Selective protein separation using siliceous materials with a trimethoxysilane-containing glycopolymer

Preparation and characterization of glycopolymers with biphenyl spacers via Suzuki coupling reaction

Poly(vinylbiphenyl)s bearing glycoside ligands at the side chains were prepared using the Suzuku coupling reaction. Effects of glycoside reactant concentration, halide species, glycoside species, and catalyst species on the incorporation of glycoside ligand into the polymer were investigated. The obtained glycopolymers exhibited specific binding to proteins corresponding to the glycoside ligands. In addition, the biphenyl spacers formed by the Suzuki coupling reaction in the glycopolymer were fluorescent, whereas the polymer precursor was not.

Formation of glyco-functionalized interfaces for protein binding using polyphenolic glycoside

In this study, a polyphenolic glycoside (α-glucosyl rutin) was used to form glyco-functionalized interfaces for protein binding. α-Glucosyl rutin was coated onto precious metals, metal oxides, and synthetic polymers, including polyethylene and polytetrafluoroethylene with poor surface modifiability. The glyco-functionalized interfaces bound strongly and specifically to concanavalin A and Bauhinia purpurea lectin, which have different carbohydrate specificities. Competitive adsorption tests demonstrated that the binding sites for the abovementioned lectins were glucosyl and rhamnosyl residues, respectively. The glyco-functionalized interfaces maintained the protein binding ability after being stored in aqueous solution for 1 day and in air for 160 days. Once the glyco-functionalized interfaces were formed on gold, silicon dioxide, polystyrene, and polytetrafluoroethylene using α-glucosyl rutin, all the glyco-functionalized interfaces bound to concanavalin A rather than peanut agglutinin.

Biopolymer monolith for protein purification

Porous glycopolymers, "glycomonoliths", were prepared by radical polymerization based on polymerization-induced phase separation with an acrylamide derivative of α-mannose, acrylamide and cross-linker in order to investigate protein adsorption and separation. The porous structure was induced by a porogenic alcohol. The pore diameter and surface area were controlled by the type of alcohol. The protein adsorption was measured in both batch and continuous flow systems. The glycomonoliths showed specific interaction with the sugar recognition protein of concanavalin A, and non-specific interaction to other proteins was negligible. The amount of protein adsorption to the materials was determined by the sugar density and the composition of the glycomonoliths. Fundamental knowledge regarding the glycomonoliths for protein separation was obtained.

Synthesis of well-defined glycopolymers with highly ordered sugar units in the side chain via combining CuAAC reaction and ROMP: lectin interaction study in homo- and hetero-glycopolymers

The design of novel heterogeneous glycopolymers with different sugar motifs is of critical importance in the glycopolymer field.

Fabrication of Carbohydrate Chips Based on Polydopamine for Real-Time Determination of Carbohydrate⁻Lectin Interactions by QCM Biosensor

A novel approach for preparing carbohydrate chips based on polydopamine (PDA) surface to study carbohydrate⁻lectin interactions by quartz crystal microbalance (QCM) biosensor instrument has been developed. The amino-carbohydrates were immobilized on PDA-coated quartz crystals via Schiff base reaction and/or Michael addition reaction. The resulting carbohydrate-chips were applied to QCM biosensor instrument with flow-through system for real-time detection of lectin⁻carbohydrate interactions. A series of plant lectins, including wheat germ agglutinin (WGA), concanavalin A (Con A), Ulex europaeus agglutinin I (UEA-I), soybean agglutinin (SBA), and peanut agglutinin (PNA), were evaluated for the binding to different kinds of carbohydrate chips. Clearly, the results show that the predicted lectin selectively binds to the carbohydrates, which demonstrates the applicability of the approach. Furthermore, the kinetics of the interactions between Con A and mannose, WGA and N-Acetylglucosamine were studied, respectively. This study provides an efficient approach to preparing carbohydrate chips based on PDA for the lectin⁻carbohydrate interactions study.

