PEI-assisted boronate affinity magnetic nanoparticle-based SELEX for efficient in vitro evolution of saponin-binding aptamers.

Saponin is a large family of important natural products with various pharmacological activities. Selective enrichment of saponin from complex biological samples is a key step for analysis of saponin. Despite that aptamers have been widely used for selective enrichment, aptamers that can specifically recognize saponins have never been reported. In this study, a facile and efficient SELEX approach was developed for in vitro evolution of saponin-binding aptamers, using PEI-assisted boronate affinity magnetic nanoparticles (p-BA-MNPs) that exhibit highly favorable binding properties as a general affinity platform. As a proof of the principle, ginsenoside Re and Rb1 were employed as two target saponins. Two aptamers towards each target saponin, with dissociation constant at the 10-5 M level, were selected within 6 rounds. An affinity magnetic nanoparticle was constructed by using the selected aptamer as a affinity ligand. The resulting material allowed for the quantitative analysis of ginsenoside Re in real samples with high reliability. The p-BA-MNPs based SELEX is straightforward and generally applicable for a wide range of target saponins, providing a promising aptamer evolution approach for aptamer-based research and pharmaceutical analysis.