Glycopolymer-Functionalized Cryogels as Catch and Release Devices for the Pre-Enrichment of Pathogens

Modification of 3D-Printed PLA Structures Using Photo-Iniferter Polymerization: Toward On-Demand Antimicrobial Water Filters

Water filtration is an important application to ensure the accessibility of clean drinking water. As requirements and contaminants vary on a local level, adjustable filter devices and their evaluation with contaminants are required. Within this work, modular filter devices are designed featuring an adjustable surface functionalization. For this purpose, 3D-printed structures are created consisting of bio-based poly(lactic acid) (PLA) that are manufactured by extrusion printing. The surface of PLA is activated with amino groups that are used to install xanthates as chain transfer agents. Subsequently, photo-iniferter (PI) polymerization is used to create cationic polymer brushes on the surface of PLA substrates. Multiple surface characterization techniques are employed to prove successful growth of polymer brushes on PLA. After initial optimization studies on flat surfaces, filter devices are printed, functionalized, and used to remove bacteria from contaminated water. Significant reduction of the number of microorganisms is detected after filtration (single filtration or cycling) and contaminating organism can also be removed from freshwater samples by simple incubation with a 3D-printed filter. The herein developed setup for producing functional filter devices and probing their performance in affinity filtration is a useful platform technology, enabling the rapid testing of polymer brushes for such applications.

Glycan-Presenting Coacervates Derived from Charged Poly(active esters): Preparation, Phase Behavior, and Lectin Capture

This study presents the preparation and phase behavior of glycan-functionalized polyelectrolytes for capturing carbohydrate-binding proteins and bacteria in liquid condensate droplets. The droplets are formed by complex coacervation of poly(active ester)-derived polyanions and polycations. This approach allows for a straightforward modular introduction of charged motifs and specifically interacting units; mannose and galactose oligomers are used here as first examples. The introduction of carbohydrates has a notable effect on the phase separation and the critical salt concentration, potentially by reducing the charge density. Two mannose binding species, concanavalin A (ConA) and Escherichia coli, are shown to not only specifically bind to mannose-functionalized coacervates but also to some degree to unfunctionalized, carbohydrate-free coacervates. This suggests non-carbohydrate-specific charge-charge interactions between the protein/bacteria and the droplets. However, when mannose interactions are inhibited or when non-binding galactose-functionalized polymers are used, interactions are significantly weakened. This confirms specific mannose-mediated binding functionalization and suggests that introducing carbohydrates reduces non-specific charge-charge interactions by a so far unidentified mechanism. Overall, the presented route toward glycan-presenting polyelectrolytes enables new functional liquid condensate droplets with specific biomolecular interactions.

Dimethylsulfoniopropionate decorated cryogels as synthetic spatially structured habitats of marine bacterial communities

In microbial consortia bacteria often settle on other organisms that provide nutrients and organic material for their growth. This is true for the plankton where microalgae perform photosynthesis and exude metabolites that feed associated bacteria. The investigation of such processes is difficult since algae provide bacteria with a spatially structured environment with a gradient of released organic material that is hard to mimic. Here we introduce the design and synthesis of a cryogel-based microstructured habitat for bacteria that provides dimethylsulfoniopropionate (DMSP) as a carbon and sulfur source for growth. DMSP, a widely distributed metabolite released by algae, is thereby made available for bacteria in a biomimetic manner. Based on a novel DMSP derived building block (DMSP-HEMA), we synthesized cryogels providing structured surfaces for settlement and delivering the organic material fueling bacterial growth. By monitoring bacterial settlement and performance we show that the cryogels represent microbial arenas mimicking the ecological situation in the plankton.

Glycopolymers against pathogen infection

Pathogens including viruses, bacteria, fungi, and parasites continue to shape our lives in profound ways every day. As we have learned to live in parallel with pathogens, we have gained a better understanding of the rules of engagement for how they bind, adhere, and invade host cells. One such mechanism involves the exploitation of host cell surface glycans for attachment/adhesion, one of the first steps of infection. This knowledge has led to the development of glycan-based diagnostics and therapeutics for the treatment and prevention of infection. One class of compounds that has become increasingly important are the glycopolymers. Glycopolymers are macromolecules composed of a synthetic scaffold presenting carbohydrates as side chain motifs. Glycopolymers are particularly attractive because their properties can be tuned by careful choice of the scaffold, carbohydrate/glycan, and overall presentation. In this review, we highlight studies over the past ten years that have examined the role of glycopolymers in pathogen adhesion and host cell infection, biofilm formation and removal, and drug delivery with the aim of examining the direct effects of these macromolecules on pathogen engagement. In addition, we also examine the role of glycopolymers as diagnostics for the detection and monitoring of pathogens.

