin determination approaches (Klason-lignin and acetyl bromide-soluble lignin). TGA can lead to a large overestimation of the lignin content of commercial papyrus sheets (~27%) compared to the other methods (~5%). A similar overestimation of the lignin content was found for the pith and rind of the native papyrus plant. We concluded that the TGA method should, therefore, not be used for lignin quantification.     

On nonanalytic solitary waves formed by a nonlinear dispersion

We study the prototypical, genuinely nonlinear, K(m, n) equation, u_t ± a(u^m)_x + (uⁿ)_xxx = 0, a = const, which exhibits a number of remarkable dispersive effects. In particular, the distinguished subclass wherein m = n + 2 is transformed into a new, purely dispersive equation free of convection. In addition to compactons, the K(m, n) can support both kinks and solitons with an infinite slope(s), periodic waves and dark solitons with cusp(s) all being manifestations of nonlinear dispersion in action. For n < 0 the enhanced dispersion at the tail may generate algebraically decaying patterns.     

Dissolution of rayon fibers for size exclusion chromatography: a challenge

Application of size exclusion chromatography (SEC) for the analysis of cellulose samples is often limited due to poor solubility in the solvent system N,N-dimethylacetamide/lithium chloride (DMAc/LiCl). Hence different activation or derivatization methods have been developed and published. Most of these methods are laborious, influence the molar mass distribution or do not support dissolution of manmade fibers, such as viscose rayon. In this study, we have evaluated different activation methods for their applicability in viscose rayon dissolution and we present a novel method for activation. We found that an additional solvent exchange step with dimethyl sulfoxide (DMSO) increases and accelerates solubility of viscose fibers in DMAc/LiCl for subsequent SEC analysis. The improved dissolution by DMSO activation is mainly due to increased swelling and improved action towards the outer skin of the fiber. The novel approach has also been applied to the even more difficult dissolution of oxidized viscose fibers.     

Synthesis of novel 3-oxa-chromanol type antioxidants

Condensation of trimethylhydroquinone with aldehydes provides 2,4-disubstituted 5,7,8-trimethyl-4H-benzo[1,3]dioxin-6-ols in a straightforward one-pot reaction. These compounds are 3-oxa-derivatives of α-tocopherol (vitamin E) and represent an interesting novel class of phenolic antioxidants. The formation reaction proceeds according to a two-step mechanism consisting of electrophilic substitution and acetalization, and provides the product as a cis/trans-mixture of diastereomers.     

Determination of carbohydrate- and lignin-derived components in complex effluents from cellulose processing by capillary electrophoresis with electrospray ionization-mass spectrometric detection

Degradation products from lignocellulosic materials receive increasing attention due to the continuously growing interest in their utilization. The inherent structural variance of lignocellulosics combined with the intricacy of lignocellulosic processing (e.g. pulping of wood and bleaching of cellulosic pulps) and the complexity of degradation processes occurring therein result in rather complex mixtures in the process streams and effluents that contain a large quantity of structurally different degradation products. This is true for most processing steps, but also for degradation reactions occurring during aging of lignocellulosic materials, such as paper, cellulosic tissue or textiles. In order to render such mixtures better analytically accessible than hitherto possible a CE-ESI-MS method was established for the simultaneous determination of aliphatic carboxylic acids from the degradation of (hemi)celluloses and aromatic compounds from lignin degradation. CE and ESI-MS parameters have been optimized towards sensitivity and good reproducibility. The method was tested in two real-world scenarios: the determination of major components in effluents from bleaching stages in the pulp and paper industry, and the analysis of degradation products in extracts of naturally aged papers. The advantages and drawbacks of this approach are critically discussed.     

Analyzing the effects of thermal stress on insulator papers by solid-state 13C NMR spectroscopy

Cellulose - Million tons of cellulosic paper have been used for insulating coils in oil-filled electrical power transformers, thereby assuring the electricity supply for our societies. The high...     

Impact of residual extractives on the thermal stability of softwood Kraft pulp

Cellulose - Wood extractives are known to cause problems during the production of pulp and paper and to impact their mechanical properties. In the present work, we systematically explored whether...     

A Cerberus‐Inspired Anti‐Infective Multicomponent Gatekeeper Hydrogel against Infections with the Emerging “Superbug” Yeast Candida auris

The pathogenic yeast Candida auris has received increasing attention due to its ability to cause fatal infections, its resistance toward important fungicides, and its ability to persist on surfaces including medical devices in hospitals. To brace health care systems for this considerable risk, alternative therapeutic approaches such as antifungal peptides are urgently needed. In clinical wound care, a significant focus has been directed toward novel surgical (wound) dressings as first defense lines against C. auris. Inspired by Cerberus the Greek mythological “hound of Hades” that prevents the living from entering and the dead from leaving hell, the preparation of a gatekeeper hybrid hydrogel is reported featuring lectin‐mediated high‐affinity immobilization of C. auris cells from a collagen gel as a model substratum in combination with a release of an antifungal peptide drug to kill the trapped cells. The vision is an efficient and safe two‐layer medical composite hydrogel for the treatment of severe wound infections that typically occur in hospitals. Providing this new armament to the repertoire of possibilities for wound care in critical (intensive care) units may open new routes to shield and defend patients from infections and clinical facilities from spreading and invasion of C. auris and probably other fungal pathogens.