Ubiquitous occurrence of 1,4-dioxane in drinking water of China and its ecological and human health risk

The occurrence and distribution of 1,4-dioxane was investigated in 280 source and finished drinking water samples from 31 Chinese cities, based on which its ecological and health risks were systematically evaluated. The findings demonstrated that 1,4-dioxane was detected in about 80.0 % samples with values ranging from n.d. to 7757 ng/L in source water and n.d. to 2918 ng/L in drinking water. 1,4-Dioxane showed limited removal efficiency using conventional coagulation-sedimentation-filtration processes (14 % ± 48 %), and a removal efficiency of 35 % ± 44 % using ozonation-biological activated carbon advanced treatment processes. Relatively higher concentrations, detection frequency and environmental risk were observed in Taihu Lake, Yellow River, Yangtze River, Zhujiang River, and Huaihe River mainly in the eastern and southern regions, where there are considerable industrial activities and comparatively high population densities. The widespread presence as by-products during manufacturing consumer products e.g., ethoxylated surfactants, suggested municipal wastewater discharges were the dominant source for the ubiquitous occurrence of 1,4-dioxane, while industrial activities, e.g. resin manufacturing, also contribute considerably to the elevated concentrations of 1,4-dioxane. The estimated risk quotients were in the range of <1.5 × 10-4 for ecological risk, <5.0 × 10-3 by oral exposure and < 5.0 × 10-2 by inhalation exposure for health risk, illustrating limited ecological harm to water environment or chronic toxicity to human health. For carcinogenic risk, 1,4-Dioxane presented a mean risk of 1.8 × 10-6 by oral exposure, which slightly surpassed the recommended acceptable levels of U.S. EPA (<10-6), and risk from inhalation exposure could be negligible. The pervasiveness in drinking water, low removal efficiencies during water treatment processes, and suspected health impacts, highlighted the necessity to set related water quality standards of 1,4-dioxane in order to improve water environment in China.

A natural butter glyceride as a plasticizer for improving thermal, mechanical, and biodegradable properties of poly(lactide acid)

Polylactic acid (PLA) is a biobased and biodegradable thermoplastic polyester with great potential to replace petroleum-based plastics. However, its poor toughness and slow biodegradation rate affect broad applications of PLA in many areas. In this study, a glycerol triester existing in natural butter, glycerol tributyrate, was creatively explored and compared with previously investigated triacetin and tributyl citrate, as potential plasticizers of PLA for achieving improved mechanical and biodegradation performances. The compatibilities of these agents with PLA were assessed quantitively via the Hansen solubility parameter (HSP) and measured by using different testing methods. The incorporation of these compounds with varied contents ranging from 1 to 30 % in PLA altered thermal, mechanical, and biodegradation properties consistently, and the relationship and impacts of chemical structures and properties of these agents were systematically investigated. The results demonstrated that glycerol tributyrate is a novel excellent plasticizer for PLA and the addition of this triester not only effectively reduced the glass transition, cold crystallization, and melting temperatures and Young's modulus, but also led to a significant improvement in the enzymatic degradation rate of the plasticized PLA. This study paves a way for the development of sustainable and eco-friendly food grade plasticized PLA products.

Occurrence of Rhodococcus sp. RR1 prmA and Rhodococcus jostii RHA1 prmA across microbial communities and their enumeration during 1,4-dioxane biodegradation

1,4-Dioxane, a likely human carcinogen, is a co-contaminant at many chlorinated solvent contaminated sites. Conventional treatment technologies, such as carbon sorption or air stripping, are largely ineffective, and so many researchers have explored bioremediation for site clean-up. An important step towards this involves examining the occurrence of the functional genes associated with 1,4-dioxane biodegradation. The current research explored potential biomarkers for 1,4-dioxane in three mixed microbial communities (wetland sediment, agricultural soil, impacted site sediment) using monooxygenase targeted amplicon sequencing, followed by quantitative PCR (qPCR). A BLAST analysis of the sequencing data detected only two of the genes previously associated with 1,4-dioxane metabolism or co-metabolism, namely propane monooxygenase (prmA) from Rhodococcus jostii RHA1 and Rhodococcus sp. RR1. To investigate this further, qPCR primers and probes were designed, and the assays were used to enumerate prmA gene copies in the three communities. Gene copies of Rhodococcus RR1 prmA were detected in all three, while gene copies of Rhodococcus jostii RHA1 prmA were detected in two of the three sample types (except impacted site sediment). Further, there was a statistically significant increase in RR1 prmA gene copies in the microcosms inoculated with impacted site sediment following 1,4-dioxane biodegradation compared to the control microcosms (no 1,4-dioxane) or to the initial copy numbers before incubation. Overall, the results indicate the importance of Rhodococcus associated prmA, compared to other 1,4-dioxane degrading associated biomarkers, in three different microbial communities. Also, the newly designed qPCR assays provide a platform for others to investigate 1,4-dioxane biodegradation potential in mixed communities and should be of particular interest to those considering bioremediation as a potential 1,4-dioxane remediation approach.

Fe-ZSM-5 zeolite catalyst for heterogeneous Fenton oxidation of 1,4-dioxane: effect of Si/Al ratios and contributions of reactive oxygen species

Heterogeneous Fenton oxidation using traditional catalysts with H2O2 for the degradation of 1,4-dioxane (1,4-DX) still presents challenge. In this study, we explored the potential of Fe-ZSM-5 zeolites (Fe-zeolite) with three Si/Al ratios (25, 100, 300) as heterogeneous Fenton catalysts for the removal of 1,4-DX from aqueous solution. Fe2O3 or ZSM-5 alone provided ineffective in degrading 1,4-DX when combined with H2O2. However, the efficient removal of 1,4-DX using H2O2 was observed when Fe2O3 was loaded on ZSM-5. Notably, the Brønsted acid sites of Fe-zeolite played a crucial role during the degradation of 1,4-DX. Fe-zeolites, in combination with H2O2, effectively removed 1,4-DX via a combination of adsorption and oxidation. Initially, Fe-zeolites demonstrated excellent affinity for 1,4-DX, achieving adsorption equilibrium rapidly in about 10 min, followed by effective catalytic oxidative degradation. Among the Fe-ZSM-5 catalysts, Fe-ZSM-5 (25) exhibited the highest catalytic activity and degraded 1,4-DX the fastest. We identified hydroxyl radicals (·OH) and singlet oxygen (1O2) as the primary reactive oxygen species (ROS) responsible for 1,4-DX degradation, with superoxide anions (HO2·/O2·-) mainly converting into 1O2 and ·OH. The degradation primarily occurred at the Fe-zeolite interface, with the degradation rate constants proportional to the amount of Brønsted acid sites on the Fe-zeolite. Fe-zeolites were effective over a wide working pH range, with alkaline pH conditions favoring 1,4-DX degradation. Overall, our study provides valuable insights into the selection of suitable catalysts for effective removal of 1,4-DX using a heterogeneous Fenton technology.

Experimental evidence for immiscibility of enantiomeric polymers: Phase separation of high-molecular-weight poly(ʟ-lactide)/poly(ᴅ-lactide) blends and its impact on hindering stereocomplex crystallization

Although polymers tend not to mix, it remains challenging to characterize the immiscibility of enantiomeric poly(ʟ-lactide) (PLLA) and poly(ᴅ-lactide) (PDLA), particularly with equivalent and high molecular weight (high MW), which frustratingly disfavors the exclusive stereocomplexation. By introducing a random copolymer (PLC) of ʟ-lactide and caprolactone to form binary blends with PLLA and PDLA, the phase behavior of high-MW PLLA/PDLA blends was investigated mainly by using differential scanning calorimetry (DSC) and atomic force microscopy (AFM). DSC results showed that PLLA/PLC blends exhibited a single glass transition temperature (Tg), which depended on the blending ratio and precisely corresponded with the theoretical values calculated from the Fox equation. In comparison, PDLA/PLC blends showed composition-dependent heat-capacity increment at two unchanged Tg values of pure PLC and PDLA. AFM observation revealed that PLC is completely miscible with PLLA at high MW but is immiscible with PDLA, logically suggesting immiscibility of high-MW PLLA and PDLA. Moreover, AFM results demonstrated that high-MW PLLA/PDLA blends exhibited spherical droplets in asymmetric blends and bicontinuous interpenetrating worm-like patterns in symmetric counterparts, showing distinct and well-defined interfaces, confirming the microphase separation. Additionally, different MWs fundamentally led to significant differences in miscibility, which consequently affected the crystallization behaviors of PLLA/PDLA blends. This work provides evidence for (im)miscibility and its crucial impact on the crystallization of PLLA/PDLA blends and has important implications for understanding the stereocomplexation of polymers.

