V Safonov

The surface parameters modifications at nano scale for biomedical applications

Functional coatings deposition is an effective way of surface modification with direct control of stoichiometry, impurity elements, functional groups and surface charges. Modified surface properties such as composition, roughness, wettability have effect on the most important processes at biomaterial interface. The aim of present study was the analysis of surface roughness and surface free energy parameters of oxide Al2O3 and Ta2O5 coatings and the possibility to separate the influence of such factors on the regularities and mechanisms of nano materials interactions with the biological objects.

Formation of Solution-derived Hydroxyapatite Coatings on Titanium Alloy in the Presence of Magnetron-sputtered Alumina Bond Coats.

Hydroxyapatite Ca10(PO4)6(OH)2 (HAp) and calcium phosphate ceramic materials and coatings are widely used in medicine and dentistry because of their ability to enhance the tissue response to implant surfaces and promote bone ingrowth and osseoconduction processes. The deposition conditions have a great influence on the structure and biofunctionality of calcium phosphate coatings. Corrosion processes and poor adhesion to substrate material reduce the lifetime of implants with calcium phosphate coatings. The research has focused on the development of advanced methods to deposit double-layered ceramic oxide/calcium phosphate coatings by a hybrid technique of magnetron sputtering and thermal methods. The thermal method can promote the crystallization and the formation of HAp coatings on titanium alloy Ti6Al4V substrates at low temperature, based on the principle that the solubility of HAp in aqueous solutions decreases with increasing substrate temperature. By this method, hydroxyapatite directly coated the substrate without precipitation in the initial solution. Using a thermal substrate method, calcium phosphate coatings were prepared at substrate temperatures of 100-105 oC. The coated metallic implant surfaces with ceramic bond coats and calcium phosphate layers combine the excellent mechanical properties of metals with the chemical stability of ceramic materials. The corrosion test results show that the ceramic oxide (alumina) coatings and the double-layered alumina-calcium phosphate coatings improve the corrosion resistance compared with uncoated Ti6Al4V and single-layered Ti6Al4V/calcium phosphate substrates. In addition, the double-layered alumina/hydroxyapatite coatings demonstrate the best biocompatibility during in vitro tests.

Comparative analysis of electrophysical properties of ceramic tantalum pentoxide coatings, deposited by electron beam evaporation and magnetron sputtering methods

Ta2O5 ceramic coatings have been deposited on glass substrates by e-beam evaporation and magnetron sputtering methods. For the magnetron sputtering process Ta target was used. X-ray diffraction measurements show that these coatings are amorphous. XPS survey spectra of the ceramic Ta2O5 coatings were obtained. All spectra consist of well-defined XPS lines of Ta 4f, 4d, 4p and 4s; O 1s; C 1s. Ta 4f doublets are typical for Ta2O5 coatings with two main peaks. Scanning electron microscopy and atomic force microscopy images of the e-beam evaporated and magnetron sputtered Ta2O5 ceramic coatings have revealed a relatively flat surface with no cracks. The dielectric properties of the tantalum pentoxide coatings have been investigated in the frequency range of 100 Hz to 1 MHz. The electrical behaviour of e-beam evaporated and magnetron sputtered Ta2O5 ceramic coatings have also been compared. The deposition process conditions principally effect the structure parameters and electrical properties of Ta2O5 ceramic coatings. The coatings deposited by different methods demonstrate the range of dielectric parameters due to the structural and stoichiometric composition changes

Biocompatibility of dielectric Ta2O5 coatings in in vitro tests

A study was performed on the impact of the structure and properties of e-beam evaporated Ta2O5 films on the cell/material response. The surface properties and structure the films were investigated by means of XPS and XRD. The cyto toxicity and cyto compatibility were estimated by in vitro tests. Other parameters, such as the surface free energy (SFE) and fractional polarity, were determined by means of the Wu, and Owens-Wendt-Rabel-Kaelble methods. The dependence was followed of the cells adhesive behavior on the coatings surface composition and parameters. The best biological response parameters (total cell number, detached cells percentage, proliferation ratio) were obtained in the case of annealed Ta2O5 coatings with stoichiometric composition and the largest values of the SFE polar part and the of the fractional polarity.

