Salt‐Toggled Capture Selection of Uric Acid Binding Aptamers

Abstract

Uric acid is the end‐product of purine metabolism in humans and an important biomarker for many diseases. To achieve the detection of uric acid without using enzymes, we previously selected a DNA aptamer for uric acid with a Kd of 1 μM but the aptamer required multiple Na+ ions for binding. Saturated binding was achieved with around 700 mM Na+ and the binding at the physiological condition was much weaker. In this work, a new selection was performed by alternating Mg2+‐containing buffers with Na+ and Li+. After 13 rounds of selection, a new aptamer sequence named UA‐Mg‐1 was obtained. Isothermal titration calorimetry confirmed aptamer binding in both selection buffers, and the Kd was around 8 μM. The binding of UA‐Mg‐1 to UA required only Mg2+. This is an indicator of successful switching of metal dependency via the salt‐toggled selection method. The UA‐Mg‐1 aptamer was engineered into a fluorescent biosensor based on the strand‐displacement assay with a limit of detection of 0.5 μM uric acid in the selection buffer. Finally, comparison with the previously reported Na+‐dependent aptamer and a xanthine/uric acid riboswitch was also made.

Adsorption of DNA and Aptamers to Sodium Urate Crystals and Inhibition of Crystal Growth

“…At present, research on DNA oligonucleotides and gout mainly focuses on the binding of DNA and UA but pays little attention to the role of DNA in the growth of urate crystals. Aptamers are single-stranded nucleic acids that can selectively bind target molecules. , A few UA binding aptamers have been obtained by systematic evolution of ligands by exponential enrichment (SELEX), mainly for the establishment of biosensors to detect UA. , In this work, we explored the effects of UA aptamers and a random DNA (rDNA) on sodium urate crystallization and also studied the adsorption and desorption of DNA, providing a basis for potential applications of DNA in gout treatment.…”