Slow Release Kinetics of Mitoxantrone from Ordered Mesoporous Carbon Films

High porosity and surface areas of ordered mesoporous materials provide substantial capacity for loading of guest molecules and the well-defined morphology of such materials can control their transport for controlled release. Here, the loading and release of mitoxantrone from unmodified ordered mesoporous carbon films is monitored using UV/Vis spectroscopy. Organic-organic self-assembly of Pluronic F127 with phenolic resin leads to interconnected elliptical pores (≈2 nm) in the film after carbonization. Interestingly, the total loading (2.6 ± 0.4 μg/cm²) and release of mitoxantrone is independent of film thickness (50-400 nm), suggesting diffusion limitations in pore filling. With alternative template, the pore size increases to ≈5 nm and the mitoxantrone loading increases to 3.5 ± 0.9 μg/cm², but the loading still remains thickness independent. Using phosphate buffered saline at 37 °C, less than 60 % of the loaded mitoxantrone is readily released from the mesoporous carbon films over a two-week period. The release profile includes an initial burst with a modest fraction (< 20 %) of the loaded drug released within the first day, followed by a near linear release over the subsequent 5-9 days. Interestingly, the smaller pores (ca. 2 nm) release nearly 50 % more mitoxantrone over 2 weeks than the larger pores (ca. 5 nm), despite the lower initial loading. These results illustrate potential limitations as well as opportunities for the use of highly hydrophobic porous materials for the controlled release of hydrophobic biologically active compounds as drug delivery systems.