Antimicrobial powders and bio-based films

Food safety can be improved by various antimicrobial applications through the effective inhibition of microorganisms for certain periods by controlled release. Antimicrobials in powders and films were studied to investigate their activities and properties. Nisin (Nisaplin®) (200, 400, 600, 800, and 1000 IU/ml) was adsorbed to silica and different corn starches and their antimicrobial activities against Listeria monocytogenes were evaluated by agar diffusion assay. Nisin-adsorbed silica (Celpure P-65) powder had the highest antimicrobial activity at 600 IU/ml and also confirmed that the highest amount of nisin was adsorbed onto silica at the same concentration. Efficacy of both unmodified corn starch and modified corn starch for adsorption of nisin was less than that of silica due to low retained activity onto powder and much loss activity in supernatant during nisin-adsorbed powder processing. Nisaplin® and Guardian® incorporated gelatin films were evaluated for their film properties, and antimicrobial activities against Listeria monocytogenes in liquid media, solid media and ready-to-eat turkey bologna. As antimicrobial concentrations increased in films, intensity of yellowness increased and lightness decreased. Also, film tensile strength was reduced and elongation increased. Both oxygen permeability (OP) and water vapor permeability (WVP) of gelatin-based Nisaplin® films increased as antimicrobial concentration increased. OP of gelatin-based Guardian® films increased as level of incorporated antimicrobial increased while WVP decreased. Gelatin-based Nisaplin® films (0.025 ~ 0.5%) completely inhibited Listeria monocytogenes within 6 hours. Gelatin-based Guardian® films (0.5 ~ 3%) inhibited Listeria monocytogenes in liquid media and two lower concentrations (0.5% and 1%) were more effective at inhibiting Listeria monocytogenes than two higher concentration (2% and 3%). Antimicrobial activity of both films against Listeria monocytogenes on solid media were evaluated for 16 weeks and gelatin-based Guardian® films were more stable than gelatin-based Nisaplin® films. Both antimicrobial films effectively inhibited Listeria monocytogenes on bologna at 4℃ for 56 days. Gelatin films containing trans-2-dodecenal were developed and their antimicrobial activities against Listeria monocytogenes and Escherichia coli O157:H7 were evaluated in model system using peptone solution and turkey bologna. Also, film properties were evaluated. Trans-2-dodecenal gelatin films completely inhibited Listeria monocytogenes in 0.1% peptone solution within 8 hours. Also, this film reduced E. coli O157:H7 populations for 48 hours compared to control. Total color difference (∆E) of all treatments inoculated with Listeria monocytogenes increased during storage at 4℃ for 56 days. Films inoculated with E. coli O157:H7 also showed increased ∆E as storage time increased while there was no change in bologna from day 1 to 56 and ∆E was higher in order as follow 2% TD \u3e 1% TD \u3e Control \u3e Bologna. Trans-2-dodecenal impregnated gelatin film suppressed Listeria monocytogenes and E. coli O157:H7 on bologna pieces during storage at 4℃ for 56 days. Antimicrobial activity of films against Listeria monocytogenes was more effective than activity against E. coli O157:H7

Efficacy and Safety of Guardcel Nasal Packing After Endoscopic Sinus Surgery: A Prospective, Single-Blind, Randomized Controlled Study

