Vores mål var at designe, fremstille og teste ferromagnetiske stenter til endotelceller fange. Ti stenter blev testet for brud og endnu 10 stenter blev testet for tilbageholdt magnetisme. Endelig blev 10 stenter testet in vitro og 8 mere stenter blev implanteret i 4 grise til at vise celle opsamling og fastholdelse.
Rapid endotelialisering af kardiovaskulære stents er nødvendig for at reducere stenttrombose og undgå trombocythæmmende behandling, som kan reducere risikoen for blødning. Muligheden for at anvende magnetiske kræfter til at indfange og fastholde endothelial udvækst celler (EOC) mærket med super paramagnetiske jernoxid nanopartikler (Spion) er blevet vist tidligere. Men denne teknik kræver udvikling af en mekanisk funktionel stent fra et magnetisk og biokompatibelt materiale efterfulgt af in-vitro og in vivo-forsøg for at bevise hurtig endotelialisering. Vi udviklede en svagt ferromagnetisk stent fra 2205 duplex rustfrit stål ved hjælp af computer aided design (CAD) og dens design blev yderligere raffineret under anvendelse af finite element analyse (FEA). Den endelige udformning af stenten udviste en hovedtøjningen under bruddet grænsen af materialet under mekanisk krympning og ekspansion. Et hundrede stenter blev fremstillet og en delmængde af dem blev anvendt til mekanisk afprøvning, RETained magnetiske målinger, in vitro-celle capture studier og in vivo implantering studier. Ti stenter blev testet for implementering for at kontrollere, om de vedvarende krympning og ekspansion cyklus uden fejl. Yderligere 10 stenter blev magnetiseret ved hjælp af en stærk neodym magnet og deres bevaret magnetfelt blev målt. Stenterne viste, at den tilbageholdte magnetisme var tilstrækkelig til at indfange Spion-mærket EOC i vores in-vitro-studier. Spion-mærket EOC fangst og opbevaring blev verificeret i store dyremodeller ved at implantere en magnetiseret stent og 1 ikke-magnetiseret kontrol stent i hver af 4 grise. De stentede arterier blev eksplanteret efter 7 dage og analyseret histologisk. De svagt magnetiske stenter udviklet i dette studie var i stand til at tiltrække og fastholde Spion-mærkede endotelceller, som kan fremme hurtig heling.
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.
Vi udviklede en magnetisk stent, som kan fungere som et bart metal stent og kan tiltrække Spion-mærkede endotelceller. I tidligere undersøgelser med magnetiske stenter har forskere brugt nikkel belagte kommercielle stenter og spoler eller masker lavet af magnetiske materialer på grund af manglende adgang til en ferromagnetisk stent 5,10-14. Andre grupper har også brugt den paramagnetiske karakter af kommercielt tilgængelige 304-grade rustfrit stål stents til målretning nanopartikler indlæst endotelce…
The authors have nothing to disclose.
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.
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 |