Gelatine-coated carbonyl iron particles and their utilization in magnetorheological suspensions

This study demonstrates the formation of biocompatible magnetic particles into organized structures upon the application of an external magnetic field. The capability to create the structures was examined in silicone-oil suspensions and in a gelatine solution, which is commonly used as a blood plasma expander. Firstly, the carbonyl iron particles were successfully coated with gelatine, mixed with a liquid medium in order to form a magnetorheological suspension, and subsequently the possibility of controlling their rheological parameters via a magnetic field was observed using a rotational rheometer with an external magnetic cell. Scanning electron microscopy, infrared spectroscopy, and thermogravimetric analysis confirmed the successful coating process. The prepared magnetorheological suspensions exhibited a transition from pseudoplastic to Bingham behavior, which confirms their capability to create chain-like structures upon application of a magnetic field, which thus prevents the liquid medium from flowing. The observed dynamic yield stresses were calculated using Robertson–Stiff model, which fit the flow curves of the prepared magnetorheological suspensions well. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Ministry of Education, Youth and Sports of the Czech Republic-DKRVO [RP/CPS/2020/003]RP/CPS/2020/003; Ministerstvo Školství, Mládeže a Tělovýchovy, MŠM

Thermal stability of bacteriocin nisin in polylactide-based films

This work investigates the thermal stability of bacteriocin nisin in polylactide (PLA) and polylactide/polyethylene glycol (PLA/PEG) blends at temperatures of 90 °C–180 °C. The samples were prepared by solvent cast technique and characterized according to their mechanical and thermal properties. Research on the thermal stability of nisin in the PLA and PLA/PEG systems was carried out by exposing the given films to various temperatures (90 °C, 120 °C, 160 °C, and 180 °C) for a duration of up to 48 h. Assessment of the antibacterial activity of the samples was carried out by the agar diffusion method against Micrococcus luteus, while structural analysis involved the use of high-performance liquid chromatography with mass detection. Structural changes in the polymer matrix were evaluated by gel permeation chromatography and scanning electron microscopy. The results showed that nisin retained almost 70% of its antimicrobial activity in the PLA matrix, even after treatment at 160 °C for 15 min. The presence of PEG significantly enhanced the degradation of nisin above 120 °C. © 2018 The AuthorsMinistry of Agriculture of the Czech Republic [QJ1310254]; Ministry of Education, Youth and Sports of the Czech Republic [LO1504]; Internal Grant Agency of Tomas Bata University in Zlin [IGA/CPS/2018/003

Antimicrobial modification of polypropylene with silver nanoparticles immobilized on zinc stearate

The microwave synthesis of Ag nanoparticles on zinc stearate (ZnSt/Ag) was performed to obtain an antimicrobial additive for a polypropylene matrix. Thermoplastically prepared polymer composites contained (1, 3, 5 and 10) % of mass fractions of ZnSt/Ag. The effect of the presence of additives on the morphology and mechanical properties of composites was studied by scanning electron microscopy and stress-strain analysis. The antimicrobial activity of the composites was studied according to the ISO 22196 standard. The results showed that sufficient antimicrobial activity of the composites against both Gram-positive and Gram-negative bacterial strains was observed in the case of the composites with the highest filling studied.grant of Technology Agency of the Czech Republic [TE02000006]; Ministry of Education, Youth and Sports of the Czech Republic - Program NPU I [LO1504]; Internal Grant Agency of the Tomas Bata University in Zlin [IGA/CPS/2015/004

Synthesis and effect of hierarchically structured Ag-ZnO hybrid on the surface antibacterial activity of a propylene-based elastomer blends

