Biocompatible Carbon-Based Coating as Potential Endovascular Material for Stent Surface

Abstract

Stainless steel 316L is a material commonly used in cardiovascular medicine. Despite the various methods applied in stent production, the rates of in-stent restenosis and thrombosis remain high. In this study graphene was used to coat the surface of 316L substrate for enhanced bio- and hemocompatibility of the substrate. The presence of graphene layers applied to the substrate was investigated using cutting-edge imaging technology: energy-filtered low-voltage FE-SEM approach, scanning electron microscopy (SEM), Raman spectroscopy, and atomic force microscopy (AFM). The potential of G-316L surface to influence endothelial cells phenotype and endothelial-to-mesenchymal transition (EndoMT) has been determined. Our results show that the bio- and hemocompatible properties of graphene coatings along with known radial force of 316L make G-316L a promising candidate for intracoronary implants.

Figure 1

Raman spectrum of the graphene layer on stainless steel substrate (G-316-L).

Figure 2

SEM images of the stainless steel surface: after mechanical polishing (a); after successful graphene transfer (b); AFM images of graphene coated steel (G-316-L): height image (c) and phase image (d). Figures 2(c) and 2(d) present AFM images of steel surface coated with graphene. The surface roughness was investigated and the surface profile in the selected cross-section and the average analyzed height of the film were determined.

Figure 3

Low-voltage FE-SEM field-emission scanning electron microscopy with energy filtering. Graphene layers visualized ((a) and (b)) versus uncoated steel ((c) and (d)) discs. Detectors used: In-Lens SE1 detector ((a) and (c)); EsB energy-filtered backscattered electrons detector ((b) and (d)). Incident beam acceleration voltage 800 V used throughout the imaging, retarding potential of EsB detector grid set at 760 V (40 eV filtering energy difference).

Figure 4

An adhesion of endothelial cells on graphene coated discs (G-316L). Cell number on G-316L was normalized to cell number on still substrate (316L) which served as a control (a). Fluorescent stained endothelial cells on steel (left) and graphene discs (right) (b); blue-nuclei; red-cytoplasm; n=6 per group, mean±SD.

Figure 5

The comparison of cells proliferation on steel (316L) and graphene (G-316L) discs. Cell proliferation was assessed by the measurement of total biomass absorbance after 24 and 72 hours of cultivation; n=6 per group, mean±SD.

Figure 6

The assessment of cytotoxic effect of graphene (G-316L) on endothelial cells in comparison to steel (316L) during 24 and 72 hours of cultivation; n=6 per group, mean±SD.

Figure 7

Metabolic activity of endothelial cells cultivated on graphene (G-316L) and steel (316L) discs; n=6 per group, mean±SD.

Figure 8

Endothelial-to-mesenchymal transition on graphene (G-316L) coated in comparison to steel (316L) discs; n=6 per group, mean±SD.

Figure 9

Platelets attachment (adhesion) (a) and mean platelets surface area (b) on steel (316L) and graphene (G-316L) coated discs. A representative fluorescence images of platelets are shown in upper part of the figures; n=6 per group, mean±SD.