Branched polyethyleneimine-assisted 3-carboxybenzoboroxole improved Wulff-type boronic acid functionalized magnetic nanoparticles for the specific capture of cis-diol-containing flavonoids under neutral conditions.

Flavonoids have shown a variety of biological activities such as antimicrobial, antibacterial, antifungal, antiviral, antiinflammatory, antitumor, antiatherogenic, and antihyperglycemic activities. A lot of important flavonoids contain cis-diols such as rutin (Ru), quercetin (Qu), luteolin (Lu), myricetin (Myr) and baicalein (Ba) and so on. It is necessary to establish a simple, low-cost and efficient purification method for cis-diol-containing flavonoids from plant extracts. Boronate affinity materials are able to reversibly bind the cis-diols via boronic acids by forming a five- or six-membered boronic cyclic ester in aqueous media. However, conventional boronate affinity materials have to be used in alkaline media, which can lead to the oxidation of cis-diols in compounds. In this study, the polyethyleneimine (PEI)-assisted 3-carboxybenzoboroxole-functionalized magnetic nanoparticles (MNPs) were prepared to achieve efficient capture of cis-diol-containing flavonoids under neutral conditions. Branched PEI was applied as a scaffold to amplify the number of boronic acid moieties, while 3-carboxybenzoboroxole, exhibiting high affinity and excellent water solubility toward flavonoids, was used as an affinity ligand. The prepared boronate affinity MNPs exhibited high binding capacity and fast binding kinetics (equilibrium in 3 min) under neutral conditions. In addition, the obtained boronate affinity MNPs exhibited high binding affinity (K d ≈ 10-4 M), low binding pH (pH ≥ 6.0) and tolerance of the interference to abundant sugars.

Efficient vitamin B12-imprinted boronate affinity magnetic nanoparticles for the specific capture of vitamin B12.

Vitamin B12 (VB12) has an important function in human physiology. However, analysis of VB12 at natural levels in foods or biological samples is difficult because of its very low concentration level and the presence of high-abundance components which can interfere with the measuring system. Thus, it is essential to develop efficient and selective enrichment approaches for VB12. Molecularly imprinted polymers (MIPs) have important applications from separation and sensing to catalysis. However, there is no report on the preparation of MIPs for VB12. Here, we use boronate affinity-based oriented surface imprinting to prepare MIPs for VB12. A VB12 template was first covalently immobilized onto the surface of boronic acid functionalized magnetic nanoparticles. Subsequently, a thin imprinting coating of poly(2-anilinoethanol) was formed to cover the substrate surface via in-water polymerization. After removing the template, 3D cavities complementary to the molecular size and shape of the template were formed in the imprinting layer. The imprinting coating was highly hydrophilic and presented limited residual boronic acid, thus non-specific binding was avoided. The prepared MIPs exhibited several highly favorable features, including excellent specificity, high binding strength and low binding pH. The prepared MIPs were successfully applied to the analysis of VB12 in human milk.