deciphering Lipoprotein-azaBODIPY interaction

New fluorophores are currently under development for fluorescence-guided surgery. Some of these contrast agents spontaneously accumulated in some tumor types, but almost failed to accumulated in other ones. To understand the tumor accumulation mechanism, we designed a study which indicated a strong association of the contrast agent with lipoproteins and more particularly with low density lipoprotein (LDL) but also with high density lipoproteins (HDL), leading to a fluorescence boost and potentially to tumor accumulation.
We are now wondering where/how the fluorophore and the LDL interact: is the fluorophore at the interphase with the shell or with the core or the LDL? Is it associated with a specific part of the LDL? Which part: cholesterol, apolipoprotein, other?