Heparin: An old drug for new clinical applications

Quality control, safety assessment and preparation approaches of low molecular weight heparin

Low Molecular Weight Heparins (LMWHs) are well-established for use in the prevention and treatment of thrombotic diseases, and as a substitute for unfractionated heparin (UFH) due to their predictable pharmacokinetics and subcutaneous bioavailability. LMWHs are produced by various depolymerization methods from UFH, resulting in heterogeneous compounds with similar biochemical and pharmacological properties. However, the delicate supply chain of UFH and potential contamination from animal sources require new manufacturing approaches for LMWHs. Various LMWH preparation methods are emerging, such as chemical synthesis, enzymatic or chemical depolymerization and chemoenzymatic synthesis. To establish the sameness of active ingredients in both innovator and generic LMWH products, the Food and Drug Administration has implemented a stringent scientific method of equivalence based on physicochemical properties, heparin source material and depolymerization techniques, disaccharide composition and oligosaccharide mapping, biological and biochemical properties, and in vivo pharmacodynamic profiles. In this review, we discuss currently available LMWHs, potential manufacturing methods, and recent progress for manufacturing quality control of these LMWHs.

Low molecular weight heparin promotes the PPAR pathway by protecting the glycocalyx of cells to delay the progression of diabetic nephropathy

Diabetic nephropathy (DN) is one of the most important comorbidities for diabetic patients, which is the main factor leading to end-stage renal disease. Heparin analogues can delay the progression of DN, but the mechanism is not fully understood. In this study, we found that low molecular weight heparin (LMWH) therapy significantly upregulated some downstream proteins of the peroxisome proliferator-activated receptor (PPAR) signaling pathway by label-free quantification of the mouse kidney proteome. Through cell model verification, LMWH can protect the heparan sulfate (HS) of renal tubular epithelial cells from being degraded by heparanase that is highly expressed in a high-glucose environment, enhance the endocytic recruitment of fatty acid-binding protein 1 (FABP1), a coactivator of the PPAR pathway, and then regulate the activation level of intracellular PPAR. In addition, we have elucidated for the first time the molecular mechanism of HS and FABP1 interaction. These findings provide new insights into understanding the role of heparin in the pathogenesis of DN and developing corresponding treatments.

Material-specific binding peptides empower sustainable innovations in plant health, biocatalysis, medicine and microplastic quantification

Material-binding peptides (MBPs) have emerged as a diverse and innovation-enabling class of peptides in applications such as plant-/human health, immobilization of catalysts, bioactive coatings, accelerated polymer degradation and analytics for micro-/nanoplastics quantification. Progress has been fuelled by recent advancements in protein engineering methodologies and advances in computational and analytical methodologies, which allow the design of, for instance, material-specific MBPs with fine-tuned binding strength for numerous demands in material science applications. A genetic or chemical conjugation of second (biological, chemical or physical property-changing) functionality to MBPs empowers the design of advanced (hybrid) materials, bioactive coatings and analytical tools. In this review, we provide a comprehensive overview comprising naturally occurring MBPs and their function in nature, binding properties of short man-made MBPs (<20 amino acids) mainly obtained from phage-display libraries, and medium-sized binding peptides (20-100 amino acids) that have been reported to bind to metals, polymers or other industrially produced materials. The goal of this review is to provide an in-depth understanding of molecular interactions between materials and material-specific binding peptides, and thereby empower the use of MBPs in material science applications. Protein engineering methodologies and selected examples to tailor MBPs toward applications in agriculture with a focus on plant health, biocatalysis, medicine and environmental monitoring serve as examples of the transformative power of MBPs for various industrial applications. An emphasis will be given to MBPs' role in detecting and quantifying microplastics in high throughput, distinguishing microplastics from other environmental particles, and thereby assisting to close an analytical gap in food safety and monitoring of environmental plastic pollution. In essence, this review aims to provide an overview among researchers from diverse disciplines in respect to material-(specific) binding of MBPs, protein engineering methodologies to tailor their properties to application demands, re-engineering for material science applications using MBPs, and thereby inspire researchers to employ MBPs in their research.

