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405 nm and 450 nm photoinactivation of <i>Saccharomyces cerevisiae</i>
摘要： Photoinactivation of bacteria with visible light has been reported in numerous studies. Radiation around 405 nm is absorbed by endogenous porphyrins and generates reactive oxygen species that destroy bacteria from within. Blue light in the spectral range of 450–470 nm also exhibits an antibacterial effect, but it is weaker than 405 nm radiation, and the photosensitizers involved have not been clarified yet, even though flavins and porphyrins are possible candidates. There are significantly fewer photoinactivation studies on fungi. To test if visible light can inactivate fungi and to elucidate the mechanisms involved, the model organism Saccharomyces cerevisiae (DSM no. 70449) was irradiated with violet (405 nm) and blue (450 nm) light. The mean irradiation doses required for a one log reduction of colony forming units for this strain were 182 J/cm2 and 526 J/cm2 for 405 nm and 450 nm irradiation, respectively. To investigate the cell damaging mechanisms, trypan blue staining was performed. However, even strongly irradiated cultures hardly showed any stained S. cerevisiae cells, indicating an intact cell membrane and thus arguing against the previously suspected mechanism of cell membrane damage during photoinactivation with visible light at least for the investigated strain. The results are compatible with photoinactivated Saccharomyces cerevisiae cells being in a viable but nonculturable state. To identify potential fungal photosensitizers, the absorption and fluorescence of Saccharomyces cerevisiae cell lysates were determined. The spectral absorption and fluorescence results are in favor of protoporphyrin IX as the most important photosensitizer at 405 nm radiation. For 450 nm irradiation, riboflavin and other flavins may be the main photosensitizer candidates, since porphyrins do not play a prominent role at this wavelength. No evidence of the involvement of other photosensitizers was found in the spectral data of this strain.
关键词： photoinactivation,porphyrin,450 nm irradiation,flavin,Saccharomyces cerevisiae,disinfection,405 nm irradiation
更新于2025-09-23 15:23:52
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Effect of Toxic Metal Ions on Photosensitized Singlet Oxygen Generation for Photodegradation of Polyaromatic Hydrocarbon Derivatives and Inactivation of <i>Escherichia coli</i>
摘要： Here we report an experimental study of the effect of toxic metal ions on photosensitized singlet oxygen generation for photodegradation of PAH derivatives, Anthracene-9,10-dipropionic acid disodium salt (ADPA) and 1,5-dihydroxynapthalene (DHN) and photoinactivation of E. coli bacteria by using cationic meso-tetra(N-methyl-4-pyridyl)porphine tetrachloride (TMPyP) as a singlet oxygen photosensitizer. Three s-block metals ions, such as Na+, K+, and Ca2+ and five toxic metals such as Cd2+, Cu2+, Hg2+, Zn2+, and Pb2+ were studied. The s-block metal ions showed no change of the rate of photodegradation of ADPA or DHN by TMPyP whereas a dramatic change in the photodegradation of ADPA and DHN were observed in the presence of toxic metals. The maximum photodegradation rate constants of ADPA and DHN were observed for Cd2+ ions [(3.91 ± 0.20) × 10-3 s-1 and (7.18 ± 0.35) × 10-4 s-1, respectively]. Strikingly, the photodegradation of ADPA and DHN was almost completely inhibited in the presence of Hg2+ ions and Cu2+ ions. A complete inhibition of growth of E. coli was observed upon visible irradiation of E. coli solutions with TMPyP and toxic metal ions particularly, Cd2+, Hg2+, Zn2+, and Pb2+ ions, except for Cu2+ ions where a significantly slow inhibition of E. coli’s growth was observed.
关键词： E. coli,photodegradation,toxic metal ions,photosensitized singlet oxygen generation,PAH derivatives,TMPyP,photoinactivation
更新于2025-09-23 15:21:01
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Photoinactivation of planktonic and biofilm forms of Escherichia coli through the action of cationic zinc(II)phthalocyanines
摘要： Novel water soluble Zn(II)phthalocyanines (ZnPc) peripherally substituted with 4-dimethylaminopyridine (DMAP) units (ZnPc 1-2) and the corresponding quaternized derivatives (ZnPc 1a-2a) were synthesized and their photodynamic inactivation (PDI) efficiency against a Gram-negative bacterium, a recombinant bioluminescent Escherichia coli strain either in planktonic and biofilm form was investigated. The analysis of the photophysical properties revealed that the increase in the number of DMAP units on ZnPc shifted the absorption and emission band in aqueous media to red. The presence of multi-positive charges on ZnPc derivatives prevented aggregation and enhances the solubility in aqueous medium. The quaternized derivatives ZnPc 1a and 2a displayed good stability and promising efficacy to generate singlet oxygen (1O2). The affinity of the amphiphilic ZnPc 1-2 and quaternized ZnPc 1a-2a to planktonic bacterial cells corresponded to an average uptake of ~106 PS molecules.CFU-1. The PDI assays conducted with planktonic cells and biofilms of E. coli show that irradiation with red or white light (150 mW.cm-2) in the presence of 20 μM of ZnPc derivatives caused an effective inactivation. ZnPc 1a and ZnPc 2a exhibited the highest inactivation efficiency, particularly of the planktonic form, causing 5 log (99.99%) reductions in bioluminescence. The inactivation factor for biofilms was 99% (2 log). ZnPc 1a and ZnPc 2a can be regarded as promising photosensitizers for the photodynamic inactivation of Gram-negative bacteria.
