A HYBRID OF APTAMER-MOLECULARLY IMPRINTED POLYMER FOR HIGH-SPECIFICITY AND HIGH-AFFINITY RECOGNITION TOWARDS TARGET PROTEINS

Biomolecular recognition plays important roles in living systems. Reagents and materials for biomolecular recognition are important tools for life science studies and biomedical applications. Aptamers and molecularly imprinted polymers (MIPs) are two effective strategies to mimic the binding properties of antibodies. Although aptamers and MIPs can overcome some drawbacks of antibodies, they have their own advantages and disadvantages. For instance, aptamers are easy to synthesize once they are selected, sequenced and validated. However, aptamers are often associated with inadequate affinity and specificity due to their dynamic structures. MIPs may provide high affinity and specificity due to the presence of imprinted cavities with fixed 3D shape and functionality, but they highly depend on the effectiveness of the imprinting approach and functional monomer(s) used. A more advantageous strategy may be to combine aptamer with MIP to gain better affinity and specificity. Although a few attempts have been made in this direction, ^[1] such a strategy is worthy of being further explored. Herein, we present a new aptamer-MIP hybrid with improved affinity and specificity. The imprinting approach used herein was inspired by a facile and efficient method called boronate-affinity oriented surface imprinting we developed recently, in which a boronic acid was used as key ligand to anchor the template for oriented surface imprinting. ^[2] An aptamer that can recognize the glycoprotein alkaline phosphatase (ALP) with relative weak affinity and specificity was used as a key ligand, and oriented surface imprinting was carried out with in-water self-polymerization system of dopamine. A thin-layer of polydopamine was formed to cover the template to an appropriate thickness. After removing the template from the polymer, an aptamer-MIP hybrid with apparently improved affinity and specificity toward ALP was obtained, with cross-reactivity of 3.2~5.6% and a dissociation constant of 1.5 × 10⁻⁹ M. With this aptamer-MIP hybrid, a plasmonic immunosandwich assay (PISA)^[3] was developed for fast and sensitive detection of ALP in human serum.

References:

[1] Bai, W., Gariano, N. A., Spivak, D. A. (2013) Macromolecular amplification of binding response in superaptamer hydrogels. Am. Chem. Soc.135: 6977-6984.

[2] Xing, R., Wang, S., Bie, Z., He, H., Liu, Z. (2017) Preparation of molecularly imprinted polymers specific to glycoproteins, glycans and monosaccharides via boronate affinity controllable-oriented surface imprinting. Protoc.12: 964-987.

[3] Liu, J., Yin, D., Wang, S., Chen, H., Liu, Z. (2016) Probing low-copy-number proteins in a single living cell. Chem. Int. Ed. 55: 13215-13218.