ICMCTF2016 Session DP: Symposium D Poster Session

TiCaPCON-Ag films with various Ag content were deposited by magnetron sputtering onto Ti substrates with different surface roughness. Doping with Ag was found to result in the formation of Ag nanoparticles, 5–10 nm in size, located on the film surface. The kinetics of Ag⁺ ion release from the films into physiological solution was studied by inductively coupled plasma mass spectrometry. An increase in Ag⁺ ion concentration in normal saline is caused by dissolution of the Ag nanoparticles. An increase in the specific surface area markedly accelerates the release of Ag⁺ ions into solution. An increase in the Ag content of films results in faster dissolution of Ag nanoparticles at initial stages but favors earlier exhaustion of the surface. It has been demonstrated that the process of Ag⁺ ion leaching out of the surface can be well controlled by varying the substrate surface roughness and the Ag content of the films. Bioactivity of Ag-doped TiCaPCON films was evaluated in vitro using simulated body fluid (SBF) and compared with that of bioactive glass Biogran. After immersion in SBF, the structure and chemistry of surface were well characterized using a combination of various microanalytical techniques, such as scanning electron microscopy, X-ray diffractometry (both in conventional and grazing incidence mode), Fourier transform infrared spectroscopy, Raman spectroscopy, and glow discharge optical emission spectroscopy. The results showed that the surface of the Ag-doped TiCaPCON films was bioactive in vitro and induced the formation of an apatite layer during exposure in SBF. The apatite layer was formed over 14 days. Various factors (film structure, surface roughness, surface functional groups, surface charge and composition, supersaturation, and near-surface local supersaturation of SBF) affecting the kinetics of bone-like apatite formation on a bioactive surface are discussed.

Surface biocompatibility has been intensively studied in connection with medical implants. Various factors like surface wettability, roughness or chemical composition have been found to influence the biocompatibility. We focused our attention on studying coatings prepared from an electrically bioactive material (i.e. a ferroelectric influencing the adhesion, growth and differentiation of osteogenic cells) as a new trend for hard tissue replacement. TiNb is high corrosion resistant and nontoxic material potentially applicable as a support for these ferrolectric coatings. In the first step, we investigated TiNb coatings deposited by magnetron sputtering on substrates made from Ti, Ti alloys Ti39Nb and Ti6Al4V and stainless steel. Optimal conditions for deposition of chemically stable and biocompatible coatings were found. Significant layer properties as crystalline structure, chemical composition, roughness, etc. were characterized. It was found that the layer properties substantially depend on the substrate type.

In the next step, the TiNb coatings was covered using a method described elsewhere by a spontaneously polarized ferroelectric film (BaTiO3, LiNbO3) with an electric charge on the surface. Growth of the human osteogenic cells was used as the surface biocompatibility test. Biocompatibility of the surfaces prepared by these two methods were compared.

Magnesium is widely used in the electrical, automotive and space industry, for being a lightweight material and for combining properties such as high strength to weight ratio, good thermal and electrical conductivity, excellent shock absorption, high damping capacity and electromagnetic shielding performance [1]. It is also bioactive, biodegradable and bio-absorbable, which allows magnesium to be used as a temporary implant [2]. However, magnesium active nature makes it a very unstable metal in aqueous environments and consequently it has a high corrosion rate. One way to improve this disadvantage, can be by using plasma electrolytic oxidation (PEO), whose purpose is to allow the formation of a porous oxide layer on the substrate surface, giving environmental protection [3]. However, the formation of coatings on pure Mg by Plasma Electrolytic Oxidation has not been widely studied due to the high active nature of the metal. In this work, two different phosphate-based electrolytes were used to obtain anodic films on pure Mg with Hexamethylenetetramine and NaF additions. Samples were mechanically polished down to # 2000 with SiC paper, washed in acetone using an ultrasonic bath and dried with a cold air stream. Hydrogen evolution studies, Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS) and Fourier Transform Infrared Spectroscopy (FTIR) were employed to study the composition, morphology and corrosion resistance of the films. Results show changes in the morphology and porosity of the anodic coatings obtained as the anodizing conditions were varied. Formation of coatings with low porosity were obtained when NaF was added to the anodizing solution, showing better corrosion resistance as evidenced by the hydrogen evolution studies, despite the thickness is lower than other coatings obtained. Regarding the chemical composition of the coatings, there are not significant different among them.

