Fe(II)-Photoantibioticsfor Potential Antibacterial,Antibiofilm, and Infective Wound Healing Applications in Rat Model

Herein, five Fe(II) complexes, viz., [Fe(<i>N</i>,<i>N</i>,<i>N</i>)₂](ClO₄)₂, where <i>N</i>,<i>N</i>,<i>N</i> = 4′-phenyl-2,2′:6′,2″-terpyridine (Ph-tpy, <b>Fe1</b>), 4′-(4 aminophenyl) 2,2′:6′,2″ terpyridine (NH₂-Phtpy, <b>Fe2</b>), 4-([2,2′:6′,2′′-terpyridin]-4′-yl)-<i>N</i>,<i>N</i>-dimethylaniline (NMe₂-Phtpy, <b>Fe3</b>), 4′-(<i>p</i>-nitrophenyl)-2.2′:6′,2″-terpyridine (NO₂-Phtpy, <b>Fe4</b>), and 4′-(4-trifluoromethylphenyl)-2,2’:6′,2′′-terpyridine (CF₃-Phtpy, <b>Fe5</b>) were developed and screened for their visible-light-triggered antibacterial activity. <b>Fe1</b>–<b>Fe5</b> exhibited absorption at <i>ca</i>. 450–600 nm, beneficial for antibacterial photodynamic therapy (aPDT) under visible light exposure. The excellent photostability and ideal energy gap between T₁ and S₀ of the complexes made them good photosensitizers for aPDT. <b>Fe5</b> had the best antibacterial activity against <i>Escherichia coli</i> and <i>Bacillus subtilis</i> upon exposure to 400–700 nm (10 J cm^–2) light due to reactive oxygen species (ROS) generation. Further, <b>Fe5</b> showed antibiofilm activity on different medical-grade biomaterials and devices. Biocompatibility of <b>Fe5</b> was validated using <i>in vivo</i> and chicken embryonic models (<i>in ovo</i>). Moreover, <i>in vivo</i> studies showed that <b>Fe5</b> efficiently healed infected wounds within 9 days.