Toxic By-products Research Articles

Advancing Insights into Pediatric Macular Diseases: A Comprehensive Review.

Pediatric macular disorders are a diverse group of inherited retinal diseases characterized by central vision loss due to dysfunction and degeneration of the macula, the region of the retina responsible for high-acuity vision. Common disorders in this category include Stargardt disease, Best vitelliform macular dystrophy, and X-linked retinoschisis. These conditions often manifest during childhood or adolescence, with symptoms such as progressive central vision loss, photophobia, and difficulty with fine visual tasks. Underlying mechanisms involve genetic mutations that disrupt photoreceptor and retinal pigment epithelium function, accumulating toxic byproducts, impaired ion channel activity, or structural degeneration. Advances in imaging modalities like optical coherence tomography and fundus autofluorescence have improved diagnostic accuracy and disease monitoring. Emerging therapies are transforming the treatment landscape. Gene therapy and genome editing hold promise for addressing the genetic basis of these disorders, while stem cell-based approaches and pharmacological interventions aim to restore retinal function and mitigate damage. Personalized medicine, driven by genomic sequencing, offers the potential for tailored interventions. Despite current challenges, ongoing research into molecular mechanisms, advanced imaging, and innovative therapies provides hope for improving outcomes and quality of life in children with macular disorders.

Synergistic activation of peroxydisulfate by photothermal and FeS2-loaded air-laid cloth in a shallow continuous flow reactor.

Synergistic activation of persulfate by photothermal and solid catalysts is an effective method for degrading organic pollutants. However, the batch reaction mode not only fails to fully utilize photothermal, but also makes it hard to separate the solid catalysts from the reaction solution. In this work, a shallow continuous flow way of effluent was set up for synergistic activation of peroxydisulfate (PDS) by photothermal and FeS2-loaded air-laid cloth (FeS2-ALC). The degradation efficiency of carbamazepine (CBZ) was significantly enhanced with a pseudo-first-order kinetic constant of 0.0359 min-1, which is 180, 40 and 10 times higher than that of the photothermal/ALC, photothermal/FeS2-ALC and photothermal/PDS processes, respectively. The enhanced efficiency was partly due to the absorption of sunlight by FeS2-ALC to heat up the reaction solution which in turn can use photothermal to activate PDS, and partly due to the activation of the PDS by Fe2+ from FeS2-ALC and the promotion of Fe3+/Fe2+ cycling via S2-. Parameters such as reaction conditions, hydraulic conditions and water quality parameters affecting degradation efficiency were investigated. A possible degradation pathway was proposed and the toxicities of byproducts were tested. Finally, cycling experiments and outdoor experiments demonstrated that the photothermal/FeS2-ALC/PDS process has potential for practical wastewater treatment.

Nanoconfinement-Enabled Resistance to Water Matrix Components for Selective Degradation of Micropollutants.

Despite recent substantial advances in water treatment, the ability to selectively degrade trace micropollutants in real waters with complex matrix components remains a grand challenge. Here we report rational crafting of graphene oxide (GO)-wrapped defective TiO2 composite catalysts that creates nanoscopic confinement over the TiO2 surface within GO, thereby enabling the selective degradation of micropollutants through effectively excluding natural organic matter (NOM) and anions from the nanoconfined catalytic sites. In contrast to unconfined counterparts, the nanoconfined composite catalysts retain high degradation efficiency when exposed to various concentrations of NOM and anions, even in real water samples. Oxygen vacancies in TiO2 promote electron separation and oxygen adsorption, leading to a 4.9-fold increase in hydroxyl radical concentration within the nanoconfined space compared to the bulk solution. In-situ X-ray photoemission spectroscopy and Raman spectroscopy unveil the nanoconfined catalytic sites on the TiO2 surface, where micropollutants smaller than the pores of GO are effectively degraded, while NOM with a larger size is excluded by GO. Furthermore, the formation of toxic disinfection byproducts is well controlled due to the exclusion of NOM. This work provides a simple yet viable strategy for designing 2D material-wrapped catalysts to selectively degrade target micropollutants in complex real waters.