In this study, a hybrid Ag-ZnO nanostructured micro-filler was synthesized by the drop technique for used in plastic and medical industry. Furthermore, new antibacterial polymer nanocomposites comprising particles of Ag-ZnO up to 5 wt % and a blend of a thermoplastic polyolefin elastomer (TPO) with polypropylene were prepared using twin screw micro-compounder. The morphology and crystalline-phase structure of the hybrid Ag-ZnO nanostructured microparticles obtained was characterized by scanning electron microscopy and powder X-ray diffractometry. The specific surface area of this filler was investigated by means of nitrogen sorption via the Brunauer-Emmet-Teller method. A scanning electron microscope was used to conduct a morphological study of the polymer nanocomposites. Mechanical and electrical testing showed no adverse effects on the function of the polymer nanocomposites either due to the filler utilized or the given processing conditions, in comparison with the neat polymer matrix. The surface antibacterial activity of the compounded polymer nanocomposites was assessed against Escherichia coli ATCC 8739 and Staphylococcus aureus ATCC 6538P, according to ISO 22196:2007 (E). All the materials at virtually every filler-loading level were seen to be efficient against both species of bacteria. © 2018 by the authors.Ministry of Education, Youth and Sports of the Czech Republic-Program NPU I [LO1504]; European Regional Development Fund (ERDF); national budget of the Czech Republic [CZ.1.05/2.1.00/19.0409]; TBU in Zlin [IGA/CPS/2017/007

Isolation and thermal stabilization of bacteriocin nisin derived from whey for antimicrobial modifications of polymers

This work describes novel alternative for extraction of bacteriocin nisin from a whey fermentation media and its stabilization by using polyethylene glycol as matrix with high practical applicability. This product was compared with commercially available nisin product stabilized by sodium chloride and nisin extracted and stabilized by using ammonium sulfate and polysorbate 80. The stability of samples was tested by means of long-term storage at -18, 4, 25, and 55 degrees C up to 165 days. The nisin content in the samples was determined by high-performance liquid chromatography and electrophoresis. In addition, effect of whey fortification with lactose on nisin production and antibacterial activity studied against Staphylococcus aureus was tested. Results show that stabilization by polyethylene glycol provides enhanced nisin activity at 55 degrees C after 14 days and long-term stability at 25 degrees C with keeping antibacterial activity.Ministry of Agriculture of the Czech Republic [QJ1310254]; Ministry of Education, Youth and Sports of the Czech Republic [LO1504]; Internal Grant Agency of Tomas Bata University in Zlin [IGA/CPS/2017/005]QJ1310254, MZe, Ministerstvo Zemědělství; LO1504, MEYS, Ministry of Education, Youth and Science; IGA/CPS/2017/00

Immobilization of bacteriocin nisin into a poly(vinyl alcohol) polymer matrix crosslinked with nontoxic dicarboxylic acid

This work is focused on novel methodology of poly(vinyl alcohol) crosslinking by non-toxic dicarboxylic acid, glutaric acid. The cross-linked system was used as a matrix for immobilization of bacteriocin nisin. Effect of the crosslinking degree on physico-chemical, morphology, mechanical, and thermal properties of poly(vinyl alcohol) films were investigated by using swelling test, Fourier transform infrared spectroscopy, scanning electron microscopy, stress-strain analysis, differential scanning calorimetry, and thermogravimetry. Release profile of the nisin from the cross-linked poly(vinyl alcohol) was studied by high performance liquid chromatography. Antibacterial activity of the prepared systems was tested by agar diffusion test and dilution and spread plate technique. Results showed suitability of glutaric acid as effective crosslinking agent of poly(vinyl alcohol) that acts synergistically with bacteriocin nisin against the tested Gram-positive and Gram-negative bacterial strains. © 2016 Wiley Periodicals, Inc.LO1504, NPU, Northwestern Polytechnical UniversityMinistry of Agriculture of the Czech Republic [QJ1310254]; Ministry of Education, Youth and Sports of the Czech Republic within the NPU I program [LO1504]; European Regional Development Fund [CZ.1.05/2.1.00/19.0409]; Internal Grant Agency of the Tomas Bata University on Zlin [IGA/CPS/2016/004

