Microchip extraction of catecholamines using a boronic acid functional affinity monolith

Hierarchical Macroporous Agarose Materials with Polyethyleneimine-Assisted Multiple Boronate Affinity Binding Sites for the Separation of Neomycin

Quantification of neomycin residues in food samples demands an efficient purification platform. Herein, hierarchical macroporous agarose monoliths with multiple boronate affinity sites were established for selective separation of neomycin. The silica core was synthesized by "one-step" Stöber procedures followed by modification with amino group and incorporation of polyethyleneimine. A versatile macroporous agarose monolith was prepared by emulsification strategies and functionalized with epoxy groups. After introducing polyethyleneimine-integrated silica nanoparticles onto the agarose monolith, fluorophenylboronic acids were immobilized. The physical and chemical characteristics of the composite monolith were analyzed systematically. After optimization, neomycin showed high binding ability of 23.69 mg/g, and the binding capacity can be manipulated by changing the pH and adding monosaccharides. The composite monolith was subsequently utilized to purify neomycin from the spiked model aquatic products followed by high-performance liquid chromatography analysis, which revealed a remarkable neomycin purification effect, indicating the great potential in the separation of neomycin from complicated aquatic products.

Cryogel Monoliths for Analyte Enrichment by Capture and Release

A platform based on cryogel monoliths in small capillaries, which allows very strong enrichment of an analyte through a capture and release process, is described. For their preparation, a photoreactive copolymer solution containing capture molecules of interest is filled into a capillary, frozen in, and then photochemically transformed into cryogel monoliths through C,H-insertion cross-linking reactions. As a test example, the platform is used for the preconcentration of dopamine from bovine serum albumin and urine samples through capture and release processes. During capture from a large volume and release into a smaller volume, the platform shows recovery rates up to 97% and allows up to a roughly 630-fold enrichment of the concentration of the analyte. The presented platform could be used as a disposable device for the purification and enrichment of a variety of cis-diol-containing samples.

Phenylboronic Acid-polymers for Biomedical Applications

Background:

Phenylboronic acid-polymers (PBA-polymers) have attracted tremendous attention as potential stimuli-responsive materials with applications in drug-delivery depots, scaffolds for tissue engineering, HIV barriers, and biomolecule-detecting/sensing platforms. The unique aspect of PBA-polymers is their interactions with diols, which result in reversible, covalent bond formation. This very nature of reversible bonding between boronic acids and diols has been fundamental to their applications in the biomedical area.

Methods:

We have searched peer-reviewed articles including reviews from Scopus, PubMed, and Google Scholar with a focus on the 1) chemistry of PBA, 2) synthesis of PBA-polymers, and 3) their biomedical applications.

Results:

We have summarized approximately 179 papers in this review. Most of the applications described in this review are focused on the unique ability of PBA molecules to interact with diol molecules and the dynamic nature of the resulting boronate esters. The strong sensitivity of boronate ester groups towards the surrounding pH also makes these molecules stimuli-responsive. In addition, we also discuss how the re-arrangement of the dynamic boronate ester bonds renders PBA-based materials with other unique features such as self-healing and shear thinning.

Conclusion:

The presence of PBA in the polymer chain can render it with diverse functions/ relativities without changing their intrinsic properties. In this review, we discuss the development of PBA polymers with diverse functions and their biomedical applications with a specific focus on the dynamic nature of boronate ester groups.

Multidentate boronate magnetic adsorbent assembled with polyhedral oligomeric silsesquioxanes and intramolecular diboronic acid for improving the binding strength toward glycoproteins

Boronate affinity is an important method for the enrichment and separation of cis-diol containing compounds, but most of the conventional boronate materials suffer from weak binding strength as well as low binding capacity towards glycoproteins due to the use of single boronic acids as ligands. In this work, a novel multidentate boronate magnetic adsorbent was assembled by using amined polyhedral oligomeric silsesquioxane as spacer and a diboronic acid as ligand. The specially designed adsorbent exhibited high adsorption capacity for cis-diols due to the high density of phenylbronic acid moieties. More interestingly, the dissociation constants toward glycoproteins on the material were lowered to be ∼10-6 M, being at least 3 orders lower than the single boronic acid bonded adsorbents. By comparing the binding properties of small molecules containing one and two pairs of cis-diols, the enhanced binding strength of glycoproteins on the multidentate boronate magnetic adsorbent was attributed to the synergistic binding of glycoproteins on the special interface. The new materials successfully captured glycoproteins from 1000-fold diluted egg white, suggesting that the material could be an optional alternative adsorbent for enriching trace glycoproteins from complex bio-samples.

