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Updated: Jun 25, 2026
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An In Vitro Approach to Photodynamic Therapy
Published on: August 17, 2018
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Efficient and Selective, In Vitro and In Vivo, Antimicrobial Photodynamic Therapy with a Dicationic Chlorin in
Anita S Amorim1, Zoe A Arnaut1, Ana I Mata1
1CQC-IMS, Chemistry Department, University of Coimbra, Coimbra 3004-535, Portugal.
ACS Infectious Diseases
|August 16, 2024
Summary
Antimicrobial photodynamic therapy (aPDT) can now effectively treat bacterial biofilms and infections using a novel chlorin photosensitizer potentiated by potassium iodide (KI). This approach significantly reduces toxicity to host cells, enabling selective biofilm inactivation and controlling localized infections in vivo.
Area of Science:
- Photochemistry
- Antimicrobial Therapy
- Bacteriology
Background:
- Cationic photosensitizers in antimicrobial photodynamic therapy (aPDT) effectively inactivate planktonic bacteria but require high, toxic concentrations for biofilms.
- Antimicrobial resistance (AMR) is a growing concern, necessitating novel therapeutic strategies.
Purpose of the Study:
- To investigate a dicationic di-imidazolyl chlorin for photoinactivation of planktonic bacteria and biofilms.
- To explore the potentiation effect of potassium iodide (KI) on the chlorin's antimicrobial activity and cytotoxicity.
- To assess the potential of this enhanced aPDT strategy for treating localized bacterial infections.
Main Methods:
- Tested a dicationic di-imidazolyl chlorin against planktonic *S. aureus* and *E. coli*, and their biofilms, under 660 nm illumination.
- Evaluated the effect of 50 mM potassium iodide (KI) on chlorin efficacy and phototoxicity to human keratinocytes.
- Conducted an exploratory in vivo study using a mouse wound infection model with *E. coli*.
Main Results:
- The chlorin demonstrated bactericidal effects at low nanomolar concentrations for planktonic bacteria and micromolar concentrations for biofilms.
- Potentiation with KI reduced effective chlorin concentrations to less than 50 nM for planktonic bacteria and less than 1 μM for biofilms.
- KI potentiation significantly decreased chlorin phototoxicity to keratinocytes, enabling selective biofilm inactivation and showing promise in a mouse wound infection model.
Conclusions:
- Potentiation with KI, involving the triiodide anion, allows for highly effective and selective antimicrobial photodynamic therapy of bacterial biofilms.
- This strategy overcomes the limitations of high photosensitizer concentrations and host cell toxicity, offering a promising approach to combat bacterial infections.
- The dicationic di-imidazolyl chlorin, potentiated by KI, demonstrates significant potential for controlling localized infections with reduced cytotoxicity.
