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Research Papers

Nanosecond Laser Induced Periodic Surface Structures on Drug Elution Profiles in Stents

[+] Author and Article Information
Michelle Buehler

Pal Molian1

Laboratory for Lasers, MEMS and Nanotechnology, Department of Mechanical Engineering,  Iowa State University, Ames, IA 50011

Restenosis is a complex biological cascade created by vessel wall stretching during angioplasty, disruption of the atherosclerotic plaque, and trauma to the vessel wall caused by the balloon and the stent struts [4].

Food and Drug Administration.

ANSI/ASME B46.1-2002, “Surface Texture (Surface Roughness, Waviness and Lay).” American Society of Mechanical Engineers.

1

Corresponding author.

J. Med. Devices 6(3), 031002 (Jul 30, 2012) (10 pages) doi:10.1115/1.4006539 History: Received March 30, 2011; Accepted March 16, 2012; Published July 30, 2012; Online July 30, 2012

Drug-eluting stents (DESs) have profoundly affected the field of interventional cardiology as a transformative technology by dramatically reducing the problem of in-stent restenosis. However, the development of adverse, late stent thrombosis (LST) raises the question of the safety profile of the DES. The aim of the study is to develop better DESs that can increase the amount of drug (sirolimus) loading while slowing down the drug release rate and potentially eliminating the polymer, all of which are expected to aid in the prevention of LST. Nanosecond pulsed laser texturing of Nitinol stent surfaces was first performed and the surface topography was analyzed using an optical profilometer. The results showed that the surface texture parameters such as surface area ratio, its roughness, volume of fluid retained per unit area, and mean valley slope suitable for drug adhesion, retention, and elution were significantly increased due to laser texturing. Subsequently, the drug elution profiles were studied for four different types of stents: laser-textured and untreated stents coated with the drug only and the drug-polymer. Laser texturing reduced the cumulative sirolimus release from 73% to 25% in drug only coated stents and from 93% to 45% in drug-polymer coated stents and showed promise for applying polymer-free drug coatings on the DES.

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Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 11

SEM images of stents coated with drug only after 7 days of in vitro drug release testing. (a),(b) Untreated stents: dissolution/diffusion of drug. (c),(d) Laser-textured stents: drug depletion by a “treelike” diffusion pattern.

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Figure 10

SEM images of stents coated with drug-polymer after 7-days of in vitro drug release testing. (a),(b) Untreated stents: bulk erosion, delamination, osmosis. (c),(d) Laser-textured stents: delamination of PLGA, drug encapsulation by the scallops.

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Figure 9

in vitro release kinetics of sirolimus for stents: (a) with the drug only coating; (b) with the drug/polymer coating (statistical analysis: *p < 0.05, **p < 0.01)

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Figure 8

(a) LC-MS/MS characterization of sirolimus; (b) HPLC detection of sirolimus

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Figure 7

Typical surface texture plots for the laser-textured stent coupon where images (b), (c), and (d) are obtained after the high pass filter is applied

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Figure 6

Typical surface texture plots for untreated stent coupon where images (b), (c), and (d) are obtained after the high pass filter is applied

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Figure 5

Ripple spacing as a function of the angle of beam incidence using Eq. 3 and experimental data

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Figure 4

SEM images of a nanosecond laser textured stent where images (b), (c), and (d) are magnified images of the noted locations in image (a)

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Figure 3

SEM images of nanosecond laser textured coupons: (a) two overlapping pulses, (b) several overlapping pulses at a speed of 1 mm/s, and (c) a closer image of (b) outside of the flat melting zone

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Figure 2

Experimental setup for nanosecond pulsed laser nanotexturing of stents

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Figure 1

(a) Part drawing of the stent used in this investigation; (b) scanning electron micrograph of the Nitinol stent fabricated from part (a)

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