Core–shell PLA–PVA porous microparticles as carriers for bacteriocin nisin

This work is focused on preparation of novel porous type of core–shell-structured microparticles based on polylactide (shell) and poly(vinyl alcohol) cross-linked with glutaric acid (GA) (core) prepared by water-in-oil-in-water solvent evaporation technique. The microparticle systems were used as delivery systems for immobilisation of model antibacterial agent–nisin. The effect of cross-linking and the initial amount of nisin on their morphology was investigated using scanning electron microscopy, BET analysis, zeta potential measurement and Fourier transform infra-red spectroscopy. Encapsulation efficiency and release profile of nisin from the microparticles were studied by high performance liquid chromatography. Antibacterial activity of the prepared systems was tested by dilution and spread plate technique. Results showed the microparticles in the size range of 9–16 μm in diameter with spherical multi-hollow core–shell structure. The presence of cross-linking agent GA influences the release profile of the peptide and has synergistic effect on Listeria monocytogenes growth reduction. © 2017 Informa UK Limited, trading as Taylor & Francis Group.CZ.1.05/2.1.00/19.0409, MŠMT, Ministerstvo Školství, Mládeže a Tělovýchovy; LO1504, MŠMT, Ministerstvo Školství, Mládeže a TělovýchovyMinistry of Agriculture of the Czech Republic [QJ1310254]; Ministry of Education, Youth and Sports of the Czech Republic [LO1504, CZ.1.05/2.1.00/19.0409]; Internal Grant Agency of the Tomas Bata University in Zlin [IGA/CPS/2017/005

Transformation of cellulose via two-step carbonization to conducting carbonaceous particles and their outstanding electrorheological performance

In this study, cellulose was carbonized in two-steps using hydrothermal and thermal carbonization in sequence, leading to a novel carbonaceous material prepared from a renewable source using a sustainable method without any chemicals and, moreover, giving high yields after a treatment at 600 degrees C in an inert atmosphere. During this treatment, cellulose was transformed to uniform microspheres with increased specific surface area and, more importantly, conductivity increased by about 7 orders of magnitude. The successful transition of cellulose to conducting carbonaceous microspheres was confirmed through SEM, FTIR, X-ray diffraction and Raman spectroscopy. Prepared samples were further used as a dispersed phase in electrorheological fluids, exhibiting outstanding electrorheological effects with yield stress over 100 Pa at an electric field strength 1.5 kV mm(-1) and a particle concentration of only 5 wt%, significantly overcoming recent state-of-the-art findings. Impedance spectroscopy analysis showed clear interfacial polarization of this ER fluid with high dielectric relaxation strength and short relaxation time, which corresponded to increased conductivity of the particles when compared to pure cellulose. These novel carbonaceous particles prepared from renewable cellulose have further potential to be utilized in many other applications that demand conducting carbonaceous structures with high specific surface area (adsorption, catalyst, filtration, energy storage).RP/CPS/2022/003; Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMTMinistry of Education, Youth and Sports of the Czech Republic-DKRVO [RP/CPS/2022/003

Anti-hydrolysis effect of aromatic carbodiimide in poly(lactic acid)/wood flour composites

Poly(lactic acid) (PLA) filled with wood flour (WF) is more susceptible to hydrolysis compared to pure PLA. This work shows that the hydrolysis reactions leading to chain scission can be hindered by using 2 wt% of bis(2,6-diisopropylphenyl)carbodiimide (ZIKA). It was found that the addition of ZIKA supports the crosslinking of PLA/WF composite. The crosslinking slightly hindered the annealing efficiency of wood flour and increased the stiffness of biocomposites. The thermal stability of biocomposites containing ZIKA was slightly improved. The relevance of the antihydrolysis effect of ZIKA during melt processing of biocomposites was correlated with the rheological and molar mass properties. The hydrolytic stability of biocomposites was determined under buffer solution conditions at accelerated temperature 80 °C and pH of 7. The determined lower depolymerisation and hydrolysis rates of PLA/WF-ZIKA composites indicate that the service lifespan of biocomposites can be prolonged by the addition of ZIKA additive. © 2017 Elsevier LtdERDF, European Regional Development Fund; ERDF, European Regional Development Fund; 17-16928Y, GACR, Grantová Agentura České Republiky; LO1211, MŠMT, Ministerstvo Školství, Mládeže a Tělovýchovy; LO1504, MŠMT, Ministerstvo Školství, Mládeže a TělovýchovyEuropean Regional Development Fund (EFRE); province of Upper Austria through program IWB - Upper Austria [project BioRest]; Ministry of Education, Youth and Sport of the Czech Republic (MEYS) through the project "Materials Research Centre - Sustain ability and Development" [LO1211]; Czech Science Foundation (GACR) [17-16928Y]; Ministry of Education, Youth and Sports of the Czech Republic (MEYS) [LO1504]; Research & Development Operational Programme – ERD