Heparin-protein interactions

Cationic Conjugated Polyelectrolytes with Aggregation-Induced Ratiometric Fluorescence

The molecular diversity of aggregation-induced emission remains to be challenging due to the limitation of conventional synthesis methods. Here, a series of novel neutral and cationic conjugated polymers composed with various ratios of tetraarylethylene (TAE) containing a bridged oxygen (O) and fluorene (F) units are designed and synthesized via the geminal cross-coupling (GCC) of 1,1-dibromoolefins. The incorporation of TAE segments into the conjugated backbone of polyfluorene produces pronounced aggregation-induced ratiometric fluorescence (AIRF), i.e., aggregation-induced emission (AIE) at 520-600 nm grows synergistically with aggregations-caused quenching (ACQ) at 400-450 nm. The content of fluorene unit in the polymer backbones determines the intensity of the initial fluorescence at blue light region. The huge distinction (about 150 nm) in dual emission wavelengths caused by the environment change makes these conjugated polyelectrolytes particularly suitable for ratiometric fluorescence sensing. Based on electrostatic interaction mechanism, the gradual addition of heparin into the cationic conjugated polymers aqueous solutions could induce dual-color fluorescence changes with a detection limit of 9 nM. This work exhibits the great facility of using GCC reaction to synthesis the conjugated TAE polymers with superior AIE properties and special functions. This article is protected by copyright. All rights reserved.

Dynamic Combinatorial Optimization of In Vitro and In Vivo Heparin Antidotes

Heparin-like macromolecules are widely used in clinics as anticoagulant, antiviral, and anticancer drugs. However, the search of heparin antidotes based on small synthetic molecules to control blood coagulation still remains a challenging task due to the physicochemical properties of this anionic polysaccharide. Here, we use a dynamic combinatorial chemistry approach to optimize heparin binders with submicromolar affinity. The recognition of heparin by the most amplified members of the dynamic library has been studied with different experimental (SPR, fluorescence, NMR) and theoretical approaches, rendering a detailed interaction model. The enzymatic assays with selected library members confirm the correlation between the dynamic covalent screening and the in vitro heparin inhibition. Moreover, both ex vivo and in vivo blood coagulation assays with mice show that the optimized molecules are potent antidotes with potential use as heparin reversal drugs. Overall, these results underscore the power of dynamic combinatorial chemistry targeting complex and elusive biopolymers.

The Future of the COVID-19 Pandemic: How Good (or Bad) Can the SARS-CoV2 Spike Protein Get?

Severe acute respiratory syndrome virus 2 (SARS-CoV2) has infected an estimated 400 million people world-wide, causing approximately 6 million deaths from severe coronavirus disease 2019 (COVID-19). The SARS-CoV2 Spike protein plays a critical role in viral attachment and entry into host cells. The recent emergence of highly transmissible variants of SARS-CoV2 has been linked to mutations in Spike. This review provides an overview of the structure and function of Spike and describes the factors that impact Spike’s ability to mediate viral infection as well as the potential limits to how good (or bad) Spike protein can become. Proposed here is a framework that considers the processes of Spike-mediated SARS-CoV2 attachment, dissociation, and cell entry where the role of Spike, from the standpoint of the virus, is to maximize cell entry with each viral-cell collision. Key parameters are identified that will be needed to develop models to identify mechanisms that new Spike variants might exploit to enhance viral transmission. In particular, the importance of considering secondary co-receptors for Spike, such as heparan sulfate proteoglycans is discussed. Accurate models of Spike-cell interactions could contribute to the development of new therapies in advance of the emergence of new highly transmissible SARS-CoV2 variants.

Constructing vascularized hepatic tissue by cell-assembled viscous tissue sedimentation method and its application for vascular toxicity assessment

In vitro Construction of the liver sinusoidal structure using artificial tissue is an important but worthwhile challenge, particularly for assessing the risk of diseases such as sinusoidal obstruction syndrome (SOS). Current models are unsuitable for evaluating the toxicity because of lacking sinusoidal capillary. In this study, we developed a vascularized hepatic tissue (VHT) using a unique tissue engineering technique, the cell assembled viscous tissue by sedimentation (CAViTs) method. The "viscous bodies" created using the CAViTs method exhibited significant self-assembly within 6 h after seeding, promoting cell-cell interaction. The level of albumin secreted by the VHT was four times higher than that of 2D-coculture and maintained for 1 month. The gene expression pattern of the VHT was closer to that of total human liver, compared with the 2D system. Quantitative evaluations of the vascular structure of VHT treated with two typical SOS-inducing compounds, monocrotaline and retrorsine, revealed higher sensitivity (IC₅₀ = 40.35 µM), 19.92 times higher than the cell-viability assay. Thus, VHT represents an innovative in vitro model that mimics the vessel network structure and could become a useful tool for the early screening of compounds associated with a risk of vascular toxicity. STATEMENT OF SIGNIFICANCE: Mimicking sinusoidal structures in in vitro liver model is important to consider from the perspective of predicting hepatotoxicity such like sinusoidal obstruction syndrome (SOS). However, it was difficult to reconstruct the vascular structure within the hepatocyte-rich environment. In this study, we constructed a vascularized hepatic tissue in a high-throughput manner by a unique method using collagen and heparin, and evaluated its applicability to toxicity assessment. Vessel morphology analysis of the model treated by monocrotaline, which is a well-known SOS-inducing compound, could predict the toxicity with higher sensitivity. To the best of our knowledge, this is the first report to provide vascularized hepatic tissues using sinusoidal endothelial cells at least for demonstrating applicability to the evaluation of SOS induction risk.

PDIA3/ERp57 promotes a matrix-rich secretome that stimulates fibroblast adhesion through CCN2

The matricellular glycoprotein thrombospondin1 (TSP1) has complex roles in the extracellular matrix and at cell surfaces, but relatively little is known about its intracellular associations prior to secretion. To search for novel intracellular interactions of TSP1 in situ, we carried out a biotin ligase-based TSP1 interactome screen and identified protein disulphide isomerase A3 (PDIA3/ERp57) as a novel candidate binding protein. In validation, TSP1 and PDIA3 were established to bind in vitro and to colocalise in the endoplasmic reticulum of human dermal fibroblasts (HDF). Loss of PDIA3 function, either by pharmacological inhibition in HDF or in Pdia3^-/- mouse embryo fibroblasts (Pdia3^-/-MEF), led to alterations in the composition of cell-derived ECM, involving changed abundance of fibronectin and TSP1, and was correlated with reduced cell spreading, altered organisation of F-actin and reduced focal adhesions. These cellular phenotypes of Pdia3^-/-MEF were normalised by exposure to conditioned medium (WTCM) or extracellular matrix (WTECM) from wild-type (WT)-MEF. Rescue depended on PDIA3 activity in WT-MEF, and was not prevented by immunodepletion of fibronectin. Heparin-binding proteins in WTCM were found to be necessary for rescue. Comparative quantitative tandem-mass-tag proteomics and functional assays on the heparin-binding secretomes of WT-MEF and Pdia3^-/- MEF identified multiple ECM and growth factor proteins to be down-regulated in the CM of Pdia3^-/- MEF. Of these, CCN2 was identified to be necessary for the adhesion-promoting activity of WTCM on Pdia3^-/- MEF and to bind TSP1. Thus, PDIA3 coordinates fibroblast production of an ECM-rich, pro-adhesive microenvironment, with implications for PDIA3 as a translational target.

