Phenolic compounds offer health-promoting functions, but they suffer from low bioavailability. Bilosomes (bile salt-containing liposomes) have the potential to improve the bioavailability of encapsulated phenolic compounds for oral administration. The hypothesis of this thesis is that incorporating bile salts into self-assembled vesicles can enhance the bioavailability of phenolic compounds. This thesis focuses on investigating the effects of bilayer modification with sodium cholate (NaC) and surface modifications using chitosan (CH) and polygalacturonic acid (PGA), on the physicochemical properties and stability of the lipid bilayer under various conditions. Additionally, it examines behaviours of the modified bilayers during simulated digestion, the bioaccessibility, and absorption of encapsulated trans-resveratrol (t-res), a model phenolic compound, with/without a food matrix.
The incorporation of NaC into the lipid bilayers and the biopolymer coating strongly affected the physical properties of the bilayers. Liposomes and bilosomes showed high stability at different pH, during thermal treatment, and during storage. Despite some challenges (pKa and swelling properties of biopolymers), biopolymer-coated bilosomes exhibited good stability and protected the encapsulated t-res. While the incorporation of NaC increased the bioaccessibility of t-res from 40% to 83-90%, it was ~20% and ~40% for CH-coated and PGA/CH-coated bilosomes, respectively. The bioaccessibility increased significantly when t-res, liposomes, and bilosomes were digested with oat milk. For the absorption of samples, t-res concentration in the basolateral chamber at 2 hours for free t-res, liposomes, and bilosomes ranged from 0.379 μM to 0.487 μM. Accumulated t-res in tissue, ready for absorption, reached remarkably 3.345 μM and 16.801 μM with the incorporation of 10 mM and 7.5 mM NaC into the bilayers, respectively.
In conclusion, bilosomes provided stability and enhanced bioaccessibility and absorption of t-res, consequently enhancing bioavailability, compared to the liposomes. For food applications, while bilosomes are promising for intestine-targeted oral delivery of phenolic compounds, biopolymer-coated bilosomes have the potential for colon-targeted oral delivery.
