A novel dual-recognition fluorescent biosensor for sialyl-Lewis^x sensitive detection

Sialyl-Lewis^x (SLe^x) is a tetrasugar, which plays an important role in initial inflammation and cancer cell metastasis, and can be used as a marker for cancer diagnosis and prognosis or a therapeutic target. Detecting SLe^x from complex biological media remains a significant challenge. Herein, a single-stranded DNA aptamer of SLe^x was screened based on the double-stranded DNA library-modified magnetic bead (MB)-SELEX technology. After 14 rounds of screening, 12,639 sequences were obtained and divided into nine families. Three representative sequences were selected based on the number of sequence repeats and Gibbs binding free energy, and the aptamer SLe^x-Apt2 with 80 nt length (K_d = 23.01 nM) had the best affinity and relatively high specificity for targeting SLe^x. Then, a novel dual-recognition fluorescent biosensor for SLe^x-sensitive detection based on aptamer SLe^x-Apt2 bio-dots and 3-aminobenzoboric acid-modified MB was developed. This method can detect SLe^x as low as 32 μM and has a good linear response in the range 100 μM to 2 mM. It has the advantages of low preparation cost, good targeting, and avoiding the occurrence of false-positive and false-negative detection results, which makes the biosensor more valuable in biological detection and clinical diagnosis.