Determination of cis-diol-containing flavonoids in real samples using boronate affinity quantum dots coated with imprinted silica based on controllable oriented surface imprinting approach.

Novel boronate affinity imprinted quantum dots (BA-CdTe@MIPs QDs) were used to develop a selective and sensitive fluorescent nanosensor for determination of cis-diol-containing flavonoids such as quercetin (Qu), baicalein (Bai) and luteolin (Lut) based on controllable oriented surface imprinting approach. The boronate affinity imprinted silica was used as recognition elements. Under the optimum conditions, the imprinting factor (IF) for Qu, Bai and Lut was evaluated to be 9.42, 6.58 and 10.91, respectively. The results indicated that the boronate affinity quantum dots coated with imprinted silica were successfully prepared. The obtained BA-CdTe@MIPs QDs provided high selectivity and high sensitivity for cis-diol-containing flavonoids such as quercetin and luteolin. The BA-CdTe@MIPs QDs exhibited linear decrease in fluorescence intensity with the increase of concentration of quercetin in the 0.05-25 µM concentration range. The detection limit (LOD) is evaluated to be 0.02 µM. The obtained fluorescent nanosensor could be successfully applied to efficient detection of cis-diol-containing flavonoids in onion skin and human urine samples. The recoveries for the spiked onion skin and urine samples were evaluated to be 83.50-104.00% and 86.67-105.00%, respectively. Clearly, this study provides a rapid and efficient fluorescent detection tool for cis-diol-containing flavonoids in real samples.

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.