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Research Papers

Optimization of Plasma Treatment, Manipulative Variables and Coating Composition for the Controlled Filling and Coating of a Microstructured Reservoir Stent

[+] Author and Article Information
Mustapha Mekki

 Hexacath, 92508 Paris, France

Stéphane Durual, Susanne S. Scherrer

Laboratory of Biomaterials, University of Geneva, 19 rue Barthélemy-Menn, 1205 Geneva, Switzerland

Johannes Lammers

1006 Lausanne, Switzerland

H. W. Anselm Wiskott1

Laboratory of Biomaterials, School of Dentistry, University of Geneva, 19 rue Barthélemy-Menn, 1205 Geneva, Switzerlandanselm@wiskott.com

1

Corresponding author.

J. Med. Devices 3(1), 011005 (Mar 09, 2009) (7 pages) doi:10.1115/1.3081394 History: Received October 31, 2008; Revised December 18, 2008; Published March 09, 2009

The object of the study was to fill and coat the microcavities of a drug eluting stent using a batch dipping process. 316L coronary stents, which were coated with a 0.25μm layer of TiNOx were used as substrates. The stents’ surface was dimpled with 0.21μl microcavities separated by distances of 1728μm depending on location. The experiment consisted of (1) optimizing the procedures to fill the microcavities with a solution of therapeutic agent and (2) covering the filled microcavities with a protective “lid” that shielded the solution during stent insertion in the arteries and then controlled its release into the surrounding tissue. The filling solution was a water-propanol mix containing 20% L-arginine. The coating solution was comprised of poly-ethylene-glycol (PEG-8000) and dexamethasone. The filling quality was investigated after altering the following variables: plasma surface activation (type of gas, pressure, power, and duration), water-propanol percentage ratio of the filling solution, lifting speed from the bath, and effect of ultrasonic vibration (monofrequency versus multifrequency). The surface coating was evaluated by altering the PEG-8000-dexamethasone percentage ratio and recording the effects on coating thickness and structure, on elution rate, and on wear resistance. The optimized process is presented in detail.

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

Stent specifications (in millimeters)

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Figure 2

Stent configuration

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Figure 3

Four echelon scale used to classify the quality of the filling into none, poor, fair, and optimal. Note that the difference between fair and optimal was established on the basis of the homogenous blending of the solution with the microcavity, not in consideration of the amount of solution.

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Figure 4

Structural formulas of poly(ethylene glycol) and dexamethasone

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Figure 5

Film thickness and film mass as a function of wt % dexamethasone in the dry film

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Figure 6

Zones labeled glass side: surface sprayed with 100% PEG-0% dexamethasone (a) and 30% PEG-70% dexamethasone (b). Note the granular appearance in (b). The zone labeled “textured background” serves as orientation reference.

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Figure 7

Degradation of the retentive coating as a function of composition

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Figure 8

Percent arginine release as a function of retentive coating composition

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Figure 9

Stent before (a) and after (b) being moved through the guide catheter

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