Modification of curcumin-loaded liposome with edible compounds to enhance ability of crossing blood brain barrier

Abstract This research explored the potential of food grade sialic acid (SA), polymerized SA (PSA), and their oxidized form to conjugate with wheat germ agglutinin (WGA) on liposome to deliver curcumin to brain. Results showed that curcumin was entrapped in liposome with high encapsulation efficiency (90.77%) and the vector had a size of about 115 nm in diameter. The thermogravimetric analysis (TGA) confirmed the successful presence of SA and PSA in the lipid bilayers of liposomes. The TGA curves below 100 °C suggested that WGA acts as a protective layer for SA and PSA. In general, the liposomes modified by the un-oxidized SA or PSA could conjugate more WGA than that oxidized counterparts, and polymerization of SA did not increase WGA conjugation on the liposomes. More than 40% of WGA on the surface of modified liposomes remained after digestive enzymes challenge. The amide peaks at 1241 cm-1 and 533-581 cm-1 in the Fourier transform infrared (FTIR) spectrum of the modified liposomes indicated the covalent bonding between carboxyl group of SA and amine group of WGA. These characteristic peaks still existed after digestive enzymes challenge, demonstrating that the conjugation of WGA and SA on the modified liposome can resist the digestive enzymes to a certain extent. SEM images showed that the modified liposomes after digestive enzymes treatment were still spherical with clear rim, and the enzyme-treated vectors had a higher permeation rate crossing blood-brain barrier (BBB) endothelial cell monolayer than the un-modified liposome without enzyme treatment. This study demonstrates how the surface modification can enhance the function of liposome as a phytochemical carrier for brain disease.