Background and Objective:
The COVID-19 pandemic highlighted the urgent need to find sustainable systems for disinfection, reducing biocides pollution. Titania nanoparticles (TiO2NPs) and their hybrids with inorganic metals, such as silver, revealed antimicrobial activity. TiO2NPs are excellent candidates against bacteria due to their photocatalytic properties: reactive oxygen species are generated in the presence of light. Silver nanoparticles (AgNPs) lead disinfection by releasing Ag+ ions. In the present work, a new nanohybrid through TiO2NPs-AgNPs conjugation was obtained and studied as a combined and synergic antibacterial nano-platform. With this aim, at first, 50 nm TiO2NPs were functionalised with a bifunctional linker, (3-mercaptopropyl)trimethoxysilane (TiO2NPs-MPTMS), through Ti-O-Si bond; subsequently, AgNPs-3MPS (3-mercapto1-propanesulfonate) were prepared _in situ_ and directly attached to the free –SH groups of TiO2NPs-MPTMS surface to form the final TiO2NPs-MPTMS-AgNPs-3MPS nanohybrid.

Materials and Methods:
_In vitro,_ antibacterial properties of TiO2NPs-MPTMS@AgNPs-3MPS were performed under controlled conditions on a gram-negative bacterium, _Escherichia coli_ (105 CFU/mL), and a gram-positive one, _Staphylococcus aureus _(104 CFU/mL), exposed for 25 minutes in the presence of visible light and in the dark.

Results:
Spectroscopic and morphology characterisations demonstrated the successful silanisation of commercial TiO2NPs and AgNPs decoration, supporting their coating on different materials. The synthesized nanohybrids stability, size, morphology, and chemical composition were also demonstrated. _In vitro,_ studies on TiO2NPs showed over 70% reduction in bacterial load. TiO2NPs-AgNPs showed over 99.9% reduction (p=0.05) for both strains, even at a 3 logs dilution of the compounds and regardless of light.

Conclusions:
Photocatalytic systems based on the combination of TiO2NPs with noble metals represent a novel strategy to generate matrices or surfaces with an antimicrobial activity enhanced by light without the need for biocides accumulation. The preliminary results by using TiO2NPs-AgNPs are promising and support further studies to evaluate and optimize kinetics at catalyst desirable concentrations.