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Femtosecond Spectroscopy of Au Hot-Electron Injection into TiO2: Evidence for Au/TiO2 Plasmon Photocatalysis by Bactericidal Au Ions and Related Phenomena
摘要： In the present work, we provide evidence for visible light irradiation of the Au/TiO2 nanoparticles’ surface plasmon resonance band (SPR) leading to electron injection from the Au nanoparticles to the conduction band of TiO2. The Au/TiO2 SPR band is shown to greatly enhance the light absorption of TiO2 in the visible region. Evidence is presented for the light absorption by the Au/TiO2 plasmon bands leading to the dissolution of Au nanoparticles. This dissolution occurs concomitantly with the injection of the hot electrons generated by the Au plasmon into the conduction band of TiO2. The electron injection from the Au nanoparticles into TiO2 was followed by femtosecond spectroscopy. The formation of Au ions was further confirmed by the spectral shift of the transient absorption spectra of Au/TiO2. The spectral changes of the SPR band of Au/TiO2 nanoparticles induced by visible light were detected by spectrophotometer, and the morphological transformation of Au/TiO2 was revealed by electron microscopy techniques as well. Subsequently, the fate of the Au ions was sorted out during the growth and biofilm formation for some selected Gram-negative bacteria. This study compares the bactericidal mechanism of Au ions and Ag ions, which were found to be substantially different depending on the selected cell used as a probe.
关键词： electron injection,antibacterial effects,genes expression,DNA repair,quorum sensing,plasmon photocatalysis,biofilms,gold nanoparticles,porins
更新于2025-11-21 11:20:42
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Comparative Effect of Two Red Lights on <i>Streptococcus mutans</i> Biofilms and Assessment of Temperature Variances in Human Teeth During <i>In Vitro</i> Photodynamic Antimicrobial Chemotherapy
摘要： Objective: The goals of this investigation were to compare the effect of photodynamic antimicrobial chemotherapy (PACT) with two different red lights on in vitro Streptococcus mutans biofilms, as well as to assess the temperature variances caused by PACT on human teeth. Methods: S. mutans biofilms (n = 3) were grown on hydroxyapatite disks, and the antimicrobial effect of PACT was evaluated using toluidine blue O (100 lg/mL) associated with Laserbeam(cid:2) (LB 56.6 J/cm2) and LumaCare(cid:3) (LC -56.6, 158.5, 317.0, and 475.6 J/cm2). Pulpal temperature variances were analyzed using a digital thermocouple placed into the pulp chamber and positioned at the cement–enamel junction level of five teeth samples during irradiation times of 300, 600, and 900 sec for LB, and 22, 60, 120, and 180 sec for LC. The mean average temperature variance was calculated for each group. All data were analyzed through analysis of variance. Results: LB (900 sec) and LC (22 sec) induced similar reductions in the viability of microorganisms. LB did not cause statistically significant increase of temperature, regardless of experimental time, and LC caused temperature increase within the safe spectrum up to 60 sec. Conclusions: PACT seems to be a minimal invasive approach for reducing the viability of cariogenic bacteria. Thus, when applied in vitro for times equal or inferior to 900 and 60 sec for LB and LC, respectively, these light sources might be considered harmless to tooth structures.
关键词： biofilms,anti-infective agents,Streptococcus mutans,photochemotherapy,temperature,dental pulp cavity
更新于2025-09-23 15:22:29
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Application Laser Transfer of Metal Nanoparticles to Bacterial Biofilms
摘要： The method of application laser transfer of silver and copper nanoparticles for the first time has been shown to be effective against biofilms formed on a solid substrate. It has been experimentally confirmed that this effect is not associated with the influence of the laser itself. The proposed method allows one to increase the locality, availability, and efficiency of biofilm destruction due to the bactericidal effect of metal nanoparticles with a slight direct laser effect on the biofilm.
关键词： metal nanoparticles,laser ablation,bacterial biofilms
更新于2025-09-23 15:21:01
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Could being chlorhexidine an adequate positive control to antimicrobial photodynamic therapy in in vitro studies?