Effect of stereo-complexation on crystallization behavior and barrier properties of poly-lactide

The unique stere-complex crystal formed by poly(ʟ-lactide)/poly(ᴅ-lactide) (PLLA/PDLA) has a significant impact on properties of poly-lactide materials and is considered an effective means to improve the barrier properties of poly-lactide (PLA). In this work, poly-lactide films with different aggregate structures were prepared and the relationship of aggregate structure and barrier properties were explored. The results show that the crystal structure including crystallinity and crystal forms can be controlled by adjusting the isothermal crystallization time and crystallization temperature during the molding process. PLLA/PDLA composite films contain both homochiral crystallites and stereo-complex crystallites, and there is a synergistic crystallization effect between the two of them, which provides the composite films with high crystallinity and excellent barrier properties. Compared to the PLLA with homochiral crystallites, the PLLA/PDLA composite film with only stereo-complex crystallites exhibits higher barrier properties. The linear correlation between the crystallinity and the barrier properties is weak due to the changes in crystallization behavior and then the structure of poly-lactide caused by stereo-complexation. The linear correlation between the crystallinity and the barrier properties of the blend film is strong in the low crystallinity but weak at high crystallinity. Compared to homochiral crystallites, stereo-complex crystallites exhibits lower crystallinity dependence. It has been proven that different crystal forms have different design ideas for preparing high-barrier films, but the stereo-complexation resulting from the intermolecular forces between PLLA and PDLA having complementary chemical structure, is an effective method for enhancing the barrier performances of poly-lactide sustainably.

In Vitro and In Vivo Degradation of Photo-Crosslinked Poly(Trimethylene Carbonate-co-ε-Caprolactone) Networks

Three-armed poly(trimethylene carbonate) (PTMC) and poly(trimethylene carbonate-co-Ɛ-caprolactone) (P(TMC-co-ε-CL)) macromers with molecular weights of approximately 30 kg mol-1 are synthesized by ring-opening polymerization and subsequent functionalization with methacrylic anhydride. Networks are then prepared by photo-crosslinking. To investigate the in vitro and in vivo degradation properties of these photo-crosslinked networks and assess the effect of ε-caprolactone content on the degradation properties, PTMC networks, and copolymer networks with two different TMC:ε-CL ratios are prepared. PTMC networks degraded slowly, via an enzymatic surface erosion process, both in vitro and in vivo. Networks prepared from P(TMC-co-ε-CL) macromers with a 74:26 ratio are found to degrade slowly as well, via a surface erosion process, albeit at a higher rate compared to PTMC networks. Increasing the ε-CL content to a ratio of 52:48, resulted in a faster degradation. These networks lost their mechanical properties much sooner than the other networks. Thus, PTMC and P(TMC-co-ε-CL) networks are interesting networks for tissue engineering purposes and the exact degradation properties can be tuned by varying the TMC:ε-CL ratio, providing researchers with a tool to obtain copolymer networks with the desired degradation rate depending on the intended application.

Fabrication and characterization of poly(lactic acid-trimethylene carbonate) based biodegradable composite films

Two biobased composite films have been prepared with poly (lactic acid-trimethylene carbonate), polylactic acid and Laponite by solvent evaporation method. The 1H NMR and FTIR spectrums illustrate that P (LA-TMC) polymer is successfully synthesized and designed composite films are produced. Morphometric analyses demonstrate that the roughnesses of the film's surface and cross-section are on the increase with higher PLA and Laponite content. Mechanical performances reveal that the rise in tensile strength and modulus while maintaining excellent elongation at break is mainly due to the increase in the content of polylactic acid and Laponite. By utilizing the nano effect of Laponite, the maximum tensile strength of the composite film reaches 34.59 MPa. Thermal property results illustrate that the Tg and initial decomposition temperature are on the growth with the increase of PLA content. However, it is not significant on the effect of Laponite on the initial decomposition temperature. The water vapor permeability measurements prove that the barrier property of P(LA-TMC)/PLA/Laponite composite film is on the ascent with the Laponite addition. Hydrolytic degradation tests indicate that PLA and Laponite play avital part in accelerating the degradation rate of composite films and alkaline media is superior acidic and neutral conditions.

Factors Influencing Discontinuation of Clazosentan Therapy in Elderly Patients with Aneurysmal Subarachnoid Hemorrhage: A Retrospective Study from a Japanese Single Center

BACKGROUND Clazosentan is an endothelin receptor antagonist approved in Japan for preventing cerebral vasospasm and vasospasm-associated cerebral ischemia and infarction. This study included elderly patients aged ≥75 years with aneurysmal subarachnoid hemorrhage (SAH) and aimed to evaluate the factors associated with discontinuing anti-vasospasm therapy with clazosentan. MATERIAL AND METHODS In this single-center retrospective observational study, we extracted diagnostic and therapeutic work-up data of consecutive 40 patients with SAH treated with clazosentan infusion (10 mg/h) as first-line anti-vasospasm therapy between May 2022 and August 2023. Patient data were compared between the discontinued and completed groups, and related factors for the discontinuation were further analyzed. RESULTS Clazosentan was discontinued in 22% (n=9) of patients due to intolerable dyspnea accompanied by hypoxemia at 5±3 days after therapy initiation, in which 44% (n=4) were elderly (≥75 years). Patients who discontinued clazosentan therapy showed significantly lower urine volumes compared with those who completed the therapy (P<0.05). Multivariate regression analysis revealed that day-to-day urine volume variance and older age were independent risk factors for drug cessation (P<0.05). The cut-off value for predicting clazosentan discontinuation was -0.7 mL/kg/h with sensitivity of 86% and specificity of 75% (area under the curve: 0.76±0.10; 95% confidence interval: 0.56-0.96; P=0.035). CONCLUSIONS Our results suggest that approximately 20% of SAH patients suffered from intolerable respiratory symptoms attributable to hypoxemia. We found that both reduced day-to-day urine volume variation and older age are independent risk factors for drug discontinuation.

Formation of bis-spiropyrrolidines from isatin, secondary amines, and alkylidene Meldrum's acids

A catalyst-free synthesis of stable bis-spiropyrrolidines from isatin, secondary amines, and alkylidene Meldrum's acids in MeCN in 75-95% yield is described. The antioxidant and antimicrobial properties of the synthesized compounds are investigated. For this purpose, the radical scavenging activities of four derivatives were studied by radical trapping of diphenylpicrylhydrazine and ferric reduction power experiments. Disk diffusion test on Gram-positive and Gram-negative bacteria was employed to investigate antibacterial activities of five derivatives.

Detection and elimination of trace d-lactic acid in lignocellulose biorefining chain: Generation, flow, and impact on chiral lactide synthesis

High chiral purity of lactic acid is a crucial indicator for the synthesis of chiral lactide as the primary intermediate chemical for ring-open polymerization of high molecular weight polylactic acid (PLA). Lignocellulose biomass is the most promising carbohydrate feedstock for commercial production of PLA, but the presence of trace d-lactic acid in the biorefinery chain adversely affects the synthesis and quality of chiral lactide. This study analyzed the fingerprint of trace  d-lactic acid in the biorefinery chain and found that the major source of  d-lactic acid comes from lignocellulose feedstock. The naturally occurring lactic acid bacteria and water-soluble carbohydrates in lignocellulose feedstock provide the necessary conditions for  d-lactic acid generation. Three strategies were proposed to eliminate the generation pathway of  d-lactic acid, including reduction of moisture content, conversion of water-soluble carbohydrates to furan aldehydes in pretreatment, and conversion to  l-lactic acid by inoculating engineered  l-lactic acid bacteria. The natural reduction of lactic acid content in lignocellulose feedstock during storage was observed due to the lactate oxidase-catalyzed oxidation of  l- and  d-lactic acids. This study provided an important support for the production of cellulosic  l-lactic acid with high chiral purity.

Meldrum's acid derivates are MepA efflux pump inhibitors: In vitro and in silico essays

Efflux pumps are proteins capable of expelling antibiotics from bacterial cells, have emerged as a major mechanism of bacterial resistance. In the ongoing pursuit to overcome and reduce bacterial resistance, novel substances are being explored as potential efflux pump inhibitors. Meldrum's acid, a synthetic molecule widely studied for its role in synthesizing bioactive compounds, holds promise in this regard. Therefore, the objective of this study is to evaluate the antibacterial activity of three derivatives of Meldrum's acid and assess their ability to inhibit efflux mechanisms, employing both in silico and in vitro approaches. The antibacterial activity of the derivatives was assessed using a broth microdilution testing method. Surprisingly, the derivatives did not exhibit direct antibacterial activity on their own. However, they displayed a significant effect in enhancing the efficacy of antibiotics, suggesting a potential role in potentiating their effects. Furthermore, fluorescence emission assays using ethidium bromide indicated that the derivatives could potentially block efflux pumps, as they exhibited fluorescence levels comparable to the positive control. To further investigate their inhibitory capacity, molecular docking studies were conducted in silico, revealing binding interactions similar to ciprofloxacin and carbonyl cyanide 3-chlorophenylhydrazone, known efflux pump inhibitors. These findings highlight the potential of Meldrum's acid derivatives as effective inhibitors of efflux pumps. By targeting these mechanisms, the derivatives offer a promising avenue to enhance the effectiveness of antibiotics and combat bacterial resistance. This study underscores the importance of exploring novel strategies in the fight against bacterial resistance and provides valuable insights into the potential of Meldrum's acid derivatives as efflux pump inhibitors. Further research and exploration in this field are warranted to fully exploit their therapeutic potential.

