Blood Compatibility of Metal Oxide Layers on Stainless-steel
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B9.47.1
Blood Compatibility of Metal Oxide Layers on Stainless-steel Kanji Tsuru, Shinji Takemoto, Tatsuhiro Yamamoto, Satoshi Hayakawa, Akiyoshi Osaka and Seisuke Takashima1 Biomaterials Laboratory, Faculty of Engineering, Okayama University, Okayama, 700-8530, JAPAN 1 Co-Operative Research Center, Okayama University, Tsushima, Okayama, 701-1221, JAPAN ABSTRACT We examined blood compatibility of titanium oxide layer on stainless-steel (SUS316L). The oxide layers with varied thickness were yielded on SUS316L plates by dip-coating of sol-gel solution starting from tetraethyltitanate. The blood compatibility was evaluated in term of platelet adhesion using platelet rich plasma. With increase in the thickness of the oxide layer, the number of adherent platelets decreased rapidly, reached minimum around 150nm. This indicated that the thickness of titanium oxide layer affected platelet adhesion. INTRODUCTION Artificial materials are widely used in medical devices that directly contact with blood. For the devices of this kind, thrombosis is a major complication induced by activation of the intrinsic coagulation system and formation of thrombus. Metallic stent used in order to prevent vessel recoil has been representative of medical devices contacted with blood. Most of metallic stents are made by stainless steel. There are some reports [1~4] to investigate the efficiency of coating heparin (anticoagulant) on stent because the blood compatibility is not still enough. However, new techniques without anticoagulant are required since a use of anticoagulant is not favor for hemopathy patient. We have reported in the previous study that titanium substrate treated with hydrogen peroxide solution and subsequently heating exhibited the excellent blood compatibility judging from the clotting time of human blood plasma [5,6]. This means titanium oxide may be a candidate in order to produce surface that has less complications when in contact with blood. In the present study, titanium oxide layers with varied thickness were yielded on stainless plates by coating of solution starting from tetraethyltitanate. Platelet adhesion tests were performed in order to investigate anti-thrombogenisity of stainless plate coated with the oxide layer.
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EXPERIMENTAL Substrates 10I10I0.1 mm in size were cut from a sheet of commercially SUS316L (supplied by Nilaco, Japan), and rinsed with acetone for 5 min three times in an ultrasonic cleaner. Titanium oxide layer was prepared through a sol-gel method starting from reagent grade tetraethyltitanate (Ti(OEt)4), ethanol (EtOH), distilled water (H2O) and hydrochloric acid solution (HCl). Table 1 shows the final mixing ratios of the chemicals for coating. Starting composition of coating sol was denoted as E10, E30 or E50 according to amount of EtOH. The sols were dip-coated on the substrate where the pull-up speed was 2mm/s. The coated substrates were heated at 300, 400 or 500°C for 10 minutes in a furnace. The titanium oxide layers prepared by 1, 3 or 5 iteration of dip-coating were denoted as D
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