Potential Anti-SARS-CoV-2 Activity of Pentosan Polysulfate and Mucopolysaccharide Polysulfate

With the increased prevalence of new SARS-CoV-2 variants of concern, such as Delta and Omicron, the COVID-19 pandemic has become an ongoing human health disaster, killing millions worldwide. SARS-CoV-2 invades its host through the interaction of its spike (S) protein with a host cell receptor, angiotensin-converting enzyme 2 (ACE2). In addition, heparan sulfate (HS) on the surface of host cells plays an important role as a co-receptor for this viral pathogen-host cell interaction. Our previous studies demonstrated that many sulfated glycans, such as heparin, fucoidans, and rhamnan sulfate have anti-SARS-CoV-2 activities. In the current study, a small library of sulfated glycans and highly negatively charged compounds, including pentosan polysulfate (PPS), mucopolysaccharide polysulfate (MPS), sulfated lactobionic acid, sulodexide, and defibrotide, was assembled and evaluated for binding to the S-proteins and inhibition of viral infectivity in vitro. These compounds inhibited the interaction of the S-protein receptor-binding domain (RBD) (wild type and different variants) with immobilized heparin, a highly sulfated HS, as determined using surface plasmon resonance (SPR). PPS and MPS showed the strongest inhibition of interaction of heparin and S-protein RBD. The competitive binding studies showed that the IC50 of PPS and MPS against the S-protein RBD binding to immobilized heparin was ~35 nM and ~9 nM, respectively, much lower than the IC50 for soluble heparin (IC50 = 56 nM). Both PPS and MPS showed stronger inhibition than heparin on the S-protein RBD or spike pseudotyped lentiviral particles binding to immobilized heparin. Finally, in an in vitro cell-based assay, PPS and MPS exhibited strong antiviral activities against pseudotyped viral particles of SARS-CoV-2 containing wild-type or Delta S-proteins.

Heparin interacts with the main protease of SARS-CoV-2 and inhibits its activity

The ability of SARS-CoV-2 to replicate in host cells is dependent on its main protease (M^pro, also called 3CLpro) that cut the viral precursor polyproteins and is a major target for antiviral drug design. Here, we showed that heparin interacts with the M^pro of SARS-CoV-2 and inhibits its activity. Protein fluorescence quenching showed that heparin strongly binds to the M^pro protein with dissociation constants K_D of 16.66 and 31.60 μM at 25 and 35 °C, respectively. From thermodynamic parameters of the interaction, there are hydrophobic and hydrogen bond interactions between them. Fluorescence resonance energy transfer (FRET) assay demonstrated that heparin inhibits the proteolytic activity of M^pro with an inhibition constant Ki of 6.9 nM and a half maximal inhibitory concentrations (IC₅₀) of 7.8 ± 2.6 nM. Furthermore, molecular docking analysis revealed that the recognition and binding groups of heparin within the active site of SARS-CoV-2 M^pro provide important new information for the characteristics of the interactions of heparin with the protease. Our finding suggested that heparin might have a potential role in inhibiting SARS-CoV-2 infection through inhibiting M^pro activity of SARS-CoV-2.

Structural Insights into the Cofactor Role of Heparin/Heparan Sulfate in Binding between the SARS-CoV-2 Spike Protein and Host Angiotensin-Converting Enzyme II

The viral entry process of the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) requires heparin and heparan sulfates from the cell surface, functioning as a cofactor for human angiotensin-converting enzyme 2 (ACE2) for recognizing the receptor-binding domain (RBD) of the spike (S) protein on the surface of the virion. In the present study, the binding poses of an oligosaccharide with four repeating units of GlcNS6S-IdoA2S (octa) predicted by Vina-Carb in the RBD binding site were employed in molecular dynamics (MD) simulations to provide atomic details for studying the cofactor mechanism. The molecular model in the MD simulations reproduced the length- and sequence-dependent behavior observed from the microarray experiments and revealed an important planar U-turn shape for HP/HS binding to RBD. The model for octa with this shape in the ACE2-RBD complex enhanced the interactions in the binding interface. The comparisons with the ACE2-RBD complex suggested that the presence of octa in the RBD binding site blocked the movements in a loop region at the distal end of the RBD binding interface and promoted the contacts of this loop region with the ACE2 N-terminus helix. This study shed light on the atomic and dynamic details for HP/HS interacting with RBD and provided insights into their cofactor role in the ACE2-RBD interactions.

Circadian control of heparan sulfate levels times phagocytosis of amyloid beta aggregates

Alzheimer's Disease (AD) is a neuroinflammatory disease characterized partly by the inability to clear, and subsequent build-up, of amyloid-beta (Aβ). AD has a bi-directional relationship with circadian disruption (CD) with sleep disturbances starting years before disease onset. However, the molecular mechanism underlying the relationship of CD and AD has not been elucidated. Myeloid-based phagocytosis, a key component in the metabolism of Aβ, is circadianly-regulated, presenting a potential link between CD and AD. In this work, we revealed that the phagocytosis of Aβ42 undergoes a daily circadian oscillation. We found the circadian timing of global heparan sulfate proteoglycan (HSPG) biosynthesis was the molecular timer for the clock-controlled phagocytosis of Aβ and that both HSPG binding and aggregation may play a role in this oscillation. These data highlight that circadian regulation in immune cells may play a role in the intricate relationship between the circadian clock and AD.

Sulfated Glycoprotein Synthesis

Chemical protein synthesis has achieved tremendous progress in the past decades. With the development of chemical ligation as powerful tools, the scope of synthetic protein is greatly expanded. Proteoglycans are a class of sulfated glycoproteins widely distributed on the cell surface and in the extracellular matrix, which are extensively engaged in cellular communication events. Consisting of protein backbone and glycosaminoglycan(s) side chain, proteoglycans are highly complex and heterogeneous in nature. Chemical synthesis provides facile and reliable approach to these molecules, with defined glycan structure and sulfation pattern. One remaining problem is that the acid-labile sulfates could hardly survive during the typical solid phase peptide synthesis (SPPS) process. In this chapter, strategic design of a "glycopeptide cassette" for the preparation of sulfated glycoprotein is described. In particular, we provide protocols for the chemical synthesis of ectodomain fragment (23-120) of sulfated glycoprotein syndecan-1.

Heparin-coated iron oxide nanoparticles: application as liver contrast agent, toxicity and pharmacokinetics

The newly prepared heparin-coated iron oxide nanoparticles (Hep-IONPs) contrasted cholangioma tumors in the liver in T2 MRI. NPs were not toxic to rats and rabbits after 14 days of consecutive...

Advance research in biomedical applications on marine sulfated polysaccharide

Marine ecosystem associated organisms are an affluent source of bioactive compounds. Polysaccharides with unique structural and practical entities have gained special studies interest inside the current biomedical zone. Polysaccharides are the main components of marine algae, plants, animals, insects, and microorganisms. In recent times research on seaweed is more persistent for extraction of natural bioactive "Sulfated polysaccharides" (SPs). The considerable amount of SP exists in the algae in the form of fucans, fucoidans, carrageenans, ulvan, etc. Major function of SPs is to act as a defensive lattice towards the infective organism. All SPs possess the high potential and possess a broad range of therapeutic applications as antitumor, immunomodulatory, vaccine adjuvant, anti-inflammatory, anticoagulant, antiviral, antiprotozoal, antimicrobial, antilipemic, therapy of regenerative medicine, also in drug delivery and tissue engineering application. This review aims to discuss the biomedicine applications of sulfated polysaccharides from marine seaweeds.