Objectives Nasal packing after endoscopic sinus surgery is frequently used to control postoperative bleeding, enhance the wound healing process, and prevent lateralization of the middle turbinate, which causes insufficient ventilation. Many biodegradable materials have been developed to reduce pain and mucosal damage during packing removal. The purpose of this study was to compare the efficacy of Guardcel (Genewel Co.) middle meatal packing with a traditional nonabsorbable middle meatal packing, Merocel (Medtronic Xomed), on wound healing and patient satisfaction. Methods In this prospective, single-blind, randomized controlled study, we enrolled 32 consecutive patients (64 nostrils) undergoing bilateral endoscopic sinus surgery at Korea University Guro Hospital from February 2015 to August 2015. Guardcel and Merocel were inserted postoperatively into a randomly assigned side. Objective findings about bleeding, hemostasis, adhesion, and infection were evaluated with nasal endoscopy. Patients’ symptoms including pain and nasal obstruction were evaluated with a visual analog scale. Each evaluation was done at 2–3 days, 1 week, 2 weeks, and 4 weeks after surgery. Results At 2–3 days after endoscopic sinus surgery, the Guardcel side had a significantly less hemostasis time than the Merocel side (P=0.001). During this period, the pain during packing removal was significantly lower on the Guardcel-inserted side than the Merocel-inserted side (P=0.002). At two weeks after surgery, the adhesion score on the Guardcel side was significantly lower than that of the Merocel side (P=0.011). Other parameters during the study follow-up periods were not statistically significant. There were no severe adverse reactions. Conclusion Guardcel, a newly developed packing material, appeared to shorten the hemostasis time and reduce pain sensation at 2–3 days after surgery; it also prevented adhesion formation 2 weeks after surgery when compared with the control. Guardcel can be an effective and safe candidate to replace conventional packing materials after endoscopic sinus surgery

Eco-Friendly Cellulose Nanofiber Extraction from Sugarcane Bagasse and Film Fabrication

The development of cost-effective cellulose fibers by utilizing agricultural residues have been attracted by the scientific community in the past few years; however, a facile production route along with minimal processing steps and a significant reduction in harsh chemical use is still lacking. Here, we report a straightforward ultrasound-assisted method to extract cellulose nanofiber (CNF) from fibrous waste sugarcane bagasse. X-ray diffraction-based crystallinity calculation showed 25% increase in the crystallinity of the extracted CNF (61.1%) as compared to raw sugarcane bagasse (35.1%), which is coherent with Raman studies. Field emission scanning electron microscopy (FE-SEM) images revealed thread-like CNF structures. Furthermore, we prepared thin films of the CNF using hot press and solution casting method and compared their mechanical properties. Our experiments demonstrated that hot press is a more effective way to produce high strength CNF films; Young’s modulus of the thin films prepared from the hot press was ten times higher than the solution casting method. Our results suggest that a combination of ultrasound-based extraction and hot press-based film preparation is an efficient route of producing high strength CNF films

TEMPO-Oxidized Cellulose Nanofibril Films Incorporating Graphene Oxide Nanofillers

To design a new system of novel TEMPO-oxidized cellulose nanofibrils (TOCNs)/graphene oxide (GO) composite, 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation was utilized. For the better dispersion of GO into the matrix of nanofibrillated cellulose (NFC), a unique process combining high-intensity homogenization and ultrasonication was adopted with varying degrees of oxidation and GO percent loadings (0.4 to 2.0 wt%). Despite the presence of carboxylate groups and GO, the X-ray diffraction test showed that the crystallinity of the bio-nanocomposite was not altered. In contrast, scanning electron microscopy showed a significant morphological difference in their layers. The thermal stability of the TOCN/GO composite shifted to a lower temperature upon oxidation, and dynamic mechanical analysis signified strong intermolecular interactions with the improvement in Young’s storage modulus and tensile strength. Fourier transform infrared spectroscopy was employed to observe the hydrogen bonds between GO and the cellulosic polymer matrix. The oxygen permeability of the TOCN/GO composite decreased, while the water vapor permeability was not significantly affected by the reinforcement with GO. Still, oxidation enhanced the barrier properties. Ultimately, the newly fabricated TOCN/GO composite through high-intensity homogenization and ultrasonification can be utilized in a wide range of life science applications, such as the biomaterial, food, packaging, and medical industries

Ultra-flexible and rollable 2D-MoS2/Si heterojunction-based near-infrared photodetector: Via direct synthesis