A parallel bioreactor strategy to rapidly determine growth-coupling relationships for bioproduction: a mevalonate case study

BackgroundThe climate crisis and depleting fossil fuel reserves have led to a drive for ‘green’ alternatives to the way we manufacture chemicals, and the formation of a bioeconomy that reduces our reliance on petrochemical-based feedstocks. Advances in Synthetic biology have provided the opportunity to engineer micro-organisms to produce compounds from renewable feedstocks, which could play a role in replacing traditional, petrochemical based, manufacturing routes. However, there are few examples of bio-manufactured products achieving commercialisation. This may be partially due to a disparity between academic and industrial focus, and a greater emphasis needs to be placed on economic feasibility at an earlier stage. Terpenoids are a class of compounds with diverse use across fuel, materials and pharmaceutical industries and can be manufactured biologically from the key intermediate mevalonate.ResultsHere, we report on a method of utilising parallel bioreactors to rapidly map the growth-coupling relationship between the specific product formation rate, specific substrate utilisation rate and specific growth rate. Using mevalonate as an example product, a maximum product yield coefficient of 0.18 gp/gs was achieved at a growth rate (μ) of 0.34 h−1. However, this process also led to the formation of the toxic byproduct acetate, which can slow growth and cause problems during downstream processing. By using gene editing to knock out the ackA-pta operon and poxB from E. coli BW25113, we were able to achieve the same optimum production rate, without the formation of acetate.ConclusionsWe demonstrated the power of using parallel bioreactors to assess productivity and the growth-coupling relationship between growth rate and product yield coefficient of mevalonate production. Using genetic engineering, our resultant strain demonstrated rapid mevalonate formation without the unwanted byproduct acetate. Mevalonate production is quantified and reported in industrially relevant units, including key parameters like conversion efficiency that are often omitted in early-stage publications reporting only titre in g/L.

Functional Imaging Methods for Investigating 3D Choroid Plexus Organoids.

The choroid plexus (ChP) is a vital brain structure that produces cerebrospinal fluid (CSF) and forms a selective barrier between the blood and CSF, essential for brain homeostasis. Composed of secretory epithelial cells, connective stroma, and a fenestrated vascular network, the ChP supports nutrient transport, immune surveillance, and the clearance of toxic by-products. Despite its significance in maintaining cerebral function, the mechanisms underlying its development and maturation remain poorly understood. Recent advancements, such as the creation of stem cell-derived three-dimensional (3D) ChP organoid model, provide a promising platform for studying these processes. The ChP organoid model replicates key developmental stages and functions of the ChP, including CSF secretion and barrier formation. Additionally, they offer unique opportunities to investigate the impacts of drugs, pathogens, and toxins on the blood-CSF barrier. This study highlights imaging techniques critical for the characterization and utilization of ChP organoids, illustrating their value in advancing our understanding of ChP biology and its role in health and disease.

A Comparative Study of Advanced Oxidation Processes for the Removal of the Antibiotic Sulfadoxine from Water—Transformation Products and Toxicity

Sulfonamides, including sulfadoxine (SDX), are widely used antibiotics, particularly for malaria treatment. However, their extensive use has led to environmental pollution, microbial resistance, and public health risks. Advanced Oxidation Processes (AOPs) offer promising methods to degrade such pollutants in water, though they may generate more toxic by-products. This study evaluates three AOPs with different hydroxyl radical generation principles: the Fenton reagent (H2O2/Fe2+), hydrogen peroxide photolysis (UV-C/H2O2), and heterogeneous photocatalysis (UV-A/TiO2). Heterogeneous photocatalysis showed superior performance, achieving 100% degradation and 77% mineralization under optimized conditions. Further analysis explored the effects of UV dose, catalyst concentration, and pH on process efficiency. The influence of water matrices, including Ultrapure Water (UW), Tap Water (TW), and Surface Water (SW) from the Aliakmonas River, was also examined. High-Resolution Mass Spectrometry identified 11 SDX transformation products formed during photocatalysis, with their formation mechanisms reported for the first time. An ecotoxicity assessment using ECOSAR software revealed insights into the potential environmental impact of these by-products.

