Bactericidal effect of hydroxyl radicals generated from a low concentration hydrogen peroxide with ultrasound in endodontic treatment

Anti-inflammatory potential of remimazolam: A laboratory and clinical investigation

BACKGROUND

Anesthetic agents, particularly intravenous anesthetics, may affect immune function and tumorigenic factors. We herein investigated whether the anti-inflammatory effects of anesthetic agents are attributed to their antioxidant properties. The antioxidant and anti-inflammatory effects of remimazolam, a new anesthetic, remain unclear. We hypothesized that remimazolam exerts anti-inflammatory effects due to its antioxidant properties, which may affect the postoperative inflammatory response. This retrospective clinical study examined this hypothesis using laboratory and clinical approaches.

METHODS

The antioxidant effects of remimazolam and dexmedetomidine were assessed by electron spin resonance (ESR) spectroscopy, and postoperative inflammatory responses were compared in 143 patients who underwent transcatheter aortic valve replacement at Kindai University Hospital between April 2021 and December 2022. The primary endpoint was the presence or absence of the antioxidant effects of the anesthetics themselves using ESR.

RESULTS

Remimazolam at clinical concentrations exerted antioxidant effects, whereas dexmedetomidine did not. Increases in C-reactive protein (CRP) levels on POD3 from preoperative values were significantly smaller in the remimazolam group than in the dexmedetomidine group (1.33 ± 1.29 vs. 2.17 ± 1.84, p = .014).

CONCLUSIONS

Remimazolam exerted stronger anti-inflammatory effects than dexmedetomidine, and these effects were enhanced by its antioxidant properties, which may have affected postoperative CRP production.

The effect of the combined system of hydrodynamic cavitation, ozone, and hydrogen peroxide on chlorophyll a and organic substances removal in the raw water

Increased levels of nutrients and algae can cause drinking water problems in communities. Harmful algal blooms affect humans, fish, marine mammals, birds, and other animals. In the present study, we investigated the use of a combined system [Hydrodynamic Cavitation, Ozone (O₃), and Hydrogen Peroxide (H₂O₂)] on the removal of Chlorophyll a and Organic substances in the raw water was investigated. The Effect of different operating conditions such as pH, cavitation time, pressure, distance, flow rate, ozone dose, and hydrogen peroxide concentration was studied. Utilizing the Taguchi design method, experiments were planned and optimized. The combined system treatment yielded a maximum reduction in Chlorophyll a and Total Organic Carbon (TOC) at an optimum condition of pH 5, cavitation pressure 5 bar, flow rate of 1 m³/h, a distance of 25 cm from the orifice plate, O₃ 3 g/h and 2 g/l of H₂O₂ concentrations. The most efficient factor in the degradation of TOC and Chlorophyll a, was cavitation pressure based on the percentage contributions of each parameter (38.64 percent and 35.05 percent, respectively). H₂O₂ was found to have the most negligible impact on degradation efficiency (4.24 percent and 4.11 percent, respectively).

Enhanced inactivation of Escherichia coli by ultrasound combined with peracetic acid during water disinfection

Peracetic acid (PAA) is a desirable disinfectant for municipal wastewater because of its potent disinfection performance and limited toxic by-products. This study explored the efficiency and mechanism of Escherichia coli inactivation by PAA combined with ultrasound simultaneously (ultrasound + PAA) or (ultrasound → PAA) sequentially. The result showed that 60 kHz ultrasound combined with PAA sequentially (60 kHz → PAA) had excellent inactivation performance on E. coli, up to 4.69-log₁₀. The result also showed that the increase of pH and humic acid concentration in solution significantly reduced the inactivation efficiency of 60 kHz → PAA treatment. We also observed that the increase of temperature was beneficial to the disinfection, while anions (Cl^-; HCO₃^-) had little effect. With 60 kHz → PAA, the PAA and the synergism between PAA and ultrasound played major contribution to the inactivation, which we assumed might be due to both the diffusion of PAA into the cells and the damage to the cytomembrane by ultrasound, as evidenced through the laser confocal microscopy (LSCM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The inactivation mechanism involved the destruction of cell membrane and loss of intracellular material. Empirically, 60 kHz → PAA was found to be effective for the inactivation of E. coli in actual wastewater, and the regrowth potential of E. coli treated by 60 kHz → PAA was significantly lower than that treated only by PAA.

