Organic-inorganic hybrids containing cerium and silver compounds: nanostructure evolution during release and antibacterial activity

Full text: Urea crosslinked siloxane-polyethylene oxide (U-PEO) hybrids are promising matrices for the incorporation and controlled delivery of bioactive agents [1]. The incorporation of antibacterial agents into the U-PEO matrix is of particular interest since the need of surfaces with antibacterial properties concerns various technological fields such as the biomedical one. Cerium, in the form of oxide (CeO₂) or as salt (nitrate) has been reported to inhibit bacterial growth. Silver nanoparticles and more generally silver based compounds are well known to have inhibitory and bactericidal effects through the formation of silver ions. However, the incorporation of silver compounds into the U-PEO hybrid often leads to opaque matrices, susceptible to suffer coloration changes, due to the photo-instability of silver ions. With the aim to synthesize novel transparent and photostable U-PEO hybrids showing antibacterial properties, combinations of cerium and silver compounds were incorporated into the U-PEO. Two parameters were studied: the molar concentration of silver related to the total amount of guest cations in the matrix and the nature of the cations source: nitrates salts vsCeO₂ colloidal suspension containing silver. The U-PEO hybrids were synthesized by the sol-gel process and the salts mixture or colloidal suspensions were incorporated during the hydrolysis. The hybrids remained transparent until 10 % of silver. The antibacterial agent release was monitored by UV-vis spectroscopy. The hybrids nanostructure evolution was studied in situ by SAXS during their swelling. The antibacterial activity of the hybrids was evaluated by turbidimetry assay. All the loaded hybrids displayed antibacterial activity against the Pseudomonas aeruginosa bacteria. The antibacterial activity was found to increase with the silver concentration. References [1] E. F. Molina, S. H. Pulcinelli, C.V. Santilli and V. Briois, J. Phys. Chem. B, 114, 3461 (2010). (author)