Cationic Derivatives of Dextran and Hydroxypropylcellulose as Novel Potential Heparin Antagonists

External Trigger Free Charge Switchable Cationic Ligands in the Design of Safe and Effective Universal Heparin Antidote

Thrombosis, the formation of blood clots within a blood vessel, can lead to severe complications including pulmonary embolism, cardiac arrest, and stroke. The most widely administered class of anticoagulants is heparin-based anticoagulants such as unfractionated heparin, low-molecular weight heparins (LMWHs), and fondaparinux. Protamine is the only FDA-approved heparin antidote. Protamine has limited efficacy neutralizing LMWHs and no reversal activity against fondaparinux. The use of protamine can lead to complications, including excessive bleeding, hypotension, and hypersensitivity, and has narrow therapeutic window. In this work, a new concept in the design of a universal heparin antidote: switchable protonation of cationic ligands, is presented. A library of macromolecular polyanion inhibitors (MPIs) is synthesized and screened to identify molecules that can neutralize all heparins with high selectivity and reduced toxicity. MPIs are developed by assembling cationic binding groups possessing switchable protonation states onto a polymer scaffold. By strategically selecting the identity and modulating the density of cationic binding groups on the polymer scaffold, a superior universal heparin reversal agent is developed with improved heparin-binding activity and increased hemocompatibility profiles leading to minimal effect on hemostasis. The activity of this heparin antidote is demonstrated using in vitro and in vivo studies.

Cationic Dextran Stearate (Dex-St-GTMAC): Synthesis and Evaluation as Polymeric Micelles for Indomethacin Corneal Penetration

Background Indomethacin as a non-steroidal anti-inflammatory drug (NSAID) is commonly used to treat some ocular inflammatory disorders. Unfortunately, indomethacin is a drug that is poorly soluble in water; therefore, it has low efficacy. An attractive approach is the targeted delivery of indomethacin to the cornea using cationic dextran stearate as a polymeric micelle drug carrier. Methods A dextran stearate-glycidyl trimethylammonium chloride (Dex-St-GTMAC) copolymer was prepared through the reaction of GTMAC, stearoyl chloride, and dextran. Then, Dex-St-GTMAC was characterized by Fourier transform infrared (FT-IR) spectroscopy and 1H NMR spectroscopy. Dex-St-GTMAC forms micelles in the presence of indomethacin. The prepared polymeric micelles were characterized for size, ζ-potential, drug loading, particle morphology, critical micelle concentration, and encapsulation efficiency. To study the irritation potential of the indomethacin-loaded Dex-St-GTMAC, Het-Cam and Draize tests have been performed. Prepared cationic micelles were subjected to the in vitro drug release and ex vivotrans-corneal permeation test. Results The dialysis method was used for the preparation of indomethacin-loaded micelles (10, 20, and 30%). Measurement of the particle size showed a mean diameter of 122.1 and 150.9 nm for the drug-loaded micelles. Scanning electron microscopy (SEM) images showed that the morphology of the particles is spherical. 10% formulation was chosen as the best formulation due to more surface charge and reasonable drug loading. ζ-potential measurement for the 10% drug-containing micelles showed a value of +39.1 mV. Drug loading efficiency and the encapsulation efficiency for 10% drug-containing micelles were 6.36 and 63.61%, respectively. The results of the Het-Cam and Draize tests indicated that the indomethacin-loaded Dex-St-GTMAC formulation had no toxicity to eye tissues. Based on our results, the prepared micelles (indomethacin-loaded Dex-St-GTMAC) exhibited a sustained drug release pattern compared to the control group. Indomethacin penetration from the micelles to the excised bovine cornea was 1.75-fold greater than the control (indomethacin 0.1% in phosphate-buffered saline (PBS)). Conclusions Data from the ζ-potential, SEM, drug loading capacity, and in vitro drug release studies indicated that cationic dextran stearate polymeric micelles are an appropriate carrier for the efficient penetration of indomethacin into cornea tissues.