Application of portable liquid scintillation counter for on-field measurement of tritium in aqueous samples during radiation emergency

Screening of aqueous samples for 3H contamination is required to decide suitability of water intended for human consumption during radiation emergency. BARC, Trombay has recently procured Portable Triathler liquid scintillation counter as a screening tool for on-site response to radiation emergency. For this purpose, parameters like, different available scintillators, scintillator to sample ratio and influence of different capacity scintillation vials were optimized for 3H concentration measurement. The study indicated that for 7 mL vials, the optimized scintillator to sample ratio was 4:1 for Optiphase Hisafe II, Ultima Gold Ultra Low Level Tritium, Aqualight AB and Dioxane based scintillators whereas for Ultima Gold AB and Optiphase Hisafe III scintillators it was 3:1. In case of 20 mL vials, the ratio was optimized to 8:1 for all the above mentioned six scintillators. Additionally, the effect of applying counting efficiency using calibration curves generated using distilled water and that obtained using optimized scintillator to sample ratio in various spiked water samples was also studied. Results in 3H concentration (2000-5700 Bq/mL) indicate about ±10% deviation using both the methods for commercially available scintillators. However, in case of Dioxane based scintillator, the deviation was higher (20%). For analysis of 3H concentration ∼200 Bq/mL using commercially available scintillators results in higher deviation of about 21% due to unreliable quench indicating parameter for count rate less than 4000. The study indicated that calibration curves constructed using optimized parameters are universally applicable for determination of 3H concentration in wide variety of water samples.

Resorbable bilayer membrane made of L-lactide-ε-caprolactone in guided bone regeneration: an in vivo experimental study

PURPOSE

Guided bone regeneration (GBR) is an accepted method in dental practice that can successfully increase the bone volume of the host at sites chosen for implant placement; however, existing GBR membranes exhibit rapid absorption and lack of adequate space maintenance capabilities. We aimed to compare the effectiveness of a newly developed resorbable bilayer membrane composed of poly (L-lactic acid) and poly (-caprolactone) (PLACL) with that of a collagen membrane in a rat GBR model.

METHODS

The rat calvaria was used as an experimental model, in which a plastic cylinder was placed. We operated on 40 male Fisher rats and subsequently performed micro-computed tomography and histomorphometric analyses to assess bone regeneration.

RESULTS

Significant bone regeneration was observed, which was and similar across all the experimental groups. However, after 24 weeks, the PLACL membrane demonstrated significant resilience, and sporadic partial degradation. This extended preservation of the barrier effect has great potential to facilitate optimal bone regeneration.

CONCLUSIONS

The PLACL membrane is a promising alternative to GBR. By providing a durable barrier and supporting bone regeneration over an extended period, this resorbable bilayer membrane could address the limitations of the current membranes. Nevertheless, further studies and clinical trials are warranted to validate the efficacy and safety of The PLACL membrane in humans.

Injectable long-acting ivacaftor-loaded poly (lactide-co-glycolide) microparticle formulations for the treatment of cystic fibrosis: In vitro characterization and in vivo pharmacokinetics in mice

Optimizing a sustained-release drug delivery system for the treatment of cystic fibrosis (CF) is crucial for decreasing the dosing frequency and improving patients' compliance with the treatment regimen. In the current work, we developed an injectable poly(D,L-lactide-co-glycolide) (PLGA) microparticle formulation loaded with ivacaftor, a cystic fibrosis transmembrane conductance regulator (CFTR) potentiator that increases the open probability of the CFTR anion channel, using a single emulsion solvent evaporation technique. We aimed to study the effect of different parameters on the characteristics of the prepared formulations to select an optimized microparticle formulation to be used in an in vivo pharmacokinetic study in mice. First, a suite of ivacaftor-loaded microparticles were prepared using different formulation parameters in order to study the effect of varying these parameters on microparticle size, morphology, drug loading, encapsulation efficiency, and in vitro release profiles. Prepared microparticles were spherical with diameters ranging from 1.91-6.93 µm, percent drug loading (% DL) of 3.91-10.3%, percent encapsulation efficiencies (% EE) of 26.6-100%, and an overall slow cumulative release profile. We selected the formulation that demonstrated optimal combined % DL and % EE values (8.25 and 90.7%, respectively) for further studies. These microparticles had an average particle size of 6.83 µm and a slow tri-phasic in vitro release profile (up to 6 weeks). In vivo pharmacokinetic studies in mice showed that the subcutaneously injected microparticles resulted in steady plasma levels of ivacaftor over a period of 28 days, and a 6-fold increase in AUC 0 - t (71.6 µg/mL*h) compared to the intravenously injected soluble ivacaftor (12.3 µg/mL*h). Our results suggest that this novel ivacaftor-loaded microparticle formulation could potentially eliminate the need for the frequent daily administration of ivacaftor to people with CF thus improving their compliance and ensuring successful treatment outcomes.

Cardiopulmonary Events of the Elderly (≥75 Years) during Clazosentan Therapy after Subarachnoid Hemorrhage: A Retrospective Study from a Tertiary Stroke Center in Japan

Clazosentan has been shown to prevent vasospasm and reduce mortality in patients after aneurysmal subarachnoid hemorrhage (SAH) and has been approved for clinical use in Japan; however, its systemic events in the elderly (aged ≥ 75 years) have not been well-documented. Here, we report serious/intolerable cardiopulmonary complications requiring discontinuation of drug therapy in elderly SAH patients. In this single-center case series study, medical records of consecutive SAH patients treated postoperatively with clazosentan (10 mg/h) between June 2022 and May 2023 were reviewed retrospectively. Thirty-three patients received clazosentan therapy, of whom six were elderly with a mean age of 80.3 ± 5.2 (range 75-89) years. Among them, despite no obvious medical history of systemic abnormalities, clazosentan was discontinued in three (50%) patients due to pleural effusion and hypoxemia with or without hypotension at 5 ± 3 days after therapy initiation, which was higher than the incidence for younger patients (15%). The elderly patients had significantly lower urine output (1935 ± 265 vs. 1123 ± 371 mL/day, p = 0.03) and greater weight gain (2.1 ± 1.1 vs. 4.2 ± 1.9 kg from baseline, p = 0.04) than patients who completed the therapy. One 89-year-old female developed congestive heart failure and hydrostatic pulmonary edema associated with increased intravascular and lung volumes even after therapy was discontinued, while the remaining two cases recovered within 2 days after drug cessation. These results suggest that elderly patients are more vulnerable to fluid retention and have a higher risk of cardiopulmonary complications during clazosentan therapy than younger patients. Careful monitoring of urine volume and weight gain and caution regarding age- and therapy-related hemodynamic insufficiencies are required.

The role of reactive chlorine and nitrogen species in micropollutant degradation in UV/monochloramine

Monochloramine (NH2Cl) is applied upstream of reverse osmosis (RO) membranes for biofouling control. Residual NH2Cl can undergo UV photolysis downstream, generating reactive species for an AOP to occur. At the bench-scale, NH2Cl is typically generated from combining sodium hypochlorite and ammonium chloride or sulfate. This study investigated the degradation of four compounds of interest - acetaminophen, caffeine, sucralose and 1,4-dioxane - in UV/NH2Cl at the bench scale to study their reactivity with reactive chlorine species (RCS) and reactive nitrogen species (RNS). With methanol acting as a scavenger of •OH radicals, the performance of UV/NH2Cl was compared to UV/H2O2 and UV/HOCl. In UV/H2O2, dioxane was severely inhibited at 1-2 mg/L H2O2 and comparable at 5 mg/L to UV/NH2Cl. When ammonium sulfate ((NH4)2SO4) was used as the ammonia source over ammonium chloride (NH4Cl), the overall degradation of micropollutants was higher and caffeine was exclusively degraded. At 1-2 mg/L NH2Cl, dioxane degraded by 16.2-17.8% and 2.92-5.29% from (NH4)2SO4 and NH4Cl respectively while caffeine degraded by 7.45-9.61% with NH2Cl ((NH4)2SO4), but not degrade with NH2Cl (NH4Cl). The higher concentration of chloride ions from NH4Cl significantly influenced the speciation of generated radicals and impacted micropollutant degradation. This suggests that the reactivity of more selective RCS (Cl2•-, •ClO, ClOH•-) and RNS (•NH2, •NO, •NO2, etc.) varies with micropollutants of interest. The presence of higher chloride concentration from the ammonia source inhibited the generation of •OH radicals with •OH consumed by RNS to form NO3- (μg/L levels), showing the impact of the choice of ammonia source and the water matrix on UV/NH2Cl performance.

