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Dominant role of molybdenum in the electrochemical deposition of biological macromolecules on metallic surfaces.

Martin EJ, Pourzal R, Mathew MT, Shull KR - Langmuir (2013)

Bottom Line: Corrosion studies on pure Co, Cr, and Mo in protein solutions found material deposition only on Mo.We hypothesize that organic deposition results from the interaction of Mo(VI) with proteins in the surrounding solution.The organic layer is reminiscent of tribochemical reaction layers that form on the surface of CoCrMo hip bearings, suggesting that these types of layers can be formed by purely electrochemical means.

View Article: PubMed Central - PubMed

Affiliation: Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States.

ABSTRACT
The corrosion of CoCrMo, an alloy frequently used in orthopedic implants, was studied with an electrochemical quartz crystal microbalance (QCM) in three physiologically relevant solutions. Mass changes were measured during potentiodynamic tests, showing material deposition in protein solutions at potential levels that caused mass loss when the proteins were not present. X-ray photoelectron spectroscopy (XPS) data indicated that the deposited material was primarily organic and therefore was most likely derived from proteins in the electrolyte. Material deposition consistently occurred at a critical potential and was not dependent on the current density or total charge released into solution. Corrosion studies on pure Co, Cr, and Mo in protein solutions found material deposition only on Mo. We hypothesize that organic deposition results from the interaction of Mo(VI) with proteins in the surrounding solution. The organic layer is reminiscent of tribochemical reaction layers that form on the surface of CoCrMo hip bearings, suggesting that these types of layers can be formed by purely electrochemical means.

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Change in mass as a function of charge released duringpotentiodynamicscans in BCS on (a) Co, (b) Cr, and (c) Mo thin films.
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fig10: Change in mass as a function of charge released duringpotentiodynamicscans in BCS on (a) Co, (b) Cr, and (c) Mo thin films.

Mentions: Potentiodynamictests were also conducted on the pure alloying elements in BCS todetermine if a particular ion is responsible for mass deposition onthe alloy. Mass changes with potential variation are shown for eachmetal in Figure 9. Cobalt specimens (Figure 9a) monotonically lost mass as the potential increased.Mass loss began near −0.48 V as the current reached a plateau.The mqeff (Figure 10a)averaged 29.3 ± 4.2 g/equiv, approximately corresponding to theCo(II) oxidation state as expected. Chromium specimens (Figure 9b) gained approximately 3.7 mg/m2 massat 0.38 V but continuously lost mass beginning at 0.5 V. The massgain at 0.38 V is 1 to 2 orders of magnitude smaller than on the alloyand corresponds to a stabilization in the current. Hence, it is likelyattributed to an enhancement in the oxide thickness on the chromiumsurface. The initial value of mqeff (Figure 10b) was approximately 9 g/equiv, nearly correspondingto the dissolution of Cr(VI) ions, but decreased to 6.7 g/equiv above0.85 V.


Dominant role of molybdenum in the electrochemical deposition of biological macromolecules on metallic surfaces.

Martin EJ, Pourzal R, Mathew MT, Shull KR - Langmuir (2013)

Change in mass as a function of charge released duringpotentiodynamicscans in BCS on (a) Co, (b) Cr, and (c) Mo thin films.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4067157&req=5

fig10: Change in mass as a function of charge released duringpotentiodynamicscans in BCS on (a) Co, (b) Cr, and (c) Mo thin films.
Mentions: Potentiodynamictests were also conducted on the pure alloying elements in BCS todetermine if a particular ion is responsible for mass deposition onthe alloy. Mass changes with potential variation are shown for eachmetal in Figure 9. Cobalt specimens (Figure 9a) monotonically lost mass as the potential increased.Mass loss began near −0.48 V as the current reached a plateau.The mqeff (Figure 10a)averaged 29.3 ± 4.2 g/equiv, approximately corresponding to theCo(II) oxidation state as expected. Chromium specimens (Figure 9b) gained approximately 3.7 mg/m2 massat 0.38 V but continuously lost mass beginning at 0.5 V. The massgain at 0.38 V is 1 to 2 orders of magnitude smaller than on the alloyand corresponds to a stabilization in the current. Hence, it is likelyattributed to an enhancement in the oxide thickness on the chromiumsurface. The initial value of mqeff (Figure 10b) was approximately 9 g/equiv, nearly correspondingto the dissolution of Cr(VI) ions, but decreased to 6.7 g/equiv above0.85 V.

Bottom Line: Corrosion studies on pure Co, Cr, and Mo in protein solutions found material deposition only on Mo.We hypothesize that organic deposition results from the interaction of Mo(VI) with proteins in the surrounding solution.The organic layer is reminiscent of tribochemical reaction layers that form on the surface of CoCrMo hip bearings, suggesting that these types of layers can be formed by purely electrochemical means.

View Article: PubMed Central - PubMed

Affiliation: Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States.

ABSTRACT
The corrosion of CoCrMo, an alloy frequently used in orthopedic implants, was studied with an electrochemical quartz crystal microbalance (QCM) in three physiologically relevant solutions. Mass changes were measured during potentiodynamic tests, showing material deposition in protein solutions at potential levels that caused mass loss when the proteins were not present. X-ray photoelectron spectroscopy (XPS) data indicated that the deposited material was primarily organic and therefore was most likely derived from proteins in the electrolyte. Material deposition consistently occurred at a critical potential and was not dependent on the current density or total charge released into solution. Corrosion studies on pure Co, Cr, and Mo in protein solutions found material deposition only on Mo. We hypothesize that organic deposition results from the interaction of Mo(VI) with proteins in the surrounding solution. The organic layer is reminiscent of tribochemical reaction layers that form on the surface of CoCrMo hip bearings, suggesting that these types of layers can be formed by purely electrochemical means.

Show MeSH
Related in: MedlinePlus