The Use of a Barley-Based Well to Define Cationic Betaglucan to Study Mammalian Cell Toxicity Associated with Interactions with Biological Structures

Among potential macromolecule-based pharmaceuticals, polycations seem particularly interesting due to their proven antimicrobial properties and use as vectors in gene therapy. This makes an understanding of the mechanisms of these molecules' interaction with living structures important, so the goal of this paper was to propose and carry out experiments that will allow us to characterize these phenomena. Of particular importance is the question of toxicity of such structures to mammalian cells and, in the work presented here, two lines, normal fibroblasts 3T3-L1 and A549 lung cancer, were used to determine this. In this work, three well-defined cationic derivatives of barley-derived betaglucans obtained in a reaction with glycidyltrimethylammonium chloride (BBGGTMAC) with different degrees of cationization (50, 70, and 100% per one glucose unit) and electrostatic charge were studied. The studies address interactions of these polymers with proteins (bovine serum proteins and BSA), nucleic acids (DNA), glycosaminoglycans (heparin), and biological membranes. The results described in this study make it possible to indicate that toxicity is most strongly influenced by interactions with biological membranes and is closely related to the electrostatic charge of the macromolecule. The presentation of this observation was the goal of this publication. This paper also shows, using fluorescently labeled variants of polymers, the penetration and impact on cell structure (only for the polymer with the highest substitution binding to cell membranes is observed) by using confocal and SEM (for the polymer with the highest degree of substitution, and the appearance of additional structures on the surface of the cell membrane is observed). The labeled polymers are also tools used together with dynamic light scattering and calorimetric titration to study their interaction with other biopolymers. As for the interactions with biological membranes, lipid Langmuir monolayers as model membrane systems were used.

Studies on Antifungal Properties of Methacrylamido Propyl Trimethyl Ammonium Chloride Polycations and Their Toxicity In Vitro

The biological activity of polycations is usually associated with their biocidal properties. Their antibacterial features are well known, but in this work, observations on the antifungal properties of macromolecules obtained by methacrylamido propyl trimethyl ammonium chloride (MAPTAC) polymerization are presented. The results, not previously reported, make it possible to correlate antifungal properties directly with the structure of the macromolecule, in particular the molecular mass. The polymers described here have antifungal activity against some filamentous fungi. The strongest effect occurs for polymers with a mass of about 0.5 mDa which have confirmed activity against the multidrug-resistant species Scopulariopsis brevicaulis, Fusarium oxysporum, and Fusarium solani, as well as the dermatophytes Trichophyton mentagrophytes, Trichophyton rubrum, Trichophyton interdigitale, and Trichophyton tonsurans. In addition, this publication describes the effects of these macromolecular systems on serum and blood components and provides a preliminary assessment of toxicity on cell lines of skin-forming cells, i.e., fibroblasts and keratinocytes. Additionally, using a Franz diffusion chamber, a negligibly low transport of the active polymer through the skin was demonstrated, which is a desirable effect for externally applied antifungal drugs. IMPORTANCE Infectious diseases are a very big medical, social, and economic problem. Even before the COVID-19 pandemic, certain infections were among of the most common causes of death. The difficulties in the treatment of infectious diseases concern in particular fungal diseases, against which we have only a few classes of drugs represented by a few substances. The publication presents the preliminary results of the in vitro antifungal activity studies of four MAPTAC polymers on different fungal species and their cytotoxicity to human cells (fibroblasts and keratinocytes). The paper also compares these properties with analogous ones of two commonly used antifungal drugs, ciclopirox and terbinafine.

The methods for removal of direct oral anticoagulants and heparins to improve the monitoring of hemostasis: a narrative literature review

The assessment of hemostasis is necessary to make suitable decisions on the management of patients with thrombotic disorders. In some clinical situations, for example, during thrombophilia screening, the presence of anticoagulants in sample makes diagnosis impossible. Various elimination methods may overcome anticoagulant interference. DOAC-Stop, DOAC-Remove and DOAC Filter are available methods to remove direct oral anticoagulants in diagnostic tests, although there are still reports on their incomplete efficacy in several assays. The new antidotes for direct oral anticoagulants - idarucizumab and andexanet alfa - could be potentially useful, but have their drawbacks. The necessity to remove heparins is also arising as heparin contamination from central venous catheter or therapy with heparin disturbs the appropriate hemostasis assessment. Heparinase and polybrene are already present in commercial reagents but a fully-effective neutralizer is still a challenge for researchers, thus promising candidates remain in the research phase.