Surface parameters modification by multilayer coatings deposition for biomedical applications

Studies are presented of the surface parameters of various multilayer coatings, namely, TiN, CrN, (Ti, Cr)N, TiN/TiC10N90, TiN/TiC20N80 deposited by means of Arc-PVD on stainless steel (1H18N9), as well as of the same coatings with an additional Al2O3 film deposited by reactive magnetron sputtering (RMS). The surface thickness, roughness and topography are estimated. Other parameters, such as the surface free energy (SFE) and fractional polarity are determined by means of the Wu and the Owens-Wendt-Rabel-Kaelble methods. Experiments are carried out on the in vitro cell/material interaction (in a fibroblasts culture) in order to determine the materials biomedical response. The results show some correlation between the surface properties and cell adhesion. The best biological response parameters (cell number, proliferation function, morphology) are obtained in the case of coatings with the highest values of the polar part component of the SFE and the fractional polarity, such as TiN, TiN/TiC10N90 and oxide coatings.

Tribological performance of ceramic coatings deposited on metal surfaces for micro-bearing biomedical applications

Modification of metal materials by means of ceramic coating deposition is an effective way of forming alternative bearing surfaces. Ceramic AlN, Al2O3 and nanocomposite oxynitride coatings are widely used as protective coatings against wear, diffusion and corrosion. The enhancement of the mechanical properties, such as hardness parameters, effective Youngs modulus, toughness, elastic recovery and wear resistance of the coatings, is very important for the tribological performance of the next generation of ceramic-coated ball bearing devices.

Modification of the structure and composition of Ca10(PO4)6(OH)2 ceramic coatings by changing the deposition conditions in O2 and Ar

Hydroxyapatite Ca10(PO4)6(OH)2 (HAp) is a material considered to be used to form structural matrices in the mineral phase of bone, dentin and enamel. HAp ceramic materials and coatings are widely applied in medicine and dentistry because of their ability to increase the tissue response to the implant surface and promote bone ingrowth and osseoconduction processes. The deposition conditions affect considerably the structure and bio-functionality of the HAp coatings. We focused our research on developing deposition methods allowing a precise control of the structure and stoichiometric composition of HAp thin films. We found that the use of O2 as a reactive gas improves the quality of the sputtered hydroxyapatite coatings by resulting in the formation of films of better stoichiometry with a fine crystalline structure.

Nanoscale surface modification of plastic substrates for advanced tissue engineering applications

Modified surface properties such as composition, nano roughness, wettability have effect on the most important processes at biomaterial interface. The research of stem cells (MSCs) adhesive potential, morphology, phenotypical characteristics on oxide coated and plastic substrate with different surface parameters was made. The oxide coatings deposition on plastic substrates shifts the surface properties at the more hydrophilic region and results in next positive cell/ biomaterial response in vitro tests. The MSCs marker number increases on the oxide nano structural surface of plastic substrates.

Surface modification of tantalum pentoxide coatings deposited by magnetron sputtering and correlation with cell adhesion and proliferation in in vitro tests

The effect was analyzed of surface treatment by argon ions on the surface properties of tantalum pentoxide coatings deposited by reactive magnetron sputtering. The structural parameters of the as-deposited coatings were investigated by means of transmission electron microscopy, atomic force microscopy and scanning electron microscopy. X-ray diffraction profiles and X-ray photoelectron spectra were also acquired. The total surface free energy (SFE), the polar, dispersion parts and fractional polarities, were estimated by the Owens-Wendt-Rabel-Kaeble method. The adhesive and proliferative potentials of bone marrow cells were evaluated for both Ta2O5 coatings and Ta2O5 coatings deposited by simultaneous bombardment by argon ions in in vitro tests.

Examination of surface and material properties of nanostructural oxide coatings for joint total and module replacement arthroplasty

Deposition of functional coatings on metal substra- tes (stainless steel 1H18N9, titanium alloy Ti6Al4V) makes it possible to combine biocompatibility of ceramics with advantages of metals for improving tribological characteristics of prostheses and creating new low-cost and innovative prototypes for defect replacement in patients of different age groups. The specific properties of nanostructural oxide coatings make them most promising for subsequent applications in implantology. High hardness parameters up to 9 Gpa, adhesion strength up to 40 N and a low friction coefficient with a strong tendency to decrease in fluids (0.07) were estimated. The corrosion test results show that oxide coating deposition had improved the corrosion resistance parameters by a factor of ten both for stainless steel and titanium substrates. The surface with oxide coatings demonstrated electrical inertness and capacitive properties. The hydrophilic property of coated surfaces versus the metal one was investigated by the method of tensiometry. Surfaces with nanostructural oxide coatings demonstrated improved biocompatibility due to dielectric properties and high values of surface energy.