Copper(II)-containing chitosan-based non-toxic composites stimulate kefir grain biomass propagation: Combined in vitro and in vivo studies

Chitosan-based systems exhibit attractive physical, chemical, and biological properties. In this study, we designed innovative Cu(II)/Chitosan-based systems: (1) the simplest Cu(II)/Chitosan blended composites, (2) the hyaluronate-covered, (3) cholesterol containing, (4) the simplest succinated, and (5) the hyaluronate-covered succinated ones. The blending of Cu2+ and succinated chitosan (4) or succinated chitosan covered by hyaluronate (5) stimulated kefir grain propagation. The most significant stimulation effect was observed in the case of succinated hyaluronate covered Cu(II)/Chitosan-based systems (5), unequivocally identified as the most effective. The observed phenomenon was attributed to the symbatic action of Cu(II) cations and polymeric matrices. Furthermore, we conducted evaluations of the in vitro and in vivo toxicity of the composites. The cholesterolcontaining systems (3) were found to be the most in vitro toxic, while hyaluronate-covered succinated composites (5) demonstrated minimal toxic effect toward living cells HEK-293. The leading composites also demonstrated low in vivo acute and subacute toxicity which allowed us to refer them to the IV class of hazard (low-toxic substances). Due to their low toxicity and remarkable ability to stimulate kefir grain biomass growth, the leading composites are of interest for further exploration, particularly in the food industry.