Search

Teicoplanin has been banned in the veterinary field due to the drug resistance of antibiotics. However, teicoplanin residue from the antibiotic abuse of humans and animals poses a threat to people's health. Therefore, it is necessary to develop an efficient way for the highly accurate and reliable detection of teicoplanin from humans, food, and water. In this study, novel imprinted quantum dots of teicoplanin were prepared based on boronate affinity-based precisely controlled surface imprinting. The imprinting factor (IF) for teicoplanin was evaluated and reached a high value of 6.51. The results showed excellent sensitivity and selectivity towards teicoplanin. The relative fluorescence intensity was inversely proportional to the concentration of teicoplanin, in the range of 1.0–17 μM. And its limit of detection (LOD) was obtained as 0.714 μM. The fluorescence quenching process was mainly controlled by a static quenching mechanism via the non-radiative electron-transfer process between QDs and the five-membered cyclic boronate esters. The recoveries for the spiked urine, milk, and water samples ranged from 95.33 to 104.17%, 91.83 to 97.33, and 94.22 to 106.67%, respectively. [ABSTRACT FROM AUTHOR]

Ellagic acid (EA) is a natural polyphenol and possesses excellent in vivo bioactivity and antioxidant behaviors, which play an important role in the treatment of oxidative stress-related diseases, such as cancer. Additionally, EA is also known as a skin-whitening ingredient. The content of EA would determine its efficacy. Therefore, the accurate analysis of EA content can provide more information for the scientific consumption of EA-rich foods and cosmetics. Nevertheless, the analysis of EA in these samples is challenging due to the low concentration level and the presence of interfering components with high abundance. Molecularly imprinted polymers are highly efficient pretreatment materials in achieving specific recognition of target molecules. However, the traditional template molecule (EA) could not be absolutely removed. Hence, template leakage continues to occur during the sample preparation process, leading to a lack of accuracy in the quantification of EA in actual samples, particularly for trace analytes. In addition, another drawback of EA as an imprinting template is that EA possesses poor solubility and a high price. Gallic acid (GA), called dummy templates, was employed for the synthesis of MIPs as a solution to these challenges. The approach used in this study was boronate affinity-based oriented surface imprinting. The prepared dummy-imprinted nanoparticles exhibited several significant advantages, such as good specificity, high binding affinity ((4.89 ± 0.46) × 10−5 M), high binding capacity (6.56 ± 0.35 mg/g), fast kinetics (6 min), and low binding pH (pH 5.0) toward EA. The reproducibility of the dummy-imprinted nanoparticles was satisfactory. The dummy-imprinted nanoparticles could still be reused even after six adsorption–desorption cycles. In addition, the recoveries of the proposed method for EA at three spiked levels of analysis in strawberry and pineapple were 91.0–106.8% and 93.8–104.0%, respectively, which indicated the successful application to real samples. [ABSTRACT FROM AUTHOR]

A novel class of imprinted quantum dots as fluorescent nanosensors were prepared based on boronate affinity-based template-immobilization surface imprinting for detection of isoquercitrin (Isq). The obtained molecularly imprinted silica coating was used as the recognition element. The quantum dots were used as signal-transduction materials. Under optimum conditions, according to the fluorescence quenching of imprinted APBA-functionalized CdTe QDs by Isq, the imprinting factor (IF) for Isq was evaluated to be 1.69. This result suggests that boronic acid-functionalized quantum dots coated with molecularly imprinted silica were successfully prepared. The prepared isoquercitrin-imprinted APBA-functionalized CdTe QDs exhibited high sensitivity and selectivity toward isoquercitrin. The isoquercitrin-imprinted CdTe QDs exhibited linear fluorescence quenching toward isoquercitrin within the range of 0.20–30 μM. And the detection limit was found to be 0.09 μM. In addition, this study also provides an efficient fluorescence detection method of other cis-diol-containing flavonoids in samples. This method may find widespread use for monitoring of trace flavonoid drugs owing to its advantages of simple preparation, low cost, high sensitivity, good stability and reproducibility. [ABSTRACT FROM AUTHOR]

