N-Carboxyanhydride Polymerization of Glycopolypeptides That Activate Antigen-Presenting Cells through Dectin-1 and Dectin-2

Metal-Free Atom Transfer Radical Polymerization to Prepare Recylable Micro-Adjuvants for Dendritic Cell Vaccine

In the development of dendritic cell (DC) vaccines, the maturation of DCs is a critical stage. Adjuvants play a pivotal role in the maturation of DCs, with a major concern being to ensure both efficacy and safety. This study introduces an innovative approach that combines high efficacy with safety through the synthesis of micro-adjuvants grafted with copolymers of 2-(methacrylamido) glucopyranose (MAG) and methacryloxyethyl trimethyl ammonium chloride (DMC). The utilization of metal-free surface-initiated atom transfer radical polymerization enables the production of safe and recyclable adjuvants. These micrometer-sized adjuvants surpass the optimal size range for cellular endocytosis, enabling the retrieval and reuse of them during the ex vivo maturation process, mitigating potential toxicity concerns associated with the endocytosis of non-metabolized nanoparticles. Additionally, the adjuvants exhibit a "micro-ligand-mediated maturation enhancement" effect for DC maturation. This effect is influenced by the shape of the particle, as evidenced by the distinct promotion effects of rod-like and spherical micro-adjuvants with comparable sizes. Furthermore, the porous structure of the adjuvants enables them to function as cargo-carrying "micro-shuttles", releasing antigens upon binding to DCs to facilitate efficient antigen delivery.

Efficacy and safety of Panax notoginseng saponin injection in the treatment of acute myocardial infarction: a systematic review and meta-analysis of randomized controlled trials

Purpose: This study aimed to assess the efficacy and safety of Panax notoginseng saponin (PNS) injection, when combined with conventional treatment (CT), for acute myocardial infarction (AMI). Methods: Comprehensive searches were conducted in seven databases from inception until 28 September 2023. The search aimed to identify relevant randomized controlled trials (RCTs) focusing on PNS injection in the context of AMI. This meta-analysis adhered to the PRISMA 2020 guidelines, and its protocol was registered with PROSPERO (number: CRD42023480131). Result: Twenty RCTs involving 1,881 patients were included. The meta-analysis revealed that PNS injection, used adjunctively with CT, significantly improved treatment outcomes compared to CT alone, as evidenced by the following points: (1) enhanced total effective rate [OR = 3.09, p < 0.05]; (2) decreased incidence of major adverse cardiac events [OR = 0.32, p < 0.05]; (3) reduction in myocardial infarct size [MD = -6.53, p < 0.05]; (4) lower ST segment elevation amplitude [MD = -0.48, p < 0.05]; (5) mitigated myocardial injury as indicated by decreased levels of creatine kinase isoenzymes [MD = -11.19, p < 0.05], cardiac troponin T [MD = -3.01, p < 0.05], and cardiac troponin I [MD = -10.72, p < 0.05]; (6) enhanced cardiac function, reflected in improved brain natriuretic peptide [MD = -91.57, p < 0.05], left ventricular ejection fraction [MD = 5.91, p < 0.05], left ventricular end-diastolic dimension [MD = -3.08, p < 0.05], and cardiac output [MD = 0.53, p < 0.05]; (7) reduced inflammatory response, as shown by lower levels of C-reactive protein [MD = -2.99, p < 0.05], tumor necrosis factor-α [MD = -6.47, p < 0.05], interleukin-6 [MD = -24.46, p < 0.05], and pentraxin-3 [MD = -2.26, p < 0.05]; (8) improved vascular endothelial function, demonstrated by decreased endothelin-1 [MD = -20.56, p < 0.05] and increased nitric oxide [MD = 1.33, p < 0.05]; (9) alleviated oxidative stress, evidenced by increased superoxide dismutase levels [MD = 25.84, p < 0.05]; (10) no significant difference in adverse events [OR = 1.00, p = 1.00]. Conclusion: This study highlighted the efficacy and safety of adjunctive PNS injections in enhancing AMI patient outcomes beyond CT alone. Future RCTs need to solidify these findings through rigorous methods. Systematic Review Registration: (https://www.crd.york.ac.uk/PROSPERO/), identifier (CRD42023480131).

Facile Preparation of Carbohydrate-Containing Adjuvants Based on Self-Assembling Glycopeptide Conjugates

Carbohydrates are intriguing biomolecules possessing diverse biological activities, including immune stimulating capability. However, their biomedical applications have been limited by their complex and heterogeneous structures. In this study, we have utilized a self-assembling glycopeptide conjugate (GPC) system to produce uniform nanoribbons appending homogeneous oligosaccharides with multivalency. This system successfully translates the nontrivial structural differences of oligomannoses into varied binding affinities to C-type lectin receptors (CLRs). We have shown that GPCs could promote the CLR-mediated endocytosis of ovalbumin (OVA) antigen, and two mannotriose-modified peptides F3m2 and F3m5 exhibit potent activity in inducing antigen-presenting cell maturation, as indicated by increased CD86 and MHCII expression. In vivo studies demonstrated that GPCs, combined with OVA antigen, significantly enhanced OVA-specific antibody production. Specifically, F3m2 and F3m5 exhibited the highest immunostimulatory effects, eliciting both Th1- and Th2-biased immune responses and promoting differentiation of CD4+ and CD8+  T cells. These findings highlight the potential of GPCs as vaccine adjuvants, and showcase their versatility in exploiting the biological functions of carbohydrates.

