Overcoming epithelial barriers to enhance drug absorption is a major challenge for nanoparticle (NP)-based mucosal delivery systems. With adequate physicochemical properties, the transepithelial delivery of NPs may be efficiently enhanced. However, little is known about the role of elasticity on the transport of NPs across the polarized epithelium, especially the processes and mechanisms of endocytosis, intracellular trafficking and exocytosis. In this study, we discovered that zwitterionic hydrogel NPs with varied elasticity displayed considerably different oral insulin absorption on diabetic rats. It was found that NP elasticity strongly shaped the transepithelial behaviors of NPs, and the increase of elasticity boosted the transcytosis by improving both endocytosis and exocytosis. Elasticity also showed a profound effect on the intracellular trafficking routes of NPs, which was closely related to distribution of NPs in exocytosis pathway and their intra-endosome sphere-to-ellipsoid shape transformation. Importantly, NPs with zwitterionic surface experienced more efficient basolateral exocytosis than apical exocytosis, while the elasticity-related exocytosis enhancement appeared to be non-selective. Therefore, tailored elasticity could promote mucosal transcytosis of NPs, which was able to be further improved with biomimetic zwitterionic surface. This study may provide important knowledge for the design of functional nanovehicles to efficiently overcome mucosal epithelial barriers in the future.

Glucagon-like peptide-1 receptor agonists (GLP-1 RA) are a series of polypeptides broadly applied in the long-term treatment of type Ⅱ diabetes. However, administration of GLP-RA is mainly through repetitive subcutaneous injection, which may seriously decrease the compliance and safety. Herein, a bio-inspired oral delivery system was designed to enhance the oral absorption of liraglutide (Lira), a kind of GLP-1 RA, by mimicking the natural cholesterol assimilation. 25-hydroxycholesterol (25HC), a cholesterol derivative, was modified on the surfaced of Lira-loaded PLGA nanoparticles (Lira 25HC NPs) and functioned as a "top-down" actuator to facilitate unidirectional transcytosis across the intestinal epithelium. After oral delivery, Lira 25HC NPs displayed improved therapeutic effect as compared with oral free Lira on type Ⅱ diabetes db/db mice, as evidenced by multiple relieved diabetic symptoms including the enhanced glucose tolerance, repressed weight growth, improved liver glucose metabolism, decreased fasting blood glucose, HbA1c, serum lipid, and increased β cells activity. Surprisingly, the fasting blood glucose, liver glucose metabolism, and HbA1c of oral Lira-loaded 25HC NPs were comparable to subcutaneous injection of free Lira. Further mechanisms revealed that 25HC ligand could mediate the nanoparticles to mimic natural cholesterol absorption by exerting high affinity towards apical Niemann-Pick C1 Like 1 (NPC1L1) and then basolateral ATP binding cassette transporter A1 (ABCA1) overexpressed on the opposite side of intestinal epithelium. This cholesterol assimilation-mimicking strategy achieve the unidirectional transport across the intestinal epithelium, thus improving the oral absorption of liraglutide. In general, this study established a cholesterol simulated platform and provide promising insight for the oral delivery of GLP-1 RA.

The epithelium is a formidable barrier to the absorption of orally delivered nano-vehicles. Here, by exploring a nutrient-absorption pathway, a self-amplified nanoplatform was developed to promote apical-to-basolateral transcytosis across the epithelium. The nanoplatform consisted of fructose-modified polyethylene glycol coated nanoparticles (Fru-PEG NPs) and a sweetener, acesulfame potassium (AceK) in combination. Compared with regular PEGylated nanoparticles, the combination exhibited a 3.9-fold increase of absorption following oral gavage in mice and an 8.8-fold increase of transepithelial transport in vitro. When encapsulated with insulin, the combination regimen elicited a stronger hypoglycemic effect, with a pharmacological bioavailability of 18.56%, which was 3.2-fold higher than that of PEG NPs. We demonstrated that a large proportion of Fru-PEG NPs underwent internalization and basolateral exocytosis via a glucose transporter type 2 (GLUT2)-dependent process, which is an important fructose assimilation pathway. Notably, co-administered AceK could prime the epithelial cells with increased apical distribution of GLUT2, thus amplifying this unidirectional transcytosis of nanoparticles. This work is the first proof-of-concept study of manipulating and amplifying a nutrient-absorption pathway to facilitate the unidirectional trans-epithelial transport of orally administered nano-delivery vehicles.

As endogenous courier vesicles, exosomes play crucial roles in macromolecule transmission and intercellular communication. Therefore, exosomes have drawn increasing attention as biomimetic drug-delivery vehicles over the past few years. However, few studies have investigated the encapsulation of peptide/protein drugs into exosomes for oral administration. Additionally, the mechanisms underlying their biomimetic properties as oral delivery vehicles remain unknown. Herein, insulin-loaded milk-derived exosomes (EXO@INS) were fabricated and the in vivo hypoglycemic effect was investigated on type I diabetic rats. Surprisingly, EXO@INS (50 and 30 IU/kg) elicited a more superior and more sustained hypoglycemic effect compared with that obtained with subcutaneously injected insulin. Further mechanism studies indicated that the origin of excellent oral-performance of milk-derived exosomes combined active multi-targeting uptake, pH adaptation during gastrointestinal transit, nutrient assimilation related ERK1/2 and p38 MAPK signal pathway activation and intestinal mucus penetration. This study provides the first demonstration that multifunctional milk-derived exosomes offer solutions to many of the challenges arising from oral drug delivery and thus provide new insights into developing naturally-equipped nanovehicles for oral drug administration.