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Macungie, PA, United States

Rokicki R.,Electrobright | Haider W.,University of Texas-Pan American | Maffi S.K.,University of Texas Health Science Center at San Antonio
Journal of Materials Engineering and Performance | Year: 2014

Research was undertaken to determine the influence of the increased content of chromium in the outermost passive layer of magneto-electrochemically refined Co-Cr alloy L-605 surface on its hemocompatibility. The chemistry, roughness, surface energy, and wettability of conventionally electropolished (EP) and magnetoelectropolished (MEP) samples were studied with x-ray photoelectron spectroscopy (XPS), open circuit potential, atomic force microscopy, and contact angle meter. In vitro hemocompatibility of tested material surfaces was assessed using two important indicators of vascular responses to biomaterial, namely endothelialization and platelets adhesion. The endothelialization was assessed by seeding and incubating samples with human umbilical vein endothelial cells (HUVEC) for 3 days before counting and observing them under a fluorescent microscope. The platelet (rich plasma blood) adhesion and activation test on EP and MEP L-605 alloy surfaces was assessed using a laser scanning confocal microscope. The XPS analysis of MEP samples showed significant enrichment of the passive layer with Cr and O when compared with the EP one. The amount of other elements in the passive layer did not show a significant difference between EP and MEP treatments. The adhesion of HUVEC cells shows remarkable affinity to surfaces enriched in Cr (MEP) with almost 100% confluency. In addition, the number of platelets that adhered to standard EP surfaces was higher compared to the MEP surface. The present study shows that the chromium-enriched surface of cobalt-chromium alloy L-605 by the magnetoelectropolishing process tremendously improves surface hemocompatibility with regard to stent functionality by enhanced endothelialization and lower platelet adhesion and should be taken under consideration as an alternative surface of biodegradable polymer drug-eluting stents, polymer-free drug-eluting stents as well as bare-metal stents. © 2014, ASM International. Source

Rokicki R.,Electrobright | Haider W.,University of Texas-Pan American | Hryniewicz T.,Koszalin University of Technology
Journal of Materials Science: Materials in Medicine | Year: 2012

The influence of 6 % sodium hypochlorite (NaClO) treatment on adhesion and proliferation of MC3T3 pre-osteoblast cells seeded on electropolished (EP) and magnetoelectropolished (MEP) nitinol surfaces were investigated. The chemistry, topography, roughness, surface energy, wettability of EP and MEP nitinol surfaces before and after NaClO treatment were studied with X-ray photoelectron spectroscopy (XPS), profilometry, and contact angle meter. In vitro interaction of osteoblast cell and NaClO treated EP and MEP nitinol surfaces were assessed after 3 days of incubation by scanning electron microscopy. The XPS analysis shows that NaClO treatment increases oxygen content especially in subsurface oxide layer of EP and MEP nitinol. The changes of both basic components of nitinol, namely nickel and titanium in oxide layer, were negligible. The NaClO treatment did not influence physico-morphological surface properties of EP and MEP nitinol to a big extent. The osteoblast cells show remarkable adherence and proliferation improvement on NaClO treated EP and MEP nitinol surfaces. After 3 days of incubation they show almost total confluence on both NaClO treated surfaces. The present study shows that NaClO treatment of EP and MEP nitinol surfaces alters oxide layer by enriching it in oxygen and by this improves bone cell-nitinol interaction. © Springer Science+Business Media, LLC 2012. Source

Hryniewicz T.,Koszalin University of Technology | Konarski P.,Laboratorium Badawczo Pomiarowe Techniki Prozni | Rokosz K.,Koszalin University of Technology | Rokicki R.,Electrobright
Surface and Coatings Technology | Year: 2011

Hydrogen concentration in AISI 316L stainless steel samples was monitored perpendicularly to the flat sample surface up to the depth of 0.8μm, using secondary ion mass spectrometry (SIMS). Depth profile analysis was performed on the samples after electrolytic polishing under different conditions. Analyses were performed on SAJW-05 apparatus with quadrupole Balzers QMA-410 analyzer and Physical Electronics 06-350E ion gun. 5keV Ar+ primary ion beam of 100μm diameter was scanned over 1mm×0.8mm area. Positive (H+, C+, CH+, O+, Cr+, Fe+) and negative (H-, C-, CH-, O-, OH-, CrO-, FeO-) secondary ion emission was registered from central part of the scanned area (10% of area) during primary ion beam sputtering.Results of hydrogen depth profile analysis were compared for the samples after a conventional electrochemical polishing (EP), and magnetoelectropolishing (MEP). Both EP and MEP processes were carried out under the electrochemical conditions regarding also natural and forced convection. The steel samples taken of a hot-rolled sheet, as received (AR), and after abrasive polishing (MP), were used as a reference. Results show that the increased current density (up to 200A/dm2) and electrolyte stirring during electropolishing cause lowering of the hydrogen content in the samples, with the best result regarding hydrogen content decrease obtained on MEP200 sample. In fact, within the MEP process, characteristic with the self-contained electrolyte whirling, the contents of hydrogen are significantly decreased. © 2011 Elsevier B.V. Source

Rokicki R.,Electrobright | Hryniewicz T.,Koszalin University of Technology | Pulletikurthi C.,Florida International University | Rokosz K.,Koszalin University of Technology | Munroe N.,Florida International University
Journal of Materials Engineering and Performance | Year: 2015

Haemocompatibility of Nitinol implantable devices and their corrosion resistance as well as resistance to fracture are very important features of advanced medical implants. The authors of the paper present some novel methods capable to improve Nitinol implantable devices to some marked degree beyond currently used electropolishing (EP) processes. Instead, a magnetoelectropolishing process should be advised. The polarization study shows that magnetoelectropolished Nitinol surface is more corrosion resistant than that obtained after a standard EP and has a unique ability to repassivate the surface. Currently used sterilization processes of Nitinol implantable devices can dramatically change physicochemical properties of medical device and by this influence its biocompatibility. The Authors’ experimental results clearly show the way to improve biocompatibility of NiTi alloy surface. The final sodium hypochlorite treatment should replace currently used Nitinol implantable devices sterilization methods which rationale was also given in our previous study. © 2015, ASM International. Source

Rokicki R.,Electrobright
Medical Device and Diagnostic Industry | Year: 2010

Surface inclusions in nitinol stents, causing primary fatigue, corrosion, and nickel leaching sites, are studied. Nitinol inclusions are classified by origin and chemical composition. Classification by origin gives two kind of inclusions such as native that are distributed throughout the whole volume of the material including surfaces, and foreign that are strictly surface phenomena. Local martensitic transformation and stress concentration points are some of the problems that can be created by inclusions. A chemical test, an inclusions test, uses 6% sodium hypochlorite (NaClO) as a reagent and requires 15 minutes of immersion and observation to conclude presence or absence of surface inclusions. Electropolished nitinol implants have shown superior results in research compared with implants finished by other processes in terms of corrosion resistance, biocompatibility, reduced nickel leaching, and fatigue resistance. Source

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