The present invention relates to a dioxide silicon or titanium derivative of formula (I): (MO2)&minus；(Am+)y, as active ingredient for the preparation of a composition having antibacterial properties useful, e.g. for topical administration. The dioxide derivatives of the present invention comprises anionic silica (SiO2)n&minus； or anionic titanium dioxide particles (TiO2)n&minus；, adsorbed with at least one cationic pharmaceutical active moiety (Am+), which may include, for instance, known antibacterial agents such as chlorexidine and the like. Furthermore, the invention relates to a composition for topical use, which may form an efficacious barrier against external microbes, substantially avoiding any infection on the affected skin.
