Abstract
In this study, the authors tested the hypotheses that plasma electrolytic oxidation (PEO) and glow-discharge plasma (GDP) would improve the electrochemical, physical, chemical, and mechanical properties of commercially pure titanium (cpTi), and that blood protein adsorption on plasma-treated surfaces would increase. Machined and sandblasted surfaces were used as controls. Standard electrochemical tests were conducted in artificial saliva (pHs of 3.0, 6.5, and 9.0) and simulated body fluid. Surfaces were characterized by scanning electron microscopy, energy-dispersive spectroscopy, x-ray photoelectron spectroscopy, atomic force microscopy, x-ray diffraction, profilometry, Vickers microhardness, and surface energy. For biological assay, the adsorption of blood serum proteins (i.e., albumin, fibrinogen, and fibronectin) was tested. Higher values of polarization resistance and lower values of capacitance were noted for the PEO and GDP groups (p < 0.05). Acidic artificial saliva reduced the corrosion resistance of cpTi (p < 0.05). PEO and GDP treatments improved the surface properties by enrichment of the surface chemistry with bioactive elements and increased surface energy. PEO produced a porous oxide layer (5-μm thickness), while GDP created a very thin oxide layer (0.76-μm thickness). For the PEO group, the authors noted rutile and anatase crystalline structures that may be responsible for the corrosion barrier improvement and increased microhardness values. Plasma treatments were able to enhance the surface properties and electrochemical stability of titanium, while increasing protein adsorption levels.
Highlights
Laccases (EC 1.10.3.2) are enzymes that belong to the group of polyphenol oxidases and catalyze the oxidation of various organic substances, typically phenolic compounds, with the simultaneous reduction of oxygen to water through a radical-catalyzed reaction mechanism (Baldrian, 2006)
We evaluated the fungus capacities to produce laccases in a Stirred Tank (ST) and Airlift (AL) bioreactors
Flask scale experiments indicated that fungus Peniophora sp
Summary
Laccases (EC 1.10.3.2) are enzymes that belong to the group of polyphenol oxidases and catalyze the oxidation of various organic substances, typically phenolic compounds, with the simultaneous reduction of oxygen to water through a radical-catalyzed reaction mechanism (Baldrian, 2006). Laccases can be found in many different species of organisms, like plants, fungi, prokaryotes, and insects (Yoshida, 1883; Claus, 2004; Dwivedi et al, 2011). They are referred as “moonlight” enzymes due to their multiple physiologic functions, which includes vegetal lignification and delignification, wound healing, pigment synthesis, anti-stress regulation, and fungal morphogenesis (Sharma and Kuhad, 2008). The mediators act as electron “shuttle” between the enzyme and the substrate, enabling the oxidization of complex substrates that could not be oxidized by the enzyme itself (Kunamneni et al, 2008; Can~as and Camarero, 2010). Laccases are used in the formulation of biofuels and biosensors, medical analyses, and synthesis of new hybrid molecules (Mikolasch and Schauer, 2009; Senthivelan et al, 2016)
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