Catecholamines, a class of cis-diol-containing compounds, play a major role in the central nervous system. Meanwhile, catecholamines can be used as specific markers for some diseases in clinical diagnostics. Thus, it is important to determine catecholamines in real samples such as serum, plasma and urine. However, direct analysis of catecholamines in these samples is quite difficult because of their very low concentration level and the presence of undesirable matrix effects. It is essential to develop highly efficient extraction materials for the selective enrichment of catecholamines. Molecularly imprinted polymers have been well used for the selective enrichment for various kinds of molecules. In this study, we have developed dopamine-imprinted magnetic nanoparticles for selective enrichment of dopamine, followed by direct absorbance determination. The dopamine-imprinted magnetic nanoparticles were prepared according to boronate affinity-based surface imprinting. Magnetic nanoparticles and boronic acid ligands were used as supporting materials and functional monomers, respectively. The prepared dopamine-imprinted magnetic nanoparticles exhibited several significant advantages, such as good specificity, high binding affinity and low binding pH toward dopamine, which made the imprinted material become an ideal sorbent for highly specific enrichment of dopamine. The prepared dopamine-imprinted magnetic nanoparticles were successfully applied to the analysis of dopamine in human urine. [ABSTRACT FROM AUTHOR]

Chlorogenic acid (CGA), a cis-diol-containing compound, can exhibit anti-inflammatory, antiviral, antimicrobial and anti-oxidation properties. Thus, it is essential to determine CGA in food products. However, analysis of CGA at natural levels in food products 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 determining CGA. Molecularly imprinted polymers can be well used for the selective enrichment of CGA from food samples. In this study, we utilized CGA-imprinted magnetic nanoparticles as an ideal sorbent for selective enrichment of CGA followed by direct absorbance determination. The CGA-imprinted magnetic nanoparticles were prepared according to a newly reported strategy, called boronate affinity-based oriented surface imprinting. Magnetic nanoparticles and boronic acid ligands were used as supporting materials and functional monomers, respectively. The prepared CGA-imprinted magnetic nanoparticles exhibited several significant advantages, such as good specificity, high binding affinity and low binding pH toward CGA, which made the molecularly imprinted material an ideal sorbent for selective enrichment of CGA. The prepared CGA-imprinted magnetic nanoparticles were successfully applied to the analysis of CGA in fruit juices. [ABSTRACT FROM AUTHOR]

Abstract 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. Highlights • Vitamin B12-imprinted magnetic nanoparticles were prepared by surface imprinting. • A hydrophilic imprinting coating was formed by polymerization of 2-anilinoethanol. • The prepared MIPs exhibited excellent specificity and high binding strength. • The prepared MIPs were successfully applied to the analysis of VB12 in human milk. [ABSTRACT FROM AUTHOR]

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]

The binding of isorhamnetin to bovine liver catalase (BLC) was first investigated at 302, 310 and 318 K at pH 7.4 using spectroscopic methods including fluorescence spectra, circular dichroism (CD) and UV-vis absorption. Spectrophotometric observations are rationalized mainly in terms of a static quenching process. The binding constants and binding sites were evaluated by fluorescence quenching methods. Enzymatic activity of BLC in the absence and presence of isorhamnetin was measured using a UV/vis spectrophotometer. The result revealed that the binding of isorhamnetin to BLC led to a reduction in the activity of BLC. The positive entropy change and enthalpy change indicated that the interaction of isorhamnetin with BLC was mainly driven by hydrophobic forces. The distance r between the donor (BLC) and acceptor (isorhamnetin) was estimated to be 2.99 nm according to fluorescence resonance energy transfer. Fluorescence, synchronous fluorescence, and CD spectra showed no obvious change in the conformation of BLC upon the binding of isorhamnetin. In addition, the influence of pH on the binding of isorhamnetin to BLC was investigated and the binding ability of the drug to BLC deceased under other pH conditions (pH 9.0, 6.5, 5.0, 3.5, or 2.0) as compared with that at pH 7.4. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Boronate affinity materials, as unique sorbents, have emerged as important media for the selective separation and molecular recognition of cis-diol-containing compounds. With the introduction of boronic acid functionality, boronate affinity materials exhibit several significant advantages, including broad-spectrum selectivity, reversible covalent binding, pH-controlled capture/release, fast association/desorption kinetics, and good compatibility with mass spectrometry. Because cis-diol-containing biomolecules, including nucleosides, saccharides, glycans, glycoproteins and so on, are the important targets in current research frontiers such as metabolomics, glycomics and proteomics, boronate affinity materials have gained rapid development and found increasing applications in the last decade. In this review, we critically survey recent advances in boronate affinity materials. We focus on fundamental considerations as well as important progress and new boronate affinity materials reported in the last decade. We particularly discuss on the effects of the structure of boronate ligands and supporting materials on the properties of boronate affinity materials, such as binding pH, affinity, selectivity, binding capacity, tolerance for interference and so on. A variety of promising applications, including affinity separation, proteomics, metabolomics, disease diagnostics and aptamer selection, are introduced with main emphasis on how boronate affinity materials can solve the issues in the applications and what merits boronate affinity materials can provide. [ABSTRACT FROM AUTHOR]

