Vladimir E Tikhonov

• PhD (Chemistry)
• Researcher at Russian Academy of Sciences

The growing use of vaccines based on chitosan/protein complexes requires a deep knowledge of how the structure of chitosan influences the complexation with the protein and its structural alterations and thermal stability within complexes. Herein, the effect of the overall charge of partially N-reacetylated short chain chitosan derivatives (ROCHI) o...

Introduction The influence of chitosan's physicochemical characteristics on the functionality of lactic acid bacteria and the production of lactic acid remains very obscure and contradictory to date. While some studies have shown a stimulatory effect of oligochitosans on the growth of Lactobacillus spp, other studies declare a bactericidal effect o...

Here is an insight into the interaction and formation of insoluble complexes of ovalbumine (OV) with a series of specific chitosan derivatives (oligochitosan (OCHI)), varying in the degree of acetylation (DA) in acidic, neural and alkaline media. The forces involved in the complexation are determined and discussed. As shown, the interaction is part...

The paper presents the results of the synthesis, a detailed kinetics study, and an investigation of the biological activity of silver nanoparticles (AgNPs) in aqueous solutions of N-reacetylated oligochitosan hydrochloride. UV–visible spectrophotometry and dynamic light scattering were employed to control silver ion reduction. The process was obser...

Energetics of chitosan (CS) polyplexes and conformational stability of bound DNA were studied at pH 5.0 by ITC and HS-DSC, respectively. The CS-DNA binding isotherm was well approximated by the McGhee-von Hippel model suggesting the binding mechanism to be a cooperative attachment of interacting CS ligands to the DNA matrix. Melting thermograms of...

Phase analysis, spectroscopic, and light scattering methods are applied to investigate the peculiarities of the interaction of oligochitosan (OCHI) with native and preheated bovine serum albumin (BSA) as well as the conformational and structural changes of BSA in BSA/OCHI complex. As shown, untreated BSA binds with OCHI mainly forming soluble elect...

The interaction between carboxymethyl cellulose and partially reacetylated chitosan soluble in acidic and alkaline aqueous media is studied by light scattering and isothermal titration calorimetry in a wide pH range. It is shown that the formation of polyelectrolyte complexes (PEC) can occur in the pH range of 6-8, while this pair of polyelectrolyt...

Edible crayfish are an object of local fishing and artificial breeding in many countries. This industry is very promising in terms of production of healthy foods and byproducts, such as biologically active polyaminosaccharide—chitosan and its derivatives. However, crayfishing is far from being at the level at which it could be. This laboratory scal...

Сomplexation of oligochitosan (OCHI) having the degree of acetylation (DA 26 %) with sodium caseinate (SC) at pH 5.8 and 7.2 is described and compared with the complexation of OCHI (DA 2 %) at pH 5.8. In the alkalescent medium, the complexation of OCHI (DA 26 %) is weaker and dualistic depending on SC concentration in the system. In the diluted alk...

Cancer diseases are characterized by high incidence and mortality worldwide. The main problem in cancer therapy is the lack of specificity of anti-cancer drugs. Therefore, the development of new methods of targeted delivery of anti-cancer drugs is an urgent task in oncology. Nanoparticles from hyaluronic acid and chitosan (HA:CS) were obtained usin...

β-lactoglobulin–oligochitosan (MW 9500 Da) system was studied under conditions of protein-polysaccharide incompatibility, the dipole-charge, and charge-charge protein-polysaccharide interactions at pH 3.0, 5.5, and 6.0, respectively, using ITC, DSC, and DLS. At pH 5.5 and 6.0, the ITC data revealed a complex formation between β-lactoglobulin and ol...

In this work, the interaction between the negatively charged surfactant sodium dodecyl sulfate (SDS) and partially N-reacetylated chitosan (RA-CHI), which is soluble at pH range up to pH 12, is studied in a wide pH range including alkaline media by light scattering (LS) and isothermic titration calorimetry (ITC). It is shown that in the weakly alka...

