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Antimicrobial activity of chitosan in protein-rich media is of a particular interest for various protein-based drug delivery and other systems. For the first time, bacteriostatic activity of chitosan derivatives in the presence of caseinate sodium (CAS) was studied and discussed. Complexation of chitosan derivatives soluble in acidic (CH and RCH) or alkalescent (RCH) media with CAS was confirmed by fluorescent spectroscopy, turbodimetry, light scattering data and measurement of electrical potentials of CAS/chitosan derivative complexes. An addition of CH and RCH caused a static quenching of CAS. Binding constants K b determined for CH/CAS and RCH/CAS complexes at pH 6.0 were equal to 29.8 × 10 6 M−1 and 8.9 × 106 M−1, respectively. K b value of RCH/CAS complex at pH 7.4 was equal to 1.1 × 105′M−1. The poisoned food method was used for counting the number and the direct measurement of the size of bacterial colonies on the surfaces of turbid agar media containing CAS/chitosan derivative complexex. Complete suppression of E. coli cells growth and restriction of S. aureus cells growth were observed on the surface of acidic media. A high concentration of CAS reduced the activity. The activity of RCH in alkalescent media is low or absent. These results can be promising for preparation of microbiologically stable protein-based drug delivery systems. • Bacteriostatic activity of chitosan derivatives in protein media is studied. • Binding constants of chitosan derivatives with caseinate sodium are determined. • In acidic medium, chitosan derivatives show a high bacteriostatic activity. • Bacteriostatic activity is very low or absent in alkalescent protein media. • Modified poisoned food method is used to determine the activity in turbid media. [ABSTRACT FROM AUTHOR]

Abstract—: Insolubility of chitosan and oligochitosan in aqueous media above pH 6.2-6.5 and the resulting decreased penetration thorough mucosa restricts significantly their application in biomedical compositions. To create non-cytotoxic chitosan derivatives with a high antibacterial activity in weakly alkaline physiological media, alkali-soluble derivatives of oligochitosan and low-molecular weight chitosan were synthesized by coupling a betaine substituent to the nitrogen atom of glucosamine units. Comparative studies of the pH range of the solubility of these derivatives depending on the chain length and modification degree of oligochitosan with Mw = 9.7 ± 1.7 kDa were carried out. It was found that 12 mol % of betaine substituents was the optimal modification degree ensuring the existence of a single-phase solution of modified oligochitosan (Mw = 2-10 kDa) within the entire pH range. Investigation of the antibacterial activity of betaine derivatives against gram-positive (S. aureus) and gram-negative (E. coli) bacteria revealed their high antibacterial effect in both weakly acidic and weakly alkaline environments. Betaine derivatives were found to be nottoxic towards cow lung epithelial cells (LEC) at concentrations below 2.5 mg/mL. The results obtained seem promising for the application of these derivatives in biomedical compositions. [ABSTRACT FROM AUTHOR]

Oligochitosan (short chain chitosan) is more soluble in acidic aqueous media than a high molecular weight (MW) chitosan, but its antimicrobial activity decreases with increase in degree of acetylation (DA) and increase in pH above a critical pH threshold point. In the present study, oligochitosans varying in MW were additionally N-acetylated and their self-assembly properties and antibacterial activity toward Staphylococcus aureus and Escherichia coli were investigated in a wide pH range as a function of MW and DA. Light scattering studies reveals that reacetyleted oligochitosan with Mw ≤ 11 kDa is completely soluble in alkaline media (up to pH 12.5), if its DA is not less than 16%. Reacetylated chitosans with DA ∼ 30% are solubile in the entire pH range up to 12.5, if their Mw is not higher than 25 kDa, but they aggregate and precipitate from the solution at pH ≥ 8 when their Mw is above 25 kDa. Considering the influence of DA and MW, the antibacterial activity of reacetylated oligochitosans is maximal in the short interval of DA 16–28% at pH 7.4. These results are promising for expanding practical application of oligochitosan in pharmaceutical, cosmetic, and food compositions. [ABSTRACT FROM AUTHOR]

Abstract: A series of oligochitosans (short chain chitosans) prepared by acidic hydrolysis of chitosan and characterized by their molecular weight, polydispersity and degree of deacetylation were used to determine their anticandidal activities. This study has demonstrated that oligochitosans show a high fungistatic activity (MIC 8–512 μg/ml) against Candida species and clinical isolates of Candida albicans, which are resistant to a series of classic antibiotics. Flow cytometry analysis showed that oligochitosan possessed a high fungicidal activity as well. For the first time it was shown that even sub-MIC oligochitosan concentration suppressed the formation of C. albicans hyphal structures, cause severe cell wall alterations, and altered internal cell structure. These results indicate that oligochitosan should be considered as a possible alternative/additive to known anti-yeast agents in pharmaceutical compositions. [Copyright &y& Elsevier]

