Effects of surface functional modification of mesoporous silica nanoparticles on oral insulin delivery: A review

Convenient and painless oral formulations of insulin are more accessible to patients than subcutaneous insulin, which is inconvenient to use and has more adverse outcomes. However, due to the intrinsic properties of insulin, and the harsh environments and physiological barriers in the gastrointestinal tract, the structure of insulin is susceptible to destruction after oral administration, resulting in drug inactivation. Mesoporous silica nanoparticles (MSNs), exhibiting advantages such as the well-developed pore network and good biocompatibility, ensures the efficient loading of insulin, protect the activity and dominant conformation of insulin. This opens new ideas for oral insulin delivery. However, due to the complex environment of the gastrointestinal tract, unmodified MSNs are not sufficient to overcome the multiple barriers of the gastrointestinal tract for efficient delivery of oral insulin. In order to make insulin oral administration more efficient, researchers have designed many different modifications on the surface of MSNs. In this review, we present the challenges facing oral insulin. The synthetic methods and physical properties of MSNs used as drug carriers are summarized. The surface modifications of MSNs currently used as carriers for insulin delivery are summarized. The advantages and disadvantages of MSNs with different surface modifications as carriers for oral administration of insulin are discussed. The limitations and future perspectives of the current MSNs and surface-modified MSNs in oral insulin delivery systems are also written.