Chi-Jen Chung

Systematic strontium substitution in hydroxyapatite coatings on titanium via micro-arc treatment and their osteoblast/osteoclast responses.

This study attempts to enhance the osseointegration of titanium implants by adopting a micro-arc treatment (MAT) capable of replacing calcium (Ca) with different percentages of strontium (Sr) in order to fabricate strontium-containing hydroxyapatite (Sr-HAp) coatings. Sr, regarded as a significant therapy promoting bone mass and bone strength, has a dual mechanism, enhancing osteoblast differentiation and inhibiting osteoclast differentiation. This study also investigates how Sr content affects the microstructure of and osteoblast/osteoclast growth on the coatings. Experimental results indicate that an increase in the Sr content in the electrolyte bath results in a greater degree of Sr substitution at Ca sites within the HAp phase, facilitating the formation of Sr-HAp coatings with Sr fully solid soluble in the HAp phase. Irrespective of the Sr content, most coatings are similar in porous morphology and pore size. Additionally, the Sr-HAp coating shows higher osteoblast compatibility than raw titanium metal and the HAp coating. Moreover, cell adhesion and proliferation after 48 h was greater than that after 4 h, indicating that Sr can stimulate osteoblast adhesion and proliferation. Further, Sr significantly inhibits osteoclast differentiation when the Sr-HAp coatings exceed 38.9 at.% Sr.

Plasma electrolytic oxidation of titanium and improvement in osseointegration

Reducing the osseointegration time for biomedical titanium implants in surgical patients is an important goal. However, a huge controversy exists over the effectiveness of osseointegration of the surface layer by plasma electrolytic oxidation (PEO), which is a widely favored surface modification for titanium-based implants. In this study, various surface coatings, including anatase-TiO2 (A-TiO2 ), rutile-TiO2 (R-TiO2 ), hydroxyapatite (HAp), strontium-containing hydroxyapatite (Sr-HAp), and dual-phase HAp-TiO2 were synthesized on titanium implants by PEO. A comparative study of osseointegration performance (both in vitro and in vivo) and bone/implant adhesion strength conducted using push-out thrust tests were demonstrated. The in vitro experimental test results agree strongly with the in vivo test results: the dual-phase HAp-TiO2 coating exhibits the superior cell adhesion and differentiation condition among all of the coatings in the in vitro tests and therefore has the highest push-out bonding strength of 5.37 MPa after 12 wk of implantation in the in vivo test. The HAp-containing coatings benefit from its bioactivity and therefore perform the others in terms of long-term osteocyte growth (from the in vitro results) and the extent of osseointegration (from the in vivo results). The dual-phase HAp-TiO2 coating provides the advantages of both the bioactive HAp and structural enhancement by the TiO2 , effectively promoting osseointegration.

Improved osteoblast compatibility of medical-grade polyetheretherketone using arc ionplated rutile/anatase titanium dioxide films for spinal implants.

Titanium dioxide (TiO(2)), known to exhibit good biocompatibility, is applied in this study as a thin film formed onto polyetheretherketone (PEEK) substrate, which has been widely used in spinal interbody fusion cages. For successful deposition, an arc ionplating (AIP) technique was applied to deposit TiO(2) at low deposition temperature without damaging PEEK substrate, while providing satisfactory film adhesion. This study systematically investigates the effects of TiO(2) thin film phase composition and surface characteristics, controlled by using different target current and substrate bias, on osteoblast compatibility. Experimental results showed that anatase phase (A-TiO(2)) and/or rutile phase (R-TiO(2) ) TiO(2) coatings, respectively, can be prepared in appropriate deposition conditions. Overall, the TiO(2)-coated PEEK presented better osteoblast compatibility than the bare PEEK material in terms of cell adhesion, cell proliferation, and cell differentiation abilities, as well as osteogenesis performance (as determined by levels of osteopontin, osteocalcin, and calcium content). Surface roughness and hydrophilicity of the AIP-TiO(2) films were found to be responsible for significant osteoblast cell growth. It is also noticeable that the R-TiO(2) exhibited better osteoblast compatibility than the A-TiO(2) due to the presence of negatively charged hydroxyl groups on R-TiO(2) (110) surface in nature.

In Vivo Osseointegration Performance of Titanium Dioxide Coating Modified Polyetheretherketone Using Arc Ion Plating for Spinal Implant Application

Polyetheretherketone (PEEK), which has biomechanical performance similar to that of human cancellous bone, is used widely as a spinal implant material. However, its bioinertness and hydrophobic surface properties result in poor osseointegration. This study applies a novel modification method, arc ion plating (AIP), that produces a highly osteoblast compatible titanium dioxide (TiO2) coatings on a PEEK substrate. This PEEK with TiO2 coating (TiO2/PEEK) was implanted into the femurs of New Zealand white male rabbits to evaluate its in vivo performance by the push-out test and histological observation. Analytical results show that AIP can prepare TiO2 coatings on bullet-shaped PEEK substrates as implant materials. After prolonged implantation in rabbits, no signs of inflammation existed. Newly regenerated bone formed more prominently with the TiO2/PEEK implant by histological observation. The shear strength of the bone/implant interface increases as implantation period increases. Most importantly, bone bonding performance of the TiO2/PEEK implant was superior to that of bare PEEK. The rutile-TiO2 coatings achieved better osseointegration than the anatase-TiO2 coatings. Therefore, AIP-TiO2 can serve as a novel surface modification method on PEEK for spinal interbody fusion cages.

