Nonenzymatic dual glucose sensing on boronic acid modified zeolitic imidazolate framework-67 nanoparticles for diabetes management.

For early diabetes identification and management, the progression of an uncomplicated and exceedingly responsive glucose testing technology is crucial. In this study, we present a new sensor incorporating a composite of metal organic framework (MOF) based on cobalt, coated with boronic acid to facilitate selective glucose binding. Additionally, we successfully employed a highly sensitive electro-optical immunosensor for the detection of subtle changes in concentration of the diabetes biomarker glycated haemoglobin (HbA1c), using zeolitic imidazolate framework-67 (ZIF-67) coated with polydopamine which further modified with boronic acid. Utilizing the polymerization characteristics of dopamine and the NH2 groups, a bonding structure is formed between ZIF-67 and 4-carboxyphenylboronic acid. ZIF-67 composite served as an effective substrate for immobilising 4-carboxyphenylboronic acid binding agent, ensuring precise and highly selective glucose identification. The sensing response was evaluated through both electrochemical and optical methods, confirming its efficacy. Under optimized experimental condition, the ZIF-67 based sensor demonstrated a broad detection range of 50-500 mg dL-1, a low limit of detection (LOD) of 9.87 mg dL-1 and a high correlation coefficient of 0.98. Furthermore, the 4-carboxyphenylboronic acid-conjugated ZIF-67-based sensor platform exhibited remarkable sensitivity and selectivity in optical-based detection for glycated haemoglobin within the clinical range of 4.7-11.3%, achieving a LOD of 3.7%. These findings highlight the potential of the 4-carboxyphenylboronic acid-conjugated ZIF-67-based electro-optical sensor as a highly sensitive platform for diabetes detection.

Glucose-Responsive Self-Healing Bilayer Drug Microneedles Promote Diabetic Wound Healing Via a Trojan-Horse Strategy.

Chronic nonhealing wounds are serious complications of diabetes with a high morbidity, and they can lead to disability or death. Conventional drug therapy is ineffective for diabetic wound healing because of the complex environment of diabetic wounds and the depth of drug penetration. Here, we developed a self-healing, dual-layer, drug-carrying microneedle (SDDMN) for diabetic wound healing. This SDDMN can realize transdermal drug delivery and broad-spectrum sterilization without drug resistance and meets the multiple needs of the diabetic wound healing process. Quaternary ammonium chitosan cografted with dihydrocaffeic acid (Da) and l-arginine and oxidized hyaluronic acid-dopamine are the main parts of the self-healing hydrogel patch. Methacrylated poly(vinyl alcohol) (methacrylated PVA) and phenylboronic acid (PBA) were used as the main part of the MN, and gallium porphyrin modified with 3-amino-1,2 propanediol (POGa) and insulin were encapsulated at its tip. Under hyperglycaemic conditions, the PBA moiety in the MN reversibly formed a glucose-boronic acid complex that promoted the rapid release of POGa and insulin. POGa is disguised as hemoglobin through a Trojan-horse strategy, which is then taken up by bacteria, allowing it to target bacteria and infected lesions. Based on the synergistic properties of these components, SDDMN-POGa patches exhibited an excellent biocompatibility, slow drug release, and antimicrobial properties. Thus, these patches provide a potential therapeutic approach for the treatment of diabetic wounds.

Molecular two-point recognition of fructosyl valine and fructosyl glycyl histidine in water by fluorescent Zn(II)-terpyridine complexes bearing boronic acids.