Ion-Exchange Resin/Carrageenan-Copper-Based Nanocomposite: Artificial Neural Network, Advanced Thermodynamic Profiling, and Anticoagulant Studies

Carrageenan (CG) and ion exchange resins (IERs) are better metal chelators. Kappa (κ) CG and IERs were synthesized and subjected to copper ion (Cu2+) adsorption to obtain DMSCH/κ-Cu, DC20H/κ-Cu, and IRP69H/κ-Cu nanocomposites (NCs). The NCs were studied using statistical physics formalism (SPF) at 315-375 K and a multilayer perceptron with five input nodes. The percentage of Cu2+ uptake efficiency was used as an outcome variable. Via the grand canonical ensemble, SPF gives models for both monolayer and multilayer sorption layers. For in vitro anticoagulant activity (ACA), the activated partial thromboplastin time were calculated using 100 μL of rabbit plasma incubated at 37 °C. After 2 min, 100 L of 0.025 M CaCl2 was added, and the clotting time was recorded for each group (n = 6). The results demonstrated that the key covariables for the adsorption process were pH and concentration. The results of artificial neural network models were comparable with the experimental findings. The error rates varied between 4.3 and 1.0%. The prediction analysis results ranged from 43.6 to 89.2. The ΔG and ΔS values for IRP69H/κ-Cu obtained were -18.91 and -16.32 and 26.21 and 22.74 kJ/mol for the temperatures 315 and 345 K, respectively. Adsorbate species were perpendicular to the adsorbent surfaces, notwithstanding the apparent importance of macro- and micropore volumes. These adsorbents typically fluctuate with temperature changes and contain one or more layers of sorption. Negative and positive sorption energies correspond to endothermic and exothermic processes. The biosorption energy (E1 and E2) values in this experiment have a value of less than 23 kJ mol-1. Complex SPF models' energy distributions validate surface properties and interactions with adsorbates. At a concentration of 100 μg/mL, DC20H/κ-Cu2+ exhibited an ACA of only 8 s. These NCs demonstrated better greater ACA with the order DC20H/κ < DMSCH/κ < IRP69H/κ. More research is needed to rule out the chemical processes behind the ACA of CG/IER-Cu NCs.

Inhibition of catechol-O-methyltransferase (COMT) by heparin oligosaccharides with specific structures

COMT inhibitors are commonly used to improve the effectiveness of levodopa in treating Parkinson's disease by inhibiting its conversion to 3-O-methyldopa. Because of the serious side effect of nitrocatechol COMT inhibitors, it is necessary to develop non-nitrocatechol COMT inhibitors with a higher safety profile. Heparin has been observed to bind to COMT. However, the exact functional significance of this interaction is not fully understood. In this study, the contribution of different substitution of heparin to its binding with COMT was investigated. In vitro and in vivo, heparin oligosaccharides can bind to COMT and inhibit its activity. Furthermore, we enriched the functional heparin oligosaccharides that bind to COMT and identified the sequence UA2S-GlcN(S/Ac)6(S/H)-UA2S-GlcNS6(S/H)-UA2(S/H)-GlcNS6S as the characteristic structural domain of these functional oligosaccharides. This study has elucidated the relationship between the structure of heparin oligosaccharides and their activity against COMT, providing valuable insights for the development of non-nitrocatechol COMT inhibitors with improved safety and efficacy.

Heparin-Modified Superparamagnetic Iron Oxide Nanoparticles Suppress Lithium Chloride/Pilocarpine-Induced Temporal Lobe Epilepsy in Rats through Attenuation of Inflammation and Oxidative Stress

The development of antiepileptic drugs is still a long process. In this study, heparin-modified superparamagnetic iron oxide nanoparticles (UFH-SPIONs) were prepared, and their antiepileptic effect and underlying mechanism were investigated. UFH-SPIONs are stable, homogeneous nanosystems with antioxidant enzyme activity that are able to cross the blood-brain barrier (BBB) and enriched in hippocampal epileptogenic foci. The pretreatment with UFH-SPIONs effectively prolonged the onset of seizures and reduced seizure severity after lithium/pilocarpine (LP)-induced seizures in rats. The pretreatment with UFH-SPIONs significantly decreased the expression of inflammatory factors in hippocampal tissues, including IL-6, IL-1β, and TNF-α. LP-induced oxidative stress in hippocampal tissues was in turn reduced upon pretreatment with UFH-SPIONs, as evidenced by an increase in the levels of the antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) and a decrease in the level of lipid peroxidation (MDA). Moreover, the LP-induced upregulation of apoptotic cells was decreased upon pretreatment with UFH-SPIONs. Together, these observations suggest that the pretreatment with UFH-SPIONs ameliorates LP-induced seizures and downregulates the inflammatory response and oxidative stress, which exerts neuronal protection during epilepsy.

