Covalent attachment of fibronectin to 316L stainless steel using amine and carboxylic acid alkanethiol self-assembled monolayers: Applications for coronary artery stents

Background. Metallic stent implantation is currently the minimally invasive procedure of choice for the treatment of blocked coronary arteries. However, stent implantation can cause vascular trauma and denude a monolayer of cells from the vascular wall called the endothelium. This event initiates an exaggerated response to injury whereby smooth muscle cells (SMC) proliferate inward causing re-closure of the artery in a process known as in-stent restenosis.;Results. A novel electrochemical method for monolayer self-assembly was developed in this work. Alkanethiol SAMs of carbon length 10 with NH2, COOH, and CH3 surface exposed functionality were attached to 316L stainless steel, which is the major stent material. The SAMs were reasonably ordered, demonstrated desired surface chemistry and were stable after rigorous rinsing and sonication tests validating their robustness for use in biomedical applications. FN was covalently attached to SAMs in two ways (1) to NH2-terminated SAMs via glutaraldehyde and (2) to COOH-terminated SAMs through n-hydroxysuccinimide (NHS) and 1-ethyl-3-{3dimethyl aminopropyl} carbodiimide (EDC). FN demonstrated stronger attachment to the surface than non-covalently bound FN which was easily removed under sonication in 0.1 M NaOH. The FN coated surfaces demonstrated augmented endothelial cell attachment compared to bare 316LSS surfaces in vitro.;The surface-immobilized FN and SAMs properties were examined using polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) contact angle goniometry and cyclic voltammetry. This novel electrochemical method of SAM immobilization and protein attachment may also be expanded to other types of drugs/proteins and a variety of biomedical applications.;Hypothesis. It has been shown that rapid re-endothelization of the artery after stent induced trauma decreases the severity of SMC proliferation considerably. By covalently tethering a cell adhesion protein, fibronectin (FN), to a stent via linking self-assembled monolayers (SAMs) it is believed that FN will increase the rate of endothelial cell attachment to the stent. This may result in the formation of a functional and confluent endothelial layer around the stent, thereby suppressing restenosis.