Incorporation of Boronic Acid into Aptamer-Based Molecularly Imprinted Hydrogels for Highly Specific Recognition of Adenosine

Molecularly imprinted polymers (MIPs) and aptamers are two types of molecular recognition strategies. We are interested in combining them to further improve specificity. Adenosine is a model analyte for developing aptamer-based biosensors, but the most commonly used DNA aptamer for adenosine can also bind deoxyadenosine with a similar affinity (K_a (adenosine)/K_a (deoxyadenosine) = 1.07). Since adenosine and deoxyadenosine differ by the former having a cis-diol, and boronic acid can bind cis-diol specifically, in this work, an acrydite-modified adenosine aptamer was copolymerized with a boronic acid containing monomer, 3-acrylamidophenylboronic acid (AAPBA) in the presence of adenosine as the template for imprinting. Isothermal titration calorimetry (ITC) and SYBR Green I staining were used to measure its binding. The AAPBA-containing aptamer-MIP exhibited a 115-fold high selectivity for adenosine against deoxyadenosine at pH 6.4, and 230-fold for adenosine against cytidine. We recently found that boronic acid containing hydrogels can nonspecifically adsorb DNA oligonucleotides and inhibit aptamer binding. The ribose in adenosine may interact with the boronic acid unit and decrease its inhibition effect to the aptamer in the MIP. However, for deoxyadenosine, it does not bear a cis-diol and thus cannot rescue the aptamer. This work provides insight into the combination of aptamers with other functional groups, which may further broaden applications in ways that free aptamers cannot achieve alone.