An interlayer approach was adopted to achieve adequate adhesion between a D
LC coating deposited by plasma-assisted CVD and a titanium substrate as par
t of a study to coat a bi-leaflet heart valve prosthesis. The interlayers (
TiC and TiN) were deposited by d.c. ion plating. TiN was also deposited by
reactive r.f. sputtering. The substrate, interlayers and DLC were assessed
for haemocompatibility and thrombogenicity using a dynamic blood method and
interactions with rabbit blood platelets, respectively. The adhesion, acti
vation and morphology of the platelets were determined by stereological tec
hniques using SEM. All surfaces were assessed topographically by stylus pro
filometry and AFM. Surface energies were compared by liquid drop goniometry
. The structure and crystallographic orientation of the TiN interlayers wer
e determined using XRD. The coatings produced no haemolytic effect, except
in the case of TiN deposited by reactive r.f. sputtering which showed a sig
nificant effect after longer assessment periods. In contrast to the DLC coa
ting, all of the interlayers showed a slight tendency towards thrombus form
ation during the later stages of incubation. Platelet spreading correlated
with the surface energy of the coatings. (C) 1999 Elsevier Science S.A. All
rights reserved.