Biodegradable composites with improved barrier properties and transparency from the impregnation of PLA to bacterial cellulose membranes

Poly(lactic acid) (PLA) was impregnated in bacterial cellulose (BC) membranes. BC/PLA films were prepared by solvent casting and mechanical, optical and barrier properties, and biodegradation process were investigated. The transparency of processed films was higher than that of neat BC and increased with PLA content. Moreover, the incorporation of PLA to BC enhanced significantly the water vapor barrier properties of the BC membranes. The bionanocomposites contained a high percentage of cellulose due to the impregnation method that leads to the film with a BC content of 94%, which practically maintains the excellent mechanical properties of BC. However, when increasing the PLA content in the bionanocomposites the mechanical properties decreased slightly with respect to BC. Biodegradation under real soil conditions was determined indirectly through the study of the visual degradation and disintegration, demonstrating that the bionanocomposites were degraded faster than the neat PLA. The successful production of BC/PLA bionanocomposites suggested the possible application of them for active food packaging. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43669.     

Quantitative Analysis of Bioactive Compounds from Aromatic Plants by Means of Dynamic Headspace Extraction and Multiple Headspace Extraction‐Gas Chromatography‐Mass Spectrometry

Seven monoterpenes in 4 aromatic plants (sage, cardamom, lavender, and rosemary) were quantified in liquid extracts and directly in solid samples by means of dynamic headspace‐gas chromatography‐mass spectrometry (DHS‐GC‐MS) and multiple headspace extraction‐gas chromatography‐mass spectrometry (MHSE), respectively. The monoterpenes were 1st extracted by means of supercritical fluid extraction (SFE) and analyzed by an optimized DHS‐GC‐MS. The optimization of the dynamic extraction step and the desorption/cryo‐focusing step were tackled independently by experimental design assays. The best working conditions were set at 30 °C for the incubation temperature, 5 min of incubation time, and 40 mL of purge volume for the dynamic extraction step of these bioactive molecules. The conditions of the desorption/cryo‐trapping step from the Tenax TA trap were set at follows: the temperature was increased from 30 to 300 °C at 150 °C/min, although the cryo‐trapping was maintained at ?70 °C. In order to estimate the efficiency of the SFE process, the analysis of monoterpenes in the 4 aromatic plants was directly carried out by means of MHSE because it did not require any sample preparation. Good linearity (r² > 0.99) and reproducibility (relative standard deviation % <12) was obtained for solid and liquid quantification approaches, in the ranges of 0.5 to 200 ng and 10 to 500 ng/mL, respectively. The developed methods were applied to analyze the concentration of 7 monoterpenes in aromatic plants obtaining concentrations in the range of 2 to 6000 ng/g and 0.25 to 110 μg/mg, respectively.     

Mechanical and thermal properties of soy protein films processed by casting and compression

Soy protein isolate (SPI) based films are environmentally friendly because they are biodegradable and come from renewable sources but they are brittle. Different ratios of plasticizer were incorporated into SPI-based films to improve mechanical properties. Glycerol has a plasticizing effect on the films in the range of 30–40%. Apart from the plasticizer, the processing method employed to prepare films also influenced on the mechanical properties. Films processed by compression showed much better mechanical properties, higher tensile strength and elongation at break, than the ones processed by casting. Analysis of the thermal properties revealed that denaturation temperatures of the two main globulin fractions present in SPI were influenced by the moisture content of the sample but not by the processing method employed.     

D‐isosorbide and 1,3‐propanediol as plasticizers for starch‐based films: Characterization and aging study

In the present work, D‐isosorbide and 1,3‐propanediol are proposed as alternative plasticizers obtained from renewable resources. Plasticized starch films were prepared by solvent casting method. The influence of using different “green” plasticizers in the final properties of starch‐based films was analyzed. Besides, the characterization of the films was also performed after storage time in order to evaluate the effect of the plasticizer on aging. UV‐spectrophotometry results showed better optical properties for both glycerol and D‐isosorbide films with higher transparency. The thermal and mechanical properties resulted influenced by the nature of the plasticizer. It was demonstrated that water vapor permeability was governed by the starch‐water interactions, whereas the oxygen permeability depended on the plasticizer's nature. The storage time affected the surface, mechanical, and thermal properties of the plasticized starch films. Atomic force microscopy results concluded that the topography of the films changed due to aging. The use of D‐isosorbide as plasticizer reduced the evolution of the mentioned properties and enhanced the reliability of the material. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44793.     

