Near-infrared Aza-BODIPY Dyes Through Molecular Surgery for Enhanced Photothermal and Photodynamic Antibacterial Therapy

The widespread use of high-dose antibiotics will not only lead to the rapid acquisition of antibiotic resistance and increased incidence of drug-resistant bacterial infections, but also produce toxic side effects on normal tissues. Herein, two near-infrared dyes BDP-4PTZ and BDP-4DPA were synthesized, and the electron donors of diphenylamine and phenothiazine with the only difference of sulphur(S)-lock between the two phenyl rings were introduced onto the electron acceptor aza-dipyrromethene boron difluoride(aza-BODIPY) through molecular surgery. Through co-precipitation into nanoparticles(NPs), BDP-4PTZ NPs and BDP-4DPA NPs were fabricated with good biocompatibility. Upon 660 nm photoirradiation, BDP-4PTZ NPs and BDP-4DPA NPs showed excellent photothermal conversion efficiency(43% and 50%, respectively) and reactive oxygen species(ROS) production performance(ca. 3.6 and 6 times higher than that of indocyanine green, respectively). In vitro antibacterial experiments indicated that both NPs could effectively destroy the bacteria’s membrane to eradicate drug-resistant bacteria. Furthermore, the bacterial abscess was effectively eliminated after treatment with BDP-4DPA NPs under 660 nm photoirradiation without adverse effects. Thus, through molecular surgery, BDP-4DPA without the S-lock demonstrates synergistic photothermal and photodynamic antimicrobial activities, which is promising for further molecular design towards effective neo-antimicrobial phototherapy.