Copper: DNA extraction and solid phase detection agent for all-in-one molecular diagnostic device coupled with isothermal amplification

In this study, an all-in-one poly(methyl methacrylate) (PMMA) device integrating two novel techniques - DNA extraction employing a CuSO₄/H₂O₂ system and DNA detection utilizing solid phase copper tape - coupled with loop-mediated isothermal amplification (LAMP) is developed for on-site pathogen detection. The CuSO₄/H₂O₂ system, also known as Fenton-like reaction, is used to produce hydroxyl radicals, which can disrupt bacterial membranes via lipid peroxidation and release DNA at room temperature. The released DNA is subsequently amplified by LAMP reaction. The acidic environment resulting from the production of hydrogen ions in the presence of target DNA in the LAMP reaction can stimulate the color change on copper tape due to the corrosion, while the innate alkaline environment in a negative sample not containing target DNA cannot stimulate the corrosion. The fabricated PMMA device integrates all the functionalities necessary for molecular diagnostics such as DNA extraction, amplification, and detection, and a carbon paste-based heater is fabricated for LAMP reaction. Using the PMMA device, Enterococcus faecium was detected as low as 4.67 × 10² CFU/mL within 90 min. E. faecium spiked in milk was successfully detected using the all-in-one PMMA device. The equipment-free techniques for decentralized diagnostics and naked-eye readout of results coupled with the portable heater serves as a promising solution for point-of-care testing particularly in a resource-limited environment.

Biologically treated industrial wastewater disinfection using the synergy of low-frequency ultrasound and H2O2/O3

Biological wastewater treatment is mostly used in many industries to treat industrial influents. Treated water is consisting of an extremely high concentration of pathogenic microorganisms. Present work demonstrate the treatment of biologically treated sugar industry wastewater (BTSWW) using a low-frequency ultrasound (US). BTWSS consists of Enterobacter, Salmonella, and Escherichia Coli with a total coliform concentration of 2500 ± 300 CFU/mL. Experiments were performed using the individual effect of US, H2O2, and O3 and the combined effect of US with H2O2, O3, and H2O2 + O3. The complete removal of total coliform was obtained for the synergy effect of US with H2O2 and O3. The performance of the process was analyzed based on pseudo-first-order kinetic rate constant and synergy coefficient. The pseudo-first-order kinetic rate constant was 21.6 and 22.3 × 10-2 min-1 with a synergy coefficient of 2 and 1.9 for a combined effect of US with H2O2 and O3, respectively. Another advantage of the synergy of US and O3 was lower requirement of the initial dose of H2O2 (2.1 mM/L). The operational cost of the process was found to be $ 1.5 × 10-2 /MLD.

Graphical abstract

Investigation of distinct contribution of nitric oxide and each reactive oxygen species in indole-3-propionic-acid-induced apoptosis-like death in Escherichia coli

AIMS

Indole-3-propionic acid (IPA) is a natural product from human microbiota, exhibiting diverse biological activities. The study focused on investigating the antibacterial mode of action(s) triggered by IPA in Escherichia coli. Separate influence of nitric oxide (NO) and each reactive oxygen species, including superoxide anion (O₂^-), hydrogen peroxide (H₂O₂), hydroxyl radical (OH^-), was specifically analyzed throughout the process.

