טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentMeital Alagem
SubjectConverging Technologies as the Interface between Natural
and Artificial Biosystem: Biologically Active
Implants
DepartmentDepartment of Biomedical Engineering
Supervisors Professor Emeritus Lotan Noah
Full Professor Beyar Rafael
Full Thesis textFull thesis text - English Version


Abstract

Coronary artery diseases are life-threatening. Currently, stent implantation is one of the main procedures for treating these disease states.   Yet, this particular procedure is associated with undesired effects, such as restenosis and late-stent thrombosis.  In this study, efforts have been made towards limiting or even preventing these detrimental effects. To this aim, we rely on our previously developed concept of Drug Factory on Stent (US Patent 6,569,688), in which an appropriately chosen enzyme, Nitric Oxide Synthase (NOS),  is immobilized on the device, where it locally converts a prodrug (L-Arginine) into the active drug entity, nitric oxide (NO). The involvement of NO in regulating hemostasis has motivated many researchers to develop hemocompatible surfaces for blood contacting devices by coating these devices with NO-releasing materials.  However, despite the enhanced blood compatibility proven so far, the limited reservoir capacity of such NO donors and the resulting limited duration of NO production restricts their potential use in long-term biomedical applications. In the present study NOS was immobilized on the surface of 316L stainless steel (StSt), using either chemical or electrochemical/chemical hybrid procedures. The thus immobilized NOS ( ImNOS ) successfully released NO for a period of at least seven months and four months after being stored at 4ºC and 37ºC, respectively. The NO released by NOS-coated 316L StSt was found to promote the desired adhesion and proliferation of ECs when compared to such processes occurring on bare StSt or to fibronectin-coated StSt.  In contrast, the undesired adhesion and proliferation of SMCs on NOS-coated 316L StSt was significantly inhibited when compared to the pertinent controls.  Moreover, and in order to also assess the potential of ImNOS to prevent thrombosis, the effect of NO release was also investigated regarding platelet adhesion.   We have found that only a negligible number of platelets adhered to the StSt surfaces coated with immobilized NOS, when compared to the related characteristics of bare and fibronectin-coated StSt.  This study demonstrates the ability of immobilized NOS to favorably act in a series of in vitro cellular pathways towards the inhibition of restenosis and thrombosis. Also, the Drug Factory on Stent approach is a promising strategy for producing hemocompatible surfaces. Hence, the results obtained in this study offer a technological platform which is general and versatile and may be conveniently adapted for many other therapeutic modalities.