Blood Compatibility Of Titanium Alloy Surface Modification With Polyethyleneimine/heparin Polyelectrolyte Multilayers

Objective①To prepare polyethyleneimine/heparin polyelectrolyte multilayers(PEMs)with an outermost layer of heparin on the surface of titanium alloy via layer by layer(L-B-L)technique;②To characterize the PEMs coating on the titanium alloy surface;③Todetermine the quantity of heparin on the surface of PEMs. Methods①First, cleanedtitanium alloy was treated by NaOH solution to obtain a precursor layer of self-assembled,and then specimens alternately soaked in polyethylenimine polycation solution and heparinpolyanion solution to build polyethylenimine/heparin PEMs structure;②The chemicalstructure, elements composition, surface topography and surface water contact angle of thespecimen surface was analyzed by the reflection infrared spectroscopy analysis, X-rayphotoelectron spectroscopy, the environmental scanning electron microscopy and thecontact angle measurement;③Using Toluidine Blue method to quantify the heparin ofthe specimen surface, then draw the heparin release curve. Results①Reflection infraredspectroscopy signal characteristics consistent with the chemical structure ofpolyethyleneimine and heparin;②Environmental scanning electron microscopy showsthe surface topography of the specimen surface;③The water contact angle of PEMs is43.2±1.8(°);④After15and7circulations of self-assemble, the quantity of hepain onthe specimen surface are3.04±0.7μg/cm2and2.60±0.4μg/cm2, with the heparin expulsionrate of45.8%and47.0%. Conclusion①It is successful to form PEMs on the surface oftitanium alloy using L-B-L technique by well contral of factors such as concentration, ionicstrength, PH value, temperature of polyethyleneimine and heparin solutions;②Thequantity of heparin on the specimen surface is relating to the number of layer, and thebonding strength of heparin using such technique is higher than physical adsorptionmethod. Objective To evaluate blood compatibility of polyethleneimine/heparin PEMs in vitro.Method The evaluating indicator of in vitro blood compatibility ofpolyethleneimine/heparin PEMs including: the test of hemolysis, prothrombin time (PT),activated partial thromboplastin time (APTT), the contents of human albumin andfibrinogen absorbed on the surface of specimen and Fig/Alb ratio, as well as plateletadhesion. Results①The hemolysis rate of PEMs was0.690%;②The prothrombin time(PT) and activated partial thromboplastin time (APTT) of PEMs were13.20±0.89s and51.33±2.87s;③Scanning electron microscopy showed that the number of platelets on thesurface of PEMs were significantly less than of titanium alloy surface. Conclusion The invitro blood compatibility of titanium alloy can be improved significantly after being coatedwith polyethleneimine/heparin PEMs with an outermost layer of heparin. Objective To evaluate blood compatibility of polyethleneimine/heparin PEMs in vivo.Method①Fifteen experiment rabbits were equally and randomly assigned to one of thethree groups: the TA4specimen group, the TA4-(PEI-Hep)15Hep specimen group and thecontrol group. Then successfully establish a rabbit model that specimens can be implantedinto the rabbit carotid.②To harvest the blood vessel in which the specimen wasimplanted, then observe thrombosis situation by macroscopic observation and microscopeobservation after made of HE staining slices. Results Compared to the TA4specimen group,the blood vessel came from the TA4-(PEI-Hep)15Hep specimen group formed fewerthrombosis and fibrous tissue, as well as slighter inflammatory cell infiltration. ConclusionIt is further confirmed by animal experiment that the blood compatibility of titanium alloycoated with polyethleneimine/heparin PEMs with an outermost layer of heparin is betterthan that of bare titanium alloy in vivo circumstances.