Chitosan derivatives as novel potential heparin reversal agents

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.

New N-Methylimidazole-Functionalized Chitosan Derivatives: Hemocompatibility and Antibacterial Properties

Novel imidazole derivatives of the low molecular weight chitosan N-(2-hydroxypropyl)-1H-1,2,3-triazol-4-yl)methyl)-1-methyl-1H-imidazol-3-ium chitosan chloride (NMIC) were synthesized using copper-catalyzed azide-alkyne cycloaddition (CuAAC). The degrees of substitution (DSs) for the new derivatives were 18-76%. All chitosan derivatives (2000 µg/mL) were completely soluble in water. The antimicrobial activity of the new compounds against E. coli and S. epidermidis was studied. The effect of chitosan derivatives on blood and its components was studied. NMIC samples (DS 34-76%) at a concentration <10 μg/mL had no effect on blood and plasma coagulation. Chitosan derivatives (DS 18-76%) at concentrations of ≥83 μg/mL in blood and ≥116.3 μg/mL in plasma resulted in a prolongation of the clotting time of blood and plasma, positively related to the DS. At concentrations up to 9.1 μg/mL, NMIC did not independently provoke platelet aggregation. The degree of erythrocyte hemolysis upon contact with NMIC samples (2.5-2500 μg/mL) was below 4%. The inhibition of blood/plasma coagulation indicates the promising use of the studied samples to modify the surface of medical materials in order to achieve thromboresistance.

Marine-origin polysaccharides-based free-standing multilayered membranes as sustainable nanoreservoirs for controlled drug delivery

The layer-by-layer (LbL) assembly technology has been widely used to functionalise surfaces and precisely engineer robust multilayered bioarchitectures with tunable structures, compositions, properties, and functions at the nanoscale by resorting to a myriad of building blocks exhibiting complementary interactions. Among them, marine-origin polysaccharides are a sustainable renewable resource for the fabrication of nanostructured biomaterials for biomedical applications owing to their wide bioavailability, biocompatibility, biodegradability, non-cytotoxicity, and non-immunogenic properties. Chitosan (CHT) and alginate (ALG) have been widely employed as LbL ingredients to shape a wide repertoire of size- and shape-tunable electrostatic-driven multilayered assemblies by exploring their opposite charge nature. However, the insolubility of CHT in physiological conditions intrinsically limits the range of bioapplications of the as-developed CHT-based LbL structures. Herein, we report the preparation of free-standing (FS) multilayered membranes made of water-soluble quaternised CHT and ALG biopolymers for controlled release of model drug molecules. The influence of the film structure in the drug release rate is studied by assembling two distinct set-ups of FS membranes, having the model hydrophilic drug fluorescein isothiocyanate-labelled bovine serum albumin (FITC-BSA) either as an intrinsic building block or added as an outer layer after the LbL assembly process. Both FS membranes are characterised for their thickness, morphology, in vitro cytocompatibility, and release profile, with those having FITC-BSA as an intrinsic LbL ingredient denoting a more sustained release rate. This work opens up new avenues for the design and development of a wide array of CHT-based devices for biomedical applications, overcoming the limitations associated with the insolubility of native CHT under physiological conditions.

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 Synthetic Protocell-Based Heparin Scavenger

Heparin is a commonly applied blood anticoagulant agent in clinical use. After treatment, excess heparin needs to be removed to circumvent side effects and recover the blood-clotting cascade. Most existing heparin antidotes rely on direct heparin binding and complexation, yet selective compartmentalization and sequestration of heparin would be beneficial for safety and efficiency. However, such systems have remained elusive. Herein, a semipermeable protein-based microcompartment (proteinosome) is loaded with a highly positively charged chitosan derivative, which can induce electrostatics-driven internalization of anionic guest molecules inside the compartment. Chitosan-loaded proteinosomes are subsequently employed to capture heparin, and an excellent heparin-scavenging performance is demonstrated under physiologically relevant conditions. Both the highly positive scavenger and the polyelectrolyte complex are confined and shielded by the protein compartment in a time-dependent manner. Moreover, selective heparin-scavenging behavior over serum albumin is realized through adjusting the localized scavenger or surrounding salt concentrations at application-relevant circumstances. In vitro studies reveal that the cytotoxicity of the cationic scavenger and the produced polyelectrolyte complex is reduced by protocell shielding. Therefore, the proteinosome-based systems may present a novel polyelectrolyte-scavenging method for biomedical applications.

