Uniform volumetric encapsulation of antimicrobial agents into mesoporous silica for their slow release: the case of copper oxide

Abstract In the present work, a modified Stöber approach was developed for direct encapsulation of copper(II) tetraammine complex solution within the mesopores of SiO 2 particles during their formation. It was shown that a developed synthetic approach allows to uniformly distribute loaded compounds, avoiding their concentration close to the silica particle surface, which is common for post-synthetic techniques of loading. In turn, uniform distribution of copper species led to their slow and sustained release into the surrounding media, both for as prepared and calcined nanocomposites. It was shown that upon 24 h exposure to the solution, the release of copper species proceeds in almost linear fashion without any signs of rate decay. Both as prepared ([Cu(NH 3 ) 4 ] 2+ @SiO 2 ) and calcined (Cu x O@SiO 2 ) nanocomposites demonstrated antibacterial activity against the Gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa , as well as the Gram-positive bacterium Staphylococcus aureus . However, the Cu x O@SiO 2 material appears to be more promising for antimicrobial applications due to its low cytotoxicity to human keratinocytes in vitro .