Interaction of binary chitosan/nonionic surfactant (NIS) system with sodium dodecyl sulfate (SDS) in aqueous solution is described using turbodimetry, light scattering, electophoretic mobility and cryogenic electron microscopy. The formation of insoluble CHI/SDS complexes is weakened with a decrease in molecular weight of chitosan and critical mice...

Pre-sowing treatment of seeds of hybrid Polesskiy 185 with aqueous solutions of oligochitosan (OX) with molecular weight (MW) 28.6 kDa, melanin from chaga, and their complex was used to stimulate the growth processes of corn in laboratory experiments. Treatment of seeds with oligochitosan solutions with concentrations: 0.0005%, 0.001%, 0.005%, 0.01...

Stimulation of the growth processes of maize variety “Stasya×LJ 48/18”, the seeds of which were treated with aqueous solutions with concentrations: 0.0005 %, 0.001 %, 0.005 %, 0.01 % oligochitosans (OLGs), depends on molecular weight (MW) and the degree of acetylation (DA) of OLGs. Oligochitosan with MW of 20.1 kDa and DA 1.0 % stimulated maize roo...

The methods commonly used for depolymerization of chitosan and preparation of oligochitosan are discussed. A synthetic approach to oligochitosan hydrochloride with a molecular weight below 16 kDa based on the treatment of parent industrial high molecular weight chitosan with a mixture of hydrochloric acid and hydrogen peroxide is described. A serie...

Molecular interaction of chitosan with sodium dodecyl sulfate (SDS) is a more complicated process than it has been imagined so far. For the first time it has been shown that the shorter chitosan chains are, the more preferably they interact with the SDS and the larger-in-size microparticles they form. The influence of ionic strength, urea and tempe...

N‐reacetylated oligochitosan (RA‐oligoCHI) with molecular weight (MW) ≤ 12 kDa and a random‐type distribution of acetyl groups can form soluble RA‐CHI/SDS complexes and transparent solutions both in acidic, where RA‐oligoCHI is soluble, and alkaline aqueous media, where RA‐oligoCHI is soluble too, at SDS concentration above its critical micellar co...

It was established that decrease of oligochitosans with molecular masses 7.0, 25.4, 45.3 kDa concentration in the process of Lactobacillus bulgaricus cultivation leads to fermented dairy product pH reduction and titratable acidity increase. Further increase in titratable acidity and decrease of lactic acid microorganisms’ amount was determined duri...

Oligochitosan samples were obtained by acid hydrolysis of high molecular weight chitosan isolated from Bombyx mori (B.M.). Carrying out acid hydrolysis for 6 hours, it was found that after 4 hours and further with increasing duration, the molecular weight of chitosan decreases to a value corresponding to the ranges of mo-lecular weights of oligochi...

Oligochitosan, a low molecular weight derivative of the cationic biopolymer, chitosan, currently shows a great potential of application as a biodegradable non-toxic stimuli-sensitive drug carrier. This paper aimed to elucidate the thermoresponsive potential of oligochitosan and the temperature-controlled drug binding and release to shed light on ol...

Thermoresponsivity of chitosan induced by β-glycerophosphate (GP) in diluted aqueous solutions has been first studied by high-sensitivity differential scanning calorimetry. It has been found that the GP solutions of chitosan undergo a first-order phase transition upon heating. The onset of this transition coincides with the cloud point of the syste...

A series of industrial chitosans were analyzed on the presence of residual heavy metals. For the first time, optical microscopy data showed that chitosan solution retained a huge number of insoluble microparticles while transmittance electron microscopy revealed that insoluble fibrous microparticles were incrusted by crystalline nanoparticles with...

For biomedical applications, chitosan and oligochitosan must be appropriately characterized and meet pharmacological requirements in terms of contamination by residual heavy metals. In this work, a series of commercial chitosans was analyzed by ICP-MS method, and high concentration of Fe (44–382 ppm), Cr (3.1–35.5 ppm) and Ni (0.33–7.91 ppm) exceed...

Treatment of Polessky 185 hybrid maize seed with 0.001% aqueous solutions of oligochitosans (OC) with molecular weights (MW): 6.9 kDa; 18.4 kDa; 28.6 kDa stimulates root growth and increase in mass of seedlings. Oligochitosan with MW 28.6 kDa had the greatest elicitor activity. Treatment of seeds with 0.001% OC aqueous solutions with varying degree...

