Monitoring of metallic biomaterials interaction with model body environment
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1
University of Chemistry and Technology Prague, Department of Metals and Corrosion Engineering, Czechia
Introduction: In vitro testing of the activity of biomaterials is frequently executed in so called simulated body fluids (SBF). Exposure in SBF is mostly used as a yes/no test [1],[2]. Samples are removed from the environment after some period of exposure and the state of the surface is evaluated. The working hypothesis of this study is based on the fact that the surface of a metallic biomaterial exposed to SBF is gradually covered by a bone-like apatite layer. This procedure should change the electrochemical properties of the material surface/environment phase boundary and the time dependences of appropriate characteristics should be detectable.
Materials and Methods: The experimental beta alloy Ti36Nb5Ta (TiNbTa), cp titanium and a diamond-like carbon layer (DLC) deposited on cp Ti were chosen for measurements. The DLC coated samples were used as controls because bioinertness is expected in this case. Measurements were done in SBF [3], the duration was 14 days. The open circuit potential (Eocp), polarization resistance (Rp) and impedance at a constant frequency 2 kHz were detected with 2 hours periodicity. Once every 24 hours, the electrochemical impedance spectrum (EIS, 1.105-2.10-3 Hz) was measured. The surface state was evaluated after exposures by SEM/EDS analysis and photoelectron spectroscopy (XPS).
Results and Discussion:
EIS spectra changes with time are illustrated in figure. The response of DLC was stable throughout the whole period of exposure, according to XPS analysis no surface layer was created. The situation was completely different in the case of Ti and TiNbTa. In the very beginning of exposure, the EIS spectra course corresponded to the passive surface. Increasing the time of exposure led to a response of more complex system. The most significant influence was detected in the case of impedance measurements at a constant frequency. The beginning of surface changes started at the 84th hour for both Ti and TiNbTa. The period of layer creation leading to an overall change in the impedance response was finished in the 101st hour for Ti, 105th hour for TiNbTa. Eocp decreased over time, the change was approximately 50 mV. In both cases, it began in the 48th hour and proceeded up to the 144th hour. Rp represents the integral value of charge transfer resistance across the phase boundary. There was no distinct trend of Rp changes with time. The contribution of an added ohmic component (layer) was obviously not very important.
Conclusion: Measurements of Eocp and Rp for monitoring is possible, but not sensitive enough concerning the given systems. The EIS spectra in the whole range of frequencies are rich in information, an important drawback is the length of measurements. Constant frequency EIS is fast and able to monitor individual steps in surface changes. There was practically no apatite-like layer precipitation detected on the DLC coating. The interaction of Ti and TiNbTa with SBF was in principle the same.
The work was carried out as a part of the MZ 15-27726A project, which is financially supported by Ministry of Health, Czech Republic.
References:
[1] Maleki-Ghaleh H, Hajizadeh K, Hadjizadeh A, Shakeri MS, Ghobadi Alamdari S, Masoudfar S et al. Electrochemical and cellular behavior of ultrafine-grained titanium in vitro. Materials Science and Engineering: C. 2014;39:299-304
[2] Pittrof A, Bauer S, Schmuki P. Micropatterned TiO(2) nanotube surfaces for site-selective nucleation of hydroxyapatite from simulated body fluid. Acta Biomater. 2011;7(1):424-31
[3] Kokubo T, Takadama H. How useful is SBF in predicting in vivo bone bioactivity? Biomaterials. 2006;27(15):2907-15
Keywords:
Surface modification,
surface property
Conference:
10th World Biomaterials Congress, Montréal, Canada, 17 May - 22 May, 2016.
Presentation Type:
Poster
Topic:
Surface and interfacial characterization
Citation:
Joska
L and
Fojt
J
(2016). Monitoring of metallic biomaterials interaction with model body environment.
Front. Bioeng. Biotechnol.
Conference Abstract:
10th World Biomaterials Congress.
doi: 10.3389/conf.FBIOE.2016.01.01897
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Received:
27 Mar 2016;
Published Online:
30 Mar 2016.
*
Correspondence:
Dr. Ludek Joska, University of Chemistry and Technology Prague, Department of Metals and Corrosion Engineering, Prague, Czechia, Email1
Dr. Jaroslav Fojt, University of Chemistry and Technology Prague, Department of Metals and Corrosion Engineering, Prague, Czechia, fojtj@vscht.cz