β-Lactoglobulin stabilized lipid nanoparticles enhance oral absorption of insulin by slowing down lipolysis

Lipid-based nanocarriers have staged a remarkable comeback in the oral delivery of proteins and peptides, but delivery efficiency is compromised by lipolysis. β-Lactoglobulin (β-lg) stabilized lipid nanoparticles, including nanoemulsions (NE@β-lg) and nanocapsules (NC@β-lg), were developed to enhance the oral absorption of insulin by slowing down lipolysis due to the protection from β-lg. Cremophor EL stabilized nanoemulsions (NE@Cre-EL) were prepared and set as a control. The lipid nanoparticles produced mild and sustained hypoglycemic effects, amounting to oral bioavailability of 3.0% ± 0.3%, 7.0% ± 1.1%, and 7.7% ± 0.8% for NE@Cre-EL, NE@β-lg, and NC@β-lg, respectively. Aggregation-caused quenching (ACQ) probes enabled the identification of intact nanoparticles, which were used to investigate the in vivo and intracellular fates of the lipid nanoparticles. In vitro digestion/lipolysis and ex vivo imaging confirmed delayed lipolysis from β-lg stabilized lipid nanoparticles. NC@β-lg was more resistant to intestinal lipolysis than NE@β-lg due to the Ca2+-induced crosslinking. Live imaging revealed the transepithelial transport of intact nanoparticles and their accumulation in the liver. Cellular studies confirmed the uptake of intact nanoparticles. Slowing down lipolysis via food proteins represents a good strategy to enhance the oral absorption of lipid nanoparticles and thus co-formulated biomacromolecules.