Synthesis and Detection of BODIPY-, Biotin-, and 19 F- Labeled Single-Entity Dendritic Heparan Sulfate Mimetics

Heparin and heparan sulfate (HS) are naturally occurring mammalian glycosaminoglycans, and their synthetic and semi-synthetic mimetics have attracted significant interest as potential therapeutics. However, understanding the mechanism of action by which HS, heparin, and HS mimetics have a biological effect is difficult due to their highly charged nature, broad protein interactomes, and variable structures. To address this, a library of novel single-entity dendritic mimetics conjugated to BODIPY, Fluorine-19 (19 F), and biotin was synthesized for imaging and localization studies. The novel dendritic scaffold allowed for the conjugation of labeling moieties without reducing the number of sulfated capping groups, thereby better mimicking the multivalent nature of HS-protein interactions. The 19 F labeled mimetics were assessed in phantom studies and were detected at concentrations as low as 5 mM. Flow cytometric studies using a fluorescently labeled mimetic showed that the compound associated with immune cells from tumors more readily than splenic counterparts and was directed to endosomal-lysosomal compartments within immune cells and cancer cells. Furthermore, the fluorescently labeled mimetic entered the central nervous system and was detectable in brain-infiltrating immune cells 24 hours after treatment. Here, we report the enabling methodology for rapidly preparing various labeled HS mimetics and molecular probes with diverse potential therapeutic applications.

Sweet but Challenging: Tackling the Complexity of GAGs with Engineered Tailor-Made Biomaterials

Glycosaminoglycans (GAGs) play a crucial role in tissue homeostasis by regulating the activity and diffusion of bioactive molecules. Incorporating GAGs into biomaterials has emerged as a widely adopted strategy in medical applications, owing to their biocompatibility and ability to control the release of bioactive molecules. Nevertheless, immobilized GAGs on biomaterials can elicit distinct cellular responses compared to their soluble forms, underscoring the need to understand the interactions between GAG and bioactive molecules within engineered functional biomaterials. By controlling critical parameters such as GAG type, density, and sulfation, it becomes possible to precisely delineate GAG functions within a biomaterial context and to better mimic specific tissue properties, enabling tailored design of GAG-based biomaterials for specific medical applications. However, this requires access to pure and well-characterized GAG compounds, which remains challenging. This review focuses on different strategies for producing well-defined GAGs and explores high-throughput approaches employed to investigate GAG-growth factor interactions and to quantify cellular responses on GAG-based biomaterials. These automated methods hold considerable promise for improving the understanding of the diverse functions of GAGs. In perspective, the scientific community is encouraged to adopt a rational approach in designing GAG-based biomaterials, taking into account the in vivo properties of the targeted tissue for medical applications.

Rapid environmentally benign label free detection of heparin using highly fluorescent N,S-CDs sensing probe through a turn-on mechanism

Heparin (HEP) is one of the oldest anticoagulant drugs that currently still in widespread clinical use. It lacks chromophore and not easily derivatized due to its hydrophilic nature. In this work we developed a green, selective, and sensitive fluorescence sensor for detection of HEP in its injection dosage forms. The sensor is composed of nitrogen and sulfur co-doped carbon quantum dots (N,S-CDs) semi quenched by Fe3+. The N,S-CDs were prepared using microwave assisted pyrolysis in 3.5 min and exhibited high emission at 425 nm after excitation at 350 nm with high quantum yield of 96%. Owing to the anionic nature of HEP, it could compete with N,S-CDs for Fe3+ complexation resulting in turning-on the quenched fluorescence. This fluorescence enhancement was linear over a concentration range between 6 and 20 μg/mL (R2 = 0.99) with a limit of detection of 1.41 µg/ml. The accuracy and precision of the proposed sensor were indicated by percentage recovery values between 98% -102% and %RSD less than 2, respectively. Furthermore, the proposed sensor was successfully applied for determination of HEP in injection dosage form. The developed sensor showed excellent greenness on analytical eco-scale (score 93%) and GAPI scale.