The hemostatic and immunostimulating activity and cytotoxicity were determined for a number of chitosans differing in molecular weight (from 3 to 510 kDa) and degree of acetylation (from 1 to 25 mol%) that were used as adjuvants in inactivated poliomyelitic, influenza, and live influenza vaccines. It has been shown that the hemostatic activity of c...

The process of complex formation of casein from skimmed milk and purified casein with chitosan of different molecular weights was studied. It was shown that at pH 6.3 casein micelles and parts of whey proteins coagulated with positively charged chitosan molecules with molecular weights of 45.3, 25.4, 7.7 and 1.5 kDa. As a result of ionic interactio...

It is well known that chitosan degradation by nitrous acid leads to oligochitosan (oligoCHIt–ahm) bearing reactive 2,5-anhydromannose (3,4-dihydroxy-5-hydroxymethyl-tetrahydrofuran-2-aldehyde) units at the new reducing ends of macromolecules. Standard protocol requires reduction of oligoCHIt–ahm with NaBH4 to corresponding oligoCHIt–hml bearing unr...

In this work, we show that the reduction of oligoCHI-ahm with NaBH4 leads to a branched oligoCHI-hml, the approach to preventing the branching by preparing a non-branched oligochitosan oxime, oligoCHIt-oxm, as well as cytotoxicity testing of oligoCHI derivatives before and after long shelf storage. Full text is available on-line until July 04. 2018...

Biomacromolecules, 2017, DOI: 10.1021/acs.biomac.7b00039 Free Electronic Reprints: https://mail.ineos.ac.ru/cgi-bin/webmail?timestamp=1492151251&md5=1xqn4%2FxcSHp0LgIkZqK1mg%3D%3D&redirect=http%3A%2F%2Fpubs%2Eacs%2Eorg%2Fpage%2Fpolicy%2Farticlesonrequest%2Findex%2Ehtml N-Reacetylated Oligochitosan: pH dependence of Self-Assembly Properties and An...

The microstructure of complex and composite poly(vinyl alcohol) (PVA) cryogels containing water-soluble chitosan hydrochloride (ChHC) of dispersed particles of water-insoluble chitosan base (Ch), respectively, has been studied by optical microscopy and attenuated total reflection FTIR spectroscopy. The macroporous morphology of cryogels has been st...

An induction of apoptosis by short chain chitosans in human lung carcinoma A549 cells and cow embryonic lung cells was studied. Seventeen well-defined oligochitosans with wide range of molecular weights, from 5.5 to 46.7 kDa, were used in this study. The experiments showed that three oligochitosans with molecular weight 6.1, 7.7, and 9.0 kDa notabl...

A method for the determination of the antimicrobial activity of chitosan with the use of organic salts for the production of pH in the range of 5.5–8.2 was studied. The double-dilution method demonstrated the effectiveness of the determination of the antimicrobial activity of chitosan samples with different molecular weights and solubilities. It wa...

Complex macroporous poly(vinyl alcohol) (PVA) cryogels have been obtained by cryogenic treatment (freezing at–20°C for 12 h followed by defrosting at a rate of 0.03°C/min) of PVA–chitosan hydrochloride mixed solutions. The subsequent alkaline treatment of the cryogels has resulted in the transformation of the water-soluble salt form of chitosan int...

Abstract: this manuscript describes several chemical methods most commonly used for chitosan depolymerization and oligochitosan preparation in comparison with a newly elaborated MTC technology. Peculiarities, including advantages and drawbacks, of the methods are also described. Illustrative data include Table (2) and Figures (4)

Antibacterial activity of chitosan with different molecular weight at different pH values against gram-negative Klebsiella pneumoniae was studied. It was found that the dependence of inhibition activity of chitosan on its molecular weight was inversed when the medium pH was increased above 7.0. In acidic media higher molecular weight chitosan had t...

