Hemostatic and Tissue Regeneration Performance of Novel Electrospun Chitosan-Based Materials.

The application of chitosan (Ch) as a promising biopolymer with hemostatic properties and high biocompatibility is limited due to its prolonged degradation time, which, in turn, slows the repair process. In the present research, we aimed to develop new technologies to reduce the biodegradation time of Ch-based materials for hemostatic application. This study was undertaken to assess the biocompatibility and hemostatic and tissue-regeneration performance of Ch-PEO-copolymer prepared by electrospinning technique. Chitosan electrospinning membranes (ChEsM) were made from Ch and polyethylene oxide (PEO) powders for rich high-porous material with sufficient hemostatic parameters. The structure, porosity, density, antibacterial properties, in vitro degradation and biocompatibility of ChEsM were evaluated and compared to the conventional Ch sponge (ChSp). In addition, the hemostatic and bioactive performance of both materials were examined in vivo, using the liver-bleeding model in rats. A penetrating punch biopsy of the left liver lobe was performed to simulate bleeding from a non-compressible irregular wound. Appropriately shaped ChSp or ChEsM were applied to tissue lesions. Electrospinning allows us to produce high-porous membranes with relevant ChSp degradation and swelling properties. Both materials demonstrated high biocompatibility and hemostatic effectiveness in vitro. However, the antibacterial properties of ChEsM were not as good when compared to the ChSp. In vivo studies confirmed superior ChEsM biocompatibility and sufficient hemostatic performance, with tight interplay with host cells and tissues. The in vivo model showed a higher biodegradation rate of ChEsM and advanced liver repair.

A Simple Method to Determine the Fractions of Labile and Mineral-Bound Microelements in Bone Tissue by Atomic Absorption Spectrometry.

In this work a simple and inexpensive method to assess the concentration ratio of the labile and mineral-bound microelements of the bone tissue was developed. The approach is based on the separation of the components of bone tissue by their selective solubility with the subsequent determination of microelements with atomic absorption spectrometry. The total concentrations of Mg, Zn, Fe, Sr, Al, Cu, and Mn and the concentrations of these elements in aqueous solutions with pH 6.5, 10, and 12 after their ultrasonically activated interaction with the powder of dried bone were determined. Two quite different bone samples were analyzed: a cortical fragment of the femur of a mature healthy cow and the spongy part of a human femoral head affected by osteoporosis. Some common and individual features of the both type of bones in regard to the total concentrations and fractional distribution of microelements are discussed. The obtained concentrations of the "soluble" fractions of microelements were critically analyzed taking into account the possible reactions leading to new insoluble phases' formation in alkaline solutions. Based on the data obtained, the ability of elements to form labile fractions in the bone tissue could be arranged in the following descending series: Mg ≥ Zn > Al > Fe > Mn > Cu > Sr.

Biocompatibility and Antibacterial Properties of ZnO-Incorporated Anodic Oxide Coatings on TiZrNb Alloy.

In a present paper, we demonstrate novel approach to form ceramic coatings with incorporated ZnO nanoparticles (NPs) on low modulus TiZrNb alloy with enhanced biocompatibility and antibacterial parameters. Plasma Electrolytic Oxidation (PEO) was used to integrate ZnO nanoparticles (average size 12-27 nm), mixed with Ca(H2PO2)2 aqueous solution into low modulus TiZrNb alloy surface. The TiZrNb alloys with integrated ZnO NPs successfully showed higher surface porosity and contact angle. XPS investigations showed presence of Ca ions and absence of phosphate ions in the PEO modified layer, what explains higher values of contact angle. Cell culture experiment (U2OS type) confirmed that the surface of as formed oxide-ZnO NPs demonstrated hydrophobic properties, what can affect primary cell attachment. Further investigations showed that Ca ions in the PEO coating stimulated proliferative activity of attached cells, resulting in competitive adhesion between cells and bacteria in clinical situation. Thus, high contact angle and integrated ZnO NPs prevent bacterial adhesion and considerably enhance the antibacterial property of TiZrNb alloys. A new anodic oxide coating with ZnO NPs could be successfully used for modification of low modulus alloys to decrease post-implantation complications.

Formation of a Bacteriostatic Surface on ZrNb Alloy via Anodization in a Solution Containing Cu Nanoparticles.

