A novel fluorescent sensor for selective rifampicin detection based on the bio-inspired molecularly imprinted polymer-AgInS2/ZnS quantum dots

A fluorescent sensing material based on the ternary core-shell quantum dots with outstanding optical properties and a bio-inspired molecularly imprinted polymer (MIP) as a recognition element has been prepared for selective detection of rifampicin (RFP). Firstly, AgInS2/ZnS core/shell quantum dots (ZAIS QDs) were prepared by a hydrothermal process. Then, the fluorescent sensor was prepared by coating these QDs by a dopamine-based MIP layer. The fluorescence of MIP@ZAIS QDs was quenched by RFP probably due to the photoinduced electron transfer process. The quenching constant was much higher for MIP@ZAIS QDs than the non-imprinted polymer@QDs, indicating that MIP@ZAIS QDs could selectively recognize RFP. Under the optimized conditions, the sensor had a good linear relationship at the RFP concentration range of 5.0 to 300 nM and the limit of detection was 1.25 nM. The respond time of the MIP@ZAIS QDs was 5 min, and the imprinting factor was 6.3. It also showed good recoveries ranging from 98 to 101%, for analysis of human plasma samples. The method is simple and effective for the detection of RFP and offers a practical application for the rapid analysis of human plasma samples.

Nanopore Discrimination of Nucleotide Sugars

Nucleotide sugars, the glycosyl donors in the biosynthesis of carbohydrates, are critical ingredients in the growth and development of all living organisms. A variety of nucleotide sugars simultaneously exist in biological samples. They, however, have only minor structural differences, which make them extremely difficult to discriminate. In this work, a phenylboronic acid (PBA)-modified Mycobacterium smegmatis porin A (MspA) hetero-octamer was applied to sense nucleotide sugars. Five representative nucleotide sugars, including guanosine diphosphate mannose (GDP-Man), adenosine diphosphate glucose (ADP-Glc), uridine diphosphate N-acetylglucosamine (UDP-GlcNAc), uridine diphosphate glucose (UDP-Glc), and uridine diphosphate glucoronic acid (UDP-GlcA), were successfully distinguished. A custom machine learning algorithm was also employed to automatically identify events, reporting a general accuracy of 99.4%. This sensing strategy provides a rapid, direct, and accurate method for identifying different nucleotide sugars. However, single-molecule identification of nucleotide sugars has never been previously reported, to the best of our knowledge.

Boronate-modified polyethyleneimine dendrimer as a solid-phase extraction adsorbent for the analysis of luteolin via HPLC

Luteolin (LTL) is a flavonoid containing a cis-diol, which has significant anti-inflammatory, anti-allergic, anti-diabetic, anti-cancer and neuroprotective activities. In this work, a silver modified boric acid affinity polyvinyl imine (PEI) dendritic adsorbent (PPEI-Ag@CPBA) was prepared on polystyrene (PS) for the rapid recognition and selective separation of LTL. A thin layer of polydopamine (PDA) was formed on the surface of the substrate by self-polymerization, and a PDA-coated PS material (PS@PDA) was obtained. PEI with sufficient active amino groups was grafted onto PS@PDA to obtain a PEI-modified material (PS@PDA@PEI), then AgNO3 was reduced with NaBH4, and PS@PDA@PEI was embedded on Ag. Finally, PPEI-Ag@CPBA was obtained through the condensation reaction of PEI with 4-carboxyphenyl boric acid (CPBA). The adsorption conditions were optimized, the optimal pH and the optimum amount of adsorbent were determined, and the maximum adsorption capacity was found to be 2.49 mg g-1. This method has been successfully applied to the selective identification of LTL in peanut shell samples, and provides a practical platform for the detection of LTL in complex substrates.

Boronate affinity material-based sensors for recognition and detection of glycoproteins

This review comprehensively presents the current overview and development potential of BAMs-based sensors for glycoprotein recognition and detection.

Preparation of salbutamol imprinted magnetic nanoparticles via boronate affinity oriented surface imprinting for the selective analysis of trace salbutamol residues

Salbutamol (SAL) is one of the most widely abused feed additives in animal husbandry.

Boronic acid functionalized g-C3N4 nanosheets for ultrasensitive and selective sensing of glycoprotein in the physiological environment

As important biomarkers, glycoprotein sensing is frequently facilitated by boronic acid binding with its cis-diols. However, boronic acid based sensors suffer from drawbacks of alkali restriction and/or sensitivity limitation. Herein, we report boronic acid decorated g-C₃N₄ nanosheets (B-g-CN) with a Wulff-type boronic acid feature, which selectively bind glycoprotein under physiological conditions. Meanwhile, the binding causes significant enhancement of the B-g-CN nanosheet fluorescence, providing the basis for glycoprotein sensing. With IgG as a model, a detection limit (LOD) of 2.2 nM (3σ/s, n = 11) was obtained within a linear range of 6.7-67 nM. The LOD was further improved to 52 pM subject to enrichment of the nanosheets, which well enables IgG assay in human urine samples. Moreover, it was successful in imaging endogenous and exogenous glycoproteins in living cells.

