Ivana Kopova

Newly developed Ti-Nb-Zr-Ta-Si-Fe biomedical beta titanium alloys with increased strength and enhanced biocompatibility.

Beta titanium alloys are promising materials for load-bearing orthopaedic implants due to their excellent corrosion resistance and biocompatibility, low elastic modulus and moderate strength. Metastable beta-Ti alloys can be hardened via precipitation of the alpha phase; however, this has an adverse effect on the elastic modulus. Small amounts of Fe (0-2 wt.%) and Si (0-1 wt.%) were added to Ti-35Nb-7Zr-6Ta (TNZT) biocompatible alloy to increase its strength in beta solution treated condition. Fe and Si additions were shown to cause a significant increase in tensile strength and also in the elastic modulus (from 65 GPa to 85 GPa). However, the elastic modulus of TNZT alloy with Fe and Si additions is still much lower than that of widely used Ti-6Al-4V alloy (115 GPa), and thus closer to that of the bone (10-30 GPa). Si decreases the elongation to failure, whereas Fe increases the uniform elongation thanks to increased work hardening. Primary human osteoblasts cultivated for 21 days on TNZT with 0.5Si+2Fe (wt.%) reached a significantly higher cell population density and significantly higher collagen I production than cells cultured on the standard Ti-6Al-4V alloy. In conclusion, the Ti-35Nb-7Zr-6Ta-2Fe-0.5Si alloy proves to be the best combination of elastic modulus, strength and also biological properties, which makes it a viable candidate for use in load-bearing implants.

Growth and Potential Damage of Human Bone-Derived Cells on Fresh and Aged Fullerene C60 Films

Fullerenes are nanoparticles composed of carbon atoms arranged in a spherical hollow cage-like structure. Numerous studies have evaluated the therapeutic potential of fullerene derivates against oxidative stress-associated conditions, including the prevention or treatment of arthritis. On the other hand, fullerenes are not only able to quench, but also to generate harmful reactive oxygen species. The reactivity of fullerenes may change in time due to the oxidation and polymerization of fullerenes in an air atmosphere. In this study, we therefore tested the dependence between the age of fullerene films (from one week to one year) and the proliferation, viability and metabolic activity of human osteosarcoma cells (lines MG-63 and U-2 OS). We also monitored potential membrane and DNA damage and morphological changes of the cells. After seven days of cultivation, we did not observe any cytotoxic morphological changes, such as enlarged cells or cytosolic vacuole formation. Furthermore, there was no increased level of DNA damage. The increasing age of the fullerene films did not cause enhancement of cytotoxicity. On the contrary, it resulted in an improvement in the properties of these materials, which are more suitable for cell cultivation. Therefore, fullerene films could be considered as a promising material with potential use as a bioactive coating of cell carriers for bone tissue engineering.

Growth and Potential Damage of Human Bone-Derived Cells Cultured on Fresh and Aged C60/Ti Films

Thin films of binary C60/Ti composites, with various concentrations of Ti ranging from ~ 25% to ~ 70%, were deposited on microscopic glass coverslips and were tested for their potential use in bone tissue engineering as substrates for the adhesion and growth of bone cells. The novelty of this approach lies in the combination of Ti atoms (i.e., widely used biocompatible material for the construction of stomatological and orthopedic implants) with atoms of fullerene C60, which can act as very efficient radical scavengers. However, fullerenes and their derivatives are able to generate harmful reactive oxygen species and to have cytotoxic effects. In order to stabilize C60 molecules and to prevent their possible cytotoxic effects, deposition in the compact form of Ti/C60 composites (with various Ti concentrations) was chosen. The reactivity of C60/Ti composites may change in time due to the physicochemical changes of molecules in an air atmosphere. In this study, we therefore tested the dependence between the age of C60/Ti films (from one week to one year) and the adhesion, morphology, proliferation, viability, metabolic activity and potential DNA damage to human osteosarcoma cells (lines MG-63 and U-2 OS). After 7 days of cultivation, we did not observe any negative influence of fresh or aged C60/Ti layers on cell behavior, including the DNA damage response. The presence of Ti atoms resulted in improved properties of the C60 layers, which became more suitable for cell cultivation.

Hydrogen-Terminated Diamond Sensors for Electrical Monitoring of Cells

In this paper we introduce fully optically transparent impedance biosensors based on intrinsic nanocrystalline diamond (NCD) films deposited on glass substrate. Prepared sensors have an interdigital electrode (IDE) structures realized by local hydrogen and oxygen termination of diamond surface, which mean in-plane configuration of active sensor area. Sensors were tested by real time monitoring of human osteoblast-like MG 63 cells in wide frequency range from 10 Hz to 100 kHz for several days. Two different measurement setups were used and compared regarding to their advantages and disadvantages. Proof of concept of diamond-based impedance sensor is showed, i.e. time dependence and frequency dependence (Nyquist plots) of absolute impedance.

Nanostructured materials as substrates for the adhesion, growth, and osteogenic differentiation of bone cells

Abstract Nanostructured materials, that is, planar materials with nanoscale surface roughness or three-dimensional nanostructured scaffolds (e.g., nanofibrous scaffolds or scaffolds with pores decorated with nanoparticles) are considered as excellent substrates for tissue engineering, because they mimic the nanoarchitecture of the natural extracellular matrix. On nanostructured substrates, the cell adhesion-mediating molecules, such as fibronectin, vitronectin, or collagen, are adsorbed in an appropriate geometrical conformation, which allows good accessibility of specific sites in these molecules (e.g., RGD-containing oligopeptides) for cell adhesion receptors. In addition, the nanostructured materials preferentially adsorb vitronectin, which is recognized with osteoblasts through the KRSR amino acid sequence. Thus, nanostructured substrates are particularly important for bone tissue engineering. On planar substrates, the surface nanoroughness can be created by various subtractive technologies, such as chemical etching, plasma treatment, sandblasting, shot peening, grinding, polishing, or additive technologies, such as deposition of various nanostructured films, based on ceramics, carbon nanoparticles, polymers, or metals. For construction of nanostructured 3D substrates, the nanoparticles can be admixed into the polymeric matrix or deposited on the inner structure of 3D scaffolds. These nanoparticles then reinforce the scaffolds and create additional nanostructure on the pore walls or fibers within the scaffolds, making these scaffolds stronger, more bioactive, and thus more suitable for bone tissue engineering. In our earlier studies and studies by other authors, all mentioned planar and 3D substrates proved to be suitable cell carriers for bone tissue engineering and construction of bone implants.