Decomposition of DNA staining agent ethidium bromide by gamma irradiation: Conditions, kinetics, by-products, biological activity, and removal from wastewater

Ethidium Bromide Degradation by Cold Atmospheric Plasma in Water and the Assessment of Byproduct Toxicity for Environmental Protection

Ethidium bromide (Et-Br) is a widely used fluorescent dye in molecular biology and biotechnology laboratories for visualizing nucleic acids in agarose gel electrophoresis. However, concerns have been raised about its environmental impact and potential health risks due to its persistence and toxicity. The potential accumulation and long-term effects on the environment necessitate the removal of Et-Br from water. This study investigates the potential of novel cold plasma technology for the degradation of Et-Br. Cold atmospheric plasma (CAP) is an environmentally friendly technology that does not produce secondary pollutants and generates a variety of potent chemical reactive oxidants such as hydroxyl radicals (•OH), H2O2, NO2, and NO3. In this study, Et-Br was treated with CAP for 15 min without the addition of any chemicals, resulting in substantial removal of Et-Br. The degradation kinetics revealed that the CAP-treated Et-Br followed a pseudo-first-order reaction, dependent on the treatment time of CAP. The degradation of Et-Br by CAP is distinctly evident through the results obtained from both high-performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometry (LC-MS) analyses, providing clear evidence of the occurrence of degradation. Furthermore, toxicity analyses of the degradation products were conducted by evaluating the Et-Br intercalation ability with DNA before and after treatment of Et-Br with CAP. To supplement the assessment, the binding of Et-Br with BSA has also been studied before and after CAP treatment. The impact of CAP-treated Et-Br on the growth and colony-forming unit (CFU) counts of Escherichia coli was also evaluated. Results indicated an increase in bacterial growth with an increase in CAP treatment time, suggesting that the degradation products of Et-Br using CAP were nontoxic. This study highlights the potential of CAP as a clean and efficient technology for the degradation of Et-Br, presenting a promising solution for mitigating its environmental and health risks.

Proper application of DNA dyes in agarose gel electrophoresis

Various dyes are used to visualize DNA bands in agarose gel electrophoresis (AGE) by the methods of pre- or post-staining. The DNA dye user's guides generally state that the binding of the dye to DNA will affect DNA mobility in electrophoresis, thus recommending post-staining for accurate measurement of DNA size. However, many AGE performers prefer pre-staining procedures for reasons such as convenience, real-time observation of DNA bands, and/or the use of a minimal amount of dye. The detrimental effect of the dye on DNA mobility and the associated risk for inaccurate measurement of DNA size are often overlooked by AGE performers. Here we quantitatively determine the impact on DNA migration imposed by frequently used dyes, including GelRed, ethidium bromide (EB), and Gold View. It was observed that pre-staining with GelRed and EB significantly slowed down DNA migration to cause as much as 39.1% overestimation on the size of sample DNA, whereas Gold View had little effect. The slowdown of DNA migration increased with dye concentration until it plateaued when the dye concentration reached a saturated level. Thus, to take advantage of pre-staining, saturated levels of DNA dyes should always be applied for both DNA samples and DNA markers to ensure a fair comparison of DNA sizes. In addition, GelRed and EB display much higher sensitivity than Gold View in the detection of DNA bands in post-staining. The saturated concentrations, cost considerations, and other useful features of these frequently used dyes are summarized for the information of AGE performers.

The performance and pathway of benzothiazole degradation by electron beam irradiation

Benzothiazole (BTH) is a typical refractory heterocyclic compound that can be used as a photosensitive material in organic synthesis and conditional plant resource research. The extensive use of BTH has led to high BTH concentrations in natural environment, such as in tap water and urine, which tend to inhibit animal hormone synthesis and induce genotoxicity. Traditional wastewater treatment processes cannot effectively remove BTH. Therefore, we aimed to use the electron beam method, an emerging method for pollutant degradation, to degrade BTH in water. Experiments showed that BTH can be effectively degraded (up to 90%) when the electron beam reaches 5 kGy and irradiation conformed perfectly to the pseudo first-order kinetics model. Experimental results showed that acidic conditions are more favorable for electron beam degradation of BTH, while the degradation of most other inorganic ions is inhibited (except SO₄^2-). Hydroxyl radicals (•OH) was confirmed to play a major role in degradation by the experiment, and the mineralization rate was greatly increased by the addition of H₂O₂ and K₂S₂O₈. In addition, our experimental and theoretical calculations showed that the degradation of BTH occurred mainly through the opening of the benzene ring. Theoretical calculations showed that the toxicity of BTH decreased significantly after electron beam degradation, making it an effective way to degrade BTH.

