Related Experiment Video
Updated: Sep 10, 2025
Author Spotlight: Exploring the Antibacterial Effects of Zinc Oxide Nanoparticles in Overcoming Antibiotic Resistance
Published on: September 27, 2024
Photosensitive PLA-cationic porphyrin films: robust antibacterial materials for fighting multidrug-resistant bacteria
Carolina V Domingos1, Madalena F C Silva1, M Ermelinda S Eusébio1
1CQC-IMS, Department of Chemistry, University of Coimbra, Rua Larga, 3004-535, Coimbra, Portugal. mmpereira@qui.uc.pt.
Abstract:
The global rise of multidrug-resistant (MDR) bacteria highlights the urgent need for alternative strategies to prevent their spread, particularly in healthcare environments. Here, we report the synthesis and evaluation of a novel mono-cationic meso-imidazolyl porphyrin (3) and its integration into biodegradable poly(lactic acid) (PLA) films, resulting in potentially effective, reusable, and broad-spectrum photodynamic antibacterial surfaces. The porphyrin was prepared using a mixed aldehyde condensation followed by microwave-assisted methylation, reducing reaction time to just 1 minute with near-quantitative yield. PLA films containing porphyrin 3 (+PLA-3) were successfully prepared and fully characterized, showing exceptional photostability and minimal leaching in aqueous environments, even under prolonged light exposure. Notably, cationic +PLA-3 exhibited superior material stability compared to analogous PLA films incorporating tetra-cationic porphyrins, attributed to the improved amphiphilic balance of the mono-cationic photosensitizer. Antibacterial studies confirmed that cationic +PLA-3 films achieved complete photodynamic inactivation (7 log CFU reduction) of both Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria under blue LED irradiation. They also demonstrated great effectiveness against clinical multidrug-resistant strains, including MRSA, E. coli, Acinetobacter baumannii, Pseudomonas aeruginosa, and Klebsiella pneumoniae, reaching total inactivation under light doses up to 23.5 J cm-2. Reusability tests confirmed full retention of antibacterial efficacy after up to 11 irradiation cycles, totalling 258.5 J cm-2. These results position cationic +PLA-3 as a promising candidate for use in self-disinfecting surfaces with potential to reduce nosocomial infection risks and environmental impact in healthcare settings.
Insights
Novel photodynamic antibacterial surfaces were developed using a mono-cationic porphyrin integrated into biodegradable poly(lactic acid) films. These reusable films effectively eliminate multidrug-resistant bacteria, offering a promising solution for healthcare settings.
Area of Science:
- Materials Science
- Photochemistry
- Microbiology
Background:
- The rise of multidrug-resistant (MDR) bacteria necessitates innovative strategies to combat infections, especially in healthcare.
- Photodynamic therapy offers a light-activated approach to antimicrobial treatment.
Purpose of the Study:
- To synthesize and evaluate a novel mono-cationic porphyrin-based material for photodynamic antibacterial applications.
- To develop reusable, broad-spectrum antibacterial surfaces using biodegradable poly(lactic acid) films.
Main Methods:
- Synthesis of a mono-cationic meso-imidazolyl porphyrin via microwave-assisted methylation.
- Incorporation of the porphyrin into poly(lactic acid) (PLA) films to create +PLA-3.
- Characterization of photostability, leaching, and material stability of the +PLA-3 films.
- Evaluation of photodynamic antibacterial efficacy against Gram-positive, Gram-negative, and MDR bacterial strains under blue LED irradiation.
Main Results:
- The synthesized porphyrin was efficiently incorporated into PLA films (+PLA-3) with excellent photostability and minimal leaching.
- +PLA-3 films demonstrated superior material stability compared to those with tetra-cationic porphyrins.
- Complete photodynamic inactivation (7 log CFU reduction) of *Staphylococcus aureus* and *Escherichia coli* was achieved.
- Effective inactivation of clinical MDR strains (MRSA, *A. baumannii*, *P. aeruginosa*, *K. pneumoniae*) was observed.
- Antibacterial efficacy was fully retained after 11 irradiation cycles, demonstrating reusability.
Conclusions:
- Mono-cationic porphyrin-integrated PLA films (+PLA-3) represent effective, reusable, broad-spectrum photodynamic antibacterial surfaces.
- These materials show significant potential for reducing healthcare-associated infections and environmental impact.
- The developed technology offers a promising alternative to conventional antimicrobial strategies in clinical settings.
