"Titanium dioxide (TiO2) is a semiconductor material that exhibits antibacterial activity due to its photocatalytic properties under ultraviolet light. On the other hand, silver also exhibits strong antibacterial activity towards a wide range of microorganisms and TiO2 with silver addition exhibits more efficient photocatalytic properties than unmodified TiO2. In this work, TiO2 nanoparticles were synthesized by the hydrothermal method and modified with silver by two different methods: wet impregnation (Ex situ) and In situ incorporation. The antimicrobial activity of TiO2 nanoparticles synthesized and modified by both methods was evaluated against Escherichia coli and Staphylococcus aureus. The results showed that TiO2 nanoparticles have anatase phase. Also, spherical morphology with a mean particle size around 10.6 nm was obtained. The presence of silver in the modified TiO2 nanoparticles was confirmed by EDS and XPS. TiO2 particles modified by the Ex situ method, showed a better bactericidal activity compared to the particles modified by In situ incorporation method and TiO2 unmodified nanoparticles. This study demonstrated that both methods used to modify the titanium dioxide nanoparticles are effective as bactericidal materials and better results were found for the Ex situ method."