Nanoengineered drug releasing aluminium wire implants: a model study for localized bone therapy

A needle puncture approach using nanoengineered aluminium (Al) wires as drug-releasing implants is explored for localized drug delivery in bone using an ex vivo bone reactor. The wire implants were prepared by electrochemical anodization with the formation of a thin nanoporous alumina (NPA) layer on their surface and pore diameters of 30-35 nm and pore lengths of 10-60 μm. An in vitro drug release study of a model drug from the implants, prepared with different thicknesses of NPA layers (pore lengths), showed a considerable influence on drug release characteristics. The results confirmed that by controlling the pore length it is possible to tune the drug releasing performance of the implants and achieve a sustained release for an extended period. The biocompatibility study of the implants evaluated using human osteoblast cell culture showed strong growth of cells, their spreading and their adhesion to the implant surface. The drug loaded wire implants inserted inside bone by a needle puncture approach are evaluated for ex vivo drug release inside bone using a bone reactor (Zetos). The results demonstrated consistent and slow drug release from implants and distribution inside bone monitored in situ using a live imaging technique. The cross-sectional study of inserted wire implants after an extended period of release confirmed stable and unchanged NPA morphology. Histology of bone in contact with implants indicates the presence of viable osteocytes along the inserted area indicating that this method is a reliable approach and NPA wire implants are harmless devices. Overall, this study demonstrates that needle guided implantation of nanoengineered and drug loaded porous wires could be used as a new drug releasing implants for localized bone therapy and treatment of bone disease such as bacterial infection, healing, and potentially bone cancer.