A liposome containing encapsulated bovine serum albumin (BSA-liposome) was developed for use as a hydrophobic carrier in which hydrophobic drugs are encapsulated into the inner aqueous core of the liposome by binding to BSA. We prepared a tacrolimus (TAC)-loaded BSA-liposome (TAC-BSA-liposome) and investigated the efficiency of delivery of the encapsulated hydrophobic drug using experimental colitis model mice induced by dextran sulfate sodium (DSS). The encapsulation efficiency of TAC was dramatically increased when the BSA-liposome was used compared to an ordinary liposome (without BSA) because of the increased water solubility of TAC as the result of its binding to BSA. In in vivo biodistribution tests in DSS-induced colitis model mice, the BSA-liposome passively targeted inflammatory lesions in the colon by virtue of the well-regulated physicochemical properties (size and PEGylation) of the BSA-liposome, which is due to the enhanced permeability and retention effect. Furthermore, the intravenous administration of TAC-BSA-liposome exerted therapeutic effects against colitis in DSS-induced colitis model mice, indicating that the BSA-liposome functions as a TAC carrier in vivo. These results suggest that the BSA-liposome has the potential for delivering many kinds of albumin-bound hydrophobic drugs to inflammatory lesions or tumor sites by virtue of the enhanced permeability retention effect.
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