Selection and verification of ssDNA aptamers to Sialyl LewisX by SELEX technique

Abstract

Objective To set up a method to obtain single-stranded DNA aptamers of Sialyl LewisX in vitro by SELEX technique and lay a foundation of application of these aptamers to metastasis of carcinoma in early diagnosis and targeted therapy. Methods A single-stranded DNA library containing 30 random sequences was constructed, at a length of 70nt. Chost cyanogen bromide (CNBr)-activated agarose beads served as screening medium,and the ssDNA aptamers of slex were obtained by SELEX technique.The aptamers were cloned and sequenced, and DNAMAN package was employed to analyze the conserved equences and the second structure of the aptamers. The affinity of aptamers to slex was determined by chro-matic biotin-streptavidin-horseradisb peroxides system. Results Through screening aptamers round by round, the affinity of aptamers to slex was increased gradually (the absorbance values were increased from 0.145 to 0.560). Most aptamers had the correct length and fix-sequence after cloning and sequencing.Conclusion After selection of 9 rounds, the ssDNA aptamers we obtained had high specificity and affinity to slex in vitro. Key words: Sialyl LewisX; Aptamers; Clone