Highly Branched Gradient Glycopolymer: Enzyme-Assisted Synthesis and Enhanced Bacteria-Binding Ability

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.

Adenosine Triphosphate-Responsive Glyconanorods through Self-Assembly of β-Cyclodextrin-Based Glycoconjugates for Targeted and Effective Bacterial Sensing and Killing

Polymer-based nanomaterials have exhibited promising alternative avenues to combat the globe challenge of multidrug-resistant bacterial infection. However, most of the reported polymeric nanomaterials have facially linear amphiphilic structures with positive net charges, which may lead to nonspecific binding, high hemolysis, and uncontrollable self-organization, limiting their practical applications. In this contribution, we report a one-dimensional glyconanorod (GNR) through self-assembly of well-defined β-cyclodextrin-based glycoconjugates (RMan) featuring hydrophobic carbon-based chains and amide rhodamines with an adenosine triphosphate (ATP)-recognition site and targeted and hydrophilic mannoses and positively net-charged ethylene amine groups. The GNRs show superior targeting sensing and killing for Gram-negative Escherichia coli (E. coli) dominantly through the multivalent recognition between mannoses on the nanorod and the lectin on the surface of E. coli. Moreover, red fluorescence was light on due to the hydrogen bonding between amide rhodamine and ATP. Benefiting from the designs, the GNRs are capable of possessing a higher therapeutic index and of encapsulating other antibiotics. They exhibit an enhanced effect against E. coli strains. Intriguingly, the GNRs displayed a more reduced hemolysis effect and lower cytotoxicity compared to that of ethylene glyco-modified nanorods. These results reveal that the glyconanomaterials not only feature superior and targeted bacterial sensing and antibacterial activity, but also better biocompatibility compared with the widely used PEG-covered nanomaterials. Furthermore, the in vivo studies demonstrate that the targeted and ATP-responsive GNRs complexed with antibiotics showed better treatment using a mouse model of abdominal sepsis following intraperitoneal E. coli infection. The present work describes a targeted and effective sensing and antibacterial platform based on glycoconjugates that have potential applications for the treatment of infections caused by pathogenic microorganisms.

Glycopolymers for Antibacterial and Antiviral Applications

Diseases induced by bacterial and viral infections are common occurrences in our daily life, and the main prevention and treatment strategies are vaccination and taking antibacterial/antiviral drugs. However, vaccines can only be used for specific viral infections, and the abuse of antibacterial/antiviral drugs will create multi-drug-resistant bacteria and viruses. Therefore, it is necessary to develop more targeted prevention and treatment methods against bacteria and viruses. Proteins on the surface of bacteria and viruses can specifically bind to sugar, so glycopolymers can be used as potential antibacterial and antiviral drugs. In this review, the research of glycopolymers for bacterial/viral detection/inhibition and antibacterial/antiviral applications in recent years are summarized.

Synthesis of Homo- and Heteromultivalent Fucosylated and Sialylated Oligosaccharide Conjugates via Preactivated N-Methyloxyamine Precision Macromolecules and Their Binding to Polyomavirus Capsid Proteins

Glycoconjugates are a versatile class of bioactive molecules that have found application as vaccines and antivirals and in cancer therapy. Their synthesis typically involves elaborate functionalization and use of protecting groups on the carbohydrate component in order to ensure efficient and selective conjugation. Alternatively, non-functionalized, non-protected carbohydrates isolated from biological sources or derived through biotechnological methods can be directly conjugated via N-methyloxyamine groups. In this study, we introduce such N-methyloxyamine groups into a variety of multivalent scaffolds─from small to oligomeric to polymeric scaffolds─making use of solid-phase polymer synthesis to assemble monodisperse sequence-defined macromolecules. These scaffolds are then successfully functionalized with different types of human milk oligosaccharides deriving a library of homo- and heteromultivalent glycoconjugates. Glycomacromolecules presenting oligosaccharide side chains with either α2,3- or α2,6-linked terminal sialic acid are used in a binding study with two types of polyomavirus capsid proteins showing that the multivalent presentation through the N-methyloxyamine-derived scaffolds increases the number of contacts with the protein. Overall, a straightforward route to derive glycoconjugates from complex oligosaccharides with high variability yet control in the multivalent scaffold is presented, and applicability of the derived structures is demonstrated.

Upper Critical Solution Temperature Polyvalent Scaffolds Aggregate and Exterminate Bacteria

Specific recognition and strong affinities of bacteria receptors with the host cell glycoconjugates pave the way to control the bacteria aggregation and kill bacteria. Herein, using aggregation-induced emission (AIE) molecules decorated upper critical solution temperature (UCST) polyvalent scaffold (PATC-GlcN), an approach toward visualizing bacteria aggregation and controlling bacteria-polyvalent scaffolds affinities under temperature stimulus is described. Polyvalent scaffolds with diblocks, one UCST block PATC of polyacrylamides showing a sharp UCST transition and typical AIE behavior, the second bacteria recognition block GlcN of hydrophilic glucosamine modified polyacrylamide, are prepared through a reversible addition and fragmentation chain transfer polymerization. Aggregated chain conformation of polyvalent scaffolds at temperature below UCST induces the aggregation of E. coli ATCC8739, because of the high density of glucosamine moieties, whereas beyond UCST, the hydrophilic state of the scaffolds dissociates the bacteria aggregation. The sweet-talking of bacteria toward the polyvalent scaffolds can be visualized by the fluorescent imaging technique, simultaneously. Due to the specific recognition of polyvalent scaffolds with bacteria, the photothermal agent IR780 loaded PATC-GlcN shows the targeted killing ability toward E. coli ATCC8739 in vitro and in vivo under NIR radiation.

From poly(vinylimidazole) to cationic glycopolymers and glyco-particles: effective antibacterial agents with enhanced biocompatibility and selectivity

Cationic glycopolymers have attracted great attention as a new type of antibacterial material.

Multivalent glycans for biological and biomedical applications

Recognition of glycans by proteins plays a crucial role in a variety of physiological processes in cells and living organisms. In addition, interactions of glycans with proteins are involved in the development of diverse diseases, such as pathogen infection, inflammation and tumor metastasis. It is well-known that multivalent glycans bind to proteins much more strongly than do their monomeric counterparts. Owing to this property, numerous multivalent glycans have been utilized to elucidate glycan-mediated biological processes and to discover glycan-based biomedical agents. In this review, we discuss recent advances (2014-2020) made in the development and biological and biomedical applications of synthetic multivalent glycans, including neoglycopeptides, neoglycoproteins, glycodendrimers, glycopolymers, glyconanoparticles and glycoliposomes. We hope this review assists researchers in the design and development of novel multivalent glycans with predictable activities.