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

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 24h 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 Gram-negative bacteria Escherichia coli , Pseudomonas aeruginosa , and Gram-positive 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 .