A cysteine enzyme hemostat for efficient heparin-tolerant blood coagulation

It is challenging to stop bleeding effectively in patients treated with heparin which leads to enhanced risk of uncontrolled bleeding during operation. Herein, we report an easy-to-use and heparin-tolerant hemostatic agent based on a thrombin-like cysteine enzyme (papain), which catalyzes the hydrolysis of fibrinogen and cross-linking of fibrin clots. A papain-based hemostat with increased procoagulant activity is developed through immobilizing papain on the cellulose carrier, which displays short clotting time in both normal and heparinized plasmas. The excellent hemostatic performance of the papain-based hemostat is further confirmed with reduced hemostatic time and limited blood loss in a mouse tail amputation model, rabbit auricular artery injury model and rat liver injury model, in which a natural coagulation system fails to function on account of heparin. This bio-hemostat has great potential to reverse the effect of heparin and stop topical hemorrhage rapidly in surgical procedures.

Quaternary ammonium substituted pullulan accelerates wound healing and disinfects Staphylococcus aureus infected wounds in mouse through an atypical 'non-pore forming' pathway of bacterial membrane disruption

The emergence of multi-drug resistant pathogens has fueled the search for alternatives to the existing line of antibiotics that can eradicate pathogens without inducing resistance development. Here, we report the accelerated wound healing and disinfection potential of a non-amphiphilic quaternized fungal exopolysaccharide, pullulan, without resistance generation in pathogens. The quaternary ammonium substituted pullulan (CP) derivatives showed excellent bactericidal activity against both Gram negative (MBC₉₀ = 1.5 μg mL^-1) and Gram positive (MBC₉₀ = 0.25 μg mL^-1) bacteria at very low concentrations without showing any toxicity towards mammalian cells. A combined approach of atomistic molecular dynamics simulation and experimental assays revealed that CP exerts a membrane directed bactericidal action through an atypical "non-pore forming" pathway which is not yet established for any known antibacterial polysaccharides. This involves an increase in membrane roughness, disorder among anionic lipid tails, formation of localized anionic lipid clusters and membrane depolarization, finally leading to physical disruption of the membrane integrity. Moreover, CP also displayed biofilm eradication abilities and emerged as an excellent therapeutic material for disinfection and healing of infected wounds. The present work shows the potential of exploiting polysaccharides as next-generation broad-spectrum antimicrobials and provides a platform for further development of rationally designed pullulan-based functional materials for biomedical applications.

Synthesis and Study of Antifungal Properties of New Cationic Beta-Glucan Derivatives

The interaction of positively charged polymers (polycations) with a biological membrane is considered to be the cause of the frequently observed toxicity of these macromolecules. If it is possible to obtain polymers with a predominantly negative effect on bacterial and fungal cells, such systems would have great potential in the treatment of infectious diseases, especially now when reports indicate the growing risk of fungal co-infections in COVID-19 patients. We describe in this article cationic derivatives of natural beta-glucan polymers obtained by reacting the polysaccharide isolated from Saccharomyces boulardii (SB) and Cetraria islandica (CI) with glycidyl trimethyl ammonium chloride (GTMAC). Two synthesis strategies were applied to optimize the product yield. Fungal diseases particularly affect low-income countries, hence the emphasis on the simplicity of the synthesis of such drugs so they can be produced without outside help. The three structures obtained showed selective anti-mycotic properties (against, i.e., Scopulariopsis brevicaulis, Aspergillus brasiliensis, and Fusarium solani), and their toxicity established using fibroblast 3T3-L1 cell line was negligible in a wide range of concentrations. For one of the polymers (SB derivative), using in vivo model of Aspergillus brasiliensis infection in Galleria mellonella insect model, we confirmed the promising results obtained in the preliminary study.

