scholarly journals Influence of the Chitosan and Rosemary Extract on Fungal Biodegradation of Some Plasticized PLA-Based Materials

Polymers ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 469
Author(s):  
Elena Stoleru ◽  
Cornelia Vasile ◽  
Lăcramioara Oprică ◽  
Onur Yilmaz
Keyword(s):  
Thermal Properties ◽  
Bioactive Compounds ◽  
Structural Changes ◽  
Degradation Products ◽  
Chaetomium Globosum ◽  
Poly Lactic Acid ◽  
Rosemary Extract ◽  
Alcoholic Extract ◽  
Fungal Degradation ◽  
Polymeric Samples

The fungal degradation of the complex polymeric systems based on poly(lactic acid) (PLA) and natural bioactive compounds (chitosan and powdered rosemary alcoholic extract) was studied. Two fungal strains, Chaetomium globosum and Phanerochaete chrysosporium were tested. Both fungi characteristics and changes in morphology, structure and thermal properties were monitored. Biochemical parameters as superoxide dismutase, catalase, soluble protein and malondialdehyde have been determined at different time periods of fungal degradation. The fungi extracellular enzyme activities are slightly decreased in the case of composites containing bioactive compounds. The presence of natural compounds in the PLA-based polymeric system determines an acceleration of fungal degradation and probably the chemical hydrolysis, which further helps the attachment of fungi on the surface of polymeric samples. Significant decreases in average molecular mass of the polymeric samples were observed by fungi action; accompanied by structural changes, increase in crystallinity and decrease of thermal properties and the loss of the physical integrity and finally to degradation and integration of fungal degradation products into environmental medium. It was found that both fungi tested are efficient for PLA-based materials degradation, the most active from them being Chaetomium globosum fungus.

Structural Studies of Fibrinolysis by Electron and Light Microscopy

1999 ◽  
Vol 82 (08) ◽  
pp. 277-282 ◽  
Author(s):  
Yuri Veklich ◽  
Jean-Philippe Collet ◽  
Charles Francis ◽  
John W. Weisel
Keyword(s):  
Electron Microscopy ◽  
Light Microscopy ◽  
Plasminogen Activator ◽  
Structural Changes ◽  
Molecular Mechanisms ◽  
Degradation Products ◽  
Molecular Model ◽  
Three Dimensional ◽  
Tissue Type ◽  
Type Plasminogen Activator

IntroductionMuch is known about the fibrinolytic system that converts fibrin-bound plasminogen to the active protease, plasmin, using plasminogen activators, such as tissue-type plasminogen activator (t-PA) and urokinase-type plasminogen activator. Plasmin then cleaves fibrin at specific sites and generates soluble fragments, many of which have been characterized, providing the basis for a molecular model of the polypeptide chain degradation.1-3 Soluble degradation products of fibrin have also been characterized by transmission electron microscopy, yielding a model for their structure.4 Moreover, high resolution, three-dimensional structures of certain fibrinogen fragments has provided a wealth of information that may be useful in understanding how various proteins bind to fibrin and the overall process of fibrinolysis (Doolittle, this volume).5,6 Both the rate of fibrinolysis and the structures of soluble derivatives are determined in part by the fibrin network structure itself. Furthermore, the activation of plasminogen by t-PA is accelerated by the conversion of fibrinogen to fibrin, and this reaction is also affected by the structure of the fibrin. For example, clots made of thin fibers have a decreased rate of conversion of plasminogen to plasmin by t-PA, and they generally are lysed more slowly than clots composed of thick fibers.7-9 Under other conditions, however, clots made of thin fibers may be lysed more rapidly.10 In addition, fibrin clots composed of abnormally thin fibers formed from certain dysfibrinogens display decreased plasminogen binding and a lower rate of fibrinolysis.11-13 Therefore, our increasing knowledge of various dysfibrinogenemias will aid our understanding of mechanisms of fibrinolysis (Matsuda, this volume).14,15 To account for these diverse observations and more fully understand the molecular basis of fibrinolysis, more knowledge of the physical changes in the fibrin matrix that precede solubilization is required. In this report, we summarize recent experiments utilizing transmission and scanning electron microscopy and confocal light microscopy to provide information about the structural changes occurring in polymerized fibrin during fibrinolysis. Many of the results of these experiments were unexpected and suggest some aspects of potential molecular mechanisms of fibrinolysis, which will also be described here.