Conjugated Polymers-based Luminescent Probes for Ratiometric Detection of Biomolecules

Accurate monitoring of the biomolecular changes in biological and physiological environments is of great significance for pathogenesis, development, diagnosis and treatment of diseases. Compared with traditional luminescent probes on the...

Regulation of stem cell fate and function by using bioactive materials with nanoarchitectonics for regenerative medicine

Nanoarchitectonics has emerged as a post-nanotechnology concept. As one of the applications of nanoarchitectonics, this review paper discusses the control of stem cell fate and function as an important issue. For hybrid nanoarchitectonics involving living cells, it is crucial to understand how biomaterials and their nanoarchitected structures regulate behaviours and fates of stem cells. In this review, biomaterials for the regulation of stem cell fate are firstly discussed. Besides multipotent differentiation, immunomodulation is an important biological function of mesenchymal stem cells (MSCs). MSCs can modulate immune cells to treat multiple immune- and inflammation-mediated diseases. The following sections summarize the recent advances of the regulation of the immunomodulatory functions of MSCs by biophysical signals. In the third part, we discussed how biomaterials direct the self-organization of pluripotent stem cells for organoid. Bioactive materials are constructed which mimic the biophysical cues of in vivo microenvironment such as elasticity, viscoelasticity, biodegradation, fluidity, topography, cell geometry, and etc. Stem cells interpret these biophysical cues by different cytoskeletal forces. The different cytoskeletal forces lead to substantial transcription and protein expression, which affect stem cell fate and function. Regulations of stem cells could not be utilized only for tissue repair and regenerative medicine but also potentially for production of advanced materials systems. Materials nanoarchitectonics with integration of stem cells and related biological substances would have high impacts in science and technology of advanced materials.

Automated Solid Phase Assisted Synthesis of a Heparan Sulfate Disaccharide Library

Heparan sulfate (HS) regulates a wide range of biological events, including blood coagulation, cancer development, cell differentiation, and viral infections. It is generally recognized that structures of HS can critically...

Affinity and Specificity for Binding to Glycosaminoglycans Can Be Tuned by Adapting Peptide Length and Sequence

Although glycosaminoglycan (GAG)–protein interactions are important in many physiological and pathological processes, the structural requirements for binding are poorly defined. Starting with GAG-binding peptide CXCL9(74-103), peptides were designed to elucidate the contribution to the GAG-binding affinity of different: (1) GAG-binding motifs (i.e., BBXB and BBBXXB); (2) amino acids in GAG-binding motifs and linker sequences; and (3) numbers of GAG-binding motifs. The affinity of eight chemically synthesized peptides for various GAGs was determined by isothermal fluorescence titration (IFT). Moreover, the binding of peptides to cellular GAGs on Chinese hamster ovary (CHO) cells was assessed using flow cytometry with and without soluble GAGs. The repetition of GAG-binding motifs in the peptides contributed to a higher affinity for heparan sulfate (HS) in the IFT measurements. Furthermore, the presence of Gln residues in both GAG-binding motifs and linker sequences increased the affinity of trimer peptides for low-molecular-weight heparin (LMWH), partially desulfated (ds)LMWH and HS, but not for hyaluronic acid. In addition, the peptides bound to cellular GAGs with differential affinity, and the addition of soluble HS or heparin reduced the binding of CXCL9(74-103) to cellular GAGs. These results indicate that the affinity and specificity of peptides for GAGs can be tuned by adapting their amino acid sequence and their number of GAG-binding motifs.

Shape-Memory ECM-Mimicking Heparin-Modified Nanofibrous Gelatin Scaffold for Enhanced Bone Regeneration in Sinus Augmentation

Biomaterials with clinical maneuverability and predictable bone regeneration are needed in the field of maxillary sinus augmentation. Herein, gelatin was chemically modified with heparin that specifically interacted with and stabilized bone morphogenetic protein-2 (BMP-2). We then introduced thermally induced phase separation to form the injectable, shape-memory, highly porous scaffold for bone regeneration in sinus augmentation. The hydrated heparin-modified nanofibrous gelatin scaffolds (NH-GS) were demonstrated with high resilience and shape-memory property, both macroscopically and microscopically, making them injectable scaffolds and expected to be applied in sinus augmentation. This novel scaffold was verified to be biocompatible and an excellent matrix to support cell attachment, proliferation, and infiltration. Further, the growth factor-loaded NH-GS showed sustained release kinetics of BMP-2 through affinity-based scaffold-growth factor interaction, compared with BMP-2 loaded gelatin sponge (GS) and nanofibrous gelatin scaffold (NF). Both in vitro and in vivo experiments demonstrated that the BMP-2-loaded NH-GS exhibited the highest osteogenesis among the other groups. Taken together, this study introduces a new regenerative strategy in maxillary sinus augmentation, which is injectable with a predefined shape and structure and promotes bone regeneration through a more sustained BMP-2 release.

Revisiting the grammar of Tau aggregation and pathology formation: how new insights from brain pathology are shaping how we study and target Tauopathies

Converging evidence continues to point towards Tau aggregation and pathology formation as central events in the pathogenesis of Alzheimer's disease and other Tauopathies. Despite significant advances in understanding the morphological and structural properties of Tau fibrils, many fundamental questions remain about what causes Tau to aggregate in the first place. The exact roles of cofactors, Tau post-translational modifications, and Tau interactome in regulating Tau aggregation, pathology formation, and toxicity remain unknown. Recent studies have put the spotlight on the wide gap between the complexity of Tau structures, aggregation, and pathology formation in the brain and the simplicity of experimental approaches used for modeling these processes in research laboratories. Embracing and deconstructing this complexity is an essential first step to understanding the role of Tau in health and disease. To help deconstruct this complexity and understand its implication for the development of effective Tau targeting diagnostics and therapies, we firstly review how our understanding of Tau aggregation and pathology formation has evolved over the past few decades. Secondly, we present an analysis of new findings and insights from recent studies illustrating the biochemical, structural, and functional heterogeneity of Tau aggregates. Thirdly, we discuss the importance of adopting new experimental approaches that embrace the complexity of Tau aggregation and pathology as an important first step towards developing mechanism- and structure-based therapies that account for the pathological and clinical heterogeneity of Alzheimer's disease and Tauopathies. We believe that this is essential to develop effective diagnostics and therapies to treat these devastating diseases.

