查看更多>>摘要：Water disinfection is one of the most important applications of ultraviolet light-emitting diodes (UV-LEDs), though bacterial regrowth remains a serious problem. In this study, we showed that UV-resistant cells, though rare, exist in an Escherichia coli clonal population. The UV-resistance of stationary phase cells was higher than that of exponential phase cells. Regrowth cell populations showed identical UV sensitivity before and after UV treatment, indicating that UV resistance is not acquired genetically, but is generated stochastically. The characteristics of these UV-resistant cells are similar to those of non-heritable antibiotic-resistant cells, termed persisters. The induction of persister formation increased the number of viable cells after UV treatment. The toxin-antitoxin system gene hipA (high persistence A) is a key factor in persister cell formation. We observed that hipA was strongly expressed in the stationary phase cells, while regrowth cells after UV treatment lost hipA expression, suggesting that the regrowth cells lost their persistence. Compared to UV batch radiation, we demonstrated that intermittent UV irradiation, which included the induction of regrowth between UV treatments, significantly reduced the number of viable E. coli cells.
Prandini, Juliana A.Castro, Kelly A. D. F.Biazzotto, Juliana C.Brancini, Guilherme T. P....
8页
查看更多>>摘要：The emergence of opportunistic pathogens and the selection of resistant strains have created a grim scenario for conventional antimicrobials. Consequently, there is an ongoing search for alternative techniques to control these microorganisms. One such technique is antimicrobial photodynamic therapy (aPDT), which combines photosensitizers, light, and molecular oxygen to produce reactive oxygen species and kill the target pathogen. Here, the in vitro susceptibilities of three fungal pathogens, namely Candida albicans, Aspergillus nidulans, and Colletotrichum abscissum to aPDT with zinc(II) phthalocyanine (ZnPc) derivative complexes were investigated. Three ZnPc bearing thiopyridinium substituents were synthesized and characterized by several spectroscopic techniques. The Q-band showed sensitivity to the substituent with high absorptivity coefficient in the 680-720 nm region. Derivatization and position of the rings with thiopyridinium units led to high antifungal efficiency of the cationic phthalocyanines, which could be correlated with singlet oxygen quantum yield, subcellular localization, and cellular uptake. The minimum inhibitory concentrations (MIC) of the investigated ZnPc-R complexes against the studied microorganisms were 2.5 mu M (C. albicans) and 5 mu M (A. nidulans and C. abscissum). One ZnPc derivative achieved complete photokilling of C. albicans and, furthermore, yielded low MIC values when used against the tolerant plant-pathogen C. abscissum. Our results show that chemical modification is an important step in producing better photosensitizers for aPDT against fungal pathogens.
查看更多>>摘要：Plasmonic nanomaterials of gold and silver have been reported to have antibacterial effect. In this study, three gold nanomaterials (NMs) of different aspect rations (Gold nanospheres (AuNSs, aspect ratio 1), and two gold nanorods (AuNRs636, aspect ratio 2.79; AuNRs772, aspect ratio 3.42)) and silver nanoparticles (AgNPs) were synthesized, characterized and the effect of incandescent light on their antibacterial properties were examined. Bacterial inactivation during photoinactivation of nanomaterials and antibacterial mechanisms (biotic ROS, membrane potential, membrane damage) were investigated using Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923, Salmonella enterica serovar Typhimurium, and methicillin-resistant S. aureus. The results indicated that AuNSs had no antibacterial activity in the tested concentration (0.49-250 mu g/mL), while AuNR636 and AuNRs772 showed significant bactericidal effect on all tested bacteria. Notably, AuNRs636 presented higher antibacterial effect than AuNRs772, which could result from higher surface reactivity of AuNRs636 owing to higher dangling bonds. Further studies showed that AuNRs but not AuNSs generated hydroxyl radicals (center dot OH) (photodynamic effect) and photothermal effect when exposed to incandescent light. The combined photodynamic and photothermal effect resulted in bacterial inactivation through cell membrane damage, lowering of cell membrane potential and DNA degradation. In summary, this investigation showed that Au NRs but not Au NSs exhibit photodynamic and photothermal effects suggesting the potential of fabricating material surfaces with Au NRs for photoactivated bacterial inactivation.
