Modulated release of dexamethasone from chitosan-carbon nanotube films

Modulated release of dexamethasone (DEX) by electrical stimulation was investigated using chitosan (CHIT) and single walled carbon nanotubes (SWNT) host carrier films. Drug-loaded CHIT/SWNT composite films were solution-cast on carbon paper substrates. Unstimulated and stimulated release of DEX in phosphate buffer saline (PBS) solution at pH 7.4 was measured by UV–visible spectroscopy. For experiments involving electrical stimulation, the effects of voltage amplitude, electrode polarity, and SWNT content were investigated. Accelerated and complete DEX release was observed upon potentiostatic application of a negative potential (−0.8 V vs. Ag/AgCl) to the composite film, which was attributed to the electrostatic repulsions of SWNTs and DEX during charging. It was also found that the DEX release can be slowed down during passive release (unstimulated) through the addition of SWNTs. Further control can be achieved upon application of a positive potential (+0.15 V vs. Ag/AgCl) in which the release rate was slower than in the passive case.