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Evaluation of Nanoporous Carbon Thin Films for Drug Loadingand Controlled Release

Mesoporous materials that possess large surface area,
tunable pore size, and ordered structures are attractive features
for many applications such as adsorption, protein separation,
enzyme encapsulation and drug delivery as these materials can be
tailored to host different guest molecules. Films provide a model
system to understand how the pore orientation impacts the potential
for loading and release of selectively sized molecules. This
research work aims to develop structure-property relationships to
understand how pore size, geometry, and surface hydrophobicity
influence the loading and release of drug molecules. In this study,
the pore size is systematically varied by incorporating
pore-swelling agent of polystyrene oligomers (hPS) to soft
templated mesoporous carbon films fabricated by cooperative
assembly of poly(styrene-block-ethylene oxide) (SEO) with phenolic
resin. To examine the impact of morphology, different compositions
of amphiphilic triblock copolymer templates, poly(ethylene
oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide)
(PEO-PPO-PEO), are used to form two-dimensional hexagonal and cubic
mesostructures. Lastly, the carbonization temperature provides a
handle to tune the hydrophobicity of the film. These mesoporous
films are then utilized to understand the uptake and release of a
model drug Mitoxantrone dihydrochloride from nanostructured
materials. The largest pore size (6nm) mesoporous carbon based on
SEO exhibits the largest uptake (3.5μg/cm2); this is
attributed to presence of larger internal volume compared to the
other two films. In terms of release, a controlled response is
observed for all films with the highest release for the 2nm cubic
film (1.45 μg/cm2) after 15 days, but this is only 56 % of
the drug loaded. Additionally, the surface hydrophobicity impacts
the fraction of drug release with a decrease from 78% to 43%, as
the films become more hydrophobic when carbonized at higher
temperatures. This work provides a model system to understand how
pore morphology, size and chemistry influence the drug loading and
release for potential implant applications.