We present a new strategy, called dual-template docking oriented molecular imprinting (DTD-OMI), for facile and highly efficient imprinting within mesoporous materials. As compared with bulk imprinting, which is a widely used strategy, DTD-OMI did not require additional steps, but provided significantly improved imprinting efficiency and binding properties. [ABSTRACT FROM AUTHOR]

Labeling is critical for the detection, quantitation, and structural identification of saccharides. However, conventional liquid-phase labeling suffers from apparent disadvantages, such as time-consuming, the presence of excessive labeling reagent, and high applicable saccharide concentration. A solid-phase approach is presented for highly efficient labeling of saccharides, using boronic acid functionalized mesoporous silica nanoparticles (MSNs) as a selective extraction sorbent and nanoscale reactor. The solid-phase labeling approach exhibited several significant advantages, including: much faster reaction speed (taking only 2 min), high product purity, and much lower applicable saccharide concentration (four orders of magnitude lower than that of liquid-phase labeling). Thus, this labeling approach opens up new avenues to the facile and efficient labeling of saccharides. [ABSTRACT FROM AUTHOR]

Labeling is critical for the detection, quantitation, and structural identification of saccharides. However, conventional liquid-phase labeling suffers from apparent disadvantages, such as time-consuming, the presence of excessive labeling reagent, and high applicable saccharide concentration. A solid-phase approach is presented for highly efficient labeling of saccharides, using boronic acid functionalized mesoporous silica nanoparticles (MSNs) as a selective extraction sorbent and nanoscale reactor. The solid-phase labeling approach exhibited several significant advantages, including: much faster reaction speed (taking only 2 min), high product purity, and much lower applicable saccharide concentration (four orders of magnitude lower than that of liquid-phase labeling). Thus, this labeling approach opens up new avenues to the facile and efficient labeling of saccharides. [ABSTRACT FROM AUTHOR]

Highlights: [•] The fluorescence of native and denatured Lys was quenched by sinomenine at pH 7.4. [•] The effect of metal ions on the binding constant of sinomenine with Lys was studied. [•] The pH 7.4 is the optimal acidity in the binding reaction. [•] Sinomenine was harder to bind to the denatured Lys. [Copyright &y& Elsevier]

Abstract: The binding of baicalein to bovine serum albumin (BSA) in the absence and presence of Cu2+ or Fe3+ in aqueous solution has been studied by fluorescence, synchronous fluorescence, ultraviolet–visible (UV–vis) spectra, circular dichroism (CD) and the three-dimensional (3D) fluorescence at pH 7.40. The decrease of the binding constant in the presence of Cu2+ or Fe3+ may result from the competition of the metal ions and baicalein binding to BSA. The effect of baicalein on the conformation of BSA was analyzed using UV, CD, fluorescence and three-dimensional (3D) fluorescence. These results indicate that the binding of baicalein to BSA causes apparent change in the secondary structure of BSA, but does not affect the polarity around the chromophore molecule. [ABSTRACT FROM AUTHOR]

Abstract: The interaction of rutin to bovine serum albumin (BSA) in aqueous solution was investigated by fluorescence spectra and ultraviolet–visible (UV–vis) spectra at pH 7.40. There are also some metal ions present in blood plasma, thus the research about the effect of metal ions on the interaction of drugs with proteins is crucial. Therefore, we have studied the effect of Cu2+ or Fe3+ on the interaction between rutin and BSA by using spectroscopic technique at pH 7.40, for the first time. The results of fluorescence titration indicated that rutin could quench the intrinsic fluorescence of BSA in a static quenching way. The binding sites number (n), the binding constant (K) and the spatial-distance (r) of rutin with BSA without or with Cu2+ or Fe3+ at 310K were calculated. The result showed that the presence of Cu2+ or Fe3+ increased the binding constant and changed the binding distance between the acceptor and the donor, which possibly results from the formation of metal ions–BSA complex. The effect of rutin on the conformation of BSA was also analyzed using UV under experimental conditions. Furthermore, the fluorescence displacement experiments indicated that rutin is situated within subdomain IIA of BSA. [Copyright &y& Elsevier]