Comparative imaging of a slow-release starch excipient.pdfVIP

/locate/carbpol Carbohydrate Polymers 70 (2007) 61–67Comparative imaging of a slow-release starch excipient tablet: Evidence of membrane formation Gre?gory Chauve a, Franc?ois Ravenelle b, Robert H. Marchessault a,* a Department of Chemistry, McGill University, 3420 University Street, Montreal, Que., Canada H3A 2A7 b Labopharm, Inc., 480 Boul. Armand Frappier, Laval, Que., Canada H7V 4B4 Received 7 December 2006; received in revised form 28 February 2007; accepted 6 March 2007 Available online 13 March 2007Abstract A controlled release excipient made of chemically modified high-amylose starch (HAS) has been used to explore the surface mem- brane responsible for the slow release characteristics. Using scanning electron microscopy (SEM) and X-ray computed microtomography (CMT), the radial and axial surfaces of dry, swollen and freeze-dried sections observed were arranged in concentric domains. The pres- ence of water enhances contrast in CMT imaging of the swollen tablet compared to the non-hydrated state. Freeze-dried SEM images showed a twin domain structure, thus defining membrane thickness. CMT quantified the average global porosity of the dry and swollen domains. The bird’s eye view of the latter defined a central-core with high contrast and 34% porosity while the average global porosity was 19% and the dry porosity was 10%. The overall membrane after 15 min swelling is best described as concentric hydrogel domains.  2007 Published by Elsevier Ltd. Keywords: Slow-release; Controlled-release; Excipient; High amylose starch; Membrane; Scanning electron microscopy; Tomography; Hydrogel; Porosity; Imaging1. Introduction Controlled delivery of medication from pharmaceutical tablets improves efficiency by avoiding the ‘‘up and down’’ drug concentration peaks in the patient’s blood resulting from multiple dose intakes. Various techniques have been used to study chemically modified high amylose starch (HAS) tablets, such as optical (Bussemer, Peppas, Bod- meier, 2003;