Development of expanded polytetrafluoroethylene graft with electret effect

Research Project

Project/Area Number	07671297
Research Category	Grant-in-Aid for Scientific Research (C)
Allocation Type	Single-year Grants
Section	一般
Research Field	General surgery
Research Institution	Nagoya University
Principal Investigator	NISHIKIMI Naomichi Nagoya University School of Medicine, Assistant Professor, 医学部, 講師 (40242862)
Co-Investigator(Kenkyū-buntansha)	SAKURAI Tsunehisa School of Medicine, Assistant Professor, 医学部, 助教授 (50144142)
Project Period (FY)	1995 – 1997
Project Status	Completed (Fiscal Year 1997)
Budget Amount *help	¥2,300,000 (Direct Cost: ¥2,300,000) Fiscal Year 1997: ¥600,000 (Direct Cost: ¥600,000) Fiscal Year 1996: ¥600,000 (Direct Cost: ¥600,000) Fiscal Year 1995: ¥1,100,000 (Direct Cost: ¥1,100,000)
Keywords	polytetrafluoroethylene / electret effect / prosthetic vascular graft / 動脈閉塞症
Research Abstract	Purpose : There are many reports on development of small caliber synthetic vascular graft. A little attention has been paid to graft surface electrical potential. Materials with surface electronegativity are accepted to have good blood compatibility. Expanded polytetrafluoroethylene (e-PTFE)is widely used material for vascular graft, and it has capability to have electret. An electret is not a battery and cannot supply energy to maintain a field in the presence of mobile ions. It is an insulator having persistent, internal electric polarization. We evaluated the effects of electret on e-PTFE with normal e-PTFE graft. Subject and Method : Surgical membranes made of e-PTFE were used as a graft material. According to a sheet electret method, a sheet of e-PTFE was electrified under corona discharge, and its electrokinetic voltage on negative surface was exceeded less than-1OOOV.Rectangular samples of non-electrified e-PTFE sheet (N type)and electret sheet(E type)were immersed in heparinized or EDTA added canine blood for 3 minutes. Samples were fixed immediately and percentage particle free surface area was evaluated with scanning electron microscope (SEM). Twenty mongrel dogs were used for in vivo study. Both types of grafts, sized lOx5mm were implanted in inferior vena cava. Dogs were sacrificed to retrieve graft at regular intervals, and samples were examined with SEM. Result : Electret effects on E type lasted for more than three years without attenuation. Immersion study showed significantly less particles were found on electronegative surface in E type. No difference was found between N and E type in implantation study. Conclusion : Electronegativity of e-PTFE sheet had the advantage of thromboresistance in vitro study, but it failed to show any advantages in vivo study. We used conventional sheet electret method, grafts were, therefore, implanted in a small patch fashion. Comparison of patency in tubular grafts is needed to elucidate electret effects.