Actinomycete-Derived Pigments: A Path Toward Sustainable Industrial Colorants.

Pigment production has a substantial negative impact on the environment, since mining for natural pigments causes ecosystem degradation, while synthetic pigments, derived from petrochemicals, generate toxic by-products that accumulate and persist in aquatic systems due to their resistance to biodegradation. Despite these challenges, pigments remain essential across numerous industries, including the cosmetic, textile, food, automotive, paints and coatings, plastics, and packaging industries. In response to growing consumer demand for sustainable options, there is increasing interest in eco-friendly alternatives, particularly bio-based pigments derived from algae, fungi, and actinomycetes. This shift is largely driven by consumer demand for sustainable options. For bio-pigments, actinomycetes, particularly from the Streptomyces genus, have emerged as a promising green source, aligning with global sustainability goals due to their renewability and biodegradability. Scale-up of production and yield optimization challenges have been circumvented with the aid of biotechnology advancements, including genetic engineering and innovative fermentation and extraction methods, which have enhanced these bio-pigments' viability and cost-competitiveness. Actinomycete-derived pigments have successfully transitioned from laboratory research to commercialization, showcasing their potential as sustainable and eco-friendly alternatives to synthetic dyes. With the global pigment market valued at approximately USD 24.28 billion in 2023, which is projected to reach USD 36.58 billion by 2030, the economic potential for actinomycete pigments is extensive. This review explores the environmental advantages of actinomycete pigments, their role in modern industry, and the regulatory and commercialization challenges they face, highlighting the importance of these pigments as promising solutions to reduce our reliance on conventional toxic pigments. The successful commercialization of actinomycete pigments can drive an industry-wide transition to environmentally responsible alternatives, offering substantial benefits for human health, safety, and environmental sustainability.

Dynamic impact of polyethylene terephthalate nanoplastics on antibiotic resistance and microplastics degradation genes in the rhizosphere of Oryza sativa L.

This study examined the effects of polyethylene terephthalate (PET) nanoplastics on the rhizosphere of Oryza sativa L., focusing on dynamic changes and interactions among microbial communities, antibiotic resistance genes (ARGs) and microplastic degradation genes (MDGs). PET exposure altered the structure and function of soil microbial, enabling specific microbial groups to thrive in polluted environments. High-dose PET treatments markedly increased the abundance and dissemination of ARGs, primarily via resistance mechanisms such as antibiotic efflux and target alteration. By providing additional carbon sources and surfaces for microbial attachment, PET stimulated the growth of microorganisms harboring MDGs, resulting in an increase in MDGs abundance. The elevated expression of MDGs facilitated the propagation of ARGs, with overlapping host microorganisms suggesting that certain microbial groups exhibit dual metabolic capabilities, enabling them to endure both antibiotic and microplastic pressures. Toxic byproducts of microplastic degradation, such as mono-ethylhexyl phthalate, further promoted ARGs dissemination by increasing horizontal gene transfer frequency. Structural equation modeling revealed that PET indirectly influenced ARGs and MDGs expression by altering soil C/N ratio, available phosphorus, and enzyme activities. Thus, nanoscale PET exacerbates ecological risks to soil microbial communities by driving co-propagation of ARGs and MDGs, highlighting the persistent threat of composite pollution to agroecosystems.

Lipid Oxidation at the Crossroads: Oxidative Stress and Neurodegeneration Explored in Caenorhabditis elegans.

