Biocidal activity of cellulose materials for medical implants

Photo-crosslinked chitosan-gelatin xerogel-like coating onto "cold" plasma functionalized poly(lactic acid) film as cell culture support

This paper reports on biofunctionalisation of a poly(lactic acid) (PLA) film by surface activation through cold plasma treatment followed by coating with a chitosan-gelatin xerogel. The UV cross-linking of the xerogel precursor was simultaneously performed with the fixation onto the PLA support. This has a strong effect on surface properties, in terms of wettability, surface free energy, morphology and micromechanical features. The hydrophilic - hydrophobic character of the surface, determined by contact angle measurements, was tuned along the process, passing from moderate hydrophobic PLA to enhanced hydrophilic plasma activated surface, which favors coating adhesion, then to moderate hydrophobic chitosan-gelatin coating. The coating has a Lewis amphoteric surface, with a porous xerogel-like morphology, as revealed by scanning electron microscopy images. By riboflavin mediated UV cross-linking the chitosan-gelatin coating becomes high adhesive and with a more pronounced plasticity, as shown by AFM force-distance spectroscopy. Thus prepared surface-coated PLA supports were successfully tested for growth of dermal fibroblasts, which are known for their induction potential of chondrogenic cells, which is very important in cartilage tissue engineering.

An Overview of the Antimicrobial Properties of Lignocellulosic Materials

Pathogenic microbes are a major source of health and environmental problems, mostly due to their easy proliferation on most surfaces. Currently, new classes of antimicrobial agents are under development to prevent microbial adhesion and biofilm formation. However, they are mostly from synthetic origin and present several disadvantages. The use of natural biopolymers such as cellulose, hemicellulose, and lignin, derived from lignocellulosic materials as antimicrobial agents has a promising potential. Lignocellulosic materials are one of the most abundant natural materials from renewable sources, and they present attractive characteristics, such as low density and biodegradability, are low-cost, high availability, and environmentally friendly. This review aims to provide new insights into the current usage and potential of lignocellulosic materials (biopolymer and fibers) as antimicrobial materials, highlighting their future application as a novel drug-free antimicrobial polymer.

Biocompatible Materials Based on Plasticized Poly(lactic acid), Chitosan and Rosemary Ethanolic Extract I. Effect of Chitosan on the Properties of Plasticized Poly(lactic acid) Materials

The purpose of the present study is to develop new multifunctional environmentally friendly materials having applications both in medical and food packaging fields. New poly(lactic acid) (PLA)-based multifunctional materials containing additives derived from natural resources like chitosan (CS) and rosemary extract (R) were obtained by melt mixing. Each of the selected components has its own specific properties such as: PLA is a biodegradable thermoplastic aliphatic polyester derived from renewable biomass, heat-resistant, with mechanical properties close to those of polystyrene and polyethylene terephthalate, and CS offers good antimicrobial activity and biological functions, while R significantly improves antioxidative action necessary in all applications. A synergy of their combination, an optimum choice of their ratio, and processing parameters led to high performance antimicrobial/antioxidant/biocompatible/environmentally degradable materials. The polyethylene glycol (PEG)-plasticized PLA/chitosan/powdered rosemary extract biocomposites of various compositions were characterized in respect to their mechanical and rheological properties, structure by spectroscopy, antioxidant and antimicrobial activities, and in vitro and in vivo biocompatibility. Scanning electron microscopy images evidence the morphology features added by rosemary powder presence in polymeric materials. Incorporation of additives improved elongation at break, antibacterial and antioxidant activity and also biocompatibility. Migration of bioactive components into D1 simulant is slower for PEG-plasticized PLA containing 6 wt % chitosan and 0.5 wt % rosemary extract (PLA/PEG/6CS/0.5 R) biocomposite and it occurred by a diffusion-controlled mechanism. The biocomposites show high hydrophilicity and good in vitro and in vivo biocompatibility. No hematological, biochemical and immunological modifications are induced by subcutaneous implantation of biocomposites. All characteristics of the PEG-plasticized PLA-based biocomposites recommend them as valuable materials for biomedical implants, and as well as for the design of innovative drug delivery systems. Also, the developed biocomposites could be a potential nature-derived active packaging with controlled release of antimicrobial/antioxidant compounds.

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.

Complex poly(lactic acid)-based biomaterial for urinary catheters: II. Biocompatibility

The present paper is focused on the surface and bulk characterization of poly(lactic acid) (PLA)-based composites that contain hydrolyzed collagen as a biological polymer, silver nanoparticles and vitamin E and epoxidized soybean oil as a plasticizer. The bionanocomposites were obtained by melt processing and evaluated for structural and surface characteristics, biocompatibility, functional properties such as antimicrobial and antioxidant activity and hydrolytic degradation behavior. It has been established that the optimal composition to impart functional properties to the PLA matrix is a formulation containing 15% epoxidized soybean oil, 15% hydrolyzed collagen, 5% Pluronic, 5% vitamin E and 0·3% silver nanoparticles. This bionanocomposite inhibits the growth of both Gram-positive bacteria, Escherichia coli and Salmonella typhimurium, and Gram-negative bacteria, Listeria monocytogenes, and reaches 100% radical-scavenging activity. The PLA-based biomaterials obtained in this study are stable in biological media in the short and medium terms and therefore are recommended as multifunctional biomaterials for the manufacture of medical devices, such as urinary catheters.