Tailor-made Glycopolymers via Reversible Deactivation Radical Polymerization: Design, Properties and Applications

Investigating the underlying mechanism of biological interactions using glycopolymer is becoming increasingly important owing to their unique recognition properties. The multivalent interactions between lectin and glycopolymer are significantly influenced by...

Combining Inducible Lectin Expression and Magnetic Glyconanoparticles for the Selective Isolation of Bacteria from Mixed Populations

The selective isolation of bacteria from mixed populations has been investigated in varied applications ranging from differential pathogen identification in medical diagnostics and food safety to the monitoring of microbial stress dynamics in industrial bioreactors. Selective isolation techniques are generally limited to the confinement of small populations in defined locations, may be unable to target specific bacteria, or rely on immunomagnetic separation, which is not universally applicable. In this proof-of-concept work, we describe a novel strategy combining inducible bacterial lectin expression with magnetic glyconanoparticles (MGNPs) as a platform technology to enable selective bacterial isolation from cocultures. An inducible mutant of the type 1 fimbriae, displaying the mannose-specific lectin FimH, was constructed in Escherichia coli allowing for "on-demand" glycan-binding protein presentation following external chemical stimulation. Binding to glycopolymers was only observed upon fimbrial induction and was specific for mannosylated materials. A library of MGNPs was produced via the grafting of well-defined catechol-terminal glycopolymers prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization to magnetic nanoparticles. Thermal analysis revealed high functionalization (≥85% polymer by weight). Delivery of MGNPs to cocultures of fluorescently labeled bacteria followed by magnetic extraction resulted in efficient depletion of type 1 fimbriated target cells from wild-type or afimbriate E. coli. Extraction efficiency was found to be dependent on the molecular weight of the glycopolymers utilized to engineer the nanoparticles, with MGNPs decorated with shorter Dopa-(ManAA)₅₀ mannosylated glycopolymers found to perform better than those assembled from a longer Dopa-(ManAA)₂₀₀ analogue. The extraction efficiency of fimbriated E. coli was also improved when the counterpart strain did not harbor the genetic apparatus for the expression of the type 1 fimbriae. Overall, this work suggests that the modulation of the genetic apparatus encoding bacterial surface-associated lectins coupled with capture through MGNPs could be a versatile tool for the extraction of bacteria from mixed populations.

Polymeric Materials Used for Immobilisation of Bacteria for the Bioremediation of Contaminants in Water

Bioremediation is a key process for reclaiming polluted soil and water by the use of biological agents. A commonly used approach aims to neutralise or remove harmful pollutants from contaminated areas using live microorganisms. Generally, immobilised microorganisms rather than planktonic cells have been used in bioremediation methods. Activated carbon, inorganic minerals (clays, metal oxides, zeolites), and agricultural waste products are acceptable substrates for the immobilisation of bacteria, although there are limitations with biomass loading and the issue with leaching of bacteria during the process. Various synthetic and natural polymers with different functional groups have been used successfully for the efficient immobilisation of microorganisms and cells. Promise has been shown using macroporous materials including cryogels with entrapped bacteria or cells in applications for water treatment and biotechnology. A cryogel is a macroporous polymeric gel formed at sub-zero temperatures through a process known as cryogelation. Macroporous hydrogels have been used to make scaffolds or supports for immobilising bacterial, viral, and other cells. The production of composite materials with immobilised cells possessing suitable mechanical and chemical stability, porosity, elasticity, and biocompatibility suggests that these materials are potential candidates for a range of applications within applied microbiology, biotechnology, and research. This review evaluates applications of macroporous cryogels as tools for the bioremediation of contaminants in wastewater.

Temperature-Controlled Adhesion to Carbohydrate Functionalized Microgel Films: An E. coli and Lectin Binding Study

The preparation of thermoresponsive mannose functionalized monolayers of poly(N-isopropylacrylamide) microgels and the analysis of the specific binding of concanavalin A (ConA) and E. coli above and below the lower critical solution temperature (LCST) are shown. Via inhibition and direct binding assays it is found that ConA binding is time-dependent, where at short incubation times binding is stronger above the LCST. Given larger incubation times, the interaction of ConA to the microgel network is increased below the LCST when compared to temperatures above the LCST, possibly due to increased ConA diffusion and multivalent binding in the more open microgel network below the LCST. For E. coli, which presents only monovalent lectins and is too large to diffuse into the network, binding is always enhanced above the LCST. This is due to the larger mannose density of the microgel layer above the LCST increasing the interaction to E. coli. Once bound to the microgel layer above the LCST, E. coli cannot be released by cooling down below the LCST. Overall, this suggests that the carbohydrate presenting microgel layers enable specific binding where the temperature-induced transition between swollen and collapsed microgels may increase or decrease binding depending on the receptor size.