Analysis of Catecholamines and Pterins in Inborn Errors of Monoamine Neurotransmitter Metabolism-From Past to Future

Inborn errors of monoamine neurotransmitter biosynthesis and degradation belong to the rare inborn errors of metabolism. They are caused by monogenic variants in the genes encoding the proteins involved in (1) neurotransmitter biosynthesis (like tyrosine hydroxylase (TH) and aromatic amino acid decarboxylase (AADC)), (2) in tetrahydrobiopterin (BH₄) cofactor biosynthesis (GTP cyclohydrolase 1 (GTPCH), 6-pyruvoyl-tetrahydropterin synthase (PTPS), sepiapterin reductase (SPR)) and recycling (pterin-4a-carbinolamine dehydratase (PCD), dihydropteridine reductase (DHPR)), or (3) in co-chaperones (DNAJC12). Clinically, they present early during childhood with a lack of monoamine neurotransmitters, especially dopamine and its products norepinephrine and epinephrine. Classical symptoms include autonomous dysregulations, hypotonia, movement disorders, and developmental delay. Therapy is predominantly based on supplementation of missing cofactors or neurotransmitter precursors. However, diagnosis is difficult and is predominantly based on quantitative detection of neurotransmitters, cofactors, and precursors in cerebrospinal fluid (CSF), urine, and blood. This review aims at summarizing the diverse analytical tools routinely used for diagnosis to determine quantitatively the amounts of neurotransmitters and cofactors in the different types of samples used to identify patients suffering from these rare diseases.

Visible Light Detection of Dopamine Enhanced by Cloud Point Extraction

Background:

Monitoring of DA, in the presence of other chemical analogues such as epinephrine, norepinephrine, serotonin, ascorbic acid, uric acid, catechol, phenethylamine, tyramine, and tyrosine, is crucial in the diagnosis and mechanistic understanding of human neuropathology. Therefore, the determination of DA at trace levels has become a very important analytical task, as part of health safety and forensic analysis.

Introduction:

A cloud point extraction (CPE) process was developed for the isolation and detection of dopamine in food, urine, and pharmaceutical samples.

Methods:

In this procedure, dopamine was derivatized with o-phthalaldehyde (OPA) and sodium sulphite in aqueous solution. The isoindole derivative was synthesized by the reaction of OPA and sodium sulphite with the amino group of dopamine and the resulted isoindole derivatives were extracted by cloud point extraction. After extraction process, the concentration of enriched analyte was measured by UV-VIS spectrophotometry. The parameters affecting the CPE such as concentration of surfactant and electrolyte, equilibration temperature and time and pH of sample solution were investigated.

Results:

After optimization of the CPE conditions, the linear range of 8-80 µM (without extraction 100- 1000 µM) was established for dopamine with detection limit at 2.6 µM.

Conclusion:

The developed extraction procedure was applied to the quantification of dopamine in chocolate, urine, and pharmaceutical samples. The study ensures a promising strategy for the detection of dopamine in the presence of biological constituents, e.g. ascorbic acid, uric acid, and serotonin.

Accelerated hydrolysis of boronic acid in a modified poly(amidoamine) dendrimer: identification of a factor leading to the production of an impurity in boronic acid containing poly(amidoamine) dendrimers

The preparation of boronic acid containing dendrimers is still a difficult task in dendrimer chemistry. In this investigation, an unanticipated hydrolysis product (4) was identified during the preparation of (G:2)-PAMAM-dendri-(4-phenyl boronic acid)14 (3) by acquiring its 1H NMR, 13C NMR, and UV–vis absorption spectra and IR spectra and comparing them with those of 4-hydroxylbenzoic acid (5). Furthermore, an Alizarin Red S staining analysis, ICP-MS, and 11B NMR spectrum indicated the lack of boronic acid in 4. Finally, treatment of 3 with hydrogen peroxide gave a product that was determined to be identical to dendrimer 4. By analyzing the formation of 4 under various conditions, the presence of numerous primary amines in a PAMAM dendrimer did accelerate the hydrolysis of peripheral boronic acid. This investigation revealed an apparent intrinsic problem that needs to be overcome during the preparation of boronic acid containing dendrimers and related boronic acid containing macromolecules.

Phenylboronic acid-functionalized core–shell magnetic composite nanoparticles as a novel protocol for selective enrichment of fructose from a fructose–glucose aqueous solution

We developed an efficient and mild method for the preparation of boronic acid-functionalized magnetic nanoparticles (MNPs), and the selective separation of fructose from a sample solution was demonstrated for the first time.

Advances in monoliths and related porous materials for microfluidics

In recent years, the use of monolithic porous polymers has seen significant growth. These materials present a highly useful support for various analytical and biochemical applications. Since their introduction, various approaches have been introduced to produce monoliths in a broad range of materials. Simple preparation has enabled their easy implementation in microchannels, extending the range of applications where microfluidics can be successfully utilized. This review summarizes progress regarding monoliths and related porous materials in the field of microfluidics between 2010 and 2015. Recent developments in monolith preparation, solid-phase extraction, separations, and catalysis are critically discussed. Finally, a brief overview of the use of these porous materials for analysis of subcellular and larger structures is given.

Polyethyleneimine-facilitated high-capacity boronate affinity membrane and its application for the adsorption and enrichment of cis-diol-containing molecules

High capacity boronate affinity membranes were prepared for the first time, the membranes possess good selectivity, faster adsorption and desorption speed towards cis-diol-containing molecules.

