Albumin is a common endogenous protein which is relatively easy to chemically modify. In the past, we were interested in targeting asialoglycoprotein receptors to evaluate the liver function. Using SPECT1 and optical imaging2, we observed a fast accumulation in the liver starting after 2 minutes while no accumulation was observed for the non-targeted albumin. We also confirmed that mostly ASGR cells were targeted, and not Kupffer cells. Using the same chemistry, we were interested in the application of a new bioconjugate to imaging-guided surgery. In order to enhance the visualization of tumor margins, we developed a new imaging probe composed of human serum albumin linked to the Sialyl Lewis X ligand3 and Cyanine 5 to target E-selectin. The bioconjugate obtained was characterized using size exclusion liquid chromatography and mass spectrometry in order to demonstrate the effective grafting of the ligands and the colloidal stability of the protein4. The in vitro and in vivo evaluation of the S-Cyal compound proved the interest of the active targeting and the usefulness of the probe in a context of tumor resection. 1doi: 10.1021/bc900275f; 2doi: 10.1039/c8nr04163f; 3doi: 10.1016/j.carres.2013.11.012; 4doi: 10.1016/j.nano.2019.02.011