Sialic acid (SA) is overexpressed on cell membranes of tumor cells, and increased serum SA concentration has been observed in tumor-bearing patients. Herein, a series of lanthanide-containing bimetallic complexes (TDA-M-Lns) for targeting SA were prepared via coordination among luminescent lanthanide ions (Ln3+ = Tb3+, Eu3+, Dy3+, or Sm3+), metal ion quenchers (M2+ = Cu2+ or Co2+), and the organic ligand 2,2'-thiodiacetic acid (TDA). SA can competitively coordinate with Ln3+, resulting in the "signal-on" of the Ln3+. Therefore, the TDA-M-Lns can be simply used for cost-saving detection of SA in the blood samples. Among the TDA-M-Lns, TDA-Co-Eu showed the highest sensitivity to detect SA in the blood of tumor-bearing mice. Furthermore, the TDA-Co-Eu was successfully used to target SA and deposit Eu3+ on the surfaces of tumor cells for the inhibition of tumor cell growth and migration. The therapeutic effect of TDA-Co-Eu on a Balb/c mouse liver tumor model was evaluated. It was proved that TDA-Co-Eu can be applied for SA detection as well as for inhibiting tumor growth.
Keywords: cell migration; coordination polymer; lanthanide complexes; luminescent sensing; sialic acid.