Biological Properties of Heparins Modified with an Arylazopyrazole-Based Photoswitch

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

Biomass-Derived Plant Extracts in Macromolecular Chitosan Matrices as a Green Coating for PLA Films

Due to the growing problem of food and packaging waste, environmental awareness, and customer requirements for food safety, there is a great need for the development of innovative and functional packaging. Among these developments, the concept of active packaging is at the forefront. The shortcoming in this area is that there is still a lack of multifunctional concepts, as well as green approaches. Therefore, this work focuses on the development of active chemical substances of natural origin applied as a coating on polylactic acid (PLA) films. Biopolymer chitosan and plant extracts rich in phenolic compounds (blackberry leaves-Rubus fruticosus, needles of prickly juniper-Juniperus oxycedrus) obtained from plant biomass from Southeastern Europe were selected in this work. In order to increase the effectiveness of individual substances and to introduce multifunctionality, they were combined in the form of different colloidal structural formulations. The plant extracts were embedded in chitosan biopolymer particles and dispersed in a macromolecular chitosan solution. In addition, a two-layer coating, the first of a macromolecular chitosan solution, and the second of a dispersion of the embedded extracts in chitosan particles, was applied to the PLA films as a novel approach. The success of the coatings was monitored by X-ray photoelectron spectroscopy (XPS) and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), and the wettability was evaluated by contact angle measurements. Scanning electron microscopy SEM tracked the morphology and homogeneity of the coating. Antioxidation was studied by DPPH and ABTS spectrophotometric tests, and microbiological analysis of the films was performed according to the ISO 22196 Standard. Desorption of the coating from the PLA was monitored by reducing the elemental composition of the films themselves. The successful functionalization of PLA was demonstrated, while the XPS and ATR-FTIR analyses clearly showed the peaks of elemental composition of the extracts and chitosan on the PLA surface. Moreover, in all cases, the contact angle of the bilayer coatings decreased by more than 35-60% and contributed to the anti-fogging properties. The desorption experiments, due to decrease in the concentration of the specific typical element (nitrogen), indicated some migration of substances from the PLA's surface. The newly developed films also exhibited antioxidant properties, with antioxidant ABTS efficiencies ranging from 83.5 to 100% and a quite high inhibition of Gram-positive Staphylococcus aureus bacteria, averaging over 95%. The current functionalization of PLA simultaneously confers antifogging, antioxidant, and antimicrobial properties and drives the development of a biodegradable and environmentally friendly composite material using green chemistry principles.

First Insights into the Antiviral Activity of Chitosan-Based Bioactive Polymers towards the Bacteriophage Phi6: Physicochemical Characterization, Inactivation Potential, and Inhibitory Mechanisms

The outbreak of the worrisome coronavirus disease in 2019 has caused great concern among the global public, especially regarding the need for personal protective equipment with applied antiviral agents to reduce the spread and transmission of the virus. Thus, in our research, chitosan-based bioactive polymers as potential antiviral agents were first evaluated as colloidal macromolecular solutions by elemental analysis and charge. Three different types of low and high molecular weight chitosan (LMW Ch, HMW Ch) and a LMW Ch derivative, i.e., quaternary chitosan (quart-LMW Ch), were used. To explore their antiviral activity for subsequent use in the form of coatings, the macromolecular Chs dispersions were incubated with the model virus phi6 (surrogate for SARS-CoV-2), and the success of virus inactivation was determined. Inactivation of phi6 with some chitosan-based compounds was very successful (>6 log), and the mechanisms behind this were explored. The changes in viral morphology after incubation were observed and the changes in infrared bands position were determined. In addition, dynamic and electrophoretic light scattering studies were performed to better understand the interaction between Chs and phi6. The results allowed us to better understand the antiviral mode of action of Chs agents as a function of their physicochemical properties.

Polymeric Materials as Potential Inhibitors Against SARS-CoV-2

Recently discovered SARS-CoV-2 caused a pandemic that triggered researchers worldwide to focus their research on all aspects of this new peril to humanity. However, in the absence of specific therapeutic intervention, some preventive strategies and supportive treatment minimize the viral transmission as studied by some factors such as basic reproduction number, case fatality rate, and incubation period in the epidemiology of viral diseases. This review briefly discusses coronaviruses' life cycle of SARS-CoV-2 in a human host cell and preventive strategies at some selected source of infection. The antiviral activities of synthetic and natural polymers such as chitosan, hydrophobically modified chitosan, galactosylated chitosan, amine-based dendrimers, cyclodextrin, carrageenans, polyethyleneimine, nanoparticles are highlighted in this article. Mechanism of virus inhibition, detection and diagnosis are also presented. It also suggests that polymeric materials and nanoparticles can be effective as potential inhibitors and immunization against coronaviruses which would further develop new technologies in the field of polymer and nanoscience.