摘要： Background: Chlorhexidine digluconate (CHX) is commonly applied as positive control of new antimicrobials, because it is considered the gold-standard for chemical plaque control. In this sense, the aim of this study was to compare the effect of treatments with curcumin-mediated aPDT and CHX in relation to the viability of specific microorganism groups in two distinct times (immediately and 24h later). Methods: Dentin caries microcosms were grown on bovine dentin discs (37oC, anaerobiosis) for 3 days in the Active Attachment Amsterdam Biofilm Model. The biofilms were treated with 300 μM curcumin and 75 J.cm-2 LED, or 0.06% and 0.12% CHX. Then, total microorganisms, total streptococci, mutans streptococci, and total lactobacilli counts were determined. The statistical analysis was conducted by Kruskal-Wallis and post-hoc Dunn's tests (P<0.05). Results: Curcumin-mediated aPDT (C+L+), 0.06% and 0.12% CHX reduced mutans streptococci counts (0.19, 0.10 and 0.07 log10 respectively) in the immediate analysis. After 24h, it was observed a re-growth of microorganisms treated by curcumin-mediated aPDT, whereas both CHX concentrations demonstrated a decrease of the viable microorganisms. Conclusion: This study confirmed the substantive effect of CHX and the immediate effect of aPDT. The use of a neutralizer solution was important to block the substantivity of CHX and permit its fair comparison with aPDT, allowing its use as a positive control in further studies.
关键词： Dental Caries,Oral Biofilms,Photochemotherapy,Chlorhexidine
更新于2025-09-23 15:21:01
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Bacteria-Targeted Supramolecular Photosensitizer Delivery Vehicles for Photodynamic Ablation Against Biofilms
摘要： Photodynamic therapy (PDT) is believed to be a potent method for biofilm treatments. However, undesired damage to normal cells may be caused due to the nonselective nature of PDT. Therefore, targeted PDT is preferred on one hand to enhance antimicrobial effects and on the other hand to reduce cytotoxicity to normal cells. For this purpose, novel bacteria-targeted photosensitizer delivery micelles are fabricated, taking advantage of α-cyclodextrin (α-CD)/polyethylene glycol (PEG) supramolecular assembly. Hydrophilic antimicrobial peptide (AMP) Magainin I is covalently bound with PEG, working as a bacterial targeting group as well as the stabilizing shell of the supramolecular micelles. Photosensitizer Chlorin e6 (Ce6) is grafted onto α-CD. The micelles exhibit excellent bacterial targeting effects. Compared to α-CD-Ce6, the supramolecular micelles possess enhanced biofilm killing ability against Gram (?) Pseudomonas aeruginosa biofilms and Gram (+) methicillin-resistant Staphylococcus aureus (MRSA) biofilms while reducing cytotoxicity to NIH/3T3 model cells.
关键词： antimicrobial peptides,biofilms,targets,cytocompatibility,photodynamic therapy
更新于2025-09-23 15:21:01
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A multifunctional platform with single-NIR-laser-triggered photothermal and NO release for synergistic therapy against multidrug-resistant Gram-negative bacteria and their biofilms
摘要： Background: Infectious diseases caused by multidrug-resistant (MDR) bacteria, especially MDR Gram-negative strains, have become a global public health challenge. Multifunctional nanomaterials for controlling MDR bacterial infections via eradication of planktonic bacteria and their biofilms are of great interest. Results: In this study, we developed a multifunctional platform (TG-NO-B) with single NIR laser-triggered PTT and NO release for synergistic therapy against MDR Gram-negative bacteria and their biofilms. When located at the infected sites, TG-NO-B was able to selectively bind to the surfaces of Gram-negative bacterial cells and their biofilm matrix through covalent coupling between the BA groups of TG-NO-B and the bacterial LPS units, which could greatly improve the antibacterial efficiency, and reduce side damages to ambient normal tissues. Upon single NIR laser irradiation, TG-NO-B could generate hyperthermia and simultaneously release NO, which would synergistically disrupt bacterial cell membrane, further cause leakage and damage of intracellular components, and finally induce bacteria death. On one hand, the combination of NO and PTT could largely improve the antibacterial efficiency. On the other hand, the bacterial cell membrane damage could improve the permeability and sensitivity to heat, decrease the photothermal temperature and avoid damages caused by high temperature. Moreover, TG-NO-B could be effectively utilized for synergistic therapy against the in vivo infections of MDR Gram-negative bacteria and their biofilms and accelerate wound healing as well as exhibit excellent biocompatibility both in vitro and in vivo. Conclusions: Our study demonstrates that TG-NO-B can be considered as a promising alternative for treating infections caused by MDR Gram-negative bacteria and their biofilms.