Selective recognition of fructosyl amino acids in water by arylboronic acid-based receptors is a central field of modern supramolecular chemistry that impacts biological and medicinal chemistry. Fructosyl valine (FV) and fructosyl glycyl histidine (FGH) occur as N-terminal moieties of human glycated hemoglobin; therefore, the molecular design of biomimetic receptors is an attractive, but very challenging goal. Herein, we report three novel cationic Zn-terpyridine complexes bearing a fluorescent N-quinolinium nucleus covalently linked to three different isomers of strongly acidified phenylboronic acids (ortho-, 2Zn; meta-, 3Zn and para-, 4Zn) for the optical recognition of FV, FGH and comparative analytes (D-fructose, Gly, Val and His) in pure water at physiological pH. The complexes were designed to act as fluorescent receptors using a cooperative action of boric acid and a metal chelate. Complex 3Zn was found to display the most acidic -B(OH)2 group (pKa = 6.98) and exceptionally tight affinity for FV (K = 1.43 × 105 M-1) with a strong quenching analytical response in the micromolar concentration range. The addition of fructose and the other amino acids only induced moderate optical changes. On the basis of several spectroscopic tools (1H, 11B NMR, UV-Vis, and fluorescence titrations), ESI mass spectrometry, X-ray crystal structure, and DFT calculations, the interaction mode between 3Zn and FV is proposed in a 1 : 1 model through a cooperative two-point recognition involving a sp3 boronate-diol esterification with simultaneous coordination bonding of the carboxylate group of Val to the Zn atom. Fluorescence quenching is attributed to a static complexation photoinduced electron transfer mechanism as evidenced by lifetime experiments. The addition of FGH to 3Zn notably enhanced its emission intensity with micromolar affinity, but with a lower apparent binding constant than that observed for FV. FGH interacts with 3Zn through boronate-diol complexation and coordination of the imidazole ring of His. DFT-optimized structures of complexes 3Zn-FV and 3Zn-FGH show a picture of binding which shows that the Zn-complex has a suitable (B⋯Zn) distance to the two-point recognition with these analytes. Molecular recognition of fructosyl amino acids by transition-metal-based receptors has not been explored until now.

Inhibition of insulin fibrillation by carboxyphenylboronic acid-modified chitosan oligosaccharide based on electrostatic interactions and hydrophobic interactions.

A novel inhibitor, carboxyphenylboronic acid-modified chitosan oligosaccharide (COS-CPBA), was developed by coupling carboxyphenylboronic acid (CPBA) with chitosan oligosaccharide (COS) to inhibit insulin fibrillation. Extensive biophysical assays indicated that COS-CPBA could decelerate insulin aggregation, hinder the conformational transition from α-helix to ß-sheet structure, change the morphology of insulin aggregates and alter fibrillation pathway. A mechanism for the inhibition of insulin fibrillation by COS-CPBA was proposed. It considers that insulin molecules bind to COS-CPBA via hydrophobic interactions, while the positively charged groups in COS-CPBA exert electrostatic repulsion on the bound insulin molecules. These two opposite forces cause the insulin molecules to display extended conformations and hinder the conformational transition of insulin from α-helix to ß-sheet structure necessary for fibrillation, thus decelerating aggregation and altering the fibrillation pathway of insulin. The studies provide novel ideas for the development of more effective inhibitors of amyloid fibrillation.

Gelatin nanocarriers assembled by a self-immolative cross-linker for targeted cancer therapy.

With a number of outstanding properties, gelatin is an ideal candidate for assembling nanoplatforms in biomedical applications. Generally, gelatin nanocarriers are cross-linked by aldehydes to improve their stability in water solution. However, aldehydes could cause multiple toxicities and their cross-linking products are uncontrollable. Here, we first used a self-immolative cross-linker to assemble gelatin nanocarriers for the controlled release of drugs and targeted cancer therapy. The cross-linker contains a disulphide bridge and two symmetrical succinimidyl-esters, endowing it with multiple functions: 1) to cross-link the gelatin nanocarriers and thus improve their stability in water; 2) to conjugate the drug and tumor-targeting ligands with nanocarriers through covalent linkage; 3) to redox-responsively degrade the nanocarriers through hydrolysis of disulphide bridge; and 4) to produce traceless drug molecules through self-immolative reaction. Good biocompatibility and controllable drug release were demonstrated by in vitro experiments. Both qualitative and quantitative analyses confirmed the intracellular uptake of the nanocarriers by using doxorubicin (DOX) as a drug model and phenylboronic acid (PBA) as the targeting ligand. In vivo results demonstrated high therapeutic efficiency and low toxic side effects of the DOX loaded nanocarriers against artificial liver tumors.

