Fluorescence-labeled liposome accumulation in injured colon of a mouse model of T-cell transfer-mediated inflammatory bowel disease.

Drug delivery systems maximize the efficacy of drugs by improving their pharmacokinetic profiles, pharmacodynamic effects, or both and reducing their adverse effects. One of the most advanced, clinically available formulations are liposome-encapsulated drugs. In this study, we aimed to determine if liposomes can selectively deliver compounds in gastrointestinal diseases. Initially, we evaluated the correlation between the diarrhea score and accumulation of fluorescence (FL)-labeled liposome using in vivo imaging systems in various disease states of an inflammatory bowel disease mouse model. The result showed that FL-labeled liposome accumulation and colon tissue weight, which reflect the disease state were highly and positively correlated. Then, to confirm the accumulation of liposomes at injured sites of the colon, we administered both FL-labeled liposomes and luminescence probes for detecting reactive oxygen species (ROS) to the mouse model. The imaging data showed that liposome accumulation tended to coincide with ROS detected sites and the correlation coefficient indicated a significantly positive correlation between liposome accumulation and ROS detection levels. Finally, we evaluated the involvement of macrophages in the uptake mechanism of the liposomes by analyzing the relationship between FL-labeled liposome accumulation and macrophage marker gene expression levels. The result showed that the expression of each macrophage marker gene and liposome accumulation showed a significant positive correlation. Therefore, the macrophages considerably contributed to the uptake mechanism of the liposomes. These data suggest that liposomes could be an attractive delivery tool for enhancing the accumulation of drug candidates through macrophages in injured colonic tissues. This approach is expected to provide new treatment options for patients with colitis.