Determination of Intracellular Levels of Reactive Oxygen Species Using the 2,7-dichlorofluorescein Diacetate Assay by Kinetic Monte Carlo Simulation

Rapid identification of bacteria by the pattern of redox reactions rate using 2',7'-dichlorodihydrofluorescein diacetate

Bacterial infection is a life-threatening situation, and its rapid diagnosis is essential for treatment. Apart from medical applications, rapid identification of bacteria is vital in the food industry or the public health system. There are various bacterial identification techniques, including molecular-based methods, immunological approaches, and biosensor-based procedures. The most commonly used methods are culture-based methods, which are time-consuming. The objective of this study is to find a fingerprint of bacteria to identify them. Three strains of bacteria were selected, and seven different concentrations of each bacterium were prepared. The bacteria were then treated with two different molar concentrations of the fluorescent fluorophore, dichlorodihydrofluorescein diacetate for 30 minutes. Then, using the fluorescence mode of a multimode reader, the fluorescence emission of each bacterium is scanned twice during 60 minutes. Plotting the difference between two scans versus the bacteria concentration results in a unique fluorescence pattern for each bacterium. Observation of the redox state of bacteria, during 90 minutes, results in a fluorescence pattern that is clearly a fingerprint of different bacteria. This pattern is independent of fluorophore concentration. Mean Squares Errors (MSE) between the fluorescence patterns of similar bacteria is less than that of different bacteria, which shows the method can properly identify the bacteria. In this study, a new label-free method is developed to detect and identify different species of bacteria by measuring the redox activity and using the fluorescence fluorophore, dichlorodihydrofluorescein diacetate. This robust and low-cost method can properly identify the bacteria, uses only one excitation and emission wavelength, and can be simply implemented with current multimode plate readers.

A new approach to study the degradation of the organic pollutants by A-doped MxOy/B photocatalysts

This work presents a new approach and a comprehensive mechanism to study the kinetics of the photodegradation of the organic pollutants. The vital role of various operational factors on the degradation of the organic pollutants is explained using this method. The proposed approach is based on the simple strategies and a powerful computational method. Two new variables "the effective concentration of photon" (I_eff) and "the effective concentration of the reactive centers" (RC) are defined to better understand the effect of operational parameters on the organic pollutant photodegradation. The optimum conditions of the photocatalytic degradation can be determined with the help of this method. This approach was used to study the kinetics of photodegradation of the organic pollutants on the [Formula: see text] photocatalysts. The provided mechanism has been examined with the some experimental data. The high correlations between the experimental data and the fitting results under different conditions prove this mechanism could be reliable.

Introduction of the Effective Photon Concentration Variable for Studying the Mechanism of Crystal Violet Photodegradation

In this work, we have proposed a new approach to study the mechanism of crystal violet (CV) photodegradation on TiO₂ surface using kinetic Monte Carlo simulation. The TiO₂ surface was considered as a set of reactive centers, which is essential in dye photodegradation. A new variable "the effective photon concentration" (I_eff ) is defined. A detailed chemical understanding of the photocatalytic reaction is provided. This approach provides a simple and effective method to find the optimal conditions of the studied system. This goal was achieved by investigating the effects of some operational parameters, including initial concentration of CV, pH, loading TiO₂ , light intensity and volume, on the degradation percent, and also, on the effective photon concentration. The perfect agreements between the experimental and simulated data at different conditions confirmed the proposed approach for describing the CV photodestruction. Also, the simulation results indicated that: (1) a significant fraction of the scattered UV irradiation into the reaction vessel does not lead to charge carrier generation; (2) the generation and recombination of charge carriers have crucial roles in the photodegradation. This is the first time that a method based on the reactive centers is employed to investigate the dye degradation by a photocatalyst.

Reactive oxygen species-responsive silk sericin microcapsules used for antioxidative stress damage

Silk sericin microcapsules loaded with horseradish peroxidase (HRP) are prepared through protein self-assembly in a green environment containing enzymes to protect liver cells from alcohol damage. Load content and release dynamics of HRP in sericin microcapsules are investigated. The role of HRP-loaded microcapsules in hydrogen peroxide (H₂ O₂ ) degradation is demonstrated using electrochemical method. Furthermore, the effect of the HRP-loaded microcapsules on cells and intracellular reactive oxygen species (ROS) level is evaluated using an alcohol damage model in vitro. Results show that HRP can be loaded effectively in the sericin microcapsules and can be released ROS-responsively from microcapsules. Cell survival rate increases after suffering from alcohol damage due to the presence of HRP-loaded microcapsule, and the active oxygen content in cells is maintained at a stable level even when it remained in an environment with high alcohol concentration. We believe that the internalized sericin microcapsules maintain HRP activity intracellularly, allow controlled HRP release within a host cell, and show excellent ability in antioxidative stress injury.

Kinetic study of antibiotic ciprofloxacin ozonation by MWCNT/MnO2 using Monte Carlo simulation

Kinetic Monte Carlo simulation was used to investigate kinetics of antibiotic ciprofloxacin degradation by direct and heterogeneous catalytic (MnO2 and carbon nano-tube loaded with MnO2) ozonation. The reaction kinetic mechanisms of each system have been obtained. The rate constant values for the each step of the reaction mechanisms were attained as adjustable parameters by kinetic Monte Carlo simulation. The carbon nano-tube loaded with MnO2 plays important role as catalyst in the ciprofloxacin ozonation by increasing reactivity of ozone and ciprofloxacin drug on the surface of carbon nano-tube. Optimized amount of ozone and catalysts were obtained via studying the effect of inlet ozone concentration and initial amount of catalyst on the rate of ciprofloxacin degradation using Monte Carlo simulation. The simulation results of this study have reasonably agreement with the present experimental data for the ozonation of ciprofloxacin drug.

Study of photo-oxidative reactivity of sunscreening agents based on photo-oxidation of uric acid by kinetic Monte Carlo simulation

In the present study, the mechanism of free radical production by light-reflective agents in sunscreens (TiO2, ZnO and ZrO2) was obtained by applying kinetic Monte Carlo simulation. The values of the rate constants for each step of the suggested mechanism have been obtained by simulation. The effect of the initial concentration of mineral oxides and uric acid on the rate of uric acid photo-oxidation by irradiation of some sun care agents has been studied. The kinetic Monte Carlo simulation results agree qualitatively with the existing experimental data for the production of free radicals by sun care agents.

Kinetic investigation of photo-catalytic activity of TiO2/metal nanocomposite in phenol photo-degradation using Monte Carlo simulation

Kinetic Monte Carlo simulation was applied to study the kinetics and photo-catalytic activity mechanism of TiO₂ anatase, P25, Au/TiO₂, Pd/TiO₂ and Au–Pd/TiO₂ applied in photo-degradation of water pollutants including phenol.