Quantification of Glycated Hemoglobin in Total Hemoglobin by a Simultaneous Dual-Signal Acquisition Approach.

The glycated hemoglobin (HbA1c) level, which is defined as the ratio of HbA1c to total hemoglobin (tHb, including glycated and unglycated hemoglobin), is considered one of the preferred indicators for diabetes monitoring. Generally, assessment of the HbA1c level requires separate determination of tHb and HbA1c concentrations after a complex separation step. This undoubtedly increases the cost of the assay, and the loss or degradation of HbA1c during the separation process results in a decrease in the accuracy of the assay. Therefore, this study explored a dual-signal acquisition method for the one-step simultaneous evaluation of tHb and HbA1c. Quantification of tHb: graphene adsorbed carbon quantum dots and methylene blue were utilized as the substrate material and linked to the antibody. tHb was captured on the substrate by the antibody. The unique heme group on tHb catalyzed the production of •OH from H2O2 to degrade methylene blue on the substrate, and a quantitative relationship between the tHb concentration and the methylene blue oxidation current signal was constructed. Quantification of HbA1c: complex labels with HbA1c recognition were made of ZIF-8-ferrocene-gold nanoparticles-mercaptophenylboronic acid. The specific recognition of the boronic acid bond with the unique cis-diol structure of HbA1c establishes a quantitative relationship between the oxidation current of the label-loaded ferrocene and the concentration of HbA1c. Thus, the HbA1c level can be assessed with only one signal readout. The sensor exhibited extensive detection ranges (0.200-600 ng/mL for tHb and 0.100-300 ng/mL for HbA1c) and low detection limits (4.00 × 10-3 ng/mL for tHb and 1.03 × 10-2 ng/mL for HbA1c).

Rational design of nanozyme with integrated sample pretreatment for colorimetric biosensing.

Nanozymes have been widely used in the field of biosensing owing to their high stability, low cost, adjustable catalytic activity, and convenient modification. However, achieving high selectivity and sensitivity simultaneously in nanozyme-based colorimetric sensing remains a major challenge. Nanozymes are nanomaterials with enzyme-simulating activity that are often used as solid-phase adsorbents for sample pretreatment. Our design strategy integrated sample pretreatment function into the nanozyme through separation and enrichment, thereby improving the selectivity and sensitivity of nanozyme-based colorimetric biosensing. As a proof-of-concept, glucose was used as the model analyte in this study. A phenylboric acid-modified magnetic nanozyme (Cu/Fe3O4@BA) was rationally designed and synthesized. Selectivity was enhanced by boronate-affinity specific adsorption and the elimination of interference after magnetic separation. In addition, magnetic solid-phase extraction enrichment was used to improve the sensitivity. A recovery rate of more than 80% was reached when the enrichment factor was 50. The synthesized magnetic Cu/Fe3O4@BA was recyclable at least five times. The proposed method exhibited excellent selectivity and sensitivity, simple operation, and recyclability, providing a novel and practical strategy for designing multifunctional nanozymes for biosensing.

Identification, crystallization, and first X-ray structure analyses of phenyl boronic acid-based inhibitors of human carbonic anhydrase-II.

