The relaxivity observed after binding with LDL, due to the increase of the tumbling time of the macromolecular adduct, is high (ca 30 mM−1 s−1 at 20 MHz) and is able to generate a good contrast enhancement when internalized in tumour cells overexpressing LDL receptors as murine melanoma (B16-F10) cell line. Here, LDLR is linked to melanoma.