Solid-phase synthesis of molecularly imprinted polymer nanolabels: Affinity tools for cellular bioimaging of glycans

Paulina X Medina Rangel,Jingjing Xu,José Kovensky,Sylvain Laclef,Karsten Haupt,Bernadette Tse Sum Bui,Maria Panagiotopoulou

doi:10.1038/s41598-019-40348-5

Abstract

Hyaluronic acid (HA) is a glycosaminoglycan that plays many roles in health and disease and is a key biomarker of certain cancers. Therefore, its detection at an early stage, by histochemical methods, is of importance. However, intracellular HA can be masked by other HA-binding macromolecules, rendering its visualization somehow problematic. We show that fluorescent molecularly imprinted polymer nanogels (MIP-NPs), can localize and detect intracellular HA. MIP-NPs were synthesized by solid-phase synthesis on glass beads (GBs). GBs were functionalized with terminal alkyne groups on which an azide derivative of the template molecule glucuronic acid was immobilized via click chemistry. Immobilization via the anomeric carbon left the template’s carboxyl moiety free to enable strong stoichiometric electrostatic interactions with a benzamidine-based functional monomer, to confer selective recognition to the MIP-NPs. Due to the two-point orientation of the template, the resulting MIP-NPs were endowed with improved binding site homogeneity and specificity, reminiscent of monoclonal antibodies. These synthetic antibodies were then applied for probing and staining HA, of which glucuronic acid is a substructure (epitope), on human epidermal cells. Their excellent sensitivity, small size and water compatibility, enabled the MIP-NPs to visualize HA, as evidenced by confocal fluorescence micrographs.

Highlights

Imprinted polymers (MIPs) are tailor-made antibody mimics obtained by a templating process at the molecular level[1,2,3]
Since imprinting small molecules by the solid phase approach requires that the template be immobilized on the solid support without involving the functional groups that can be exploited for recognition properties, an alkyne or azide equivalent can be a useful alternative for its immobilization on solid support without compromising the accessibility of the functional groups for the imprinting process
The anomeric carbon can be conveniently used to attach the coupling group. This strategy is employed for the first time to immobilize a template molecule for the obtention of molecularly imprinted polymer nanogels (MIP-NPs) using solid-phase synthesis

Summary

Introduction

Imprinted polymers (MIPs) are tailor-made antibody mimics obtained by a templating process at the molecular level[1,2,3] They are synthesized by copolymerizing functional and cross-linking monomers around a template molecule. The main drawbacks is their non-compatibility with water, their incomplete template removal and the non-homogeneity of their binding sites To overcome these problems, the recently-developed solid-phase synthesis approach in which the template is covalently immobilized on glass beads (GBs) as solid support, has emerged as a promising solution[17,18]. The recently-developed solid-phase synthesis approach in which the template is covalently immobilized on glass beads (GBs) as solid support, has emerged as a promising solution[17,18] This configuration can allow an oriented immobilization of the template upon which MIP-NPs are synthesized[19,20,21]. In order to confer high selectivity to the MIP, a functional monomer bearing a benzamidine moiety, (4-acrylamidophenyl) (amino)methaniminium acetate (AB), which forms very strong electrostatic interactions in a 1:1 stoichiometry with the –COOH moiety of the template[15]

Methods

Results

Conclusion