Acrylamide-based hydrogel nanoparticles, which had hydrodynamic radii in aqueous dispersions of about 100–180 nm, were prepared by miniemulsion polymerization. The redox initiation at the interfacial boundary made it possible to conduct synthesis at an ambient temperature with a high rate and resulted in latexes of enhanced aggregative stability. T...

A facile method of preparation of stabilized and functionalized nano- and microparticles of magnetite by successive application of oppositely charged polymers with a regular structure of macromolecular chains ( chitosan and maleic acid copolymers) onto Fe3O4 core are developed. This approach makes it possible to create two types of magnetite interp...

A facile method of preparation of stabilized and functionalized nanoand microparticles of magnetite by successive application of oppositely charged polymers with a regular structure of macromolecular chains (chitosan and maleic acid copolymers) onto Fe3O4 core are developed. This approach makes it possible to create two types of magnetite interpoly...

This report has been prepared to present clear concepts and definitions of general and specific terms with regards to chitin, chitosan and their derivatives. Current concepts of polymer chemistry and physics (monomer, oligomer, polymer, persistence length, Kuhn segment) have been used to define terms: chitin, chitosan, oligochitosan, chitooligomer,...

Light scattering and microscopy studies show that short chain chitosans (oligochitosans) are partially associated in dilute solutions in the pH range below critical point of phase separation. The observed structural diversity of solutions (spherical and fibril-like aggregates, and molecularly dispersed systems – “true solution”) depends on purifica...

The kinetics of the adsorption at the air–water interface and the processes of the structure formation inside the adsorption layers of the alkylated chitosan (the cationic polysoap) have been studied in function of its bulk concentration and the ageing time of the adsorption layers. It has been shown that the dynamic surface tension γ(t) of this po...

Low molecular weight chitosans grafted with N-/2(3)-(dodec-2-enyl)succinoyl groups (HM-LMW-chitosans) with a mean molecular mass of 5kDa, a degree of acetylation of 3% and a degree of tetradecenoyl substitution (TDC) of 3–18mol% have been synthesized. These molecules are monodisperse and soluble in water at neutral pH. Using tensiometry and Nile Re...

Low molecular weight chitosans (5 kDa) hydrophobically modified with 3, 10, and 18 mol % of tetradecenoyl (TDC) groups have been synthesized. Their good solubility at neutral pH, their surface activity and micelle-forming properties as well as their ability to interact with negatively charged phospholipid vesicles mimicking the internal layer of ce...

We studied the effect of combined preparation on the basis of chitosan containing a bioregulator isolated from cattle serum in a concentration of 10(-10) mg/ml on healing of II-IIIa degree skin burns in mammals in vivo.

We studied the effect of combined preparation on the basis of chitosan containing a bioregulator isolated from cattle serum in a concentration of 10(-10) mg/ml on healing of purulent wounds in mammals in vivo.

Oligochitosan samples varying in molecular weight (Mw) and having narrow polydispersities were prepared by means of depolymerization of chitosan in hydrochloric acid, and their antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA) was measured at pH values 5.5–8.0. The antibacterial testing of oligochitosans obtained sho...

Chitosan has been reported to be a non-toxic, biocompatible antibacterial, antifungal and insecticidal agent. In many publications it has been shown that the biocidal activity of chitosan can grow or reduce with the reduction of chitosan molecular weight (MW). In some experiments it has been shown that the antimicrobial activity of chitosan does no...

The nematophagous fungus Pochonia chlamydosporia degrades chitosan, an antifungal compound that severely affects plant pathogenic fungi, but not nematophagous and entomopathogenic fungi. Extracellular proteins from culture filtrates of P. chlamydosporia grown with either colloidal chitin or chitosan as main carbon and nitrogen sources were investig...

A novel method was developed to incorporate macrocyclic polyene antibiotics, nystatin and amphotericin B, into liposomes prepared from the mixture of phosphatidylcholine and cholesterol (7: 3) or phosphatidylcholine, cholesterol, and cardiolipin (7: 3: 1). Membranes of the liposomes were modified using the amphiphilic polymer N-vinylpyrrolidone wit...

Holographic sensors based on the hydrogels containing affinity groups sensitive to certain components of gaseous and liquid mixtures represent a promising class of sensors. These sensors have some advantages: the simple qualitative visual way of the information readout, exploitation simplicity, reversibility, wide spectrum of application, and a low...