关键词： Reactive Oxygen Species,Cationic Phthalocyanines,E. coli,Bacterial Resistance,Biofilm,Antimicrobial Photoinactivation
更新于2025-09-19 17:15:36
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Inactivation of Bacteria during Stimulation of Sensitizers with High-Power Nanosecond Laser Pulses
摘要： The results of a study of photoinactivation of bacteria during stimulation of sensitizers with nanosecond laser pulses with a power density within 1–30 MW/cm2 are presented. The irreversible damage to living cells by shock waves developed during the formation and collapse of vapor bubbles in locally heated microregions of the medium is discussed. The local heating of the medium occurred due to heat release during nonradiative relaxation of high electronic states of sensitizer molecules.
关键词： local heating,highly excited electronic states of molecules,photoinactivation of bacteria,acoustic waves
更新于2025-09-16 10:30:52
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Realisation and assessment of a low-cost LED device for contact lens disinfection by visible violet light
摘要： This study presents a device for efficient, low-cost and eye-friendly overnight disinfection of contact lenses by visible violet light as an alternative to disinfection with biocide-containing solutions. Bacterial solutions with one Pseudomonas and one Staphylococcus strain each were irradiated for up to 8 h in commercial transparent contact lens cases by the presented light-emitting diode (LED) device. Samples were taken at different intervals and distributed on agar plates. The surviving bacteria were determined by counting of colony-forming units and compared to the specific requirements of the stand-alone test for contact lens disinfection of the hygiene standard ISO 14729. The concentration of both microorganisms was reduced by three orders of magnitude after less than 4 h of irradiation. The LED current and intensity have not yet been at maximum and could be further increased if necessary for other microorganisms. The presented device fulfils the requirement of the stand-alone test of the contact lens hygienic standard ISO 14729 for the tested Pseudomonas and Staphylococcus strains. According to literature data, the inactivation of Serratia marcescens, Candida albicans and Fusarium solani seems also possible, but may require increased LED current and intensity.
关键词： Staphylococcus,LED device,contact lens,visible light,photoinactivation,Pseudomonas,disinfection
更新于2025-09-12 10:27:22
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Photodynamic therapy treatment of wound caused by myiasis in the goat vulva - case report
摘要： Photodynamic therapy (PDT) has been studied in tissue healing and treatment of infected wounds, mainly for their potential to inactivate microorganisms. The objective of this study was to demonstrate the effectiveness of the use of photodynamic therapy in the treatment of a wound caused by myiasis. A young goat, female, Saanen, which had fly larvae infestation by Cochliomyia hominivorax and extensive tissue loss in the region of the vulva and perianal due to larval activity in the tissue was treated with photodynamic therapy. After treatment there was a complete reepithelization in 15 days, demonstrating that photodynamic therapy can be an alternative treatment for wounds.
关键词： healing,Photoinactivation,wounds
更新于2025-09-11 14:15:04
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Photoinactivation of the <b><i>Staphylococcus aureus</i></b> Lactose-Specific EIICB Phosphotransferase Component with <b><i>p</i></b>-azidophenyl-β-D-Galactoside and Phosphorylation of the Covalently Bound Substrate
摘要： Background: The phosphoenolpyruvate (PEP):lactose phosphotransferase system of Staphylococcus aureus transports and phosphorylates lactose and various phenylgalactosides. Their phosphorylation is catalyzed by the Cys476-phosphorylated EIIB domain of the lactose-specific permease enzyme IICB (EIICBLac). Phosphorylation causes the release of galactosides bound to the EIIC domain into the cytoplasm by a mechanism not yet understood. Results: Irradiation of a reaction mixture containing the photoactivatable p-azidophenyl-β-D-galactopyranoside and EIICBLac with UV light caused a loss of EIICBLac activity. Nevertheless, photoinactivated EIICBLac could still be phosphorylated with [32P] PEP. Proteolysis of photoinactivated [32P]P-EIICBLac with subtilisin provided an 11-kDa radioactive peptide. Only the sequence of its first three amino acids (-H-G-P-, position 245–247) could be determined. They are part of the substrate binding pocket in EIICs of the lactose/cellobiose PTS family. Surprisingly, while acid treatment caused hydrolysis of the phosphoryl group in active [32P]P EIICBLac, photoinactivated [32P]P-EIICBLac remained strongly phosphorylated. Conclusion: Phosphorylation of the –OH group at C6 of p-nitrenephenyl-β-D-galactopyranoside covalently bound to EIICLac by the histidyl-phosphorylated [32P]P EIIBLac domain is a likely explanation for the observed acid resistance. Placing p-nitrenephenyl-β-D-galactopyranoside into the active site of modelled EIICLac suggested that the nitrene binds to the -NH- group of Ser248, which would explain why no sequence data beyond Pro247could be obtained.
关键词： Staphylococcus aureus,Lactose transport,Photoinactivation,Phosphoenolpyruvate:carbohydrate phosphotransferase system,Azidophenyl-β-D-galactopyranoside
更新于2025-09-04 15:30:14