Human carbonic anhydrases (hCAs) play a central role in various physiological processes in the human body. HCAs catalyze the reversible hydration of CO2 into HCO3-, and hence maintains the fluid and pH balance. Overexpression of CA II is associated with diseases, such as glaucoma, and epilepsy. Therefore, CAs are important clinical targets and inhibition of different isoforms, especially hCA II is used in treatment of glaucoma, altitude sickness, and epilepsy. Therapeutically used CA inhibitors (CAI) are sulfonamide-based, such as acetazolamide, dichlorphenamide, methazolamide, ethoxzolamide, etc. However, they exhibit several undesirable effects such as numbness, tingling of extremities, malaise, metallic taste, fatigue, renal calculi, and metabolic acidosis. Therefore, there is an urgent need to identify safe and effective inhibitors of the hCAs. In this study, different phenyl boronic acids 1-5 were evaluated against bovine (bCA II) and hCA II. Among all, compound 1 (4-acetylphenyl boronic acid) was found to be active against bCAII and hCA II with IC50 values of 246 ± 0.48 and 281.40 ± 2.8 µM, respectively, while the remaining compounds were found in-active. Compound 1 was identified as competitive inhibitor of hCA II enzyme (Ki = 283.7 ± 0.002 µM). Additionally, compound 1 was found to be non-toxic against BJ Human fibroblast cell line. The X-ray crystal structure for hCA II in-complex with compound 1 was evaluated to a resolution of 2.6 Å. In fact, this the first structural analysis of a phenyl boron-based inhibitor bound to hCA II, allowing an additional structure-activity analysis of the compounds. Compound 1 was found to be directly bound in the active site of hCA II by interacting with His94, His119, and Thr199 residues. In addition, a bond of 3.11 Å between the zinc ion and coordinated boron atom of the boronic acid moiety of compound 1 was also observed, contributing to binding affinity of compound 1 for hCA II. PDB ID: 8IGF.

Chemoselectivity Strategy Based on B-Label Integrated with Tailored COF for Targeted Metabolomic Analysis of Short-Chain Fatty Acids by UHPLC-MS/MS.

Chemoselective extraction strategy is an emerging and powerful means for targeted metabolomics analysis, which allows for the selective identification of biomarkers. Short-chain fatty acids (SCFAs) as functional metabolites for many diseases pose challenges in qualitative and quantitative analyses due to their high polarity and uneven abundance. In our study, we proposed the B-labeled method for the derivatization of SCFAs using easily available 3-aminobenzeneboronic acid as the derivatization reagent, which enables the introduction of recognition unit (boric acid groups). To analyze the B-labeled targeted metabolites accurately, cis-diol-based covalent organic framework (COF) was designed to specifically capture and release target compounds by pH-response borate affinity principle. The COF synthesized by the one-step Schiff base reaction possessed a large surface area (215.77 m2/g), excellent adsorption capacity (774.9 µmol/g), good selectivity, and strong regeneration ability (20 times). Combined with ultrahigh-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) analysis, our results indicated that the detection sensitivities of SCFAs increased by 1.2-2500 folds compared with unlabeled method, and the retention time and isomer separation were improved. Using this strategy, we determined twenty-six SCFAs in the serum and urine of rats in four groups about osteoporosis and identified important biomarkers related to the tricarboxylic acid cycle and fatty acid metabolism pathways. In summary, UHPLC-MS/MS based on B-labeled derivatization with tailored COF strategy shows its high selectivity, excellent sensitivity, and good chromatographic behavior and has remarkable application prospect in targeted metabolomics study of biospecimens.

The preparation of a boronate affinity-based controlled oriented imprinting coating on a silica nanoparticle surface for the separation and purification of shikimic acid in herbal medicine.

