Preparation and properties of hydrophobic films based on acetylated broken-rice starch nanocrystals for slow protein delivery

Native and acetylated broken-rice starches (nanocrystals) with different degrees of substitution (DS) and their corresponding films were individually prepared, and the drug release profiles, weight loss, solubility and dispersion and surface morphology were comparatively studied. Bovine serum albumin (BSA) was used as a model drug. Acetylated native starch (ANS) DS 2.58, acetylated starch nanocrystals (ASN) DS 0.98, ASN DS 1.86, and ASN DS 2.72 were observed to be very soluble in chloroform. BSA was released rapidly from the native rice starch (NS) and ANS DS 2.58 films. ASN with high DS significantly slowed down the release of BSA from films, the percentages of BSA released from film ASN DS 2.72 only reached to 13% after 3.5 weeks release, and the release data followed Korsmeyer-Peppas equation. Further studies reveal that the particle size of ASN DS 2.72 was smallest, and the weight loss of ASN DS 2.72 film was lowest. The results demonstrate that acetylation and nanometer particle form of rice starch film can effectively retard protein drug release, and the prepared films based on ASN with high DS from broken rice may be suitable for the controlled protein delivery.