Nanoparticle-supported polymer brushes for temperature-regulated glycoprotein separation: investigation of structure-function relationship

Preparation of nickel-chelated iminodiacetate-functionalized macroporous agarose monolith using modular and clickable building blocks for affinity separation of histidine-tagged recombinant proteins

Selective separation and purification of protein from complex medium is required to completely investigate the structure and function of the target protein. In this study, a composite macroporous agarose monolith containing iminodiacetate-chelated Ni²⁺ ligands was synthesized for selective separation and purification of histidine-tagged recombinant proteins. The large and interconnected pores in the monolith enabled fast binding of proteins with high matrix tolerance in treating complex mediums. To realize the selective protein binding, the iminodiacetate was directly conjugated to epoxy-functionalized agarose monolith via simple chemical reactions between epoxy and imino groups. After chelated Ni²⁺, the composite monolith could bind histidine-tagged recombinant proteins through the coordination interaction between transition metal ions and the imidazole ring of histidine. To further increase the binding capacities of the monolith, a hydrophilic intermediate polymer chain containing multiple iminodiacetate immobilization sites was conjugated to the azide-functionalized agarose monolith via Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction. The morphology and chemical composition of the composite agarose monolith were characterized systematically. The protein binding capacities of the obtained composite agarose monolith were subsequently investigated. The binding capacities of the composite agarose monolith towards the model proteins Gp10 and Lys84 were 0.93 and 0.51 mg/mL, respectively. The protein binding of the composite agarose monolith could be manipulated by adjusting the temperature and concentrations of imidazole. These results demonstrate that the composite agarose monolith could be used as an affinity medium for rapid separation and purification of histidine-tagged recombinant proteins from biological samples.

Hyperbranched polymers as superior adsorbent for the treatment of dyes in water

The effective control on environmental pollutants is crucial for the proper management of diverse environmental systems (e.g., soil, water, and air). In this respect, the utility of various functional materials such as hyperbranched polymers (HPs) has been recognized due to their great potentil as adsorbent for the mitigation of numerous environmental pollutants. Here, we highlight the latest progress achieved in the design and construction of HPs with high adsorption potentials. We focus on adsorption mechanisms, functionalization methods, the role of functional groups in adsorption capacity, and the choice of HPs in adsorption of cationic and anionic dyes. Recent published reports are reviewed to quantify and qualify the removal efficiency of pollutants through adsorption. We also evaluate the adsorbing efficiency of the constructed HPs and compared their performance with other such systems. The utilization potential of new materials (magnetic, polar, and biological) is highlighted along with the methods needed for their preparation and/or modification (surface, end-group, and zwitterionic) for the construction of efficient adsorbing systems. Finally, the advantages and limitations of adsorbing systems are described along with the existing challenges to help establish guidelines for future research. This article is thus expected to offer new path and guidance for developing advanced HP-based adsorbents.

Probing polymer brushes with electrochemical impedance spectroscopy: a mini review

Polymer brushes are frequently used as surface-tethered antifouling layers in biosensors to improve sensor surface-analyte recognition in the presence of abundant non-target molecules in complex biological samples by suppressing nonspecific interactions. However, because brushes are complex systems highly responsive to changes in their surrounding environment, studying their properties remains a challenge. Electrochemical impedance spectroscopy (EIS) is an emerging method in this context. In this mini review, we aim to elucidate the potential of EIS for investigating the physicochemical properties and structural aspects of polymer brushes. The application of EIS in brush-based biosensors is also discussed. Most common principles employed in these biosensors are presented, as well as interpretation of EIS data obtained in such setups. Overall, we demonstrate that the EIS-polymer brush pairing has a considerable potential for providing new insights into brush functionalities and designing highly sensitive and specific biosensors.

Functionalized Particles Designed for Targeted Delivery

Pure bioactive compounds alone can only be exceptionally administered in medical treatment. Usually, drugs are produced as various forms of active compounds and auxiliary substances, combinations assuring the desired healing functions. One of the important drug forms is represented by a combination of active substances and particle-shaped polymer in the nano- or micrometer size range. The review describes recent progress in this field balanced with basic information. After a brief introduction, the paper presents a concise overview of polymers used as components of nano- and microparticle drug carriers. Thereafter, progress in direct synthesis of polymer particles with functional groups is discussed. A section is devoted to formation of particles by self-assembly of homo- and copolymer-bearing functional groups. Special attention is focused on modification of the primary functional groups introduced during particle preparation, including introduction of ligands promoting anchorage of particles onto the chosen living cell types by interactions with specific receptors present in cell membranes. Particular attention is focused on progress in methods suitable for preparation of particles loaded with bioactive substances. The review ends with a brief discussion of the still not answered questions and unsolved problems.

Tailor-made magnetic nanocomposite with pH and thermo-dual responsive copolymer brush for bacterial separation

Rapid detection of pathogenic bacteria particularly in food samples demands efficient separation and enrichment strategies. Here, hydrophilic temperature-responsive boronate affinity magnetic nanocomposites were established for selective enrichment of bacteria. The thermo-responsive polymer brushes were developed by surface-initiated atom transfer radical polymerization of N-isopropylacrylamide (NIPAm) and allyl glycidyl ether (AGE), followed by a reaction of epoxy groups, and incorporation of fluorophenylboronic acid. The physical and chemical characteristics of the magnetic nanocomposites were analyzed systematically. After optimization, S. aureus and Salmonella spp. showed high binding capacities of 32.14 × 10⁶ CFU/mg and 50.98 × 10⁶ CFU/mg in 0.01 M PBS (pH 7.4) without bacteria death. Bacterial bindings can be controlled by altering temperature and the application of competing monosaccharides. The nanocomposite was then utilized to enrich S. aureus and Salmonella spp. from the spiked tap water, 25% milk, and turbot extraction samples followed by multiplex polymerase chain reaction (mPCR), which resulted in high bacteria enrichment, and demonstrated great potential in separation of bacteria from food samples.