Shikimic acid (SA) is one of the most effective drugs against the A (H1N1) virus and has high medicinal value. Additionally, it has the ability to generate non-toxic herbicides and antimicrobial medications. The extraction from plants has proven to be the main route of production of SA with economic benefits and environmental efficiency. Therefore, it is necessary to perform purification of SA from these herbal medicines before quantifying it. In this study, researchers employed a boronate affinity-based controlled oriented surface imprinting technique to produce molecularly imprinted polymers (MIPs) as highly effective solid phase extraction (SPE) adsorbents for the isolation and purification of SA. 3-Fluoro-4-formylphenylboronic acid functionalized silica nanoparticles were used as supporting materials for immobilizing SA. Poly(2-anilinoethanol) with a higher hydrophilic domain can be used as an effective imprinting coating. The prepared SA-imprinted silica nanoparticles exhibited several significant results, such as good specificity, high binding capacity (39.06 ± 2.24 mg g-1), moderate binding constant (6.61 × 10-4 M-1), fast kinetics (8 min) and low binding pH (pH 5.0) toward SA. The replication of SA-imprinted silica nanoparticles was deemed satisfactory. The SA-imprinted silica nanoparticles could be still reused after seven adsorption-desorption cycles, which indicated high chemical stability. In addition, the recoveries of the proposed method for SA at three spiked level analysis in star aniseed and meadow cranesbill were 96.2% to 109.0% and 91.6% to 103.5%, respectively. The SA-imprinted silica nanoparticles that have been prepared are capable of identifying the target SA in real herbal medicines. Our approach makes sample pre-preparation simple, fast, selective and efficient.

Reversible Assembly of Proteins and Phenolic Polymers for Intracellular Protein Delivery with Serum Stability.

The design of intracellular delivery systems for protein drugs remains a challenge due to limited delivery efficacy and serum stability. Herein, we propose a reversible assembly strategy to assemble cargo proteins and phenolic polymers into stable nanoparticles for this purpose using a heterobifunctional adaptor (2-formylbenzeneboronic acid). The adaptor is easily decorated on cargo proteins via iminoboronate chemistry and further conjugates with catechol-bearing polymers to form nanoparticles via boronate diester linkages. The nanoparticles exhibit excellent serum stability in culture media but rapidly release the cargo proteins triggered by lysosomal acidity and GSH after endocytosis. In a proof-of-concept animal model, the strategy successfully transports superoxide dismutase to retina via intravitreal injection and efficiently ameliorates the oxidative stress and cellular damage in the retina induced by ischemia-reperfusion (I/R) with minimal adverse effects. The reversible assembly strategy represents a robust and efficient method to develop serum-stable systems for the intracellular delivery of biomacromolecules.

Mucoadhesive phenylboronic acid-grafted carboxymethyl cellulose hydrogels containing glutathione for treatment of corneal epithelial cells exposed to benzalkonium chloride.

Benzalkonium chloride (BAK) is the most commonly-used preservative in topical ophthalmic medications that may cause ocular surface inflammation associated with oxidative stress and dry eye syndrome. Glutathione (GSH) is an antioxidant in human tears and able to decrease the proinflammatory cytokine release from cells and reactive oxygen species (ROS) formation. Carboxymethyl cellulose (CMC), a hydrophilic polymer, is one of most commonly used artificial tears and can promote the corneal epithelial cell adhesion, migration and re-epithelialization. However, most of commercial artificial tears provide only temporary relief of irritation symptoms and show the short-term treatment effects. In the study, 3-aminophenylboronic acid was grafted to CMC for increase of mucoadhesive properties that might increase the precorneal retention time and maintain the effective therapeutic concentration on the ocular surface. CMC was modified with different degree of substitution (DS) and characterized by Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. Phenylboronic acid (PBA)-grafted CMC hydrogels have interconnected porous structure and shear thinning behavior. Modification of CMC with high DS (H-PBA-CMC) shows the strong bioadhesive force. The optimal concentration of GSH to treat corneal epithelial cells (CECs) was evaluated by cell viability assay. H-PBA-CMC hydrogels could sustained release GSH and decrease the ROS level. H-PBA-CMC hydrogels containing GSH shows the therapeutic effects in BAK-damaged CECs via improvement of inflammation, apoptosis and cell viability. After topical administration of developed hydrogels, there was no ocular irritation in rabbits. These results suggested that PBA-grafted CMC hydrogels containing GSH might have potential applications for treatment of dry eye disease.