MAIN METHODS

The generation of respective reactive oxygen species (ROS), NO, and ONOO^- was conducted using flow cytometer using different dyes. Further analysis of separate influences was held based on usage of each scavenger: sodium pyruvate, thiourea, tiron, and L-NAME. Oxidative cell damage was observed through the detection of glutathione depletion and lipid peroxidation. DNA fragmentation and membrane depolarization were observed by TUNEL and DiBAC₄(3) staining agent. Finally, Annexin V/PI and FITC-VAD-FMK were applied to detect apoptosis-like death.

KEY FINDINGS

IPA exhibited antibacterial activity in E. coli through the accumulation of ROS, NO, ONOO^-, and DNA damage, eventually leading to apoptosis-like death. NO and O₂^- exerted the most potent influence on oxidative damage of E. coli, whereas H₂O₂ accounts for the least impact. Moreover, the results reveal the major contribution of ONOO^- in IPA-induced apoptosis-like death in E. coli.

SIGNIFICANCE

This is the first study that introduces the antibacterial activity and apoptosis-like death induced by IPA and suggests the possibility of being an alternative for current antibiotics. Furthermore, the distinct influence of each ROS and NO was analyzed to investigate their contribution to oxidative damage leading to bacterial apoptosis-like death.

Apoptosis-like death-inducing property of tachyplesin I in Escherichia coli

 Antimicrobial peptide (AMP) derived from the horseshoe crab, tachyplesin I (KWCFRVCYRGICYRRCR-NH₂ ), displayed the apparent antimicrobial activity with low cytotoxicity, suggesting its efficacy as an attractive agent but still lacks the understandings regarding its mechanism(s). Hence, the study focused on investigating the antibacterial mode of action of tachyplesin I against Escherichia coli. Based on the reactive oxygen species generation displayed in several antimicrobial effects, the detection of superoxide anion and nitric oxide were verified after tachyplesin I treatment. Substantial increment of two molecules was followed by the imbalance in intracellular ion concentration, noticeably magnesium and calcium. The series of stages led to hydroxyl radical generation with reduced glutathione, followed by damage in DNA due to oxidative stress. Eventually, the apoptosis-like death in E. coli was monitored in DNA fragmentation-dependent manner due to the tachyplesin I treatment, verified by membrane depolarization, caspase-like protein activation, and phosphatidylserine exposure. Accordingly, tachyplesin I induces apoptosis-like death in E. coli, suggesting the potential of being a candidate for regulating bacterial infection.

An MSN-based synergistic nanoplatform for root canal biofilm eradication via Fenton-enhanced sonodynamic therapy

The validity and biocompatibility of irrigating agents are imperative for the success of root canal therapy. The imperfections in the currently available irrigants highlight the fact that more advanced technologies and strategies are required for complete disinfection in endodontic treatments. In the present study, a Fenton reaction-enhanced antimicrobial sonodynamic therapy (SDT) platform was fabricated for root canal disinfection. Firstly, mesoporous silica nanoparticles (MSNs) were synthesized, grafted with an amino group and then conjugated with sonosensitizer protoporphyrin IX (PpIX). Iron ions were then anchored (M@P-Fe) to initiate a Fenton reaction. Nanoparticle characterization by size and zeta potential measurements, scanning electron microscopy, transmission electron microscopy and thermogravimetric analysis confirmed that the platform was successfully developed. Reactive oxygen species (ROS) generation assessment, methylene blue degradation and electron spin resonance assays illustrated upon ultrasound (US) irradiation, that augmented ROS, can be produced by US activated PpIX and iron mediated Fenton reactions from low concentration H2O2 (0.01%). In vitro anti-Enterococcus faecalis efficacy was demonstrated by growth curve and colony forming unit measurements. Confocal laser scanning microscopy and scanning electron microscopy observations illustrated the effectiveness of the platform on in situ biofilm eradication in root canal. Owing to the stronger oxidizing capability and short lifetime of ROS, the Fenton reaction-enhanced SDT can induce detrimental oxidative damage to bacteria upon activation of US while avoiding nonspecific toxicity to cells, which was verified by cytotoxicity evaluations using CCK-8 assay and morphology observation of MC3T3-E1 cells. Compared to commonly used NaClO, this nanoplatform displayed desirable anti-bacterial, anti-biofilm abilities and better biocompatibility. These results highlight that the integrated M@P-Fe + US + H2O2 platform is a promising candidate for US enhanced root canal irrigation and disinfection.