Offsetting Low-Affinity Carbohydrate Binding with Covalency to Engage Sugar-Specific Proteins for Tumor-Immune Proximity Induction

Carbohydrate-binding receptors are often used by the innate immune system to potentiate inflammation, target endocytosis/destruction, and adaptive immunity (e.g., CD206, DC-SIGN, MBL, and anticarbohydrate antibodies). To access this class of receptors for cancer immunotherapy, a growing repertoire of bifunctional proximity-inducing therapeutics use high-avidity multivalent carbohydrate binding domains to offset the intrinsically low affinity associated with monomeric carbohydrate-protein binding interactions (Kd ≈ 10-3-10-6 M). For applications aimed at recruiting anticarbohydrate antibodies to tumor cells, large synthetic scaffolds are used that contain both a tumor-binding domain (TBD) and a multivalent antibody-binding domain (ABD) comprising multiple l-rhamnose monosaccharides. This allows for stable bridging between tumor cells and antibodies, which activates tumoricidal immune function. Problematically, such multivalent macromolecules can face limitations including synthetic and/or structural complexity and the potential for off-target immune engagement. We envisioned that small bifunctional "proximity-inducing" molecules containing a low-affinity monovalent ABD could efficiently engage carbohydrate-binding receptors for tumor-immune proximity by coupling weak binding with covalent engagement. Typical covalent drugs and electrophilic chimeras use high-affinity ligands to promote the fast covalent engagement of target proteins (i.e., large kinact/KI), driven by a favorably small KI for binding. We hypothesized the much less favorable KI associated with carbohydrate-protein binding interactions can be offset by a favorably large kinact for the covalent labeling step. In the current study, we test this hypothesis in the context of a model system that uses rhamnose-specific antibodies to induce tumor-immune proximity and tumoricidal function. We discovered that synthetic chimeric molecules capable of preorganizing an optimal electrophile (i.e., SuFEx vs activated ester) for protein engagement can rapidly covalently engage natural sources of antirhamnose antibody using only a single low-affinity rhamnose monosaccharide ABD. Strikingly, we observe chimeric molecules lacking an electrophile, which can only noncovalently bind the antibody, completely lack tumoricidal function. This is in stark contrast to previous work targeting small molecule hapten and peptide-specific antibodies. Our findings underscore the utility of covalency as a strategy to engage low-affinity carbohydrate-specific proteins for tumor-immune proximity induction.

Mirror Image Mucins and Thio Mucins with Tunable Biodegradation

Mucin glycoproteins are the major component of mucus and are integral to the cellular glycocalyx. Mucins play diverse roles in health and disease, are an important element in epithelial tissue models, and have broad therapeutic potential. All mucin applications are currently challenged by their inherent structural heterogeneity and degradation by proteases. In this study, we describe the synthesis and study of chemically defined mucin analogues bearing native glycans. We utilized combinations of enantiomer amino acids and glycan thioether linkages to achieve tunable proteolysis while maintaining cytocompatibility and binding activity. Structural characterization revealed a previously unknown mirror-image helix and sheds light on the molecular drivers of glycoprotein conformation. This work represents an important step toward the development of artificial mucins for biomedical applications.

Synthesis and evaluation of 1,5-dithialaminaribiose and -triose tetravalent constructs

We report the synthesis of novel tetravalent glucoclusters containing 1,5-dithia mimetics of laminaribiose and triose. The new constructs were evaluated for their ability to inhibit anti-CR3 fluorescent staining of human neutrophils, for which they showed moderate affinity. Evaluation of the synthesized glycoclusters for their ability to inhibit anti-Dectin-1 fluorescent staining of mouse macrophages revealed little to no affinity for Dectin-1.

Information transfer in mammalian glycan-based communication

Glycan-binding proteins, so-called lectins, are exposed on mammalian cell surfaces and decipher the information encoded within glycans translating it into biochemical signal transduction pathways in the cell. These glycan-lectin communication pathways are complex and difficult to analyze. However, quantitative data with single-cell resolution provide means to disentangle the associated signaling cascades. We chose C-type lectin receptors (CTLs) expressed on immune cells as a model system to study their capacity to transmit information encoded in glycans of incoming particles. In particular, we used nuclear factor kappa-B-reporter cell lines expressing DC-specific ICAM-3-grabbing nonintegrin (DC-SIGN), macrophage C-type lectin (MCL), dectin-1, dectin-2, and macrophage-inducible C-type lectin (MINCLE), as well as TNFαR and TLR-1&2 in monocytic cell lines and compared their transmission of glycan-encoded information. All receptors transmit information with similar signaling capacity, except dectin-2. This lectin was identified to be less efficient in information transmission compared to the other CTLs, and even when the sensitivity of the dectin-2 pathway was enhanced by overexpression of its co-receptor FcRγ, its transmitted information was not. Next, we expanded our investigation toward the integration of multiple signal transduction pathways including synergistic lectins, which is crucial during pathogen recognition. We show how the signaling capacity of lectin receptors using a similar signal transduction pathway (dectin-1 and dectin-2) is being integrated by compromising between the lectins. In contrast, co-expression of MCL synergistically enhanced the dectin-2 signaling capacity, particularly at low-glycan stimulant concentration. By using dectin-2 and other lectins as examples, we demonstrate how signaling capacity of dectin-2 is modulated in the presence of other lectins, and therefore, the findings provide insight into how immune cells translate glycan information using multivalent interactions.

