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CoCr alloy is commonly used in variouscardiovascular medical devices for its excellent physical and mechanicalproperties. However, the formation of blood clots on the alloy surfacesis a serious concern. This research is focused on the surface modificationof CoCr alloy using varying concentrations (1, 25, 50, 75, and 100mM) of phosphoric acid (PA) and phosphonoacetic acid (PAA) to generatevarious surfaces with different wettability, chemistry, and roughness.Then, the adsorption of blood plasma proteins such as albumin andfibrinogen and the adhesion, activation, and aggregation of plateletswith the various surfaces generated were investigated. Contact angleanalysis showed PA and PAA coatings on CoCr provided a gradient ofhydrophilic surfaces. FTIR showed PA and PAA were covalently boundto CoCr surface and formed different bonding configurations dependingon the concentrations of coating solutions used. AFM showed the formationof homogeneous PA and PAA coatings on CoCr. The single and dual proteinadsorption studies showed that the amount of albumin and fibrinogenadsorbed on the alloy surfaces strongly depend on the type of PA andPAA coatings prepared by different concentrations of coating solutions.All PA coated CoCr showed reduced platelet adhesion and activationwhen compared to control CoCr. Also, 75 and 100 mM PA-CoCr showedreduced platelet aggregation. For PAA coated CoCr, no significantdifference in platelet adhesion and activation was observed betweenPAA coated CoCr and control CoCr. Thus, this study demonstrated thatCoCr can be surface modified using PA for potentially reducing theformation of blood clots and improving the blood compatibility ofthe alloy. [ABSTRACT FROM AUTHOR]

Antiproliferativedrugs such as paclitaxel and sirolimus are deliveredfrom stents to inhibit the growth of smooth muscle cells (SMCs) forpreventing neointimal hyperplasia. However, these drugs delay thegrowth of endothelial cells (ECs) as well and cause late stent thrombosis.We recently demonstrated the use of Vitamin-C (l-ascorbicacid, l-AA) over paclitaxel and sirolimus for inhibitingSMCs growth and promoting EC growth simultaneously. In this study,we have investigated the delivery of l-AA from CoCr alloysurfaces for potential use in stents. A polymer-free phosphoric acid(PA) platform and a polymer-based poly(lactic-co-glycolicacid) (PLGA) platform were used for coating l-AA onto CoCrsurfaces. For the PA platform, FTIR confirmed that the PA was coatedon CoCr, while the AFM showed that the PA coating on the CoCr surfacewas homogeneous. The successful deposition of l-AA on PA-coatedCoCr was also confirmed by FTIR. The uniform distribution of l-AA crystals on PA-coated CoCr was shown by SEM, optical profilometer,and AFM. The drug release studies showed that l-AA (276 μg/cm2) was burst released from the PA platform by 1 h. For thePLGA platform, SEM showed that the l-AA incorporated polymerfilms were smoothly and uniformly coated on CoCr. FTIR showed that l-AA was incorporated into the bulk of the PLGA film. DSC showedthat the l-AA was present in an amorphous form and formedan intermolecular bonding interaction with PLGA. The drug releasestudies showed that l-AA was sustained released from thePLGA coated CoCr for up to 24 h. The SEM, FTIR, and DSC characterizationsof samples collected post drug release shed light on the mechanismof l-AA release from PLGA coated CoCr. Thus, this study demonstratedthe delivery of l-AA from biomaterial surfaces for potentialapplications in stents and other implantable medical devices. [ABSTRACT FROM AUTHOR]