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.

Thrombin and Factor Xa Hydrolysis of Chromogenic Substrates in the Presence of Sulfated Derivatives of Galactomannan and Galactoglucomannan Natural Gels.

Polysaccharides are important structural components of all plant species. Gel-like polysaccharides have found wide application in various fields, including medicine, construction, and the food industry. In the present work, galactomannan and galactoglucomannan gel-like polysaccharides were modified with sulfate groups and their anticoagulant activity was studied. Sulfation with chlorosulfonic acid in pyridine and with sulfamic acid in pyridine and a sulfamic acid-urea deep eutectic solvent were used as synthesis routes. The resulting gel-like polysaccharide sulfates were studied by elemental analysis, Fourier-transform infrared spectroscopy, and gel permeation chromatography. It was established that the anticoagulant effect of sulfated galactoglucomannan (SGGM) and galactomannan (SGM-1 and SGM-2) is related to an independent antithrombin-independent decrease in the amidolytic activity of thrombin and factor Xa. It is shown that the inhibitory activity of SGGM and SGM-2 against the collagen-induced platelet aggregation can be an additional factor in selecting compounds that are most promising for modifying polymer surfaces to ensure resistance to blood clotting.

The Development of New Low-Molecular-Weight Factor Xa Inhibitors that are Potential Anticoagulants.

BACKGROUND: Despite the introduction of direct oral anticoagulants, the search for new oral anticoagulants remains an urgent task. OBJECTIVE: By using docking and scoring, based on physical methods, simple chemical rules, methods of synthesis, and activity measurement, develop new low-molecular-weight inhibitors of factor Xa, which are potential anticoagulants. METHODS: The development of leads was based on chemical synthesis and structure-based drug design methods. The basic idea was to combine the two approaches: one based on predictive modeling and the other based on the experimental data. RESULTS: In this study, we developed some nanomolar leads. Further chemical modification improved the inhibition constant by more than one order. DISCUSSION: The method proposed in this paper, as well as other methods, includes virtual screening, chemical synthesis, and activity measurement. However, the most time-consuming process in this method (chemical synthesis) was simplified, and the cost was reduced to the extent that was allowed; a very simple chemical reaction was chosen, i.e., the formation of an amide bond. CONCLUSION: In this work, we demonstrated how using simple chemical rules based on the structurebased drug design, substances with a nanomolar concentration of activity can be developed.

Synthesis of silver nanoparticles using gallic acid-conjugated chitosan derivatives.

In presented study, various chitosan derivatives containing covalently bounded gallic acid were obtained: chitosan with gallic acid (CG), quaternized chitosan with gallic acid (QCG), and succinylated chitosan with gallic acid (SCG). Chitosan derivatives were used as stabilizing and reducing agents in the synthesis of silver nanoparticles (AgNPs). The dimensional characteristics of nanomaterials were determined by transmission electron (TEM), dynamic light scattering (DLS) and atomic force (AFM) microscopy, antibacterial activity (against E. coli, S. epidermidis), cytotoxicity (HaCaT, Colo 357 cell lines) and hemocompatibility. Among all samples, QCG-AgNPs showed low toxicity in the range of studied concentrations (3.125-100 µg/ml) high stability of nanoparticle for 4 months (according to UV.spectroscopy data) the highest antibacterial activity against S. epidermidis (3.91 µg/ml). The high antibacterial activity, stability, and simplicity of the process of producing AgNPs based on the QCG derivative reveals that a new method for producing modified AgNPs deserves future consideration.

Synthesis and hemocompatibility of amino (di-)butyldeoxy modified hydroxyethyl starch.

Cationic polymers are of interest as the basis for obtaining various biomaterials. Hydrophilic biopolymers and their modification products are of main interest. Biocompatibility is the prime criterion that makes this material usable for said purposes. In this research, hydroxyethyl starch (HES) was used as a basis for synthesis of aminodeoxy derivatives, containing n-butylamin (BA) and dibutylamin (DBA) fragments. Bromodeoxy HES was an intermediate compound. The structure of synthesized polymers was confirmed with NMR, elemental analysis and FTIR methods. The derivatives with 0.6 and 0.9 degree of substitution were tested for compatibility with blood. The research showed that HES base does not have an anticoagulation activity, does not affect human platelet aggregation and in concentrations up to 10 mg/mL of cell suspension in a buffer solution does not destroy red blood cell membrane, and therefore can be used as a component of drug delivery systems. Addition of aminodeoxy derivatives of HES hindered development of ADP-induced platelet aggregation. Derivatives of HES-DBA and HES-BA0.9 may also be of interest, but their concentration must not exceed 1 * 10-5 mg/mL of blood. Biodegradation of HES cationic derivatives were analyzed through identification of reducing sugars after treatment with amylase and pancreatin.

The Development of New Factor Xa Inhibitors Based on Amide Synthesis.

BACKGROUND: Factor Xa (FXa) is known to play a central role in blood coagulation cascade and considered to be one of the most attractive targets for oral anticoagulants of new generation. OBJECTIVE: Our approach for the development of directly acting oral anticoagulants (DOAC), FXa inhibitors was demonstrated in this work. METHOD: Chemical synthesis is the base of our approach for the development of potential inhibitors. In this work, the substances like R1-(CONH)-R2-(CONH)-R3 are being developed, using previously described docking and screening methods, where R1, R2 and R3 are some chemical groups and (CONH) are amide bonds connecting R1, R2 and R3. The direction of amide bond (CONH) could be arbitrary for R1, R2 and R2, R3. RESULTS: Chemical modifications were made in the frame of the results, taking into account the structure of FXa, chemical synthesis capabilities, as well as patentability of the target compounds. Subnanomolar potency of several developed compounds was achieved. Several analyzers and various testing-suites have been used to measure the concentration that doubled the prothrombin time (PTx2). Moreover, in human plasma the PTx2 concentration of the compound 217 (DD217) turned out to be 80±20 nM. The compound efficacy has proved by in vivo assays including oral administrations in rats, rabbits and monkeys. CONCLUSION: The pharmacodynamic profile of DD217 for oral administration in cynomolgus monkeys proves the efficacy of the compound, which makes it promising for the future preclinical trials.