Preparation and applications of artificial mucins in biomedicine

Mucus is an essential barrier material that separates organisms from the outside world. This slippery material regulates the transport of nutrients, drugs, gases, and pathogens toward the cell surface. The surface of the cell itself is coated in a mucus-like barrier of glycoproteins and glycolipids. Mucin glycoproteins are the primary component of mucus and the epithelial glycocalyx. Aberrant mucin production is implicated in diverse disease states from cancer and inflammation to pre-term birth and infection. Biological mucins are inherently heterogenous in structure, which has challenged understanding their molecular functions as a barrier and as biochemically active proteins. Therefore, many synthetic materials have been developed as artificial mucins with precisely tunable structures. This review highlights advances in design and synthesis of artificial mucins and their application in biomedical studies of mucin chemistry, biology, and physics.

Synthesis and biomedical applications of mucin mimic materials

Mucin glycoproteins are the major component of mucus and coat epithelial cell surfaces forming the glycocalyx. The glycocalyx and mucus are involved in the transport of nutrients, drugs, gases, and pathogens toward the cell surface. Mucins are also involved in diverse diseases such as cystic fibrosis and cancer. Due to inherent heterogeneity in native mucin structure, many synthetic materials have been designed to probe mucin chemistry, biology, and physics. Such materials include various glycopolymers, low molecular weight glycopeptides, glycopolypeptides, polysaccharides, and polysaccharide-protein conjugates. This review highlights advances in the area of design and synthesis of mucin mimic materials, and their biomedical applications in glycan binding, epithelial models of infection, therapeutic delivery, vaccine formulation, and beyond.

Principles of glycocalyx engineering with hydrophobic-anchored synthetic mucins

The cellular glycocalyx is involved in diverse biological phenomena in health and disease. Yet, molecular level studies have been challenged by a lack of tools to precisely manipulate this heterogeneous structure. Engineering of the cell surface using insertion of hydrophobic-terminal materials has emerged as a simple and efficient method with great promise for glycocalyx studies. However, there is a dearth of information about how the structure of the material affects membrane insertion efficiency and resulting density, the residence time of the material, or what types of cells can be utilized. Here, we examine a panel of synthetic mucin structures terminated in highly efficient cholesterylamide membrane anchors for their ability to engineer the glycocalyx of five different cell lines. We examined surface density, residence time and half-life, cytotoxicity, and the ability be passed to daughter cells. We report that this method is robust for a variety of polymeric structures, long-lasting, and well-tolerated by a variety of cell lines.

Chemical and Synthetic Biology Approaches for Cancer Vaccine Development

Cancer vaccines have been considered promising therapeutic strategies and are often constructed from whole cells, attenuated pathogens, carbohydrates, peptides, nucleic acids, etc. However, the use of whole organisms or pathogens can elicit unwanted immune responses arising from unforeseen reactions to the vaccine components. On the other hand, synthetic vaccines, which contain antigens that are conjugated, often with carrier proteins, can overcome these issues. Therefore, in this review we have highlighted the synthetic approaches and discussed several bioconjugation strategies for developing antigen-based cancer vaccines. In addition, the major synthetic biology approaches that were used to develop genetically modified cancer vaccines and their progress in clinical research are summarized here. Furthermore, to boost the immune responses of any vaccines, the addition of suitable adjuvants and a proper delivery system are essential. Hence, this review also mentions the synthesis of adjuvants and utilization of biomaterial scaffolds, which may facilitate the design of future cancer vaccines.

New opportunities for immunomodulation of the tumour microenvironment using chemical tools

Immunotherapy is recognised as an attractive method for the treatment of cancer, and numerous treatment strategies have emerged over recent years. Investigations of the tumour microenvironment (TME) have led to the identification of many potential therapeutic targets and methods. However, many recently applied immunotherapies are based on previously identified strategies, such as boosting the immune response by combining commonly used stimulators, and the release of drugs through changes in pH. Although methodological improvements such as structural optimisation and combining strategies can be undertaken, applying those novel targets and methods in immunotherapy remains an important goal. In this review, we summarise the latest research on the TME, and discuss how small molecules, immune cells, and their interactions with tumour cells can be regulated in the TME. Additionally, the techniques currently employed for delivery of these agents to the TME are also mentioned. Strategies to modulate cell phenotypes and interactions between immune cells and tumours are mainly discussed. We consider both modulatory and targeting methods aiming to bridge the gap between the TME and chemical modulation thereof.

Synthesis of bioactive (1→6)-β-glucose branched poly-amido-saccharides that stimulate and induce M1 polarization in macrophages

β-Glucans are of significant interest due to their potent antitumor and immunomodulatory activities. Nevertheless, the difficulty in purification, structural heterogenicity, and limited solubility impede the development of structure-property relationships and translation to therapeutic applications. Here, we report the synthesis of a new class of (1→6)-β-glucose-branched poly-amido-saccharides (PASs) as β-glucan mimetics by ring-opening polymerization of a gentiobiose-based disaccharide β-lactam and its copolymerization with a glucose-based β-lactam, followed by post-polymerization deprotection. The molecular weight (Mn) and frequency of branching (FB) of PASs is readily tuned by adjusting monomer-to-initiator ratio and mole fraction of gentiobiose-lactam in copolymerization. Branched PASs stimulate mouse macrophages, and enhance production of pro-inflammatory cytokines in a FB-, dose-, and Mn-dependent manner. The stimulation proceeds via the activation of NF-κB/AP-1 pathway in a Dectin-1-dependent manner, similar to natural β-glucans. The lead PAS significantly polarizes primary human macrophages towards M1 phenotype compared to other β-glucans such as lentinan, laminarin, and curdlan.

