Characterization of H3PO4/HNO3–NANO2 oxidized bacterial cellulose and its usage as a carrier for the controlled release of cephalexin

Biocompatibility, biodegradation, good sorption characteristics, and unique structure of highly oxidized bacterial cellulose (OBC) are of great interest for the development of new drug delivery systems. In this study, OBC with 9.6, 13.0 and 19.5% carboxyl groups for 5, 20, and 48 h of synthesis, respectively, was successfully obtained using the HNO₃/H₃PO₄–NaNO₂. The results of morphological analysis showed that with an increase in the number of carboxyl groups, OBC fibers become thicker and rougher. Fourier-transform infrared spectroscopy showed the formation of carboxyl groups in the OBC after the oxidation reaction. The crystallinity of the samples according to X-Ray diffraction analysis decreased with increasing reaction time. The immobilization of cephalexin in the polymer matrix was studied in detail, it took 120 min to achieve balance in the solution with a concentration of 1 mg/ml, and the maximum amount of a sorbed antibiotic reached 43 mg/g. The drug release in vitro at 37 °C in PBS with pH 7.4 and 2.0 was prolonged. Various models were used to describe the release mechanism, the best of which was Ritger-Peppas with a diffusion exponent value ranging from 0.743 to 0.830, which explains the drug release mainly through non-Fickian diffusional release. The cephalexin-loaded OBC showed high antimicrobial activity against Gram-negative bacteria Escherichia coli and Gram-positive bacteria Staphylococcus aureus. The structure and properties of the resulting highly oxidized cellulose make it an excellent candidate as a drug delivery carrier with prolonged antimicrobial drug release characteristics.

     

Influence of the properties of modified dextran hydrogel polymer network on the kinetics of the release of prospidin antitumor agent

The influence exerted by the conditions of the synthesis of dextran phosphate hydrogels in the orthophosphoric acid–urea system on their functional composition and swellability in water was studied. The main parameters of the polymer network, namely, the mean molecular mass of segments between cross-linking points, the pore size, and the cross-linking density, were determined. Samples of prospidin immobilized on dextran phosphate hydrogels were prepared, and the kinetics of the cytostatic release into phosphate buffer solution (pH 7.4) was studied in relation to the functional composition and parameters of the polymer network of the support. The prospidin release from dextran phosphate hydrogels is due both to diffusion processes and to breakdown of the polymer network of the hydrogel.     

Sorption of the antitumor drug prospidinum on microgels of polysaccharide phosphates

The intermolecular interaction of prospidinum with gel-forming dextran and starch phosphates has been studied. The sorption equilibria have been studied for cytostatic and the biodegradable hydrogels of polysaccharide phosphates. The concentration coefficients of ion exchange equilibrium and distribution coefficients of prospidinum have been calculated at different degrees of microgel phase filling with the cytostatic, and the relations between the coefficients and the degree of hydrogel swelling have been determined. The ion-exchange and nonexchange contributions to sorption values have been found. The analysis of the distribution coefficients has demonstrated that the concentration of prospidinum sorbed through the nonexchange mechanism is higher than its concentration in an external solution due to the van der Waals interactions between prospidinum cations and macromolecules of polysaccharide phosphates. The Na form of polysaccharide phosphates is the optimal carrier for prospidinum, because this form has a higher density of the total negative charge than their H form has.