Ferromagnético Bare Metal Stent para captura de células endoteliais e Retenção
Summary
Nossos objetivos foram para projetar, fabricar e testar stents ferromagnéticos para a captura de células endoteliais. Dez stents foram testados quanto à fractura e mais 10 stents foram testados para o magnetismo retida. Finalmente, 10 stents foram testados in vitro e 8 mais stents foram implantados em 4 porcos para mostrar a captura e retenção celular.
Abstract
Endotelização rápida de stents cardiovasculares é necessária para reduzir a trombose de stent e para evitar a terapia anti-plaquetas que podem reduzir o risco de sangramento. A viabilidade do uso de forças magnéticas para capturar e reter as células endoteliais excrescência (EdC) marcadas com nanopartículas de óxido de ferro super-paramagnéticas (spion) foi mostrado anteriormente. Mas esta técnica requer o desenvolvimento de um stent funcional mecanicamente a partir de um material magnético e biocompatível seguido de in-vitro e in-vivo de ensaio para comprovar rápida endotelização. Nós desenvolvemos um stent fracamente ferromagnéticos de aço inoxidável 2205 duplex utilizando desenho assistido por computador (CAD) e seu design foi aperfeiçoada por meio de análise de elementos finitos (FEA). O desenho final do stent exibiu a principal pressão abaixo do limite de fratura do material durante cravamento mecânica e expansão. Cem stents foram fabricados e um subconjunto deles foi usado para ensaios mecânicos, tempo de retained medições do campo magnético, em estudos in vitro de captura de células, in vivo e estudos de implantação. Dez stents foram testados para implantação para verificar se eles sustentado friso e expansão ciclo sem falhas. Outros 10 stents foram magnetizadas usando um ímã de neodímio forte e seu campo magnético retido foi medido. Os stents mostrou que o magnetismo retido foi suficiente para capturar spion marcado EOC nos nossos estudos in vitro. Foi verificada marcado com spion captura e retenção de EOC em grandes modelos animais através da implantação de um stent magnetizado e um stent controle não-magnetizado em cada um dos 4 porcos. As artérias stented foram explantadas após 7 dias e analisados histologicamente. Os stents fracamente magnéticos desenvolvidas neste estudo foram capazes de atrair e reter as células endoteliais marcado com spion que podem promover a cura rápida.
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
Desenvolvemos um stent magnético que pode funcionar como um stent convencional e pode atrair células endoteliais marcado com spion. Em estudos anteriores envolvendo stents magnéticas, os pesquisadores usaram níquel stents revestidos comerciais e bobinas ou malhas feitas de materiais magnéticos devido à indisponibilidade de um stent ferromagnético 5,10-14. Outros grupos também têm utilizado a natureza paramagnética de stents de aço inoxidável 304 de grau comercialmente disponíveis para o direciona…
Divulgations
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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