Corrosion Resistance of Graphene oxide/Silver Coatings on Ni–Ti alloy and Expression of IL-6 and IL-8 in Human Oral Fibroblasts

Abstract

Graphene based materials (GBMs) have potentials for dental and medical applications. GBMs may cause changes in the levels of cytokine released in the body. this study aimed to study the corrosion resistance of graphene oxide (Go) and Go/silver (Go/Ag) nanocomposite coated nickel-titanium (niti) alloy by electrophoretic deposition and to access the viability of human pulp fibroblasts, and the interleukin (IL)-6 and IL-8 expression level. The bare and coated NiTi samples were characterized by scanning electron microscope (SeM), energy-dispersive X-ray spectroscopy (eDS), Raman spectroscopy, surface profilometry, and X-ray diffraction (XRD). The corrosion resistance of the bare NiTi and coated NiTi samples were investigated by potentiodynamic polarization and electrochemical impedance spectroscopy in 3.5% NaCl solution. The cell viability of human pulp fibroblasts was accessed by the treated culture medium of the bare NiTi and coated NiTi alloys containing 1% fetal bovine serum. IL-6 and IL-8 expression levels were studied by human enzyme-linked immunosorbent assay (ELISA). Data were analyzed using One-way ANOVA (α = 0.05). Both the GO-coated NiTi and GO/Ag-coated NiTi alloys showed better corrosion resistance, a lower rate of corrosion, and higher protection efficiency than the bare NiTi alloy. The coated NiTi alloys were biocompatible to human pulp fibroblasts and showed upregulation of IL-6 and IL-8 levels. Nickel-titanium (NiTi) alloy is widely used due to the special properties of superelasticity and shape memory. Common biomedical applications of NiTi alloys include vascular stents, staples, catheter guide wires, orthodontic wires, and endodontic instruments. However, NiTi alloy exhibits corrosion attack compared to stainless steel, cobalt-chrome, or β-titanium and it results in Ni and Ti ions release. It was found that a significant release of Ni and Ti ions from dental alloys in corrosive environment is noted although the amount of Ni ions release diminish with time 1. Another study found that Ni leaching occurred after placement of the NiTi orthodontic archwires, bands and brackets and was associated with an increase of the Ni ion concentration in the patient's saliva which lasted for 10 weeks and then decreased slowly 2. These ions can cause foreign body reactions, allergy, and adverse reactions in the human body, such as stomatitis, burning sensation, angular cheilitis, and loss of taste 3,4. Similarly, Ni along with Co and Cr remains the most common metals associated with surgical implant failure due to metal sensitization 5. Therefore, the surface modifications and/or coatings have an important role in surface improvement and reducing the corrosion and body reactions. Although various polymer coatings have been tried on NiTi alloy, there has always difficult in making a successful coatings 6,7. Graphene is a sheet of sp 2 carbon atoms that creates a 2-D hexagonal honeycomb structure 8. Graphene based materials (GBMs) have been used for fabricating various nanocomposite coatings to improve surface and me...

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