Growth of Lactic Acid Bacteria on Gold-Influence of Surface Roughness and Chemical Composition

The main focus of this work was to establish a correlation between surface topography and chemistry and surface colonization by lactic acid bacteria. For this reason, we chose gold substrates with different surface architectures (i.e., smooth and nanorough) that were characterized by atomic force microscopy (AFM), electron scanning microscopy (SEM), and X-ray diffractometry (XRD). Moreover, to enhance biocompatibility, we modified gold substrates with polymeric monolayers, namely cationic dextran derivatives with different molar masses. The presence of those layers was confirmed by AFM, infrared spectroscopy (IR), and X-ray photoelectron spectroscopy (XPS). In order to determine the adhesion abilities of non-modified and modified gold surfaces, we tested three lactic acid bacteria (LAB) strains (i.e., Lactobacillus rhamnosus GG, Lactobacillus acidophilus, and Lactobacillus plantarum 299v). We have shown that surface roughness influences the surface colonization of bacteria, and the most significant impact on the growth was observed for the Lactobacillus rhamnosus GG strain. What is more, covering the gold surface with a molecular polymeric film by using the layer-by-layer (LbL) method allows additional changes in the bacterial growth, independently on the used strain. The well-being of the bacteria cells on tested surfaces was confirmed by using selective staining and fluorescence microscopy. Finally, we have determined the bacterial metabolic activity by measuring the amount of produced lactic acid regarding the growth conditions. The obtained results proved that the adhesion of bacteria to the metallic surface depends on the chemistry and topography of the surface, as well as the specific bacteria strain.

Serum Albumin-Peptide Conjugates for Simultaneous Heparin Binding and Detection

Heparin is a polysaccharide-based anticoagulant agent, which is widely used in surgery and blood transfusion. However, overdosage of heparin may cause severe side effects such as bleeding and low blood platelet count. Currently, there is only one clinically licensed antidote for heparin: protamine sulfate, which is known to provoke adverse effects. In this work, we present a stable and biocompatible alternative for protamine sulfate that is based on serum albumin, which is conjugated with a variable number of heparin-binding peptides. The heparin-binding efficiency of the conjugates was evaluated with methylene blue displacement assay, dynamic light scattering, and anti-Xa assay. We found that multivalency of the peptides played a key role in the observed heparin-binding affinity and complex formation. The conjugates had low cytotoxicity and low hemolytic activity, indicating excellent biocompatibility. Furthermore, a sensitive DNA competition assay for heparin detection was developed. The detection limit of heparin was 0.1 IU/mL, which is well below its therapeutic range (0.2-0.4 IU/mL). Such biomolecule-based systems are urgently needed for next-generation biocompatible materials capable of simultaneous heparin binding and sensing.

New long-term action insulin formulations obtained using polycations for heparin neutralization

Phenomena that occur between an insulin and four different positively charged polymers (protamine, cationic dextran, chitosan, and poliallylamine derivatives) were studied by dynamic light scattering and fluorescence measurements (using fluorescein-labeled polymers). These processes were compared to the reaction of polycations with heparin that is responsible for the neutralization of anticoagulant activity in blood stream.The nature of polycations interaction with heparin is electrostatic, while the interaction with insulin is more complicated.We observed that the presence of zinc atoms (and its complexing by nitrogen from macromolecules) is critical for insulin suspensions formation and stability. The differences between the nature of these two reactions were revealed. The highly immunogenic action of protamine present in long-acting insulin products makes it reasonable to develop similar systems based on the nonprotein polycations.

