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Riboflavin (vitamin B2), a cis-diol-containing compound, is an essential vitamin for maintaining human health mainly in energy metabolism and is a critical component of enzyme cofactors and flavoproteins. Thus, the determination of riboflavin in food products is essential in riboflavin-fortified foods. However, analysis of riboflavin at natural levels in foods or biological samples is difficult because of its very low concentration level and the presence of undesirable matrix effects which could interfere with the measuring system. Thus, it is essential to develop efficient and selective enrichment approaches for riboflavin. Molecularly imprinted polymers can be well used for riboflavin extraction and pre-concentration from food samples. In this study, we present riboflavin-imprinted magnetic nanoparticles as an ideal sorbent for the selective enrichment of riboflavin followed by direct fluorometric determination. The riboflavin-imprinted magnetic nanoparticles were prepared according to a newly reported strategy, called boronate affinity-based surface initiated imprinting. Magnetic nanoparticles and vinylphenylboronic acid were used as supporting materials and a functional monomer, respectively. The prepared riboflavin-imprinted magnetic nanoparticles exhibited several significant advantages, such as excellent selectivity, high binding affinity and low binding pH toward riboflavin, which made the molecularly imprinted material become an ideal sorbent for the selective enrichment of riboflavin. The prepared riboflavin-imprinted magnetic nanoparticles were successfully applied to the analysis of riboflavin in milk. [ABSTRACT FROM AUTHOR]

Boronate affinity materials, as efficient sorbents for extraction, separation and enrichment of glycoproteins, have attracted more and more attention in recent years. However, conventional boronate affinity materials suffer from low binding affinity due to the use of single boronic acids, which makes the extraction of glycoproteins in trace concentration rather difficult or impossible. Here we present a type of high boronate avidity material, polyethyleneimine (PEI)-assisted boronic acid-functionalized magnetic nanoparticles (MNPs). Branched PEI was used as a scaffold to amplify the number of boronic acid moieties, while 2,4-difluoro-3-formyl-phenylboronic acid (DFFPBA), exhibiting high affinity and excellent water solubility toward cis-diol-containing compounds, was employed as an affinity ligand. Due to the PEI-assisted synergistic multivalent binding, the boronate avidity MNPs exhibited a high binding affinity toward glycoproteins with dissociation constants of 10−6–10−7 M, which was the highest among the reported boronic acid-functionalized materials that can be applied for a glycoproteomic analysis. Such an avidity enabled the selective extraction of trace glycoproteins as low as 2 × 10−15 M. This feature greatly favored the selective enrichment of trace glycoproteins from real samples. Meanwhile, the boronate avidity MNPs were tolerant to the interference of abundant sugars. In addition, the PEI-based boronate avidity MNPs exhibited high binding capacity and low binding pH. The feasibility for practical applications was demonstrated with the selective enrichment of trace glycoproteins in human saliva. [ABSTRACT FROM AUTHOR]