Immunostimulatory Polymers as Adjuvants, Immunotherapies, and Delivery Systems

Activating innate immunity in a controlled manner is necessary for the development of next-generation therapeutics. Adjuvants, or molecules that modulate the immune response, are critical components of vaccines and immunotherapies. While small molecules and biologics dominate the adjuvant market, emerging evidence supports the use of immunostimulatory polymers in therapeutics. Such polymers can stabilize and deliver cargo while stimulating the immune system by functioning as pattern recognition receptor (PRR) agonists. At the same time, in designing polymers that engage the immune system, it is important to consider any unintended initiation of an immune response that results in adverse immune-related events. Here, we highlight biologically derived and synthetic polymer scaffolds, as well as polymer–adjuvant systems and stimuli-responsive polymers loaded with adjuvants, that can invoke an immune response. We present synthetic considerations for the design of such immunostimulatory polymers, outline methods to target their delivery, and discuss their application in therapeutics. Finally, we conclude with our opinions on the design of next-generation immunostimulatory polymers, new applications of immunostimulatory polymers, and the development of improved preclinical immunocompatibility tests for new polymers.

Biomimetic Glycosylated Polythreonines by N-Carboxyanhydride Polymerization

Glycosylated threonine (Thr) is a structural motif found in seemingly disparate natural proteins from deep-sea collagen to mucins. Synthetic mimics of these important proteins are of great interest in biomedicine. Such materials also provide ready access to probe the contributions of individual amino acids to protein structure in a controlled and tunable manner. N-Carboxyanhydride (NCA) polymerization is one major route to such biomimetic polypeptides. However, challenges in the preparation and polymerization of Thr NCAs have impeded obtaining such structures. Here, we present optimized routes to several glycosylated and acetylated Thr NCAs of high analytical purity. Transition metal catalysis produced tunable homo-, statistical, and block-polypeptides with predictable chain lengths and low dispersities. We conducted structural work to examine their aqueous conformations and found that a high content of free OH Thr induces the formation of water-insoluble β-sheets. However, glycosylation appears to induce a polyproline II-type helical conformation, which sheds light on the role of glyco-Thr in rigid proteins such as mucins and collagen.

Hierarchy of Complex Glycomacromolecules: From Controlled Topologies to Biomedical Applications

Carbohydrates bearing a distinct complexity use a special code (Glycocode) to communicate with carbohydrate-binding proteins at a high precision to manipulate biological activities in complex biological environments. The level of complexity in carbohydrate-containing macromolecules controls the amount and specificity of information that can be stored in biomacromolecules. Therefore, a better understanding of the glycocode is crucial to open new areas of biomedical applications by controlling or manipulating the interaction between immune cells and pathogens in terms of trafficking and signaling, which would become a powerful tool to prevent infectious diseases. Even though a certain level of progress has been achieved over the past decade, synthetic glycomacromolecules are still lagging far behind naturally existing glycans in terms of complexity and precision because of insufficient and inefficient synthetic techniques. Currently, specific targeting at a cellular level using synthetic glycomacromolecules is still challenging. It is obvious that multidisciplinary collaborations are essential between different specialized disciplines to enhance the carbohydrate receptor-targeting paradigm for new biomedical applications. In this Perspective, recent developments in the synthesis of sophisticated glycomacromolecules are highlighted, and their biological and biomedical applications are also discussed in detail.

Dynamic Glycopeptide Dendrimers: Synthesis and Their Controllable Self-Assembly into Varied Glyco-Nanostructures for the Biomimicry of Glycans

A library of 14 dynamic glycopeptide amphiphilic dendrimers composed of 14 hydrophilic and bioactive saccharides (seven kinds) as dendrons and 7 hydrophobic peptides (di- and tetrapeptides) as arms with β-cyclodextrin (CD) as a core were facially designed and synthesized in several steps. Fourteen saccharides were first conjugated to the C-2 and C-3 positions of CD, forming glycodendrons. Subsequently, seven oligopeptide arms were introduced at the C-6 positions of a CD moiety by an acylhydrazone dynamic covalent bond, resulting in unique Janus amphiphilic glycopeptide dendrimers with precise and varied molecular structures. The kinds of hydrophilic parts of saccharides and hydrophobic parts of peptides were easily varied to prepare a series of amphiphilic Janus glycopeptide dendrimers. Intriguingly, these obtained amphiphilic glycopeptide dendrimers showcased very different self-assembly behaviors from the traditional amphiphilic linear block-copolymers and self-assembled into different glyco-nanostructures with controllable morphologies including glycospheres, worm-like micelles, and fibers depending upon the repeat unit ratio of saccharides and phenylalanine. Both glycodendrons and glycopeptide assemblies displayed strong and specific recognitions with C-type mannose-specific lectin. Moreover, these glycopeptide nanomaterials can encapsulate exemplary hydrophobic molecules such as Nile red (NR). The dye-loaded glycopeptide nanostructures showed a pH-controllable release behavior around the physiological and acidic tumor environment. Furthermore, cell experiments demonstrated that such glyco-nanostructures can further facilitate the functions of a model drug of the pyridone agent to reduce the expression of monocyte chemotactic protein-1 (MCP-1) and interleukin -1beta (IL-1β) in the primary peritoneal macrophages via encapsulating drugs. Considering all the abovementioned advantages including unique and precise structures, bioactivity, targeting, and controllable cargo release, we believe that these findings can not only enrich the library of glycopeptides but also provide a new avenue to the fabrication of smart and structure-controllable glyco-nanomaterials which hold great potential biological applications such as targeted delivery and release of therapeutic and bioactive molecules.