关键词： Biofilms,Single-NIR-laser-triggered,Graphene,NO release,Multidrug-resistant Gram-negative bacteria,Synergistic,Photothermal
更新于2025-09-23 15:19:57
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The pulsed light inactivation of veterinary relevant microbial biofilms and the use of a RTPCR assay to detect parasite species within biofilm structures
摘要： The presence of pathogenic organisms namely parasite species and bacteria in biofilms in veterinary settings, is a public health concern in relation to human and animal exposure. Veterinary clinics represent a significant risk factor for the transfer of pathogens from housed animals to humans, especially in cases of wound infection and the shedding of faecal matter. This study aims to provide a means of detecting veterinary relevant parasite species in bacterial biofilms, and to provide a means of disinfecting these biofilms. A real time PCR assay was utilized to detect parasite DNA in Bacillus cereus biofilms on stainless steel and PVC surfaces. Results show that both Cryptosporidium and Giardia attach to biofilms in large numbers (100-1000 oo/cysts) in as little as 72 hours. Pulsed light successfully inactivated all test species (Listeria, Salmonella, Bacillus, Escherichia) in planktonic and biofilm form with an increase in inactivation for every increase in UV dose.
关键词： Giardia,Cryptosporidium,Biofilms,Veterinary,PCR
更新于2025-09-19 17:15:36
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Intimately coupled TiO2/g-C3N4 photocatalysts and in-situ cultivated biofilms enhanced nitrate reduction in water
摘要： Nitrogen pollution has become a major threat to the aquatic environment, and the key to solve this problem is to enhance the nitrate reduction in water. Intimately coupled photocatalysis and biodegradation (ICPB) is a novel technique for degradation of bio-recalcitrant pollutants; however, it has not been used for nitrate reduction. This study applied a system that intimately coupled TiO2/g-C3N4 photocatalysts and in-situ cultivated biofilms for nitrate reduction in water without additional electron donors. The result shows a nitrate removal rate up to 40.3% in ICPB after 16 h. Furthermore, the N2 selectivity was 86.3%, which was higher than that for other protocols. In ICPB, nitrate was first reduced to nitrite, which was mainly contributed to the effect of biofilms. Then, nitrite was reduced via the cooperation of photocatalysts and biofilms, which benefited both low production of undesirable products and high selectivity of N2. Moreover, the growth of the microbes during the ICPB were favorable for denitrification. In conclusion, light-induced electrons generated from TiO2/g-C3N4 were harvested by microbes, optimizing the community structure of biofilms toward nitrate reduction. This study provides a new strategy to enhance the nitrate reduction in water and an insight into the reduction mechanism of nitrate in ICPB.
关键词： Intimately coupled system,Biofilms,Electrons,Photocatalysis,Nitrate
更新于2025-09-19 17:13:59
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In Situ Monitoring of the Antibacterial Activity of a Copper–Silver Alloy Using Confocal Laser Scanning Microscopy and pH Microsensors
摘要： The antibacterial efficacy of a copper–silver alloy coating under conditions resembling build up of dry surface bacterial biofilms is successfully demonstrated according to US EPA test methods with a ≥99.9% reduction of test organisms over a 24 h period. A tailor-made confocal imaging protocol is designed to visualize in situ the killing of bacterial biofilms at the copper–silver alloy surface and monitor the kinetics for 100 min. The copper–silver alloy coating eradicates a biofilm of Gram-positive bacteria within 5 min while a biofilm of Gram-negative bacteria are killed more slowly. In situ pH monitoring indicates a 2-log units increase at the interface between the metallic surface and bacterial biofilm; however, the viability of the bacteria is not directly affected by this raise (pH 8.0–9.5) when tested in buffer. The OH? production, as a result of the interaction between the electrochemically active surface and the bacterial biofilm under environmental conditions, is thus one aspect of the contact-mediated killing of the copper–silver alloy coating and not the direct cause of the observed antibacterial efficacy. The combination of oxidation of bacterial cells, release of copper ions, and local pH raise characterizes the antibacterial activity of the copper–silver alloy-coated dry surface.
关键词： bacterial biofilms,confocal laser scanning microscopy,copper–silver alloy,electroplating,antibacterial activity
更新于2025-09-11 14:15:04
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A living liquid crystal dissected
摘要： A large-scale imaging study has tracked thousands of bacteria living in three-dimensional biofilms. This technical tour de force reveals the importance of mechanical interactions between cells for building local and global structure.
关键词： Biofilms,Living Liquid Crystal,Mechanical Interactions,Microbial Biophysics,Three-dimensional Imaging
更新于2025-09-09 09:28:46