Recent Advances on Stimuli-Responsive Combination Therapy against Multidrug-Resistant Bacteria and Biofilm

The widespread occurrence of infections from multidrug-resistant (MDR) bacteria is a global health problem. It has been amplified over the past few years due to the increase in adaptive traits in bacteria and lack of advanced treatment strategies. Because of the low bioavailability and limited penetration at infected sites, the existing antibiotics often fail to resist bacterial growth. Recently, developed stimuli-responsive drug delivery systems and combinatorial therapeutic systems based on nanoparticles, metal-organic frameworks, hydrogels, and organic chromophores offer the ability to improve the therapeutic efficacy of antibiotics by reducing drug resistance and other side effects. These therapeutic systems have been designed with the relevant chemical and physical properties that respond to specific triggers resulting in spatiotemporal controlled release and site-specific transportability. This review highlights the latest development of single and dual/multistimuli-responsive antibiotic delivery systems for combination therapies to treat MDR bacterial infections and biofilm eradication.

Disinfection characteristics of an advanced rotational hydrodynamic cavitation reactor in pilot scale

Hydrodynamic cavitation is a promising technique for water disinfection. In the present paper, the disinfection characteristics of an advanced hydrodynamic cavitation reactor (ARHCR) in pilot scale were studied. The effects of various flow rates (1.4-2.6 m³/h) and rotational speeds (2600-4200 rpm) on the removal of Escherichia coli (E. coli) were revealed and analyzed. The variation regularities of the log reduction and reaction rate constant at various cavitation numbers were established. A disinfection rate of 100% was achieved in only 4 min for 15 L of simulated effluent under 4200 rpm and 1.4 m³/h, with energy efficiency at 0.0499 kWh/L. A comprehensive comparison with previously introduced HCRs demonstrates the superior performance of the presented ARHCR system. The morphological changes in E. coli were studied by scanning electron microscopy. The results indicate that the ARHCR can lead to serious cleavage and surface damages to E. coli, which cannot be obtained by conventional HCRs. Finally, a possible damage mechanism of the ARHCR, including both the hydrodynamical and sonochemical effects, was proposed. The findings of the present study can provide strong support to the fundamental understanding and applications of ARHCRs for water disinfection.

A novel continuous hydrodynamic cavitation technology for the inactivation of pathogens in milk

Hydrodynamic cavitation is a powerful tool for the enhancement of various processing applications. This study utilizes continuous hydrodynamic cavitation (CHC) for the inactivation of pathogens in milk for the first time. The thermal characteristics, inactivation performance, damage on the nutritional composition, product safety, and cost of the advanced rotational hydrodynamic cavitation reactor at pilot scale were comprehensively investigated. The inactivation results demonstrated that 5.89, 5.53, and 2.99 ± 0.08 log reductions of Escherichia coli, Staphylococcus aureus, and Bacillus cereus were achieved, respectively, at a final treatment temperature of 70 °C for 1-2 s. Moreover, the detrimental effect of CHC on the nutritional composition of milk, including mineral, fat, protein, and vitamin contents, was similar to that of high-temperature short-time method. The change in the concentrations of general bacteria and E. coli, as well as the pH value and acidity of the CHC treated milk stored at 5 °C for 14 days was found to be close to that of low-temperature long-time pasteurized milk. The cost of the present CHC treatment was $0.00268/L with a production rate of 4.2 L/min. CHC appears to be a remarkable method for the continuous processing of milk, as well as other liquid foods with high nutrition and "fresh-picked" flavor, due to its high efficacy, good scalability, high production capacity, and low operating and equipment costs.