Synthesis of 1,4-benzodioxan derivatives and the evaluation of their biological activity as a novel juvenile hormone signaling inhibitor

BACKGROUND

Juvenile hormone (JH) signaling inhibitors may be used as insect growth regulators because of their ability to control metamorphosis and reproduction in insects by regulating the action of JH.

RESULTS

We identified ethyl (E)-3-(4-{[7- (4-methoxycarbonylbenzyloxy)-1,4-benzodioxan-6-yl]methyl}phenyl)prop-2-enoate (EMBP) and observed its strong precocious metamorphosis-inducing activity against silkworm larvae. To further elucidate its mechanism of action, we investigated the effect of EMBP on the JH-mediated signaling pathway in vitro and in vivo. In a reporter assay using a Bombyx mori cell line, EMBP strongly suppressed the induction of reporter gene expression by Juvenile hormone I (JH I) in a concentration-dependent manner. A parallel rightward shift was observed in the dose-response curve of JH I after treatment with EMBP, indicating that EMBP competitively inhibited JH. Moreover, we monitored developmental changes in the JH-responsive gene, Krüppel homolog 1 (Kr-h1), and ecdysone-responsive gene, Broad-Complex (BRC), in EMBP-treated silkworm larvae. EMBP suppressed only the expression of Kr-h1 in third-instar larvae.

CONCLUSION

Our results demonstrated that EMBP specifically regulates the JH-mediated Kr-h1 signaling pathway. EMBP could be used as a lead compound in the development of new insect growth regulators. © 2023 Society of Chemical Industry.

Postoperative stability of bioresorbable plates made of 85:15 poly (L-lactide-co-glycolide) in Le Fort I osteotomy

OBJECTIVE

Recently, RapidSorb plates (DePuy Synthes) made of 85.15 poly (L-lactide-co-glycolide) have been used for orthognathic surgery; however, reports regarding their effectiveness are limited. We aimed to compare the postoperative stability of RapidSorb plates, RapidSorb combined with titanium (MOJ plates), and MOJ plates in patients who underwent Le Fort I osteotomy at Tokyo Medical and Dental University Hospital.

STUDY DESIGN

The use of RapidSorb in the maxilla is a load-sharing application and therefore constitutes an approved indication. Discrepancies in the maxillary positions were measured using postoperative computed tomography data at 1 week and 1 year using the centroid method 3-dimensionally. Treatment with RapidSorb alone showed a more vertical discrepancy in the maxilla treatment with MOJ and RapidSorb+MOJ. The RapidSorb4 group was subdivided into 2 groups (under and over 1.0-mm) based on the change in the maxillary centroid.

RESULTS

The bone gap at the lateral border of the piriform aperture was significantly larger in the over-1.0-mm group than in the 1.0-mm group.

CONCLUSIONS

The fixation of RapidSorb alone is not appropriate in load-bearing and unstable applications but is not contraindicated for load-sharing indications. Fixation with RapidSorb combined with MOJ was clinically effective, with results similar to titanium plate-only fixation regarding postoperative stability.

Treatment of hazardous landfill leachate containing 1,4 dioxane by biochar-based photocatalysts in a solar photo-oxidation reactor

This study investigates a combined photocatalytic and adsorption system to maximize the removal of 1,4 dioxane from hazardous landfill leachate (HLL). The production of transformation products was also investigated to obtain a comprehensive evaluation of the treatment system. Copper/iron doped zinc oxide (Cu-Fe-ZnO) was introduced to biochar to form a hybrid materials and used to treat HLL contaminated with 1,4 dioxane of 355.0 ± 11.7 mg/L. The Cu-Fe-ZnO/biochar removed 93.1 ± 8.7% of 1,4 dioxane at a dose of 0.6 g/L within 90 min, as compared with only 42.7 ± 3.3% by 1.2 g/L of bare biochar within 210 min. The Cu-Fe-ZnO/biochar degraded 1,4 dioxane into ethylene glycol, glycolic acid, and formic acid. The 1,4 dioxane removal mechanisms were investigated using the density functional theory, demonstrating that doping of ZnO with metal atoms (Cu-Fe) narrowed the bandgap from 3.307 eV to 2.736 eV. The enhanced photocatalytic activity of ZnO was also supported by the role of biochar in increasing the reactive species and adsorbing the pollutant molecules. The high degradation efficiency of 1,4 dioxane using small catalyst doses with short reaction times would reduce the treatment cost and improve the system's applicability for treating HLL and industrial effluents.

Low-temperature persulfate activation by powdered activated carbon for simultaneous destruction of perfluorinated carboxylic acids and 1,4-dioxane

Carbonaceous materials have emerged as a method of persulfate activation for remediation. In this study, persulfate activation using powdered activated carbon (PAC) was demonstrated at temperatures relevant to groundwater (5-25 °C). At room temperature, increasing doses of PAC (1-20 g L^-1) led to increased persulfate activation (3.06 × 10^-6s^-1 to 2.10 × 10^-4 with 1 and 20 g L^-1 PAC). Activation slowed at lower temperatures (5 and 11 °C); however, substantial (>70 %) persulfate activation was achieved. PAC characterization showed that persulfate is activated at the surface of the PAC, as indicated by an increase in the PAC C:O ratio. Similarly, electron paramagnetic resonance (EPR) spectroscopy studies with a spin trapping agents (5,5-dimethyl-1-pyrroline N-oxide (DMPO)) and 2,2,6,6-tetramethylpiperidine (TEMP) revealed that singlet oxygen was not the main oxidizing species in the reaction. DMPO was oxidized to form 5,5-dimethylpyrrolidone-2(2)-oxyl-(1) (DMPOX), which forms in the presence of strong oxidizers, such as sulfate radicals. The persulfate/PAC system is demonstrated to simultaneously degrade both perfluorooctanoic acid (PFOA) and 1,4-dioxane at room temperature and 11 °C. With a 20 g L^-1 PAC and 75 mM persulfate, 80 % and 70 % of the PFOA and 1,4-dioxane, respectively, degraded within 6 h at room temperature. At 11 °C, the same PAC and persulfate doses led to 57% dioxane degradation and 54 % PFOA degradation within 6 h. Coupling PAC with persulfate offers an effective, low-cost treatment for simultaneous destruction of 1,4-dioxane and PFOA.

Electron beam treatment for the removal of 1,4-dioxane in water and wastewater

Electron beam (e-beam) treatment uses accelerated electrons to form oxidizing and reducing radicals when applied to water without the use of external chemicals. In this study, electron beam treatment was used to degrade 1,4-dioxane in several water matrices. Removal improved in the progressively cleaner water matrices and removals as high as 94% to 99% were observed at a dose of 2.3 kGy in secondary effluent. 1,4-dioxane removal was confirmed to be primarily through hydroxyl radical oxidation. The calculated electrical energy per order was found to be 0.53, 0.26, and 0.08 kWh/m³/order for secondary effluent (Avg. total organic carbon (TOC) 9.25 mg/L), granular activated carbon effluent (TOC 3.46 mg/L), and ultrapure water, respectively, with a 70% generation and transfer efficiency applied.

Efficient biodegradation of 1,4-dioxane commingled with additional organic compound: Role of interspecies interactions within consortia

Microbial consortia-mediated biodegradation of 1,4-dioxane (1,4-D), an emerging water contaminant, is always a superior choice over axenic cultures. Thus, better understanding of the functions of coexisting microbes and their interspecies interactions within the consortia is crucial for predicting biodegradation efficiency and designing efficient 1,4-D-degrading microbial consortia. This study evaluated how microbial community compositions and interspecies interactions govern the microbial consortia-mediated 1,4-D biodegradation by investigating the biodegradability and microbial community dynamics of both enriched (N112) and synthetic (SCDs and SCDNs) microbial consortia in the absence or presence of additional organic compound (AOC). In the absence of AOC, N112 exhibited 100% 1,4-D biodegradation efficiency at a rate of 12.5 mg/L/d, whereas the co-occurrence of AOC resulted in substrate-dependent biodegradation inhibition and thereby reduced the biodegradation efficiency and activity (2.0-10.0 mg/L/d). The coexistence and negative influence of certain low-abundant non-degraders on both 1,4-D-degraders and key non-degraders in N112 was identified as the prime cause behind such biodegradation inhibition. Comparing with N112, SCDN-1 composed of 1,4-D-degraders and key non-degraders significantly improved the 1,4-D biodegradation efficiency in the presence of AOC, confirming the absence of negative influence of low-abundant non-degraders and cooperative interactions between 1,4-D-degraders and key non-degraders in SCDN-1. On the contrary, both two-species and three-species SCDs comprised of only 1,4-D-degraders resulted in lower 1,4-D biodegradation efficiency as compared to SCDN-1 under all treatment conditions, while max. 91% 1,4-D biodegradation occurred by SCDs in the absence of AOC. These results were attributed to the negative interaction among 1,4-D-degraders and the absence of complementary roles of key non-degraders in SCDs. The findings improve our understanding of how interspecies interactions can regulate the intrinsic abilities and functions of coexisting microbes during biodegradation in complex environments and provide valuable guidelines for designing highly efficient and robust microbial consortia for practical bioremediation of 1,4-D like emerging organic contaminants.