Impact of early heparin therapy on mortality in critically ill patients with sepsis associated acute kidney injury: a retrospective study from the MIMIC-IV database

Background: Inflammatory-coagulation dysfunction plays an increasingly important role in sepsis associated acute kidney injury (SAKI). This study aimed to investigate whether early heparin therapy improves survival in patients with SAKI. Methods: Patients with SAKI were identified from the Medical Information Mart for Intensive Care-IV database. The patients were divided into two groups: those who received heparin subcutaneously within 48 h after intensive care unit (ICU) admission and the control group, who received no heparin. The primary endpoint was ICU mortality, the secondary outcomes were 7-day, 14-day, 28-day, and hospital mortality. Propensity score matching (PSM), marginal structural Cox model (MSCM), and E-value analyses were performed. Results: The study included 5623 individuals with SAKI, 2410 of whom received heparin and 3213 of whom did not. There were significant effects on ICU and 28-day mortality in the overall population with PSM. MSCM further reinforces the efficacy of heparin administration reduces ICU mortality in the general population. Stratification analysis with MSCM showed that heparin administration was associated with decreased ICU mortality at various AKI stages. Heparin use was also associated with reduced 28-day mortality in patients with only female, age >60 years, and AKI stage 3, with HRs of 0.79, 0.77, and 0.60, respectively (p < 0.05). E-value analysis suggests robustness to unmeasured confounding. Conclusion: Early heparin therapy for patients with SAKI decreased ICU mortality. Further analysis demonstrated that heparin therapy was associated with reduced 28-day mortality rate in patients only among female, age > 60 years and AKI stage 3.

Block Synthesis and Step-Growth Polymerization of C-6-Sulfonatomethyl-Containing Sulfated Malto-Oligosaccharides and Their Biological Profiling

Highly sulfated malto-oligomers, similar to heparin and heparan-sulfate, have good antiviral, antimetastatic, anti-inflammatory and cell growth inhibitory effects. Due to their broad biological activities and simple structure, sulfated malto-oligomer derivatives have a great therapeutic potential, therefore, the development of efficient synthesis methods for their production is of utmost importance. In this work, preparation of α-(1→4)-linked oligoglucosides containing a sulfonatomethyl moiety at position C-6 of each glucose unit was studied by different approaches. Malto-oligomeric sulfonic acid derivatives up to dodecasaccharides were prepared by polymerization using different protecting groups, and the composition of the product mixtures was analyzed by MALDI-MS methods and size-exclusion chromatography. Synthesis of lower oligomers was also accomplished by stepwise and block synthetic methods, and then the oligosaccharide products were persulfated. The antiviral, anti-inflammatory and cell growth inhibitory activity of the fully sulfated malto-oligosaccharide sulfonic acids were determined by in vitro tests. Four tested di- and trisaccharide sulfonic acids effectively inhibited the activation of the TNF-α-mediated inflammatory pathway without showing cytotoxicity.

Polysaccharide-based hydrogels for medical devices, implants and tissue engineering: A review

