Effect of Bovine Serum Albumin on the Stability of Bicalutamide-Encapsulated Lipid Nano-Emulsion in Bovine Serum

Aiming at the development of a stable drug carrier for bicalutamide (BT), we prepared various lipid nano-emulsions (LNEs) from a lipid mixture of soybean oil, phosphatidylcholine, sodium palmitate and sucrose palmitate (SP). These LNEs had mean particle size of approximately 50 nm and zeta potential (ζ) of -40 to -30 mV and were investigated their stability in saline solution and in bovine serum by using the dynamic light scattering method. In saline solution, while the droplet size of LNEs without and with BT reached more than 150 nm, that of the BT-encapsulated LNEs with SP could be maintained within 100 nm even after 24 h. In contrast, the droplet size of LNEs hardly increased even over 72 h placed in bovine serum, suggesting that bovine serum albumin (BSA) suppressed their coalescence. The intrinsic fluorescence of BSA was quenched and blue-shifted in the presence of LNE. In addition, the ζ values of all LNEs increased to around -20 mV according to the increase of BSA concentration. These results demonstrated that BSA interacted with LNE particles. Furthermore, the fluorescence resonance energy transfer using a fluorescence probe revealed that not only BT encapsulated in LNE particles but also SP strongly interacted with BSA.