Ferromagnétique Bare Metal Stent pour endothéliale capture de cellules et de la conservation
Summary
Nos objectifs étaient de concevoir, fabriquer et tester stents ferromagnétiques pour la capture des cellules endothéliales. Dix stents ont été testés pour la fracture et 10 autres stents ont été testés pour le magnétisme retenu. Enfin, 10 stents ont été testés in vitro et 8 autres stents ont été implantés dans 4 porcs pour montrer capture et la conservation cellule.
Abstract
Endothélialisation rapide des endoprothèses vasculaires est nécessaire pour réduire la thrombose de stent et d'éviter la thérapie anti-plaquettaire qui peut réduire le risque de saignement. La faisabilité de l'utilisation des forces magnétiques pour capturer et conserver les cellules endothéliales excroissance (COE) marqués avec des nanoparticules d'oxyde de fer super-paramagnétiques (SPION) a été montré précédemment. Mais cette technique nécessite la mise au point d'un stent mécaniquement fonctionnelle à partir d'un matériau magnétique et biocompatible suivi par in-vitro et in-vivo des tests pour prouver endothélialisation rapide. Nous avons développé un stent faiblement ferromagnétique acier inoxydable duplex 2205 en utilisant conception assistée par ordinateur (CAD) et sa conception a été affinée en utilisant une analyse par éléments finis (FEA). La conception finale du stent présenté une déformation principale sous la limite de rupture du matériau pendant le sertissage mécanique et d'expansion. Une centaine de stents ont été fabriqués et un sous-ensemble d'entre eux a été utilisé pour les essais mécaniques, retained mesures de champ magnétique, des études in vitro de capture de cellules, in vivo et des études d'implantation. Dix stents ont été testés pour déploiement pour vérifier si elles soutenue sertissage et l'expansion du cycle sans défaillance. 10 autres ont été magnétisés stents utilisant un aimant de néodyme forte et leur champ magnétique retenu a été mesurée. Les stents ont montré que le magnétisme retenu était suffisante pour capturer SPION marqué EOC dans nos études de in vitro. Capture et la conservation des COE SPION marqué a été vérifiée dans les grands modèles animaux par l'implantation d'une endoprothèse magnétisé et 1 non-aimanté stent de contrôle dans chacun des 4 porcs. Les artères ont été explantées stentées après 7 jours et analysés histologiquement. Les stents faiblement magnétiques développés dans cette étude étaient capables d'attirer et de retenir les cellules endothéliales Spion marqué qui peut favoriser la guérison rapide.
Introduction
Patients implanted with vascular stents manufactured from thrombogenic materials like stainless steel, cobalt chromium, and platinum chromium – both bare metal stents (BMS) and drug eluting stents (DES) – need anti-platelet therapy to prevent thrombus formation. BMS heal rapidly, but are subject to late stage restenosis due to incomplete healing. DES require long term anti-platelet therapy due to delayed healing. Anti-platelet therapy administered to avoid thrombosis as a result of incomplete or delayed healing leads to increased bleeding risk and may not be suitable for certain patients1,2. An ideal stent will heal completely and quickly thus avoiding long-term anti-platelet therapy and late stage restenosis. This complete healing can only be achieved if the stent is rapidly coated with a monolayer of endothelial cells after implantation. Coating the stents with biocompatible materials such as gold or other biopolymers has been shown to improve thrombo-resistance, but none of these techniques achieved ideal blood compatibility as may be possible by coating with endothelial cells3,4.
A stent can be coated with endothelial cells post implantation by attracting circulating progenitor cells. This self-seeding technique can be achieved by utilizing ligands and antibodies. But this technique is limited by the low number of circulating endothelial progenitor cells. A promising strategy is to deliver cells directly to the stent immediately following implantation during a short period of blood flow occlusion3,5. This strategy requires a technique for rapidly capturing cells and retaining them on the stent even after restoring blood flow. We have developed a technique in which a magnetic stent is used to attract and retain magnetically-labeled endothelial cells delivered post implantation. To achieve this, a functional BMS with sufficient magnetic properties to capture and retain magnetically-labeled endothelial cells is required6.