Lipid metabolism plays a critical role in maintaining cellular integrity, especially within the nervous system, where lipids support neuronal structure, function, and synaptic plasticity. However, this essential metabolic pathway is highly susceptible to oxidative stress, which can lead to lipid peroxidation, a damaging process induced by reactive oxygen species. Lipid peroxidation generates by-products that disrupt many cellular functions, with a strong impact on proteostasis. In this review, we explore the role of lipid oxidation in protein folding and its associated pathological implications, with a particular focus on findings in neurodegeneration from Caenorhabditis elegans studies, an animal model that remains underutilized. Additionally, we highlight the effectiveness of different methodologies applied in this nematode to deepen our understanding of this intricate process. In the nervous system of any animal, including mammals and invertebrates, lipid oxidation can disturb the delicate balance of cellular homeostasis, leading to oxidative stress, the build-up of toxic by-products, and protein misfolding, key factors in neurodegenerative diseases. This disruption contributes to the pathogenesis of neurodegenerative disorders such as Alzheimer's, Parkinson's, or Huntington's disease. The findings from Caenorhabditis elegans studies offer valuable insights into these complex processes and highlight potential avenues for developing targeted therapies to mitigate neurodegenerative disease progression.

Reducing the Formation of Toxic Byproducts During the Photochemical Release of Epinephrine.

Engineered light-sensitive molecules offer a sophisticated toolkit for the manipulation of biological systems with both spatial and temporal precision. Notably, artificial "caged" compounds can activate specific receptors solely in response to light exposure. However, the uncaging process can lead to the formation of potentially harmful byproducts. For example, the photochemical release of adrenaline (epinephrine) is accompanied by the formation of adrenochrome, which has neuro- and cardiotoxic effects. To investigate this effect in detail, we synthesized and compared two "caged" epinephrine analogs. The first was a classical compound featuring an ortho-nitrobenzyl protecting group attached to the amino group of epinephrine. The second analog retained the ortho-nitrobenzyl group but included an additional carbamate linker. The photolysis of both compounds was conducted under identical conditions, and the resulting products were analyzed using UV-Vis spectroscopy, chromatography, and NMR techniques. Surprisingly, while the classical compound led to the formation of adrenochrome, the carbamate-type caged epinephrine did not produce this byproduct, resulting in the clean release of the active substance. Subsequently, we assessed the novel compound in an in vitro platelet activation assay. The results demonstrated that the uncaging of epinephrine significantly enhances platelet activation, making it a valuable tool for advanced signaling studies.

Structural analysis of ExaC, an NAD+-dependent aldehyde dehydrogenase, from Pseudomonas aeruginosa

The opportunistic pathogen Pseudomonas aeruginosa (Pa) utilizes ethanol as an energy source, however, ethanol metabolism generates acetaldehyde, a toxic byproduct. To mitigate this toxicity, P. aeruginosa employs aldehyde dehydrogenases (ALDHs) to oxidize acetaldehyde into less harmful compounds. ExaC, an NAD+-dependent ALDH from P. aeruginosa (PaExaC) and a member of group X ALDHs, plays a critical role in this detoxification by oxidizing both aldehydes and hydrazones. In this study, we determined the crystal structures of PaExaC in its apo and NAD+-bound forms. PaExaC functions as a homodimer, with three distinct domains: an NAD+ binding domain, a catalytic domain, and an oligomerization domain. Structural analyses revealed that PaExaC’s substrate entry channel (SEC) is optimized for size-selective aldehyde metabolism, with Leu120, Tyr462, and Thr302. Comparative structural and docking analyses with other ALDHs further validated PaExaC’s preference for small aliphatic aldehydes and hydrazones. These findings highlight PaExaC’s role in aldehyde detoxification, facilitating P. aeruginosa survival in diverse environments, and provide structural insights for developing targeted inhibitors to help treat infections.

LC-MS/MS based analytical strategies for the detection of lipid peroxidation products in biological matrices.

Oxidative stress (OS) arises mainly from exposure to reactive oxygen species (ROS) such as superoxide anion, hydroxyl radical, and hydrogen peroxide. These molecules can cause significant damage to proteins, DNA, and lipids, leading to various diseases. Cells fight ROS with detoxifying enzymes; however, an imbalance can cause damage leading to ischemic conditions, heart disease progression, and neurological disorders such as Alzheimer's disease. Accurate assessment of OS levels is then crucial and oxidized lipidic products are considered relevant OS biomarkers. In fact, lipids are particularly prone to ROS attack, leading to lipid peroxidation, cell membrane damage, and toxic by-products affecting DNA, proteins, and low-density lipoproteins. This review reports on recent advances in LC-MS/MS approaches for OS lipidic biomarkers, focusing on overcoming analytical challenges. 3 different classes of biomarkers have been reported, malondialdehyde, isoprostanes and oxidised sterols. For each class, the main analytical challenges with a particular focus on derivatisation procedure, sensitivity, matrix effect, ionisation have been described and discussed. The recent advancements of the LC-MS-MS procedures move towards simpler approaches, reducing errors and improving the reliability of the measurement thus enabling a comprehensive and robust OS assessment.

