Synthesis of three fluorescent boronic acid sensors for tumor marker Sialyl Lewis X in cancer diagnosis

Sialyl Lewis X (sLex) is a carbohydrate that is considered not only a marker for cancer, but also an antigen associated with the malignant behavior of cancerous cells. We have synthesized three fluorescent boronic acid sensors as potential sensors for sLex. Photoinduced electron transfer by a fluorescence analyzer was used to assess sensor-sLex antigen binding. The reaction was carried out in mixed aqueous solution, and Sensor 3 was identified as showing the strongest fluorescence enhancement upon binding to sLex at 10 nM. In cell-line culture experiments, Sensor 1 was shown to label sLex expression positively for HepG2, Colo 205, and COS-7 cells, and negatively for MDA-MB-231 cells; Sensor 2 did so positively for HepG2, PLC/PRF/5, and Colo 205 cells, and negatively for MDA-MB-231 and COS7 cells; and Sensor 3 did so positively for PLC/PRF/5 and HepG2 cells, and negatively for MDA-MD-231 and COS7 cells. MTT cytotoxicity experiment results showed that the three sensors are nontoxic, and Hoechst 33258 experiments showed that no apoptosis occurred.