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

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