Water-Soluble Iron Porphyrins as Catalysts for Suppressing Chlorinated Disinfection Byproducts in Hypochlorite-Dependent Water Remediation.

We are facing a world-wide shortage of clean drinking water which will only be further exacerbated by climate change. The development of reliable and affordable methods for water remediation is thus of utmost importance. Chlorine (which forms active hypochlorites in solution) is the most commonly used disinfectant due to its reliability and low cost. One drawback is that it reacts with organic pollutants to generate toxic chlorinated byproducts. To mitigate chlorination in water remediation, we have investigated the use of catalytic amounts of charged water-soluble iron porphyrins. These are known to activate hypochlorite to generate high valent oxoiron species. We studied the depletion of the model micropollutant phenol and the accumulation of chlorinated disinfection byproducts under water remediation conditions, using iron porphyrins [(TMPyP)FeCl]Cl4 and (NH4)4[(TPPS)FeCl] as catalysts, by membrane inlet mass spectrometry. Despite bearing opposite charges on the meso-substituent, both iron porphyrins suppress the formation of chlorinated disinfection by-products equally well. To gain further insight, spectroscopic studies were performed. These showed the transient formation of Compound II, followed by either regeneration of the iron(III) porphyrin at low NaOCl concentrations, or total decomposition of the porphyrin complex at high NaOCl concentrations. Potential future directions for modifications of porphyrin-based catalysts are discussed.

Sub‐Nanometer Pt Nanowires with Disordered Shells for Highly Active Elelctrocatalytic Oxidation of Formic Acid

AbstractControlled synthesis of one‐dimensional materials at atomic‐scale dimensions represents a milestone in nanotechnology, offering the potential to maximize atom utilization while enhancing catalytic performance. However, achieving structural stability and durability at such fine scales requires precise control over material structure and local chemical environment. Here, we introduce dimethylamine (DMA) as a small‐molecule modifier, in contrast to conventional long‐chain surfactants, to interact with surface Pt atoms. This approach facilitates the removal of surface Pt atoms bonded to nitrogen atoms in DMA during solubilization in water, effectively stripping the size of Pt nanowires down to sub‐nanometer. The resulting Pt subnanometer nanowires (subNWs) feature a monoatomic‐layer surface composed of disordered, bonding‐unsaturated Pt atoms, and an interior crystalline core as narrow as 0.58 nm in diameter. These unique structural characteristics confer the Pt subNWs with an electrochemically active surface‐area of 189 m2 ⋅ g−1 during formic acid oxidation. Furthermore, the amorphous‐like surface structure lowers the free energy of *OCOH intermediates and inhibits the formation of toxic byproducts CO, demonstrating exceptional electrocatalytic activity of 18.1 A ⋅ mg−1, surpassing most reported Pt‐based electrocatalysts. Our work introduces a novel strategy for the controlled construction of nanowire‐structures at sub‐nanometer scale, effectively bridging the gap between ultrafine structural design and performance stability.

Green Silver Nanoparticles: An Antibacterial Mechanism.

Silver nanoparticles (AgNPs) are a promising tool in the fight against pathogenic microorganisms. "Green" nanoparticles are especially valuable due to their environmental friendliness and lower energy consumption during production, as well as their ability to minimize the number of toxic by-products. This review focuses on the features of AgNP synthesis using living organisms (bacteria, fungi, plants) and the involvement of various biological compounds in this process. The mechanism of antibacterial activity is also discussed in detail with special attention given to anti-biofilm and anti-quorum sensing activities. The toxicity of silver nanoparticles is considered in light of their further biomedical applications.