A Co(III)-peroxo-arylboronate complex formed by nucleophilic reaction of a Co(III)-peroxo species.

In this work, we report the generation and characterization of two new Co(III)-peroxo complexes 2 and 3. 2 is best described as a mononuclear CoIII-(O2) complex that exhibits an 18O-isotope sensitive OO bond stretching vibration at 845(-49) cm-1, indicating a relatively weak peroxo moiety compared to those of other CoIII-(O2) complexes reported previously. Complex 3 is a CoIII-peroxo-arylboronate species having a rare {CoIIIOOBO} five-membered metallocycle, which is structurally characterized using X-ray crystallography. Investigations of the reaction mechanism using density functional theory calculations show that 2 likely undergoes a nucleophilic attack to an arylboronic acid, which is generated by hydrolysis of the BPh4- anion in wet acetonitrile solution, to first form a CoIII-peroxo-arylboronic acid adduct, followed by the loss of one benzene molecule to generate the five-membered metallocycle. The entire reaction is thermodynamically favorable. Taken together, the conversion of 2 to 3 represents the discovery of a novel nucleophilic reactivity that can be carried out by mononuclear Co(III)-peroxo complexes.

Ferrocene-Based Antioxidant Self-Healing Hydrogel via the Biginelli Reaction for Wound Healing.

The development of antioxidant wound dressings to remove excessive free radicals around wounds is essential for wound healing. In this study, we developed an efficient strategy to prepare antioxidant self-healing hydrogels as wound dressings by combining multicomponent reactions (MCRs) and postpolymerization modification. A polymer containing ferrocene and phenylboronic acid groups was developed via the Biginelli reaction, followed by efficient modification. This polymer is antioxidant due to its ferrocene moieties and can rapidly cross-link poly(vinyl alcohol) to realize an antioxidant self-healing hydrogel through dynamic borate ester linkages. This hydrogel has low cytotoxicity and is biocompatible. In in vivo experiments, this hydrogel is superior to existing clinical dressings in promoting wound healing. This study demonstrates the value of the Biginelli reaction in exploring biomaterials, potentially offering insights into the design of other multifunctional polymers and related materials using different MCRs.

Pyrene-Appended Boronic Acids on Graphene Foam Electrodes Provide Quantum Capacitance-Based Molecular Sensors for Lactate.

Molecular recognition and sensing can be coupled to interfacial capacitance changes on graphene foam surfaces linked to double layer effects and coupled to enhanced quantum capacitance. 3D graphene foam film electrodes (Gii-Sens; thickness approximately 40 µm; roughness factor approximately 100) immersed in aqueous buffer media exhibit an order of magnitude jump in electrochemical capacitance upon adsorption of a charged molecular receptor based on pyrene-appended boronic acids (here, 4-borono-1-(pyren-2-ylmethyl)pyridin-1-ium bromide, or abbreviated T1). This pyrene-appended pyridinium boronic acid receptor is employed here as a molecular receptor for lactate. In the presence of lactate and at pH 4.0 (after pH optimization), the electrochemical capacitance (determined by impedance spectroscopy) doubles again. Lactic acid binding is expressed with a Hillian binding constant (Klactate = 75 mol-1 dm3 and α = 0.8 in aqueous buffer, Klactate = 460 mol-1 dm3 and α = 0.8 in artificial sweat, and Klactate = 340 mol-1 dm3 and α = 0.65 in human serum). The result is a selective molecular probe response for lactic acid with LoD = 1.3, 1.4, and 1.8 mM in aqueous buffer media (pH 4.0), in artificial sweat (adjusted to pH 4.7), and in human serum (pH adjusted to 4.0), respectively. The role of the pyrene-appended boronic acid is discussed based on the double layer structure and quantum capacitance changes. In the future, this new type of molecular capacitance sensor could provide selective enzyme-free analysis without analyte consumption for a wider range of analytes and complex environments.

