Nanoporous materials have attracted significant attention as drug delivery platforms in which interfacial phenomena are often more influential than fluid mechanics in defining molecular loading capacity and release kinetics. This study employs nanoporous gold (np-Au) as a model material system to investigate physical mechanisms of molecular release of fluorescein (a small molecule drug surrogate) from the submicron-thick np-Au coatings. Specifically, the study reveals an interfacial mechanism where halide ion-gold surface interactions dictate the loading capacity and release kinetics of fluorescein. We systematically study the effect of halide concentration and species on release kinetics from sputter-deposited np-Au films with a combination of quantitative electron microscopy, fluorospectrometry, and electrochemical surface characterization techniques. The results suggest that the interplay of halide-gold interaction probability and affinity determine the nature of release kinetics. The former mechanism plays a more dominant role at higher ionic strengths, while the latter is more important at lower ionic strengths. This interfacial phenomenon is further complemented by functionalizing the np-Au with self-assembled monolayers (SAMs) of alkanethiols for modulating gold surface-halide affinity and consequently the molecular release kinetics.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Surfaces, Coatings and Films
- Physical and Theoretical Chemistry