Hydrogels are highly biocompatible biomaterials composed of crosslinked three-dimensional networks of hydrophilic polymers. Owing to their natural origin, polysaccharide-based hydrogels (PBHs) possess low toxicity, high biocompatibility and demonstrate in vivo biodegradability, making them great candidates for use in various biomedical devices, implants, and tissue engineering. In addition, many polysaccharides also show additional biological activities such as antimicrobial, anticoagulant, antioxidant, immunomodulatory, hemostatic, and anti-inflammatory, which can provide additional therapeutic benefits. The porous nature of PBHs allows for the immobilization of antibodies, aptamers, enzymes and other molecules on their surface, or within their matrix, potentiating their use in biosensor devices. Specific polysaccharides can be used to produce transparent hydrogels, which have been used widely to fabricate ocular implants. The ability of PBHs to encapsulate drugs and other actives has been utilized for making neural implants and coatings for cardiovascular devices (stents, pacemakers and venous catheters) and urinary catheters. Their high water-absorption capacity has been exploited to make superabsorbent diapers and sanitary napkins. The barrier property and mechanical strength of PBHs has been used to develop gels and films as anti-adhesive formulations for the prevention of post-operative adhesion. Finally, by virtue of their ability to mimic various body tissues, they have been explored as scaffolds and bio-inks for tissue engineering of a wide variety of organs. These applications have been described in detail, in this review.

Polysaccharide-based tumor microenvironment-responsive drug delivery systems for cancer therapy

The biochemical indicators of tumor microenvironment (TME) that are different from normal tissues provide the possibility for constructing intelligent drug delivery systems (DDSs). Polysaccharides with good biocompatibility, biodegradability, and unique biological properties are ideal materials for constructing DDSs. Nanogels, micelles, organic-inorganic nanocomposites, hydrogels, and microneedles (MNs) are common polysaccharide-based DDSs. Polysaccharide-based DDSs enable precise control of drug delivery and release processes by incorporating TME-specific biochemical indicators. The classification and design strategies of polysaccharide-based TME-responsive DDSs are comprehensively reviewed. The advantages and challenges of current polysaccharide-based DDSs are summarized and the future directions of development are foreseen. The polysaccharide-based TME-responsive DDSs are expected to provide new strategies and solutions for cancer therapy and make important contributions to the realization of precision medicine.

Non-Anticoagulant Activities of Low Molecular Weight Heparins-A Review

Low molecular weight heparins (LMWHs) are derived from heparin through chemical or enzymatic cleavage with an average molecular weight (Mw) of 2000-8000 Da. They exhibit more selective activities and advantages over heparin, causing fewer side effects, such as bleeding and heparin-induced thrombocytopenia. Due to different preparation methods, LMWHs have diverse structures and extensive biological activities. In this review, we describe the basic preparation methods in this field and compare the main principles and advantages of these specific methods in detail. Importantly, we focus on the non-anticoagulant pharmacological effects of LMWHs and their conjugates, such as preventing glycocalyx shedding, anti-inflammatory, antiviral infection, anti-fibrosis, inhibiting angiogenesis, inhibiting cell adhesion and improving endothelial function. LMWHs are effective in various diseases at the animal level, including cancer, some viral diseases, fibrotic diseases, and obstetric diseases. Finally, we briefly summarize their usage and potential applications in the clinic to promote the development and utilization of LMWHs.

Host Membranes as Drivers of Virus Evolution

The molecular mechanisms controlling the adaptation of viruses to host cells are generally poorly documented. An essential issue to resolve is whether host membranes, and especially lipid rafts, which are usually considered passive gateways for many enveloped viruses, also encode informational guidelines that could determine virus evolution. Due to their enrichment in gangliosides which confer an electronegative surface potential, lipid rafts impose a first control level favoring the selection of viruses with enhanced cationic areas, as illustrated by SARS-CoV-2 variants. Ganglioside clusters attract viral particles in a dynamic electrostatic funnel, the more cationic viruses of a viral population winning the race. However, electrostatic forces account for only a small part of the energy of raft-virus interaction, which depends mainly on the ability of viruses to form a network of hydrogen bonds with raft gangliosides. This fine tuning of virus-ganglioside interactions, which is essential to stabilize the virus on the host membrane, generates a second level of selection pressure driven by a typical induced-fit mechanism. Gangliosides play an active role in this process, wrapping around the virus spikes through a dynamic quicksand-like mechanism. Viruses are thus in an endless race for access to lipid rafts, and they are bound to evolve perpetually, combining speed (electrostatic potential) and precision (fine tuning of amino acids) under the selective pressure of the immune system. Deciphering the host membrane guidelines controlling virus evolution mechanisms may open new avenues for the design of innovative antivirals.

