The search for new hemostatic materials remains a priority for researchers, as the problem of uncontrolled hemorrhage during surgical interventions or traumatic injuries represents a significant challenge. The objective of the study was to identify novel polysaccharide structures with enhanced hemostatic properties based on chitosan. The number of chitosan derivatives with two substituents was synthesized and characterized by 1H NMR, FTIR. One of these was a structural analogue of L-DOPA - N-(3,4-dihydroxybenzyl), while the other comprised fragments of different nature, including hydrophobic N-(4-(tetradecyloxy)benzyl), negatively charged groups N-(4-carboxybenzyl) and aminocaproic acid residue. The hemostatic potential of the novel compounds was evaluated in vitro/in vivo on human blood and in mouse model of tail bleeding. Solutions of chitosan derivatives showed the ability to aggregate with blood about 3-5 times higher than chitosan in a neutral saline medium (0.9 % NaCl) and slightly acidic conditions both when (Ca2+) was added and in the case of citrated blood. Chitosan derivatives demonstrated low toxicity (3T3, HepG2 and Huh7) and did not induce plasma coagulation or platelet aggregation at low concentrations. The novel compounds can be used to modify the surface of biomaterials in order to improve their hemostatic properties.

The review article includes information on the use of coatings, both from chitosan itself and in combination with other polysaccharides and functional compounds, for postharvest processing, mainly of tomatoes, to extend the shelf life of harvested produce. During harvesting of fruits and vegetables, losses due to fungal infection can be as high as 50%. To prevent yield losses and preserve fruit quality, various methods of postharvest treatment are used. Currently, the most effective means used to control postharvest diseases are synthetic fungicides, but their uncontrolled use negatively affects human health and the environment. Recently, there has been a continuing trend to increase the use of natural antimicrobial agents. Such natural compounds can be chitin and chitosan, they are renewable, biodegradable, low toxicity and safe for consumers and the environment. The film-forming ability of chitosan and its antimicrobial, antioxidant properties are important for obtaining functional coatings for postharvest processing of fruits.

Chitosan is a natural polysaccharide and, when applied externally, is able to stimulate both growth and defense of the plant, enhancing its resistance to abiotic stresses and suppressing the development of many phytopathogens. Immune response includes the activation of defense proteins, carbohydrases such as chitinases and glucanases, which are also known to participate in the regulation of morphogenesis. In this study, for the first time, the effect of treatment with unfractionated (hydrolysate) chitosan of low (CH1) and medium (CH2) molecular weight on chitinase and glucanase activities, as well as on the expression of chitinase and β-1,3-glucanase genes in the roots of two cultivars of garlic Allium sativum L. differing by resistance to Fusarium rot was examined. It was shown that the effect of chitosans on the enzymatic activity and expression of the genes encoding β-1,3-glucanases (AsPR2a, AsPR2b, and AsPR2c) and chitinases (AsCHI1, AsCHI3, AsCHI7, AsCHI17, and AsCHI23) is cultivar-specific, which may be due to different susceptibility of the cultivars to Fusarium. The expression pattern of chitinase genes AsCHI10, AsCHI27, and AsCHI34, similar between varieties, suggested their involvement in root tissue morphogenesis. The results indicated a greater stimulatory effect of CH2 in comparison with CH1 on chitinase and glucanase activity. The stronger inhibitory influence of CH2 (as compared with CH1) on the expression of chitinase and β-1,3-glucanase genes correlated with the lower fungicidal effect of CH2 on Fusarium proliferatum. The findings may be used in breeding biotechnology to increase the resistance of garlic to Fusarium.

The review considers the prospects for the use of chitosan nanoforms with metals to combat phytopathogens. Nanoparticles of metals and metal oxides exhibit enhanced biological activity, including antifungal activity, due to their unique physical and chemical characteristics, such as their size, surface area, and charge. A number of studies, mainly in vitro, have demonstrated the inhibitory activity of metal nanoparticles and metal oxides against the growth of a number of phytopathogens. Attention is focused the use of chitosan to produce engineering nanomaterials due to a number of advantages associated primarily with the biodegradability and biocompatibility of the polymer. From a review of articles over the past 15 years, it follows that the use of nanoforms of chitosan, metals, metal oxides, and nanomaterials based on them is preferable for the suppression of phytopathogen growth.