A Genome-Wide CRISPR/Cas9-Based Screen Identifies Heparan Sulfate Proteoglycans as Ligands of Killer-Cell Immunoglobulin-Like Receptors

While human leukocyte antigen (HLA) and HLA-like proteins comprise an overwhelming majority of known ligands for NK-cell receptors, the interactions of NK-cell receptors with non-conventional ligands, particularly carbohydrate antigens, is less well described. We previously found through a bead-based HLA screen that KIR3DS1, a formerly orphan member of the killer-cell immunoglobulin-like receptor (KIR) family, binds to HLA-F. In this study, we assessed the ligand binding profile of KIR3DS1 to cell lines using Fc fusion constructs, and discovered that KIR3DS1-Fc exhibited binding to several human cell lines including ones devoid of HLA. To identify these non-HLA ligands, we developed a magnetic enrichment-based genome-wide CRISPR/Cas9 knock-out screen approach, and identified enzymes involved in the biosynthesis of heparan sulfate as crucial for the binding of KIR3DS1-Fc to K562 cells. This interaction between KIR3DS1 and heparan sulfate was confirmed via surface plasmon resonance, and removal of heparan sulfate proteoglycans from cell surfaces abolished KIR3DS1-Fc binding. Testing of additional KIR-Fc constructs demonstrated that KIR family members containing a D0 domain (KIR3DS1, KIR3DL1, KIR3DL2, KIR2DL4, and KIR2DL5) bound to heparan sulfate, while those without a D0 domain (KIR2DL1, KIR2DL2, KIR2DL3, and KIR2DS4) did not. Overall, this study demonstrates the use of a genome-wide CRISPR/Cas9 knock-out strategy to unbiasedly identify unconventional ligands of NK-cell receptors. Furthermore, we uncover a previously underrecognized binding of various activating and inhibitory KIRs to heparan sulfate proteoglycans that may play a role in NK-cell receptor signaling and target-cell recognition.

Sulfation Code and Conformational Plasticity of l-Iduronic Acid Homo-Oligosaccharides Mimic the Biological Functions of Heparan Sulfate

Recently, the activity of heparan sulfate (HS) has led to the discovery of many drug candidates that have the potential to impact both medical science and human health. However, structural diversity and synthetic challenges impede the progress of HS research. Here, we report a library of novel l-iduronic acid (IdoA)-based HS mimics that are highly tunable in conformation plasticity and sulfation patterns to produce many of the functions of native HS oligosaccharides. The NMR analysis of HS mimics confirmed that 4-O-sulfation enhances the population of the ¹C₄ geometry. Interestingly, the ¹C₄ conformer becomes exclusive upon additional 2-O-sulfation. HS mimic microarray binding studies with different growth factors showed that selectivity and avidity are greatly modulated by the oligosaccharide length, sulfation code, and IdoA conformation. Particularly, we have identified 4-O-sulfated IdoA disaccharide (I-21) as a potential ligand for vascular endothelial growth factor (VEGF₁₆₅), which in a multivalent display modulated endothelial cell proliferation, migration, and angiogenesis. Overall, these results encourage the consideration of HS mimics for therapeutic applications.

Molecularly-imprinted hydrogel beads via self-sacrificing micro-reactors as safe and selective bilirubin adsorbents

For patients who are suffering from liver dysfunction or metabolic obstruction, excessive bilirubin (BIL) in their bodies may cause jaundice with irreversible cerebral injury. Traditional exchange transfusion and photodynamic therapy pose a risk of serious adverse reactions or limited curative effects. Therefore, as a generally used treatment, hemoperfusion (HP) purifies patients' blood with solid adsorbents. However, the development of clinical BIL absorbents is greatly impeded by low selectivity and unsatisfactory blood compatibility. Herein, inspired by oviparity, we propose BIL-imprinted poly(acrylic acid-co-sodium p-styrenesulfonate)-reduced graphene oxide (PAA-SS-rGO@BIL) hydrogel beads as BIL adsorbents via self-sacrificing micro-reactors. In the micro-reactors, cross-linked polymerization is achieved and a solidified gel is formed. The received hydrogel beads show outstanding selective adsorption capabilities toward BIL due to the recognition sites, and π-π and hydrophobic interactions. Such hydrogel beads possess superior blood compatibility owing to their bioinspired heparin-mimicking gel structure. Simulated BIL selective adsorption experiments in vitro demonstrate that the BIL concentrations in the plasma of a patient with severe jaundice can be restored to a moderate level within 3 hours. Therefore, hydrogel beads offer new options for clinical BIL adsorption.

Heparin and Derivatives for Advanced Cell Therapies

Heparin and its derivatives are saving thousands of human lives annually, by successfully preventing and treating thromboembolic events. Although the mode of action during anticoagulation is well studied, their influence on cell behavior is not fully understood as is the risk of bleeding and other side effects. New applications in regenerative medicine have evolved supporting production of cell-based therapeutics or as a substrate for creating functionalized matrices in biotechnology. The currently resurgent interest in heparins is related to the expected combined anti-inflammatory, anti-thrombotic and anti-viral action against COVID-19. Based on a concise summary of key biochemical and clinical data, this review summarizes the impact for manufacturing and application of cell therapeutics and highlights the need for discriminating the different heparins.

Disruption of morphogenic and growth pathways in lysosomal storage diseases

The lysosome achieved a new protagonism that highlights its multiple cellular functions, such as in the catabolism of complex substrates, nutrient sensing, and signaling pathways implicated in cell metabolism and growth. Lysosomal storage diseases (LSDs) cause lysosomal accumulation of substrates and deficiency in trafficking of macromolecules. The substrate accumulation can impact one or several pathways which contribute to cell damage. Autophagy impairment and immune response are widely studied, but less attention is paid to morphogenic and growth pathways and its impact on the pathophysiology of LSDs. Hedgehog pathway is affected with abnormal expression and changes in distribution of protein levels, and a reduced number and length of primary cilia. Moreover, growth pathways are identified with delay in reactivation of mTOR that deregulate termination of autophagy and reformation of lysosomes. Insulin resistance caused by changes in lipids rafts has been described in different LSDs. While the genetic and biochemical bases of deficient proteins in LSDs are well understood, the secondary molecular mechanisms that disrupt wider biological processes associated with LSDs are only now becoming clearer. Therefore, we explored how specific signaling pathways can be related to specific LSDs, showing that a system medicine approach could be a valuable tool for the better understanding of LSD pathogenesis. This article is categorized under: Metabolic Diseases > Molecular and Cellular Physiology.

Poly(2-alkyl-2-oxazoline)-Heparin Hydrogels-Expanding the Physicochemical Parameter Space of Biohybrid Materials

Poly(ethylene glycol) (PEG)-glycosaminoglycan (GAG) hydrogel networks are established as very versatile biomaterials. Herein, the synthetic gel component of the biohybrid materials is systematically varied by combining different poly(2-alkyl-2-oxazolines) (POx) with heparin applying a Michael-type addition crosslinking scheme: POx of gradated hydrophilicity and temperature-responsiveness provides polymer networks of distinctly different stiffness and swelling. Adjusting the mechanical properties and the GAG concentration of the gels to similar values allows for modulating the release of GAG-binding growth factors (VEGF165 and PDGF-BB) by the choice of the POx and its temperature-dependent conformation. Adsorption of fibronectin, growth of fibroblasts, and bacterial adhesion scale with the hydrophobicity of the gel-incorporated POx. In vitro hemocompatibility tests with freshly drawn human whole blood show advantages of POx-based gels compared to the PEG-based reference materials. Biohybrid POx hydrogels can therefore enable biomedical technologies requiring GAG-based materials with customized and switchable physicochemical characteristics.

