Boronate affinity monolith via two-step atom transfer radical polymerization for specific capture of cis -diol-containing compounds

Preparation of branched polyethyleneimine-assisted boronic acid-functionalized magnetic MXene for the enrichment of catecholamines in urine samples

Herein, a magnetic borate-functionalized MXene composite with multiple boronic affinity sites was fabricated by embedding Fe3 O4 nanoparticles with 4-formylphenylboronic acid functionalized Ti3 C2 Tx nanosheets and served as sorbent for the simultaneous extraction of catecholamines (CAs) in urine samples. The morphology and structure of the magnetic materials were investigated using scanning microscopy, vibrating sample magnetometer, X-ray photoelectron spectrometer, and X-ray diffraction. The introduction of polyethyleneimine can amplify the bonded boronic acid groups, thereby effectively improving the adsorption capacities for CAs based on the multiple interactions of boronic affinity, hydrogen bonding, and metal coordination. The adsorption performance was investigated using the kinetics and isotherms models, and the main parameters that influence the extraction efficiency were optimized. Under the most favorable magnetic solid-phase extraction condition, a sensitive method for the analysis of CAs in urine samples was developed by combining magnetic solid-phase extraction conditions with high-performance liquid chromatography detection. The findings illustrated that the proposed approach possessed a wide linearity range of 0.05-250 ng/mL with an acceptable correlation coefficient (R2  ≥ 0.9984) and detection limits of 0.010-0.015 ng/mL for the target CAs. The research not only provides a notable composite with multiple boronic affinity sites but also offers an effective and feasible measure for the detection of CAs in biological samples.

Simultaneous extraction of hydroxylated polycyclic aromatic hydrocarbons and catecholamines with magnetic boronic acid hypercrosslinked polymers

Urinary hydroxylated polycyclic aromatic hydrocarbons (OH-PAHs) and catecholamines (CAs) are important biomarkers of PAHs exposure. In this study, a novel magnetic boronic acid hypercrosslinked composite (Fe3O4@HCP-BA) is synthesized using a facile one-pot strategy and applied as a sorbent for the simultaneous extraction of OH-PAHs and CAs in urine samples. The synthesized Fe3O4@HCP-BA composites are characterized by rich pore structure, highly specific surface area, good magnetic response, and excellent selectivity and adsorption efficiency (range: 65.26-496.71 and 1227.3-1581.8 µmol g-1 for CAs and OH-PAHs, respectively). The mechanisms governing the adsorption of the OH-PAHs and CAs to the Fe3O4@HCP-BA composites were systematically studied via adsorption kinetics, isotherm models, XPS characterization, and molecular simulation. The resultant Fe3O4@HCP-BA composite-based MSPE/HPLC-FLD method exhibited good linearity (R2 > 0.9916), low limits of detection (0.2-0.3 pg mL-1 and 0.2-0.3 ng mL-1 for OH-PAHs and CAs, respectively), and good precision (intra-day and inter-day RSDs < 11.1%). The analysis of CAs and OH-PAHs in the urine samples from 14 smokers and 14 non-smokers revealed a positive correlation between the concentrations of CAs and OH-PAHs. Our findings not only establish the proposed method as a green, environmentally friendly, and simple strategy for preparing magnetic adsorbents, but also confirm it as a promising alternative method for accurate determination of OH-PAHs and CAs in biological samples.

Two-dimensional boron nanosheets for selective enrichment and detection of cis-diol compounds by surface-assisted laser desorption/ionization time-of-flight mass spectrometry

Surface-assisted laser desorption/ionization time-of-flight mass spectrometry (SALDI-TOF MS) is an effective method for detecting of low-mass molecules. In this study, two-dimensional boron nanosheets (2DBs) were fabricated through thermal oxidation etching and coupling liquid exfoliation technologies, and applied as a matrix and selective sorbent for detecting cis-diol compounds by SALDI-TOF MS. The outstanding nanostructure and boric acid active sites of 2DBs endow them with sensitivity for cis-diol compound detection, excellent selectivity, and low background interference for complex samples. The specific in-situ enrichment faculty of the 2DBs as a matrix was investigated by SALDI-TOF MS using glucose, arabinose, and lactose as model analytes. In the presence of 100 -fold more interfering substances, the 2DBs showed high selectivity against cis-diol compounds, and exhibited a better sensitivity and a reduced limit of detection through enrichment treatment than graphene oxide matrices. The linearity, limit of detection (LOD), reproducibility, and accuracy of the method were evaluated under optimized conditions. The results showed that the linear relationships of six saccharides remained in the range of 0.05-0.6 mM with a correlation coefficient r ≥0.98. The LODs of six saccharides were 1 nM (glucose, lactose, mannose, fructose) and 10 nM (galactose, arabinose). Sample-to-sample (n = 6) with relative standard deviations (RSDs) of 3.2% to 8.1% were observed. Recoveries (n = 5) of 87.9-104.6% were obtained at three spiked levels in the milk samples. The proposed strategy promoted the development of a matrix for use with SALDI-TOF MS detection, in which the UV absorption properties and enrichment capabilities of 2DBs were combined.

