Evaluation of the Sorption Capacity of Functionalized Bacterial Cellulose Gel Films with Respect to Chloramphenicol

Due to unique natural characteristics such as biocompatibility, nontoxicity, mechanical stability, and high moisture content, bacterial cellulose can be efficiently used for the production of new medical materials, including various wound dressings. Bacterial cellulose can be produced by bacteria of the genera Gluconaceto-bacter, Aerobacter, Rhizobium and others. Under static cultivation conditions, the producers form gel films of bacterial cellulose, which differ in their properties. Bacterial cellulose does not possess inherent antimicrobial activity; therefore, bacterial cellulose films must be further enhanced before they are used as medical materials. In order to improve the properties of BC, researchers use various modification methods to introduce antimicrobial activity. The main attention is paid to the post-synthetic modification: in this concept, in order to impart antimicrobial properties to bacterial cellulose it is saturated with antibiotics or other antibacterial and antifungal drugs. To improve the sorption properties, successful attempts were made to oxidize BC and then to saturate it with an antibiotic. The introduction of new reactive functional groups to the surface of bacterial cellulose fibers will make it possible to better control the sorption process and increase the saturation of films with antibacterial drugs. The purpose of this work was to determine the effect of bacterial cellulose treatment during oxidation in the TEMPO/NaClO/NaBr system on the properties of oxidized samples, i.e., an increase in the sorption capacity with respect to a biologically active compound. Films were obtained under conditions of stationary cultivation of the strain Gluconacetobacter hansenii GH 1/2008 (VKPM B-10547) on glucose and fructose carbon sources. Chloramphenicol, a broad-spectrum antibiotic, was chosen as a model antibiotic with which the films were saturated. The resulting films did not differ significantly in terms of thickness, water-holding capacity, and dry weight (see Table 1). Derivatives of BC gel films were obtained without destroying the native three-dimensional gel structure using an oxidative process catalyzed by the nitroxyl radical TEMPO (2,2,6,6-tetramethylpiperidin-1-yl)oxyl). Depending on the oxidation conditions, a series of gel films functionalized with carboxyl groups (COOH) were obtained with a total content of COOH groups varying in a wide range from 0.041 to 0.219 mmol/g (see Fig. 2В). It was shown for the first time that the content of COOH groups depends on the quality of films synthesized on various carbon sources: the maximum degree of carboxylation was noted for films synthesized by G. hansenii on fructose, which is apparently associated with differences in the supramolecular structure of cellulose (see Fig.2B and 3). For the obtained gel films, the sorption capacity with respect to the antibacterial drug chloramphenicol (CP) was evaluated. A direct relationship was established between the sorption value and the amount of COOH groups in the films. The amount of sorption of the antibiotic depends on the degree of carboxylation of the sample (see table 3). Thus, the functionalization of the surface of bacterial cellulose gel films with carboxyl groups leads to an increase in their sorption properties. Indeed, the amount of antibiotic absorbed by the oxidized films is several times higher as opposed to the non-oxidized gel films. The obtained results demonstrate the benefits of carrying out the process of oxidation of bacterial cellulose films, increasing the degree of their saturation with antimicrobial agents and the possibility of their further use for medical purposes as a dressing material. The article contains 7 Figures, 3 Tables and 26 References.