Dual-controlled oral colon-targeted delivery of bovine insulin based on mesoporous phosphonate

The time- and pH-controlled oral colon-targeted delivery system for bovine insulin was developed by dip-coating lag-time films on tablet comprising bovine insulin-loaded pH-sensitive mesoporous phosphonate (ZrBPMP-3) as tablet core and absorption enhancer of insulin, sodium glycocholate, in outer layer, in which the lag time can be controlled via adjusting coating times of lag-time films and the release of bovine insulin in the colon can be triggered by pH-sensitive ZrBPMP-3. The pH transition release experiments show that the tablet with four times lag-time films coating can carry bovine insulin passing through the stomach and small intestine with a minimum release and trigger off the release of loaded bovine insulin in the colon under dual control, time control and pH value control. Furthermore, the released bovine insulin can still retain its native conformation, as evidenced by circular dichroism spectroscopy, indicating that bovine insulin cannot denature and lose its bioactive conformation during the loading, lag-time films coating, delivery and release. In addition, it is worth mentioning that ZrBPMP-3 almost exhibits non-cytotoxicity at low concentration in MTT assays. Thus, ZrBPMP-3 as a new kind of carrier and based on which developing controllable colon-targeted delivery system have potential application in oral delivery of insulin and even other therapeutic peptides and proteins.