PTK7 and leukemia: Niu et al. reported the synthesis of a bioconjugate (50, Figure 32) in which an NHC gold(I) complex has been linked to the sgc8c aptamer, which can selectively recognise CCRF-CEM leukaemia cells binding the protein tyrosine kinase 7(PTK-7), more abundantly expressed in cancer cells surface than in healthy ones [133].