Centrality of G6PD in COVID-19: The Biochemical Rationale and Clinical Implications

Introduction: COVID-19 is a novel and devastating disease. Its manifestations vary from asymptomatic to lethal. Moreover, mortality rates differ based on underlying health conditions and ethnicity. We investigated the biochemical rationale behind these observations using machine reasoning by the sci.AI system (https://sci.ai/). Facts were extracted and linked from publications available in nlm.nih.gov and Europe PMC to form the dataset which was validated by medical experts. Results: Based on the analysis of experimental and clinical data, we synthesized detailed biochemical pathways of COVID-19 pathogenesis which were used to explain epidemiological and clinical observations. Clinical manifestations and biomarkers are highlighted to monitor the course of COVID-19 and navigate treatment. As depicted in the Graphical Abstract, SARS-CoV-2 triggers a pro-oxidant (PO) response leading to the production of reactive oxygen species (ROS) as a normal innate defense. However, SARS-CoV-2's unique interference with the antioxidant (AO) system, through suppression of nitric oxide (NO) production in the renin- angiotensin-aldosterone system (RAAS), leads to an excessive inflammatory PO response. The excessive PO response becomes critical in cohorts with a compromised AO system such as patients with glucose-6-phosphate dehydrogenase deficiency (G6PDd) where NO and glutathione (GSH) mechanisms are impaired. G6PDd develops in patients with metabolic syndrome. It is mediated by aldosterone (Ald) which also increases specifically in COVID-19. Conclusion: G6PD is essential for an adequate immune response. Both G6PDd and SARS-CoV-2 compromise the AO system through the same pathways rendering G6PDd the Achilles' heel for COVID-19. Thus, the evolutionary antimalarial advantage of the G6PDd cohort can be a disadvantage against SARS-CoV-2.

A review on hydrodynamic cavitation disinfection: The current state of knowledge

Disinfection, which aims to eliminate pathogenic microorganisms, is an essential step of water treatment. Hydrodynamic cavitation (HC) has emerged as a promising technology for large-scale disinfection without introducing new chemicals. HC, which can effectively induce sonochemistry by mechanical means, creates extraordinary conditions of pressures of ~1000 bar, local hotspots with ~5000 K, and high oxidation (hydroxyl radicals) in room environment. These conditions can produce highly destructive effects on microorganisms in water. In addition, the enhancements of chemical reactions and mass transfers by HC produce the synergism between HC and disinfectants or other physical treatment methods. HC is generated by hydrodynamic cavitation reactors (HCRs), therefore, their performance basically determines the effectiveness, economical efficiency, and applicability of HC disinfection. Therefore, developing high-performance HCRs and revealing the corresponding disinfection mechanisms are the most crucial issues today. In this review, we summarize the fundamental principles of HC and HCRs and recent development in HC disinfection. The energy release from cavitation phenomenon and corresponding mechanisms are elaborated. The performance (effectiveness, treatment ratio, and cost) of various HCRs, effects of treatment conditions on performance, and applicability of HC disinfection are evaluated and discussed. Finally, recommendations are provided for the future progress based on the analysis of previous studies.

UV-Vis quantification of hydroxyl radical concentration and dose using principal component analysis