References

[1] A. Atrens, G.-L. Song, M. Liu, Z. Shi, F. Cao, and M. S. Dargusch, “Review of Recent Developments in the Field of Magnesium Corrosion,” Adv. Eng. Mater., vol. 17, no. 4, pp. 400–453, Apr. 2015.

[2] H. Hornberger, S. Virtanen, and a R. Boccaccini, “Biomedical coatings on magnesium alloys - a review.,” Acta Biomater., vol. 8, no. 7, pp. 2442–55, Jul. 2012.

[3] P. B. Srinivasan, J. Liang, C. Blawert, M. Störmer, and W. Dietzel, “Characterization of calcium containing plasma electrolytic oxidation coatings on AM50 magnesium alloy,” Appl. Surf. Sci., vol. 256, no. 12, pp. 4017–4022, Apr. 2010.

Hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂, HAp) is materials mainly known for its special ability to contact bone tissue. HAp coated implants, mainly prepared by plasma spraying have shown to increase the quality of adhesion of structural prostheses and to reduce particle release from the metal surface. However, the in vivo tests of these coatings have shown lack of bonding strength to the metallic bio-inert substrate or resorption. It is well known that natural HAp contains lot of trace elements that play very important roles in the biological process. Functional elements doped in HAp can be easily fabricated by adding the related ions into the reactions, such as Mg, Mn, Zn, Si, and Sr.

It is generally noted that Si is essential to the growth and development of biological tissue such as bone, teeth and some invertebrate skeleton. Mg is the fourth most abundant cation found in extracellular matrix of bone. Mg deficiency is reported to reduce the bone density and ductility, and increases the chance of bone fracture.

In this study, we prepared Si and Mg co-doped nano-phase HAp film on the (low elastic modulus) Ti-25Ta-xHf (0, 3, 7, 15 wt.%) alloy nano-network surface using the electrochemical deposition method. The deposition process involved two steps, 1) Ti nano-network on Ti-25Ta-xHf alloy was formed at high current in NaOH solution; 2) electrochemical deposition method was carried out in electrolyte for Si and Mg co-doped nano-phase HAp deposition on TiO₂ nano-network surface. The range of lateral pore size of the network specimen was about 10–120 nm on Ti surface by anodized in 5 M NaOH solution at 0.3 A for 10 min. Nano-network TiO₂ surface were formed by this anodization step which acted as templates and anchorage for growth of the HAp during subsequent pulsed electrochemical deposition process at 85℃. High purity Ca(NO₃)₂, Mg(NO₃)₂, Na₂SiO₃ and NH₄H₂PO₄ were used as starting materials.

The morphology and crystalline structure of Si and Mg co-doped nano-phase HAp on the Ti nano-network surface was characterized using a thin film X-ray diffractometer (TF-XRD) and field emission scanning electron microscopy (FE-SEM). Elemental analysis was performed using an energy dispersive X-ray spectroscopy (EDS).

