Enhancing oral bioavailability of insulin through bilosomes: Implication of charge and chain length on apical sodium-dependent bile acid transporter (ASBT) uptake

This study investigates the impact of charge and chain length of bile salts in the bilosomes on the oral bioavailability of insulin (IN) by examining their uptake via the apical sodium-dependent bile acid transporter (ASBT). Deoxycholic acid bile salt was conjugated with different amino acids to create conjugates with varying charge and chain length, which were then embedded in liposomes. The resulting bilosomes had a particle size <400 nm, a PDI of 0.121 ± 0.03, and an entrapment efficiency of ∼70 %, while maintaining the chemical and conformational integrity of the loaded IN. Bilosomes also provided superior protection in biological fluids without compromising their biophysical attributes. Quantitative studies using the Caco-2 cell line demonstrated that anionic bilosomes were taken up more efficiently through ASBT than cationic bilosomes with 4- and 1.3-fold increase, respectively. Ex-vivo permeability studies corroborated these findings. In-vivo efficacy studies revealed a 1.6-fold increase in the AUC of IN with bilosomes compared to subcutaneous IN. The developed bilosomes were able to reduce blood glucose levels by ∼65 % at 6 h, with a cumulative hypoglycemic value of 35 % and a BAR of ∼30 %. These results suggest that ASBT can be a suitable target for improving the oral bioavailability of bilosomes containing IN.