Self-assembled multivalent (SAMul) ligand systems with enhanced stability in the presence of human serum

Self-assembled cationic micelles are an attractive platform for binding biologically-relevant polyanions such as heparin. This has potential applications in coagulation control, where a synthetic heparin rescue agent could be a useful replacement for protamine, which is in current clinical use. However, micelles can have low stability in human serum and unacceptable toxicity profiles. This paper reports the optimisation of self-assembled multivalent (SAMul) arrays of amphiphilic ligands to bind heparin in competitive conditions. Specifically, modification of the hydrophobic unit kinetically stabilises the self-assembled nanostructures, preventing loss of binding ability in the presence of human serum - cholesterol hydrophobic units significantly outperform systems with a simple aliphatic chain. It is demonstrated that serum albumin disrupts the binding thermodynamics of the latter system. Molecular simulation shows aliphatic lipids can more easily be removed from the self-assembled nanostructures than the cholesterol analogues. This agrees with the experimental observation that the cholesterol-based systems undergo slower disassembly and subsequent degradation via ester hydrolysis. Furthermore, by stabilising the SAMul nanostructures, toxicity towards human cells is decreased and biocompatibility enhanced, with markedly improved survival of human hepatoblastoma cells in an MTT assay.

The neutralization of heparan sulfate by heparin-binding copolymer as a potential therapeutic target

Besides regulating ligand–receptor and cell–cell interactions, heparan sulfate (HS) may participate in the development of many diseases, such as cancer, bacterial or viral infections, and their complications, like bleeding or inflammation. In these cases, the neutralization of HS could be a potential therapeutic target. The heparin-binding copolymer (HBC, PEG41-PMAPTAC53) was previously reported by us as a fully synthetic compound for efficient and safe neutralization of heparins and synthetic anticoagulants. In a search for molecular antagonists of HS, we examined the activity of HBC as an HS inhibitor both in vitro and in vivo and characterized HBC/HS complexes. Using a colorimetric Azure A method, isothermal titration calorimetry and dynamic light scattering techniques we found that HBC binds HS by forming complexes below 200 nm with less than 1 : 1 stoichiometry. We confirmed the HBC inhibitory effect in rats by measuring activated partial thromboplastin time, prothrombin time, anti-factor Xa activity, anti-factor IIa activity, and platelet aggregation. HBC reversed the enhancement of all tested parameters caused by HS demonstrating that cationic synthetic block copolymers may have a therapeutic value in various disorders involving overproduction of HS.

The neutralization of heparan sulfate (HS) by a heparin-binding copolymer (HBC) could be a promising treating option for bacterial or viral infections or bleeding related to overproduction of HS in cancer or other diseases.

Approaches to prevent bleeding associated with anticoagulants: current status and recent developments

Anticoagulants are widely used for the prophylaxis and treatment of cardiovascular disorders and to prevent blood clotting during surgeries. However, the major limitation associated with anticoagulant therapy is bleeding; all the current anticoagulants do have a bleeding risk. The propensity to bleed is much higher among the elderly population and patients with renal insufficiency. Therefore, there is an utmost and urgent clinical need for a highly efficient, nontoxic antidote with excellent anticoagulant reversal activity. This will significantly improve the safety of anticoagulation therapy. This review summarizes the current options and approaches to reverse anticoagulation activity of clinically used anticoagulants. We start with an introduction to thrombosis and then summarize the details of current clinically available anticoagulants and their mechanisms of action and limitations. This is followed by current practices in anticoagulant neutralization including the details of the only clinically approved unfractionated heparin antidote, protamine; recent advances in the development of antidotes against heparin-based drugs; and direct oral anticoagulants (DOACs).

Significant role of cationic polymers in drug delivery systems

Cationic polymers are characterized as the macromolecules that possess positive charges, which can be either inherently in the polymer side chains and/or its backbone. Based on their origins, cationic polymers are divided in two category including natural and synthetic, in which the possessed positive charges are as result of primary, secondary or tertiary amine functional groups that could be protonated in particular situations. Cationic polymers have been employed commonly as drug delivery agents due to their superior encapsulation efficacy, enhanced bioavailability, low toxicity and improved release profile. In this paper, we focus on the most prominent examples of cationic polymers which have been revealed to be applicable in drug delivery systems and we also discuss their general synthesis and surface modification methods as well as their controlled release profile in drug delivery.