Biological Synergy and Antimicrobial Mechanism of Hydroxypropyltrimethyl Ammonium Chloride Chitosan with Benzalkonium Chloride

Preservatives in eye drops have always been the focus of people's attention. Benzalkonium chloride (BAC) is one of the most frequently used bacteriostatic agents in eye drops, which has broad-spectrum and efficient bactericidal ability. However, the inappropriate dosage of BAC may lead to high cytotoxicity. Therefore, adding low-toxic hydroxypropyltrimethyl ammonium chloride chitosan (HACC) can not only achieve antimicrobial effect, but also have the advantages of moisturizing and biocompatibility. In this paper, the minimum inhibitory concentrations (MICs) of HACC and BAC were evaluated against Escherichia coli, Staphylococcus aureus, Staphylococcus epidermidis, Diphtheroid bacillus and Candida albicans. Based on the MIC of each antimicrobial agent, an antimicrobial assay was performed to investigate the antimicrobial ability of disinfectant solution. Besides, cytotoxicity had also been assessed. When the HACC/BAC solution at weight ratio of 150/1 showed a highest antimicrobial efficiency and the cell proliferation rates were the highest in 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays. Furthermore, the cell leakage was examined by UV absorption, indicating the great synergistic antimicrobial effect between HACC and BAC. What is more, the results of micromorphology research suggested that as the result of repulsive force between the two molecules, the average particle size of HACC would decrease. Finally, the impedance experiment showed that with the addition of BAC, current density would increase significantly, suggesting that more positive charge group was exposed to aqueous solution, leading the the increase of antimicrobial ability. Based on these results, HACC-BAC combination solution might be a promising novel antimicrobial group for biomedical applications.

Polymeric approach to combat drug-resistant methicillin-resistant Staphylococcus aureus

ABSTRACT

The current global death rate has threatened humans due to increase in deadly unknown infections caused by pathogenic microorganisms. On the contrary, the emergence of multidrug-resistant bacteria is also increasing which is leading to elevated lethality rate worldwide. Development of drug-resistant bacteria has become one of the daunting global challenges due to failure in approaching to combat against them. Methicillin-resistant Staphylococcus aureus (MRSA) is one of those drug-resistant bacteria which has led to increase in global mortality rate causing various lethal infections. Polymer synthesis can be one of the significant approaches to combat MRSA by fabricating polymeric coatings to prevent the spread of infections. This review provides last decade information in the development of various polymers against MRSA.

GRAPHICAL ABSTRACT

An Overview of Current Knowledge on the Properties, Synthesis and Applications of Quaternary Chitosan Derivatives

Chitosan, a chitin-derivative polysaccharide, known for its non-toxicity, biocompatibility and biodegradability, presents limited applications due to its low solubility in neutral or basic pH medium. Quaternization stands out as an alternative to modify this natural polymer, aiming to improve its solubility over a wide pH range and, consequently, expand its range of applications. Quaternization occurs by introducing a quaternary ammonium moiety onto or outside the chitosan backbone, via chemical reactions with primary amino and hydroxyl groups, under vast experimental conditions. The oldest and most common forms of quaternized chitosan involve N,N,N-trimethyl chitosan (TMC) and N-[(2-hydroxy-3-trimethyl ammonium) propyl] chitosan (HTCC) and, more recently, quaternized chitosan by insertion of pyridinium or phosphonium salts. By modifying chitosan through the insertion of a quaternary moiety, permanent cationic charges on the polysaccharide backbone are achieved and properties such as water solubility, antimicrobial activity, mucoadhesiveness and permeability are significantly improved, enabling the application mainly in the biomedical and pharmaceutical areas. In this review, the main quaternized chitosan compounds are addressed in terms of their structure, properties, synthesis routes and applications. In addition, other less explored compounds are also presented, involving the main findings and future prospects regarding the field of quaternized chitosans.

