Exploring doxorubicin localization in eluting TiO2 nanotube arrays through fluorescence correlation spectroscopy analysisElectronic supplementary information (ESI) available: Further details on the release measurements and analysis, fluorescence correlation spectroscopy measurements. See DOI: 10.1039/c2an36052g

• Main Authors: De Santo, Ilaria, Sanguigno, Luigi, Causa, Filippo, Monetta, Tullio, Netti, Paolo A
• Format: Journal Article
• Language: English
• Published: 01.10.2012
• ISSN: 0003-2654; 1364-5528
• DOI: 10.1039/c2an36052g

Drug elution properties of TiO 2 nanotube arrays have been largely investigated by means of solely macroscopic observations. Controversial elution performances have been reported so far and a clear comprehension of these phenomena is still missing as a consequence of a lack of molecular investigation methods. Here we propose a way to discern drug elution properties of nanotubes through the evaluation of drug localization by Fluorescence Correlation Spectroscopy (FCS) analysis. We verified this method upon doxorubicin elution from differently loaded TiO 2 nanotubes. Diverse elution profiles were obtained from nanotubes filled by soaking and wet vacuum impregnation methods. Impregnated nanotubes controlled drug diffusion up to thirty days, while soaked samples completed elution in seven days. FCS analysis of doxorubicin motion in loaded nanotubes clarified that more than 90% of drugs dwell preferentially in inter-nanotube spaces in soaked samples due to decorrelation in a 2D fashion, while a 97% fraction of molecules showed 1D mobility ascribable to displacements along the nanotube vertical axis of wet vacuum impregnated nanotubes. The diverse drug localizations inferred from FCS measurements, together with distinct drug-surface interaction strengths resulting from diverse drug filling techniques, could explain the variability in elution kinetics. Fluorescence correlation spectroscopy analysis shows different drug localizations in titania nanostructured drug-eluting coatings for diverse drug loading techniques employed.