Tunable, biodegradable grafting-from glycopolypeptide bottlebrush polymers

The cellular glycocalyx and extracellular matrix are rich in glycoproteins and proteoglycans that play essential physical and biochemical roles in all life. Synthetic mimics of these natural bottlebrush polymers have wide applications in biomedicine, yet preparation has been challenged by their high grafting and glycosylation densities. Using one-pot dual-catalysis polymerization of glycan-bearing α-amino acid N-carboxyanhydrides, we report grafting-from glycopolypeptide brushes. The materials are chemically and conformationally tunable where backbone and sidechain lengths were precisely altered, grafting density modulated up to 100%, and glycan density and identity tuned by monomer feed ratios. The glycobrushes are composed entirely of sugars and amino acids, are non-toxic to cells, and are degradable by natural proteases. Inspired by native lipid-anchored proteoglycans, cholesterol-modified glycobrushes were displayed on the surface of live human cells. Our materials overcome long-standing challenges in glycobrush polymer synthesis and offer new opportunities to examine glycan presentation and multivalency from chemically defined scaffolds.

Synthetic mimics of glycoproteins and proteoglycans have wide applications in biomedicine, yet preparation has been challenged by their high grafting and glycosylation densities. Here the authors show one-pot dual-catalysis polymerization of glycan-bearing α-amino acid N-carboxyanhydrides to form glycopolypeptide brushes.

The Road to Structurally Defined β-Glucans

β-glucans are polymers of glucose that have been isolated from a variety of organisms. Isolated β-glucans have been used for medical purposes for centuries; however, efforts to define the biological activities of β-glucans experimentally were initiated in the 1940's. The diversity of structure associated with isolated β-glucans has impeded said investigations, and efforts to leverage the biological activity of β-glucans for clinical applications. In recognition of the need for defined β-glucans that retain the biological activity of isolated β-glucans, considerable investment has been made to facilitate the synthesis of structurally defined β-glucans. Here, we review the different approaches that have been applied to prepare β-glucans. In addition, we summarize the approaches that have been utilized to conjugate β-glucans to proteins.

Synthetic Glycomacromolecules of Defined Valency, Absolute Configuration, and Topology Distinguish between Human Lectins

Carbohydrate-binding proteins (lectins) play vital roles in cell recognition and signaling, including pathogen binding and innate immunity. Thus, targeting lectins, especially those on the surface of immune cells, could advance immunology and drug discovery. Lectins are typically oligomeric; therefore, many of the most potent ligands are multivalent. An effective strategy for lectin targeting is to display multiple copies of a single glycan epitope on a polymer backbone; however, a drawback to such multivalent ligands is they cannot distinguish between lectins that share monosaccharide binding selectivity (e.g., mannose-binding lectins) as they often lack molecular precision. Here, we describe the development of an iterative exponential growth (IEG) synthetic strategy that enables facile access to synthetic glycomacromolecules with precisely defined and tunable sizes up to 22.5 kDa, compositions, topologies, and absolute configurations. Twelve discrete mannosylated "glyco-IEGmers" are synthesized and screened for binding to a panel of mannoside-binding immune lectins (DC-SIGN, DC-SIGNR, MBL, SP-D, langerin, dectin-2, mincle, and DEC-205). In many cases, the glyco-IEGmers had distinct length, stereochemistry, and topology-dependent lectin-binding preferences. To understand these differences, we used molecular dynamics and density functional theory simulations of octameric glyco-IEGmers, which revealed dramatic effects of glyco-IEGmer stereochemistry and topology on solution structure and reveal an interplay between conformational diversity and chiral recognition in selective lectin binding. Ligand function also could be controlled by chemical substitution: by tuning the side chains of glyco-IEGmers that bind DC-SIGN, we could alter their cellular trafficking through alteration of their aggregation state. These results highlight the power of precision synthetic oligomer/polymer synthesis for selective biological targeting, motivating the development of next-generation glycomacromolecules tailored for specific immunological or other therapeutic applications.

Pattern recognition receptors in health and diseases

Pattern recognition receptors (PRRs) are a class of receptors that can directly recognize the specific molecular structures on the surface of pathogens, apoptotic host cells, and damaged senescent cells. PRRs bridge nonspecific immunity and specific immunity. Through the recognition and binding of ligands, PRRs can produce nonspecific anti-infection, antitumor, and other immunoprotective effects. Most PRRs in the innate immune system of vertebrates can be classified into the following five types based on protein domain homology: Toll-like receptors (TLRs), nucleotide oligomerization domain (NOD)-like receptors (NLRs), retinoic acid-inducible gene-I (RIG-I)-like receptors (RLRs), C-type lectin receptors (CLRs), and absent in melanoma-2 (AIM2)-like receptors (ALRs). PRRs are basically composed of ligand recognition domains, intermediate domains, and effector domains. PRRs recognize and bind their respective ligands and recruit adaptor molecules with the same structure through their effector domains, initiating downstream signaling pathways to exert effects. In recent years, the increased researches on the recognition and binding of PRRs and their ligands have greatly promoted the understanding of different PRRs signaling pathways and provided ideas for the treatment of immune-related diseases and even tumors. This review describes in detail the history, the structural characteristics, ligand recognition mechanism, the signaling pathway, the related disease, new drugs in clinical trials and clinical therapy of different types of PRRs, and discusses the significance of the research on pattern recognition mechanism for the treatment of PRR-related diseases.