A multilayer Ti nano-network was produced rapidly on Ti-25Ta-xHf surface a simple electrochemical anodized treatment. The enhancement of the HAp-forming ability arise from Ti nano-network surface, which is formed the conversion of the sodium titanate gel on the electrochemical anodized treatment. The phase and morphologies of deposits HAp were influenced by the Ti surface morphologies, current density and Si and Mg ion concentration. (Supported by NRF: 2015H1C1A1035241 : hcchoe@chosun.ac.kr)

Surgical implants are usually fabricated from light metal or alloys such as Ti and Ti alloys which exhibit superior mechanical properties such as tensile strength, toughness and fatigue resistance. The surfaces of metallic implants are usually coated with bioactive material to improve the biocompatibility of the metallic implant while preserving the useful mechanical properties of the implant materials. Since their introduction in the 1980s, hydroxyapatite [(Ca₁₀(PO₄)₆(OH)₂), HAp] coatings on orthopedic implants have gained wide acceptance in metallic implants because of its excellent biocompatibility and chemical composition close to that of natural bone. It is well-known that natural HAp contains lot of trace elements which play very important roles in the biological process. Functional elements doped in HAp can be easily fabricated by adding the related ions into the reactions, such as Mg, Mn, Zn, Sr, and Si. In addition, silicon-doped HAp (Si–HAp) has been reported and the materials have been shown to enhance the rate and quality of bone tissue repair in bioactive coating technology. Because Si is the essential element for higher biological organism, and it has been considered to play an important role in bone metabolism.

In this study, we prepared Si-doped HAp coated on the Ti-6Al-4V for dental applications. In order to form Si-HAp films on the Ti-6Al-4V alloy, first, electrochemical deposition for HA precipitation was carried out using cyclic voltammetry (CV) method with scanning potential between 0 V to -1.5 V at scan rate 100 mV/s on 85℃. In the mixed Ca(NO₃)₂, Si(Na₂SiO₃) and NH₄H₂PO₄ solution..

The morphology and crystalline structure of Si-doped nano-phase HAp on the TiO₂ nano-network surface was characterized using a thin film X-ray diffractometer (TF-XRD) and field emission scanning electron microscopy (FE-SEM). Elemental analysis was performed using an energy dispersive X-ray spectroscopy (EDS), and fourier transform infrared spectroscopy (FT-IR). (Supported by NRF : 2015H1C1A1035241:hcchoe@chosun.ac.kr)

The possibility of substituting the hard tissue instrumentations like artificial bones, artificial hip joints, artificial teeth, and dental implants for functionally disordered hard tissues like bone and teeth has been grown recently. Titanium (Ti) and its alloys have been fast emerged as the most attractive choice for the majority of medical applications. Commercially pure Ti (CP-Ti) and Ti-6Al-4V ELI have been an important biomaterial in this field for a long period, due to its high specific strength, excellent corrosion resistance, and superior biocompatibility. It is difficult to achieve a chemical bonding with the bone issue and form a new bone on its surface at an early stage after the implantation. Even though titanium as well as its oxides are known to be bio-inert and despite some reports of their direct bonding to bone, most authors state that there is no strong bonding between the bone tissue and titanium or its oxide. Various ways of physical and chemical treatments of Ti surface have been proposed to overcome this drawback and to produce a better biocompatible implant surface.

Manganese (Mn) influences regulation of bone remodeling, and its deficit causes reduction of organic matrix synthesis and retards endochondral osteogenesis, increasing the possibility of bone abnormalities such as decrease of bone thickness or length.

Plasma electrolyte oxidation (PEO) is a promising technology to produce porous and firmly adherent inorganic Mn containing TiO₂ (Mn-TiO₂) coatings on Ti surface, and the amount of Mn introduced into the coatings can be optimized by altering the electrolyte composition. In this study, a Mn-TiO₂ coatings were produced on Ti dental implant using PEO, with the substitution degree, respectively, at 0, 5, 10 and 20%. Based on the preliminary analysis of the coating structure, composition and morphology and a bone like apatite formation model were used to evaluate the in vitro biological responses at the bone-implant interface.

The enhancement of the bone like apatite forming ability arises form Mn-TiO₂ surface, which has formed the reduction of the Mn ions. The promising results successfully demonstrate the immense potential of Mn-TiO₂ coatings in dental and biomaterials applications.