Doxorubicin covalently conjugated heparin displays anti-cancer activity as a self-assembled nanoparticle with a low-anticoagulant effect

Heparin is a glycosaminoglycans (GAGs) member and well-known FDA-approved anticoagulant that has been widely used in the clinic for 100 years. It has also been evaluated in various fields for further clinical applications, such as in anti-cancer or anti-inflammatory therapy beyond its anticoagulant effect. Here, we sought to utilize heparin molecules as drug carriers by directly conjugating the anticancer drug doxorubicin to the carboxyl group of unfractionated heparin. Given the molecular action of doxorubicin in intercalating DNA, it is expected to be less effective when structurally combined with other molecules. However, by utilizing doxorubicin molecules to produce reactive oxygen species (ROS), we found that the heparin-doxorubicin conjugates have significant cytotoxic ability to kill CT26 tumor cells with low anticoagulant activity. Several doxorubicin molecules were bound to heparin to provide sufficient cytotoxic capability and self-assembly ability due to their amphiphilic properties. The self-assembled formation of these nanoparticles was demonstrated through DLS, SEM and TEM. The cytotoxic ROS-generating doxorubicin-conjugated heparins could inhibit tumor growth and metastasis in CT26-bearing Balb/c animal models. Our results demonstrate that this cytotoxic doxorubicin-based heparin conjugate can significantly inhibit tumor growth and metastasis, thus showing promise as a potential new anti-cancer therapeutic.

Composite nanofibrous dressing loaded with Prussian blue and heparin for anti-inflammation therapy and diabetic wound healing

Diabetic ulcer is a severe complication of diabetes that can lead to amputation due to the overproduction of pro-inflammatory factors and reactive oxygen species (ROS). In this study, a composite nanofibrous dressing was developed by combining Prussian blue nanocrystals (PBNCs) and heparin sodium (Hep) through electrospinning, electrospraying, and chemical deposition. The nanofibrous dressing (PPBDH) was designed to take advantage of the excellent pro-inflammatory factor-adsorbing capability of Hep and the ROS-scavenging capabilities of PBNCs, resulting in synergistic treatment. It is worth noting that the nanozymes were firmly anchored to the fiber surfaces through slight polymer swelling caused by the solvent during electrospinning, thereby guaranteeing the preservation of the enzyme-like activity levels of PBNCs. The PPBDH dressing was found to be effective in reducing intracellular ROS levels, protecting cells from ROS-induced apoptosis, and capturing excessive pro-inflammatory factors, including chemoattractant protein-1 (MCP-1) and interleukin-1β (IL-1β). Furthermore, a chronic wound healing evaluation conducted in vivo demonstrated that the PPBDH dressing was able to effectively alleviate the inflammatory response and accelerate wound healing. This research presents an innovative approach to fabricate nanozyme hybrid nanofibrous dressings, which have great potential in accelerating the healing of chronic and refractory wounds with uncontrolled inflammation.

SPR Sensor-Based Analysis of the Inhibition of Marine Sulfated Glycans on Interactions between Monkeypox Virus Proteins and Glycosaminoglycans

Sulfated glycans from marine organisms are excellent sources of naturally occurring glycosaminoglycan (GAG) mimetics that demonstrate therapeutic activities, such as antiviral/microbial infection, anticoagulant, anticancer, and anti-inflammation activities. Many viruses use the heparan sulfate (HS) GAG on the surface of host cells as co-receptors for attachment and initiating cell entry. Therefore, virion-HS interactions have been targeted to develop broad-spectrum antiviral therapeutics. Here we report the potential anti-monkeypox virus (MPXV) activities of eight defined marine sulfated glycans, three fucosylated chondroitin sulfates, and three sulfated fucans extracted from the sea cucumber species Isostichopus badionotus, Holothuria floridana, and Pentacta pygmaea, and the sea urchin Lytechinus variegatus, as well as two chemically desulfated derivatives. The inhibitions of these marine sulfated glycans on MPXV A29 and A35 protein-heparin interactions were evaluated using surface plasmon resonance (SPR). These results demonstrated that the viral surface proteins of MPXV A29 and A35 bound to heparin, which is a highly sulfated HS, and sulfated glycans from sea cucumbers showed strong inhibition of MPXV A29 and A35 interactions. The study of molecular interactions between viral proteins and host cell GAGs is important in developing therapeutics for the prevention and treatment of MPXV.