Hydroxyl radicals (∙OH) are powerful oxidizing species formed naturally in the environment or artificially produced to destroy contaminants in water treatment facilities. Their short lifetime and high reactivity, however, present a significant challenge to quantifying their concentration in solution. Herein, we developed a novel method to accurately measure the steady-state ∙OH concentration and total ∙OH dose produced during the UV photolysis of hydrogen peroxide (H₂O₂) by monitoring the loss of salicylic acid (SA). This information can be acquired using only benchtop UV-Vis spectroscopy, thus expanding measurement capabilities of resource-limited laboratories by eliminating the need for sophisticated instrumentation. To improve the precision with which the rate of SA loss was measured compared to previous methods, we applied principal component analysis (PCA) to fit the UV-Vis spectra collected during SA exposure to ∙OH. For our experimental conditions consisting of 12 mL solutions composed of ≤ 100 mM H₂O₂ and 0.07 mM SA, the steady-state ∙OH concentration throughout the complete photolysis of H₂O₂ was 1.33 × 10^-11 M ± 1.14 × 10^-12 M. This represents more than a ten-fold improvement in reducing the uncertainty of the measurement, with respect to narrowing the 95 % confidence interval, compared to a previous method that employed matrix analysis to process the spectra. Furthermore, the variance of the measured ∙OH concentrations was reduced by a factor of 100 compared to previous methods. Using PCA, the limit-of-detection and limit-of-quantitation for ∙OH are 5.33 × 10^-13 M and 1.23 × 10^-12 M, respectively. By developing quantitative relationships among ∙OH concentration, H₂O₂ concentration, and UV exposure time, we also show how to calculate the equivalent exposure to ∙OH generated in natural aquatic environments by indirect photolysis. Finally, we use this methodology to demonstrate that the presence of suspended carbonaceous nanoparticles at concentrations as high as 300 ppm does not affect ∙OH concentration.

Elucidating sulfate radical-mediated disinfection profiles and mechanisms of Escherichia coli and Enterococcus faecalis in municipal wastewater

Practical applications of disinfection technologies for engineered waters require an in‒depth understanding of disinfection profiles and mechanisms of pathogenic bacteria in a complex matrix. This study investigated the inactivation of E. coli and E. faecalis by SO₄^•-, an emerging advanced disinfectant, in ultrapure water (UPW) and wastewater effluent (WE). Based on the bacterial inactivation kinetics in UPW in a zerovalent iron/peroxydisulfate system, the second order rate constants (k) for SO₄^•- reacting with E. coli and E. faecalis were measured to be (1.39 ± 0.1) × 10⁹ M^-1 s^-1 and (6.71 ± 0.1) × 10⁹ M^-1 s^-1, respectively. The morphological images of both bacteria by the scanning electron microscope indicated that SO₄^•- initiates oxidative reactions on the wall/membranes, causing their irreversible damage, ultimately affecting membrane permeability and physiological functions. To profile the inactivation kinetics of two strains of bacteria in WE matrix, a mechanistic process‒based model with the obtained k values was developed. Sensitivity and uncertainty analyses indicated that the key parameters for the model predictions were the concentrations of halide ions (i.e., Br^- and Cl^-) in WE and their k values reacting with SO₄^•- accounting for >80% of uncertainty or variance expected in predicted bacterial inactivation. This model allows precise estimation of required disinfectant dose even in complex water matrices, shedding lights on the extension of application of SO₄^•-‒based technology in wastewater treatments.

Tuning the ATP-triggered pro-oxidant activity of iron oxide-based nanozyme towards an efficient antibacterial strategy

An alarming increase in bacterial resistance towards various types of antibiotics makes it imperative to design alternate or combinational therapies to treat stubborn bacterial infections. In this perspective, emerging tools like nanozymes, nanomaterials with biological enzyme like characteristics, are being utilised to control infections caused by bacterial pathogens. Among several nanozymes used for antibacterial applications, Fe₃O₄ nanoparticles (NP) received great attention due to their effective peroxidase like activity. The pH dependent peroxidase activity of Fe₃O₄ NP results in generation of OH radical via the unique Fenton chemistry of iron. However, their pH dependent activity is restricted to acidic environment and dramatic loss in antibacterial activity is observed at near neutral pH. Here we describe a novel strategy to overcome the pH lacunae of citrate coated Fe₃O₄ NP by utilizing adenosine triphosphate disodium salt (ATP) as a synergistic agent to accelerate the OH radical production and restore its antibacterial activity over a wide range of pH. This synergistic combination (30 µg/mL Fe₃O₄ NP and 2.5 mM ATP) shows a high bactericidal activity against both gram positive (B. subtilis) and gram negative (E. coli) bacterial strains, in presence of H₂O₂, at neutral pH. The synergistic effect (Fe₃O₄ NP + ATP) is determined from the viability assessment and membrane damage studies and is further confirmed by comparing the concentration of generated OH radicals. Over all, this study illustrates ATP assisted and OH-mediated bactericidal activity of Fe₃O₄ nanozyme at near neutral pH.

