A drug delivery system based on ɛ-polylysine-modified titania nanotube (ɛ-PL-TNTs) arrays was prepared. Polylysine on the nanotubes' surface can effectively bind with alendronate, a drug for the treatment of osteoporosis, through chemical bond. The bonds are fairly stable in an acid environment and cannot easily break up in a physiological environment. The ɛ-PL-TNTs increased the amount of drug loading by 9% in weight. The in vitro release profile of alendronate from ɛ-PL-TNTs showed a significant reduced burst release and an extended overall release of more than 15 days.
Nanostructured materials play a fundamental role in orthopedic research owing to their outstanding properties and excellent biocompatibility. Titania nanotube (TNT) arrays engineered by electrochemical anodization process have been extensively explored and used as effective carriers for controlled drug delivery. In this study, we proposed a drug delivery system based on coordination bond. Iron (III), Fe3+, on the nanotube surface can effectively bind to alendronate sodium (NaAL), a drug for the treatment of osteoporosis, through coordination bonds, which can be formed or broken through the change of pH, and thus can be controlled by pH. The pH-responsive system was prepared by three-step procedure: (i) fabrication of TNTs by electrochemical anodization, (ii) modification of amino groups on the surface of nanotubes by hydrothermal method, and (iii) amino-functionalized nanotubes by Fe3+ solution soak. The Fe-modified TNTs not only allowed alendronate-loading content of up to 50.2% by weight, which is significantly higher than most drug delivery systems previously reported, but also delayed and prolonged drug release. Moreover, in vitro drug release experiments demonstrated that coordination bond-based TNT system may have great potential applications in clinical use.
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