Gradient Chitosan Hydrogels Modified with Graphene Derivatives and Hydroxyapatite: Physiochemical Properties and Initial Cytocompatibility Evaluation

In this study, we investigated preparation of gradient chitosan-matrix hydrogels through a novel freezing-gelling-thawing method. The influence of three types of graphene family materials (GFM), i.e., graphene oxide (GO), reduced graphene oxide (rGO), and poly(ethylene glycol) grafted graphene oxide (GO-PEG), as well as hydroxyapatite (HAp) on the physicochemical and biological properties of the composite hydrogels was examined in view of their potential applicability as tissue engineering scaffolds. The substrates and the hydrogel samples were thoroughly characterized by X-ray photoelectron spectroscopy, X-ray diffractometry, infrared spectroscopy, digital and scanning electron microscopy, rheological and mechanical analysis, in vitro chemical stability and bioactivity assays, as well as initial cytocompatibility evaluation with human umbilical cord Wharton's jelly mesenchymal stem cells (hUC-MSCs). We followed the green-chemistry approach and avoided toxic cross-linking agents, using instead specific interactions of our polymer matrix with tannic acid, non-toxic physical cross-linker, and graphene derivatives. It was shown that the most promising are the gradient hydrogels modified with GO-PEG and HAp.

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.

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).

Synthesis of inulin derivatives with quaternary phosphonium salts and their antifungal activity

Inulin is a kind of renewable and biodegradable carbohydrate with good water solubility and numerous physiological functions. For further utilization of inulin, chemical modification can be applied to improve its bioactivities. In this paper, five novel inulin derivatives were synthesized via chemical modification with quaternary phosphonium salt. Their antifungal activity against three kinds of plant pathogens including Colletotrichum lagenarium, Phomopsis asparagi, and Fusarium oxysporum was assessed with radial growth assay in vitro. Results revealed that all the inulin derivatives exhibited improved antifungal activity compared with inulin. Particularly, inulin modified with triphenylphosphine (TPhPAIL) exhibited the best antifungal activity with inhibitory indices of 80.0%, 78.8%, and 87.4% against Colletotrichum lagenarium, Phomopsis asparagi, and Fusarium oxysporum at 1.0mg/mL respectively. The results clearly showed that chemical modification of inulin with quaternary phosphonium salt could efficiently improve derivatives' antifungal activity. Further analysis of results indicated that the antifungal activity was influenced by alkyl chain length or electron-withdrawing ability of the grafted quaternary phosphonium salts. Longer alkyl chain lengths or the stronger electron-withdrawing groups would lead to enhanced antifungal efficacy.

N-(2-hydroxy) propyl-3-trimethylammonium chitosan chloride: An immune-enhancing adjuvant for hepatitis E virus recombinant polypeptide vaccine in mice

Adjuvants are essential for enhancing vaccine potency by improving the humoral and/or cell-mediated immune response to vaccine antigens. This study was performed to evaluate the immuno-enhancing characteristic of N-(2-hydroxy) propyl-3-trimethylammonium chitosan chloride (HTCC), the cationically modified chitosan, as an adjuvant for hepatitis E virus (HEV) recombinant polypeptide vaccine. Animal experiments showed that HTCC provides adjuvant activity when co-administered with HEV recombinant polypeptide vaccine by intramuscularly route. Vaccination using HTCC as an adjuvant was associated with increases of the serum HEV-specific IgG antibodies, splenocytes proliferation and the growths of CD4⁺CD8^- T lymphocytes and IFN-γ-secreting T lymphocytes in peripheral blood. These findings suggested that HTCC had strong immuno-enhancing effect. Our findings are the first to demonstrate that HTCC is safe and effective in inducing a good antibody response and stimulating Th1-biased immune responses for HEV recombinant polypeptide vaccine.

Biopolymeric nano/microspheres for selective and reversible adsorption of coronaviruses