Mechanisms of oxidative removal of 1,4-dioxane via free chlorine rapidly mixing into monochloramine: Implications on water treatment and reuse

Free chlorine (HOCl) and monochloramine (NH₂Cl) are two of the most commonly used water disinfectants in water treatment; however, the capability of rapid mixing of HOCl into NH₂Cl to induce oxidative reactions for efficient removal of contaminants remains largely unknown. In this study, 1,4-dioxane (1,4-D) removal was quantified during the rapid mixing of HOCl into NH₂Cl, to evaluate the effects of solution pH and HOCl-to-NH₂Cl ratio, and to identify mechanisms by which reactive species are generated in the system. Results showed that the highest 1,4-D removal was observed at the near-neutral pH of 6 with the HOCl-to-NH₂Cl molar ratio of 1. Hydroxyl radical (HO^•) contributed to 60-70 % of 1,4-D degradation and its generation was initiated by the hydrolytic decay of NH₂Cl and NHCl₂ upon HOCl addition to NH₂Cl with rapid mixing, and subsequent transformation of peroxynitrite (ONOO^-) and peroxynitrous acid (ONOOH). The results also confirmed that the presence of dissolved oxygen was required to form ONOO^-/ONOOH, and ONOO^- was a crucial precursor for reactive radical generation. These findings provide insight into the reaction mechanism associated with the system of rapidly mixed HOCl into NH₂Cl with the potential optimization and application for efficient trace organics removal in water treatment and reuse.

Valorisation of Lignocellulosic Wastes, the Case Study of Eucalypt Stumps Lignin as Bioadsorbent for the Removal of Cr(VI)

The main objective of this work was to assess Eucalyptus globulus lignin as an adsorbent and compare the results with kraft lignin, which has previously been demonstrated to be an effective adsorbent. Eucalypt lignin was extracted (by the dioxane technique), characterised, and its adsorption properties for Cr(VI) ions were evaluated. The monomeric composition of both types of lignin indicated a high content of guaiacyl (G) and syringyl (S) units but low content of p-hydroxyphenyl (H), with an H:G:S ratio of 1:50:146 (eucalypt lignin) and 1:16:26 (kraft lignin), as determined by Py-GC/MS. According to elemental analysis, sulphur (2%) and sodium (1%) were found in kraft lignin, but not in eucalypt lignin. The adsorption capacity of the eucalypt lignin was notably higher than the kraft lignin during the first 8 h, but practically all the ions had been absorbed by both the eucalypt and kraft lignin after 24 h (93.4% and 95%, respectively). Cr(VI) adsorption onto both lignins fitted well using the Langmuir adsorption isotherm model, with capacities of 256.4 and 303.0 mg/g, respectively, for eucalypt and kraft. The study’s overall results demonstrate the great potential of eucalypt lignin as a biosorbent for Cr(VI) removal from aqueous solutions.

Advocacy for the Medicinal Plant Artabotrys hexapetalus (Yingzhao) and Antimalarial Yingzhaosu Endoperoxides

The medicinal plant Artabotrys hexapetalus (synonyms: A.uncinatus and A. odoratissimus) is known as yingzhao in Chinese. Extracts of the plant have long been used in Asian folk medicine to treat various symptoms and diseases, including fevers, microbial infections, ulcers, hepatic disorders and other health problems. In particular, extracts from the roots and fruits of the plant are used for treating malaria. Numerous bioactive natural products have been isolated from the plant, mainly aporphine (artabonatines, artacinatine) and benzylisoquinoline (hexapetalines) alkaloids, terpenoids (artaboterpenoids), flavonoids (artabotrysides), butanolides (uncinine, artapetalins) and a small series of endoperoxides known as yingzhaosu A-to-D. These natural products confer antioxidant, anti-inflammatory and antiproliferative properties to the plant extracts. The lead compound yingzhaosu A displays marked activities against the malaria parasites Plasmodium falciparum and P. berghei. Total syntheses have been developed to access yingzhaosu compounds and analogues, such as the potent compound C14-epi-yingzhaosu A and simpler molecules with a dioxane unit. The mechanism of action of yingzhaosu A points to an iron(II)-induced degradation leading to the formation of two alkylating species, an unsaturated ketone and a cyclohexyl radical, which can then react with vital parasitic proteins. A bioreductive activation of yingzhaosu A endoperoxide can also occur with the heme iron complex. The mechanism of action of yingzhaosu endoperoxides is discussed, to promote further chemical and pharmacological studies of these neglected, but highly interesting bioactive compounds. Yingzhaosu A/C represent useful templates for designing novel antimalarial drugs.

Effective Ligand Design: Zinc Complexes with Guanidine Hydroquinoline Ligands for Fast Lactide Polymerization and Chemical Recycling

Invited for this month's cover is the group of Sonja Herres-Pawlis at RWTH Aachen University. The image shows how the zinc guanidine complexes help a circular economy of bioplastics by mediating the ring-opening polymerization of lactide and the depolymerization of polylactide (PLA). The Research Article itself is available at 10.1002/cssc.202201075.

Activation of ozone by peroxymonosulfate for selective degradation of 1,4-dioxane: Limited water matrices effects

The presence of 1,4-dioxane in various water streams poses a threat to the health of human beings. In this study, the oxidative combination of ozone with peroxymonosulfate (PMS) was for the first time used to remove 1,4-dioxane from water. Near complete abatement of 1,4-dioxane was achieved by ozone-PMS after reaction of only 15 min and the degradation kinetics was found to be positively correlated with doses of PMS and ozone. Ozone-PMS oxidation had the optimum performance at slight base pH values. Both sulfate radicals and hydroxyl radicals were generated in ozone-PMS oxidation and these radicals resulted in the degradation of 1,4-dioxane. The effects of common water constituents and real water matrices were investigated. It was found that bicarbonate ions with a concentration up to 10 mM had a slight promoting effect, while either chloride ions or natural organic matter inhibited only slightly the degradation. Meanwhile, no obvious difference in the degradation of 1,4-dioxane was found among the real water matrices and deionized water, which demonstrates that ozone-PMS oxidation has high tolerance and stability. The results from this study demonstrate that ozone-PMS may be a promising technology for the removal of 1,4-dioxane from various water matrices.

Preparation of healing promotive alanyl-glutamine-poly(p-dioxanone) electrospun membrane integrated with gentamycin and its application for intestinal anastomosis in rats

Anastomosis surgery at the intestinal site is performed on millions of individuals every year. However, several persistent complications, such as anastomotic leakage, abnormal adhesion, and anastomotic stenosis, have been observed after the surgery. For promoting anastomotic healing and to overcome the challenges mentioned above, re-epithelialization at anastomotic sites is crucial. In this study, an epithelialization-promoting macromolecular prodrug Ala-Gln-PPDO was prepared and processed into fibrous membranes by electrospinning. Ala-Gln and gentamicin were sustainably released from the electrospun membranes with degradation of these membranes to promote the proliferation of rat intestinal epithelial cells and suppress the proliferation of Staphylococcus aureus and Escherichia coli. The comprehensive repair effects of Ala-Gln-PPDO membranes have been evaluated in rat models of intestinal anastomosis in this study. Application of Ala-Gln-PPDO membranes, especially the gentamicin-incorporated Ala-Gln-PPDO ones, could prevent adhesion between the injured intestine and surrounding intestinal tissues. In addition, they did not affect the healing strength of anastomotic stoma negatively and could promote re-epithelialization at the anastomotic sites. Furthermore, the gentamicin-incorporated Ala-Gln-PPDO membranes could relieve stenosis at anastomotic sites. The gentamicin-incorporated Ala-Gln-PPDO electrospun membrane is a promising, comprehensive implantable material for promoting healing after gastrointestinal anastomosis owing to its effects involving the promotion of re-epithelialization, prevention of adhesion, and relieving of anastomotic stenosis.