Boronic Acid Functionalized Nanosilica for Binding Guest Molecules

Dendritic fibrous nanosilica (DFNS) has very high surface area and well-defined nanochannels; therefore, it is very useful as supporting material for numerous applications including catalysis, sensing, and bioseparation. Due to the highly restricted space, addition of molecular ligands to DFNS is very challenging. This work studies how ligand conjugation in nanoscale pores in DFNS can be achieved through copper-catalyzed click reaction, using an optional, in situ synthesized, temperature-responsive polymer intermediate. A clickable boronic acid is used as a model to investigate the ligand immobilization and the molecular binding characteristics of the functionalized DFNS. The morphology, composition, nanoscale pores, and specific surface area of the boronic acid functionalized nanosilica were characterized by electron microscopy, thermogravimetric and elemental analysis, Fourier transform infrared spectroscopy, and nitrogen adsorption-desorption measurements. The numbers of boronic acid molecules on the modified DFNS with and without the polymer were determined to be 0.08 and 0.68 mmol of ligand/g of DFNS, respectively. We also studied the binding of small cis-diol molecules in the nanoscale pores of DFNS. The boronic acid modified DFNS with the polymer intermediate exhibits higher binding capacity for Alizarin Red S and nicotinamide adenine dinucleotide than the polymer-free DFNS. The two types of boronic acid modified DFNS can bind small cis-diol molecules in the presence of large glycoproteins, due in large part to the effect of size exclusion provided by the nanochannels in the DFNS.

Photoconjugation of temperature- and pH-responsive polymer with silica nanoparticles for separation and enrichment of bacteria

A new photoconjugation approach was developed to prepare nanoparticle-supported boronic acid polymer for effective separation and enrichment of bacteria. The photo-activated polymer immobilization was demonstrated by coupling an azide-modified copolymer of N-isopropylacrylamide and glycidyl methacrylate to a perfluorophenyl azide-modified silica surface. The thermoresponsive polymer was synthesized using reversible addition fragmentation chain transfer polymerization followed by conversion of the pendant epoxides into azide groups. The perfluorophenyl azide-modified silica nanoparticles were synthesized by an amidation reaction between amino-functionalized silica and pentafluorobenzoyl chloride, and a subsequent treatment with sodium azide. Bacteria-capturing boronic acid was conjugated to the silica-supported polymer chains via Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) click reaction. The particle size, morphology and organic content of the composite nanoparticles were characterized systematically. The capability of the nanocomposite to bind Gram-positive and Gram-negative bacteria was investigated. The nanocomposite exhibited high binding capacities for E. coli (13.4 × 10⁷ CFU/mg) and S. epidermidis (7.66 × 10⁷ CFU/mg) in phosphate buffered saline. The new photoconjugation strategy enables fast and straightforward grafting of functional polymers on surface, which opens many new opportunities for designing functional materials for bioseparation and biosensing.

Iron-chelated thermoresponsive polymer brushes on bismuth titanate nanosheets for metal affinity separation of phosphoproteins

Separation of phosphoproteins plays an important role for identification of biomarkers in life science. In this work, bismuth titanate supported, iron-chelated thermoresponsive polymer brushes were prepared for selective separation of phosphoproteins. The iron-chelated thermoresponsive polymer brushes were synthesized by surface-initiated atom transfer radical polymerization of N-isopropylacrylamide and glycidyl methacrylate, followed by a ring opening reaction of epoxy group, and chelation of the obtained cis-diols with Fe³⁺ ions. The composite material was characterized to determine the size and thickness, the content of the organic polymer and the metal loading. The bismuth titanate supported, iron-chelated thermoresponsive polymer brushes showed selective binding for phosphoproteins in the presence of abundant interfering proteins, and a high binding capacity for phosphoproteins by virtue of the metal affinity between the metal ions on the polymer brushes and the phosphate groups in the phosphoproteins (664 mg β-Casein per g sorbent). The thermoresponsive property of the polymer brushes made it possible to adjust phosphoprotein binding by changing temperature. Finally, separation of phosphoproteins from a complex biological sample (i.e. milk) was demonstrated using the nanosheet-supported thermoresponsive polymer brushes.

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.

A facile and general approach for the preparation of boronic acid-functionalized magnetic nanoparticles for the selective enrichment of glycoproteins

Biomedical applications and biomarkers for early clinical diagnostics and the treatment of diseases demand efficient and selective enrichment platforms for glycoproteins.

Facile fabrication of a “Catch and Release” cellulose acetate nanofiber interface: a platform for reversible glycoprotein capture and bacterial attachment

We disclose boronic acid ligand-functionalized electrospun cellulose acetate nanofiber mats that can be used as a platform for reversible glycoprotein capture and bacterial attachment.