Designing Smaller, Synthetic, Functional Mimetics of Sulfated Glycosaminoglycans as Allosteric Modulators of Coagulation Factors

Natural glycosaminoglycans (GAGs) are arguably the most diverse collection of natural products. Unfortunately, this bounty of structures remains untapped. Decades of research has realized only one GAG-like synthetic, small-molecule drug, fondaparinux. This represents an abysmal output because GAGs present a frontier that few medicinal chemists, and even fewer pharmaceutical companies, dare to undertake. GAGs are heterogeneous, polymeric, polydisperse, highly water soluble, synthetically challenging, too rapidly cleared, and difficult to analyze. Additionally, GAG binding to proteins is not very selective and GAG-binding sites are shallow. This Perspective attempts to transform this negative view into a much more promising one by highlighting recent advances in GAG mimetics. The Perspective focuses on the principles used in the design/discovery of drug-like, synthetic, sulfated small molecules as allosteric modulators of coagulation factors, such as antithrombin, thrombin, and factor XIa. These principles will also aid the design/discovery of sulfated agents against cancer, inflammation, and microbial infection.

Synthesis and Optimization of Collagen-targeting Peptide-Glycosaminoglycans for Inhibition of Platelets Following Endothelial Injury

Many endothelial complications, whether from surgical or pathological origins, can result in the denudation of the endothelial layer and the exposure of collagen. Exposure of collagen results in the activation of platelets, leading to thrombotic and inflammatory cascades that ultimately result in vessel stenosis. We have previously reported the use of peptide-GAG compounds to target exposed collagen following endothelial injury. In this paper we optimize the spacer sequence of our collagen binding peptide to increase its conjugation to GAG backbones and increase the peptide-GAG collagen binding affinity by increasing peptide C-terminal cationic charge. Furthermore, we demonstrate the use of these molecules to inhibit platelet activation through collagen blocking, as well as their localization to exposed vascular collagen following systemic delivery. Altogether, optimization of peptide sequence and linkage chemistry can allow for increased conjugation and function, having implications for glycoconjugate use in other clinical applications.

Heparin, Heparan Sulphate and Sepsis: Potential New Options for Treatment

Sepsis is a life-threatening hyperreaction to infection in which excessive inflammatory and immune responses cause damage to host tissues and organs. The glycosaminoglycan heparan sulphate (HS) is a major component of the cell surface glycocalyx. Cell surface HS modulates several of the mechanisms involved in sepsis such as pathogen interactions with the host cell and neutrophil recruitment and is a target for the pro-inflammatory enzyme heparanase. Heparin, a close structural relative of HS, is used in medicine as a powerful anticoagulant and antithrombotic. Many studies have shown that heparin can influence the course of sepsis-related processes as a result of its structural similarity to HS, including its strong negative charge. The anticoagulant activity of heparin, however, limits its potential in treatment of inflammatory conditions by introducing the risk of bleeding and other adverse side-effects. As the anticoagulant potency of heparin is largely determined by a single well-defined structural feature, it has been possible to develop heparin derivatives and mimetic compounds with reduced anticoagulant activity. Such heparin mimetics may have potential for use as therapeutic agents in the context of sepsis.

Biological Properties of Heparins Modified with an Arylazopyrazole-Based Photoswitch

Unfractionated heparin (UFH) and enoxaparin (Enox) were substituted with a photoswitch (PS) showing quantitative trans-cis and cis-trans photoisomerizations. Long half-life of the cis photoisomer enabled comparison of the properties of heparins substituted with both PS photoisomers. Hydrodynamic diameter, D_h, of UFH-PS decreased upon trans-cis photoisomerization, the change being more pronounced for UFH-PS with a higher degree of substitution (DS), while D_h of Enox-PS did not significantly change. The anticoagulative properties of substituted heparins were significantly attenuated compared to non-substituted compounds. The interaction of UFH-PS with HSA, lysozyme, and protamine was studied with ITC. Under serum-free conditions, UFH-PS-trans with a high DS stimulated proliferation of murine fibroblasts, while UFH-PS-cis decreased the viability of these cells. Under serum conditions, both UFH-PS-cis and UFH-PS-trans decreased cell viability, the reduction for UFH-PS-cis being higher than that for UFH-PS-trans. Neither Enox-PS-trans nor Enox-PS-cis influenced the viability at concentrations prolonging aPTT, while at higher concentrations their cytotoxicity did not differ.