scholarly journals An Insight into Kiwiberry Leaf Valorization: Phenolic Composition, Bioactivity and Health Benefits

Molecules ◽  
2021 ◽  
Vol 26 (8) ◽  
pp. 2314
Author(s):  
Ana Margarida Silva ◽  
Diana Pinto ◽  
Iva Fernandes ◽  
Victor de Freitas ◽  
María de la Luz Cádiz-Gurrea ◽  
...  
Keyword(s):  
Bioactive Compounds ◽  
Plant Material ◽  
Dry Weight ◽  
Alcoholic Extract ◽  
Phenolic Profile ◽  
Hydroalcoholic Extract ◽  
Caffeoylquinic Acids ◽  
Solar Exposure ◽  
Assisted Extraction ◽  
Phenolic And Flavonoid

During kiwiberry production, different by-products are generated, including leaves that are removed to increase the fruit’s solar exposure. The aim of this work was to extract bioactive compounds from kiwiberry leaf by employing microwave-assisted extraction (MAE). Compatible food solvents (water and ethanol) were employed. The alcoholic extract contained the highest phenolic and flavonoid contents (629.48 mg of gallic acid equivalents (GAE) per gram of plant material on dry weight (dw) (GAE/g dw) and 136.81 mg of catechin equivalents per gram of plant material on dw (CAE/g dw), respectively). Oppositely, the hydroalcoholic extract achieved the highest antioxidant activity and scavenging activity against reactive oxygen and nitrogen species (IC50 = 29.10 μg/mL for O2•−, IC50 = 1.87 μg/mL for HOCl and IC50 = 1.18 μg/mL for •NO). The phenolic profile showed the presence of caffeoylquinic acids, proanthocyanidin, and quercetin in all samples. However, caffeoylquinic acids and quercetin were detected in higher amounts in the alcoholic extract, while proanthocyanidins were prevalent in the hydroalcoholic extract. No adverse effects were observed on Caco-2 viability, while the highest concentration (1000 µg/mL) of hydroalcoholic and alcoholic extracts conducted to a decrease of HT29-MTX viability. These results highlight the MAE potentialities to extract bioactive compounds from kiwiberry leaf.

scholarly journals Reaction Mechanism and Mechanical Property Improvement of Poly(Lactic Acid) Reactive Blending with Epoxy Resin

Polymers ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2429
Author(s):  
Krittameth Kiatiporntipthak ◽  
Nanthicha Thajai ◽  
Thidarat Kanthiya ◽  
Pornchai Rachtanapun ◽  
Noppol Leksawasdi ◽  
...  
Keyword(s):  
Thermal Properties ◽  
Epoxy Resin ◽  
Softening Temperature ◽  
Poly Lactic Acid ◽  
Mechanical And Thermal Properties ◽  
Nanoparticle Dispersion ◽  
Reactive Blending ◽  
Partial Miscibility ◽  
Epoxy Blends ◽  
Epoxy Content

Polylactic acid (PLA) was melt-blended with epoxy resin to study the effects of the reaction on the mechanical and thermal properties of the PLA. The addition of 0.5% (wt/wt) epoxy to PLA increased the maximum tensile strength of PLA (57.5 MPa) to 67 MPa, whereas the 20% epoxy improved the elongation at break to 12%, due to crosslinking caused by the epoxy reaction. The morphology of the PLA/epoxy blends showed epoxy nanoparticle dispersion in the PLA matrix that presented a smooth fracture surface with a high epoxy content. The glass transition temperature of PLA decreased with an increasing epoxy content owing to the partial miscibility between PLA and the epoxy resin. The Vicat softening temperature of the PLA was 59 °C and increased to 64.6 °C for 0.5% epoxy. NMR confirmed the reaction between the -COOH groups of PLA and the epoxy groups of the epoxy resin. This reaction, and partial miscibility of the PLA/epoxy blend, improved the interfacial crosslinking, morphology, thermal properties, and mechanical properties of the blends.

