Lenka Pazourková

Low-density polyethylene is one of the basic polymers used in medicine for a variety of purposes; so, the relevant improvements in functional properties are discussed here, making it safer to use as devices or implants during surgery or injury. The objective of the laboratory-prepared material was to study the antimicrobial and biocompatible properties of low-density polyethylene composites with 3 wt. % hybrid nanoclay filler. We found that the antimicrobial activity was mainly related to the filler, i.e., the hybrid type, where inorganic clay minerals, vermiculite or montmorillonite, were intercalated with organic chlorhexidine diacetate and subsequently decorated with Ca-deficient hydroxyapatite. After fusion of the hybrid nanofiller with polyethylene, intense exfoliation of the clay layers occurred. This phenomenon was confirmed by the analysis of the X-ray diffraction patterns of the composite, where the original basal peak of the clays decreased or completely disappeared, and the optimal distribution of the filler was observed using the transmission mode of light microscopy. Functional property testing showed that the composites have good antibacterial activity against Staphylococcus aureus, and the biocompatibility prediction demonstrated the formation of Ca- and P-containing particles through an in vitro experiment, thus applicable for medical use.

The aim of this study was to conduct artificial ageing tests on polymer-ceramic composites prepared from polyamide PA-12 polymer matrix for medical applications and three different variants of ceramic fillers: zirconia, alumina and cenospheres. Before ageing, the samples were subjected to ethyl oxide sterilization. The composite variants were prepared for 3D printing using the fused deposition modeling method. The control group consisted of unsterilized samples. Samples were subjected to artificial ageing in a high-pressure autoclave. Ageing conditions were calculated from the modified Hammerlich Arrhenius kinetic equation. Ageing was carried out in artificial saliva. After ageing the composites were subjected to mechanical (tensile strength, hardness, surface roughness) testing, chemical and structural (MS, FTIR) analysis, electron microscopy observations (SEM/EDS) and absorbability measurements.

The alumina and zirconia surfaces were pretreated with chemical etching using alkaline mixtures of ammonia, hydrogen peroxide and sodium hydroxide, and followed with application of the powder layer of Ca-deficient hydroxyapatite (CDH). The influence of etching bath conditions time and concentration on surface development, chemical composition and morphology of medicinal ceramic powders were studied. The following analyses were performed: morphology (scanning electron microscopy), phase composition (X-ray diffraction analysis), changes in binding interactions and chemical composition (FT-Infrared and Energy dispersive spectroscopies). Both types of etchants did not expose the original phase composition changes or newly created phases for both types of ceramics. Subsequent decoration of the surface with hydroxyapatite revealed differences in the morphological appearance of the layer on both ceramic surfaces. The treated zirconia surface accepted CDH as a flowing layer on the surface, while the alumina was decorated with individual CDH aggregates. The goal of this study was to focus further on the ceramic fillers for polymer-ceramic composites used as a biomaterial in dental prosthetics.

Novel biomedical composites, based on organically modified vermiculite and montmorillonite with deposited Ca-deficient hydroxyapatite (CDH), were prepared. The monoionic sodium forms of vermiculite and montmorillonite were intercalated with chlorhexidine diacetate (CA). The surfaces of organoclays were used for the precipitation of Ca-deficient hydroxyapatite. The composites with Ca-deficient hydroxyapatite showed very good antibacterial effects, similar to the antimicrobial activity of pure organoclay samples. Better antibacterial activity was shown in the organically modified montmorillonite sample with Ca-deficient hydroxyapatite compared with the vermiculite composite, but, in the case of Staphylococcus aureus, both composites showed the same minimum inhibitory concentration (MIC) value. The antimicrobial effect of composites against bacteria and fungi increased with the time of exposure. The structural characterization of all the prepared materials, performed using X-ray diffraction and FT infrared spectroscopy analysis, detected no changes in the original clay or CDH during the intercalation or precipitation process, therefore we expect the strength of the compounds to be in the original power.

Clay mineral vermiculite (VT) was modified by organic surfactant hexadecyltrimethylammonium bromide, cerium and aluminum chloride solutions. Prepared materials were used as VT nanofillers to the polyethylene (PE) matrix. The composites of PE with VT nanofillers were prepared by melt compounding technique. Content of organic and inorganic constituents was determined. The X-ray diffraction patterns of VT nanofillers confirmed intercalation of organic and inorganic cations into the VT interlayer space. Antimicrobial activity of powder VT nanofillers and surfaces of PE composite plates was tested on different bacterial strains: 1) Gram-negative, Escherichia coli, 2) Gram-positive, Staphylococcus aureus, and 3) yeast, Candida albicans. The results of antimicrobial test show that powder VT nanofillers inhibited growth of tested bacteria already after 1 h of action. The surfaces of PE composites showed good antibacterial and antifungal effect against Staphylococcus aureus and Candida albicans, respectively.

In this study, the surfaces of montmorillonite (Mt) and vermiculite (Ver) were utilized as substrate for in situ preparation of hydroxyapatite (HAp) nanocomposite. Nanocomposites of clay mineral/HAp were investigated as sorbents of cadmium cations (Cd2+). Two different processes of sorption were compared-(1) dynamic and (2) static (maintaining the solutions containing Cd2+ with sorbents for 24 h in constant conditions). The samples were characterized using atomic absorption spectrometry (AAS) and X-ray powder diffraction (XRD) analysis. The results show that nanocomposites of clay mineral/HAp have higher sorption capacity than pure clays. Comparison of sorption techniques reveals small differences between sorption on Mt clay and its composites.Web of Science1687791778