It was shown that low-molecular chitosan could be fractioned by ultrafiltration. The types of membranes suitable for this purpose were determined. The effect of ionic strength and the solvent nature on the molecular weight and polydispersity of the obtained samples was studied. The possibility of obtaining chitosan with low polydispersity was shown. [ABSTRACT FROM AUTHOR]

The possibility of obtaining monosaccharide derivatives of low-molecular-weight chitosan with the use of the Maillard reaction was studied. Chitosan derivatives (molecular weight, 24 and 5 kDa) obtained with glucosamine, N-acetyl galactosamine, galactose, and mannose with a substitution degree of 4–14% and a yield of 60–80% were obtained. Some physicochemical and biological properties of these derivatives were studied. We showed that monosaccharide derivatives of low-molecular-weight chitosan exhibited antibacterial activity. Chitosan at a concentration of 0.01% caused 100% death of bacteria B. subtilis and E. coli. The strongest antibacterial effect was exhibited by 24-kDa derivatives: only 0.02–0.08% of cells survived. These derivatives were two orders of magnitude more effective than the 5-kDa chitosan modified with galactose. [ABSTRACT FROM AUTHOR]

N‐reacetylated oligochitosan (RA‐oligoCHI) with molecular weight ≤ 12 kDa and a random‐type distribution of acetyl groups can form soluble RA‐CHI/SDS (SDS; sodium dodecyl sulfate) 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 concentration. AN antibacterial activity test shows that RA‐CHIs preserve a high bacteriostatic activity toward S. aureus and E. coli in the presence of SDS both in acidic and alkaline aqueous solutions. The discovered compatibility and preservation of antibacterial activity can make promising the application of RA‐CHIs as artificial biocides for the preparation of microbiologically stable pharmaceutical hydrocolloids and cosmetic compositions containing strong anionic surfactants designed for topical applications. [ABSTRACT FROM AUTHOR]

It is well known that chitosan degradation by nitrous acid leads to oligochitosan (oligoCHI t –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 oligoCHI t –ahm with NaBH 4 to corresponding oligoCHI t –hml bearing unreactive hydroxymethyl group instead of reactive aldehyde group. For the first time, HP SEC as well as UV and CD spectroscopy methods have revealed that the reduction leads to an indefinite side modification and the formation of a branched oligoCHI t -hml with increased molecular weight. Here, it is shown that the branching and modification can be prevented by means of the simple and reproducible reaction of oligoCHI t –ahm with hydroxylamine that allows preparation of a stable linear oligochitosan oxime, oligoCHI t –oxm. Cytotoxicity tests show that oligoCHI t –ahm, oligoCHI t –hml and oligoCHI t –oxm are non-toxic at concentration below 2.5 mg/ml, and the cytotoxicity is concentration dependent and decreases in the order oligoCHI t –ahm > oligoCHI t –hml > oligoCHI t –oxm at higher concentrations both before and after long shelf-storage. The elaborated approach and cytotoxicity data give an opportunity to use the non-branched oligoCHI t –oxm for biomedical applications. [ABSTRACT FROM AUTHOR]

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 alkalescent system, the formation of only soluble complexes is observed at OCHI/SC ratio ≤0.9. In the semi diluted one, the complexation results in the formation of insoluble complexes those composition changes symbatically with the OCHI/SC ratio in the system. At pH 5.8, OCHI/SC ratio in insoluble complexes remains the same regardless of OCHI/SC ratio in the solution. At pH 5.8, the electrostatic complexation weakens with an increase in DA and is completely suppressed at a high ionic strength. These results can be promising for construction of biodegradable protein/chitosan drug delivery systems. [Display omitted] [ABSTRACT FROM AUTHOR]

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 temperature on microparticles formation allows interpreting the mechanism of microparticles formation as a cooperative electrostatic interaction between SDS and chitosan with simultaneous decrease in the surface charge of the complexes initiating the aggregation of microparticles. It is shown that hydrogen bonding is mainly responsible for the aggregation while hydrophobic interaction has a lesser effect. Chitosan demonstrates a high bacteriostatic activity in the presence of SDS in solution and can be promising for preparation of microbiologically stable pharmaceutical hydrocolloids, cosmetic products and chitosan-based Pickering emulsions containing strong anionic surfactants. [Display omitted] • A decrease in molecular weight favors chitosan complexation with sodium dodecyl sulfate (SDS). • The size of SDS/chitosan microparticles increases with decrease in molecular weight of chitosan. • Hydrogen bonds are mainly responsible for formation of SDS/chitosan complex microparticles. • An increase in temperature leads to disruption of hydrogen bonds and SDS/chitosan microparticles. • Chitosan demonstrates a high bacteriostatic activity in the presence of SDS. [ABSTRACT FROM AUTHOR]