A novel biopolymeric material in the form of nano/microspheres was developed which was capable of adsorbing coronaviruses. The biopolymer was obtained by crosslinking of chitosan (CHIT) with genipin, a nontoxic compound of plant origin, in inverted emulsion and reacting the chitosan nano/microspheres obtained (CHIT-NS/MS) with glycidyltrimethyl-ammonium chloride (GTMAC). As a result the nano/microspheres of N-(2-hydroxypropyl)-3-trimethyl chitosan (HTCC-NS/MS) were obtained. HTCC-NS/MS were studied as the adsorbents of human coronavirus NL63 (HCoV-NL63), mouse hepatitis virus (MHV), and human coronavirus HCoV-OC43 particles in aqueous virus suspensions. By studying cytopathic effect (CPE) caused by these viruses and performing PCR analyses it was found HTCC-NS/MS strongly adsorb the particles of HCoV-NL63 virus, moderately adsorb mouse hepatitis virus (MHV) particles, but do not adsorb HCoV-OC43 coronavirus. The adsorption capacity of HTCC-NS/MS well correlated with the antiviral activity of soluble HTCC against a given virus. Importantly, it was shown that HCoV-NL63 particles could be desorbed from the HTCC-NS/MS surface with a salt solution of high ionic strength with retention of virus virulence. The obtained material may be applied for the removal of coronaviruses, purification and concentration of virus samples obtained from biological matrices and for purification of water from pathogenic coronaviruses.

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.

Chitosan Derivatives Active against Multidrug-Resistant Bacteria and Pathogenic Fungi: In Vivo Evaluation as Topical Antimicrobials

The continuous rise of antimicrobial resistance and the dearth of new antibiotics in the clinical pipeline raise an urgent call for the development of potent antimicrobial agents. Cationic chitosan derivatives, N-(2-hydroxypropyl)-3-trimethylammonium chitosan chlorides (HTCC), have been widely studied as potent antibacterial agents. However, their systemic structure-activity relationship, activity toward drug-resistant bacteria and fungi, and mode of action are very rare. Moreover, toxicity and efficacy of these polymers under in vivo conditions are yet to be established. Herein, we investigated antibacterial and antifungal efficacies of the HTCC polymers against multidrug resistant bacteria including clinical isolates and pathogenic fungi, studied their mechanism of action, and evaluated cytotoxic and antimicrobial activities in vitro and in vivo. The polymers were found to be active against both bacteria and fungi (MIC = 125-250 μg/mL) and displayed rapid microbicidal kinetics, killing pathogens within 60-120 min. Moreover, the polymers were shown to target both bacterial and fungal cell membrane leading to membrane disruption and found to be effective in hindering bacterial resistance development. Importantly, very low toxicity toward human erythrocytes (HC₅₀ = >10000 μg/mL) and embryo kidney cells were observed for the cationic polymers in vitro. Further, no inflammation toward skin tissue was observed in vivo for the most active polymer even at 200 mg/kg when applied on the mice skin. In a murine model of superficial skin infection, the polymer showed significant reduction of methicillin-resistant Staphylococcus aureus (MRSA) burden (3.2 log MRSA reduction at 100 mg/kg) with no to minimal inflammation. Taken together, these selectively active polymers show promise to be used as potent antimicrobial agents in topical and other infections.

Effective Enhancement of Hypoglycemic Effect of Insulin by Liver-Targeted Nanoparticles Containing Cholic Acid-Modified Chitosan Derivative

Liver is responsible for the balance of blood glucose level. In this study, cholic acid and N-(2-hydroxy)-propyl-3-trimethylammonium chloride modified chitosan (HTCC-CA) was used as a liver-targeted vehicle for insulin delivery. A novel approach was developed to effectively load insulin by mixing insulin and HTCC-CA in 50% ethanol and water mixed solvent at pH 2 and then dialysis against pH 7.4 phosphate buffer subsequently against water. The insulin-loaded HTCC-CA nanoparticles have an average diameter of 86 nm and insulin loading efficiency of 98.7%. Due to random distribution of the hydrophobic cholic acid groups in HTCC-CA, some of the cholic acid groups located on the nanoparticle surface. Compared with free insulin, the nanoparticles increased in vitro cellular uptake of insulin to 466%, and the nanoparticles accumulated in liver for more time after subcutaneous injection into mice. The therapy for diabetic rats displayed that the nanoparticles increased the pharmacological bioavailability of insulin to 475% relative to free insulin, and the nanoparticles could maintain the hypoglycemic effect for more than 24 h. This study demonstrates that the nanoparticles with cholic acid groups on their surface possess liver-targeted property and biocompatible insulin-loaded HTCC-CA nanoparticles can effectively enhance the hypoglycemic effect of insulin.

