Reactivity Differences Enable ROS for Selective Ablation of Bacteria.

Area of Science:

• Photodynamic therapy
• Antimicrobial strategies
• Chemical biology

Background:

• Developing selective photodynamic agents to combat bacterial infections, particularly Gram-positive strains, is a significant challenge.
• Existing methods often lack specificity, leading to collateral damage to host cells or beneficial bacteria.

Purpose of the Study:

• To engineer novel photodynamic agents with distinct reactive oxygen species (ROS) generation profiles for selective bacterial ablation.
• To demonstrate the proof-of-concept for differential ROS generation in targeting Gram-positive bacteria.

Main Methods:

• Synthesis of sulfur-substituted (NBS-N) and selenium-substituted (NBSe-N) phenoxazinium compounds.
• Evaluation of ROS generation (superoxide anion radical vs. singlet oxygen) by the synthesized compounds.
• Assessment of bacterial killing efficacy against Gram-positive and Gram-negative bacteria using fluorescence imaging and morphological analysis.
• In vivo efficacy testing of NBS-N in a mouse model of Gram-positive bacterial infection.

Main Results:

• NBS-N primarily generated superoxide anion radicals, selectively killing Gram-positive bacteria.
• NBSe-N produced higher levels of singlet oxygen, effective against both Gram-positive and Gram-negative bacteria.
• Bacterial fluorescence imaging and morphological changes confirmed the selective and differential bacterial ablation.
• NBS-N demonstrated successful healing of Gram-positive bacterial-infected wounds in mice.

Conclusions:

• Differential ROS generation by tailored photodynamic agents can achieve selective Gram-positive bacterial eradication.
• The developed strategy offers a promising approach for designing targeted antimicrobial therapies.
• This work paves the way for new photodynamic agents to address Gram-positive bacterial infections.