Enzymatic sensor of putrescine with optical oxygen transducer — mathematical model of responses of sensitive layer

A biosensor for putrescine containing a sensing layer with an optical oxygen probe based on ruthenium complex and the enzyme diamine oxidase from pea is described. The diamine oxidase was pre-immobilised on broken micro-beads modified with a ferrofluid. The pre-immobilised enzyme and ruthenium complex were both incorporated into the UV-cured inorganic-organic hybrid polymer ORMOCER® and deposited on a lens to form a sensitive layer of 210 µm in thickness. The sensitivity to the putrescine concentration determined under air saturation was between 3.50 µs L mmol^?1 and 4.50 µs L mmol^?1 in a hundred experiments conducted intermittently over a one year period. With the oxygen concentration increasing from 10 % to 100 % of DO (dissolved oxygen), the biosensor sensitivity decreased from 6.87 µs L mmol^?1 to 0.70 µs L mmol^?1 and its dynamic range increased from 0.10 mmol L^?1 to 1.75 mmol L^?1. To estimate the behaviour of the putrescine sensor in parametric space, a mathematical model of the reaction-transport processes inside the sensing layer was developed. The model revealed the qualitative relations between the sensor analytical features, the characteristics of the sensitive layer and concentrations of substrates. The results of the mathematical modelling may serve as guidelines in the design of optodes for specific applications.     

Extending the threshold values for inverse-positivity of a linear fourth order operator

Positivity - In this paper, we study sufficient conditions for the (strict) inverse-positivity of the linear fourth order operator corresponding to the one-dimensional beam equation with a...     

Monitoring of Portland cement chemical reaction and quantification of the hydrated products by XRD and TG in function of the stoppage hydration technique

Journal of Thermal Analysis and Calorimetry - Cement hydration occurs according to a sequence of reactions whose products have a direct influence on the working properties of concretes and mortars...     

Self‐recovery and fatigue of double‐network gels with permanent and reversible bonds

Double‐network (DN) gels subjected to cyclic deformation (stretching up to a fixed strain followed by retraction down to the zero stress) demonstrate a monotonic decrease in strain with time (self‐recovery). Observations show that the duration of total recovery varies in a wide interval (from a few minutes to several days depending on composition of the gel), and this time is strongly affected by deformation history. A model is developed for the kinetics of self‐recovery. Its ability to describe stress–strain diagrams in cyclic tests with various periods of recovery is confirmed by comparison with observations on several DN gels. Numerical simulation reveals pronounced enhancement of fatigue resistance in multi‐cycle tests with stress‐ and strain‐controlled programs when subsequent cycles of deformation are interrupted by intervals of recovery. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 438–453     

Synthesis of Fucose-Containing Disaccharides by Glycosylhydrolases from Various Origins

Applied Biochemistry and Biotechnology - Glycosylhydrolases of various origins were used to produce fucose-containing disaccharides with prebiotic potential using different donor substrates and...     

Disposable Stochastic Sensors for the Simultaneous Assay of Acetylcholine and Dopamine in Whole Blood Samples

Acetylcholine and dopamine are neurotransmitters important for aging and brain pathology. Their assay in whole blood is essential for fast and early detection of neurodegenerative disorders. Therefore, polymeric textile covered with a thin layer of Ag was used to provide stochastic sensors modified with maltodextrins presenting different dextrose equivalence: Maltodextrin I (dextrose equivalence 13.0–17.0), and Maltodextrin II (dextrose equivalence 16.5–19.5). These stochastic sensors were used reliable for both qualitative and quantitative analysis of acetylcholine and dopamine in whole blood samples. Their sensitivity and selectivity were high, and they were reliable for the assay of dopamine and acetylcholine in whole blood samples, with recoveries higher than 98.00%, and relative standard deviations (%) values lower than 1.00%.     

In Vivo Anti-Inflammatory Effect,Antioxidant Activity,and Polyphenolic Content of Extracts from Capsicum chinense By-Products

By-products of Capsicum chinense Jacq., var Jaguar could be a source of bioactive compounds. Therefore, we evaluated the anti-inflammatory effect, antioxidant activity, and their relationship with the polyphenol content of extracts of habanero pepper by-products obtained from plants grown on black or red soils of Yucatán, Mexico. Moreover, the impact of the type of extraction on their activities was evaluated. The dry by-product extracts were obtained by maceration (ME), Soxhlet (SOX), and supercritical fluid extraction (SFE). Afterward, the in vivo anti-inflammatory effect (TPA-induced ear inflammation) and the in vitro antioxidant activity (ABTS) were evaluated. Finally, the polyphenolic content was quantified by Ultra-Performance Liquid Chromatography (UPLC), and its correlation with both bioactivities was analyzed. The results showed that the SFE extract of stems of plants grown on red soil yielded the highest anti-inflammatory effect (66.1 ± 3.1%), while the extracts obtained by ME and SOX had the highest antioxidant activity (2.80 ± 0.0052 mM Trolox equivalent) and polyphenol content (3280 ± 15.59 mg·100 g⁻¹ dry basis), respectively. A negative correlation between the anti-inflammatory effect, the antioxidant activity, and the polyphenolic content was found. Overall, the present study proposed C. chinense by-products as a valuable source of compounds with anti-inflammatory effect and antioxidant activity.