Supramolecular interaction of labetalol with cucurbit[7]uril for its sensitive fluorescence detection

This work studied the host-guest interaction between cucurbit[7]uril (CB[7]) and labetalol in acidic aqueous solution and proposed a simple competitive method for fluorescence detection of labetalol. The binding constant of labetalol-CB[7] was (1.83 ± 0.22) × 10(6) M(-1), which was greater than those of palmatine-CB[7], berberine-CB[7], and coptisine-CB[7] complexes. The fluorescence intensity of palmatine-CB[7], berberine-CB[7], and coptisine-CB[7] complexes decreased linearly with increasing concentration of labetalol ranging from 0.014 to 2.06, 0.014 to 1.15, and 0.034 to 1.23 μM, respectively. Based on the competitive interaction, the proposed detection method for labetalol showed limits of detection of 4.9 nM, 4.9 nM, and 12.0 nM, respectively, and was successfully applied for the determination of labetalol in human urine samples with good precision and recoveries from 95.4% to 102.5%. Moreover, it could be employed to monitor the time-dependent concentration of labetalol in urine from a healthy volunteer after oral medication. The superstructure-based competitive mode provided a promising fluorescence assay strategy for various potential applications.