Boronate crosslinking-based ratiometric electrochemical assay of glycated albumin.

As a product of nonenzymatic glycation, glycated albumin (GA) is a promising serum marker for the short-term glycemic monitoring in patients with diabetes. On the basis of the boronate crosslinking (BCL)-enabled direct labeling of ferrocene (Fc) tags to the nonenzymatically glycated (NEG) sites, we report herein a novel aptamer-based ratiometric electrochemical (apt-REC) platform for the point-of-care (POC) assay of GA. This apt-REC platform is based on the recognition of GA proteins by the methylene blue (MB)-modified aptamer receptors and the labeling of the Fc tags to the NEG sites via the BCL. Using MB as the reference tag and Fc as the quantification tag, the ratio of the oxidation currents (i.e., IFc/IMB) can serve as the yardstick for the ratiometric assay of GA. Due to the presence of tens of the NEG sites, each GA protein can be labeled with tens of quantification tags, permitting the amplified assay in a simple, time-saving, and low-cost manner. The ratiometric signal exhibited a good linear response over the range from 0.1 to 100 µg/mL, with a detection limit of 45.5 ng/mL. In addition to the superior reproducibility and robustness, this apt-REC platform is highly selective (capable of discriminating GA against human serum albumin (HSA)) and applicable to GA assay in serum samples. Due to its low cost, high reproducibility and robustness, simple operation, and high sensitivity and selectivity, this apt-REC platform holds great promise in the POC assay of GA for diabetes management.

Simple Binding and Dissociation of a Sialoglycoprotein Using Boronic Acid-Modified Functional Interfaces on Microparticles.

An overexpression of sialic acid is an indicator of metastatic cancer, and selective detection of sialic acid shows potential for cancer diagnosis. Boronic acid is a promising candidate for this purpose because of its ability to specifically bind to sialic acid under acidic conditions. Notably, the binding strength can be easily modulated by adjusting the pH, which allows for a simple dissociation of the bound sialic acid. In this study, we developed 5-boronopicolinic acid (5-BPA)-modified magnetic particles (BMPs) to selectively capture sialic acid biomolecules. We successfully captured fetuin, a well-known sialoglycoprotein, on BMPs at >104 molecules/particle using an acetate buffer (pH 5.0). Facile dissociation then occurred when the system was changed to a pH 7.6 phosphate buffer. This capture-and-release process could be repeated at least five times. Moreover, this system could enrich fetuin by more than 20 times. In summary, BMPs are functional particles for facile purification and concentration through the selective capture of sialic acid proteins and can improve detection sensitivity compared with conventional methods. This technology shows potential for the detection of sialic acid overexpression by biological particles.

Surface Modification of Polystyrene with Boronic Acid for Immunoaffinity-Based Cell Enrichment.

Obtaining an enriched and phenotypically pure cell population from heterogeneous cell mixtures is important for diagnostics and biosensing. Existing techniques such as fluorescent-activated cell sorting (FACS) and magnetic-activated cell sorting (MACS) require preincubation with antibodies (Ab) and specialized equipment. Cell immunopanning removes the need for preincubation and can be done with no specialized equipment. The majority of the available antibody-mediated analyte capture techniques require a modification to the Abs for binding. In this work, no antibody modification is used because we take advantage of the carbohydrate chain in the Fc region of Ab. We use boronic acid as a cross-linker to bind the Ab to a modified surface. The process allows for functional orientation and cleavable binding of the Ab. In this study, we created an immunoaffinity matrix on polystyrene (PS), an inexpensive and ubiquitous plastic. We observed a 37% increase in Ab binding compared with that of a passive adsorption approach. The method also displayed a more consistent antibody binding with 17 times less variation in Ab loading among replicates than did the passive adsorption approach. Surface topography analysis revealed that a dextran coating reduced nonspecific antibody binding. Elemental analysis (XPS) was used to characterize the surface at different stages and showed that APBA molecules can bind upside-down on the surface. While upside-down antibodies likely remain functional, their elution behavior might differ from those bound in the desired way. Cell capture experiments show that the new surface has 43% better selectivity and 2.4-fold higher capture efficiency compared to a control surface of passively adsorbed Abs. This specific surface chemistry modification will allow the targeted capture of cells or analytes with the option of chemical detachment for further research and characterization.

