Feasibility, stability and release performance of a time-dependent insulin delivery system intended for oral colon release

The aim of the present work was to evaluate the viability of a time-dependent delivery platform (ChronotopicTM) in preparing an insulin-based system intended for oral colon delivery. The main objectives were to assess the influence of the manufacturing process and storage conditions on the protein stability. Insulin-loaded cores were manufactured by direct compression and were subsequently coated with hydroxypropyl methylcellulose (HPMC) in a top-spray fluid bed up to increasing weight gains, namely 20%, 60% and 100%. In order to evaluate the impact the operating conditions may have on the protein integrity, insulin and its main degradation products (A21-desamido insulin – A21, Other Insulin-Related Compounds – OIRCs, and High-Molecular Weight Proteins – HMWPs) were assayed on samples collected after each process step by chromatographic methods. Furthermore, long-term (4 °C) and accelerated (25 °C–60% RH) stability studies were carried out on tablet cores and coated systems by assessing insulin, A21, OIRC and HMWP percentages throughout a one-year storage period. In addition, the in vitro release behaviour was investigated during the same study period. The overall results indicated that the manufacturing process is not detrimental for insulin integrity and that 4 °C storage temperature alters neither the protein content nor the release performances of the device.It was therefore concluded that insulin-containing systems intended for oral colon delivery can be obtained by the ChronotopicTM technology.