Profile of TREM2-Derived circRNA and mRNA Variants in the Entorhinal Cortex of Alzheimer’s Disease Patients

Genetic variants in TREM2, a microglia-related gene, are well-known risk factors for Alzheimer’s disease (AD). Here, we report that TREM2 originates from circular RNAs (circRNAs), a novel class of non-coding RNAs characterized by a covalent and stable closed-loop structure. First, divergent primers were designed to amplify circRNAs by RT-PCR, which were further assessed by Sanger sequencing. Then, additional primer sets were used to confirm back-splicing junctions. In addition, HMC3 cells were used to assess the microglial expression of circTREM2s. Three candidate circTREM2s were identified in control and AD human entorhinal samples. One of the circRNAs, circTREM2_1, was consistently amplified by all divergent primer sets in control and AD entorhinal cortex samples as well as in HMC3 cells. In AD cases, a moderate negative correlation (r = −0.434) was found between the global average area of Aβ deposits in the entorhinal cortex and circTREM2_1 expression level. In addition, by bioinformatics tools, a total of 16 miRNAs were predicted to join with circTREM2s. Finally, TREM2 mRNA corresponding to four isoforms was profiled by RT-qPCR. TREM2 mRNA levels were found elevated in entorhinal samples of AD patients with low or intermediate ABC scores compared to controls. To sum up, a novel circRNA derived from the TREM2 gene, circTREM2_1, has been identified in the human entorhinal cortex and TREM2 mRNA expression has been detected to increase in AD compared to controls. Unraveling the molecular genetics of the TREM2 gene may help to better know the innate immune response in AD.     

Relating cyclic voltammetry and impedance analysis in a viologen electrochromic device

Viologens are electrochromic materials that have a wide range of coloration depending on the radical substituents. The results for a new blue viologen-based device, that has recently been patented, with an active area of 8.5 cm² is presented in this paper. The characterization techniques used are based on optical measurements, chronoamperometry, cyclic voltammetry, and impedance spectroscopy analysis. A study of the results obtained from these measurements provides both an overview of the reactions taking place and has allowed an equivalent circuit to be developed which relates the different electrochemical parameters. The transmittance is observed to change from 80% to 15% in 600 nm for input voltages ranging from 0 to 2.5 V. However, increasing voltage beyond 1.8 V shows no optical change, thus, maintaining the voltage below this level optimizes the use of electrical current. Voltages and charges used for each redox reaction have been computed and are seen to be linearly related. The equivalent circuit generated to mimic the process has included parameters based on Warburg diffusion and double-layer capacitances. Results from this model are consistent with measurements for up to 1.8 V. Saturation of reduced species has been deduced for input voltages beyond this level.     

Significance of changes in blood pressure and pulse rate after percutaneous liver biopsy

Blood-pressure and pulse-rate changes were evaluated prospectively in 50 patients undergoing uncomplicated liver biopsies and retrospectively in 4 patients who, since 1973, had recognized postbiopsy hemorrhage requiring transfusion. In uncomplicated biopsies a wide range of variations in vital signs was encountered between "baseline" and "before" controls and between controls and postbiopsy measurements. To place the changes in perspective, percentile scales were developed for percent maximum deviation from control for systolic blood pressure, diastolic blood pressure, and pulse rate. Analysis of changes in patients with significant hemorrhage revealed; (1) marked changes in vital signs in the early (2-hr) postbiopsy period; (2) the association of early hypertensive changes with pain followed by later evidence of hemorrhage in two of the four patients; (3) the lesser helpfulness of pulse change (1 of 4 bleeders) as compared to blood pressure change (4 of 4 patients).     

Click Crosslinked Chitosan/Gold Nanocomposite Hydrogels

Preparation of novel nanocomposite hydrogels opens up new avenues to next generation of biocompatible materials to be used in bioengineering and drug delivery. Toward this goal, chitosan nanocomposite hydrogels using click chemistry inspired cross‐linking are prepared. To enable this, Diels–Alder reaction of furan‐containing chitosan and maleimide‐coated gold nanoparticles is employed. The viscoelastic properties of the obtained nanocomposites as well as the effect of the nanoparticles as cross‐linkers are studied, indicating that they play significant role in hydrogel formation and stability. Nanoparticle‐enriched hydrogels are also found to demonstrate pH‐sensitivity therefore showing their potential for future biosensing applications.

     

Bladder cancer and squamous metaplasia in spinal cord injury patients

The influence of long-term indwelling urethral catheterization was studied by random bladder and urethral biopsies in 62 spinal cord injury patients. Six patients (10 per cent) had diffuse squamous cell bladder carcinoma, 4 of whom had no tumor visible endoscopically. Five of the patients with cancer were among 25 patients (20 per cent) managed with an indwelling urethral catheter for more than 10 years (average 21 years, range 15 to 30 years). The other cancer patient had been free of the catheter for 27 years after suprapubic cystotomy for 4 years. Gross and microscopic hematuria was associated with cancer. Squamous metaplasia of the bladder was significantly greater in patients who had been catheterized for more than 10 years (80 per cent), compared to those catheterized for less than 10 years (42 per cent) and patients without catheters (20 per cent). Urethral squamous metaplasia increased slightly in long-term catheterization patients. Urinary infection was universal and did not distinguish patients with inflammation, metaplasia or cancer. Therefore, the duration of indwelling catheterization seems to be the major factor in squamous changes in these patients.