High strength, excellent corrosion resistance, high biocompatibility, osseointegration ability, and low bacteria adhesion are critical properties of metal implants. Additionally, the implant surface plays a critical role as the cell and bacteria host, and the development of a simultaneously antibacterial and biocompatible implant is still a crucial challenge. Copper nanoparticles (CuNPs) could be a promising alternative to silver in antibacterial surface engineering due to low cell toxicity. In our study, we assessed the biocompatibility and antibacterial properties of a PEO (plasma electrolytic oxidation) coating incorporated with CuNPs (Cu nanoparticles). The structural and chemical parameters of the CuNP and PEO coating were studied with TEM/SEM (Transmission Electron Microscopy/Scanning Electron Microscopy), EDX (Energy-Dispersive X-ray Dpectroscopy), and XRD (X-ray Diffraction) methods. Cell toxicity and bacteria adhesion tests were used to prove the surface safety and antibacterial properties. We can conclude that PEO on a ZrNb alloy in Ca-P solution with CuNPs formed a stable ceramic layer incorporated with Cu nanoparticles. The new surface provided better osteoblast adhesion in all time-points compared with the nontreated metal and showed medium grade antibacterial activities. PEO at 450 V provided better antibacterial properties that are recommended for further investigation.

Antibacterial Activity of In Situ Prepared Chitosan/Silver Nanoparticles Solution Against Methicillin-Resistant Strains of Staphylococcus aureus.

BACKGROUND: Investigation of new effective drugs against the methicillin-resistant strains of Staphylococcus aureus (MRSA) is an urgent issue of modern medicine. Antiseptics as an alternative of antibiotics are strong, sustained, and active preparations against resistant strains and do not violate microbiocenosis. MATERIALS AND METHODS: The activity of in situ prepared chitosan-Ag nanoparticles (Ag NPs) solution with different component ratio was tested against MRSA isolated from patients. Ag NPs were synthesized via chemical reduction method using green chemistry approach. In order to improve antimicrobial activity and dispersibility of Ag NPs, surface modification of Ag NPs by cetrimonium bromide (CTAB) was performed. Ag NPs and chitosan-Ag NPs solution were characterized using X-ray diffraction, transmission electron microscopy, infrared spectroscopy, and spectrophotometric measurements. RESULTS AND CONCLUSIONS: The results of XRD, FTIR, UV-Vis, and TEM measurements confirmed the chemical composition of chitosan and Ag NPs and their high purity. Chitosan-AgNPs solutions have shown their superior antimicrobial efficacy compared to its pure forms. At the same time, in situ preparation of chitosan-Ag NPs solution (chitosan powder 6.0 µg/ml, Ag/CTAB NPs) was not possible due to the precipitation of the components. This result is very promising and may be considered as an effective solution in fighting against drug-resistant bacteria.

Dielectric and electric properties of new chitosan-hydroxyapatite materials for biomedical application: Dielectric spectroscopy and corona treatment.

Chitosan-hydroxyapatite composite materials were synthesized and the possibility to make their surface charged by corona discharge treatment has been evaluated. Dielectric and electric properties of the materials were studied by dielectric spectroscopy, including application of equivalent circuits method and computer simulations. Dielectric spectroscopy shows behavior of the materials quite different from that of both chitosan and HA alone. The obtained dielectric permittivity data are of particular interest in predicting the materials' behavior in electrostimulation after implantation. The ε values observed at physiological temperature in the frequency ranges applied are similar to ε data available for bone tissues.

Characterization and in vivo evaluation of chitosan-hydroxyapatite bone scaffolds made by one step coprecipitation method.

Chitosan/hydroxyapatite scaffolds could be used for bone regeneration in case the application of auto- or allografts is impossible. The objective of the present work was to characterize and study in vivo biodegradation of simple chitosan/hydroxyapatite scaffolds. For this purpose, a series of chitosan/hydroxyapatite composites has been synthesized in aqueous medium from chitosan solution and soluble precursor salts by a one step coprecipitation method. A study of in vivo behavior of the materials was then performed using model linear rats. Cylindrical-shaped rods made of the chitosan/hydroxyapatite composite material were implanted into tibial bones of the rats. After 5, 10, 15, and 24 days of implantation, histological and histo-morphometric analyses of decalcified specimens were performed to evaluate the stages of biodegradation processes. Calcified specimens were examined by scanning electron microscopy with X-ray microanalysis to compare elemental composition and morphological characteristics of the implant and the bone during integration. Porous chitosan/hydroxyapatite scaffolds have shown osteoconductive properties and have been replaced in the in vivo experiments by newly formed bone tissue.