Optimization of the Microwave Assisted Glycosylamines Synthesis Based on a Statistical Design of Experiments Approach

Glycans carry a vast range of functions in nature. Utilizing their properties and functions in form of polymers, coatings or glycan derivatives for various applications makes the synthesis of modified glycans crucial. Since amines are easy to modify for subsequent reactions, we investigated regioselective amination conditions of different saccharides. Amination reactions were performed according to Kochetkov and Likhoshertov and accelerated by microwave irradiation. We optimized the synthesis of glycosylamines for N-acetyl-d-galactosamine, d-lactose, d-glucuronic acid and l-(-)-fucose using the design of experiments (DoE) approach. DoE enables efficient optimization with limited number of experimental data. A DoE software generated a set of experiments where reaction temperature, concentration of carbohydrate, nature of aminating agent and solvent were investigated. We found that the synthesis of glycosylamines significantly depends on the nature of the carbohydrate and on the reaction temperature. There is strong indication that high temperatures are favored for the amination reaction.

Glycopolymer Brushes by Reversible Deactivation Radical Polymerization: Preparation, Applications, and Future Challenges

The cellular surface contains specific proteins, also known as lectins, that are carbohydrates receptors involved in different biological events, such as cell-cell adhesion, cell recognition and cell differentiation. The synthesis of well-defined polymers containing carbohydrate units, known as glycopolymers, by reversible deactivation radical polymerization (RDRP) methods allows the development of tailor-made materials with high affinity for lectins because of their multivalent interaction. These polymers are promising candidates for the biomedical field, namely as novel diagnostic disease markers, biosensors, or carriers for tumor-targeted therapy. Although linear glycopolymers are extensively studied for lectin recognition, branched glycopolymeric structures, such as polymer brushes can establish stronger interactions with lectins. This specific glycopolymer topology can be synthesized in a bottlebrush form or grafted to/from surfaces by using RDRP methods, allowing a precise control over molecular weight, grafting density, and brush thickness. Here, the preparation and application of glycopolymer brushes is critically discussed and future research directions on this topic are suggested.

Controlled synthesis of sugar-containing poly(ionic liquid)s

A facile synthetic route is reported toward sugar-containing pyridinium-based poly(ionic liquid)s (PILs) for efficient killing of bacteria.

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.

An on-site bacterial detection strategy based on broad-spectrum antibacterial ε-polylysine functionalized magnetic nanoparticles combined with a portable fluorometer

A sensitive on-site bacterial detection strategy is presented that integrates the broad-spectrum capturing feature of ε-polylysine-functionalized magnetic nanoparticles with an in-house built portable fluorometer. Based on the electrostatic interaction, the functionalized magnetic nanoparticles (ε-PL-MNPs) were prepared for Gram-positive and Gram-negative bacterial separation and subsequent viable release. ε-PL-MNPs show a broad reactivity towards bacteria with the high capture efficiency from real-world sample media. They also enable controlled viable bacterial release with pH adjustment. Detection of bacteria is based on a combination of broad-spectrum capture with colorimetric and fluorimetric immunoassays. A portable fluorometer is built to enhance the applicability for sensitive on-site detection. A limit of detection of 98 CFU·mL^-1 is achieved that is comparable to that of a known spectrofluorometric method for E. coli DH5α. Graphical abstract Schematic presentation of bacterial capture using cationic polymer functionalized magnetic nanoparticles and general fluorometric immunoassay with portable fluorometer. The limit of detection is 98 CFU·mL^-1 for E. coli DH5α.

Artificial Microbial Arenas: Materials for Observing and Manipulating Microbial Consortia

From the smallest ecological niche to global scale, communities of microbial life present a major factor in system regulation and stability. As long as laboratory studies remain restricted to single or few species assemblies, however, very little is known about the interaction patterns and exogenous factors controlling the dynamics of natural microbial communities. In combination with microfluidic technologies, progress in the manufacture of functional and stimuli-responsive materials makes artificial microbial arenas accessible. As habitats for natural or multispecies synthetic consortia, they are expected to not only enable detailed investigations, but also the training and the directed evolution of microbial communities in states of balance and disturbance, or under the effects of modulated stimuli and spontaneous response triggers. Here, a perspective on how materials research will play an essential role in generating answers to the most pertinent questions of microbial engineering is presented, and the concept of adaptive microbial arenas and possibilities for their construction from particulate microniches to 3D habitats is introduced. Materials as active and tunable components at the interface of living and nonliving matter offer exciting opportunities in this field. Beyond forming the physical horizon for microbial cultivates, they will enable dedicated intervention, training, and observation of microbial consortia.

