Theranostic FRET Gate to Visualize and Quantify Bacterial Membrane Breaching

Area of Science:

• Biomaterials Science
• Microbiology
• Chemical Biology

Background:

• Developing real-time bacterial membrane breaching probes is crucial for infectious disease treatment.
• Aggregation-induced emission (AIE) polymers offer potential as antimicrobial theranostics.
• Crystal violet (CV) can be used as an acceptor in fluorescence resonance energy transfer (FRET) probes.

Purpose of the Study:

• To design and synthesize novel AIE polymers as antimicrobial gatekeepers.
• To construct FRET probes for visualizing bacterial membrane permeabilization.
• To develop an image-based assay for quantifying bactericidal activity.

Main Methods:

• Synthesis of AIE-active tetraphenylethylene (TPE)-tagged polycaprolactone polymers with varying charges (neutral, anionic, cationic).
• Self-assembly of AIE polymers into nanoparticles acting as gatekeepers for FRET probes.
• Construction of bacterial membrane-reinforced FRET probes utilizing AIE polymers and CV.
• Confocal microscopy to observe FRET activation and quantify bactericidal activity in *Escherichia coli*.

Main Results:

• Cationic AIE polymers successfully adhered to Gram-negative bacterial membranes, triggering probe activation and FRET signal.
• Neutral and anionic AIE polymers did not breach the membrane, resulting in no FRET signal.
• A visualization-based FRET assay was established for quantifying bactericidal activity.

Conclusions:

• Cationic AIE polymers serve as effective antimicrobial gatekeepers for bacterial membrane breaching.
• The developed FRET probes enable real-time visualization and quantification of antimicrobial activity.
• This approach offers a promising tool for studying bacterial membrane interactions and developing new antimicrobial strategies.