Atomic two-dimensional (2D) transition metal dichalcogenides (TMDs) have attracted significant attention for application in various optoelectronic devices such as image sensors, biomedical imaging systems, and consumer electronics and in diverse spectroscopic analyses. However, a complicated fabrication process, involving transfer and alignment of as-synthesized 2D layers onto flexible target substrates, hinders the development of flexible high-performance heterojunction-based photodetectors. Herein, an ultra-flexible 2D-MoS2/Si heterojunction-based photodetector is successfully fabricated through atmospheric-pressure plasma enhanced chemical vapor deposition, which enables the direct deposition of multi-layered MoS2 onto a flexible Si substrate at low temperature (<200 °C). The photodetector is responsive to near infrared light (λ = 850 nm), showing responsivity of 10.07 mA W-1 and specific detectivity (D∗) of 4.53 × 1010 Jones. The measured photocurrent as a function of light intensity exhibits good linearity with a power law exponent of 0.84, indicating negligible trapping/de-trapping of photo-generated carriers at the heterojunction interface, which facilitates photocarrier collection. Furthermore, the photodetectors can be bent with a small bending radius (5 mm) and wrapped around a glass rod, showing excellent photoresponsivity under various bending radii. Hence, the device exhibits excellent flexibility, rollability, and durability under harsh bending conditions. This photodetector has significant potential for use in next-generation flexible and patchable optoelectronic devices. This journal is © The Royal Society of Chemistry.N

In-depth Investigation of Hg2Br2 Crystal Growth and Evolution

Physical vapor transport (PVT) has frequently been adopted for the synthesis of mercurous bromide (Hg2Br2) single crystals for acousto-optic modulators. However, thus far, very few in-depth studies have been conducted that elucidate the growth process of the Hg2Br2 single crystal. This paper reports an in-depth investigation regarding the crystal growth and evolution behavior of the Hg2Br2 crystal with facet growth mode. Based on the experimental and simulation results, the temperature profile conditions concerning the seed generation and seed growth could be optimized. Next, the PVT-grown Hg2Br2 crystals (divided into single crystal and quasi-single crystal regions) were characterized using various analysis techniques. The single-crystal Hg2Br2 was found to possess a more uniform strain than that of the quasi-single crystal through a comparison of the X-ray diffraction data. Meanwhile, the binding energy states and electron backscatter diffraction images of the as-synthesized Hg2Br2 crystals were similar, regardless of the crystal type. Furthermore, Raman spectroscopy and transmission electron microscopy analyses provided information on the atomic vibration mode and atomic structures of the two kinds of samples. The synergistic combination of the simulation and experimental results used to verify the growth mechanism facilitates the synthesis of high-quality Hg2Br2 crystals for potential acousto-optic tunable filter device applications

Computational Screening for Design of Optimal Coating Materials to Suppress Gas Evolution in Li-Ion Battery Cathodes

Ni-rich layered oxides are attractive materials owing to their potentially high capacity for cathode applications. However, when used as cathodes in Li-ion batteries, they contain a large amount of Li residues, which degrade the electrochemical properties because they are the source of gas generation inside the battery. Here, we propose a computational approach to designing optimal coating materials that prevent gas evolution by removing residual Li from the surface of the battery cathode. To discover promising coating materials, the reactions of 16 metal phosphates (MPs) and 45 metal oxides (MOs) with the Li residues, LiOH, and Li₂CO₃ are examined within a thermodynamic framework. A materials database is constructed according to density functional theory using a hybrid functional, and the reaction products are obtained according to the phases in thermodynamic equilibrium in the phase diagram. In addition, the gravimetric efficiency is calculated to identify coating materials that can eliminate Li residues with a minimal weight of the coating material. Overall, more MP and MO materials react with LiOH than with Li₂CO₃. Specifically, MPs exhibit better reactivity to both Li residues, whereas MOs react more with LiOH. The reaction products, such as Li-containing phosphates or oxides, are also obtained to identify the phases on the surface of a cathode after coating. On the basis of the Pareto-front analysis, P₂O₅ could be an optimal material for the reaction with both Li residuals. Finally, the reactivity of the coating materials containing 3d/4d transition metal elements is better than that of materials containing other types of elements