The effect of blending poly (l-lactic acid) on in vivo performance of 3D-printed poly(l-lactide-co-caprolactone)/PLLA scaffolds

Blending poly (l-lactic acid, PLLA) with poly (l-lactide-co-caprolactone, PLCL) is an effective strategy for developing new PLCL/PLLA blend based biomaterials. However, the effect of PLLA on in vivo performance of PLCL/PLLA blends is unclear yet. To address this issue, in this study, the effect of PLLA on in vivo biodegradability and biocompatibility of 3D-printed scaffolds of PLCL/PLLA blend was investigated. Three kinds of different 3D-printed PLCL/PLLA scaffolds using different blends with different mass ratios of the polymers, were prepared and implanted subcutaneously. The shrinkage and tissue responses were monitored by ultrasonography after the implantation. 2 months post-operation, the in vivo performances of the scaffolds were investigated histologically. All scaffolds showed good biocompatibility and allowed fast tissues ingrowth, however PLCL50/PLLA50 scaffold with the highest PLLA ratio induced the thickest the fibrous capsule surrounding the scaffolds and highest inflammatory scores. Furthermore, it was found that the fine porous structures of all scaffolds were well maintained, indicating the 3D-printed scaffolds were degraded through a surface erosion but not bulk erosion way. However, different scaffolds showed different shrinkage and degradation ratios, and PLCL50/PLLA50 scaffold resulted in a significant shrinkage, while PLCL90/PLLA10 scaffold showed the better structural stability. Therefore, PLLA at blending different ratio had different effects on the in vivo performance of 3D-printed PLCL/PLLA scaffolds. Particularly, PLCL/PLLA scaffolds blending with low ratio of PLLA, such as PLCL90/PLLA10 scaffold showed better application potential in tissue engineering. Our findings provide a new insight on the rational design, constrcution and application of the 3D-printed PLCL/PLLA scaffolds.

Interface engineering strategy of a Ti4O7 ceramic membrane via graphene oxide nanoparticles toward efficient electrooxidation of 1,4-dioxane

Although Ti₄O₇ ceramic membrane has been recognized as one of the most promising anode materials for electrochemical advanced oxidation process (EAOP), it suffers from relatively low hydroxyl radical (^•OH) production rate and high charge-transfer resistance that restricted its oxidation performance of organic pollutants. Herein, we reported an effective interface engineering strategy to develop a Ti₄O₇ reactive electrochemical membrane (REM) doped by graphene oxide nanoparticles (GONs), GONs@Ti₄O₇ REM, via strong GONs-O-Ti bonds. Results showed that 1% (wt%) GON doping on Ti₄O₇ REM significantly reduced the charge-transfer resistance from 73.87 to 8.42 Ω compared with the pristine Ti₄O₇ REM, and yielded ^•OH at 2.5-2.8 times higher rate. The 1,4-dioxane (1,4-D) oxidation rate in batch experiments by 1%GONs@Ti₄O₇ REM was 1.49×10^-2 min^-1, 2 times higher than that of the pristine Ti₄O₇ REM (7.51×10^-3 min^-1) and similar to that of BDD (1.79×10^-2 min^-1). The 1%GONs@Ti₄O₇ REM exhibited high stability after a polarization test of 90 h at 80 mA/cm², and within 15 consecutive cycles, its oxidation performance was stable (95.1-99.2%) with about 1% of GONs lost on the REM. In addition, REM process can efficiently degrade refractory organic matters in the groundwater and landfill leachate, the total organic carbon was removed by 54.5% with a single-pass REM. A normalized electric energy consumption per log removal of 1,4-D (EE/O) was observed at only 0.2-0.6 kWh/m³. Our results suggested that chemical-bonded interface engineering strategy using GONs can facilitate the EAOP performance of Ti₄O₇ ceramic membrane with outstanding reactivity and stability.

In vivo effects of 1,4-dioxane on genotoxic parameters and behavioral alterations in Drosophila melanogaster

1,4-Dioxane (DXN) is used as solvent in different consumer products including cosmetics, paints, surfactants, and waxes. In addition, DXN is released as an unwanted contaminating by-product as a result of some reactions including ethoxylation of alcohols, which occurs with in personal care products. Consequently, DXN pollution was detected in drinking water and is considered as an environmental problem. At present, the genotoxicity effects attributed to DXN are controversial. The present study using an in vivo model organism Drosophila melanogaster aimed to determine the toxic/genotoxic, mutagenic/recombinogenic, oxidative damage as evidenced by ROS production, phenotypic alterations as well as behavioral and developmental alterations that are closely related to neuronal functions. Data demonstrated that nontoxic DXN concentration (0.1, 0.25, 0.5, or 1%) induced mutagenic (1%) and recombinogenic (0.1, 0.25, or 0.5%) effects in wing spot test and genotoxicity in hemocytes using comet assay. The nontoxic concentrations of DXN (0.1, 0.25, 0.5, or 1%) significantly increased oxidative stress, climbing behavior, thermal sensivity and abnormal phenotypic alterations. Our findings show that in contrast to in vitro exposure, DXN using an in vivo model Drosophila melanogaster this compound exerts toxic and genotoxic effects. Data suggest that additional studies using other in vivo models are thus warranted.

Co-occurrence of odor-causing dioxanes and dioxolanes with bis(2-chloro-1-methylethyl) ether in Huangpu River source water and fates in O3-BAC process

In recent years, dioxanes and dioxolanes have been intermittently detected in water environment and have caused several offensive drinking water odor incidents worldwide. In this study, the co-occurrence of eight dioxanes, twelve dioxolanes and bis(2-chloro-1-methylethyl) ether was investigated in Huangpu River watershed to explore potential sources and contributions to septic/chemical odor. Totally 8 dioxanes and dioxolanes were detected in river, with 1,4-dioxane (212 -8310 ng/L) and 2,5,5-trimethyl-1,3-dioxane (n.d.-133 ng/L) as the dominated dioxanes, 2-methyl-1,3-dioxolane (49.5 -2278 ng/L), 2-ethy-4-methyl-1,3-dioxolane (n.d.-167 ng/L) and 1,3-dioxolane (n.d.-225 ng/L) as the major dioxolanes. Bis(2-chloro-1-methylethyl) ether was detected (n.d.-1094 ng/L) with significant correlation with dioxanes and dioxolanes, illustrating their similar polyester resin-related industrial origins. 2-Ethy-4-methyl-1,3-dioxolane, 2,5,5-trimethyl-1,3-dioxane and bis(2-chloro-1-methylethyl) ether with individual maximum odor activity value above 1, should contribute to septic/chemical odor in Huangpu River water. The increased concentrations of these chemicals in the downstream of some industrial areas illustrated the association with industrial discharge. Fates in a waterworks using the river water as source water were further explored. The adopting ozone-biological activated carbon treatment could permit a relatively high removal for bis(2-chloro-1-methylethyl) ether and 2,5,5-trimethyl-1,3-dioxane (> 80%), while limited removal for other chemicals. This study provides valuable information for the management of drinking source water and water environment.

Clazosentan: First Approval

Clazosentan (PIVLAZ^™) is a small molecule, endothelin (ET) A receptor-selective antagonist being developed by Idorsia Pharmaceuticals. ET_A receptor inhibition by clazosentan decreases ET-related cerebral vasospasm, which may occur after an aneurysmal subarachnoid haemorrhage. Clazosentan has been approved in Japan for use in the prevention of cerebral vasospasm, vasospasm-related cerebral infarction and cerebral ischaemic symptoms after aneurysmal subarachnoid haemorrhage, following the results from the JapicCTI163369 and JapicCTI163368 phase III trials. This article summarises the milestones in the development of clazosentan leading to this first approval in this indication.

Oxidative degradation of commingled trichloroethylene and 1,4-dioxane by hydroxyl radicals produced upon oxygenation of a reduced clay mineral

Improper disposal of chlorinated solvents such as trichloroethylene (TCE) and its stabilizer 1,4-dioxane has resulted in extensive contamination in soils and groundwater. Oxidative degradation of these contaminants by strong oxidants has been proposed recently as a remediation strategy, but specific mechanisms and degradation efficiencies are still poorly understood, especially in commingled systems. In this study, a reduced iron-bearing clay (RIC), nontronite (rNAu-2), was oxygenated to produce hydroxyl radicals (•OH) for degradation of TCE and 1,4-dioxane under circumneutral and dark conditions. Results showed that TCE and 1,4-dioxane could be effectively degraded during oxygenation of rNAu-2 in both single and commingled systems. Compared with the single compound system, the degradation rates and efficiencies of TCE and 1,4-dioxane decreased in the commingled system. The negative effect was more significant for TCE than 1,4-dioxane. The commingled TCE and 1,4-dioxane impacted the degradation pattern of each other, due to their difference in •OH scavenging efficiency, surface affinity to rNAu-2 and solubility. Moreover, solution pH, buffer type, rNAu-2 dosage, and dissolved organic matter all affected •OH production and contaminant degradation efficiency. Our findings provide new insights for investigating the natural attenuation of commingled chlorinated solvents and 1,4-dioxane by RIC in redox-fluctuating environments and offer guidance for developing possible in-situ remediation strategies.

