Investigation On The Surface Modification Of Titanium By Polypyrrole Coating For Artificial Cardiovascular Device Fabrication

PartⅠSynthesis and surface characteristics of polypyrrole coated titaniumObejective①To prepare polypyrrole (PPy) coating on titanium (Ti) electrochemically.②To investigate the surface characteristics of PPy coated Ti(Ti/PPy). Methods①Polypyrrole coating was grown galvanostatically on Ti plates at a current density of 2.5 mA/cm~2 for 20 min using a platinum counter electrode and an Ag/AgCl reference electrode. The synthesis solution is composed of 0.1 M pyrrole monomer and 0.1 M sodium-p-toluene sulfonate.②The resultant polypyrrole coating was characterized in terms of adhesive strength by pull-off test, contact angle measurement by contact angle tester, chemical composition by the attenuated total re?ection Fourier transform infrared (ATR-FTIR) and surface morphology by scanning electron microscopy (SEM), respectively. Results①Complete, even and deep green coating was obtained on Ti substrate.②The adhesion strength of PPy coating to Ti substrate amounts to up to 18.02±1.10MPa and the water contact angle and deduced surface energy for PPy coating is 75.70±2.14((?)°) and 40.19(mJ/m~2) respectively, compared to 66.10±2.25((?)°) and 46.67(mJ/m~2) for uncoated Ti correspondingly. The typical signals featuring PPy chemical composition were obtained by ATR-FTIR and the typical"cauliflower"like surface morphology was shown clearly by SEM as well. Conclusion①Complete, even and intimately adherent PPy coating can be synthesized on Ti substrates galvanostatically.②The resultant PPy coating possesses greater water contact angle and lower surface energy compared to uncoated Ti(P<0.05). PartⅡInvestigation on in vitro blood compatibility of polypyrrolecoated titanium Objective To investigate the in vitro blood compatibility of PPy coated Ti (Ti/PPy). Methods Ti/PPy was evaluated for in vitro blood compatibility in terms of hemolysis, dynamic clotting time, thrombin time (TT), prothrombin time (PT), activated partial thromboplastin time (APTT), platelet adhesion and C3a level and uncoated Ti and polytetrafluoroethylene (PTFE) were both or either used as references in the latter six analysises. Results The hemolysis rate for Ti/PPy was analyzed to be 0.516% and the dynamic clotting time for Ti/PPy is comparable to that for PTFE (P>0.05)and significantly longer than that for uncoated T(iP<0.05). As regards prothrombin time (PT), activated partial thromboplastin time (APTT) and thrombin time (TT), they are 14.0±0.2 seconds, 23.2±0.3 seconds and 15.8±0.6 seconds for Ti/PPy compared to 11.2±0.7 seconds, 20.5±0.3 seconds and 14.1±0.2 seconds for uncoated Ti. However, in terms of these results there is no significant difference between Ti/PPy and PTFE, the PT, APTT and TT of which is determined to 14.5±0.3s, 23.1±0.4s, 16.1±0.3s, respectively (P>0.05). The C3a level for Ti/PPy is 1.39±0.41μg/ml which is comparable to a level of 1.10±0.27μg/ml for blank control(P>0.05)but significantly lower compared to uncoated Ti which is 4.73±0.65μg/ml(P<0.01). In the platelet adhesion test it was shown by SEM that the adhered platelets on the surface of Ti were considerable in contrast to almost no platelets on Ti/PPy. Conclusion: The in vitro blood compatibility of Ti/PPy is comparable to that of polytetrafluoroethylene (PTFE) and significantly superior to that of uncoated Ti.PartⅢInvestigation on in vivo blood compatibility of polypyrrole coated titaniumObjective To investigate the in vivo blood compatibility of PPy coated Ti (Ti/PPy). Methods Four female rabbits were selected with weight varying between 5kg and 6 kg for in vivo implantation. For each rabbit one Ti/PPy and uncoated Ti plates (1mm×2mm×20mm) were implanted onto the walls of both common carotid arteries of it respectively on condition of anesthesia after cleaning and sterilizing. Routine antiseptic and anticoagulant treatment was delivered to each rabbit after operation and every 2 weeks after implantation, one rabbit was sacrificed and the grafts were explanted for surface morphology analysis with SEM. Results It was shown that there was only mild fibrin absorption onto the surface of Ti/PPy explants while significant thrombosis appeared on the Ti explants. Conclusion The in vivo blood compatibility of Ti/PPy is superior to that of uncoated Ti.