Regional Citrate Anticoagulation or Heparin Anticoagulation for Renal Replacement Therapy in Patients With Liver Failure: A Systematic Review and Meta-Analysis

In patients with liver failure complicated by acute kidney injury, renal replacement therapy (RRT) is often required to improve the internal environment. The use of anticoagulants for RRT in patients with liver failure remains controversial. We searched the PubMed, Embase, Cochrane Library, and Web of Science databases for studies. The methodological quality of the included studies was assessed using the Methodological Index for Nonrandomized Studies. A meta-analysis was performed using R software (version 3.5.1) and Review Manager (version 5.3.5). During RRT, 348 patients from 9 studies received regional citrate anticoagulation (RCA), and 127 patients from 5 studies received heparin anticoagulation (including heparin and LMWH). Among patients who received RCA, the incidence of citrate accumulation, metabolic acidosis, and metabolic alkalosis were 5.3% (95% confidence interval [CI]: 0%-25.3%), 26.4% (95% CI: 0-76.9), and 1.8% (95% CI: 0-6.8), respectively. The potassium, phosphorus, total bilirubin (TBIL), and creatinine levels were lower, whereas the serum pH, bicarbonate, base excess levels, and total calcium/ionized calcium ratio were higher after treatment than before treatment. Among patients who received heparin anticoagulation, the TBIL levels were lower, whereas the activated partial thromboplastin clotting time and D-dimer levels were higher after treatment than before treatment. The mortality rates in the RCA and heparin anticoagulation groups were 58.9% (95% CI: 39.2-77.3) and 47.4% (95% CI: 31.1-63.7), respectively. No statistical difference in mortality was observed between the 2 groups. For patients with liver failure, the administration of RCA or heparin for anticoagulation during RRT under strict monitoring may be safe and effective.

Metal Binding to Sodium Heparin Monitored by Quadrupolar NMR

Heparins and heparan sulfate polysaccharides are negatively charged glycosaminoglycans and play important roles in cell-to-matrix and cell-to-cell signaling processes. Metal ion binding to heparins alters the conformation of heparins and influences their function. Various experimental techniques have been used to investigate metal ion-heparin interactions, frequently with inconsistent results. Exploiting the quadrupolar 23Na nucleus, we herein develop a 23Na NMR-based competition assay and monitor the binding of divalent Ca2+ and Mg2+ and trivalent Al3+ metal ions to sodium heparin and the consequent release of sodium ions from heparin. The 23Na spin relaxation rates and translational diffusion coefficients are utilized to quantify the metal ion-induced release of sodium ions from heparin. In the case of the Al3+ ion, the complementary approach of 27Al quadrupolar NMR is employed as a direct probe of ion binding to heparin. Our NMR results demonstrate at least two metal ion-binding sites with different affinities on heparin, potentially undergoing dynamic exchange. For the site with lower metal ion binding affinity, the order of Ca2+ > Mg2+ > Al3+ is obtained, in which even the weakly binding Al3+ ion is capable of displacing sodium ions from heparin. Overall, the multinuclear quadrupolar NMR approach employed here can monitor and quantify metal ion binding to heparin and capture different modes of metal ion-heparin binding.

Not Just Anticoagulation—New and Old Applications of Heparin

In recent decades, heparin, as the most important anticoagulant drug, has been widely used in clinical settings to prevent and treat thrombosis in a variety of diseases. However, with in-depth research, the therapeutic potential of heparin is being explored beyond anticoagulation. To date, heparin and its derivatives have been tested in the protection against and repair of inflammatory, antitumor, and cardiovascular diseases. It has also been explored as an antiangiogenic, preventive, and antiviral agent for atherosclerosis. This review focused on the new and old applications of heparin and discussed the potential mechanisms explaining the biological diversity of heparin.