Degradation of 1,4-dioxane by biochar activating peroxymonosulfate under continuous flow conditions

1,4-Dioxane degradation under both batch-scale and column experiments has been investigated within the biochar activated peroxymonosulfate (PMS) system for in-situ remediation of 1,4-dioxane contaminated groundwater. In case of the batch experiments, the 1,4-dioxane degradation efficiencies were significantly increased with the increased biochar pyrolysis temperatures. The optimized 1,4-dioxane degradation efficiency at 89.2% was achieved with 1.0 g L^-1 of biochar (E800) and 8.0 mM PMS. In the absence of PMS, the breakthrough rates of 1,4-dioxane in biochar packed column experiments under the dynamic flow conditions were relatively slow compared with those in sand packed columns. Simultaneously, based on the integrated areas (IA) from the 1,4-dioxane breakthrough curves, the degradation efficiency at 70.2% was estimated in biochar packed column (W_E800:W_Sand = 1:9) under continuous injections of 16.0 mM PMS. Electron paramagnetic resonance (EPR) indicated that hydroxyl, sulfate and superoxide radicals were generated within the biochar/PMS systems and alcohol quenching experiments suggested that the dominated hydroxyl and sulfate radicals were responsible for 1,4-dioxane degradation. The findings of this study suggested that the biochar activated PMS system is a promising and cost-effective strategy for the remediation of 1,4-dioxane contaminated groundwater.

Establishing the prevalence and relative rates of 1,4-dioxane biodegradation in groundwater to improve remedy evaluations

Options for remediating 1,4-dioxane at groundwater sites are limited due to the physical-chemical properties of this compound. The relevance of natural attenuation processes for 1,4-dioxane was investigated through data from field, lab, and modeling efforts. The objectives were to use multiple lines of evidence for 1,4-dioxane biodegradation to understand the prevalence of this activity and evaluate convergence between lines of evidence. A ¹⁴C-1,4-dioxane assay confirmed 1,4-dioxane biodegradation at 9 of 10 sites (median rate constant of 0.0105 yr^-1 across wells). Site-wide rate constants were established using a calibrated fate and transport model at 8 sites (median = 0.075 yr^-1). The ¹⁴C assay constants are likely more conservative, and variability in rates suggested that biodegradation at sites may be localized. Stable isotope fractionation was observed at 7 of 10 sites and served as another direct line of evidence of in situ biodegradation of 1,4-dioxane. This includes sites where indirect lines of evidence, including geochemical conditions or genetic biomarkers for degradation, would not necessarily have been supportive. This highlights the importance of collecting multiple lines of evidence to document 1,4-dioxane natural attenuation, and the widespread prevalence of biodegradation suggests that this process should be part of long-term management decisions.

Evaluation of natural attenuation of 1,4-dioxane in groundwater using a 14C assay

Monitored Natural Attenuation (MNA) is a preferred remedy for sites contaminated with 1,4-dioxane due to its low cost and limited environmental impacts compared to active remediation. Having a robust estimate of the rate at which biodegradation occurs is an essential component of assessing MNA. In this study, an assay was developed using ¹⁴C-labeled 1,4-dioxane to measure rate constants for biodegradation based on accumulation of ¹⁴C products. Purification of the ¹⁴C-1,4-dioxane stock solution lowered the level of ¹⁴C impurities to below 1% of the total ¹⁴C activity. This enabled determination of rate constants in groundwater as low as 0.0021 yr^-1, equating to a half-life greater than 300 years. Of the 54 groundwater samples collected from 10 sites in the US, statistically significant rate constants were determined with the ¹⁴C assay for 24. The median rate constant was 0.0138 yr^-1 (half-life = 50 yr); the maximum rate constant was 0.367 yr^-1 (half-life = 1.9 yr). The results confirmed that biodegradation of 1,4-dioxane is occurring at 9 of the 10 sites sampled, albeit with considerable variability in the level of activity. The specificity of the assay was confirmed using acetylene and the absence of oxygen to inhibit monooxygenases.

Oxidative stress and genotoxicity in 1,4-dioxane liver toxicity as evidenced in a mouse model of glutathione deficiency

1,4-Dioxane (DX) is a synthetic chemical used as a stabilizer for industrial solvents. Recent occurrence data show widespread and significant contamination of drinking water with DX in the US. DX is classified by the International Agency for Research on Cancer as a group 2B carcinogen with the primary target organ being the liver in animal studies. Despite the exposure and cancer risk, US EPA has not established a drinking water Maximum Contaminant Level (MCL) for DX and a wide range of drinking water targets have been established across the US and by Health Canada. The DX carcinogenic mechanism remains unknown; this information gap contributes to the varied approaches to its regulation. Our recent mice study indicated alterations in oxidative stress response accompanying DNA damage as an early change by high dose DX (5000 ppm) in drinking water. Herein, we report a follow-up study, in which we used glutathione (GSH)-deficient glutamate-cysteine ligase modifier subunit (Gclm)-null mice to investigate the role of redox homeostasis in DX-induced liver cytotoxicity and genotoxicity. Gclm-null and wild-type mice were exposed to DX for one week (1000 mg/kg/day by oral gavage) or three months (5000 ppm in drinking water). Subchronic exposure of high dose DX caused mild liver cytotoxicity. DX induced assorted molecular changes in the liver including: (i) a compensatory nuclear factor erythroid 2-related factor 2 (NRF2) anti-oxidative response at the early stage (one week), (ii) progressive CYP2E1 induction, (iii) development of oxidative stress, as evidenced by persistent NRF2 induction, oxidation of GSH pool, and accumulation of the lipid peroxidation by-product 4-hydroxynonenal, and (iv) elevations in oxidative DNA damage and DNA repair response. These DX-elicited changes were exaggerated in GSH-deficient mice. Collectively, the current study provides additional evidence linking redox dysregulation to DX liver genotoxicity, implying oxidative stress as a candidate mechanism of DX liver carcinogenicity.

Peroxone activated persulfate oxidation of 1,4-Dioxane under column scale conditions

The research presented herein investigates a peroxone activated persulfate (PAP) oxidant, commercialized under the trade name OxyZone®, and its effects on 1,4-Dioxane (dioxane) contaminated water under column scale conditions in the presence of porous material. There is a limited understanding of the underlying processes that govern PAP oxidation, including the oxidation rates in the presence of aquifer material, and how these reactions proceed once the oxidant is injected into a contaminant plume. Initial batch experiments with porous material (e.g. sand) provided data on the reaction rates of dioxane oxidation as a function of the oxidant: contaminant ratio. The observed degradation rates were approximately 4 times lower than those reported for aqueous solutions containing no porous media. Subsequent column experiments simulated two PAP injections schemes along the flowpath of a dioxane plume to study if the injection of one oxidant slug may yield different results than injecting the same oxidant volume at two separate locations. The injection of one oxidant slug was found more effective, resulting in near complete destruction of dioxane over a prolonged time at a rate more than an order of magnitude greater than in the two-slug injection scenario. Tracer test results suggest that the prolonged oxidant reactivity was in part caused by the high density of the injected oxidant solution. Overall, the results underline the importance of accounting for the properties of both the oxidant solution and the porous material when considering the injection of PAP oxidant into an impacted aquifer.

The industrial solvent 1,4-dioxane causes hyperalgesia by targeting capsaicin receptor TRPV1

BACKGROUND

The synthetic chemical 1,4-dioxane is used as industrial solvent, food, and care product additive. 1,4-Dioxane has been noted to influence the nervous system in long-term animal experiments and in humans, but the molecular mechanisms underlying its effects on animals were not previously known.

RESULTS

Here, we report that 1,4-dioxane potentiates the capsaicin-sensitive transient receptor potential (TRP) channel TRPV1, thereby causing hyperalgesia in mouse model. This effect was abolished by CRISPR/Cas9-mediated genetic deletion of TRPV1 in sensory neurons, but enhanced under inflammatory conditions. 1,4-Dioxane lowered the temperature threshold for TRPV1 thermal activation and potentiated the channel sensitivity to agonistic stimuli. 1,3-dioxane and tetrahydrofuran which are structurally related to 1,4-dioxane also potentiated TRPV1 activation. The residue M572 in the S4-S5 linker region of TRPV1 was found to be crucial for direct activation of the channel by 1,4-dioxane and its analogs. A single residue mutation M572V abrogated the 1,4-dioxane-evoked currents while largely preserving the capsaicin responses. Our results further demonstrate that this residue exerts a gating effect through hydrophobic interactions and support the existence of discrete domains for multimodal gating of TRPV1 channel.

CONCLUSIONS

Our results suggest TRPV1 is a co-receptor for 1,4-dioxane and that this accounts for its ability to dysregulate body nociceptive sensation.

