Complex coacervation-controlled release from monoolein cubic phase containing silk fibroin and alginate.

pH-dependent release from monoolein (MO) cubic phase was obtained by taking advantage of complex coacervation between hydrophobically modified alginate (HmAL) and hydrophobically modified silk fibroin (HmSF) in the water channels. The degree of coacervation was investigated at pH 3.0 by a light scattering method and the maximum coacervation was observed when the ratio of HmAL to HmSF was 1:15. The degree of coacervation dramatically decreased (from 581.2 to 5.2 nm in size and from 267.9 to 12.3 nm in Kcps) when the pH of medium increased from 3.0 to 5.0. The % release in 100 h of FITC-dextran increased from 2.42 to 7.20% when pH of release medium increased from 3.0 to 9.0. Under acidic conditions, coacervate will block the water channels of cubic phase, suppressing the release. As the pH of release medium increases, the coacervate will dissolve, resulting in a higher release. The cubic phase could be exploited as a pH-sensitive carrier for the oral delivery of an acid-labile drug.