Selective oxidation of ammonium to dinitrogen by a novel catalytic ozonation system: Regulating the N2 selectivity by sulfite.

The selective oxidation of NH4+-N into dinitrogen (N2) is still a challenge. Currently, traditional advanced oxidation processes often involve in the chlorine free radicals to increase the selectivity of NH4+-N oxidation products towards N2 but is usually accompanied by the production of many toxic disinfection by-product. Herein, we reported a novel catalytic ozonation system (UV/O3/MgO/Na2SO3) for selective NH4+-N oxidation based on the reducing capability and photochemical properties of Na2SO3. In the UV/O3/MgO/Na2SO3/NH4+-N system, Na2SO3 could not only reduce the intermediate of NO2- or NO3- to N2 by inducing the generation of hydrated electrons under UV irradiation, but also reduce the gaseous intermediate of NOx to N2, thus achieving a high N2 selectivity (>85 %). Based on the analyses of each component roles, the determination of reactive oxygen species and the evolution of NH4+-N oxidation intermediates, the possible mechanisms of NH4+-N selective oxidation by UV/O3/MgO/Na2SO3 system were revealed. This system exhibits a great potential for the NH4+-N removal from water/wastewater. This work provides a new strategy for NH4+-N oxidation into N2 by advanced oxidation processes independent of the action of chlorine free radicals.

Enhanced Anticancer Efficacy of Alkaline Plasma-Activated Water through Augmented RONS Production.

Despite notable advances in anticancer drug development, their manufacture and use pose environmental and health risks due to toxic byproducts, drug residue contamination, and cytotoxicity to normal cells. Therefore, developing cost-effective anticancer treatments with fewer toxic side effects and higher selectivity is essential to the advancement of highly effective anticancer therapies. Plasma-activated water (PAW) offers a green alternative to conventional chemical treatments as it reverts to water within days. However, the limited duration and dose of reactive oxygen and nitrogen species (RONS) in acidified PAW restrict its clinical deployment and the full understanding of their mechanism. In this study, we propose alkaline PAW as an innovative enhancement of the RONS technology. The alkaline PAW generated markedly superior RONS, with about 10 times higher levels of NO2-, H2O2, and ONOO-/O2•- than acidic PAW. The possible RONS generation pathways in alkaline PAW are analyzed by scavengers. In conventional acidic PAW, 70% of the H2O2 concentration is contributed by •OH but only about 20% in alkaline PAW. ONOO- is mainly formed through the reaction of O2•- with NO in alkaline pH, while in acidic PAW, it mainly forms from NO2- and H2O2. The results unveiled the synergistic and formidable anticancer effects of alkaline PAW against cancer cells, typified by an increase in intracellular ROS/RNS levels. Furthermore, alkaline PAW injection also effectively prevented xenograft tumor growth in mice. We systematically investigated this high-dose anticancer solution without using noble gases, toxic reagents, or extra energy consumption and successfully demonstrated the possibility of alkaline PAW being an effective and environmentally friendly therapeutic technology. The activity is closely linked to the RONS dose, and the generation pathway provides much-needed insight into the fundamental aspects of PAW chemistry required for the optimization of the biochemical activity of PAW.

Sub-Nanometer Pt Nanowires with Disordered Shells for Highly Active Elelctrocatalytic Oxidation of Formic Acid.

Controlled synthesis of one-dimensional materials at atomic-scale dimensions represents a milestone in nanotechnology, offering the potential to maximize atom utilization while enhancing catalytic performance. However, achieving structural stability and durability at such fine scales requires precise control over material structure and local chemical environment. Here, we introduce dimethylamine (DMA) as a small-molecule modifier, in contrast to conventional long-chain surfactants, to interact with surface Pt atoms. This approach facilitates the removal of surface Pt atoms bonded to nitrogen atoms in DMA during solubilization in water, effectively stripping the size of Pt nanowires down to sub-nanometer. The resulting Pt subnanometer nanowires (subNWs) feature a monoatomic-layer surface composed of disordered, bonding-unsaturated Pt atoms, and an interior crystalline core as narrow as 0.58 nm in diameter. These unique structural characteristics confer the Pt subNWs with an electrochemically active surface-area of 189 m2 ⋅ g-1 during formic acid oxidation. Furthermore, the amorphous-like surface structure lowers the free energy of *OCOH intermediates and inhibits the formation of toxic byproducts CO, demonstrating exceptional electrocatalytic activity of 18.1 A ⋅ mg-1, surpassing most reported Pt-based electrocatalysts. Our work introduces a novel strategy for the controlled construction of nanowire-structures at sub-nanometer scale, effectively bridging the gap between ultrafine structural design and performance stability.

