On the use of porous nanomaterials to photoinactivate E. coli with natural sunlight irradiation

.An organic-inorganic hybrid material based on nanocrystals of zeolite L functionalized with silicon phthalocyanine can develop interesting properties when activated by natural sunlight. Cell viability tests show that this nanomaterial is able to photoinactivate mouse cells and Escherichia coli (. E. coli) bacteria, and is also very efficient against the self-defense mechanisms of E. coli during the first minutes of solar irradiation. The results suggest that Gram-negative E. coli become more resistant to singlet oxygen-based disinfection treatments at higher temperatures. The present work contributes to the development of new functional materials for a range of important sunlight-based applications. © 2015 Elsevier Lt

Antimicrobial Photodynamic Therapy: Study of Bacterial Recovery Viability and Potential Development of Resistance after Treatment

Antimicrobial photodynamic therapy (aPDT) has emerged in the clinical field as a potential alternative to antibiotics to treat microbial infections. No cases of microbial viability recovery or any resistance mechanisms against it are yet known. 5,10,15-tris(1-Methylpyridinium-4-yl)-20-(pentafluorophenyl)-porphyrin triiodide (Tri-Py+-Me-PF) was used as photosensitizer. Vibrio fischeri and recombinant Escherichia coli were the studied bacteria. To determine the bacterial recovery after treatment, Tri-Py+-Me-PF (5.0 μM) was added to bacterial suspensions and the samples were irradiated with white light (40 W m−2) for 270 minutes. Then, the samples were protected from light, aliquots collected at different intervals and the bioluminescence measured. To assess the development of resistance after treatment, bacterial suspensions were exposed to white light (25 minutes), in presence of 5.0 μM of Tri-Py+-Me-PF (99.99% of inactivation) and plated. After the first irradiation period, surviving colonies were collected from the plate and resuspended in PBS. Then, an identical protocol was used and repeated ten times for each bacterium. The results suggest that aPDT using Tri-Py+-Me-PF represents a promising approach to efficiently destroy bacteria since after a single treatment these microorganisms do not recover their viability and after ten generations of partially photosensitized cells neither of the bacteria develop resistance to the photodynamic process

A comparative study of the photoinactivation of bacteria by meso -substituted cationic porphyrin, rose Bengal and methylene blue

International audienceAdvances in wastewater treatment technology have led many to predict that planned wastewater reuse in agriculture will soon become more common in some regions of the world which face acute problems of water quality and quantity. The use of ecologically friendly wastewater disinfection techniques could be one of the most exciting advances in this field. The combined action of a photosensitizer (meso-substituted cationic porphyrin, TMPyP; rose Bengal, RB; methylene blue, MB) and visible light, particularly sunlight, seem to be a promising approach to microbial inactivation, potentially applicable for disinfection of domestic effluents. In the present work, photosensitization was either performed on Gram-positive and Gram-negative bacteria in pure culture (Enterococcus hirae and Escherichia coli), or carried out with wild strains in secondary wastewater effluent (enterococci and E. coli). The results described in this paper show that TMPyP is the most effective for photoinactivation of the bacterial models studied here. The relative effectiveness of RB and MB was found to be tightly linked to bacteria Gram type. Whatever the sensitizer used, Gram-negative bacteria were more resistant to photosensitization than Gram-positive strains. The order of increasing effectiveness of the photosensitizers for photoinactivation of Gram-positive bacteria (TMPyP ≥ RB > MB) and Gram-negative bacteria (TMPyP > MB > RB) remains unchanged for either pure culture or wild strains (bacterial communities in wastewater). The effectiveness of the photochemical process depends primarily on the type of microorganisms as well as the type of photosensitizers (concentration, singlet oxygen quantum yield, ionic charge), and the reaction medium

Photoinactivation de bactéries d intérêt sanitaire en condition de simulation solaire en présence de photosensibilisants synthétiques et/ou naturels

