Chemically Modulating Ceria-Based Artificial Haloperoxidase for Enhanced Antibacterial Activity and Biofilm Inhibition

Ceria (CeO 2 ) nanoparticles with haloperoxidase (HPO)-like activity have gained attention as a biologically benign antifoulant. 3,4-Dihydroxy- l -phenylalanine (DOPA), a main composition in mussel foot proteins, plays a crucial role in the biofouling process. However, the impact on the HPO-like activity and antifouling performance of CeO 2 nanoparticles when DOPA molecules adsorb on them remains unexplored. This interesting question warrants investigation, particularly considering that it may occur in an actual marine environment. Herein, the interaction between DOPA and CeO 2 is explored. Despite the higher Ce 3+ fractions and the lower band gap energies due to the electron transfer from DOPA to the CeO 2 surface, DOPA still had a slightly negative effect on the HPO-like activity of CeO 2 since they decreased the exposed Ce 3+ sites. The DOPA-CeO 2 nanocomposites with HPO-like activities could kill bacteria and trigger quorum-sensing signaling quenching, achieving a biofilm inhibition performance. Amazingly, 0.1% DOPA-CeO 2 nanocomposite exhibited higher antibacterial activity and better biofilm suppression activities due to its HPO-like activity and positive zeta potential. The remarkable results demonstrated that DOPA, as a participant in the biofouling process, could enhance the antibacterial activity and antifouling performance of CeO 2 nanoparticles at an appropriate concentration.