Biomimetic Viruslike and Charge Reversible Nanoparticles to Sequentially Overcome Mucus and Epithelial Barriers for Oral Insulin Delivery.

Nanoparticles (NPs) for oral delivery of peptide/protein drugs are largely limited due to the coexistence of intestinal mucus and epithelial barriers. Sequentially overcoming these two barriers is intractable for a single nanovehicle due to the requirements of different or even contradictory surface properties of NPs. To solve this dilemma, a mucus-penetrating virus-inspired biomimetic NP with charge reversal ability (P-R8-Pho NPs) was developed by densely coating poly(lactic- co-glycolic acid) NPs with cationic octa-arginine (R8) peptide and specific anionic phosphoserine (Pho). The small size (81.81 nm) and viruslike neutral charged surface (-2.39 mV) of the biomimetic NPs achieved rapid mucus penetration, which was almost equal to that of the conventional PEGylated mucus-penetrating nanoparticles. The hydrolysis of surface-anchored anionic Pho was achieved by intestinal alkaline phosphatase, which led to the turnover of ζ potential to positive (+7.37 mV). This timely charge reversal behavior also exposed cationic R8 peptide and induced efficient cell-penetrating peptide (CPP)-mediated cellular uptake and transepithelial transport on Caco-2/E12 cocultured cell model. What's more, P-R8-Pho NPs showed excellent stability in simulated gastrointestinal conditions and enhanced absorption in intestine in vivo. Finally, oral administration of insulin-loaded P-R8-Pho NPs enabled to induce a preferable hypoglycemic effect and a 1.9-fold higher oral bioavailability was achieved compared with single CPP-modified P-R8 NPs on diabetic rats. The combinative application of biomimetic mucus-penetrating strategy and enzyme-responsive charge reversal strategy in a single nanovehicle could sequentially overcome mucus and epithelial barriers, thus showing great potential for the oral peptide/protein delivery.