La photosensibilisation utilise une substance promotrice de l activité désinfectante de la lumière solaire faisant intervenir les espèces réactives de l oxygène. Dans ce travail nous avons retenu une porphyrine cationique (TMPyP). Pour cerner les facteurs de l efficacité de la désinfection des eaux usées, nous avons étudié les mécanismes de photoinactivation des bactéries. Les bactéries Gram-négatif (Escherichia coli) apparaissent plus résistantes à la photoinactivation que les bactéries Gram-positif (Enterococcus hirae). La même observation est réalisée sur des bactéries sauvages dans un effluent d eau usée. Les essais en résonance paramagnétique électronique (RPE) montrent que la TMPyP est susceptible d agir sur des substrats via les réactions de type I (espèces radicalaires) ou de Type II (oxygène singulet). La comparaison de l action de photosensibilisants synthétiques ou naturels à celle de la TMPyP montre que ce dernier est plus efficace pour la photoinactivation des bactéries. L efficacité du processus est lié au type de microorganismes, à la concentration et la charge électronique du photosensibilisant et à la charge organique du milieu.RENNES1-BU Sciences Philo (352382102) / SudocSudocFranceF

Involvement of both Type I and Type II mechanisms in Gram-positive and Gram-negative bacteria photosensitization by a meso-substituted cationic porphyrin

International audienceA meso-substituted cationic porphyrin (TMPyP) showed a photocytotoxicity against Gram-positive and Gram-negative bacteria. In order to determine the mechanism involved in the phototoxicity of this photosensitizer, electron paramagnetic resonance (EPR) experiments with 2,2,6,6-tetramethyl-4-piperidone (TEMP), a specific probe for singlet oxygen, and the spin-trap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) were carried out with illuminated TMPyP. An EPR signal characteristic of TEMP-singlet oxygen (TEMPO) adduct formation was observed, which could be ascribed to singlet oxygen (1O2) generated by TMPyP photosensitization. The signal for the DMPO spin adduct of superoxide anion (DMPO-OOH) was observed in DMSO solution but not in aqueous conditions. However, an EPR spectrum characteristic of the DMPO-hydroxyl radical spin adduct (DMPO-OH) was observed in aqueous conditions. The obtained results testify a primary hydroxyl radical ({radical dot}OH) generation probably from superoxide anion (O2{radical dot} -) via the Fenton reaction and/or via Haber-Weiss reaction. Gram-positive and Gram-negative bacteria inactivation by TMPyP photosensitization predominantly involved Type II reactions mediated by the formation of 1O2, as demonstrated by the effect of quenchers for 1O2 and scavengers for {radical dot}OH (sodium azide, thiourea, and dimethylsulphoxide). Participation of other active oxygen species cannot however be neglected since Type I reactions also had a significant effect, particularly for Gram-negative bacteria. For Gram-negative bacteria the photoinactivation rate was lower in the presence of superoxide dismutase, a specific O2{radical dot} - scavenger, and/or catalase, an enzyme which specifically eliminates H2O2, but was unchanged for Gram-positive bacteria. The generation of 1O2, O2{radical dot} - and {radical dot}OH by TMPyP photosensitization indicated that TMPyP maintained a photodynamic activity in terms of Type I and Type II mechanisms

Lethal photosensitisation of 'Staphylococcus aureus' and 'Escherichia coli' using crystal violet and zinc oxide-encapsulated polyurethane

Crystal violet and zinc oxide nanoparticles (CVZnO) were incorporated into medical grade polyurethane polymers by a two-step dipping procedure to prepare novel bactericidal surfaces. The photobactericidal activity of CVZnO polyurethane samples was tested against the Gram-positive bacterium, Staphylococcus aureus and the Gram-negative bacterium, Escherichia coli. Exposure of the polymer samples to white light induced the lethal photosensitisation of both S. aureus and E. coli. In addition, this novel system demonstrated significant antibacterial activity under dark conditions against S. aureus within 2 hours, but more remarkably, a 99.9% reduction in the numbers of E. coli within 4 hours in the dark. This is, to the best of our knowledge, the most potent ‘dark-kill’ by a light activated antimicrobial agent ever reported. The singlet oxygen quenchers, bovine serum albumin and L-histidine, and an enzyme which catalyses the decomposition of hydrogen peroxide, bovine catalase, were incorporated into the antibacterial assays to determine if the mechanism of E. coli kill involved a Type 1 or a Type 2 light-activated process