Ferric Ions as a Catalytic Mediator in Metal-EGCG Network for Bactericidal Effect and Pathogenic Biofilm Eradication at Physiological pH

Pathogenic bacteria and biofilm formation have become the urgent threats to global public health. Herein, metal-epigallocatechin gallate (EGCG) network with improved bactericidal effect and pathogenic biofilm eradication ability via trivalent cationic Fe 3+ catalyzed hydrogen peroxide (H 2 O 2 ) decomposition is developed. EGCG, the predominant catechin from tea, is predicted to be a good chelator for eight metal ions (i.e., Al 3+ , Cr 3+ , Cu 2+ , Co 2+ , Zn 2+ , Mn 2+ , Ni 2+ , Fe 3+ ). 3,3',5,5'-tetramethylbenzidine oxidation experiment using UV–vis spectrometer demonstrated that Zn 2+ , Mn 2+ , Ni 2+ are the potential candidates to accelerate the generation of H 2 O 2 by EGCG. Compared with the other two metal-EGCG network (Zn 2+ -EGCG or Mn 2+ -EGCG), only Ni 2+ -EGCG network has better bactericidal property and plays a synergistic role in the network system. Furthermore, by introducing Fe 3+ to Ni 2+ -EGCG network, the complex exhibits the best bactericidal property for gram-negative bacteria Escherichia coli ( E. coli ) and Pseudomonas aeruginosa (PAO1), which can be explained by the rapid H 2 O 2 decomposition and associated production of hydroxyl radicals. With SYTO 9/PI staining assay, Fe 3+ as a catalytic mediator in Ni 2+ -EGCG network shows the most significant bactericidal effect and pathogenic biofilm eradication ability. According to the above analysis, Ni 2+ -EGCG network presents a promising nanoplatform as an alternative to antibiotics for eradication of pathogenic bacteria and biofilms.