Commercially pure titanium (Cp-Ti) and Ti-6Al-4V ELI possesses many good mechanical properties such as high-fracture toughness and fatigue strength. However, being bioinert, the integration of such implant in bone was not in good condition to achieve improved osseointergraiton, there have been many efforts to modify the composition and topography of implant surface. To overcome this drawback, hydroxyapatite (HAp) has been applied as coating materials on Ti alloy implants for hard tissue applications because its chemical similarity to the inorganic component of human bone, capability of conducting bone formation and strong affinity to the surrounding bone tissue.

Recent studies have shown that cells in the human body are predisposed to interact with nano-structured surfaces, such as surface of nano-scale roughness and surfaces with immobilized nano-particles. Thus nano-phase on implant surfaces, e.g., a coating composed of nano HAp particles on Ti and Ti alloys, have aroused increasing research interest in the biomedical field.

In particular, a number of investigations have raised concerns associated with commercially available high temperature plasma-sprayed HAp coatings, such as poor control over coating composition, phase, crystallinity, thickness, morphology, and resistance to delamination. Consequently, alternative techniques for the fabrication of HAp coatings have been investigated and developed. Compared with other methods, electrochemically deposited HAp exhibits a higher degree of control over crystallinity under milder conditions and shorter reaction times. Furthermore, a film thickness of less 1 ㎛- can be achieved. Reduction of the film thickness leads to an increased resistance to delamination, which is observed frequently for thicker coating. However, there is potentially low adhesive strength of the coating, which can be overcome by combination with anodic growth of oxide layers. In order from HAp films on the Ti-6Al-4V alloy, electrochemical deposition of HAp precipitation was carried out using cyclic voltammetry (CV) method with scanning potential between 0V to -1.0 to -2.0 V on 85 ^oC. In the mixed Ca(NO₃)₂ and NH₄H₂PO₄ solution.

In this study, electrochemical deposition HAp has been carried out on anodized Ti surface. The anodization process in specific electrochemical method resulted in nano-network TiO₂ structure. Deposition of nano-phase HAp crystals that grow from nano-network TiO₂ structure in various electrochemical factors.

Commercial pure titanium (CP Ti) and Ti-6Al-4V alloy have been widely used for orthopedic implant materials and dental implant materials because of its excellent combination of biocompatibility, corrosion resistance, and mechanical properties. However, being bioinert, the integration of such implant in bone was not in good condition to achieve improved osseointergraiton, there have been many efforts to modify the composition and topography of implant surface. To overcome this drawback, calcium phosphate (CaP) has been applied as coating materials on Ti alloy implants for hard tissue applications because its chemical similarity to the inorganic component of human bone, capability of conducting bone formation and strong affinity to the surrounding bone tissue. Various metallic elements, such as strontium (Sr), magnesium (Mg), zinc (Zn), sodium (Na), silicon (Si), silver (Ag), and yttrium (Y) are known to play an important role in the bone formation and also affect bone mineral characteristics, such as crystallinity, degradation behavior, and mechanical properties.

Zn is essential for the growth of the human and other animals. Bone growth retardation is a common finding in various conditions associated with Zn deficiency, suggesting a physiological role of Zn in the growth and mineralization of bone tissue.

Plasma electrolyte oxidation (PEO) is a promising technology to produce porous and firmly adherent inorganic Zn containing TiO₂ (Zn-TiO₂) coatings on Ti surface, and the amount of Sr introduced into the coatings can be optimized by altering the electrolyte composition. In this study, a series of Zn-TiO₂ coatings were produced on Ti dental implant using PEO, with the substitution degree, respectively, at 0, 5, 10 and 20%. Based on the preliminary analysis of the coating structure, composition and morphology, a bone like apatite formation model is used to evaluate the in vitro biological responses at the bone-implant interface.