Heterogeneous irradiation system: enhanced degradation of methylene blue by electron beam irradiation combined with graphite carbon nitride/carbon nanodots

In the present work, the degradation of methylene blue (MB) was investigated by electron beam irradiation combined with graphite carbon nitride/carbon nanodots (EBI&g-C₃N₄/CDs). In comparison with EBI alone, the EBI&g-C₃N₄/CDs method showed a higher removal efficiency of high concentrations of MB (500 mg L^-1) from aqueous solution. Investigation on the effect of the synthesized g-C₃N₄/CDs revealed that CDs and g-C₃N₄ were both contributing factors, while the latter could enhance the degradation of MB through surface reactions that occurred after adsorption. Experiments on the existence of hydrogen peroxide revealed the synergistic effect between g-C₃N₄/CDs and hydrogen peroxide. An excellent degradation effect was obtained at natural pH, and the total organic carbon was significantly reduced. Regeneration experiments revealed that the g-C₃N₄/CDs material has good stability and reusability. The studies in the presence of assorted radical scavengers suggested that ·OH played a vital role in the degradation process and a total of 17 intermediates were detected using liquid chromatograph-mass spectrometer (LC-MS) analysis. The possible degradation mechanisms of MB were proposed.

Degradation of Organic Dyes Using the Ionizing Irradiation Process in the Presence of the CN/CD3/Fe6 Composite: Mechanistic Studies

Organic dyes are ubiquitous pollutants in various aquatic environments as they are produced in abundance and used widely. In the present work, the degradation and mineralization of various organic dyes such as methylene blue (MB), methyl orange (MO), and rhodamine B (RhB), following the electron beam irradiation method in the presence of a graphitic carbon nitride/carbon nanodots/Fe(II) (CN/CD3/Fe6) composite, were studied. The removal efficiency of MB reached 81.7% under conditions of electron beam irradiation (EBI) when the total irradiation dose was 5 kGy. This increased to 91.2% in the presence of the CN/CD3/Fe6 composite. The mineralization efficiency increased from 30.1 to 47.3% when the composite was added, and the total irradiation dose was 20 kGy. The removal efficiency of organic dyes was not significantly affected in the pH range of 3-11. Results from cyclic experiments conducted using MB degradation indicated that the CN/CD3/Fe6 composite exhibited good stability and reusability even after five irradiation cycles. Results from scavenging experiments revealed that •OH was the predominant reactive species during the MB degradation process. Intermediates produced in the synergistic system (EBI&CN/CD3/Fe6 system) consisting of the CN/CD3/Fe6 composite and EBI were detected using the liquid chromatography-mass spectrometry (LC-MS) technique. Based on the results, the possible degradation mechanism and pathways for MB were proposed.

Degradation of anticorrosive agent benzotriazole by electron beam irradiation: Mechanisms, degradation pathway and toxicological analysis

Benzotriazole (BTA), which is extensively served as household and engineering agent, is one of the emerging and persistent contaminants. Despite the spirit to remove BTA is willing, the traditional wastewater treatments are weak. Therefore, the degradation of BTA via electron beam was systematically explored in this study. It turned out that after 5.0 kGy irradiation, even 87.5 mg L^-1 BTA could be completely removed, and the irradiation conformed perfectly to the pseudo first-order kinetics model. The effects of solution pH, inorganic anions (CO₃^2-, HCO₃^-, NO₃^-, NO₂^-, SO₄^2-, SO₃^2-, Cl^-), and gas atmosphere were all explored. And results indicated that oxidative hydroxyl radicals played critical role in BTA irradiation. Additionally, presence of H₂O₂ and K₂S₂O₈ promoted significantly not only degradation extent but also mineralization efficiency of BTA due to they both augmented the generation of oxidative free radicals. Moreover, by combining theoretical calculations with experimental results, it could be inferred that degradation of BTA was mainly carried out by the benzene ring-opening. Further toxicity evaluation proved that as irradiation proceeded, the toxicity alleviated. Taken together, there were various indications that BTA could be effectively eliminated by electron beam irradiation in aquatic environments.