Nano-Enhanced Drug Delivery and Therapeutic Ultrasound for Cancer Treatment and Beyond

While ultrasound is most widely known for its use in diagnostic imaging, the energy carried by ultrasound waves can be utilized to influence cell function and drug delivery. Consequently, our ability to use ultrasound energy at a given intensity unlocks the opportunity to use the ultrasound for therapeutic applications. Indeed, in the last decade ultrasound-based therapies have emerged with promising treatment modalities for several medical conditions. More recently, ultrasound in combination with nanomedicines, i.e., nanoparticles, has been shown to have substantial potential to enhance the efficacy of many treatments including cancer, Alzheimer disease or osteoarthritis. The concept of ultrasound combined with drug delivery is still in its infancy and more research is needed to unfold the mechanisms and interactions of ultrasound with different nanoparticles types and with various cell types. Here we present the state-of-art in ultrasound and ultrasound-assisted drug delivery with a particular focus on cancer treatments. Notably, this review discusses the application of high intensity focus ultrasound for non-invasive tumor ablation and immunomodulatory effects of ultrasound, as well as the efficacy of nanoparticle-enhanced ultrasound therapies for different medical conditions. Furthermore, this review presents safety considerations related to ultrasound technology and gives recommendations in the context of system design and operation.

Effects of cavitation on different microorganisms: The current understanding of the mechanisms taking place behind the phenomenon. A review and proposals for further research

A sudden decrease in pressure triggers the formation of vapour and gas bubbles inside a liquid medium (also called cavitation). This leads to many (key) engineering problems: material loss, noise, and vibration of hydraulic machinery. On the other hand, cavitation is a potentially useful phenomenon: the extreme conditions are increasingly used for a wide variety of applications such as surface cleaning, enhanced chemistry, and wastewater treatment (bacteria eradication and virus inactivation). Despite this significant progress, a large gap persists between the understanding of the mechanisms that contribute to the effects of cavitation and its application. Although engineers are already commercializing devices that employ cavitation, we are still not able to answer the fundamental question: What precisely are the mechanisms how bubbles can clean, disinfect, kill bacteria and enhance chemical activity? The present paper is a thorough review of the recent (from 2005 onward) work done in the fields of cavitation-assisted microorganism's destruction and aims to serve as a foundation to build on in the next years.

Impact of ROS-Induced Damage of TCA Cycle Enzymes on Metabolism and Virulence of Salmonella enterica serovar Typhimurium

Salmonella enterica serovar Typhimurium (STM) is exposed to reactive oxygen species (ROS) originating from aerobic respiration, antibiotic treatment, and the oxidative burst occurring inside the Salmonella-containing vacuole (SCV) within host cells. ROS damage cellular compounds, thereby impairing bacterial viability and inducing cell death. Proteins containing iron–sulfur (Fe–S) clusters are particularly sensitive and become non-functional upon oxidation. Comprising five enzymes with Fe–S clusters, the TCA cycle is a pathway most sensitive toward ROS. To test the impact of ROS-mediated metabolic perturbations on bacterial physiology, we analyzed the proteomic and metabolic profile of STM deficient in both cytosolic superoxide dismutases (ΔsodAB). Incapable of detoxifying superoxide anions (SOA), endogenously generated SOA accumulate during growth. ΔsodAB showed reduced abundance of aconitases, leading to a metabolic profile similar to that of an aconitase-deficient strain (ΔacnAB). Furthermore, we determined a decreased expression of acnA in STM ΔsodAB. While intracellular proliferation in RAW264.7 macrophages and survival of methyl viologen treatment were not reduced for STM ΔacnAB, proteomic profiling revealed enhanced stress response. We conclude that ROS-mediated reduced expression and damage of aconitase does not impair bacterial viability or virulence, but might increase ROS amounts in STM, which reinforces the bactericidal effects of antibiotic treatment and immune responses of the host.

