Boronic acid-functionalized materials have been the subject of increasing attention in recent years due to their capability in the facile selective extraction of glycoproteins. However, boronic acids are associated with weak binding affinity, and it is thereby difficult for boronate affinity materials to extract glycoproteins of low concentration. Here we present for the first time a boronate avidity material, dendrimeric boronic acid-functionalized magnetic nanoparticles, with significantly enhanced binding strength towards glycoproteins. Due to the dendrimer-assisted multivalent synergistic binding, the boronate avidity material exhibited dissociation constants of 10 À5 to 10 À6 M towards glycoproteins, which are 3-4 orders of magnitude higher than the affinities of single boronic acid binding. Such an avidity enabled the selective extraction of trace glycoproteins; an extractable concentration as low as 2 Â 10 À14 M was demonstrated. Meanwhile, the boronate avidity material was tolerant of the interference of abundant competing sugars. Moreover, the dendrimeric boronic acid-functionalized magnetic nanoparticles exhibited two additional advantages: high binding capacity and fast binding/ desorption speed. Due to these favourable features, the selective enrichment of trace glycoproteins by the boronate avidity material became not only possible but also efficient. Efficient enrichment of trace glycoproteins from human saliva was demonstrated. The dendrimer-assisted synergistic binding strategy is also applicable to other types of boronic acid-functionalized materials and other types of functionalized materials.

A benzoboroxole-functionalized monolithic column was synthesized, which exhibited the best specificity and affinity towards cis-diol containing biomolecules as compared with the boronate affinity monolithic columns reported as well as significant secondary separation capability under acidic conditions.

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The affinity of boronic acids to cis-diol-containing biomolecules has found wide applications in many fields, such as sensing, separation, drug delivery, and functional materials. A sound understanding of the binding interactions will greatly facilitate exquisite applications of this chemistry. Although a few analytical tools have been available for the characterization of the interactions, these techniques are associated with some apparent drawbacks, so they are only applicable to a limited range of boronic acids and cis-diol-containing biomolecules. Therefore, a widely applicable method is still greatly needed. In this work, an affinity capillary electrophoresis (ACE) method was established and validated to probe the interactions between boronic acids and cis-diol-containing biomolecules. The method was proven to be applicable to almost all types of cis-diol-containing biomolecules and boronic acids. Based on this method, a quantitative, comparative study on the interactions between 14 boronic acids that have important potentials for application with 5 typical monosaccharides of biological importance was carried out. The findings provided new insights into boronate affinity interactions, particularly the relationship between the binding strength with the molecular structures of the binding species. Besides, effects of pH and temperature on the binding strength were also investigated. This method exhibited several significant advantages, including (1) possibility of simultaneous study of multiple interactions, (2) low requirement on the purity of the binding species, (3) wide applicability, and (4) high accuracy and precision.

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