Preparation Of Controllable Nanostructured Oxide Film On TLM Alloy For Application In Drug Delivery

Preparation of drug-loaded oxide layers on metal vascular stents is one of theeffective ways to solve subacute thrombosis and late stent thrombosis for currentpolymer drug-eluting stents. In this thesis, ordered nanostructured oxide films wereprepared on near β TLM (Ti-25Nb-3Mo-2Sn-3Zr) biomedical alloy by anodizationtechnique. Furthermore, the in vitro performance of drug loading/releasing fromanodized specimens and the related biocompatibility were investigated usingDexamethasone (DXM) and Rapamycin (Rapa) as model drugs. The main results areas the followings.Regular nanopores and nanotubes/nanopores could be obtained on TLM alloy byone-step anodization technique. During the self-organizing process of nanostructuredoxide via anodization technique, the ordered nanopores initially occured, which wasfollowed by the splitting process of nanoporous boundaries, resulting in the formationof hierarchical oxide structures with underlying nanopores and upper nanotubes. Thenanopores were interconnected with the upper nanotubes, possessing the samepore-to-pore distance, which was dependent on anodization voltage and independenton anodization time. With the assistance of electric field, F ions aggregated around thenanoporous boundaries, which could form water-soluble fluorides with metal oxides,making nanopores split. Meanwhile, the present study indicated that the the alloyingcomponents played an important role in the self-organizing oxide structures. TLMalloy mainly contains Ti and Nb, and niobium oxide is significantly more resistant toF ions than titanium oxide, which could prevent the fast splitting of regularnanoporous intervals. This could be used to explain the formation of hierarchicaloxide structure instead of the nanotubes on anodized pure Ti.Highly ordered nanoporous oxide layer on TLM alloy was achieved by two-stepanodization treatment, which was amorphous and showed good hydrophily.Single-drug (DXM) and double-drug (DXM-Rapa) were loaded onto the two-stepanodized TLM alloy via vacuum-assisted drying method. The results of SEM andFTIR indicated that drugs were well loaded onto the anodic oxide films. The in vitrodrug-release behavior demonstrated that the drug release could be divided into twophases: burst-release phase and slow-release phase. Drug-loading cycles could controlthe drug-loading quantity and finally control drug-releasing duration, which was up to more than four weeks. Compared with the reported drug-loaded TiO2nanotubes, thepresent drug-loaded system was more stable and lasted longer. The hemolysis testindicated that hemolysis rates of all the tested specimens were lower than5%, whichmet the hemolysis rate standard for biomedical materials and proved that thebiocompatibility of the biomedical TLM alloy was improved by the nanostructuredoxide film.