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Bioengineering

Graphene Coatings for Biomedical Implants

Published: March 1st, 2013

DOI:

10.3791/50276

1Department of Physics, Clemson University, 2Department of Pharmacology and Toxicology, East Carolina University, 3Department of Bioengineering, Clemson University, 4Center for Optical Materials Science and Engineering Technologies, Clemson University

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....

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1. Graphene-coating of NiTi

  1. The graphene samples used in this study were grown on copper (Cu) substrates using the chemical vapor deposition technique, and subsequently transferred to 4.5 mm2NiTi substrates.
  2. Cu foils (1 cm x 1 cm) were placed in a 1 in. quartz tube furnace and heated to 1,000 °C in the presence of 50 sccm of H2 and 450 sccm of Ar.
  3. Next, methane (1 and 4 sccm) was introduced into the furnace at different flow rates for 20-30 min. Th.......

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Figure 1
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.

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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.......

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Name Company Catalog Number Comments
Reagent
Dulbecco's Modified Eagle Medium ATCC 30-2002
Thiazolyl blue tetrazolium bromide Sigma-Aldrich M2128
CellTiter 96 Aqueous One solution cell proliferation assay (MTS) Promega G3582
Dimethyl sulfoxide Sigma-Aldrich D8418
36.5% formaldehyde Sigma-Aldrich F8775
Triton X-100 Sigma-Aldrich T8787
Alexafluor 488 phalloidin Life Technologies A12379
VECTASHIELD mounting medium with DAPI Vector Laboratories H-1200
Human serum albumin Sigma-Aldrich A9511
Human fibrinogen
Tris/Glycine/SDS Bio-Rad 161-0732
Ready Gel Tris-HCl Gel Bio-Rad 161-1158
Acetic acid Sigma-Aldrich 45726
SYPRO Red Life Technologies S-6653
Protein low BCA assay Lamda Biotech G1003
Precision Plus Protein Kaleidoscope Standard Bio-Rad 161-0375
Immun-Blot PVDF membrane Bio-Rad 162-0177
Blotting grade blocker non-fat dry milk Bio-Rad 170-6404XTU
Anti-actin antibody produced in rabbit Sigma-Aldrich A2066
BM Chemiluminescence Western Blotting kit (mouse/rabbit) Roche Applied Science 11520709001
RIPA buffer Sigma-Aldrich R0278
NiTi (51% Ni, 49% Ti) Alfa-Aesar 44953
Equipment
Horiba JobinYvon Raman spectrometer Dilor XY 98
Nikon Confocal microscope Eclipse TI microscope
Thermoscientific Plate reader
Bio-Rad Power supply 164-5050 PowerPac basic power supply
Bio-Rad Electrophoresis cell 165-8004 Mini-PROTEAN tetra cell
Bio-Rad Gel holder cassette 170-3931 Mini gel holder cassette

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