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Bioelectrochemistry ; 129: 235-241, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31226524


During tribocorrosion of biomedical alloys, potentials may shift cathodically across the metal-oxide-electrolyte interface resulting in the increased reduction of local oxygen and water molecules. The products of reduction are thought to include reactive oxygen species (ROS) as well as hydroxide ions. Using fluorescent probes, developed for labeling intracellular ROS-based hydroxyl radicals (OH·) and hydrogen peroxide (H2O2), ROS generation due to reduction reactions at cathodically biased CoCrMo alloy surfaces was measured directly. Using terephthalic acid (TA) and pentafluorosulfonylbenzene-fluorescein (PFF) as fluorescent dosimeters, it was found that OH· and H2O2 concentrations increased up to 16 h and 2 h, respectively. Decreases in fluorescence past these time points were attributed to the continuous onset of reduction reactions consuming both the ROS and/or dosimeter. It was also found that voltages below and including -600 mV (vs. Ag/AgCl) produced measurable quantities of H2O2 after two hours of polarization, with concentrations increasing with decreasing potentials up to -1000 mV. The detection and quantification of ROS in a clinical setting could help us better understand the role of ROS in the inflammatory response as well as their impact on corrosion behavior of biomedical alloys.

Cromo/química , Cobalto/química , Corantes Fluorescentes/química , Peróxido de Hidrogênio/análise , Radical Hidroxila/análise , Molibdênio/química , Espécies Reativas de Oxigênio/análise , Ligas/química , Eletrodos , Fluoresceína/química , Oxirredução , Ácidos Ftálicos/química , Espectrometria de Fluorescência/métodos
J Biomed Mater Res A ; 2018 Dec 03.
Artigo em Inglês | MEDLINE | ID: mdl-30507061


Electrochemical interactions at the cell-metal interface determine cell viability and influence behavior in response to different electrode potential conditions, specifically cathodic biases. Mechanically assisted crevice corrosion, for example, induces cathodic potentials and the associated electrochemical consequences of increased reduction reactions at the implant surface may affect cell viability in a manner that is different for various cell phenotypes. Monocyte macrophage-like U937 cells were cultured on cobalt-chromium-molybdenum (CoCrMo) metal surfaces in vitro for 24 h to assess cell behavior in response to sustained applied voltages. The electrochemical zone of viability for U937 cells polarized for 24 h in vitro was -1000 ≤ mV < +500, compared to -400 < mV < +500 for MC3T3-E1 preosteoblast-like cells cultured under the same conditions, likely as a result of intrinsic apoptosis. Voltages above +250 mV had a lethal effect on U937 cells that was similar to that seen previously for MC3T3-E1 cells on biased CoCrMo surfaces. It appears that cell phenotype directly influences behavior in response to cathodic electrochemical stimuli and that the monocyte macrophage-like cells are more resistant to cathodic potential stimuli than preosteoblasts. This may be due to a glutathione-based increased ability to quench reactive oxygen species and inflammatory-associated radicals hypothesized to be generated during reduction of oxygen. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 00A: 000-000, 2018.

Artigo em Inglês | MEDLINE | ID: mdl-30184331


Two-solution bone cements modified with ethylene glycol-dimethacrylate (EG-DMA) as a crosslinker have been developed as an attempt to further improve the mechanical properties of acrylic bone cement. The result of this study shows that EG-DMA can increase the mechanical properties and fractional monomer conversion while preserving the thermal characteristics. The strength and bending modulus increase with EG-DMA concentrations at 5-10 vol % EG-DMA. Substituting the EG-DMA content past 10 vol % decreases the bending properties due to the effects of reduced monomer concentrations. Strengthened EG-DMA samples demonstrated an increase in ductility with noticeably different fracture surface morphologies than the control samples, indicated by microtroughs and ridge formation caused by excessive plastic strain. This work provides insight into the effect of substituting a crosslinker for MMA monomer in an injectable two-solution system and lays out the ideal concentrations of EG-DMA for superior mechanical or fractional monomer conversion properties. © 2018 Wiley Periodicals, Inc. J. Biomed. Mater. Res. Part B, 2018.