The enhancement of the bone like apatite forming ability arises form Zn-TiO₂ surface, which has formed the reduction of the Zn ions. The promising results successfully demonstrate the immense potential of Zn-TiO₂ coatings in dental and biomaterials applications. (Supported by NRF-20080062283 & 2015H1C1A1035241 :hcchoe@chosun.ac.kr)

Diamond-like carbon (DLC) coating have been prepared with Indian clove oil, Syzygium aromaticum, in polyurethane substrates. Chemical and fungicide properties of DLC coatings with and without Indian clove were analyzed. The DLC coatings were deposited using a Directed Liquid Plasma Chemical Vapor Deposition (DLP-CVD). Carbon precursors for DLC coating were provided by hexane and Indian clove liquid mixture. The polyurethane substrates were chosen due to its use in the manufacture of catheters and in many others biological applications. Therefore, DLC with Indian cloves properties deposited in polyurethane substrates are aiming polymeric surfaces with fungicide properties. The Indian clove active principle was provided by Eugenol. The parameters used in DLP-CVD were controlled in order to preserve Eugenol properties in DLC. The final coatings containing DLC:eugenol were analyzed by Raman spectroscopy and were used in fungicide tests. The fungicide tests were run out using biofilm growth and development of yeasts of the Candida genus were grown-up in vitro. The results indicated DLC:eugenol were deposited as an adherent, uniform and flexible coating in polyurethane substrate. The results using colony-forming units in (CFU/ml) and a qualitative method using the technique of scanning electron microscopy (SEM) reveal DLC:eugenol coating a promising coating for polymeric surfaces with fungicide properties.

The Ti-6Al-4V alloy is widely used for various bone substitute applications, including orthopedic and dental implants. However, there are some problems of Ti-6Al-4V alloy such Alzheimer’s disease of aluminum, toxicity of vanadium, high elatic modulus, and low corrosive-wear resistance. For improving this problem, some researchers have focused on Ti-Ta-Hf alloys systems with controlling the contensts of Ta and Hf elements.

However, being bio-inert metallic implant, they cannot bond to living bone directly after implantation into host body. Hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂, HAp) is materials mainly known for its special ability to contact bone tissue. HAp coated implants, mainly prepared by plasma spraying have shown to increase the quality of adhesion of structural prostheses and to reduce particle release from the metal surface. However, the in vivo tests of these coatings have shown lack of bonding strength to the metallic bio-inert substrate or resorption. It is well-known that natural HAp contains lot of trace elements which play very important roles in the biological process. Functional elements doped in HAp can be easily fabricated by adding the related ions into the reactions, such as Mg, Mn, Zn, Si, and Sr.

Mg ion is the most abundant, amounting typically around 6 mol%, in cartilage and bone tissue during the initial phases of osteogenesis, while it tends to disappear when the bone is mature. Mg deficiency adversely affects all stages of skeletal metabolism, causing cessation of bone growth, de- crease of osteoblastic and osteoclastic activities, osteopenia and bone fragility.

In this study, we prepared Mg-doped nano-phase HAp film on the nanotubular structure using the anodization. The deposition process involved two steps, 1) nanotubular structure on Ti-30Ta-xHf (x=0, 3, 7 , 15 wt.%) was formed at 30V for 2h in 1M H₃PO₄ +0.8 wt.% NaF mixed solution; 2) electrochemical deposition method was carried out in electrolyte for Mg doped nano-phase HAp deposition on nanotubular structure. Nanotubular structure was formed by this anodization step which acted as templates and anchorage for growth of the HAp during subsequent pulsed electrochemical deposition process at 85℃. High purity Ca(NO₃)₂, Mg(NO₃)₂ and NH₄H₂PO₄ were used as starting materials.

The morphology and crystalline structure of Mg-doped nano-phase HAp on the nanotubular structure was characterized using a thin film X-ray diffractometer (TF-XRD) and field emission scanning electron microscopy (FE-SEM). Elemental analysis was performed using an energy dispersive X-ray spectroscopy (EDS) (Supported by NRF: 2015H1C1A1035241 : hcchoe@chosun.ac.kr)