Binding of proteins and platelets to gas discharge-deposited polymers

Surface engineering of biomaterials with plasma techniques

In this study, 3 types of plasma techniques, i.e. plasma modification, plasma deposition and plasma followed by grafting reaction, are used for the fabrication of tools, medical devices and biomaterials. Depending on purpose, bioadhesion of cells and biomolecules is either looked for or avoided. Since the mechanisms of bioadhesion depend on the characteristics of the surface (hydrophilic or hydrophobic), modifying the surface by a treatment will alter the bioadhesion. These treatments are developed for the anti-fouling process, the sterilisation and the improvement of the formation of biofilms. They have also proved useful for the synthesis of biomimicking devices.

Nonporous silicone polymer coating of expanded polytetrafluoroethylene grafts reduces graft neointimal hyperplasia in dog and baboon models

PURPOSE

Neointimal hyperplasia frequently develops after placement of prosthetic vascular grafts and is a major cause of graft failure. This study was an attempt to prevent vascular lesion formation by coating the graft luminal surface with a thin layer of nonporous silicone polymer, and subsequently with an ultrathin layer of vapor phase (plasma gas)-deposited fluoropolymer, thereby providing a smooth and chemically uniform surface that was postulated to limit pannus tissue ingrowth across the graft anastomoses.

METHODS

Bilateral femoral arteriovenous (AV) conduits were constructed in four dogs using expanded polytetrafluoroethylene graft materials (ePTFE; 6-mm inside diameter, 2.5-cm long). In each animal, one femoral AV shunt was constructed from a graft whose luminal surface was entirely coated with polymer. On the contralateral side, an uncoated graft served as a control. Bilateral aortoiliac grafts were placed in three baboons using 5-cm segments of ePTFE (4-mm inside diameter). One end (1 cm) of each graft had been coated with polymer. In each animal, the coated end of one graft was placed proximally and the coated end of the second graft was placed distally in the contralateral vessels.

RESULTS

All grafts were patent at 30 days. In the dog model, there was a significant reduction in graft neointimal area at the venous anastomoses for the coated grafts compared with the uncoated grafts (0.03 +/- 0.02 mm2 and 1.11 +/- 0.54 mm2, respectively; p < 0.05). In the baboon model, the silicone coating significantly reduced the graft neointimal thickness (0.003 +/- 0.003 mm vs 0.21 +/- 0.05 mm; p < 0.05) and neointimal area (0.05 +/- 0.08 mm2 vs 0.82 +/- 0.58 mm2; p < 0.05).

CONCLUSIONS

These data demonstrate that healing of ePTFE grafts can be effectively modified by altering the physical properties of the graft surface. Neointimal hyperplasia within ePTFE grafts is significantly reduced by the local application of a fluorocarbon-coated, silicone-based polymer. The resulting graft flow surface effectively prevents tissue ingrowth from the adjacent native vessel, thereby preserving the anastomosis luminal area. This approach could represent a new strategy for limiting graft surface anastomotic neointimal hyperplasia.