Improving performance of cell imprinted PDMS by integrating boronate affinity and local post-imprinting modification for selective capture of circulating tumor cells from cancer patients

Efficient capture of circulating tumor cells (CTCs) from cancer patients is an important technique that may promote early diagnosis and prognosis monitoring of cancer. However, the existing systems have certain disadvantages, such as poor selectivity, low capture efficiency, consumption of antibodies, and difficulty in release of CTCs for downstream analysis. Herein, we fabricated an innovative PEGylated boronate affinity cell imprinted polydimethylsiloxane (PBACIP) for highly efficient capture of CTCs from cancer patients. The antibody-free PBACIP possessed hierarchical structure of imprinted cavities, which were inlaid with boronic acid modified SiO₂ nanoparticles (SiO₂@BA), so it could specifically capture target CTCs from biological samples due to the synergistic effect of boronate affinity and cell imprinting. Furthermore, PEGylation was accurately completed in the non-imprinted region by the template cells occupying the imprinted cavity, which not only retained the microstructure of original imprinted cavities, but also endowed PBACIP with hydrophilicity. The artificial PBACIP could efficiently capture human breast-cancer cells from biological sample. When 5 to 500 SKBR3 cells were spiked in 1 mL mice lysed blood, the capture efficiency reached 86.7 ± 11.5% to 96.2 ± 2.3%. Most importantly, the PBACIP was successfully used to capture CTCs from blood of breast cancer patients, and the captured CTCs were released for subsequent gene mutation analysis. The PBACIP can efficiently capture and release CTCs for downstream analysis, which provides a universal strategy toward individualized anti-tumor comprehensive treatments and has great potential in the future cell-based clinical applications.

A review on recent advances in the enrichment of glycopeptides and glycoproteins by liquid chromatographic methods: 2016-Present

Among various protein post-translational modifications (PTMs), glycosylation has received special attention due to its immense role in molecular interactions, cellular signal transduction, immune response, etc. Aberration in glycan moieties of a glycoprotein is associated with cancer, diabetes, and bacterial and viral infections. In biofluids (plasma, saliva, urine, milk, etc.), glycoproteins are low in abundance and are masked by the presence of high abundant proteins. Hence, prior to their identification using mass spectrometry methods, liquid chromatography (LC)-based approaches were widely used. A general enrichment strategy involves a protein digestion step, followed by LC-based enrichment and desorption of glycopeptides, and enzymatic excision of the glycans. The focus of this review article is to highlight the articles published since 2016 that dealt with different LC-based approaches for glycopeptide and glycoprotein enrichment. The preparation of stationary phases, their surface activation, and ligand immobilization strategies have been discussed in detail. Finally, the major developments and future trends in the field have been summarized.

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.

Magnetic borate-modified Mxene: A highly affinity material for the extraction of catecholamines

A novel magnetic borate-modified MXene composite was prepared by in situ growth of Fe₃O₄ particles onto the surface of phenylboronic acid modified Ti₃C₂T_x nanosheets. The magnetic composite possesses highly selective recognition properties to catecholamines, and high adsorption capacity (up to 319.6 μmol g^-1) for dopamine. Besides, the adsorption of urinary catecholamines can be accomplished within 2.0 min. The excellent adsorption performance can be assigned to its unique 2D layered structures, which helps to shorten the diffusion path and facilitate molecular transport. In addition, the multilayer adsorption and the synergetic interactions of borate affinity, van der Waals forces, hydrogen bonding and π-π stacking also contribute to the adsorption. By coupling the magnetic boronate affinity composites with high-performance liquid chromatography-fluorescence detection, a sensitive method for the determination of catecholamines in urine samples was proposed. The validation results revealed it can offer good linearities (correlation coefficients higher than 99%). The method detection limits were 0.06, 0.16, 0.03 and 0.14 ng mL^-1 for norepinephrine, epinephrine, dopamine and isoprenaline, respectively, and relative recoveries for these catecholamines were in the range of 98.56-108.1%, 92.56-110.0%, 98.79-112.3% and 88.14-97.81%, respectively. The proposed method was successfully applied to analyze the catecholamines in the urine samples from 15 healthy volunteers and 16 patients with Alzheimer's disease. The results indicated that the magnetic borate-modified Mxene composite possesses superior extraction performance, and can be used as an outstanding candidate for the extraction of catecholamines in pre-clinical or clinical studies.

Preparation of Boronic Acid-Functionalized Cryogels Using Modular and Clickable Building Blocks for Bacterial Separation

Composite cryogels containing boronic acid ligands are synthesized for effective separation and isolation of bacteria. The large and interconnected pores in cryogels enable fast binding and release of microbial cells. To control bacterial binding, an alkyne-tagged boronic acid ligand is conjugated to azide-functionalized cryogel via the Cu(I)-catalyzed azide-alkyne cycloaddition reaction. The boronic acid-functionalized cryogel binds Gram-positive and Gram-negative bacteria through reversible boronate ester bonds, which can be controlled by pH and simple monosaccharides. To increase the capacity of affinity separation, a new approach is used to couple the alkyne-tagged phenylboronic acid to cryogel via an intermediate polymer layer that provides multiple immobilization sites. The morphology and chemical composition of the composite cryogel are characterized systematically. The capability of the composite cryogel for the separation of Gram-positive and Gram-negative bacteria is investigated. The binding capacities of the composite cryogel for Escherichia coli and Staphylococcus epidermidis are 2.15 × 10⁹ and 3.36 × 10⁹ cfu/g, respectively. The bacterial binding of the composite cryogel can be controlled by adjusting pH. The results suggest that the composite cryogel may be used as affinity medium for rapid separation and isolation of bacteria from complex samples.