Biosynthesis of Peptide Hydrogel-Titania Nanoparticle Composites with Antibacterial Properties

The photoantibacterial properties of titania nanoparticles (TiO(2)NPs) are attracting much interest, but the separation of their suspension limits their application. In this study, the encapsulation of commercial TiO(2)NPs within self-assembling tripeptide hydrogels to form hgel-TiO2NP composites with significant photoantibacterial properties is reported. The Fmoc-Phe(3) hydrogelator was synthesized via an enzymatic method. The resulting composite was characterized with DLS, zeta-potential, SAXS, FESEM-EDS and rheological measurements. Two different concentrations of TiO(2)NPs were used. The results showed that, by increasing the TiO2NP quantity from 5 to 10 mg, the value of the elastic modulus doubled, while the swelling ratio decreased from 63.6 to 45.5%. The antimicrobial efficacy of hgel-TiO(2)NPs was tested against a laboratory Staphylococcus aureus (S. aureus) strain and two methicillin-resistant S. aureus (MRSA) clinical isolates. Results highlighted a concentration-dependent superior antibacterial activity of hgel-TiO(2)NPs over TiO(2)NPs in the dark and after UV photoactivation. Notably, UV light exposure substantially increased the biocidal action of hgel-TiO(2)NPs compared to TiO(2)NPs. Surprisingly, in the absence of UV light, both composites significantly increased S. aureus growth relative to control groups. These findings support the role of hgel-TiO(2)NPs as promising biocidal agents in clinical and sanitation contexts. However, they also signal concerns about TiO2NP exposure influencing S. aureus virulence.