查看更多>>摘要：The photodynamic inactivation (PDI) represents the potential alternative to traditional antibiotic therapy, and can be applied to treat various bacterial infections, including those caused by Gram-negative bacterial strains. One of the treatment modalities is based on the capacity of bacterial cells to synthesize the excess amounts of porphyrins after exposure to an externally applied 5-aminolevulinic acid (5-ALA), which makes them photosensitive and leads to reduced survival after irradiation with an appropriately selected light source. This study focuses on the sensitization and the photoinduced inactivation of Salmonella enterica cells in PBS containing 0.5 mM 5-ALA, incubated at 37 degrees C for 4 h or for 20 h and afterwards irradiated with violet LED light (11.1 mW/cm(2), a peak at 400 nm). It has been found that both amounts and composition of endogenous porphyrins not only depended on the incubation duration, but also were affected by externally induced photo- and chemo-oxidation reactions. The application of different sensitization conditions has revealed that the increasing amounts of endogenously produced porphyrins do not ensure the proportional reduction of bacterial cell survival numbers. The comparative investigations also demonstrated that the presence of endogenously produced porphyrins in the medium results in secondary sensitization of bacterial cells and causes a notably stronger photoinactivation effect in comparison to their externally applied standards.
Di Giorgio, ErosFerino, AnnalisaChoudhary, HimanshiLoffler, Phillip M. G....
15页
查看更多>>摘要：Cationic porphyrins bearing an alkyl side chain of 14 (2b) or 18 (2d) carbons dramatically inhibit proliferation of pancreatic cancer cells following treatment with light. We have compared two different ways of delivering porphyrin 2d: either in free form or engrafted into palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine liposomes (L 2d). Cell cytometry shows that while free 2d is taken up by pancreatic cancer cells by active (endocytosis) and passive (membrane fusion) transports, L -2d is internalized solely by endocytosis. Confocal microscopy showed that free 2d co-localizes with the cell membrane and lysosomes, whereas L -2d partly co-localizes with lysosomes and ER. It is found that free 2d inhibits the KRAS-Nrf2-GPX4 axis and strongly triggers lipid peroxidation, resulting in cell death by ferroptosis. By contrast, L -2d does not affect the KRAS-Nrf2-GPX4 axis and activates cell death mainly through apoptosis. Overall, our study demonstrates for the first time that cationic alkyl porphyrins, which have a IC50 similar to 23 nM, activate a dual mechanism of cell death, ferroptosis and apoptosis, where the predominant form depends on the delivery mode.
查看更多>>摘要：Cuspareine as an antiviral alkaloid can be used in the treatment of COVID-19. In this study, we introduced the ionic liquids (ILs) concluded cuspareinium as a cation with CH3COO-, CF3COO-, and PF6 as anions. The optimized geometry, thermodynamic parameters, and reactivity descriptors were calculated with density functional theory (DFT) approach and time-dependent density functional theory (TD-DFT) using B3LYP/6-311G. In addition, the UV and IR spectra of the introduced ILs were investigated. Based on DFT calculation, the designed IL CH3COO- can be to the most suitable anions due to most solubility in the water. DFT studies displayed that all the introduced ILs have more polarity than pristine cuspareine and CH3COO- -cuspareine is the most polarity due to high dipole moment. Also, the thermo- chemical data of the designed ionic liquids revealed that PF6cuspareine is distinguished to be stable. A molecular docking study of the designed ILs with 6 LU7 protease was performed to display interactions and binding energy. Results of molecular docking displayed that CH3COOion liquid has the highest binding energy (- 7.20 kcal/mol) and Ala7, and Lys 5 residues are involved in an interaction. DFT and molecular docking studies of cuspareine as alkaloid based on ionic liquids can be helpful to for more pharmaceutical and biological researches of cuspareine as an antiviral agent against COVID-19.
NSTL
Elsevier