Enhancement of bioactivity on medical polymer surface using high power impulse magnetron sputtered titanium dioxide film.

This study utilizes a novel technique, high power impulse magnetron sputtering (HIPIMS), which provides a higher ionization rate and ion bombardment energy than direct current magnetron sputtering (DCMS), to deposit high osteoblast compatible titanium dioxide (TiO2) coatings with anatase (A-TiO2) and rutile (R-TiO2) phases onto the biomedical polyetheretherketone (PEEK) polymer substrates at low temperature. The adhesions of TiO2 coatings that were fabricated using HIPIMS and DCMS were compared. The in vitro biocompatibility of these coatings was confirmed. The results reveal that HIPIMS can be used to prepare crystallinic columnar A-TiO2 and R-TiO2 coatings on PEEK substrate if the ratio of oxygen to argon is properly controlled. According to a tape adhesion test, the HIPIMS-TiO2 coatings had an adhesion grade of 5B even after they were immersed in simulated body fluid (SBF) environments for 28days. Scratch tests proved that HIPIMS-TiO2 coatings undergo cohesive failure. These results demonstrate that the adhesive force between HIPIMS-TiO2 coating/PEEK is stronger than that between DCMS-TiO2 coating/PEEK. After a long period (28days) of immersion in SBF, a bone-like crystallinic hydroxyapatite layer with a corresponding Ca/P stoichiometry was formed on both HIPIMS-TiO2. The osteoblast compatibility of HIPIMS-TiO2 exceeded that of the bare PEEK substrate. It is also noticeable that the R-TiO2 performed better in vitro than the A-TiO2 due to the formation of many negatively charged hydroxyl groups (-OH(-)) groups on R-TiO2 (110) surface. In summary, the HIPIMS-TiO2 coatings satisfied the requirements for osseointegration, suggesting the possibility of using HIPIMS to modify the PEEK surface with TiO2 for spinal implants.

Microstructure, Mechanical and Electrochemical Properties of Arc Ion Plated Titanium Dioxide on Polyetheretherketone

The arc ion plating (AIP) technique is known to be capable of providing high film deposition rate and strong film adhesion. Titanium dioxide (TiO2) is characterized by its high chemical stability, photocatalysis and biocompatibility nature. The present study employed AIP to deposit TiO2 onto polyetheretherketone (PEEK) at low temperature. This study investigates the microstructure, mechanical and electrochemical properties of the TiO2 coatings as affected by the coating variables for some possible applications. The experimental results indicate that a crystallinic columnar film containing a controllable ratio of anatase to rutile phase can be prepared. The pencil hardness of the PEEK material graded as 4H was increased to over 9H by AIP-TiO2 coating. The film adhesion of the AIP-TiO2 coating can ultimately reach a critical load of 15 N and is associated with its deposition condition, but exhibits the cohesive failure mode (of the scratch scar) regardless of its deposition condition. The polarization behavior of the TiO2 coating in 3.5 wt.% NaCl electrolyte reveals that the AIP-TiO2 coating presents a greater electrochemical inertness if the rutile phase exists. The coating is, however, close to the electrochemical behavior of graphite material in all cases.

Characteristics of Micro-Arc Treated Osseointegrated Porous Hydroxyapatite/Titanium Dioxide Coatings on Titanium Metal

A rapid and sufficient osseointegrating functions is obviously essential to the patients who suffered the bone reconstruction period. In order to perfectly target this issue, a single-stage micro-arc treated (MAT) coating beneficial from its inherent porous morphologies with controllable pore sizes, strong adhesive force between coatings and substrate and wide selections in electrolytes, is considered. Hydroxyapatite is extensively utilized and identified as mimic composition to human bone and an active bone ingrowth function. However, a controllable high-purity HAp phase via one-stage MAT has not yet been achieved. This study therefore prepares high-purity HAp coatings using one-stage MAT with the electrolyte combination of Calcium acetate and sodium biphosphate dihydrate on a titanium surface through a systematical evaluation of various MAT parameters, including Ca/P ratios of the electrolyte, electrolyte concentrations, working voltages, and treatment periods. Analytical results show that high-purity HAp can grow at a relatively high Ca/P ratio and electrolyte concentration when combined with a relatively high working voltage and long treatment time, which would otherwise grow with CaTiO3 and/or anatase TiO2 and/or rutile TiO2 simultaneously. Additionally, CaTiO3 acts a precursor phase for HAp formation. Ultimately, the highest purity of HAp coating is obtainable on metal titanium using a Ca/P ratio = 2.16 and applying a working voltage of 450 V for 10 min using one-stage MAT. This highest purity of HAp coating also presents excellent level of Ecorr than that on raw Ti alloys. The high Ecorr of HAp coating contributed from its thick and dense oxide layer by working voltage via one-stage MAT, consequently promises its satisfactory protection. The HAp coating demonstrated in this study not only provides the effective approach to produce the desired purity of HAp coatings but compromises its resistance to SBF. The bioactive HAp coating on Ti alloys via one-stage MAT, thus, considers as one significant surface modification for artificial hip joints and dental implants.