Analytical challenges of glycosaminoglycans at biological interfaces

The analysis of glycosaminoglycans (GAGs) is a challenging task due to their high structural heterogeneity, which results in diverse GAG chains with similar chemical properties. Simultaneously, it is of high importance to understand their role and behavior in biological systems. It has been known for decades now that GAGs can interact with lipid molecules and thus contribute to the onset of atherosclerosis, but their interactions at and with biological interfaces, such as the cell membrane, are yet to be revealed. Here, analytical approaches that could yield important knowledge on the GAG-cell membrane interactions as well as the synthetic and analytical advances that make their study possible are discussed. Due to recent developments in laser technology, we particularly focus on nonlinear spectroscopic methods, especially vibrational sum-frequency generation spectroscopy, which has the potential to unravel the structural complexity of heterogeneous biological interfaces in contact with GAGs, in situ and in real time.

Customizing biohybrid cryogels to serve as ready-to-use delivery systems of signaling proteins

Macroporous cryogels have recently gained increasing interest for the controlled administration of signaling proteins in tissue engineering due to an advantageous combination of material properties. However, most of the previously reported cryogel systems did not allow for tunable, sustained protein release. We therefore designed a set of ready-to-use multi-armed polyethylene glycol (starPEG)-heparin cryogel systems containing different amounts of the protein-affine glycosaminoglycan component heparin to enable systematically tunable long-term delivery of different signaling proteins without affecting other cell-instructive properties. Experimental data and mathematical modeling indicate that the macroporous structure causes local differences in the concentration of proteins released into the pores and in the surrounding of the cryogels. As a proof-of-concept for their ready-to-use potential, cryogels pre-functionalized with signaling proteins and cell adhesion-peptides were demonstrated to induce the neuronal differentiation of colonizing pheochromocytoma cells. The elaborated approach opens up new perspectives for cryogels as easily storable and applicable systems for the precision delivery of signaling proteins.

Mass Spectrometric Methods for the Analysis of Heparin and Heparan Sulfate

Glycosaminoglycans like heparin and heparan sulfate exhibit a high degree of structural microheterogeneity. This structural heterogeneity results from the biosynthetic process that produces these linear polysaccharides in cells and tissues. Heparin and heparan sulfate play critical roles in normal physiology and pathophysiology, hence it is important to understand how their structural features may influence overall activity. Therefore, high-resolution techniques like mass spectrometry represent a key part of the suite of methodologies available to probe the fine structural details of heparin and heparan sulfate. This chapter outlines the application of techniques like LC-MS and LC-MS/MS to study the composition of these polysaccharides, and techniques like GPC-MS that allow for an analysis of oligosaccharide fragments in these mixtures.

Methods for the Production of Recombinant Heparosan, a Critical Heparin Precursor, from Nonpathogenic E. coli Strains

Heparin is an essential anticoagulant drug discovered over a century ago. Heparin is the second most highly used natural drug and remains a mainstay of therapy with an expected global market share of more than $14 billion in the next 10 years. However, it is still naturally derived from unsustainable animal sources, such as bovine lungs and porcine intestines, as an unfractionated, heterogeneous complex mixture with unpredictable pharmacokinetic properties. Extensive research has been done in devising bioengineering and chemical approaches to produce structurally specific heparin and heparin-like polymers. Though several challenges remain, one of the main bottlenecks is the rapid, high-yield production of recombinant heparosan, a heparin precursor, which is originally isolated from a pathogenic E. coli K5 strain. Herein, we outline the methods for producing metabolically engineered size-specific heparosan, by transforming the essential heparosan biosynthetic genes into nonpathogenic E.coli strain BL21(DE3), in a highly controlled manner. The methods described herein are promising and can be easily scaled up for large-scale production of heparin-like structures.

Preparation of Nanosensors for Detecting the Activity of Glycosaminoglycan Cleaving Enzymes

Glycosaminoglycans (GAGs) play crucial roles in several biological processes including cell division, angiogenesis, anticoagulation, neurogenesis, axon guidance and growth, and viral and bacterial infections among others. The GAG cleaving hydrolases/lyases play a major role in the control of GAG structures, functions, and turn over. Dysregulation of GAG cleaving enzymes in vivo are linked to a number of human diseases including cancer, diabetes, atherosclerosis, arthritis, inflammation, and cardiovascular diseases. Several GAG cleaving enzymes are widely used for studying GAG glycobiology: heparitinases, chondroitinases, heparanases, hyaluronidases, and keratanases. Herein, we describe a method to synthesize four distinct nanometal surface energy transfer (NSET)-based gold-GAG-dye conjugates (nanosensors). Heparin, chondroitin sulfate, heparan sulfate, and hyaluronic acid are covalently linked with distinct fluorescent dyes and then immobilized on gold nanoparticles (AuNPs) to build nanosensors that serve as excellent substrates for GAG cleaving enzymes. Upon treatment of nanosensors with their respective GAG cleaving enzymes, dye-labeled oligosaccharides/disaccharides are released from AuNPs resulting in enhanced fluorescence recovery. These nanosensors have a great promise as diagnostic tools in various human pathophysiological conditions for detecting dysregulated expression of GAG cleaving enzymes and also as a sensitive analytical tool for assessing the quality control of pharmaceutical grade heparin polysaccharides that are produced in millions of small- and medium-sized animal slaughter houses worldwide.

Sulfated poly-amido-saccharides (sulPASs) are anticoagulants in vitro and in vivo

Anticoagulant therapeutics are a mainstay of modern surgery and of clotting disorder management such as venous thrombosis, yet performance and supply limitations exist for the most widely used agent - heparin. Herein we report the first synthesis, characterization, and performance of sulfated poly-amido-saccharides (sulPASs) as heparin mimetics. sulPASs inhibit the intrinsic pathway of coagulation, specifically FXa and FXIa, as revealed by ex vivo human plasma clotting assays and serine protease inhibition assays. sulPASs activity positively correlates with molecular weight and degree of sulfation. Importantly, sulPASs are not degraded by heparanases and are non-hemolytic. In addition, their activity is reversed by protamine sulfate, unlike small molecule anticoagulants. In an in vivo murine model, sulPASs extend clotting time in a dose dependent manner with bleeding risk comparable to heparin. These findings support continued development of synthetic anticoagulants to address the clinical risks and shortages associated with heparin.

Amphiphilic Copolymers for Versatile, Facile, and In Situ Tunable Surface Biofunctionalization

Precision surface engineering is key to advanced biomaterials. A new platform of PEGylated styrene-maleic acid copolymers for adsorptive surface biofunctionalization is reported. Balanced amphiphilicity renders the copolymers water-soluble but strongly affine for surfaces. Fine-tuning of their molecular architecture provides control over adsorptive anchorage onto specific materials-which is why they are referred to as "anchor polymers" (APs)-and over structural characteristics of the adsorbed layers. Conjugatable with an array of bioactives-including cytokine-complexing glycosaminoglycans, cell-adhesion-mediating peptides and antimicrobials-APs can be applied to customize materials for demanding biotechnologies in uniquely versatile, simple, and robust ways. Moreover, homo- and heterodisplacement of adsorbed APs provide unprecedented means of in situ alteration and renewal of the functionalized surfaces. The related options are exemplified with proof-of-concept experiments of controlled bacterial adhesion, human umbilical vein endothelial cell, and induced pluripotent cell growth on AP-functionalized surfaces.

