SAXS experiment for fluorophore and LDL association

A new fluorophore is currently under development for fluorescence-guided surgery. This contrast agent 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). We are now wondering where/how the contrast agent and the LDL interact: is the contrast agent at the interphase with the shell or with the core or the LDL? Is it associated with a specific part of the LDL?