Magnetic dendritic mesoporous silica nanoparticles based integrated platform for rapid and efficient analysis of saccharides.

BACKGROUND: As an essential compound in living organism, saccharides have attracted enormous attentions from scientists in various fields. Understanding the distribution of saccharides in various samples is of great scientific importance. However, the low signal response and lack of specific recognition technology of saccharides and the complex matrix of samples make the analysis of saccharides a very challenge task. Thus, the development of a simple and straightforward strategy for the analysis of saccharides would represent a great contribution to the field. RESULTS: In this study, by employing the sulfonyl functionalized magnetic dendritic mesoporous silica nanoparticles as the substrate, we develop an integrated platform for analysis of saccharides. The construction of the platform mainly relied on multi-functional boronic acid, which serves as separation and derivation ligands at the same time. In the general procedure, the boronic acid is first immobilized onto the surface of substrate, then the selective enrichment of saccharides can be realized via boronate affinity separation. Finally, by the rational choice of the solution, we are able to elute the labelled complex (boronic acid-saccharide) from the substrate, which can be direct subjected to HPLC-UV analysis. The reliable precision (<15 %), accuracy (80-100 %), reproducibility (<10 %), improved sensitivity (20x) and limited time-consuming (down to minutes) of the proposed platform are experimentally demonstrated. SIGNIFICANCE AND NOVELTY: The successful quantification of different saccharides (alditols, glucose) in real samples is achieved. The proposed strategy is not only straightforward and fast, but also avoid the requirement of special equipment. With these attractive features, we believe that this strategy will greatly prompt the analysis of saccharides in various samples (eg. food, pharmaceutics and biosamples).

The use of multicomponent reactions in the development of bis-boronic acids for the detection of ß-sialic acid.

Sialic acid (SA) is a naturally occurring monosaccharide found in glycoproteins and glycolipids. Changes in the expression of SA are associated with several diseases; thus, the detection of SA is of great significance for biological research, cancer diagnosis, and treatment. Boronic acid analogs have emerged as a promising tool for detecting sugars such as SA due to its reversible covalent bonding ability. In this study, 11 bis-boronic acid compounds and 2 mono-boronic acid compounds were synthesized via a highly efficient Ugi-4CR strategy. The synthesized compounds were subjected to affinity fluorescence binding experiments to evaluate their binding capability to SA. Compound A1 was shown to have a promising binding constant of 2602 ± 100 M-1 at pH = 6.0. Density Functional Theory (DFT) calculations examining the binding modes between A1 and SA indicated that the position of the boronic acid functional group was strongly correlated with its interaction with SA's α-hydroxy acid unit. The DFT calculations were consistent with the observations from the fluorescence experiments, demonstrating that the number and relative positions of the boronic acid functional groups are critical factors in enhancing the binding affinity to SA. DFT calculations of both S and R configuration of A1 indicated that the effect of the S/R configuration of A1 on its binding with ß-sialic acid was insignificant as the Ugi-4CR generated racemic products. A fluorine atom was incorporated into the R2 substituent of A1 as an electron-withdrawing group to produce A5, which possessed a significantly higher capability to bind to SA (Keq = 7015 ± 5 M-1 at pH = 6.0). Finally, A1 and A5 were shown to possess exceptional binding selectivity toward ß-sialic acid under pH of 6.0 and 6.5 while preferring to bind with glucose, fructose, and galactose under pH of 7.0 and 7.5.