In vitro evaluation of a new resilient, hard-carbon, thin-film coating as a bearing material for ventricular assist devices-In Vitro Bearing Evaluation of BioMedFlex by ProQuest


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									J. Biomedical Science and Engineering, 2010, 3, 525-528                                                                JBiSE
doi:10.4236/jbise.2010.35073 Published Online May 2010 (

In vitro evaluation of a new resilient, hard-carbon, thin-film
coating as a bearing material for ventricular assist devices
——In Vitro Bearing Evaluation of BioMedFlex

Nicole A. Mielke1, Alex L. Massiello1, David J. Horvath1, Stephen M. Benefit1, Darren Burgess2,
Leonard A. R. Golding1, Kiyotaka Fukamachi1
 Department of Biomedical Engineering/ND20, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA;
 BioMedFlex, LLC, Denver, North Carolina, USA.

Received 1 December 2009; revised 14 December 2009; accepted 20 December 2009.

ABSTRACT                                                            stage heart failure who are unresponsive to conven-
                                                                    tional therapies. Although current designs demonstrate
Our aim was to evaluate the potential use of Bio-                   adequate performance, reliability remains a significant
MedFlex® (BMF), a new resilient, hard-carbon, thin-                 issue, as these devices are implanted for extended dura-
film coating, as a blood journal bearing material in                tions (well beyond 1 year) and may likely be intention-
Cleveland Heart’s continuous-flow left and right ven-               ally implanted in patients as permanent (“destination”)
tricular assist devices (VADs). BMF is not classified               therapy. Because components of implantable pumps
as a diamond-like carbon (DLC) and differs from                     must withstand difficult in vivo environments and run-
other thin-film carbon coatings by its high flexural                ning conditions, carbon materials (diamond-like carbon
strength, radiopacity, and wear resistance. A 2- to                 [DLC] and pyrolytic carbon) have emerged as promising
                                                                    coating materials for pump components to enhance du-
4-μm-thick BMF adhesion layer was deposited on the
                                                                    rability and biocompatibility characteristics. Some of
VAD journal bearing surfaces. A commercial DLC                      these carbon coatings are chemically inert, wear and
coating used in other clinical blood pump applica-                  corrosion resistant, and bio- and hemocompatible. These
tions was used as a control. Durability and reliability             coatings may also minimize platelet adhesions and acti-
of the BMF coating was verified in severe pump                      vation, prevent thrombogenicity, and improve perform-
start/stop testing using 20 BMF-coated journal bear-                ance by decreasing power usage or increasing pump
ing pairs. The BMF-coated surfaces showed no coat-                  output.
ing failures, whereas 57% of the DLC bearing pairs                     The continuous-flow VADs of Cleveland Heart (Char-
developed scratches through the carbon coating, do-                 lotte, NC) have been adapted from the CorAide LVD-
cumenting that BMF can provide a durable coating                    4000 Left Ventricular Assist System (Arrow Interna-
in our blood journal bearing application. In conclu-                tional, Reading, PA), developed at Cleveland Clinic.
sion, BMF has shown qualities that support its sig-                 Detailed descriptions of the pump have previously been
                                                                    published [1,2]. The left and right ventricular assist de-
nificant advantages as an alternative journal bea-
                                                                    vices (LVADs and RVADs, respectively) consist of three
ring material in Cleveland Heart pumps. Our plan
                                                                    subassemblies: the volute housing, the rotating assembly
includes biocompatibility testing with ongoing animal
                                                                    (RA), and the stator assembly (Figure 1). The RA con-
studies, endurance testing with submerged pumps                     tains a cylindrical four-pole magnet and spins around the
running in saline, and assessment of batch coating                  titanium stator housing post, which contains the motor
processing capability.                                              windings. The RA is supported axially by permanent
                                                                    magnets and radially by a thin film of blood, forming a
Keywords: Heart Assist Device; Diamond-Like
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