New antimicrobial materials with cerium ions in the composition of salts, solutions, and composite systems based on Ce3+(NO3)3 × 6H2O

Abstract

The results of detailed characterization of new antimicrobial materials in the form of Ce(NO₃)₃ × 6H₂O salt with the proposed crystal-chemical composition of [Ce³⁺(H₂O)₄(NO₃)₃] × 2H₂O and its aqueous solution by X-ray diffraction (XRD), differential scanning calorimetry (DSC), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS) are presented. The stages of [Ce³⁺(H₂O)₄(NO₃)₃] × 2H₂O thermal decomposition with the formation of [Ce³⁺(H₂O)₄(NO₃)₃] (<220 °C), Ce³⁺ONO₃ (230–320 °C) and Ce⁴⁺O₂ (>300 °C) are shown. It was found that Ce³⁺ ions in the composition of [Ce(H₂O)₄(NO₃)₃] × 2H₂O salt and in its aqueous solution retain their formal charge (FC Ce = 3) and coordination number (CNCe = 10, where 6O from three NO₃⁻ groups and 4O from four 4H₂O molecules) with the reorientation of nitro groups in Ce³⁺ far environment in an aqueous salt solution. It was established that [Ce³⁺(H₂O)₄(NO₃)₃] × 2H₂O, [Ce³⁺(H₂O)₄(NO₃)₃] and Ce³⁺ONO₃ salts inhibit the growth of Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa bacteria in the absence of radiation with a growth zone inhibition diameter D > 37 mm with D_max = 45 mm on the multiphase sample ([Ce³⁺(H₂O)₄(NO₃)₃], Ce³⁺ONO₃, Ce⁴⁺O₂), which is higher than that on penicillin (D = 12–18 mm). It is shown that an increase in the [Ce³⁺(H₂O)₄(NO₃)₃] × 2H₂O salt concentration in an aqueous solution has a positive effect on antimicrobial activity. It is not excluded that the absence of interaction of Ce³⁺ ions in the salt solution with Langmuir phospholipid monolayers of phosphatidylethanolamine (DPPE) and phosphatidylglycerin (DPPG) is associated with the damage to the protein component of the bacterial membrane and not with the phospholipid one and/or with the “penetration” of Ce³⁺ ions into the cell and violation of its water-ionic balance. It is shown that the “H-Beta – Ce³⁺(NO₃)₃ × 6H₂O” system fabrication with biocompatible H-Beta zeolite contributes to the preservation of antimicrobial activity in the dark (Pseudomonas aeruginosa) with a decrease in the amount of the active component.