Structural and thermal properties of the amaranth starch granule obtained by high-impact wet milling

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Diego Fernando Roa Acosta ◽  
José Fernando Solanilla Duque ◽  
Lina Marcela Agudelo Laverde ◽  
Héctor Samuel Villada Castillo ◽  
Marcela Patricia Tolaba
Keyword(s):  
Thermal Properties ◽  
Structural Changes ◽  
Starch Granule ◽  
Amorphous Region ◽  
Extraction Yield ◽  
High Impact ◽  
Degree Of Crystallinity ◽  
Wet Milling ◽  
Starch Structure ◽  
Structure Changes

AbstractIn this study, amaranth starch was extracted by high-impact wet milling and its structural and thermal properties and the effect of NaOH and SDS concentrations on extraction yield were evaluated. The best condition was 55 g of starch/100 g of amaranth, with a decrease from 2.5 to 3.5 kJ/g using different milling energies. The decrease in the protein content of the starch granule is due to an effect of the interaction between surfactant and alkali, preventing the destruction of granules. All starches presented a degree of crystallinity between 21 and 28%. The internal structural changes of the starch granule were monitored by attenuated total reflectance - Fourier-transform infrared (ATR-FTIR) in the region of 990 to 1060 cm−1. Spectra showed significant differences between the peaks at 1032 and 1005 cm−1, corresponding to the crystalline/amorphous region of the starch structure. Changes in viscosity profiles were observed between 0.302 and 1.163 Pa s.

Morphological Structure and Thermal Property of PLA/PCL Nanofiber by Electrospinning

2014 ◽  
Vol 1048 ◽  
pp. 418-422 ◽  
Author(s):  
Rui Tian Zhu ◽  
Ming Hao Tan ◽  
Peng Zhang ◽  
Liang Zhang ◽  
Xiao Ming Chen ◽  
...  
Keyword(s):  
Thermal Properties ◽  
Medical Equipment ◽  
Morphological Structure ◽  
Diameter Distribution ◽  
Poly Lactic Acid ◽  
Adhesive Film ◽  
Mean Diameter ◽  
Blend Fiber ◽  
Biomedical Field ◽  
Poly Caprolactone

Poly (lactic) acid (PLA)/poly (caprolactone) (PCL) blends nanofibers, with mean diameter about 600nm, were prepared by electrospinning. This research focused on the morphological and thermal properties of nanofibers made from PLA/PCL bends with different PCL content. The results showed that the addition of PCL could improve the morphology of the nanofibers. The film with blend fiber at PLA/PCL ratio of 80:20 is characterized with the smoothest surface and the highest orientation. The diameter distribution of blend fibers is wider than that of pure PLA. The glass-transition temperature of PLA for blend fiber is higher than that of pure PLA, and their melting temperature is lower than that of pure PLA. It can be used in biomedical field for degradable membrane, anti-adhesive film and medical equipment.

Influence of extrusion screw speed on the properties of halloysite nanotube impregnated polylactic acid nanocomposites

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Chaitra Venkatesh ◽  
Yuanyuan Chen ◽  
Zhi Cao ◽  
Shane Brennan ◽  
Ian Major ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Lactic Acid ◽  
Thermal Properties ◽  
Composite Films ◽  
Polymer Melt ◽  
Poly Lactic Acid ◽  
Mechanical And Thermal Properties ◽  
Screw Speed ◽  
Halloysite Nanotube ◽  
The Past

Abstract Poly (lactic acid)/halloysite nanotube (PLA/HNT) nanocomposites have been studied extensively over the past few years owing to the interesting properties of the polymer, PLA, and the nanoclay, HNT, individually and as composites. In this paper, the influence of the screw speed during extrusion was investigated and was found to have a significant impact on the mechanical and thermal performance of the extruded PLA/HNT nanocomposites. To determine the effect of screw speed on PLA/HNT nanocomposites, 5 and 10 wt% of HNTs were blended into the PLA matrix through compounding at screw speeds of 40, 80, and 140 rpm. Virgin PLA was compounded for comparison. The resultant polymer melt was quench cooled onto a calendar system to produce composite films which were assessed for mechanical, thermal, chemical, and surface properties. Results illustrate that in comparison to 40 and 80 rpm, the virgin PLA when compounded at 140 rpm, indicated a significant increase in the mechanical properties. The PLA/HNT 5 wt% nanocomposite compounded at 140 rpm showed significant improvement in the dispersion of HNTs in the PLA matrix which in turn enhanced the mechanical and thermal properties. This can be attributed to the increased melt shear at higher screw speeds.

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