Low molecular weight chitosans (5 kDa) hydrophobically modified with 3, 10, and 18 mol % of tetradecenoyl (TDC) groups have been synthesized. Their good solubility at neutral pH, their surface activity and micelle-forming properties as well as their ability to interact with negatively charged phospholipid vesicles mimicking the internal layer of ce...

Chitosan derivatives are potential candidates for gene delivery because they are biocompatible and low toxic. However, their use has been limited by their moderate transfection efficiency and the rather large sizes of DNA complexes with high molecular weight chitosans. To circumvent these limitations, we used low molecular weight (approximately 5 k...

Amphiphilic N-[2(3)-(dodec-2′-en-1′-yl)succinoyl]chitosan (DDC-chitosan) of varying degree of substitution was synthesized by the reaction of chitosan with (2-dodecen-1-yl)succinic anhydride in 1% acetic acid/methanol (1:1 v/v) solution. A degree of substitution (5–30mol.%) depended on anhydride/amino group ratio. Surface tension activity, rheologi...

Galactomannan from seeds of Cyamopsis tetragonoloba (L.) Taub. (guar) was depolymerized using immobilized enzymatic preparation celloviridin. A set of fragments whose molecular weights varied from 12.6 to 245.6 kDa was obtained. Sulfated derivatives of components of all fractions were synthesized, in which the content of HSO 3− groups was 48.05 ± 2...

The synthesis of a series of low-molecular-weight chitosans and the results of their bioassay against several phytopathogenic fungi are described.

Regioselective quaternization of chitosan and its amphiphilic derivatives has been carried out by means of reaction with betaine in the presence of the coupling reagent 2-ethoxy-1-ethoxycarbonyl-1,2-dihydroquinoline (EEDQ) in aqueous media at pH 5.5 ± 0.5. This reaction results in preparation of N-/(trimethylammonio)acetyl/chitosan chloride and its...

A new approach to the preparation of water soluble polymer in inverse miniemulsions is proposed. A redox initiation system consisting of ceric ions and carbohydrate-based surfactant Span 60 as a reducing agent is successfully used for the polymerization of AAm. This initiation system provides chain nucleation and growth near interfacial boundaries....

The direct reaction of 2-ethoxy-1-ethoxycarbonyl-1,2-dihydroquinoline (EEDQ) with chitosan amino groups, which resulted in the formation of N-(ethoxycarbonyl)chitosan, was found and confirmed chemically and by IR and 1H NMR spectroscopy.

Low molecular weight chitosans grafted with N-/2(3)-(dodec-2-enyl)succinoyl groups (HM-LMW-chitosans) with a mean molecular mass of 5 kDa, a degree of acetylation of 3% and a degree of tetradecenoyl substitution (TDC) of 3-18 mol% have been synthesized. These molecules are monodisperse and soluble in water at neutral pH. Using tensiometry and Nile...

Low molecular weight chitosan (4.6 kDa) and N-/2(3)-(dodec-2-enyl)succinoyl/-derivatives of different degrees of substitution were tested for their antimicrobial activity against Escherichia coli, Pseudomonas aureofaciens, Enterobacter agglomerans, Bacillus subtilis, Candida kruisei and Fusarium oxysporum f. sp. radicis lycopersici. The results ind...

Amphiphilic N-derivatives of chitosan containing C12 alkyl and carboxyl groups were obtained. It was shown that the compounds obtained have fungicidal activity and form intermolecular associates in solutions.

The kinetics of the adsorption at the air–water interface and the processes of the structure formation inside the adsorption layers of the alkylated chitosan (the cationic polysoap) have been studied in function of its bulk concentration and the ageing time of the adsorption layers. It has been shown that the dynamic surface tension γ(t) of this po...

Fluorimetric method for determination of endochitinolytic activity using N-fluorescein-labeled chitin (FITC-Chitin) is proposed, and a procedure for FITC-Chitin preparation with a degree of FITC content of 2.2 mol.% (one FITC molecule per 45 glucosamine residues) is described. FITC-Chitin is capable to distinquish endochitinase and exochitinase (β-...