Synthesis and application of boronic acid-functionalized magnetic adsorbent for sensitive analysis of salbutamol residues in pig tissues

Salbutamol (SAL) is the most widely used β2 -agonist drug for asthma and chronic obstructive pulmonary patients, but it is also often abused as feed additive. In recent years, the abuse of SAL has led to a large number of food safety incidents. Therefore, the monitoring of SAL residues in animal products is very important. A highly selective boronate affinity magnetic adsorbent was synthesized and developed for detection of trace levels of SAL residues in pig tissue samples. The obtained Fe3O4@SiO2@FPBA(4-formylphenylboronic acid) magnetic adsorbent showed good adsorption ability to catechol and SAL, and then it was successfully applied as special magnetic solid-phase phase extraction adsorbent coupled with high-performance liquid chromatography (HPLC) for simultaneous isolation and determination of cis-diol compounds. The binding capacity of catechol and SAL reached 96 and 50 µmol/g, respectively. The method was successfully established for the detection of trace levels of SAL in pig tissue samples. The linear range extended from 0.32 to 800 µg/kg (R(2) = 0.9994). The limit of detection of SAL was 0.19 µg/kg. The recoveries were satisfactory (89.5-108.0%) at three spiked levels with RSD between 2.1 and 11.3%. These results indicated that the method has potential for enrichment and detection of trace levels of SAL residual in animal food products.

One-pot preparation of boronic acid and PEG bi-functionalized silica particles for separation and purification of catecholamine from rat serum

A novel boronate absorbent with the ability to resist protein adsorption was synthesized by a one step method.

Synthesis and characterization of 4-(2-aminoethyl)aniline imprinted polymer as a highly effective sorbent of dopamine

The aim of the study was to develop an efficient sorbent for the separation of dopamine. 4-(2-Aminoethyl)aniline was chosen as a pseudo-template to produce the imprinted polymers from seven different functional monomers in the presence of ethylene glycol dimethacrylate as a cross-linker. The binding capacity showed that the highest binding specificity towards dopamine was achieved when methacrylic acid was used as the monomer in methanol solution to form a polymer matrix. The imprinting factor value was equal to 22.96. Other biogenic amines were bound much more weakly. A simple theoretical model was used to give an insight into the imprinting process and the selectivity of polymer matrix. Two artificial urine samples were used as the complex matrices to show the usefulness of the new sorbent for bioanalysis.

Recent advances in enhancing the sensitivity of electrophoresis and electrochromatography in capillaries and microchips (2010-2012)

CE has been alive for over two decades now, yet its sensitivity is still regarded as being inferior to that of more traditional methods of separation such as HPLC. As such, it is unsurprising that overcoming this issue still generates much scientific interest. This review continues to update this series of reviews, first published in Electrophoresis in 2007, with updates published in 2009 and 2011 and covers material published through to June 2012. It includes developments in the field of stacking, covering all methods from field amplified sample stacking and large volume sample stacking, through to isotachophoresis, dynamic pH junction and sweeping. Attention is also given to online or inline extraction methods that have been used for electrophoresis.

Integrated affinity and electrophoresis systems for multiplexed biomarker analysis

The integration of affinity columns in microfluidic devices generates a micro-total analysis system which has high value in applications such as analyte extraction and preconcentration. In this chapter we describe the preparation of affinity columns in situ by photopolymerization of acrylate monomers. The epoxy groups on the columns are further functionalized with antibodies to form affinity columns. We describe in detail the use of our affinity columns in extracting cancer biomarkers from model mixtures and blood serum. The purified biomarkers are then eluted from the column, separated by microchip capillary electrophoresis, and detected by laser-induced fluorescence. Our procedures allow efficient sample pretreatment and preconcentration, as well as simultaneous and rapid quantification of multiple biomarkers.

Applications of reversible covalent chemistry in analytical sample preparation

Reversible covalent chemistry (RCC) adds another dimension to commonly used sample preparation techniques like solid-phase extraction (SPE), solid-phase microextraction (SPME), molecular imprinted polymers (MIPs) or immuno-affinity cleanup (IAC): chemical selectivity. By selecting analytes according to their covalent reactivity, sample complexity can be reduced significantly, resulting in enhanced analytical performance for low-abundance target analytes. This review gives a comprehensive overview of the applications of RCC in analytical sample preparation. The major reactions covered include reversible boronic ester formation, thiol-disulfide exchange and reversible hydrazone formation, targeting analyte groups like diols (sugars, glycoproteins and glycopeptides, catechols), thiols (cysteinyl-proteins and cysteinyl-peptides) and carbonyls (carbonylated proteins, mycotoxins). Their applications range from low abundance proteomics to reversible protein/peptide labelling to antibody chromatography to quantitative and qualitative food analysis. In discussing the potential of RCC, a special focus is on the conditions and restrictions of the utilized reaction chemistry.