Heparin-binding copolymer reverses effects of unfractionated heparin, enoxaparin, and fondaparinux in rats and mice

The parenteral anticoagulants may cause uncontrolled and life-threatening bleeding. Protamine, the only registered heparin antidote, is partially effective against low-molecular weight heparins, completely ineffective against fondaparinux and may cause unacceptable toxicity. Therefore, we aimed to develop a synthetic compound for safe and efficient neutralization of all parenteral anticoagulants. We synthesized pegylated PMAPTAC block copolymers, and then, we selected a lead heparin-binding copolymer (HBC). We assessed the effectiveness of HBC in the model of arterial thrombosis electrically induced in the carotid artery of rats by measuring thrombus weight, bleeding time, activated partial thromboplastin time, activated clotting time, and anti-factor Xa activity. The intravital tissue distribution, the cardiorespiratory, and organ toxicity were monitored. HBC diminished antithrombotic and anticoagulant effects of unfractionated heparin. Moreover, it stopped bleeding and completely reversed the enhancement of clotting times and anti-factor Xa activity caused by enoxaparin or fondaparinux. We observed slight pulmonary congestion and cell infiltration, but the cardiorespiratory parameters remained unchanged. We found a strong signal of fluorescently-labeled HBC in the urine, and a weaker in the liver and in the kidney. No signs of hepatic or nephrotoxicity were observed in the blood biochemistry or histopathologic examination. We developed a copolymer efficiently neutralizing effects of heparins in the living organism, which shows a very promising efficacy/safety profile and may help in the management of uncontrolled bleeding resulting from an anticoagulant injection. HBC could enable the safe replacement of unfractionated heparin with low-molecular weight heparins in patients undergoing cardiac surgery and complex vascular procedures.

The Toxicokinetic Profile of Dex40-GTMAC3-a Novel Polysaccharide Candidate for Reversal of Unfractionated Heparin

Though protamine sulfate is the only approved antidote of unfractionated heparin (UFH), yet may produce life threatening side effects such as systemic hypotension, catastrophic pulmonary vasoconstriction or allergic reactions. We have described 40 kDa dextrans (Dex40) substituted with glycidyltrimethylammonium chloride (GTMAC) as effective, immunogenically and hemodynamically neutral inhibitors of UFH. The aim of the present study was to evaluate in mice and rats toxicokinetic profile of the most promising polymer—Dex40-GTMAC3. Polymer was rapidly eliminated with a half-time of 12.5 ± 3.0 min in Wistar rats, and was mainly distributed to the kidneys and liver in mice. The safety studies included the measurement of blood count and blood biochemistry, erythrocyte osmotic fragility and the evaluation of the histological alterations in kidneys, liver and lungs of mice and rats in acute and chronic experiments. We found that Dex40-GTMAC3 is not only effective but also very well tolerated. Additionally, we found that protamine may cause overt hemolysis with appearance of permanent changes in the liver and kidneys. In summary, fast renal clearance behavior and generally low tissue accumulation of Dex40-GTMAC3 is likely to contribute to its superior to protamine biocompatibility. Intravenous administration of therapeutic doses to living animals does not result in the immunogenic, hemodynamic, blood, and organ toxicity. Dex40-GTMAC3 seems to be a promising effective and safe candidate for further clinical development as new UFH reversal agent.

Nonclinical evaluation of novel cationically modified polysaccharide antidotes for unfractionated heparin

Protamine, the only registered antidote of unfractionated heparin (UFH), may produce a number of adverse effects, such as anaphylactic shock or serious hypotension. We aimed to develop an alternative UFH antidote as efficient as protamine, but safer and easier to produce. As a starting material, we have chosen generally non-toxic, biocompatible, widely available, inexpensive, and easy to functionalize polysaccharides. Our approach was to synthesize, purify and characterize cationic derivatives of dextran, hydroxypropylcellulose, pullulan and γ-cyclodextrin, then to screen them for potential heparin-reversal activity using an in vitro assay and finally examine efficacy and safety of the most active polymers in Wistar rat and BALB/c mouse models of experimentally induced arterial and venous thrombosis. Efficacy studies included the measurement of thrombus formation, activated partial thromboplastin time, bleeding time, and anti-factor Xa activity; safety studies included the measurement of hemodynamic, hematologic and immunologic parameters. Linear, high molecular weight dextran substituted with glycidyltrimethylammonium chloride groups at a ratio of 0.65 per glucose unit (Dex40-GTMAC3) is the most potent and the safest UFH inhibitor showing activity comparable to that of protamine while possessing lower immunogenicity. Cationic polysaccharides of various structures neutralize UFH. Dex40-GTMAC3 is a promising and potentially better UFH antidote than protamine.