Use of photo-Fenton's reaction by 400-nm LED light for endodontic disinfection: A preliminary in vitro study on Enterococcus faecalis

One of the biggest challenges in endodontics is the complete disinfection of root canals. In addition to mechanical preparation, the technique traditionally also involves channel disinfection with other agents such as sodium hypochlorite, hydrogen peroxide, chlorhexidine, or a combination of these. Some bacterial species are particularly resistant to eradication. Using Enterococcus faecalis in this preliminary study, we tested the bactericidal effectiveness of the Fenton reaction and the photo-Fenton reaction using an LED light with a 400-nm wavelength. Discs of hydroxyapatite were incubated in brain-heart broth contaminated with Enterococcus faecalis. After 4days, they were decontaminated with different bactericidal agents, including some with proven and well-known efficacy (5% sodium hypochlorite and 3% hydrogen peroxide) and other treatments using solutions of 1.5% hydrogen peroxide and 0.15% iron gluconate (Fenton reaction) plus LED light at a Fluence of 4.0J/cm² (photo-Fenton reaction). The photo-Fenton reaction demonstrated comparable performance to that of sodium hypochlorite in eliminating Enterococcus faecalis.

Effects of photodynamic therapy, 2 % chlorhexidine, triantibiotic mixture, propolis and ozone on root canals experimentally infected with Enterococcus faecalis: an in vitro study

The aim of this study was to evaluate the antibacterial effect of photodynamic therapy (PDT), 2 % chlorhexidine (CHX). The teeth were contaminated with 0.1 mL Enterococcus faecalis (3 × 10⁸ cell/mL) and randomized into eight treatment groups: Group 1 (2.5 % NaOCl); Group 2 (PDT); Group 3 (2 % CHX); Group 4 (TAM); Group 5 (propolis), Group 6 (ozone), Group 7 (positive control) and Group 8 (negative control). Following treatment, the canal content was sampled. The samples were cultured in triplicate on blood agar plates to determine the number of colony forming units (CFU)/mL. The teeth were analyzed by SEM to determine the percentage of area with contamination and debris. The group with the lowest CFU/mL count was the ozone group, which obtained similar values to the PDT group. SEM images showed that 2.5 % NaOCL group showed the lowest percentage of contaminated area. Applications of PDT, 2 % CHX, TAM, propolis and ozone showed antibacterial potential similar to 2.5 % NaOCL.

Ultrasound-enhanced chemiluminescence tomography in biological tissue

This paper reports ultrasound-assisted optical imaging of chemiluminescent probes in biological tissue. A focused low power ultrasound sonochemically enhances a peroxyoxalate chemiluminescence (CL) that involves indocyanine green (ICG) as luminescent pigments. By scanning the focus, it produces tomographic images of CL in scattering media. The authors demonstrate imaging using a slab of porcine muscle measuring 50 × 50 × 75 mm, in which a capsuled CL reagent is embedded at 25 mm depth. Spatial resolution of imaging and concentration characteristics of CL reagents to enhanced CL intensity are also studied to evaluate the potential for use in bio-imaging applications with exploring the CL enhancement mechanisms. CL enhancement ratio, defined as the ratio of ultrasonically enhanced CL intensity to the base intensity without ultrasound irradiation, was found to be constant even in varying ICG and oxidizer concentrations, implying to be applicable for quantitative determination of these molecules.