To obtain modified polyurethane (PU) plates, quaternized chitosan (QuatCh; degree of substitution 50%, degree of deacetylation 87%) and unfractionated heparin (UFH) were applied in layers to the plate surfaces. The relief of the surface of the plates was studied via atomic-force microscopy (AFM). After processing, the root-mean-square roughness and the height of the unevenness of the PU profile of the plates significantly increased. The value of the contact angle of the modified PU plates decreased from 86.1° ± 11.3° to 63.2° ± 3.68°. Donor blood and the blood recalcification time test were used to assess the in vitro resistance of the PU plates to the appearance of blood clots on the surface (thromboresistance, TR). When the modified PU plates were incubated with blood for 20–180 min, the TR reached 78.43 ± 4.02–88.94 ± 1.98%. The recalcification time of human blood containing PU plates coated with QuatCh–UFH (483 ± 22.64 s for 20 min of incubation and576.5 ± 24.64 s for 40 min of incubation) significantly differed from the recalcification time of human blood containing PU plates without coating (257.5 ± 12.84 s for 20 min of incubation and 273.3 ± 16.6 s for 40 min of incubation). Thus, layer-by-layer modification of the PU plates with QuatCh and UFH led to a high resistance to the appearance of blood clots on the surface.

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.

We studied hemocompatibility of silver nanoparticles synthesized on the basis of a conjugate of quaternized chitosan with gallic acid (QChit-Gal). For the three variants of silver particles (Nos. 1, 2, and 3), the QChit-Gal:AgNO3 ratio was 5:1, 5:3, and 1:1, respectively. Anticoagulant activity of all samples of silver nanoparticles was lower than that of the conjugate. Samples of nanoparticles Nos. 1 and 2 in a concentration of 0.0233 mg/ml did not affect plasma clotting time and can be used for intravenous administration. However, their concentration in the blood should not exceed 0.01 mg/ml, because in this concentration they do not affect erythrocyte membrane, do not induce platelet aggregation, and do not affect platelet aggregation induced by ADP.

Growth inhibition by chitosans (with molecular weight 6, 12, 18, 25 and 45 kDa) was demonstrated for 10 filamentous fungi belonging to the families Aspergillaceae, Cladosporiacea, Pleosporaceae, Cordycipitaceae and Microascaceae which are responsible for biodeterioration of tempera paintings and are the dominant members of microbiome from Paintings of Ancient Rus Halls, State Tretyakov Gallery, Russia. The greatest effect was achieved at 2% chitosan in agar medium; its antifungal activity increased in the row: 6‒12‒18‒25 kDa. Chitosans with a molecular weights of 25 and 45 kDa inhibited fungal growth to the same degree. Representatives of Cladosporiaceae and Sordariomycetes (Cordycipitaceae and Microascaceae) showed the greatest sensitivity to chitosan. Some Aspergillaceae were found to exhibit elevated resistance. Investigation of antifungal activity of chitosans incorporated into tempera materials to assess their possible application as art objects antiseptics will be the goal of our further research.

The effect of the main characteristics of low molecular weight chitosan obtained via enzymatic and chemical hydrolysis with a molecular mass (MM) of 2–100 kDa, a deacetylation degree (DD) of 60–98%, and a polydispersity (Mw/Mn) of 1.9–2.7 on the growth of Botrytis cinerea has been studied. The greatest inhibitory effect on the fungal germination process (a conidia germination index of less than 50%) was provided by chitosan samples with an MM of 2–13 kDa, a DD of 85–98%, and a polydispersity of 2–2.5. Among the most effective was chitosan with an MM of 13 kDa and a deacetylation degree 98%, which had a significant inhibitory effect on the growth of the fungal mycelium at concentration 0.938 mg/mL. This sample of chitosan and its complex with copper ions (75 ppm) significantly suppressed fungal metabolic activity (up to 20 and 10%, respectively), which indicates their high potential as antifungal agents for the development of fungicides.

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.

Conjugates of chitosan (molecular weight 28 and 830 kDa) with gallic acid were synthesized by a reaction initiated by a free radical. The conjugates contained 106 and 119 mg of polyphenol per g of polymer. Thin films were obtained from solutions of synthesized chitosan derivatives, and their physico-chemical characteristics (thickness of 0.058–0.076 mm and moisture content of 7.92–9.44%), as well as the antioxidant (inhibiting activity with respect to 2,2-diphenyl-1-picrylhydrazyl) and antimicrobial properties, were studied in relation to Staphylococcus epidermidis and Escherichia coli .

В обзоре процесс диссоциации рассматривается как один из важных факторов, создающих гетерогенность популяции бактерий. Частота диссоциативных переходов составляет 10-10 на одно клеточное деление. Подчеркивается, что существуют строгие коррелятивные зависимости между генетическими, физиолого-биохимическими и морфологическими различиями диссоциантов, причем первичные фенотипические изменения происходят в их клеточных оболочках (в размере и химическом строении капсулы, клеточной стенки и цитоплазматической мембраны), что определяет различия в морфологии клеток и колоний, скорости роста, устойчивости к внешнему воздействию, способности к синтезу биологически активных веществ. Даны некоторые практические советы для прогнозирования и управления гетерогенным составом популяции, создаваемым процессом диссоциации, для стабилизации выхода синтезируемых клетками практически ценных веществ.

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.