Carbohydrate-Based Macromolecular Biomaterials

Carbohydrates are the most abundant and one of the most important biomacromolecules in Nature. Except for energy-related compounds, carbohydrates can be roughly divided into two categories: Carbohydrates as matter and carbohydrates as information. As matter, carbohydrates are abundantly present in the extracellular matrix of animals and cell walls of various plants, bacteria, fungi, etc., serving as scaffolds. Some commonly found polysaccharides are featured as biocompatible materials with controllable rigidity and functionality, forming polymeric biomaterials which are widely used in drug delivery, tissue engineering, etc. As information, carbohydrates are usually referred to the glycans from glycoproteins, glycolipids, and proteoglycans, which bind to proteins or other carbohydrates, thereby meditating the cell-cell and cell-matrix interactions. These glycans could be simplified as synthetic glycopolymers, glycolipids, and glycoproteins, which could be afforded through polymerization, multistep synthesis, or a semisynthetic strategy. The information role of carbohydrates can be demonstrated not only as targeting reagents but also as immune antigens and adjuvants. The latter are also included in this review as they are always in a macromolecular formulation. In this review, we intend to provide a relatively comprehensive summary of carbohydrate-based macromolecular biomaterials since 2010 while emphasizing the fundamental understanding to guide the rational design of biomaterials. Carbohydrate-based macromolecules on the basis of their resources and chemical structures will be discussed, including naturally occurring polysaccharides, naturally derived synthetic polysaccharides, glycopolymers/glycodendrimers, supramolecular glycopolymers, and synthetic glycolipids/glycoproteins. Multiscale structure-function relationships in several major application areas, including delivery systems, tissue engineering, and immunology, will be detailed. We hope this review will provide valuable information for the development of carbohydrate-based macromolecular biomaterials and build a bridge between the carbohydrates as matter and the carbohydrates as information to promote new biomaterial design in the near future.

Biological applications of water-soluble polypeptides with ordered secondary structures

Water-soluble polypeptides are a class of synthetic polymers with peptide bond frameworks imitating natural proteins and have broad prospects in biological applications. The regulation and dynamic transition of the secondary structures of water-soluble polypeptides have a great impact on their physio-chemical properties and biological functions. In this review article, we briefly introduce the current strategies to synthesize polypeptides and modulate their secondary structures. We then discuss the factors affecting the conformational stability/transition of polypeptides and the potential impact of side-chain functionalization on the ordered secondary structures, such as α-helix and β-sheet. We then summarize the biological applications of water-soluble polypeptides such as cell penetration, gene delivery, and antimicrobial treatment, highlighting the important roles of ordered secondary structures therein.

Synthesis and Biopharmaceutical Applications of Sugar-Based Polymers: New Advances and Future Prospects

The rapid rise in research interest in carbohydrate-based polymers is undoubtedly due to the nontoxic nature of such materials in an in vivo environment and the versatile roles that the polymers can play in cellular functions. Such polymers have served as therapeutic tools for drug delivery, including antigens, proteins, and genes, as well as diagnostic devices. Our focus in the first half of this Review is on synthetic methods based on ring-opening polymerization and enzyme-catalyzed polymerization, along with controlled radical polymerization. In the second half of this Review, sugar-based polymers are discussed on the basis of their remarkable success in competitive receptor binding, as multifunctional nanocarriers of targeting inhibitors for cancer treatment, in genome-editing delivery, in immunotherapy based on endogenous antibody recruitment, and in treatment of respiratory diseases, including influenza A. Particular emphasis is put on the synthesis and biopharmaceutical applications of sugar-based polymers published in the most recent 5 years. A noticeable attribute of carbohydrate-based polymers is that the sugar-receptor interactions can be facilitated by the cooperative effect of multiple sugar units. Their diversified topology and structures will drive the development of new synthetic strategies and bring about important applications, including coronavirus-related drug therapy.

Design, synthesis and biological applications of glycopolypeptides

Carbohydrates play essential structural and biochemical roles in all living organisms. Glycopolymers are attractive as well-defined biomimetic analogs to study carbohydrate-dependent processes, and are widely applicable biocompatible materials in their own right. Glycopolypeptides have shown great promise in this area since they are closer structural mimics of natural glycoproteins than other synthetic glycopolymers and can serve as carriers for biologically active carbohydrates. This review highlights advances in the area of design and synthesis of such materials, and their biomedical applications in therapeutic delivery, tissue engineering, and beyond.

Design and Synthesis of Mucin-Inspired Glycopolymers

Mucins are bottlebrush biopolymers that are glycoproteins on the surfaces of cells and as hydrogels secreted inside and outside the body. Mucin function in biology includes cell-cell recognition, signaling, protection, adhesion, and lubrication. Because of their attractive and diverse properties, mucins have recently become the focus of synthetic efforts by researchers who hope to understand and emulate these biomaterials. This review is focused on the development of methodologies for preparing mucin-inspired synthetic oligomers and glycopolymers, including solid-phase synthesis, polymerization of glycosylated monomers, and post-polymerization grafting of glycans to polymer chains. How these synthetic mucins have been used in health applications is discussed. Natural mucins are formed from a conserved set of monomers that are combined into chains of different sequences and lengths to achieve materials with widely diverse properties. Adopting this design paradigm from natural mucins could lead to next-generation bioinspired synthetic materials.