HTCC: Broad Range Inhibitor of Coronavirus Entry

To date, six human coronaviruses have been known, all of which are associated with respiratory infections in humans. With the exception of the highly pathogenic SARS and MERS coronaviruses, human coronaviruses (HCoV-NL63, HCoV-OC43, HCoV-229E, and HCoV-HKU1) circulate worldwide and typically cause the common cold. In most cases, infection with these viruses does not lead to severe disease, although acute infections in infants, the elderly, and immunocompromised patients may progress to severe disease requiring hospitalization. Importantly, no drugs against human coronaviruses exist, and only supportive therapy is available. Previously, we proposed the cationically modified chitosan, N-(2-hydroxypropyl)-3-trimethylammonium chitosan chloride (HTCC), and its hydrophobically-modified derivative (HM-HTCC) as potent inhibitors of the coronavirus HCoV-NL63. Here, we show that HTCC inhibits interaction of a virus with its receptor and thus blocks the entry. Further, we demonstrate that HTCC polymers with different degrees of substitution act as effective inhibitors of all low-pathogenic human coronaviruses.

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.

Chitosan-based mucosal adjuvants: Sunrise on the ocean

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Metabolism and safety profile of chitosan and its derivatives on mucosal application.

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Mechanisms of chitosan as potent mucosal adjuvant.

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Different types and forms of chitosan in pre-clinical applications.

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Clinical perspectives.

Mucosal vaccination, which is shown to elicit systemic and mucosal immune responses, serves as a non-invasive and convenient alternative to parenteral administration, with stronger capability in combatting diseases at the site of entry. The exploration of potent mucosal adjuvants is emerging as a significant area, based on the continued necessity to amplify the immune responses to a wide array of antigens that are poorly immunogenic at the mucosal sites. As one of the inspirations from the ocean, chitosan-based mucosal adjuvants have been developed with unique advantages, such as, ability of mucosal adhesion, distinct trait of opening the junctions to allow the paracellular transport of antigen, good tolerability and biocompatibility, which guaranteed the great potential in capitalizing on their application in human clinical trials. In this review, the state of art of chitosan and its derivatives as mucosal adjuvants, including thermo-sensitive chitosan system as mucosal adjuvant that were newly developed by author's group, was described, as well as the clinical application perspective. After a brief introduction of mucosal adjuvants, chitosan and its derivatives as robust immune potentiator were discussed in detail and depth, in regard to the metabolism, safety profile, mode of actions and preclinical and clinical applications, which may shed light on the massive clinical application of chitosan as mucosal adjuvant.

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.

Enhanced delivery of daidzein into fibroblasts and neuronal cells with cationic derivatives of gamma-cyclodextrin for the control of cellular glycosaminoglycans

Two cationic derivatives of γ-cyclodextrin (GCD) were synthesized by functionalization with glycidyltrimethylammonium chloride (GTMAC) and ethylenediamine (EDA). Both these derivatives (GCD-GTMAC and GCD-EDA) have been shown to interact strongly with anionic biopolymers, unfractionated heparin (UFH) and mucin, the latter showing their mucoadhesive properties. They form inclusion complexes with daidzein (DAI), an isoflavone displaying a multitude of physiological effects, much more efficiently than the unmodified GCD. It was also shown that the complexes of these GCD derivatives with DAI and Nile Red penetrate human fibroblasts and murine hippocampal neuronal cells indicating that cationic GCD derivatives can be considered as potential delivery systems for isoflavones and other poorly water soluble compounds. Moreover, it was found that DAI delivered in cationic GCD complexes decreased the level of the cellular glycosaminoglycans (GAGs) in normal fibroblasts suggesting their possible application in the control of GAGs in mucopolysaccharidoses, lysosomal storage diseases caused by pathological accumulation of GAGs in the cells.

Inactivation of heparin by cationically modified chitosan

This study was performed to evaluate the ability of N-(2-hydroxypropyl)-3-tri methylammonium chitosan chloride (HTCC), the cationically modified chitosan, to form biologically inactive complexes with unfractionated heparin and thereby blocking its anticoagulant activity. Experiments were carried out in rats in vivo and in vitro using the activated partial thromboplastin time (APTT) and prothrombin time (PT) tests for evaluation of heparin anticoagulant activity. For the first time we have found that HTCC effectively neutralizes anticoagulant action of heparin in rat blood in vitro as well as in rats in vivo. The effect of HTCC on suppression of heparin activity is dose-dependent and its efficacy can be comparable to that of protamine-the only agent used in clinic for heparin neutralization. HTCC administered i.v. alone had no direct effect on any of the coagulation tests used. The potential adverse effects of HTCC were further explored using rat experimental model of acute toxicity. When administered i.p. at high doses (250 and 500 mg/kg body weight), HTCC induced some significant dose-dependent structural abnormalities in the liver. However, when HTCC was administered at low doses, comparable to those used for neutralization of anticoagulant effect of heparin, no histopathological abnormalities in liver were observed.

