The in-vitro biological and electrochemical interactions of electrically polarized commercially pure titanium used for orthopedic and dental applications
Date of Award
Doctor of Philosophy (PhD)
Biomedical and Chemical Engineering
Osteoblasts, Electrochemical impedance, Orthopedic implants, Titanium
Biomedical Engineering and Bioengineering | Engineering
This dissertation characterized, within a simulated biological environment, how applied voltage alters the electrochemical impedance of commercially pure titanium (cpTi) and, in turn, alters cpTi's in-vitro interaction with pre-osteoblasts. A newly developed potential step impedance analysis (PSIA) quantified the electrochemical impedance (solution resistance (R s ), polarization resistance (R p ), interfacial capacitance (C), and the constant phase element's exponent, (Alpha)) of the electrified interface. An electrochemical cell culture chamber was developed to potentiostatically control the voltage of the cpTi cell culture substrate and to perform PSIA.
Scanning PSIA and 24 hr static PSIA experiments were conducted in phosphate buffered saline (PBS), alpha modified eagles medium (AMEM), and AMEM supplemented with 10% fetal bovine serum (AMEM+FBS). These results showed that the short and long-term impedance properties of cpTi are dependent on voltage within the -1000 mV to +1000 mV range studied. Moreover, the presence of organic species (proteins, amino acids) in the electrolyte solution altered the short-term impedance properties only at cathodic potentials while having no effect at anodic potentials. Oxide growth occurred during the 24 hr immersion and static polarization in the range of 0 to +1000 mV resulting in decreased current density and increased R p , both by roughly 2 orders of magnitude. The R p decreased in a log-linear trend from 0 to -1000 mV. At -600 and -1000 mV, oxide modification and/or interaction with adsorbed organic species increased the capacitance during 24 hr immersion in all solutions except PBS at -600 mV. Capacitance values were largest for AMEM+FBS.
Static PSIA was also conducted concurrently with cell culture assessment of pre-osteoblast morphology and viability. The results of pre-osteoblasts cultured directly on cpTi at -600 and -1000 mV showed marked reductions in cell spreading and viability within 24 hrs, while polarization between -300 and +1000 mV shows no difference in cell behavior out to 72 hrs. The observed relationship between cell behavior and impedance indicated that electrochemical thresholds are present which influence cpTi's in-vitro interactions with pre-osteoblasts. These outcomes are clinically significant for modular orthopedic implants whose potential can shift, via fretting corrosion, down into the range of voltages exhibiting poor cell behavior.
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Ehrensberger, Mark T., "The in-vitro biological and electrochemical interactions of electrically polarized commercially pure titanium used for orthopedic and dental applications" (2008). Biomedical and Chemical Engineering - Dissertations. 8.