Effect of Gamma Irradiation on the PLA-Based Blends and Biocomposites Containing Rosemary Ethanolic Extract and Chitosan

The irradiation of polymeric materials with ionizing radiation (γ-rays, X-rays, accelerated electrons, ion beams, etc.) may lead to disproportion, hydrogen abstraction, arrangements, degradation, and/or the formation of new bonds. The purpose of this paper is to evaluate the effect of gamma irradiation on some new poly(lactic acid) (PLA)-based blends and biocomposites, which is crucial when they are used for food packaging or medical purposes. The polymeric blends and biocomposites based on PLA and rosemary ethanolic extract (R) and poly(ethylene glycol) (PEG) (20 wt%) plasticized PLA, chitosan (CS) (3–6 wt%) and R (0.5 wt%) biocomposites were subjected to gamma irradiation treatment using three low γ-doses of 10, 20, and 30 kGy. The effect of irradiation was evaluated by Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), thermogravimetry (TG), chemiluminescence method (CL), migration studies, and antibacterial activity tests. It was found that in comparison with neat PLA, the gamma irradiation in the oxidative conditions of the PLA-based blends and biocomposites, causes modifications in the structure, morphology, and thermal properties of the materials depending on irradiation dose and the presence of natural additives such as rosemary and chitosan. It was established that under a gamma-irradiation treatment with dose of 10–20 kGy, the PLA materials showed minor changes in structure and properties being suitable for application in packaging and in addition after irradiation with such doses their antimicrobial activity against Escherichia coli, Staphylococcus aureus, and Salmonella typhimurium is improved.

Evaluation of the Rosemary Extract Effect on the Properties of Polylactic Acid-Based Materials

New multifunctional materials containing additives derived from natural resources as powdered rosemary ethanolic extract were obtained by melt mixing and processed in good conditions without degradation and loss of additives. Incorporation of powdered rosemary ethanolic extract (R) into poly(lactic acid) (PLA) improved elongation at break, rheological properties, antibacterial and antioxidant activities, in addition to the biocompatibility. The good accordance between results of the chemiluminescence method and radical scavenging activity determination by chemical method evidenced the increased thermoxidative stability of the PLA biocomposites with respect to neat PLA, with R acting as an antioxidant. PLA/R biocomposites also showed low permeability to gases and migration rates of the bioactive compounds and could be considered as high-performance materials for food packaging. In vitro biocompatibility based on the determination of surface properties demonstrated a good hydrophilicity, better spreading and division of fibroblasts, and increased platelet cohesion. The implantation of PLA/R pellets, was proven to possess a good in vivo biocompatibility, and resulted in similar changes in blood parameters and biochemical responses with the control group, suggesting that these PLA-based materials demonstrate very desirable properties as potential biomaterials, useful in human medicine for tissue engineering, wound management, orthopedic devices, scaffolds, drug delivery systems, etc. Therefore, PLA/R-based materials show promising properties for applications both in food packaging and as bioactive biomaterials.

Poly(vinyl alcohol)/chitosan/montmorillonite nanocomposites for food packaging applications

Poly(vinyl alcohol) (PVA)/chitosan (CS)/montmorillonite (C30B) materials for food packaging applications were prepared by using a noninvasive and low-cost freeze/thawing method. Cloisite 30B nanoclay content in PVA/CS gels was varied in order to establish optimum amount to obtain improved properties. The structural, morphological, rheological aspects, thermal stability, and antimicrobial activity were investigated using various techniques as Fourier transform infrared, scanning electron microscopy, rheology, thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical thermal analysis, and antibacterial tests. It was noticed that the obtained materials show an intercalated structure with specific interactions between components and nanoclay incorporation led to an increased thermal stability, mechanical properties, and excellent antimicrobial activity against Escherichia coli, Listeria monocytogenes, and Salmonella typhimurium due to synergistic action of CS and nanoclay.

Polyurethane–extracellular matrix/silver bionanocomposites for urinary catheters

Polyurethane–extracellular matrix membranes with bionanocomposites or coatings containing a small amount of biocompatible polymers such as hydrolyzed collagen, elastin, hyaluronic acid or chondroitin sulfate, and silver were obtained by solvent casting or electrospinning/electrospraying of the polyurethane–extracellular matrix–Ag formulations onto pure polyurethane membrane in order to achieve improved antibacterial biomaterials for urinary catheters. Using Fourier transform infrared spectroscopy, the interaction of the incorporated silver nanoparticles with polyurethane–extracellular matrix was found, while X-ray photoelectron spectroscopy and X-ray diffraction analyses ws used to determine the presence of metallic Ag for polyurethane membrane and Ag only in oxidized state for polyurethane–extracellular matrix membranes due to the stabilizing effect of polymeric components. The in vitro antimicrobial tests against Escherichia coli, Salmonella typhymurium, and Listeria monocytogenes were used for the evaluation of the antimicrobial efficiency.