Bacteria Single-Cell and Photosensitizer Interaction Revealed by Quantitative Phase Imaging

Area of Science:

• Biophysics
• Microbiology
• Medical Imaging

Background:

• Quantifying bacterial cell changes during antibacterial treatment is challenging, especially for biofilms which reduce susceptibility to biocides.
• Current 3D label-free imaging methods for bacteria-photosensitizer interactions in antimicrobial photodynamic therapy (aPDT) are limited.

Purpose of the Study:

• To present a novel method for investigating cellular alterations and quantitatively analyzing bacterial photodynamic inactivation.
• To demonstrate the capability of Digital Holographic Tomography (DHT) for real-time, label-free characterization of subcellular structures and biophysical processes.

Main Methods:

• Digital Holographic Tomography (DHT) was employed for in situ examination of *Escherichia coli* and *Staphylococcus aureus* response to photosensitizers.
• Changes in 3D refractive index distributions within single cells revealed photosensitizer accumulation.
• Results were validated using confocal microscopy and statistical analysis.

Main Results:

• DHT enabled real-time characterization of subcellular structures and biophysical processes in bacteria.
• The method quantitatively analyzed intracellular density changes induced by photosensitizers.
• Sub-micrometer spatial resolution was achieved in a label-free manner.

Conclusions:

• DHT provides a powerful tool for label-free, quantitative analysis of bacterial responses to antimicrobial treatments.
• This technique advances the study of bacteria-photosensitizer interactions crucial for antimicrobial photodynamic therapy.
• DHT offers real-time insights into cellular biophysical changes at high resolution.