Supermacroporous Composite Cryogels in Biomedical Applications

Supermacroporous gels, called cryogels, are unique scaffolds that can be prepared by polymerization of monomer solution under sub-zero temperatures. They are widely used in many applications and have significant potential biomaterials, especially for biomedical applications due to their inherent interconnected supermacroporous structures and easy formation of composite polymers in comparison to other porous polymer synthesis techniques. This review highlights the fundamentals of supermacroporous cryogels and composite cryogels, and then comprehensively summarizes recent studies in preparation, functionalization, and utilization with mechanical, biological and physicochemical features, according to the biomedical applications. Furthermore, conclusions and outlooks are discussed for the use of these promising and durable supermacroporous composite cryogels.

Polydimethylsiloxane-Based Giant Glycosylated Polymersomes with Tunable Bacterial Affinity

A synthetic cell mimic in the form of giant glycosylated polymersomes (GGPs) comprised of a novel amphiphilic diblock copolymer is reported. A synthetic approach involving a poly(dimethylsiloxane) (PDMS) macro-chain transfer agent (macroCTA) and postpolymerization modification was used to marry the hydrophobic and highly flexible properties of PDMS with the biological activity of glycopolymers. 2-Bromoethyl acrylate (BEA) was first polymerized using a PDMS macroCTA ( M_n,th ≈ 4900 g·mol^-1, Đ = 1.1) to prepare well-defined PDMS- b-pBEA diblock copolymers ( Đ = 1.1) that were then substituted with 1-thio-β-d-glucose or 1-thio-β-d-galactose under facile conditions to yield PDMS- b-glycopolymers. Compositions possessing ≈25% of the glycopolymer block (by mass) were able to adopt a vesicular morphology in aqueous solution (≈210 nm in diameter), as indicated by TEM and light scattering techniques. The resulting carbohydrate-decorated polymersomes exhibited selective binding with the lectin concanavalin A (Con A), as demonstrated by turbidimetric experiments. Self-assembly of the same diblock copolymer compositions using an electroformation method yielded GGPs (ranging from 2-20 μm in diameter). Interaction of these cell-sized polymersomes with fimH positive E. coli was then studied via confocal microscopy. The glucose-decorated GGPs were found to cluster upon addition of the bacteria, while galactose-decorated GGPs could successfully interact with (and possibly immobilize) the bacteria without the onset of clustering. This demonstrates an opportunity to modulate the response of these synthetic cell mimics (protocells) toward biological entities through exploitation of selective ligand-receptor interactions, which may be readily tuned through a considered choice of carbohydrate functionality.

3D cryogel composites as adsorbent for isolation of protein and small molecules

A green and promising sample pretreatment method was successfully established, which efficiently isolated proteins and small molecules in human serum. This method was achieved based on the multifunctional polymer, cryogel, as a solid phase extraction (SPE) monolith easily equipped in a syringe. The cryogel (pDC/GO-DE) was composed of diallyldimethyl ammonium chloride (DC) and 2-hydroxyethyl methacrylate (HE), which was further modified with graphene oxide (GO) and N-diethylethanamine hydrobromide (DE). Various proteins, including bovine serum albumin (BSA), lysozyme (Lys), γ-globulins, immunoglobulin G (IgG), transferrin, small molecules (ribavirin, adenosine, ofloxacin, estriol, rutin, amoxicillin, ibuprofen, 1-methyl-3-phenyl-propylamine, and benzylamine) and their mixtures were successively studied as model analytes to evaluate the new material and demonstrate the isolation mechanism, which was mainly dependent on mixed-mode ion-exchange and the hybrid hydrophobicity-hydrophilicity property of pDC/GO-DE cryogel. Moreover, the three-dimensional macroporous structure contributed to the underlying size-selective isolation. When 10 times diluted human serum was used as the sample, more than 95% of proteins were adsorbed within 10 min under physiological conditions, and the interference matrix in serum was also efficiently reduced. After recycling three times, the extraction ratio of proteins in human serum was still higher than 90%. When four small molecules (camptothecin, ribavirin, 1-methyl-3-phenylpropylamine and ofloxacin) were added to blank human serum, their recoveries were within 65.6-81.8%, and were comparable to those obtained by protein precipitation method (63.7-83.2%).

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.

Monomer design strategies to create natural product-based polymer materials

In an effort towards enhancing function and sustainability, natural products have become of interest in the field of polymer chemistry.