The interfacial gelation of proteins at metallic surfaces was investigated with an electrochemical quartz crystal microbalance (QCM). When Cr electrodes were corroded in proteinaceous solutions, it was found that gels will form at the Cr surfaces if molybdate ions are also present in the solution. Gelation is reversible and can also be controlled with the electrochemical potential at the electrode. Further, a method was developed to characterize the viscoelastic properties of thin films in liquid media using the QCM as a high-frequency rheometer. By measuring the frequency and dissipation at multiple harmonics of the resonance frequency, the viscoelastic phase angle, density-modulus product, and areal mass of a film can be determined. The method was applied to characterize the protein films, demonstrating that they have a phase angle near 55° and a density-modulus product of ≈10(7) Pa·g/cm(3). Data imply that the gels are composed of a weakly cross-linked proteinaceous network with properties similar to albumin solutions with concentrations in the range of ≈40 wt %.

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.

A UCST polymer functionalized graphene oxide as a thermally responsive ion permeable membrane.

No abstract