Photocatalytic Degradation\nof Bacterial Lipopolysaccharides\nby Peptide-Coated TiO<sub>2</sub> Nanoparticles

In this study, we report the degradation of smooth and\nrough lipopolysaccharides\n(LPS) from Gram-negative bacteria and of lipoteichoic acid (LTA) from\nGram-positive bacteria by peptide-coated TiO<sub>2</sub> nanoparticles\n(TiO<sub>2</sub> NPs). While bare TiO<sub>2</sub> NPs displayed minor\nbinding to both LPS and LTA, coating TiO<sub>2</sub> NPs with the\nantimicrobial peptide LL-37 dramatically increased the level of binding\nto both LPS and LTA, decorating these uniformly. Importantly, peptide\ncoating did not suppress reactive oxygen species generation of TiO<sub>2</sub> NPs; hence, UV illumination triggered pronounced degradation\nof LPS and LTA by peptide-coated TiO<sub>2</sub> NPs. Structural consequences\nof oxidative degradation were examined by neutron reflectometry for\nsmooth LPS, showing that degradation occurred preferentially in its\nouter O-antigen tails. Furthermore, cryo-TEM and light scattering\nshowed lipopolysaccharide fragments resulting from degradation to\nbe captured by the NP/lipopolysaccharide coaggregates. The capacity\nof LL-37-TiO<sub>2</sub> NPs to capture and degrade LPS and LTA was\ndemonstrated to be of importance for their ability to suppress lipopolysaccharide-induced\nactivation in human monocytes at simultaneously low toxicity. Together,\nthese results suggest that peptide-coated photocatalytic NPs offer\nopportunities for the confinement of infection and inflammation.