Functionalized Nano-adsorbent for Affinity Separation of Proteins

Thiol-functionalized silica nanospheres (SiO₂-SH NSs) with an average diameter of 460 nm were synthesized through a hydrothermal route. Subsequently, the prepared SiO₂-SH NSs were modified by SnO₂ quantum dots to afford SnO₂/SiO₂ composite NSs possessing obvious fluorescence, which could be used to trace the target protein. The SnO₂/SiO₂ NSs were further modified by reduced glutathione (GSH) to obtain SnO₂/SiO₂-GSH NSs, which can specifically separate glutathione S-transferase-tagged (GST-tagged) protein. Moreover, the peroxidase activity of glutathione peroxidase 3 (GPX3) separated from SnO₂/SiO₂-GSH NSs in vitro was evaluated. Results show that the prepared SnO₂/SiO₂-GSH NSs exhibit negligible nonspecific adsorption, high concentration of protein binding (7.4 mg/g), and good reused properties. In the meantime, the GST-tagged GPX3 separated by these NSs can retain its redox state and peroxidase activity. Therefore, the prepared SnO₂/SiO₂-GSH NSs might find promising application in the rapid separation and purification of GST-tagged proteins.

Tetra-nickel substituted polyoxotungsate as an efficient sorbent for the isolation of His6-tagged proteins from cell lysate

By virtue of the flexible structure of polyoxometalates, Ni²⁺ is encapsulated into trivacant lacunary tungstophosphate ligands by the form of [Ni₄] cluster to offer a tetra-nickel substituted polyoxotungsate K₆Na₄[Ni₄(H₂O)₂(PW₉O₃₄)₂] (Ni₄P₂). The Ni₄P₂ is then immobilized onto the surface of SiO₂ nanoparticles by self-assembly under electrostatic interactions to give the product of Ni₄P₂@SiO₂ composites. Due to the specific affinity between substituted Ni²⁺ in the polyoxotungsate and the histidine residues of protein, Ni₄P₂@SiO₂ composites exhibit highly adsorption selectivity towards histidine protein. This Ni₄P₂@SiO₂ composite is of high stability, and SDS-PAGE assay indicates that it can be used repeatedly as an efficient sorbent for the isolation of His6-tagged proteins from cell lysate with improved performance when compared with commercial NTA-Ni²⁺ column.

Graphene-Embedded Hydrogel Nanofibers for Detection and Removal of Aqueous-Phase Dyes

A facile route to graphene/polymer hydrogel nanofibers was developed. An aqueous dispersion of graphene (containing >40% bilayer graphene flakes) stabilized by a functionalized water-soluble polymer with phenyl side chains was successfully electrospun to yield nanofibers. Subsequent vapor-phase cross-linking of the nanofibers produced graphene-embedded hydrogel nanofibers (GHNFs). Interestingly, the GHNFs showed chemical sensitivity to the cationic dyes methylene blue (MB) and crystal violet (CV) in the aqueous phase. The adsorption capacities were as high as 0.43 and 0.33 mmol g^-1 s^-1 for MB and CV, respectively, even in a 1.5 mL s^-1 flow system. A density functional theory calculation revealed that aqueous-phase MB and CV dyes were oriented parallel to the graphene surface and that the graphene/dye ensembles were stabilized by secondary physical bonding mechanisms such as the π-π stacking interaction in an aqueous medium. The GHNFs exhibited electrochemical properties arising mainly from the electric double-layer capacitance, which were applied in a demonstration of GHNF-based membrane electrodes (5 cm in diameter) for detecting the dyes in the flow system. It is believed that the GHNF membrane can be a successful model candidate for commercialization of graphene due to its easy-to-fabricate process and remarkable properties.

Glycopolymer monoliths for affinity bioseparation of proteins in a continuous-flow system: glycomonoliths

Macroporous materials, called glycomonoliths, were prepared from saccharide-containing monomers, and applied for affinity bioseparation of proteins in a continuous-flow system.

Glyconanomaterials for biosensing applications

Nanomaterials constitute a class of structures that have unique physiochemical properties and are excellent scaffolds for presenting carbohydrates, important biomolecules that mediate a wide variety of important biological events. The fabrication of carbohydrate-presenting nanomaterials, glyconanomaterials, is of high interest and utility, combining the features of nanoscale objects with biomolecular recognition. The structures can also produce strong multivalent effects, where the nanomaterial scaffold greatly enhances the relatively weak affinities of single carbohydrate ligands to the corresponding receptors, and effectively amplifies the carbohydrate-mediated interactions. Glyconanomaterials are thus an appealing platform for biosensing applications. In this review, we discuss the chemistry for conjugation of carbohydrates to nanomaterials, summarize strategies, and tabulate examples of applying glyconanomaterials in in vitro and in vivo sensing applications of proteins, microbes, and cells. The limitations and future perspectives of these emerging glyconanomaterials sensing systems are furthermore discussed.

A facile strategy to fabricate covalently linked raspberry-like nanocomposites with pH and thermo tunable structures

A simple and controllable route to prepare covalently bonded raspberry-like composite particles with pH and thermal dual-responsiveness.

