Effect of ethylene-co-vinyl acetate-glycidylmethacrylate and cellulose microfibers on the thermal,rheological and biodegradation properties of poly(lactic acid) based systems

The properties and biodegradation behavior of blends of poly(lactic acid) (PLA) and ethylene-vinyl acetate-glycidylmethacrylate copolymer (EVA-GMA), and their composites with cellulose microfibers (CF) were investigated. The blends and composites were obtained by melt mixing and the morphology, phase behavior, thermal and rheological properties of PLA/EVA-GMA blends and PLA/EVA-GMA/CF composite films were investigated as a function of the composition. The disintegrability in composting conditions was examined by means of morphological, thermal and chemical analyses to gain insights into the post-use degradation processes. The results indicated a good compatibility of the two polymers in the blends with copolymer content up to 30 wt.%, while at higher EVA-GMA content a phase separation was observed. In the composites, the presence of EVA-GMA contributes to improve the interfacial adhesion between cellulose fibers and PLA, due to interactions of the epoxy groups of GMA with hydroxyls of CF. The addition of cellulose microfibers in PLA/EVA-GMA system modifies the rheological behavior, since complex viscosity increased in presence of fibers and decreased with an increase in frequency. Disintegration tests showed that the addition of EVA-GMA influence the PLA disintegration process, and after 21 days in composting conditions, blends and composites showed faster degradation rate in comparison with neat PLA due to the different morphologies induced by the presence of EVA-GMA and CF phases able to allow a faster water diffusion and an efficient PLA degradation process.     

Micellization and Clouding Phenomenon of Phenothiazine Drug Promethazine Hydrochloride: Effect of NaCl and Urea Addition

Herein we report the micellization and clouding behavior of promethazine hydrochloride (PMT) in absence and presence of NaCl/ureas. The critical micelle concentration (CMC) of PMT is measured by conductivity method and the values decrease with increasing the NaCl concentration. With increasing the temperature, the CMC first increases then decreases. At 25°C, the maximum CMC values were obtained (with or without NaCl). The thermodynamic parameters are evaluated which indicate more stability of the PMT solution in presence of NaCl. PMT shows phase separation also. The cloud point (CP) of PMT decreases with increase in pH due to deprotonation of the drug molecules. Ureas decreased the CP and the behavior is explained on the basis of removal of water from the head group region.     

Acyclovir-Loaded Chitosan Microspheres for Gastroretention: Development and Evaluation

Mucoadhesive chitosan microspheres of acyclovir were prepared to prolong the gastric residence time using simple emulsification phase separation technique. The particle morphology of drug-loaded formulations was measured by SEM and the particle size distribution was determined using an optical microscope. The release profile of acyclovir from microspheres was examined in simulated gastric fluid (SGF pH 1.2). The particles were found to be discreet and spherical with the maximum particles of an average size (31.62 ± 4.64). The entrapment efficiency was found to be in the range of 40.24 to 67.29%. The concentration of the glutaraldehyde (25%v/v) as a cross-linker 2 ml and drug polymer ratio of 1:2 caused an increase in the entrapment efficiency and the extent of drug release. The optimized chitosan microspheres were found to possess good bioadhesion (79.89 ± 1.01%). The gamma-scintigraphy study showed the gastric residence time of more than 6 hours which revealed that optimized formulation could be a good choice for gastroretentive systems.     

Liquid crystalline banana‐shaped monomers derived from 2,7‐naphthalene: synthesis and properties

Three banana‐shaped monomers, i.e. 2,7‐naphthalene bis[4‐(4‐allyloxyphenylazo)‐benzoate], 2,7‐naphthalene bis[4‐(4‐allyloxy‐3‐fluorophenylazo)benzoate] and 2,7‐naphthalene bis{4‐[4‐(10‐undecenyloxy)phenylazo]benzoate}, containing azobenzene as side arms, 2,7‐dihydroxynaphthalene as central units and terminal double bonds as polymerisable functional groups, were synthesised and their mesophase behaviour investigated. Polarizing optical microscopy and DSC measurements reveal that all compounds exhibit nematic mesophases. The absorption spectrum of the trans‐azobenzene groups displays a high‐intensity π–π* transition at about 365 nm and a low‐intensity n–π* transition at around 450 nm for all compounds. Hence, photochromism can be achieved by the introduction of the azo linkage to banana‐shaped liquid crystals molecules.     

