Genetically Encoded Photosensitizers as Light-Triggered Antimicrobial Agents

Area of Science:

• Biochemistry
• Microbiology
• Photochemistry

Background:

• Multi-drug resistant pathogens pose a significant global health threat.
• Novel antimicrobial strategies are urgently required to combat resistant bacteria.
• Genetically encoded photosensitizers (PS) offer a potential light-triggered therapeutic approach.

Purpose of the Study:

• To evaluate genetically encoded photosensitizers (PS) derived from green fluorescent protein (GFP) and light-oxygen-voltage (LOV) photoreceptors as antimicrobial agents.
• To investigate the photophysical properties and reactive oxygen species (ROS) generation of these PS for antibacterial applications.
• To compare the efficacy of intracellular and extracellular application of PS for bacterial inactivation.

Main Methods:

• Analysis of genetically encoded photosensitizers (PS) related to GFP and LOV photoreceptors.
• Assessment of ROS production (O2•−, H2O2, 1O2) via type-I and type-II reactions upon light exposure.
• Cell viability assays and microfluidics to determine intracellular and extracellular phototoxicity.
• Evaluation of bacterial inactivation rates for E. coli and other pathogenic bacteria.

Main Results:

• GFP-related PS showed slow bacterial inactivation, both intracellularly and extracellularly.
• LOV-based PS, like SOPP3, achieved rapid and homogeneous killing of Gram-negative and Gram-positive bacteria.
• The type and yield of ROS, along with PS localization, significantly influenced antibacterial spectrum and efficacy.

Conclusions:

• Genetically encoded photosensitizers, particularly LOV-based ones, show promise as effective light-triggered antimicrobial agents.
• Photodynamic inactivation using tailored PS offers a new strategy against multi-drug resistant bacteria.
• Understanding ROS generation and PS localization is key to optimizing photodynamic antibacterial therapies.