One-step synthesis of dual clickable nanospheres via ultrasonic-assisted click polymerization for biological applications

Dual clickable nanospheres (DCNSs) were synthesized in one step using an efficient approach of ultrasonic-assisted azide-alkyne click polymerization, avoiding the need of surfactants. This novel approach presents a direct clickable monomer-to-nanosphere synthesis. Field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), and dynamic laser scattering (DLS) were used to characterize the synthesized DCNSs. Numerous terminal alkynyl and azide groups on the surface of DCNSs facilitate effective conjugation of multiple molecules or ligands onto a single nanocarrier platform under mild conditions. To exemplify the potential of DCNSs in biological applications, (1) multivalent glyconanoparticles (GNPs) were prepared by clicking DCNSs with azide-functionalized and alkyne-functionalized lactose sequentially for the determination of carbohydrate-galectin interactions with quartz crystal microbalance (QCM) biosensor. Using protein chip (purified galectin-3 coated on chip) and cell chip (Jurkat cells immobilized on chip), the QCM sensorgrams showed excellent binding activity of GNPs for galectins; (2) fluorescent GNPs were prepared by clicking DCNSs with azide-functionalized Rhodamine B and alkyne-functionalized lactose sequentially in order to target galectin, which is overexpressed on the surface of Jurkat cells. The fluorescent images obtained clearly showed the cellular internalization of fluorescent GNPs. This fluorescent probe could be easily adapted to drugs to construct lectin-targeted drug delivery systems. Thus, DCNSs prepared with our method may provide a wide range of potential applications in glycobiology and biomedicine.

Metal mesh device sensor immobilized with a trimethoxysilane-containing glycopolymer for label-free detection of proteins and bacteria

Biosensors for the detection of proteins and bacteria have been developed using glycopolymer-immobilized metal mesh devices. The trimethoxysilane-containing glycopolymer was immobilized onto a metal mesh device using the silane coupling reaction. The surface shape and transmittance properties of the original metal mesh device were maintained following the immobilization of the glycopolymer. The mannose-binding protein (concanavalin A) could be detected at concentrations in the range of 10(-9) to 10(-6) mol L(-1) using the glycopolymer-immobilized metal mesh device sensor, whereas another protein (bovine serum albumin) was not detected. A detection limit of 1 ng mm(-2) was achieved for the amount of adsorbed concanavalin A. The glycopolymer-immobilized metal mesh device sensor could also detect bacteria as well as protein. The mannose-binding strain of Escherichia coli was specifically detected by the glycopolymer-immobilized metal mesh device sensor. The glycopolymer-immobilized metal mesh device could therefore be used as a label-free biosensor showing high levels of selectivity and sensitivity toward proteins and bacteria.

Synthesis of petal-like ferric oxide/cysteine architectures and their application in affinity separation of proteins

Petal-like ferric oxide/cysteine (FeOOH/Cys) architectures were prepared through a solvothermal route, which possessed high thiol group density. These thiol groups as binding sites can chelate Ni(2+) ions, which can be further used to enrich and separate his-tagged proteins directly from the mixture of lysed cells without sample pretreatment. These results show that the FeOOH/Cys architectures with immobilized Ni(2+) ions present negligible nonspecific protein adsorption and high protein adsorption capacity, with the saturation capacity being 88mg/g, which are especially suitable for purification of his-tagged proteins.

Signal amplified two-dimensional photonic crystal biosensor immobilized with glyco-nanoparticles

A two-dimensional, glycopolymer-immobilized, photonic crystal (PhC) biosensor was developed for the detection of proteins.

Ferroferric oxide/l-cysteine magnetic nanospheres for capturing histidine-tagged proteins

Ferroferric oxide/l-cysteine (Fe₃O₄/Cys) nanospheres (NSs) have been successfully synthesized via a facile solvothermal route. Fe₃O₄/Cys NSs possessed high thiol group density and saturation magnetization (M_s) of 84.6 emu g^-1. The prepared magnetic NSs are biocompatible and manipulatable by an external magnetic force. After chelating Ni²⁺ ions, Fe₃O₄/Cys-Ni²⁺ NSs were used to enrich and purify histidine-tagged (His-tagged) proteins directly from the mixture of lysed cells without pretreatment. It has been found that Fe₃O₄/Cys-Ni²⁺ NSs present negligible nonspecific protein adsorption and high protein binding activity with the saturation capacity being 53.2 μg mg^-1 and they are especially suitable for rapid purification of His-tagged proteins.