Construction of heparin-based hydrogel incorporated with Cu5.4O ultrasmall nanozymes for wound healing and inflammation inhibition

Excessive production of inflammatory chemokines and reactive oxygen species (ROS) can cause a feedback cycle of inflammation response that has a negative effect on cutaneous wound healing. The use of wound-dressing materials that simultaneously absorb chemokines and scavenge ROS constitutes a novel 'weeding and uprooting' treatment strategy for inflammatory conditions. In the present study, a composite hydrogel comprising an amine-functionalized star-shaped polyethylene glycol (starPEG) and heparin for chemokine sequestration as well as Cu5.4O ultrasmall nanozymes for ROS scavenging (Cu5.4O@Hep-PEG) was developed. The material effectively adsorbs the inflammatory chemokines monocyte chemoattractant protein-1 and interleukin-8, decreasing the migratory activity of macrophages and neutrophils. Furthermore, it scavenges the ROS in wound fluids to mitigate oxidative stress, and the sustained release of Cu5.4O promotes angiogenesis. In acute wounds and impaired-healing wounds (diabetic wounds), Cu5.4O@Hep-PEG hydrogels outperform the standard-of-care product Promogram® in terms of inflammation reduction, increased epidermis regeneration, vascularization, and wound closure.

Heparin and Its Derivatives: Challenges and Advances in Therapeutic Biomolecules

Heparin has been extensively studied as a safe medicine and biomolecule over the past few decades. Heparin derivatives, including low-molecular-weight heparins (LMWH) and heparin pentasaccharide, are effective anticoagulants currently used in clinical settings. They have also been studied as functional biomolecules or biomaterials for various therapeutic uses to treat diseases. Heparin, which has a similar molecular structure to heparan sulfate, can be used as a remarkable biomedicine due to its uniquely high safety and biocompatibility. In particular, it has recently drawn attention for use in drug-delivery systems, biomaterial-based tissue engineering, nanoformulations, and new drug-development systems through molecular formulas. A variety of new heparin-based biomolecules and conjugates have been developed in recent years and are currently being evaluated for use in clinical applications. This article reviews heparin derivatives recently studied in the field of drug development for the treatment of various diseases.

Translational Applications of Hydrogels

Advances in hydrogel technology have unlocked unique and valuable capabilities that are being applied to a diverse set of translational applications. Hydrogels perform functions relevant to a range of biomedical purposes-they can deliver drugs or cells, regenerate hard and soft tissues, adhere to wet tissues, prevent bleeding, provide contrast during imaging, protect tissues or organs during radiotherapy, and improve the biocompatibility of medical implants. These capabilities make hydrogels useful for many distinct and pressing diseases and medical conditions and even for less conventional areas such as environmental engineering. In this review, we cover the major capabilities of hydrogels, with a focus on the novel benefits of injectable hydrogels, and how they relate to translational applications in medicine and the environment. We pay close attention to how the development of contemporary hydrogels requires extensive interdisciplinary collaboration to accomplish highly specific and complex biological tasks that range from cancer immunotherapy to tissue engineering to vaccination. We complement our discussion of preclinical and clinical development of hydrogels with mechanical design considerations needed for scaling injectable hydrogel technologies for clinical application. We anticipate that readers will gain a more complete picture of the expansive possibilities for hydrogels to make practical and impactful differences across numerous fields and biomedical applications.

Pentamethinium Salts Nanocomposite for Electrochemical Detection of Heparin

This study presents a simple route to heparin detection and develops a voltammetric approach using supramolecular principles and nanomaterials. Nanocomposites, including gold nanoparticles (AuNPs) and γ-substituted pentamethinium salts (PMS) deposited on a glass carbon (GC) electrode surface (GC/AuNPs/PMS) and covered by a plasticized poly(vinyl chloride) (PVC) membrane, are proposed for heparin detection. The conductivity of the nonconducting PVC-plasticized membrane is guaranteed by AuNPs, and the selectivity is provided by the interaction between γ-substituted PMS and anionic analytes. In order to extend the linear range, it is necessary to apply a solvent compatible with PVC-plasticized membrane, namely tetrahydrofuran. The proposed voltammetric sensor showed a concentration dependence from 1.72 up to 45.02 IU mL⁻¹ heparin and was used for heparin detection in saline and biological samples with recovery of 95.1–100.9%.

Platelet factor 4 polyanion immune complexes: heparin induced thrombocytopenia and vaccine-induced immune thrombotic thrombocytopenia

BACKGROUND

This is a review article on heparin-induced thrombocytopenia, an adverse effect of heparin therapy, and vaccine-induced immune thrombotic thrombocytopenia, occurring in some patients administered certain coronavirus vaccines.

MAIN BODY/TEXT

Immune-mediated thrombocytopenia occurs when specific antibodies bind to platelet factor 4 /heparin complexes. Platelet factor 4 is a naturally occurring chemokine, and under certain conditions, may complex with negatively charged molecules and polyanions, including heparin. The antibody-platelet factor 4/heparin complex may lead to platelet activation, accompanied by other cascading reactions, resulting in cerebral sinus thrombosis, deep vein thrombosis, lower limb arterial thrombosis, myocardial infarction, pulmonary embolism, skin necrosis, and thrombotic stroke. If untreated, heparin-induced thrombocytopenia can be life threatening. In parallel, rare incidents of spontaneous vaccine-induced immune thrombotic thrombocytopenia can also occur in some patients administered certain coronavirus vaccines. The role of platelet factor 4 in vaccine-induced thrombosis with thrombocytopenia syndrome further reinforces the importance the platelet factor 4/polyanion immune complexes and the complications that this might pose to susceptible individuals. These findings demonstrate, how auxiliary factors can complicate heparin therapy and drug development. An increasing interest in biomanufacturing heparins from non-animal sources has driven a growing interest in understanding the biology of immune-mediated heparin-induced thrombocytopenia, and therefore, the development of safe and effective biosynthetic heparins.

SHORT CONCLUSION

In conclusion, these findings further reinforce the importance of the binding of platelet factor 4 with known and unknown polyanions, and the complications that these might pose to susceptible patients. In parallel, these findings also demonstrate how auxiliary factors can complicate the heparin drug development.

What is the Sugar Code?

A code is defined by the nature of the symbols, which are used to generate information‐storing combinations (e. g. oligo‐ and polymers). Like nucleic acids and proteins, oligo‐ and polysaccharides are ubiquitous, and they are a biochemical platform for establishing molecular messages. Of note, the letters of the sugar code system (third alphabet of life) excel in coding capacity by making an unsurpassed versatility for isomer (code word) formation possible by variability in anomery and linkage position of the glycosidic bond, ring size and branching. The enzymatic machinery for glycan biosynthesis (writers) realizes this enormous potential for building a large vocabulary. It includes possibilities for dynamic editing/erasing as known from nucleic acids and proteins. Matching the glycome diversity, a large panel of sugar receptors (lectins) has developed based on more than a dozen folds. Lectins ‘read’ the glycan‐encoded information. Hydrogen/coordination bonding and ionic pairing together with stacking and C−H/π‐interactions as well as modes of spatial glycan presentation underlie the selectivity and specificity of glycan‐lectin recognition. Modular design of lectins together with glycan display and the nature of the cognate glycoconjugate account for the large number of post‐binding events. They give an entry to the glycan vocabulary its functional, often context‐dependent meaning(s), hereby building the dictionary of the sugar code.

