All ZrNT were cleaned by washing with ethanol, deionized water, and dried with N 2 prior to drug loading. Diclofenac sodium (DCF) was selected as a model drug and loading was carried out by pipetting 50 µL (0.045 mM) of the drug in ethanol, onto the active surface area of the post-treated nanotubes. After pipetting, the NTs were left undisturbed for a minute and a half, enabling diffusion dependent deposition into the tube, followed by gentle heating at ~ 50 ͦ C to evaporate the solvent.