Mechanism of structure formation of microbial cellulose during nascent stage

The structure of microbial cellulose (MC) produced by Acetobacter xylinum was studied in presence of Fluorescent Brightener, Direct Blue 1, 14, 15, 53, Direct Red 28, 75 and 79, as probe. X-ray diffraction pattern of the product showed that it was a crystalline complex of dye and cellulose. The product has the structure in which the monomolecular layer of the dye molecule is included between the cellulose sheets corresponding to the ( $ 1\bar{1}0 $ ) planes of microbial cellulose. As a result of dye inclusion, d-spacing of lower angle plane (100) of products becomes 8.0–8.8 Å instead of 6.1 Å of MC. The d-spacing for the higher angle plane must be (010) plane due to stronger van der Waals forces between the pyranose rings which reduced 5.3 Å space of (110) plane of MC to 3.9–4.5 Å in the product. However, cellulose regenerated from FB, DR28 products was cellulose I and IV, respectively, and that from each DB1, 14, 15, 53, DR75 and 79 products was cellulose II. Solid state ¹³C NMR and deuteration-IR showed the product was non-crystalline which was contrasted to X-ray results. The regenerated celluloses were cellulose I_β, IV_I and II, respectively. Thus the structure of the product depends on the characteristics of dye which affects the conformation of cellulose at the nascent stage by the direct interaction with cellulose chains. The different regenerated celluloses as well as different fine structure in the same cellulose allomorph were produced depending mainly on number and position of the sulfonate groups in the dye.     

Photo‐ and pH‐Tunable Multicolor Fluorescent Nanoparticle‐Based Spiropyran‐ and BODIPY‐Conjugated Polymer with Graphene Oxide

We report a stimuli‐responsive fluorescent nanomaterial, based on graphene oxide coupled with a polymer conjugated with photochromic spiropyran (SP) dye and hydrophobic boron dipyrromethane (BODIPY) dye, for application in triggered target multicolor bioimaging. Graphene oxide (GO) was reduced by catechol‐conjugated polymers under mildly alkaline conditions, which enabled to formation of functionalized multicolor graphene nanoparticles that can be induced by irradiation with UV light and by changing the pH from acidic to neutral. Investigation of these nanoparticles by using AFM, fluorescence emission, and in vitro cell and in vivo imaging revealed that they show different tunable colors in bioimaging applications and, more specifically, in cancer‐cell detection. The stability, biocompatibility, and quenching efficacy of this nanocomposite open a different perspective for cell imaging in different independent colors, sequentially and simultaneously.     

Brief survey on phytochemicals to prevent COVID-19

BackgroundThe recent pandemic by COVID-19 is a global threat to human health. The disease is caused by SARS-CoV-2 and the infection rate is increased more quickly than MERS and SARS as their rapid adaptation to varied climatic conditions through rapid mutations. It becomes more severe due to the lack of proper therapeutic drugs, insufficient diagnostic tool, scarcity of appropriate drug, life supporting medical facility and mostly lack of awareness. Therefore, preventive measure is one of the important strategies to control. In this context, herbal medicinal plants received a noticeable attention to treat COVID-19 in Indian subcontinent. Here, 44 Indian traditional plants have been discussed with their novel phytochemicals that prevent the novel corona virus. The basic of SARS-CoV-2, their common way of transmission including their effect on immune and nervous system have been discussed. We have analysed their mechanism of action against COVID-19 following in-silico analysis. Their probable mechanism and therapeutic approaches behind the activity of phytochemicals to stimulate immune response as well as inhibition of viral multiplication discussed rationally. Thus, mixtures of active secondary metabolites/phytochemicals are the only choice to prevent the disease in countries where vaccination will take long time due to overcrowded population density.     

Poly (methyl methacrylate) grafted wheat straw for economical and eco-friendly treatment of oily wastewater

Cellulose - The sustainable development of oil–gas and petrochemical industries necessitates the development of cost-effective and eco-friendly technologies to treat mass-produced oily...     

Concerted effect of boron and porosity on shear thickening behavior of hybrid mesoporous silica dispersions

In the present work, the influence of porosity and boron on shear thickening behavior of hybrid mesoporous silica has been studied. Three different levels of boron modification were performed by varying the molar composition of boric acid viz., 1.5 mmol, 2.5 mmol, and 3.5 mmol in a co-condensation approach. The incorporation of boron in mesoporous silica network was confirmed by various techniques such as Fourier transform infra-red (FTIR), and ¹¹B solid- state nuclear magnetic resonance (NMR) spectroscopy. The morphology and particle size were confirmed by using scanning and transmission electron microscopy. To evaluate the effect of boron and porosity on the shear thickening behavior, dispersions were prepared from mesoporous boron- modified silica (MSiB), control mesoporous silica (MSi), non-porous boron-modified silica (SiB), and control non-porous silica (Si) in polyethylene glycol. The shear thickening behavior was studied using steady shear rheology. The dispersion prepared from different loadings of synthesized MSiB containing 1.5 mmol boron showed more than 16 times increase in viscosity (657.7 Pa.s) compared to that of MSi (39.2 Pa.s) at a fairly low volume fraction (φ = 0.15) of silica. It is expected that the highly ordered mesoporous architecture of hybrid silica has improved the interaction between the particle and the dispersing medium through hydrogen bonding. The porous morphology of the hybrid mesoporous silica as well as the incorporation of boron in the silica network favors the formation of a frictional contact network, and a transition from continuous shear thickening (CST) to discontinuous shear thickening (DST) behavior was observed. Therefore, silica prepared via incorporation of boron as well as porosity can be material of interest in variety of applications, for example, soft body armors, sporting goods, and shear thickening electrolytes for high impact resistant batteries.