Heparin Microislands in Microporous Annealed Particle Scaffolds for Accelerated Diabetic Wound Healing

Mimicking growth factor-ECM interactions for promoting cell migration is a powerful technique to improve tissue integration with biomaterial scaffolds for the regeneration of damaged tissues. This has been attempted by scaffold-mediated controlled delivery of exogenous growth factors; however, the predetermined nature of this delivery can limit the scaffold's ability to meet each wound's unique spatiotemporal regenerative needs and presents translational hurdles. To address this limitation, we present a new approach to growth factor presentation by incorporating heparin microislands, which are spatially isolated heparin-containing microparticles that can reorganize and protect endogenous local growth factors via heterogeneous sequestration at the microscale in vitro and result in functional improvements in wound healing. More specifically, we incorporated our heparin microislands within microporous annealed particle (MAP) scaffolds, which allows facile tuning of microenvironment heterogeneity through ratiometric mixing of microparticle sub-populations. In this manuscript, we demonstrate the ability of heparin microislands to heterogeneously sequester applied growth factor and control downstream cell migration in vitro. Further, we present their ability to significantly improve wound healing outcomes (epidermal regeneration and re-vascularization) in a diabetic wound model relative to two clinically relevant controls.

Peptide Inhibitors of Vascular Endothelial Growth Factor A: Current Situation and Perspectives

Vascular endothelial growth factors (VEGFs) are the family of extracellular signaling proteins involved in the processes of angiogenesis. VEGFA overexpression and altered regulation of VEGFA signaling pathways lead to pathological angiogenesis, which contributes to the progression of various diseases, such as age-related macular degeneration and cancer. Monoclonal antibodies and decoy receptors have been extensively used in the anti-angiogenic therapies for the neutralization of VEGFA. However, multiple side effects, solubility and aggregation issues, and the involvement of compensatory VEGFA-independent pro-angiogenic mechanisms limit the use of the existing VEGFA inhibitors. Short chemically synthesized VEGFA binding peptides are a promising alternative to these full-length proteins. In this review, we summarize anti-VEGFA peptides identified so far and discuss the molecular basis of their inhibitory activity to highlight their pharmacological potential as anti-angiogenic drugs.

Midkine Interaction with Chondroitin Sulfate Model Synthetic Tetrasaccharides and Their Mimetics: The Role of Aromatic Interactions

Midkine (MK) is a neurotrophic factor that participates in the embryonic central nervous system (CNS) development and neural stem cell regulation, interacting with sulfated glycosaminoglycans (GAGs). Chondroitin sulfate (CS) is the natural ligand in the CNS. In this work, we describe the interactions between a library of synthetic models of CS-types and mimics. We did a structural study of this library by NMR and MD (Molecular Dynamics), concluding that the basic shape is controlled by similar geometry of the glycosidic linkages. Their 3D structures are a helix with four residues per turn, almost linear. We have studied the tetrasaccharide-midkine complexes by ligand observed NMR techniques and concluded that the shape of the ligands does not change upon binding. The ligand orientation into the complex is very variable. It is placed inside the central cavity of MK formed by the two structured beta-sheets domains linked by an intrinsically disordered region (IDR). Docking analysis confirmed the participation of aromatics residues from MK completed with electrostatic interactions. Finally, we test the biological activity by increasing the MK expression using CS tetrasaccharides and their capacity in enhancing the growth stimulation effect of MK in NIH3T3 cells.

Heparin promotes fibrillation of most phenol-soluble modulin virulence peptides from Staphylococcus aureus

Phenol-soluble modulins (PSMs), such as α-PSMs, β-PSMs, and δ-toxin, are virulence peptides secreted by different Staphylococcus aureus strains. PSMs are able to form amyloid fibrils, which may strengthen the biofilm matrix that promotes bacterial colonization of and extended growth on surfaces (e.g., cell tissue) and increases antibiotic resistance. Many components contribute to biofilm formation, including the human-produced highly sulfated glycosaminoglycan heparin. Although heparin promotes S. aureus infection, the molecular basis for this is unclear. Given that heparin is known to induce fibrillation of a wide range of proteins, we hypothesized that heparin aids bacterial colonization by promoting PSM fibrillation. Here, we address this hypothesis using a combination of thioflavin T-fluorescence kinetic studies, CD, FTIR, electron microscopy, and peptide microarrays to investigate the mechanism of aggregation, the structure of the fibrils, and identify possible binding regions. We found that heparin accelerates fibrillation of all α-PSMs (except PSMα2) and δ-toxin but inhibits β-PSM fibrillation by blocking nucleation or reducing fibrillation levels. Given that S. aureus secretes higher levels of α-PSM than β-PSM peptides, heparin is therefore likely to promote fibrillation overall. Heparin binding is driven by multiple positively charged lysine residues in α-PSMs and δ-toxins, the removal of which strongly reduced binding affinity. Binding of heparin did not affect the structure of the resulting fibrils, that is, the outcome of the aggregation process. Rather, heparin provided a scaffold to catalyze or inhibit fibrillation. Based on our findings, we speculate that heparin may strengthen the bacterial biofilm and therefore enhance colonization via increased PSM fibrillation.

Isolation methods commonly used to study the liposomal protein corona suffer from contamination issues

The liposomal protein corona has been the focus of numerous studies, but there is still no consensus regarding its extent and composition. Rather, the literature is full of conflicting reports on the matter. To elucidate whether there could be a methodological explanation for this, we here scrutinize the efficiency of three commonly used liposome isolation methods at isolating stealth liposomes from human plasma. Firstly, we show that size-exclusion chromatography (SEC) in its standard form is prone to isolating unbound protein material together with the liposomes, but also that the method may be optimized to mitigate this issue. Secondly, we demonstrate that SEC in combination with membrane ultrafiltration is no better at removing the unbound protein material than SEC alone. Thirdly, we show that centrifugation is not able to pellet the liposomes. Overall, our results suggest that previous research on the liposomal protein corona may have suffered from significant methodological problems, in particular related to contaminant proteins interfering with the analysis of the protein corona. We believe that the data presented here may help guide future research around this challenge to reach a converging understanding about the properties of the protein corona on liposomes. STATEMENT OF SIGNIFICANCE: Upon administration into the circulatory system, liposomal drug carriers encounter an environment rich in proteins. These proteins may adsorb to the liposomes to form what is known as the protein corona, potentially governing the interactions of the liposomes with tissues and cells. However, despite decades of intense research efforts, there is currently no clear understanding about the extent and composition of the liposomal protein corona, making it impossible to assess its mechanistic importance. Here we report that the methods commonly used to isolate liposomes from blood plasma or serum to study the protein corona are susceptible to protein contamination. This may be the underlying technical reason for the current confusion about the characteristics of the liposomal protein corona.

