Published: March 1st, 2013
Graphene offers potential as a coating material for biomedical implants. In this study we demonstrate a method for coating nitinol alloys with nanometer thick layers of graphene and determine how graphene may influence implant response.
Atomically smooth graphene as a surface coating has potential to improve implant properties. This demonstrates a method for coating nitinol alloys with nanometer thick layers of graphene for applications as a stent material. Graphene was grown on copper substrates via chemical vapor deposition and then transferred onto nitinol substrates. In order to understand how the graphene coating could change biological response, cell viability of rat aortic endothelial cells and rat aortic smooth muscle cells was investigated. Moreover, the effect of graphene-coatings on cell adhesion and morphology was examined with fluorescent confocal microscopy. Cells were stained for actin and nuclei, and there were noticeable differences between pristine nitinol samples compared to graphene-coated samples. Total actin expression from rat aortic smooth muscle cells was found using western blot. Protein adsorption characteristics, an indicator for potential thrombogenicity, were determined for serum albumin and fibrinogen with gel electrophoresis. Moreover, the transfer of charge from fibrinogen to substrate was deduced using Raman spectroscopy. It was found that graphene coating on nitinol substrates met the functional requirements for a stent material and improved the biological response compared to uncoated nitinol. Thus, graphene-coated nitinol is a viable candidate for a stent material.
The past three decades have witnessed discovery of novel materials-based therapies and devices for disease treatments and diagnostics. Novel alloy materials such as nitinol (NiTi) and stainless steel are often used in biomedical implant manufacturing due to their superior mechanical properties.1-3 However, numerous challenges remain due to exogenous material cytotoxicity, bio- and hemo-compatibility. The metallic nature of these alloys results in poor bio- and hemocompatibility due to metal leaching, lack of cell adhesion, proliferation, and thrombosis when it comes in contact with flowing blood (such as catheters, blood vessel grafts, vascular ste....
1. Graphene-coating of NiTi
Figure 1. a) CVD grown polycrystalline graphene on Cu foils mimics the metal crystal grains (scale bar: 10 μm). b) Raman spectrum of 1 sccm (4 sccm) graphene shows intense (relatively weaker) G' band indicating monolayer (few layer) nature of as-prepared graphene. c) AFM image of graphene transferred on to NiTi shows a roughness of ~5 nm. Scale bar = 500 nm.
Biocompatibility and cytotoxicity: The chemical vapor deposition (CVD) method yielded polycrystalline graphene samples that mimicked Cu crystal grains, as shown in Figure 1a. We employed Raman spectroscopy to confirm the presence of monolayer (few layer) graphene on 1 sccm (4 sccm) samples (see Figure 1b). Clearly, 1 sccm (4 sccm) samples exhibit intense (relatively weaker) G' band indicative of monolayer (few layer) graphene. Figure 1c shows an atomic forc.......
|Dulbecco's Modified Eagle Medium
|Thiazolyl blue tetrazolium bromide
|CellTiter 96 Aqueous One solution cell proliferation assay (MTS)
|Alexafluor 488 phalloidin
|VECTASHIELD mounting medium with DAPI
|Human serum albumin
|Ready Gel Tris-HCl Gel
|Protein low BCA assay
|Precision Plus Protein Kaleidoscope Standard
|Immun-Blot PVDF membrane
|Blotting grade blocker non-fat dry milk
|Anti-actin antibody produced in rabbit
|BM Chemiluminescence Western Blotting kit (mouse/rabbit)
|Roche Applied Science
|NiTi (51% Ni, 49% Ti)
|Dilor XY 98
|Eclipse TI microscope
|PowerPac basic power supply
|Mini-PROTEAN tetra cell
|Gel holder cassette
|Mini gel holder cassette
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