High Density Polyethylene Containing Antibacterial Silver Nanoparticles for Medical Applications

Mechanical Performance of 3D-Printed Polyethylene Fibers and Their Durability against Degradation

Polyethylene (PE), one of the most popular thermoplastic polymers, is widely used in various areas, such as materials engineering and biomedical engineering, due to its superior performance, while 3D printing via fused deposition modeling (FDM) provides a facile method of preparing PE products. To optimize the performance and assess the degradation of FDM-printed PE materials, we systematically investigate the influences of printing parameters, such as fiber diameter (stretching) and printer head temperature, and degradation, such as UV exposure and thermal degradation, on the mechanical performance of FDM-printed PE fibers. When FDM-printed PE fibers with a smaller diameter are prepared under a higher collecting speed, they undergo stronger stretching, and thus, show higher tensile strength and Young's modulus values. Meanwhile, the tensile strength and Young's modulus decrease as the printer head temperature increases, due to the lower viscosity, and thus, weaker shearing at high temperatures. However, degradation, such as UV exposure and thermal degradation, cause a decrease in all four mechanical properties, including tensile strength, Young's modulus, tensile strain and toughness. These results will guide the optimization of FDM-printed PE materials and help to assess the durability of PE products against degradation for their practical application.

Biological and Physicochemical Assessment of Middle Ear Prosthesis

Polymers modified with bioactive nanoparticles are a promising solution for patients who need a tissue replacement. Modern implants, thanks to bioactive and bactericidal functions, facilitate the healing and regeneration process of the replaced tissue. The aim of this study was to assess whether silver nanoparticles (AgNPs) could support antibacterial function without cytotoxic effect and deterioration of biostability. This article describes biological and physiochemical aspects concerning a new polymeric middle ear implant (Otoimplant) enriched with silver nanoparticles. This kind of prosthesis is a promising implant for the reconstruction of ossicles in ossiculoplasty. We found that incorporation of silver nanoparticles into a polymeric matrix resulted in bactericidal efficacy against Gram-positive and Gram-negative bacteria, both resistant to antibiotics and basic strains. Our prostheses do not show cytotoxic effect and are a suitable biomaterial platform for effective culture of Saos2 and NHOst osteoblastic cells. The in vitro incubation of the samples in distilled water revealed that surface parameters, such as roughness, may slightly increase as a result of unveiling nanoparticles. However, the prolonged immersion does not change mechanical parameters. During one-year incubation, the prosthesis proved to retain stable values of Young's modulus, tensile strength, propagation of longitudinal ultrasonic waves, pH, and conductivity.

Long-Term Stability of Two Thermoplastic Polymers Modified with Silver Nanoparticles

The aim of this study was to investigate the mechanical properties of polymeric composites prepared via extrusion and injection moulding. Four stable thermoplastic polymers were used as composites matrices (two kinds of polymethyl methacrylate and two kinds of co-polymer acrylonitrile-butadiene-styrene). Silver nanoparticles AgNPs were used as a modifying phase. Mechanical properties of testes materials were determined during the uniaxial stretching. Surface properties such as roughness and contact angle were also evaluated. The materials’ stability was assessed using scanning electron microscopy and non-destructive ultrasonic testing. All measurements were carried out at time intervals, determining both the initial parameters and after 6 and 12 months of incubation in deionized water. The obtained results proved that neither the preparation technology nor the amount of the modifier adversely affect the mechanical properties of the tested composites. The incorporated modifier does not change the surface properties significantly. The studies conducted after the materials’ incubation in water indicate their stability.

Polyethylene/silver-nanofiber composites: A material for antibacterial films

Silver nanofibers (Ag-Nfbs)~80nm in diameter were synthesized by hydrothermal treatment. The nanofibers (3 and 5wt%) were added in the initial feed together with the catalytic system. Polymerizations in an ethylene atmosphere were performed, yielding PE nanocomposites in situ with 3 and 5wt% content of Ag-Nfbs. The antibacterial effect of the silver-nanofiber composites was evaluated after incubation of Escherichia coli ATCC 25923 for 8h on their surface. Bacterial viability tests showed that the silver-nanofiber composites inhibited the growth of Escherichia coli ATCC 25923 by 88 and 56%. This behavior is attributed to increased silver ions release from the nanocomposite. TEM analysis showed that the antibacterial effect is associated with membrane disruption but not with changes in shape.

Relating nanomaterial properties and microbial toxicity

Metal and metal oxide nanoparticles are among the most commonly used nanomaterials and their potential for adversely affecting environmental systems raises concern. Complex microbial consortia underlie environmental processes, and the potential toxicity of nanoparticles to microbial systems, and the consequent impacts on trophic balances, is particularly worrisome. The diverse array of metal and metal oxides, the different sizes and shapes that can be prepared and the variety of possible surface coatings complicate assessments of toxicity. Further muddling biocidal interpretations are the diversity of microbes and their intrinsic tolerances to stresses. Here, we review a range of studies focused on nanoparticle-microbial interactions in an effort to correlate the physical-chemical properties of engineered metal and metal oxide nanoparticles to their biological response. General conclusions regarding the parent material of the nanoparticle and the nanoparticle's size and shape on potential toxicity can be made. However, the surface coating of the material, which can be altered significantly by environmental conditions, can ameliorate or promote microbial toxicity. Understanding nanoparticle transformations and how the nanoparticle surface can be designed to control toxicity represents a key area for further study. Additionally, the vast array of microbial species and the structuring of these species within communities complicate extrapolations of nanoparticle toxicity in real world settings. Ultimately, to interpret the effect and eventual fate of engineered materials in the environment, an understanding of the relationship between nanoparticle properties and responses at the molecular, cellular and community levels will be essential.