Chemical Strategies to Boost Cancer Vaccines

Personalized cancer vaccines (PCVs) are reinvigorating vaccine strategies in cancer immunotherapy. In contrast to adoptive T-cell therapy and checkpoint blockade, the PCV strategy modulates the innate and adaptive immune systems with broader activation to redeploy antitumor immunity with individualized tumor-specific antigens (neoantigens). Following a sequential scheme of tumor biopsy, mutation analysis, and epitope prediction, the administration of neoantigens with synthetic long peptide (SLP) or mRNA formulations dramatically improves the population and activity of antigen-specific CD4+ and CD8+ T cells. Despite the promising prospect of PCVs, there is still great potential for optimizing prevaccination procedures and vaccine potency. In particular, the arduous development of tumor-associated antigen (TAA)-based vaccines provides valuable experience and rational principles for augmenting vaccine potency which is expected to advance PCV through the design of adjuvants, delivery systems, and immunosuppressive tumor microenvironment (TME) reversion since current personalized vaccination simply admixes antigens with adjuvants. Considering the broader application of TAA-based vaccine design, these two strategies complement each other and can lead to both personalized and universal therapeutic methods. Chemical strategies provide vast opportunities for (1) exploring novel adjuvants, including synthetic molecules and materials with optimizable activity, (2) constructing efficient and precise delivery systems to avoid systemic diffusion, improve biosafety, target secondary lymphoid organs, and enhance antigen presentation, and (3) combining bioengineering methods to innovate improvements in conventional vaccination, "smartly" re-educate the TME, and modulate antitumor immunity. As chemical strategies have proven versatility, reliability, and universality in the design of T cell- and B cell-based antitumor vaccines, the union of such numerous chemical methods in vaccine construction is expected to provide new vigor and vitality in cancer treatment.

Self-Assembling Glycopeptide Conjugate as a Versatile Platform for Mimicking Complex Polysaccharides

Polysaccharides are a class of carbohydrates that play pivotal roles in living systems such as being chemical messengers in many vital biological pathways. However, the complexity and heterogeneity of these natural structures have posed daunting challenges on their production, characterization, evaluation, and applications. While there have been various types of synthetic skeletons that could mimic some biological aspects of polysaccharides, a safer and more easily accessed system is still desired to avoid the unnatural components and difficulties in modifying the structures. In this work, conveniently accessible self-assembling glycopeptide conjugates are developed, where the natural O-glycosidic linkages and phosphoryl modifications assist the self-assembly and concurrently reduce the risk of toxicity. The generated nanoparticles in aqueous solution offer a multivalent display of structurally controllable carbohydrates as mimics of polysaccharides, among which a mannosylated version exhibits immunostimulatory effects in both cellular assays and vaccination of mice. The obtained results demonstrate the potential of this glycopeptide conjugate-derived platform in exploiting the intriguing properties of carbohydrates in a more structurally maneuverable fashion.

Membrane-tethered mucin-like polypeptides sterically inhibit binding and slow fusion kinetics of influenza A virus

The mechanism(s) by which cell-tethered mucins modulate infection by influenza A viruses (IAVs) remain an open question. Mucins form both a protective barrier that can block virus binding and recruit IAVs to bind cells via the sialic acids of cell-tethered mucins. To elucidate the molecular role of mucins in flu pathogenesis, we constructed a synthetic glycocalyx to investigate membrane-tethered mucins in the context of IAV binding and fusion. We designed and synthesized lipid-tethered glycopolypeptide mimics of mucins and added them to lipid bilayers, allowing chemical control of length, glycosylation, and surface density of a model glycocalyx. We observed that the mucin mimics undergo a conformational change at high surface densities from a compact to an extended architecture. At high surface densities, asialo mucin mimics inhibited IAV binding to underlying glycolipid receptors, and this density correlated to the mucin mimic's conformational transition. Using a single virus fusion assay, we observed that while fusion of virions bound to vesicles coated with sialylated mucin mimics was possible, the kinetics of fusion was slowed in a mucin density-dependent manner. These data provide a molecular model for a protective mechanism by mucins in IAV infection, and therefore this synthetic glycocalyx provides a useful reductionist model for studying the complex interface of host-pathogen interactions.

Helical polymers for biological and medical applications

Helices are the most prevalent secondary structure in biomolecules and play vital roles in their activity. Chemists have been fascinated with mimicking this molecular conformation with synthetic materials. Research has now been devoted to the synthesis and characterization of helical materials, and to understand the design principles behind this molecular architecture. In parallel, work has been done to develop synthetic polymers for biological and medical applications. We now have access to materials with controlled size, molecular conformation, multivalency or functionality. As a result, synthetic polymers are being investigated in areas such as drug and gene delivery, tissue engineering, imaging and sensing, or as polymer therapeutics. Here, we provide a critical view of where these two fields, helical polymers and polymers for biological and medical applications, overlap. We have selected relevant polymer families and examples to illustrate the range of applications that can be targeted and the impact of the helical conformation on the performance. For each family of polymers, we briefly describe how they can be prepared, what helical conformations are observed and what parameters control helicity. We close this Review with an outlook of the challenges ahead, including the characterization of helicity through the process and the identification of biocompatibility.

Therapeutic potential of polypeptide-based conjugates: Rational design and analytical tools that can boost clinical translation

The clinical success of polypeptides as polymeric drugs, covered by the umbrella term "polymer therapeutics," combined with related scientific and technological breakthroughs, explain their exponential growth in the development of polypeptide-drug conjugates as therapeutic agents. A deeper understanding of the biology at relevant pathological sites and the critical biological barriers faced, combined with advances regarding controlled polymerization techniques, material bioresponsiveness, analytical methods, and scale up-manufacture processes, have fostered the development of these nature-mimicking entities. Now, engineered polypeptides have the potential to combat current challenges in the advanced drug delivery field. In this review, we will discuss examples of polypeptide-drug conjugates as single or combination therapies in both preclinical and clinical studies as therapeutics and molecular imaging tools. Importantly, we will critically discuss relevant examples to highlight those parameters relevant to their rational design, such as linking chemistry, the analytical strategies employed, and their physicochemical and biological characterization, that will foster their rapid clinical translation.

