Microparticles comprising cinnamoyl cellulose and cinnamoyl gelatin prepared by emulsion method and their pH and electric field-responsive release property

Abstract

pH- and electric field-responsive microparticles were prepared by photo cross-linking cinnamoyl gelatin (CinGel) and cinnamoyl cellulose nanocrystal (CinCNC) contained in the water droplet of W/O emulsion. Cinnamoyl chloride (CC) was covalently attached to Gel and CNC through a condensation reaction to obtain CinGel and CinCNC, confirmed by 1H NMR and FT-IR spectroscopy. Using a colorimetric method, the cinnamoyl group (CG) content of CinGel was determined to be 1.6 % and that of CinCNC to be 3–15.3 %, depending on the CC/CNC ratio in the reaction mixture. The maximum photo-dimerization degree of CG of CinGel obtained under UV irradiation was about 33 % and that of CinCNC was 4.4–7.5 %. Microparticles were prepared by cross-linking CinGel and CinCNC contained in the water droplet of the emulsion using UV irradiation. Sphere-like particles and irregularly shaped ones were found on the SEM photo of CinGel/CinCNC microparticles and the mean dimeters were determined to be 11.6–17.1 µm. CinGel/CinCNC ratio in the emulsion little affected the shape and size of the resulting microparticles. An energy dispersive spectroscopy revealed that the microparticle composition was reflecting CinGel/CinCNC ratio in the emulsion. The release of a payload (i.e. amaranth) markedly promoted as the medium pH value increased from 3 to 8, possibly due to the decomplexation of CinGel/CinCNC electrostatic complex and/or the electrostatic expulsion of the payload from CinGel. The release was expedited as the applied voltage increased up to 4.5 V, probably due to the shear stress-induced deformation of the microparticle matrix and/or the forced electrostatic expulsion of the payload.