Survivability of Titanium Implant Materials: In Vitro Simulated Inflammatory and Infectious Environment

Abstract

Titanium-based implants utilized in total joint arthroplasties could restore primary musculoskeletal function to patients suffering from osteoarthritis and other conditions. Implants are susceptible to failure stemming from aseptic loosening and infection at the joint site, eventually requiring revision surgery. We hypothesized that there might be a feedback loop by which metal degradation particles and ions released from the implant decrease cell viability and increase immune response, thereby creating biochemical conditions that increase the corrosion rate and release more metal ions. This study focused on the synergistic process through cell viability assays and electrochemical tests. From the results, inflammatory conditions from ion release resulting in cell death would further increase the corrosion rate at the metal implant site. The synergistic interaction in the implant surroundings in which infectious conditions produce Ti ions that contribute to more infection, creating a potential cycle of accelerating corrosion.

Keywords: Corrosion; Implant failure; Macrophage; Titanium.

Fig. 1

The schematic representation of the overall experimental design of this proposed study. Part 1 evaluates the cellular response of MG-63 osteosarcoma cells cultured with different concentrations of Ti particles and ions, Part 2 evaluates the cell behavior with various inflammatory conditions, and Part 3 studies the electrochemical behavior of Ti metal sample using the cell-secreted media at different conditions as the electrolyte

Fig. 2

The figure represents the MG-63 cells’ responses in the presence of Ti particles and ions at different concentrations. There was no toxicity observed with the cells in the presence of Ti particles from 1 to 50 ppm. However, a steady decline in cell viability between treatments of 0–20 ppm Ti ions showed a significant drop in viability between 20 and 50 ppm Ti ions. Also 20 and 50 ppm Ti ions were chosen to replicate infectious conditions as they appear to challenge cells but not destroy them

Fig. 3

The graph represents the MG-63 cytotoxicity evaluation under the inflammatory and infectious conditions using hydrogen peroxides and lactic acid. From the results we observe both hydrogen peroxide and lactic acid decreases the cell viability. However, hydrogen peroxide is generally more toxic than lactic acid. The cell viability declines in the presence of 20 ppm Ti ions, with hydrogen peroxide and also with combined solution. Overall, the combined solution with 50 ppm Ti ion seems to be very toxic

Fig. 4

Treatments: control (a), 0.5 mM H₂O₂ + 20 ppm Ti ions (b), 0.5 mM H₂O₂ + 50 ppm Ti ions (c), 0.23 μL/mL lactic acid + 20 ppm Ti ions (d), 0.23 μL/mL lactic acid + 50 ppm Ti ions (e), 0.5 mM H₂O₂ + 0.23 μL/mL lactic acid + 20 ppm Ti ions (f), 0.5 mM H₂O₂ + 0.23 μL/mL lactic acid + 20 ppm Ti ions (g). i This imaging corroborates the findings of alamarBlue assay results. It also highlights the disparity in cell viability between the most infectious/inflammatory conditions (g), and a healthy implant environment (control a). ii The bar graph represents 4% fluorescent intensity of the live and dead cells in the given various treatment conditions

Fig. 5

Data collected from the potentiodynamic test in the corrosion study a Tafel’s plot obtained from the EIS analysis, b the Ti sample exposed to the challenged media has the greater E_corr value, and c the Ti sample exposed to the challenged media has the greater I_corr value. The obtained results suggest that the sample underwent higher corrosion in the presence of challenged media

Fig. 6

Bode and Nyquist plots—a Bode plot obtained by plotting frequency versus impedance and the phase angle from the electrochemical analysis. b These graphs were collected from electrochemical impedance spectroscopy—Nyquist plot. c The resistance graph reveals a higher resistance for the control sample. d The capacitance graph reveals a higher capacitance for the control. These data support the previous finding that the challenge has been corroded more

Fig. 7

a and b The dark spots on the control sample are remnants from the Ti oxide layer. The absence of these spots on the challenge demonstrates the increased corrosion. c and d The challenged sample features minuscule holes known as pitting corrosion, further evidence of the increased corrosion of the challenged sample

Fig. 8

Schematic diagram showing the possible clinical implications of the study. Since most hip implants are made up of titanium metal, the release of its particles or ions leads to serious complications. The presence of the inflammatory condition in response to the presence of Ti ions could create conditions that adversely impact the cells exposed to them. Consequently, this could leverage the immune system response to create conditions that develop inflammation and further increase corrosion processes