The 'bubble-flotation chromatography' technique was proposed and successfully applied to the selective separation of chitosan samples of different hydrophobicity from their mixed aqueous solutions.

Culture filtrates of the nematophagous fungi Verticillium chlamydosporium and V. suchlasporium growing on colloidal chitin showed increasing chitinolytic activity and production of two (32- and 43-kDa) main proteins. Maximum activity was found 18-20 days after inoculation, but V. suchlasporium always displayed higher activity. Zymography of such fi...

Extracellular enzymes--a chitinase and a protease with molecular weights 22 and 32 kDa, respectively--were isolated from Streptomyces kurssanovii cells. After purification on modified regenerated chitin, the enzymes were virtually homogeneous according to denaturing PAGE. Both enzymes were found to degrade chitosan.

A chitinolytic enzyme complex produced by the Gram-positive bacterium Streptomyces kurssanovii was immobilized on macroporous cross-linked chitin by physical adsorption, and the biocatalyst obtained used for the preparation of acid-free-water soluble chitosan with a molecular weight of 2–9 kDa starting from commercial crab chitosan by two-step hydr...

A highly O-cross-linked chitin-based sorbent resistant toward digestion by the extracellular chitinolytic complex of Streptomyces kurssanovii was prepared by means of cross-linking of N-acetylchitosan with 2,3-epoxypropyl chloride. Not less than four stages of cross-linking were required for the matrix to be fully resistant toward the action of chi...

Chitosan was cross-linked to various extents with nitrilotriacetic acid in the presence of a water-soluble carbodiimide in homogeneous solution, and was then fully N-acetylated. The structure of the nitrilotriacetic acid residues attached to the chitin backbone was determined by acid-base titration. It was shown that the chitin derivatives containe...

The preparation of two affinity-chromatography sorbents based on cross-linked chitin are described. Both sorbents retained selectively one of the four extracellular chitinases in the culture supernatant produced by Streptomyces kurssanovii. Chitinases with molecular masses of 42 kDa and 26 kDa were isolated in homogeneous form using one-step affini...

One of the four chitinases with a molecular mass of 42 kDa existing in the chitinolytic enzyme complex produced by Streptomyces kurssanovii was separated in homogeneous form using one-step affinity chromatography on cross-linked and phosphorylated chitin-type sorbents. Three other chitinases were not selectively bound by the sorbents and were not o...

Chitosan was crosslinked to varying extents with bis(vinylsu1fonyl)arenes as crosslinking agents in homogeneous solution. The effect of reaction conditions on the onset of gelation was investigated. The rate of gelation was shown to depend on the chitosan concentration and the structure of the crosslinking agent used. The degree of crosslinking and...

Chitosan was crosslinked to varying extents with bis(vinylsulfonyl)arenes as crosslinking agents in homogeneous solution. The effect of reaction conditions on the onset of gelation was investigated. The rate of gelation was shown to depend on the chitosan concentration and the structure of the crosslinking agent used. The degree of crosslinking and...

The action of a microbial chitinolytic enzyme complex from Streptomyces kurssanovii on chitosan gels with various degrees of cross-linking and on the O-derivatives of the gels was examined. The rate of digestion of the gels was shown to depend on the degree of cross-linking as well as on the size of the O-substituent, decreasing greatly with a rise...

The significant differences in the racemization rates of amino acids and the corresponding amides make it possible to carry out selective racemization of amides in the presence of optically active amino acids.

Polymer analogue transformations have been used to synthesize a number of cross-linked polymers containing salycilic aldehyde or fragments similar to it in the acidic groups that ensure that the products swell in aqueous media. With lysine, valine, alanine and glutamic acid as examples, the catalytic activity of the products obtained have been demo...

Isomers of polyacylamidosalicylic aldehyde have been prepared by reacting aminophenol isomers with anhydrides, acid chlorides and esters of polymeric acids with subsequent formylation of the products by dimethylformamide in the presence of phosphorus chloroxide. Using lysin as an example, the catalytic activity of compounds obtained in the racemiza...