Theconjugation of CA-SF, containing the sulfamido group able to bindthe enzyme active site, to a Gd-complex offers two significant advantages:it allows the observation of biodistribution using MRI and enhanceshydrophilicity, leading to improved solubility in aqueous environments.The biological evaluation demonstrated that Gd-B-CA-SF selectivelytargets cancer cells, particularly those overexpressing CA IX, whilesparing healthy cells. The gene discussed is CA9; the disease is cancer.