Increased Toxicity toward Mammalian Cells in the Periodate Oxidation Process of Wastewater: The Overlooked Formation of Noniodinated but Nitrogenous Byproducts.

Periodate (PI) shows promising potential as an oxidant for wastewater treatment; however, its impact on the toxicity of wastewater remains unknown. Here, we found that with 100 μM PI addition, the cytotoxicity of wastewater increased from 4.8 to 7.6 mg-Phenol/L to 9.5 to 12.8 mg-Phenol/L, and genotoxicity increased from 0.3 to 0.9 μg-4-NQO/L. Interestingly, hypoiodous acid (HOI) was not detected during the reaction, and there was no observed increase in the concentration of total organic iodine (TOI). CHON components in dissolved organic matter changed most obviously in PI oxidation, which might serve as primary precursors for toxic byproducts. Cytotoxicity of typical nitrogen-containing precursors of tryptophan, lysine, phenylalanine, and tyrosine after PI oxidation increased from not detected to 14.7, 2.4, 4.1, and 3.2 mg-Phenol/L, respectively. Here, four nonhalogenated aromatic nitrogenous byproducts (N-DBPs) of 3-hydroxyquinoline, 4-hydroxyquinoline, benzopyridine, and benzopyrrole were confirmed using standards, and four byproducts such as 2-formylbenzonitrile were tentatively proposed. The cytotoxicity of the four confirmed byproducts was comparable to those known N-DBPs such as nitrosamines, suggesting attention should be given to these nonhalogenated but nitrogenous byproducts. The four confirmed byproducts were detected in two PI-treated wastewater samples with concentrations of 0.8, 0.98, 0.52, and 0.0038, and 18.28, 1.50, 0.57, and 0.0074 μg/L, respectively, with contributions less than 1.5% to the overall cytotoxicity. Further investigations are warranted to elucidate the primary drivers of toxicity in PI-treated wastewater.

Haloacetonitriles Induce Structure-Related Cellular Toxicity Through Distinct Proteome Thiol Reaction Mechanisms.

Haloacetonitriles (HANs) are a class of toxic drinking water disinfection byproducts (DBPs). However, the toxicity mechanisms of HANs remain unclear. We herein investigated the structure-related in vitro toxicity of 6 representative HANs by utilizing complementary bioanalytical approaches. Dibromoacetonitrile (DBAN) displayed strong cytotoxicity and Nrf2 oxidative stress responses, followed by monohalogenated HANs (monoHANs) while other polyhalogenated HANs (polyHANs) exhibited little toxicity. Activity based protein profiling (ABPP) revealed that toxic HANs adduct to human proteome thiols, supporting thiol reactivity as the primary toxicity mechanism for HANs. By using glutathione (GSH) as a thiol surrogate, monoHANs reacted with GSH via SN2 while polyHANs reacted through ultrafast addition reactions. In contrast, DBAN generated an unexpected fully debrominated product and glutathione disulfide (GSSG). The unique reaction of DBAN with GSH was found to be mediated by radicals which was supported by electron paramagnetic resonance (EPR) spectroscopy and by radical trapping reagent reaction quenching. Shotgun proteomics further revealed that monoHANs and DBAN adducted to proteome thiols in live cells forming dehalogenated adducts. Multiple antioxidant proteins, SOD1, CSTB, and GAPDH, were adducted by toxic HANs at specific cysteine residues. This study highlights the structurally selective toxicity of HANs in human cells, which are attributed to their distinct reactions with proteome thiols.