Affinity-based design of a synthetic universal reversal agent for heparin anticoagulants

Heparin-based anticoagulant drugs have been widely used for the prevention of blood clotting during surgical procedures and for the treatment of thromboembolic events. However, bleeding risks associated with these anticoagulants demand continuous monitoring and neutralization with suitable antidotes. Protamine, the only clinically approved antidote to heparin, has shown adverse effects and ineffectiveness against low-molecular weight heparins and fondaparinux, a heparin-related medication. Alternative approaches based on cationic molecules and recombinant proteins have several drawbacks including limited efficacy, toxicity, immunogenicity, and high cost. Thus, there is an unmet clinical need for safer, rapid, predictable, and cost-effective anticoagulant-reversal agents for all clinically used heparins. We report a design strategy for a fully synthetic dendritic polymer-based universal heparin reversal agent (UHRA) that makes use of multivalent presentation of branched cationic heparin binding groups (HBGs). Optimization of the UHRA design was aided by isothermal titration calorimetry studies, biocompatibility evaluation, and heparin neutralization analysis. By controlling the scaffold's molecular weight, the nature of the protective shell, and the presentation of HBGs on the polymer scaffold, we arrived at lead UHRA molecules that completely neutralized the activity of all clinically used heparins. The optimized UHRA molecules demonstrated superior efficacy and safety profiles and mitigated heparin-induced bleeding in animal models. This new polymer therapeutic may benefit patients undergoing high-risk surgical procedures and has potential for the treatment of anticoagulant-related bleeding problems.

Chemically modified poly(2-hydroxyethyl methacrylate) cryogel for the adsorption of heparin

Various clinical procedures, such as cardiovascular surgery or extracorporeal blood purification, involve systemic anticoagulation using heparin. High concentrations of circulating heparin require neutralization due to possible serious bleeding complications. The intravenous administration of the heparin antagonist protamine sulfate is routinely clinically performed, but is frequently associated with adverse reactions. Therefore, there is a need for a valid and safe alternative to achieve extracorporeal heparin removal from blood or plasma, such as a filter, a matrix, or an adsorbent. Here, we describe the development of a macroporous poly(2-hydroxyethyl methacrylate)-based monolithic cryogel functionalized with l-lysine (pHEMA-lys) and the characterization of its selective heparin adsorption. The maximum binding capacity was quantified in vitro using aqueous and serum solutions under static and dynamic conditions, and fresh human plasma under static conditions. The pHEMA-lys bound 40,500 IU and 32,500 IU heparin/g cryogel at the equilibrium in aqueous solution and 50% serum, respectively. In human plasma spiked with 100 IU/mL of heparin, the binding was still highly efficient (4330 IU/g cryogel after 30 min, i.e., 87% of the initial concentration). The cryogels showed good blood compatibility, as indicated by negligible adsorption of albumin, antithrombin III, and total protein, and may thus be suitable for extracorporeal heparin removal.

Cationic polymers and their therapeutic potential

The last decade has witnessed enormous research focused on cationic polymers. Cationic polymers are the subject of intense research as non-viral gene delivery systems, due to their flexible properties, facile synthesis, robustness and proven gene delivery efficiency. Here, we review the most recent scientific advances in cationic polymers and their derivatives not only for gene delivery purposes but also for various alternative therapeutic applications. An overview of the synthesis and preparation of cationic polymers is provided along with their inherent bioactive and intrinsic therapeutic potential. In addition, cationic polymer based biomedical materials are covered. Major progress in the fields of drug and gene delivery as well as tissue engineering applications is summarized in the present review.