Novel polymeric inhibitors of HCoV-NL63

The human coronavirus NL63 is generally classified as a common cold pathogen, though the infection may also result in severe lower respiratory tract diseases, especially in children, patients with underlying disease, and elderly. It has been previously shown that HCoV-NL63 is also one of the most important causes of croup in children. In the current manuscript we developed a set of polymer-based compounds showing prominent anticoronaviral activity. Polymers have been recently considered as promising alternatives to small molecule inhibitors, due to their intrinsic antimicrobial properties and ability to serve as matrices for antimicrobial compounds. Most of the antimicrobial polymers show antibacterial properties, while those with antiviral activity are much less frequent. A cationically modified chitosan derivative, N-(2-hydroxypropyl)-3-trimethylammonium chitosan chloride (HTCC), and hydrophobically-modified HTCC were shown to be potent inhibitors of HCoV-NL63 replication. Furthermore, both compounds showed prominent activity against murine hepatitis virus, suggesting broader anticoronaviral activity.

Eudragit E100 as a drug carrier: the remarkable affinity of phosphate ester for dimethylamine

Therapeutic agents containing phosphate groups in their molecules have increasing therapeutic impact. The object of this study was to characterize the cationic polyelectrolyte Eudragit E100 (EuE100) as a carrier for drugs containing phosphate groups, using dexamethasone phosphate (DP) as a model. A series of EuE100-DP complexes was obtained by acid-base reaction in which DP neutralized 12.5-75% of the basic groups of EuE100. The solids obtained after solvent evaporation revealed by spectroscopic characterization the complete reaction between the components through the ionic interaction between the amine groups of EuE100 and the phosphate groups of DP. The reversibility of the counterion condensation, evaluated through the proton-withdrawing effect produced by the ionic exchange generated by titration with NaCl, showed a remarkable high affinity between EuE100 and DP. In line, drug delivery in bicompartimental Franz cells toward water as receptor medium was very slow (2% in 6 h). However, it was increased as water was replaced by NaCl solution, which upon diffusion generates ionic exchange. A sustained release of DP with noticeable zero order kinetics accounted for a remarkable high affinity, mainly due to the electrostatic attraction. The release rate remains constant regardless of the saline concentration of the media. Besides, the delivery control is maintained even in gastric simulated fluid, a property not informed previously for EuE100 complexes.

Hydrogel membranes based on genipin-cross-linked chitosan blends for corneal epithelium tissue engineering

Novel polymeric hydrogel scaffolds for corneal epithelium cell culturing based on blends of chitosan with some other biopolymers such as hydroxypropylcellulose, collagen and elastin crosslinked with genipin, a natural substance, were prepared. Physicochemical and biomechanical properties of these materials were determined. The in vitro cell culture experiments with corneal epithelium cells have indicated that a membrane prepared from chitosan-collagen blend (Ch-Col) provided the regular stratified growth of the epithelium cells, good surface covering and increased number of the cell layers. Ch-Col membranes are therefore the most promising material among those studied. The performance of Ch-Col membranes is comparable with that of the amniotic membrane which is currently recommended for clinical applications.

Chitosan-based ultrathin films as antifouling, anticoagulant and antibacterial protective coatings

Ultrathin antifouling and antibacterial protective nanocoatings were prepared from ionic derivatives of chitosan using layer-by-layer deposition methodology. The surfaces of silicon, and glass protected by these nanocoatings were resistant to non-specific adsorption of proteins disregarding their net charges at physiological conditions (positively charged TGF-β1 growth factor and negatively charged bovine serum albumin) as well as human plasma components. The coatings also preserved surfaces from the formation of bacterial (Staphylococcus aureus) biofilm as shown using microscopic studies (SEM, AFM) and the MTT viability test. Moreover, the chitosan-based films adsorbed onto glass surface demonstrated the anticoagulant activity towards the human blood. The antifouling and antibacterial actions of the coatings were correlated with their physicochemical properties. The studied biologically relevant properties were also found to be dependent on the thickness of those nanocoatings. These materials are promising for biomedical applications, e.g., as protective coatings for medical devices, anticoagulant coatings and protective layers in membranes.