Facile synthesis of carboxymethyl-β-cyclodextrin conjugated magnetic nanoparticles for selective enrichment of glycopeptides

RATIONALE

Selective enrichment of glycopeptides prior to mass spectrometry (MS) analysis is essential due to the low abundance of the modified glycopeptides in complex samples, ion suppression effects during MS ionization and detection caused by the co-presence of non-glycosylated peptides, etc. Among different enrichment approaches, hydrophilic interaction liquid chromatography (HILIC)-based magnetic separation has become one of the most popular methods in recent years, due to its high efficiency and selectivity for glycopeptide enrichment.

METHODS

Herein, novel carboxymethyl-β-cyclodextrin (CMCD)-modified magnetic nanoparticles (MNPs) were synthesized via a carbodiimide activation method. CMCD was covalently bonded with the -OH group on the surface of MNPs through carbodiimide, and the proposed procedure provides a rapid and efficient alternative for glycopeptide enrichment due to its stable interaction, time-saving, and easy operation.

RESULTS

The prepared absorbents with a mean diameter of 15 nm demonstrated a strong magnetic response to an externally applied magnetic field. The results of thermogravimetric analysis showed the content of bound CMCD was 3 wt%. The outer CMCD layer conjugated on the Fe3 O4 core showed high hydrophilic surface property. In the analysis of a complex mouse liver sample, a total of 666 unique N-glycosylation sites corresponding to 494 glycosylated proteins were identified successfully.

CONCLUSIONS

The study demonstrated an easy-to-use CMCD-modified MNPs-based approach with high selectivity and high capacity in the enrichment of low-abundance glycopeptides from complex biological samples. Copyright © 2016 John Wiley & Sons, Ltd.

Molecularly imprinted polymers as recognition materials for electronic tongues

For over three decades now, molecularly imprinted polymers (MIPs) have successfully been used for selective chemical sensing because the shape and size of their imprinted molecular cavities perfectly matched those of the target analyte molecules. Moreover, orientation of recognizing sites of these cavities corresponded to those of the binding sites of the template molecules. In contrast, electronic tongue (e-tongue) is usually an array of low-affinity recognition units. Its selectivity is based on recognition pattern or multivariate analysis. Merging these two sensing devices led to a synergetic hybrid sensor, an MIP based e-tongue. Fabrication of these e-tongues permitted simultaneous sensing and discriminating several analytes in complex solutions of many components so that these arrays compensated for limitation in cross-reactivity of MIPs. Apparently, analytical signals generated by MIP-based e-tongues, compared to those of ordinary sensor arrays, were more reliable where a unique pattern or 'fingerprint' for each analyte was generated. Additionally, several transduction platforms (from spectroscopic to electrochemical) engaged in constructing MIP-based e-tongues, found their broad and flexible applications. The present review critically evaluates achievements in recent developments of the MIP based e-tongues for chemosensing.

Boronate-Affinity Glycan-Oriented Surface Imprinting: A New Strategy to Mimic Lectins for the Recognition of an Intact Glycoprotein and Its Characteristic Fragments

Lectins possess unique binding properties and are of particular value in molecular recognition. However, lectins suffer from several disadvantages, such as being hard to prepare and showing poor storage stability. Boronate-affinity glycan-oriented surface imprinting was developed as a new strategy for the preparation of lectin-like molecularly imprinted polymers (MIPs). The prepared MIPs could specifically recognize an intact glycoprotein and its characteristic fragments, even within a complex sample matrix. Glycan-imprinted MIPs could thus prove to be powerful tools for important applications such as proteomics, glycomics, and diagnostics.

Simple and effective label-free capillary electrophoretic analysis of sugars by complexation using quinoline boronic acids

An effective separation and detection procedure for sugars by capillary electrophoresis (CE) using a complexation between quinolineboronic acid (QBA) and multiple hydroxyl structure of sugar alcohol is reported. We investigated the variation of fluorescence spectra of a variety of QBAs with sorbitol at a wide range of pH conditions and then found that 5-isoQBA strongly enhanced the fluorescence intensity by the complexation at basic pH conditions. The other sugar alcohols having multiple hydroxyls also revealed the enhancement of the fluorescence intensity with 5-isoQBA, whereas the alternation of the intensity was not found in the sugars such as glucose. After optimization of the 5-isoQBA concentration and pH of the buffered solution in CE analysis, 6 sugar alcohols were successfully separated in the order based on the formation constants with 5-isoQBA, which were calculated from the variation of the fluorescence intensity with each sugar alcohol and 5-isoQBA. Furthermore, the limits of detection for sorbitol and xylitol by the CE method were estimated at 15 and 27 μM, respectively.

Highly stable and reusable imprinted artificial antibody used for in situ detection and disinfection of pathogens

Sandwich ELISA methods have been widely used for biomarker and pathogen detection because of their high specificity and sensitivity. However, the main drawbacks of this assay are the cost, the time-consuming procedure for the isolation of antibodies and their poor stability. To overcome these restrictions, we herein fabricated artificial antibodies based on imprinting technology and developed a sandwich ELISA for pathogen detection. Both the capture and detection antibodies were obtained via an in situ method, with simplicity, rapidity and low cost. The peroxidase mimics, the CeO2 nanoparticles, as signal generators were integrated with the detection antibody. The fabricated artificial antibodies exhibited not only natural antibody-like binding affinities and selectivities, but also superior stability and reusability. The detection limit was about 500 CFU mL-1, which is much lower than that of traditional ELISA methods (104 to 105 CFU mL-1). Furthermore, the capture antibody can disinfect pathogens in situ.