Controlling the dissolution rate of hydrophobic drugs by incorporating carbon nanotubes with different levels of carboxylation

We present the anti-solvent precipitation of hydrophobic drugs griseofulvin (GF) and sulfamethoxazole (SMZ) in the presence of carboxylated carbon nanotubes (f-CNTs). The aqueous dispersed f-CNTs were directly incorporated into the drug particles during the precipitation process. f-CNTs with different levels of carboxylation were tested where the hydrophilicity was varied by altering the C:COOH ratio. The results show that the hydrophilic f-CNTs dramatically enhanced the dissolution rate for both drugs, and the enhancement corresponded to the hydrophilicity of f-CNTs. The time to reach 80% dissolution (t80) reduced from 52.5 min for pure SMZ to 16.5 min when incorporated f-CNTs that had a C:COOH ratio of 23.2 were used, and to 11.5 min when the ratio dropped to 16. A corresponding decrease was observed for SMZ for the above-mentioned f-CNTs. The study clearly demonstrates that it is possible to control the dissolution rate of hydrophobic drugs by altering the level of carboxylation of the incorporated CNTs.