ICMCTF2019 Session DP-ThP: Coatings for Biomedical and Healthcare Applications (Symposium D) Poster Session

The use of composite coatings emerges as a great alternative to induce superficially the combination of properties widely desired in surgical implants, such as: osteointegration and bactericidal character, which can not be conferred by a single material. In the present investigation, the effect of the incorporation of an intermediate layer of titanium nitride (TiN) on the chemical composition, structure, morphology, phases and adherence of a multi-layer Hydroxyapatite (HA) - silver (Ag) coating deposited on Ti-6Al-4V by magnetron RF sputtering was evaluated. The elemental composition analysis was performed by energy dispersive spectroscopy, while the techniques of micro-Raman spectroscopy, scanning electron microscopy and atomic force microscopy were used to determine the structure and morphology of the obtained coatings. A variation in the Ca/P ratio, the Ag content and the thickness in the HA-Ag coatings deposited on the TiN layer was found compared to the HA-Ag system deposited on the metallic alloy. In the same way, the roughness and structure of this coating was modified according to the surface where it was deposited.

Key words: Magnetron sputtering, Hydroxyapatite, Ca/P ratio, structure, multi-layer coating, intermediate layers, critical load.

Electrode materials for neural stimulation have been widely investigated for implantable devices. Among them, iridium and iridium oxide are attractive materials for bio-interface applications due to their desirable stability, electrochemical performanc, and biocompatibility. In this study, metallic iridium thin film was deposited on a transparent conducting oxide substrate (ITO-coated glass) by radio-frequency (RF) magnetron sputtering, and we carried out an electrochemical activation to produce iridium oxide film through a repetitive biphasic pulsed current. The process parameters for sputtering of iridium film and electrochemical activation of iridium oxide film were optimized. The activated iridium oxide film exhibited superior electrochemical performance, including large charge storage capacity (CSC), high charge injection capability, low electrochemical impedance, and excellent stability. In addition, the biocompatibility of activated iridium oxide was evaluated by cytotoxicity, and the iridium oxide/iridium film showed high cell-viability. These findings suggest that the activated iridium oxide film is a promising candidate as an electrode material for the development of neurostimulating devices.

Polyetheretherketone (PEEK), known for its comparable elastic modulus to human cancellous bone characteristics and X-ray radiolucency, is greatly considered for spinal implant material. However, the bio-inertness and hydrophobic surface properties of PEEK results in poor osseointegration when implanted into human bodies. The aim of this study is to develop a combination method, viz., laser roughening process and titanium dioxide (TiO₂) deposition, for modifying the biological properties of PEEK surface. A femtosecond pulse laser was utilized to avoid the thermal damage on PEEK, while high power impulse magnetron sputtering (HIPIMS) was employed to deposited high crystallinic TiO₂ coating at low temperature. The results showed that the hierarchically patterned PEEK surfaces composed of nano- and microstructures can be obtained by adjusting laser parameters. Such structure resulted in varied surface roughness and water wetting ability. On the other hand, the highest rank (5B) in adhesion tape test proved the superior adhesion of the HIPIMS prepared TiO₂ coating even on roughened PEEK surface. The strong adhesion is believed to arise from the advantage of high ion energy and high-density plasma characteristics of the HIPIMS discharge. Under proper laser roughening condition followed by HIPIMS-TiO₂, the in vitro osteoblast compatibility test performed a much higher level than bare PEEK.

Titanium and its alloys have been widely used as biomaterials for orthopedic and dental implants because of their excellent biocompatibility and mechanical properties. However, they are considered to be bioinert, such that when they are inserted into the human body these implants cannot bond directly to the surrounding living bone. This study aimed to improve the bioactivity of a low-modulus Ti-5Nb-5Mo alloy with a hydroxyapatite (HA) surface coating using eggshells as a Ca source through hydrothermal reaction and heat treatment. The results showed that the whole alkali-treated alloy surface was covered with amorphous calcium phosphate nanoparticles after hydrothermal reaction at 200 °C for 48 h. When sub sequently heat-treated at various temperatures (400, 500 or 600 °C ) for 48 h, the surface coating of Ti-5Nb-5Mo alloy was transformed into crystalline rod-like HA nanoparticles. Also, heat treatment enhanced the adhesion between the HA coating and the Ti alloy substrate. Additionally, FTIR analysis confirmed the production of HA containing mixed AB-type carbonate substitutions. To evaluate bioactivity of the bone-like HA-coated Ti-5Nb-5Mo alloy, the capability of calcium phosphate apatite formation on the alloy surface was assessed by immersion in a simulated body fluid (SBF). Dune-like apatite layer was observed to densely deposit on the surface of HA-coated Ti alloy after 6 h of immersion in the SBF. Notably, the ability of Ti-5Nb-5Mo alloy subjected to sequential process with alkali, hydrothermal, and heat treatments to form bone-like HA nanoparticle coating was obviously greater than that of its counterpart without HA coating.

