Role of catalyst supports in biocatalysis

Biocatalysis utilizes enzymes and microbial cells as catalysts for a wide range of applications in biotechnology. Immobilization of biocatalysts on various materials has several advantages, including the capacity for reuse, quick reaction termination, easy biocatalyst recovery and operational stability. The present article focuses on the use of material supports for developing immobilized biocatalysts in applications related to energy, environment and chemical synthesis. The work provides a comprehensive overview of a broad class of materials, including organic, inorganic and composites, that have been shown to be prosperous candidates to support the immobilization of enzymes and microbial cells. It also highlights the properties of nanomaterial support such as large surface area and comfort compartment for immobilization. The availability of different types of materials as catalyst support provides an opportunity to understand and develop efficient biocatalytic systems. The choice of selecting a catalyst support will mostly depend on the interaction of the material with the enzyme or microbial cell. Finally, potential challenges, future approaches in developing immobilized biocatalytic systems for various applications and novel material supports are suggested. © 2022 Society of Chemical Industry (SCI).     

Polyurethane networks from formiated soy polyols: Synthesis and mechanical characterization

Polyurethanes can be prepared using polyols obtained from vegetable oils in natura, such as castor oil, or from functionalized vegetable oils, such as hydroxylated soybean oil. These polyurethanes have different valuable properties, determined by their chemical composition and cross-linking density. In this study, soy epoxy polyols with different OH contents were prepared through a one-step reaction using the method of in situ performic acid generation. Polyols with OH functionalities from 1.9 to 3.2 were reacted in bulk with different diisocyanates at a NCO/OH molar ratio of 0.8 and 60°C for 24 h. Mechanical properties of the polyurethanes were determined by dynamic mechanical thermal analysis, hardness (Shore A), and swelling measurements. Polymer networks with glass-transition temperatures (T _g ) from −13 to 48°C were obtained. We observed that the higher the OH functionality of the polyols, the higher the T _g and cross-linking density of the polyurethane network. The influence of diisocyanate structure (rigid or flexible chain), curing temperature, and curing reaction time on mechanical properties was also investigated.     

Experimental investigation of the release mechanism of proxyphylline from silicone rubber matrices

The release process of a water soluble, model drug (proxyphylline) with small, yet not negligible osmotic action, from silicone rubber (SR) matrices is presented. The kinetics of release for different initial loads of the drug is supplemented by measurements of the kinetics of the concurrent water uptake. To gain insight on the relevant non‐Fickian transport mechanisms, the morphology, the diffusion, and sorption properties of the drug‐depleted matrices are studied. In addition, both drug‐loaded and drug‐depleted matrices are characterized with respect to their mechanical properties. The combined information derived from these techniques support—at least below the percolation threshold—the operation of a release mechanism occurring through a uniformly swollen polymer matrix without formation of cracks, in contrast to the release observed in the case of water soluble, inorganic salts where release takes place through a network of microscopic cracks. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effects of subphase pH and temperature on the interfacial behavior of double hydrophilic diblock copolymer PDEGMA-b-PDIPAEMA

The aggregation behavior of two pH- and temperature-responsive diblock copolymers of poly[di-(ethylene glycol) methyl ether methacrylate]-block-poly[2-(diisopropylamino) ethyl methacrylate] (PDEGMA-b-PDIPAEMA) at the air/water interface and the structures of their Langmuir–Blodgett (LB) films were studied by the Langmuir monolayer technique and atomic force microscopy, respectively. At the air/water interface, PDEGMA-b-PDIPAEMA tends to form the core-shell-corona micellar structure composed of a PDIPAEMA main chain core, an amino ethyl ester shell, and a PDEGMA corona. Under acidic, neutral, and alkaline conditions, PDIPAEMA blocks are completely protonated, partially protonated, and completely non-protonated, respectively, and the protonated amino ethyl ester groups are immersed in water before monolayer compression, whereas PDEGMA coronas are adsorbed at the interface. At pH 3, 7, and 10, the limiting areas (A₀) for PDEGMA42%-PDIPAEMA58% (weight percents) and PDEGMA55%-PDIPAEMA45% are 8.2/10.2/14.0 and 6.7/8.3/8.4 nm², respectively. The A₀ values of the former copolymer are larger than those of the latter. This is because the shells in the former copolymer are denser due to the higher polymerization degree of PDIPAEMA blocks, providing greater steric hindrance for PDEGMA coronas and making the latter more extended at the interface. In contrast to other copolymer systems, the effect of temperature on the isotherms of PDEGMA-b-PDIPAEMA is less obvious.     

Effect of water aging on the mechanical properties of flax fiber/bio-based resin composites

Present work investigates the effect of hydrothermal aging of flax fiber-reinforced bio-based epoxy resin laminates on the mechanical and thermomechanical properties of the composites. Three different types of bio-based resins were used. Plates reinforced with eight layers plain weave flax fibers of 150 g/m², manufactured using Resin Transfer Molding (RTM), compression molding or autoclave technique depends on type of the resin. One dimensional Fickian behavior shows a good fitting to the experimental data derived from weight measurements. The water uptake at the equilibrium state in the case of 60 °C temperature was slightly greater than that at 40 °C. The mechanical properties after hydrothermal aging show a significant reduction and do not return to their initial values even after the drying process. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48787.     

How Far Are We from Prescribing Fasting as Anticancer Medicine?

(1) Background: the present review provides a comprehensive and up-to date overview of the potential exploitation of fasting as an anticancer strategy. The rationale for this concept is that fasting elicits a differential stress response in the setting of unfavorable conditions, empowering the survival of normal cells, while killing cancer cells. (2) Methods: the present narrative review presents the basic aspects of the hormonal, molecular, and cellular response to fasting, focusing on the interrelationship of fasting with oxidative stress. It also presents nonclinical and clinical evidence concerning the implementation of fasting as adjuvant to chemotherapy, highlighting current challenges and future perspectives. (3) Results: there is ample nonclinical evidence indicating that fasting can mitigate the toxicity of chemotherapy and/or increase the efficacy of chemotherapy. The relevant clinical research is encouraging, albeit still in its infancy. The path forward for implementing fasting in oncology is a personalized approach, entailing counteraction of current challenges, including: (i) patient selection; (ii) fasting patterns; (iii) timeline of fasting and refeeding; (iv) validation of biomarkers for assessment of fasting; and (v) establishment of protocols for patients’ monitoring. (4) Conclusion: prescribing fasting as anticancer medicine may not be far away if large randomized clinical trials consolidate its safety and efficacy.     

Spontaneous Oleofoams from Water-in-Oil Emulsions

Spontaneously foaming oil systems have been formulated from water-in-oil emulsions by the controlled release and entrapment of gas in emulsified water droplets contained within the oil. The cascade of events leading to their formation is as follows: Two Span 60-emulsified populations of water droplets, one containing Na₂CO₃, the other 10% HCl and caseinate, were mixed in miglyol oil; the controlled coalescence of Na₂CO₃ droplets with the HCl ones served as a microreactor for the pH reduction and the subsequent release of CO₂ from Na₂CO₃; these gas microbubbles were arrested by sodium caseinate, stabilizing a microfoam within the water droplets; these droplets expanded under the rising gas pressure, spontaneously transforming the surrounding oil into a foamy oleogel containing water droplets.     

Smart Surfaces: Heterogeneous Photo-Catalysis on TiO2 Based Coatings for De-pollution Purposes in Indoor and Outdoor Environments

Topics in Catalysis - Heterogeneous photocatalysis using semiconductors, e.g. TiO2 as photocatalyst is a promising technology for the degradation of environmental pollutants. Preliminary evidence...