Effect of Oligochitosan on Experimental Venous Thrombosis in Guinea Pigs.

Oligochitosan Сh10/85 with a molecular weight of 10 kDa and a deacetylation degree of 85% prevented the development of experimental venous thrombosis in guinea pigs after intravenous administration in a dose of 30 mg/kg. In a concentration of 0.005-0.5 mg/ml, oligochitosan Ch10/85 did not provoke hemolysis of human red blood cells in in vitro experiments. The antithrombotic effect of oligochitosan Ch10/85 that exhibits low anticoagulant activity (by two orders of magnitude lower than that of unfractionated heparin) can be associated with inhibition of platelet aggregation.

Chitin/Chitosan and Its Derivatives: Fundamental Problems and Practical Approaches.

In this review, we present the data on the natural occurrence of chitin and its partially or fully deacetylated derivative chitosan, as well as their properties, methods of modification, and potential applications of derivatives with bactericidal, fungicidal, and antioxidant activities. The structure and physicochemical characteristics of the polymers, their functions, and features of chitin microbial synthesis and degradation, including the processes occurring in nature, are described. New data on the hydrolytic microorganisms capable of chitin degradation under extreme conditions are presented. Special attention is focused on the effect of physicochemical characteristics of chitosan, including molecular weight, degree of deacetylation, polydispersity index, and number of amino group derivatives (quaternized, succinyl, etc.) on the antimicrobial and antioxidant properties of modified polymers that can be of particular interest for biotechnology, medicine, and agriculture. Analysis of the available literature data confirms the importance of fundamental research to broaden our knowledge on the occurrence of chitin and chitosan in nature, their role in global biosphere cycles, and prospects of applied research aimed at using chitin, chitosan, and their derivatives in various aspects of human activity.

Analysis of the Action of Quaternized Chitosans with Different Molecular Weight on Anticoagulant Activity of Heparins In Vitro.

Quaternized derivatives of chitosan with a substitution degree of 85-98% (highly substituted) synthesized from chitosans with a molecular weight of 5, 10, 20 kDa, with a degree of deacetylation of 89-98%, and the code numbers of QChit 5, QChit 10, QChit 20, respectively, completely neutralize antithrombin activity of unfractionated heparin and partially neutralize aXa activity of low-molecular-weight heparin (clexane), similar to protamine sulfate. The advantages of QChit 5 and QChit 10 over QChit 20 and protamine sulphate are the follows: the effect is achieved at lower concentrations and in greater concentration range; they do not promote platelet aggregation; in a concentration of 0.0072 mg/ml they do not destroy the erythrocyte membranes.

Effects of Chitosan Derivative N-[(2-Hydroxy-3-Trimethylammonium)Propyl]Chloride on Anticoagulant Activity of Guinea Pig Plasma.

Intravenous injection of protamine sulfate or quarternized chitosan derivative to guinea pigs after injection of 70 aIIa U/kg non-fractionated heparin shortened plasma clotting time (shown by partial activated thromboplastin time, thrombin time, and prothrombin time). Intravenous injection of protamine sulfate or quarternized chitosan derivative to guinea pigs after injection of 1 mg/kg (100 aXa U/kg) low-molecular-weight heparin (clexane) led to shortening of plasma clotting time in the ReaClot Heparin test and to prolongation of plasma amidolytic activity in the factor Xa chromogenic substrate test.

[Antibacterial Activity of Alkylated and Acylated Derivatives of Low-Molecular Weight Chitosan].

A number of alkylated (quaternized) and acylated derivatives of low-molecular weight chitosan were obtained. The structure and composition of the compounds were confirmed by the results of IR and PMR spectroscopy, as well as conductometric titration. The effect of the acyl substituent and the degree of substitution of N-(2-hydroxy-3-trimethylammonium) with the propyl fragment appended to amino groups of the C2 atom of polymer chains on antibacterial activity against typical representatives of gram-positive and gram-negative microorganisms (Staphylococcus epidermidis and Escherichia coli) was studied. The highest activity was in the case of N-[(2-hydroxy-3-trimethylammonium)propyl]chitosan chloride with the maximal substitution (98%). The minimal inhibitory concentration of the derivative was 0.48 µg/mL and 3.90 µg/mL for S. epidermis and E. coli, respectively.

[Antibacterial effect of peptide conjugates with a quaternized chitosan derivative and its estimation by the method of atomic force microscopy].

We obtained a number of conjugates based on a quaternized chitosan derivative and antimicrobial peptides (melittin and warnerin) crosslinked by microbial transglutaminase. We determined the optimal conditions for the synthesis (30 minutes, with a mole ratio of peptides and chitosan derivative of 1.4: 100) and studied the antibacterial properties of obtained conjugates. The antibacterial effect of the conjugates was found to be greater than that of their components. The antibacterial activity of the conjugates was determined by the double-dilution method and by atomic force microscopy.

[Neutralization of anticoagulant activity of heparin by N-[(2-hydroxy-3-trimethylammonium) propyl] chloride derivatives of chitosan].

Alkylated derivatives of low molecular weight chitosan with different substitution degrees of 98, 40, and 9% (I, II, and III respectively) have been synthesized. The structure of the obtained derivatives was defined by spectral assays (IR-spectroscopy and proton magnetic resonance). Chitosan derivatives were characterized with positive zeta-potential (33­51 mV) and solubility from 2 to 100 mg/mL in pH 7.4 and 25°C. It was shown that, at a concentration of 0.0014­0.0029 mg/mL, derivative I, as well as protamine sulfate, could be used to neutralize the anticoagulant activity of unfractionated or low molecular weight heparin. At a concentration of 0.0029­0.58 mg/mL, derivative I enhanced platelet aggregation, which would be necessary when hemostatic compounds or materials were used. Derivatives II and III enhanced platelet aggregation to a lesser extent.

[Analysis of toxicity and biocompatibility of chitosan derivatives with different physico-chemical properties].

A comparative study of the toxicity and hemocompatibility of chitosan and its derivatives with different acetylation degrees, molecular masses, charges, and hydrophobicity has been performed. It has been shown that only positively charged chitosan derivatives activate platelets and suppress cell proliferation, regardless of the acetylation degree, molecular mass, and hydrophobicity. Chitosan quaternization decreases toxicity at a low degree of substitution and abruptly increases it at a high one. Negatively charged chitosan derivatives were nontoxic and compatible with blood components. It was concluded that the toxicity of chitosan and its derivatives is defined by their charge and solubility at a neutral pH.