Complexation of oligochitosan with sodium caseinate in alkalescent and weakly acidic media

Viability and Surface Morphology of Human Erythrocytes upon Interaction with Chitosan Derivatives

The viability and surface morphology of human erythrocytes upon interaction with oligochitosan (OCH), having a molecular weight (MW) of 6.2-15.4 kDa and a degree of acetylation (DA) of 1-2%, and interaction with N-reacetylated OCH (ROCH) with a 6.4-14.3 kDa MW and 24-30% DA were studied in isotonic saline phosphate buffer with pH 7.4. It was shown that the use of OCH caused high hemolysis and irreversible transformation of the erythrocytes. Thus, OCH having a 6.2 kDa MW and 1% DA, used at a 0.01% concentration, induced high hemolysis of erythrocytes, and their viability did not exceed the maximal value of 60%. Among the nonhemolyzed erythrocytes, about 20% reversibly transformed erythrocytes and about 20% irreversibly transformed erythrocytes were observed in comparison with the control experiments. For the first time, it was shown that ROCHs had a much lower impact on the cells. Thus, about 82% of the erythrocytes had a discoid form, while 12% and ∼6% of the cells underwent reversible and irreversible transformations, respectively, in the presence of ROCH (MW 6.4, DA 24%), used at a 0.01% concentration. It was observed that an increase in the MW and concentration of chitosan derivatives led to a decrease in the cell viability. It was supposed that the complexation of chitosan derivatives with phosphate counterions in the buffer might reduce the impact of chitosan derivatives on the viability and surface morphology of erythrocytes due to a reduction in the average zeta-potential of chitosan derivative/phosphate complexes from positive to negative values. These results supported the suggestion that reacetylation and reduction of the overall charge of chitosan molecules could improve the compatibility of chitosan derivatives with erythrocytes. This finding opens an opportunity for the construction of chitosan derivatives and their complexes that are compatible with other blood forming elements.

Interaction between reacetylated chitosan and albumin in alcalescent media

Interaction of chitosan and its derivatives with proteins of animal blood at blood pH relevant conditions is of a particular interest for construction of antimicrobial chitosan/protein-based drug delivery systems. In this work, the interaction of a series of N-reacetylated oligochitosans (RA-CHI) having Mw of 10-12 kDa and differing in the degree of acetylation (DA 19, 24, and 40 %) with bovine serum albumin (BSA) in alkalescent media is described in first. It is shown that RA-CHI forms soluble complexes with BSA in solutions with pH 7.4 and a low ionic strength. Light scattering study shows that soluble RA-CHI complexes have spherical form with the radius of about 100 nm. Circular dichroism, fluorescent spectroscopy, and micro-IR spectroscopy studies show that the secondary structure of BSA in soluble complexes remain intact. Isothermal titration calorimetry of RA-CHI with DA 24 % and BSA mixing in the buffers with different ionization heats reveals a significant contribution of electrostatic forces to the binding process and an additional ionization of chitosan due to the proton transfer from the buffer substance. An increase of ionic strength to the blood relevant value 0.15 M suppresses the binding. It is shown that application of RA-CHI with higher DA value leads to a decrease in the affinity of RA-CHI to BSA and an alteration of the interaction mechanism. The finding opens an opportunity to the application of N-reacetylated chitosan derivatives in the complex systems compatible with blood plasma proteins.

Exploiting specific properties of squid pens for the preparation of oligochitosan hydrochloride

Herein, we describe in first the application of squid pens for the preparation of pharmaceutical-grade oligochitosan hydrochloride with the physicochemical characteristics corresponding with the requirements of the European Pharmacopoeia. It is shown that the use of specific properties of squid pens as a source of parent chitosan allows preparing the product with a high yield at relatively moderate process conditions used for squid pens treatments and chitosan depolymerization.

An insight into the effect of interaction with protein on antibacterial activity of chitosan derivatives

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 Kb determined for CH/CAS and RCH/CAS complexes at pH 6.0 were equal to 29.8 × 106 M-1 and 8.9 × 106 M-1, respectively. Kb 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.