Plasma surface modification of the inner surface of LDPE tubing for biomedical applications

Plasma surface modification of the inner surface of small diameter non ga s-permeable low-density polyethylene (LDPE) tubing has been accomplished. Surface characterization results show that the inner surface of the tubing can be modified uniformly by ammonia, hexamethyldisiloxane (HMDSO), and HMDSO/NH₃ gas mixtures. Captive bubble contact angle measurements demonstrated that the surfaces modified by the ammonia plasma and propane sultone posttreatment are more hydrophilic than the control surface. The addition of ammonia to the HMDSO gas reduced the contact angle values of the plasma polymerized siloxanes. Ex vivo canine shunt experiments indicated that the ammonia plasma modified surface and the ammonia/propane sultone-treated surface are more platelet activating than the control (i.e., nontreated LDPE). In contrast, the HMDSO-based plasma polymerized surfaces showed similar blood compatibility to that of the control.