Heparin-mediated electrostatic immobilization of bFGF via functional polymer films for enhanced self-renewal of human neural stem cells

Preserving the self-renewal capability of undifferentiated human neural stem cells (hNSCs) is one of the crucial prerequisites for efficient hNSC-based regenerative medicine. Considering that basic fibroblast growth factor (bFGF) is one of the key contributing factors in maintaining the self-renewal property of hNSCs, the bioactivity and stability of bFGF in the hNSC culture should be regulated carefully. In this study, we developed a functional polymer film of poly(glycidyl methacrylate (GMA)-co-N,N-dimethylaminoethyl methacrylate (DMAEMA)) (coGD, or p(GMA-co-DMAEMA)) via initiated chemical vapor deposition (iCVD), which facilitated a stable, electrostatic adsorption of heparin and subsequent immobilization of bFGF. The bFGF-immobilized coGD surface substantially enhanced the proliferation rate and neurosphere forming ability of hNSCs compared to tissue culture plate (TCP). The expression of the stemness markers of hNSCs such as NESTIN and SOX-2 was also upregulated prominently on the coGD surface. Also, the hNSCs cultured on the coGD surface showed enhanced neurogenesis upon spontaneous differentiation. The immobilized bFGF on the coGD surface stimulated the expression of bFGF receptors and subsequently activated the mitogen-activated protein kinase (MAPK) pathway, attributed to the increase in self-renewal property of hNSCs. Our results indicate that the coGD surface allowed in situ heparin-mediated bFGF immobilization, which served as a robust platform to generate hNSC neurospheres with enhanced self-renewal and differentiation capabilities and thereby will prompt an advance in the field of therapeutics of neurodegenerative diseases.

Adeno-Associated Virus (AAV) Gene Delivery: Dissecting Molecular Interactions upon Cell Entry

Human gene therapy has advanced from twentieth-century conception to twenty-first-century reality. The recombinant Adeno-Associated Virus (rAAV) is a major gene therapy vector. Research continues to improve rAAV safety and efficacy using a variety of AAV capsid modification strategies. Significant factors influencing rAAV transduction efficiency include neutralizing antibodies, attachment factor interactions and receptor binding. Advances in understanding the molecular interactions during rAAV cell entry combined with improved capsid modulation strategies will help guide the design and engineering of safer and more efficient rAAV gene therapy vectors.

Pre-analytical considerations in biomarker research: focus on cardiovascular disease

Clinical biomarker research is growing at a fast pace, particularly in the cardiovascular field, due to the demanding requirement to provide personalized precision medicine. The lack of a distinct molecular signature for each cardiovascular derangement results in a one-size-fits-all diagnostic and therapeutic approach, which may partially explain suboptimal outcomes in heterogeneous cardiovascular diseases (e.g., heart failure with preserved ejection fraction). A multidimensional approach using different biomarkers is quickly evolving, but it is necessary to consider pre-analytical variables, those to which a biological sample is subject before being analyzed, namely sample collection, handling, processing, and storage. Pre-analytical errors can induce systematic bias and imprecision, which may compromise research results, and are easy to avoid with an adequate study design. Academic clinicians and investigators must be aware of the basic considerations for biospecimen management and essential pre-analytical recommendations as lynchpin for biological material to provide efficient and valid data.

Tuning the network charge of biohybrid hydrogel matrices to modulate the release of SDF-1

The delivery of chemotactic signaling molecules via customized biomaterials can effectively guide the migration of cells to improve the regeneration of damaged or diseased tissues. Here, we present a novel biohybrid hydrogel system containing two different sulfated glycosaminoglycans (sGAG)/sGAG derivatives, namely either a mixture of short heparin polymers (Hep-Mal) or structurally defined nona-sulfated tetrahyaluronans (9s-HA4-SH), to precisely control the release of charged signaling molecules. The polymer networks are described in terms of their negative charge, i.e. the anionic sulfate groups on the saccharides, using two parameters, the integral density of negative charge and the local charge distribution (clustering) within the network. The modulation of both parameters was shown to govern the release characteristics of the chemotactic signaling molecule SDF-1 and allows for seamless transitions between burst and sustained release conditions as well as the precise control over the total amount of delivered protein. The obtained hydrogels with well-adjusted release profiles effectively promote MSC migration in vitro and emerge as promising candidates for new treatment modalities in the context of bone repair and wound healing.

Recent Progress on Cellulose-Based Ionic Compounds for Biomaterials

Glycans play important roles in all major kingdoms of organisms, such as archea, bacteria, fungi, plants, and animals. Cellulose, the most abundant polysaccharide on the Earth, plays a predominant role for mechanical stability in plants, and finds a plethora of applications by humans. Beyond traditional use, biomedical application of cellulose becomes feasible with advances of soluble cellulose derivatives with diverse functional moieties along the backbone and modified nanocellulose with versatile functional groups on the surface due to the native features of cellulose as both cellulose chains and supramolecular ordered domains as extractable nanocellulose. With the focus on ionic cellulose-based compounds involving both these groups primarily for biomedical applications, a brief introduction about glycoscience and especially native biologically active glycosaminoglycans with specific biomedical application areas on humans is given, which inspires further development of bioactive compounds from glycans. Then, both polymeric cellulose derivatives and nanocellulose-based compounds synthesized as versatile biomaterials for a large variety of biomedical applications, such as for wound dressings, controlled release, encapsulation of cells and enzymes, and tissue engineering, are separately described, regarding the diverse routes of synthesis and the established and suggested applications for these highly interesting materials.

Engineering the Composition of Microfibers to Enhance the Remodeling of a Cell-Free Vascular Graft

The remodeling of vascular grafts is critical for blood vessel regeneration. However, most scaffold materials have limited cell infiltration. In this study, we designed and fabricated a scaffold that incorporates a fast-degrading polymer polydioxanone (PDO) into the microfibrous structure by means of electrospinning technology. Blending PDO with base polymer decreases the density of electrospun microfibers yet did not compromise the mechanical and structural properties of the scaffold, and effectively enhanced cell infiltration. We then used this technique to fabricate a tubular scaffold with heparin conjugated to the surface to suppress thrombosis, and the construct was implanted into the carotid artery as a vascular graft in animal studies. This graft significantly promoted cell infiltration, and the biochemical cues such as immobilized stromal cell-derived factor-1α further enhanced cell recruitment and the long-term patency of the grafts. This work provides an approach to optimize the microfeatures of vascular grafts, and will have broad applications in scaffold design and fabrication for regenerative engineering.

Conformational changes of GDNF-derived peptide induced by heparin, heparan sulfate, and sulfated hyaluronic acid - Analysis by circular dichroism spectroscopy and molecular dynamics simulation

Glial-cell-line-derived neurotrophic factor (GDNF) is a protein that has therapeutic potential in the treatment of Parkinson's disease and other neurodegenerative diseases. The activity of GDNF is highly dependent on the interaction with sulfated glycans which bind at the N-terminus consisting of 19 residues. Herein, we studied the influence of different glycosaminoglycan (i.e., glycan; GAG) molecules on the conformation of a GDNF-derived peptide (GAG binding motif, sixteen amino acid residues at the N-terminus) using both experimental and theoretical studies. The GAG molecules employed in this study are heparin, heparan sulfate, hyaluronic acid, and sulfated hyaluronic acid. Circular dichroism spectroscopy was employed to detect conformational changes induced by the GAG molecules; molecular dynamics simulation studies were performed to support the experimental results. Our results revealed that the sulfated GAG molecules bind strongly with GDNF peptide and induce alpha-helical structure in the peptide to some extent.