Synthesis of β-1,3-glucan mimics by β-1,3-glucan trisaccharyl monomer polymerization

β-1,3-Glucans are important as immunostimulating agents in living organisms. The multivalent binding of β-1,3-glucans to dectin-1, a cell surface receptor, activates immunological defenses. To study artificial immunostimulating agents, glycopolymers carrying β-1,3-glucan trisaccharides as artificial ligands were synthesized. The β-1,3-glucan trisaccharide, defined as an active unit of β-1,3-glucan, was constructed from D-glucose by glycosylation. A norbornene group was introduced as a polymerizable group into the trisaccharide derivative at the aglycone. The prepared endo/exo norbornene stereoisomers of the monomers were separated by silica gel chromatography and identified by NMR spectroscopy and mass spectrometry. The synthesized glycosyl monomers were polymerized and copolymerized with norbornene using 2^nd generation Hoveyda-Grubbs catalyst, deprotected, and purified by gel filtration to prepare water-soluble glycopolymers of varied compositions and high molecular weights. These polymers will have the potential for multivalent binding to dectin-1 to activate immune response and facilitate studies to understand the binding mechanisms of β-1,3-glucans with dectin-1.

Carbohydrate-based nanocarriers and their application to target macrophages and deliver antimicrobial agents

Many deadly infections are produced by microorganisms capable of sustained survival in macrophages. This reduces exposure to chemadrotherapy, prevents immune detection, and is akin to criminals hiding in police stations. Therefore, the use of glyco-nanoparticles (GNPs) as carriers of therapeutic agents is a burgeoning field. Such an approach can enhance the penetration of drugs into macrophages with specific carbohydrate targeting molecules on the nanocarrier to interact with macrophage lectins. Carbohydrates are natural biological molecules and the key constituents in a large variety of biological events such as cellular communication, infection, inflammation, enzyme trafficking, cellular migration, cancer metastasis and immune functions. The prominent characteristics of carbohydrates including biodegradability, biocompatibility, hydrophilicity and the highly specific interaction of targeting cell-surface receptors support their potential application to drug delivery systems (DDS). This review presents the 21^st century development of carbohydrate-based nanocarriers for drug targeting of therapeutic agents for diseases localized in macrophages. The significance of natural carbohydrate-derived nanoparticles (GNPs) as anti-microbial drug carriers is highlighted in several areas of treatment including tuberculosis, salmonellosis, leishmaniasis, candidiasis, and HIV/AIDS.

Aggregation-Induced Emission Luminogen Assisted Self-Assembly and Morphology Transition of Amphiphilic Glycopolypeptide with Bioimaging Application

Recently, fluorescent macromolecules with AIE effect have attracted considerable attentions due to their remarkable optical properties. In particular, designing novel tetraphenylethylene (TPE)-based bioconjugates to construct various self-assembled nanostructures and to expand the applications have aroused great interests. Herein, we report the self-assembly of TPE-based amphiphilic glycopolypeptide bioconjugate for bioimaging and tracing of live cells. The resultant amphiphilic fluorescent glycopolypeptide P1tM-TPE could self-assemble into different nanostructures, including vesicles, spindles and porous nanosheets, which mainly depends on the water fraction in DMSO/water mixture. At the same time, the vesicles can transform to spindles when increasing the water fractions. Both the vesicles and spindles are prone to be effectively internalized by macrophages, and all of them performed outstanding intracellular fluorescent retention properties. As far as we know, this is the first report on self-assembly and applications of glycopolypeptide-TPE bioconjugate, which will deepen our understanding on the self-assembly mechanism of TPE-based bioconjugates and provide a new way for fabricating functional fluorescent materials to monitor various biological processes.

Photoactivatable Fluorogenic Labeling via Turn-On "Click-Like" Nitroso-Diene Bioorthogonal Reaction

Fluorogenic labeling enables imaging cellular molecules of interest with minimal background. This process is accompanied with the notable increase of the quantum yield of fluorophore, thus minimizing the background signals from unactivated profluorophores. Herein, the development of a highly efficient and bioorthogonal nitroso-based Diels-Alder fluorogenic reaction is presented and its usefulness is validated as effective and controllable in fluorescent probes and live-cell labeling strategies for dynamic cellular imaging. It is demonstrated that nitroso-based cycloaddition is an efficient fluorogenic labeling tool through experiments of further UV-activatable fluorescent labeling on proteins and live cells. The ability of tuning the fluorescence of labeled proteins by UV-irradiation enables selective activation of proteins of interest in a particular cell compartment at a given time point, while leaving the remaining labeled molecules untouched.

Lithium hexamethyldisilazide initiated superfast ring opening polymerization of alpha-amino acid N-carboxyanhydrides

Polypeptides have broad applications and can be prepared via ring-opening polymerization of α-amino acid N-carboxyanhydrides (NCAs). Conventional initiators, such as primary amines, give slow NCA polymerization, which requires multiple days to reach completion and can result in substantial side reactions, especially for very reactive NCAs. Moreover, current NCA polymerizations are very sensitive to moisture and must typically be conducted in a glove box. Here we show that lithium hexamethyldisilazide (LiHMDS) initiates an extremely rapid NCA polymerization process that is completed within minutes or hours and can be conducted in an open vessel. Polypeptides with variable chain length (DP = 20–1294) and narrow molecular weight distribution (Mw/Mn = 1.08–1.28) were readily prepared with this approach. Mechanistic studies support an anionic ring opening polymerization mechanism. This living NCA polymerization method allowed rapid synthesis of polypeptide libraries for high-throughput functional screening.

Ring-opening polymerizations of α-amino acid N-carboxyanhydrides to form polypeptides are usually sensitive to moisture, slow and can undergo side reactions. Here the authors use lithium hexamethyldisilazide to initiate α-amino acid N-carboxyanhydride polymerizations that is very fast and can be conducted in an open vessel.