Recent studies have shown the potential use of nanodiamonds (NDs) as drug carriers for the therapy of cancer due to their high stability and small size. With the aim of obtaining a new system to be applied as drug delivery platform for the therapy of metastatic melanoma, a new technique of obtaining NDs from CVD diamond thin film was developed. The synthetic CVD-diamond film has similar physical and chemical properties to natural diamond: extreme hardness, excellent thermal conductivity, biological compatibility and chemical stability at temperatures below 800°C. Herein, CVD NDs were prepared by using laser ablation. The NDs were characterized by X-ray (XRD), (MEV-FEG), (TEM), energy dispersion spectroscopy (EDS), (XPS), Raman spectroscopy and dynamic light scattering. Furthermore, since cytocompatibility is one of the main features required for a drug delivery platform, the cytotoxicity of NDs was evaluated in B16-F10-Nex2 cells by MTT assay. The results showed that the laser ablation process reduced CVD particle size. The mean hydrodynamic diameter in aqueous suspension after the centrifugation changed from 54 nm. The high stability of aqueous suspension of CVD NDs was indicated by the low polidispersity index (0,2) and a small increase in the mean value of hydrodynamic diameter during the observed period (D = 215 nm). The high stability was provided by the high charge density on NDs surface as suggested by the high value of Zeta-potential (-36.39 and -30.94 mV). EDS analysis showed that NDs were composed of carbon (77.2%) and oxygen (22.2%). By X-ray diffraction analysis, it could be observed the characteristic peak of NDs at 43⁰. Raman spectrum of CVD NDs showed three peaks at: 1332, 1500 and 1600 cm^-1, corresponding to D and G bands of diamond. Cytotoxicity assay showed 60% and 80% of cell viability after 24h 48h 72h and 96h of incubation with NDs. The high value of cell viability is an indicative of the cytocompatibility of NDs, indicating the potential use of NDs in biomedical applications such as drug delivery platforms.

Coating technology offers innovative solutions to improve the quality and durability of medical devices. Among new materials, titanium oxynitride coatings (TiOxNy) are considered promising for applications in implantology (cardiovascular stents) due to their high biocompatibility. The purpose of this study is to test tantalum oxynitride coatings (TaOxNy) as a potential candidate in dental implants application. Coatings with different nitrogen and oxygen contents were deposited by conventional reactive magnetron sputtering and by High Power Impulse Magnetron Sputtering (HIPIMS) in mixed Ar-O₂-N₂ atmosphere. The coatings were deposited onto titanium micro-rough substrates (Ti-SLA) and stainless steel substrates. In some experiments water vapor was used as a reactive gas, instead of oxygen. The Ti-SLA uncoated sample was chosen as control in cellular response biological tests. None of the specimens presented any signs of cytotoxicity. Their biological response was similar to that of Ti-SLA. The coatings produced with water vapor showed an improvement of the corrosion resistance as well as a slight enhancement of cell adhesion. Even though the tantalum oxynitride coatings didn’t show a noticeable enhancement of biological response on Ti-SLA surfaces, their application looks promising on other substrates such as stainless steel.

Most of the surgical and odontological instrumentation is manufactured using martensitic stainless steel AISI 420 and 440 due to their acceptable biocompatibility, good hardenability, proper hardness and resistance to corrosion. However, the resistance to wear of this type of steels is relatively low and may be susceptible to contamination with bacteria representing a potential risk to the health of patients. This research work focused on the development of a coating system of titanium-aluminum-nitride doped with silver and copper nanoparticles TiAlN (Ag, Cu) to provide it with an appropriate bactericidal effect for possible biomedical applications.

TiAlN coatings doped with four different contents of Ag and Cu nanoparticles (11 at.% to 20 at.%) were deposited onto 420 steel by means of self- manufactured DC unbalanced magnetron sputtering using two composited targets of Ti/Al and Ag-Cu (both 50/50 at.% and 99.9% purity), which were facing each other at 180 degrees. The diffusion of the Ag-Cu nanoparticles to the sample surface, as well as their quantity, size, shape and distribution was controlled by an appropriate adjustment of the power applied to the Ag/Cu- target, the temperature and time of the deposition process, since the mechanical, tribological and bactericidal properties of the compound depend, among others, on these characteristics of the nanoparticles. The microstructure, surface topography, chemical and phase composition were analyzed by scanning and transmission electron microscopy (SEM/TEM), energy dispersive X-ray spectroscopy (EDX ) and X-ray difraction. To evaluate the bactericidal effect of steel and coated samples in vitro inhibition and adhesion test were carried out selected Staphylococcus aureus and Escherichia coli, two of the major pathogen frequently found in surgery and dentistry rooms and associated with infections . The coating without doping presents a structure of columnar growth, which becomes densified with the increase of the Ag-Cu content and takes a glassy appearance accompanied by an increased size of the Ag-Cu particles and consequently also in the surface roughness. All the coated samples exhibited a higher bactericidal effect in comparison with the uncoated and with TiAlN coated steel, however the greater inhibition (100%) and less adherence to both bacteria was showed by the sample coated with 17% at Ag-Cu . Based on the results obtained, the developed nanostructured coating system might be considered for potential application in surgical and dental instrumentation.

There is a high interest to investigate nanomaterials that can work effectively against different types of bacteria and provide alternative substitution for chemical substances and antibiotics. In this research, conductive materials nanoparticles in the form of thin films were deposited on water filter papers by using direct current (DC) high vacuum magnetron sputtering technique. The effectiveness of the nanoparticles to remove bacteria from polluted water was tested during the experiment. The morphology of the coatings and their adherence to the water filter paper was examined using the Scanning Electron Microscopy and their chemical composition was investigated using the X-ray diffraction technique. A ll thin films showed good adhesion to water filter fibers and ensured a high area of exposure to contaminated water. The antibacterial effect of different conductive thin films was characterized by using the standardized membrane filtering technique for water and wastewater examination. The testing media (i.e. contaminated water) containing bacterial samples were collected from local wastewater basins. Water was tested for the bacterial content before and after the exposure to conductive thin films coated filters.