Insulin regulates blood glucose levels, and is the mainstay for the treatment of type-1 diabetes and type-2 when other drugs provide inadequate control. Therefore, effective oral Insulin delivery would be a significant advance in drug delivery. Herein, we report the use of the modified cell penetrating peptide (CPP) platform, Glycosaminoglycan-(GAG)-binding-enhanced-transduction (GET), as an efficacious transepithelial delivery vector in vitro and to mediate oral Insulin activity in diabetic animals. Insulin can be conjugated with GET via electrostatic interaction to form nanocomplexes (Insulin GET-NCs). These NCs (size and charge; 140 nm, +27.10 mV) greatly enhanced Insulin transport in differentiated in vitro intestinal epithelium models (Caco2 assays; >22-fold increased translocation) with progressive and significant apical and basal release of up taken Insulin. Delivery resulted in intracellular accumulation of NCs, enabling cells to act as depots for subsequent sustained release without affecting viability and barrier integrity. Importantly Insulin GET-NCs have enhanced proteolytic stability, and retained significant Insulin biological activity (exploiting Insulin-responsive reporter assays). Our study culminates in demonstrating oral delivery of Insulin GET-NCs which can control elevated blood-glucose levels in streptozotocin (STZ)-induced diabetic mice over several days with serial dosing. As GET promotes Insulin absorption, transcytosis and intracellular release, along with in vivo function, our simplistic complexation platform could allow effective bioavailability of other oral peptide therapeutics and help transform the treatment of diabetes.
Bibliographical noteFunding Information:
The research leading to these results has received funding from the European Research Council under the European Community's Seventh Framework Programme ( FP7/2007-2013 )/ ERC grant agreement 227845 and strategic research funding by Ulster University . J.E.D acknowledges the support of the Medical Research Council , the Engineering and Physical Sciences Research Council , and the Biotechnology and Biological Sciences Research Council UK Regenerative Medicine Platform Hub “Acellular Approaches for Therapeutic Delivery” ( MR/K026682/1 ). R.C.M. is recipient of an R.D. Lawrence Fellowship of Diabetes UK. S.R acknowledges the support of Punjab Educational Endowment Fund (PEEF) scholarship, Government of Punjab, Pakistan. We thank David Onion and team at the Flow cytometry facility ( University of Nottingham ) for expertise in flow cytometry and ImageStream analyses.
© 2023 The Authors
- Cell penetrating peptides (CPPs)
- Transepithelial delivery
- Oral insulin delivery
- Glycosaminoglycan-GAG-binding enhanced transduction (GET)