Preparation of microparticles composed of cinnamoyl gelatin and cinnamoyl alginate by spray-drying method and effect of UV irradiation and pH value on their release property

Microparticles composed of cinnamoyl gelatin (CinGel) and cinnamoyl alginate (CinAlg) were prepared as a UV irradiation- and pH-responsive carrier by a spray-drying method. CinGel and CinAlg were prepared by a condensation reaction. Using a colorimetric method, the gelatin to CA mass ratio and the alginate to CA mass ratio were calculated to be 1:0.04 and 1:0.02, respectively. The complexation of CinGel and CinAlg in aqueous solution took place when the medium was acidic (e.g., pH 4.0) and the maximum complexation was obtained when the CinGel/CinAlg mass ratio was 7:3. On SEM photographs, some spray-dried CinGel/CinAlg particles were spherical and others were irregularly shaped, and the diameter was a few to tens of micrometers. The release degrees of amaranth loaded in UV-treated microparticles were lower than those of the dye loaded in UV-untreated ones, possibly because of the photo cross-linkage of CinGel and CinAlg. Regardless of whether the microparticles were UV-treated, the release degree at pH 4.0 was significantly lower than the release degree at pH 6.0 and pH 8.0, possibly because of complexation of CinGel and CinAlg under the acidic condition.