In this paper, we discuss the methods for designing, manufacturing, and testing a 2205 stainless steel stent. The stents were designed using CAD and FEA. The manufactured stents were magnetized using a neodymium magnet and the retained magnetic field was measured using a magneto-resistance microsensor probe. We then tested the stents for magnetically-labeled cell capture in a culture dish during our in-vitro experiments. Finally, the stents were tested in-vivo by implanting magnetic and non-magnetic stents in 4 pigs and histologically analyzing the stented arteries.
Protocol
Representative Results
Discussion
Nous avons développé un stent magnétique qui peut fonctionner comme un stent en métal nu et peut attirer les cellules endothéliales Spion marqué. Dans des études précédentes impliquant des stents magnétiques, les chercheurs ont utilisé nickel stents actifs commerciaux et des bobines ou des mailles en matériaux magnétiques en raison de l'indisponibilité d'un stent ferromagnétique 5,10-14. D'autres groupes ont également utilisé la nature paramagnétique disponibles dans le commerce …
Disclosures
The authors have nothing to disclose.
Acknowledgements
The authors thank Tyra Witt, Cheri Mueske, Brant Newman and Dr. Peter J. Psaltis, MBBS, PhD for their valuable contributions. This study was financially supported by European Regional Development Fund – FNUSA-ICRC (No. CZ.1.05/1.100/02.0123), American Heart Association Scientist Development Grant (AHA #06-35185N), National Institutes of Health (T32HL007111) and The Grainger Innovation Fund – Grainger Foundation.
Materials
| 2205 Stainless steel | Carpenter Technology Corporation | N/A | Round bar stock material |
| Abaqus | Dassault systems | N/A | Software |
| Atropine | Prescription drug. | ||
| Clopidogrel | Commercial name: Plavix. Prescription drug. | ||
| CM-DiI | Life Technologies | V-22888 | Molecular Probes, Eugene, OR |
| Endothelial growth medium-2 | Lonza | CC-3162 | |
| Hand Held Crimping tool | Blockwise engineering | M1-RMC | |
| Hydrochloric acid (HCl) | Sigma Aldrich | MFCD00011324 | CAUTION: wear proptective equipment and handle under fume hood |
| Isoflurane anesthesia | Piramal Critical Care, Inc. | ||
| Isopropyl alcohol | Sigma Aldrich | MFCD00011674 | |
| NdFeB magnet 2" Dia x 1" thick | Amazing magnets | D1000P | Axially magnetized disc magnet with poles on flat faces |
| Over-The-Wire trifold balloon | N/A | N/A | Any commercially available OTW trifold balloon can be used |
| Phosphate buffered saline | Life Technologies | 10010-023 | Commonly known as PBS |
| Sodium Bicarbonate (NaHCO3) | Sigma Aldrich | MFCD00003528 | |
| Sodium pentobarbital | Zoetis | Commercial Name: Sleepaway (26%), FatalPlus, Beuthanasi. Controlled substance to be ordered only by licensed veternarian | |
| SolidWorks | Dassault systems | N/A | Software |
| SpinTJ-020 micro sensor | MicroMagneitcs Sensible Solutions | N/A | Long probe STJ-020 microsensor |
| SPION | Mayo Clinic | N/A | Nanoparticles synthesized internally (Ref: Lee, S. J. et al. Nanoparticles of magnetic ferric oxides encapsulated with poly(D,L latide-co-glycolide) and their applications to magnetic resonance imaging contrast agent. J Magn Magn Mater 272, 2432-2433, doi:DOI 10.1016/j.jmmm.2003.12.416 (2004)) |
| Telazol | Zoetis | Controlled substance to be ordered only by licensed veternarian | |
| Trypsin EDTA | Life Technologies | 25200-056 | Gibco, Grand Island, NY |
| Xylazine | Bayer Animal Health | Commercial name: Rompun. Controlled sunstance to be ordered only by a licensed veternarian |
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