Adsorption of DNA Oligonucleotides by Boronic Acid-Functionalized Hydrogel Nanoparticles

Boronic acid-functionalized hydrogels were commonly used for covalent binding of cis-diol-contained molecules such as glucose, but noncovalent adsorption by boronic acids was less studied. DNA as an important polymer has been used to enhance the function of hydrogels including boronic acid-containing gels. In this work, noncovalent interactions between DNA oligonucleotides and boronic acid-containing hydrogel nanoparticles were studied in detail. The gels were composed of either poly(N-isopropylacrylamide) or with additional 5.6 mol % of 3-acrylamidophenylboronic acid (AAPBA). DNA adsorption on the AAPBA-containing gels was achieved with a high salt concentration, which can be explained by electrostatic repulsion between DNA and boronic acid. The critical role of boronic acid was confirmed by adding competing cis-diol-containing molecules such as glucose, fructose, and cytidine. Hydrogen bonding and hydrophobic interactions are important for DNA adsorption based on inhibited adsorption by urea and dimethyl sulfoxide. Polycytosine DNA showed a higher adsorption capacity compared to the other three types of DNA homopolymers. When T₁₅ and T₁₄-rU were compared, no covalent binding was detected for T₁₄-rU, suggesting that a single terminal diol was insufficient to support covalent binding at the low concentration of DNA used. Finally, the boronic acid-containing gels were able to adsorb an aptamer and inhibit its binding function. Binding was rescued by adding glucose to block the boronic acids. This study demonstrates noncovalent boronic acid interactions with DNA, and this information could be useful for designing and optimization of related biosensors and materials.