Potential of UV-B and UV-C irradiation in disinfecting microorganisms and removing N-nitrosodimethylamine and 1,4-dioxane for potable water reuse: A review

The ultraviolet (UV)-based advanced oxidation process (AOP) is a powerful technology for removing pathogenic microorganisms and contaminants of emerging concern (CECs) from water. AOP in potable water reuse has been predominantly based on traditional low-pressure mercury (LP-Hg) lamps at 254 nm wavelength, supplemented by hydrogen peroxide addition. In this review, we assessed the potential of unconventional UV wavelengths (UV-B, 280-315 nm and UV-C, 100-280 nm) compared to conventional one (254 nm) in achieving the attenuation of pathogens and CECs. At the same UV doses, conventional 254 nm LP-Hg lamps and other sources such as, 222 nm KrCl lamps and 265 nm UV-LEDs, showed similar disinfection capability for viruses, protozoa, and bacteria, and the effect of hydrogen peroxide (H₂O₂) addition on disinfection remained unclear. The attenuation levels of key CECs in potable water reuse (N-nitrosodimethylamine and 1,4-dioxane) by 185 + 254 nm LP-Hg or 222 nm KrCl lamps were generally greater than those by conventional 254 nm LP-Hg and other UV lamps. CEC degradation was generally enhanced by H₂O₂ addition. Overall, our review suggests that 222 nm KrCl or 185 + 254 nm LP-Hg lamps with the addition of H₂O₂ would be the best alternative to conventional 254 nm LP-Hg lamps for achieving target removal levels of both pathogens and CECs in potable water reuse.

Discovery of zeylenone from Uvaria grandiflora as a potential botanical fungicide

BACKGROUND

Botanical pesticides play an important role in organic agricultural practices and are widely used in integrated pest management (IPM). Uvaria grandiflora was mainly reported as traditional medicines and possessed antibacterial, antioxidant, and antiprotozoal activities. Therefore, important biological activities of U. grandiflora may suggest that they have the potential to be used as botanical pesticides.

RESULTS

The extract of U. grandiflora exhibited broad-spectrum inhibitory activity toward phytopathogenic fungi and oomycetes, particularly against Colletotrichum musae and Phytophthora capsici, and its secondary metabolite zeylenone also displayed strong antifungal and anti-oomycete activities against phytopathogens. Particularly, half maximal effective concentration (EC₅₀ ) values of zeylenone against Phytophthora capsici and C. musae were 6.98 and 3.37 μg mL^-1 , showing better inhibitory effects than those of commercial fungicides (azoxystrobin and osthole). Additionally, the pot experiments showed that the extract of U. grandiflora could effectively control Pseudoperonospora cubensis, Phytophthora infestans, Phytophthora capsici and Podosphaera xanthii. In the field experiment, 5% microemulsion of U. grandiflora extract exhibited 79.72% efficacy against cucumber powdery mildew at 87.5 g ha^-1 on the 14th day after two sprayings, which was better than that of 21.5% trifloxystrobin and 21.5% fluopyram SC at 200.9 g ha^-1 . Surprisingly, 5% microemulsion of U. grandiflora extract could promote cucumber growth significantly. Furthermore, the action mechanism analysis indicated that zeylenone may damage the cytoderm and affect energy metabolism of Phytophthora capsici.

CONCLUSION

It is the first time that the extract of U. grandiflora and zeylenone have been discovered leading to broad application prospects in the development as botanical fungicides. © 2021 Society of Chemical Industry.

A rotational study of the 1:1 adduct of ethanol and 1,4-dioxane

The pure rotational spectra of the 1:1 ethanol - 1,4-dioxane complex and its OD mono-deuterated species have been measured using pulsed-jet Fourier transform microwave spectroscopy. Conformational predictions for the plausible isomers of ethanol - 1,4-dioxane have been carried out considering the spatial orientation of gauche/trans ethanol with respect to the chair/boat and twisted conformations of 1,4-dioxane. Using Helium for the supersonic expansion, the microwave spectrum has been observed for the most stable structure. In the observed isomer, the two subunits are linked together by an OH⋯O hydrogen bond with gauche ethanol acting as proton donor to dioxane in the chair conformation. The non-covalent interactions have been characterized using different computational approaches. A small inverse Ubbelohde effect was observed after H → D isotopic substitution in the OH⋯O hydrogen bond.

Identification of the phylotypes involved in cis-dichloroethene and 1,4-dioxane biodegradation in soil microcosms

Co-contamination with chlorinated compounds and 1,4-dioxane has been reported at many sites. Recently, there has been an increased interest in bioremediation because of the potential to degrade multiple contaminants concurrently. Towards improving bioremediation efficacy, the current study examined laboratory microcosms (inoculated separately with two soils) to determine the phylotypes and functional genes associated with the biodegradation of two common co-contaminants (cis-dichloroethene [cDCE] and 1,4-dioxane). The impact of amending microcosms with lactate on cDCE and 1,4-dioxane biodegradation was also investigated. The presence of either lactate or cDCE did not impact 1,4-dioxane biodegradation one of the two soils. Lactate appeared to improve the initiation of the biological removal of cDCE in microcosms inoculated with either soil. Stable isotope probing (SIP) was then used to determine which phylotypes were actively involved in carbon uptake from cDCE and 1,4-dioxane in both soil communities. The most enriched phylotypes for ¹³C assimilation from 1,4-dioxane included Rhodopseudomonas and Rhodanobacter. Propane monooxygenase was predicted (by PICRUSt2) to be dominant in the 1,4-dioxane amended microbial communities and propane monooxygenase gene abundance values correlated with other enriched (but less abundant) phylotypes for ¹³C-1,4-dioxane assimilation. The dominant enriched phylotypes for ¹³C assimilation from cDCE included Bacteriovorax, Pseudomonas and Sphingomonas. In the cDCE amended soil microcosms, PICRUSt2 predicted the presence of DNA encoding glutathione S-transferase (a known cDCE upregulated enzyme). Overall, the work demonstrated concurrent removal of cDCE and 1,4-dioxane by indigenous soil microbial communities and the enhancement of cDCE removal by lactate. The data generated on the phylotypes responsible for carbon uptake (as determined by SIP) could be incorporated into diagnostic molecular methods for site characterization. The results suggest concurrent biodegradation of cDCE and 1,4-dioxane should be considered for chlorinated solvent site remediation.

The Effects of Septorhinoplasty Techniques and Poly-P-Dioxanone Plate Use on Maxillofacial Growth: An Experimental Study

ABSTRACT

Since the septum plays a key role in maxillofacial growth, the effect of septorhinoplasty maneuvers and the use of poly-p-dioxanone plate during growth on maxillofacial growth was investigated in our study. Thirty-three New Zealand rabbits each with an age of 8 weeks were included in the study. Maxillofacial computed tomography was performed on all 8-weeks old rabbits. Then, the rabbits were divided into 5 groups randomly. No intervention was done on the rabbits in group 1. Nasal dorsum of the rabbits in the 2nd group were opened, and the mucosae were bilaterally elevated. In the third group underwent limited cartilage resection by preserving the nasal dorsum. Removed cartilage was crushed and placed back between the mucoperichondrial flaps for the rabbits in the 4th group. Crushed cartilage with Poly-P-Dioxanone plate was used for the rabbits in the 5th Group. Maxillofacial computed tomography was performed at the end of the 20th week and growth parameters were investigated. When the group 2 was compared with the control group, the nasal bone length was observed to be significantly shorter (P < 0.05). Group 5 compared with group 4, incisive bone volume remained significantly low (P < 0.05) and malocclusion developed. Nasal bone length was affected negatively in the group that underwent osteotomy and mucosa elevation. Although positive results related to poly-p-dioxanone plate use have been reported for adults, incisive bone development retarded in noses that had not yet reached adult size in our study and the maxillofacial development was affected adversely.

Severe Complications Following Maxillary Sinus Augmentation Using Poly L-lactide-co-ε-caprolactone-Coated Bovine Bone: A Retrospective Study

PURPOSE

To describe the postoperative complications following lateral wall sinus augmentation using (poly L-lactideco-ε-caprolactone; PLCL) and natural polysaccharides polymers-coated bovine bone (PBB). The secondary aims were to examine histologic findings and to propose complication management alternatives.

MATERIALS AND METHODS

This retrospective study included 61 subjects who underwent 67 lateral wall sinus augmentation procedures using PBB in the standard protocol. In cases that presented complications, treatment included additional antibiotic therapy, implant removal, or sinus reentry and total removal of the grafting material. In three cases, biopsy specimens were taken from the sinuses, and histologic analyses were performed.

RESULTS

The prevalence of postoperative complications was 32.8% (22 of 67 cases) in 18 of the patients (29.5%). The most prevalent symptoms were persistent pain (68.2%), swelling (63.6%), and oroantral fistula (54.5%). Radiographic signs appeared in 45.5% of the complications. A total of 24 implants failed; thus, an overall 80.3% survival rate was established at 19 months. The vast majority of complications (86.4%) were treated eventually with reentry surgery and revealed that the sinus was full with granulation tissue surrounding pieces of a nonossified rubber-like material. In cases where implants were placed, nonosseointegrated implants were surrounded by soft tissue. The sinus was cleaned thoroughly; the graft material remnants were removed together with inflamed parts of the sinus membrane, followed by chlorhexidine and saline lavages. In the biopsy specimens taken from the sinus cavity, there were no histologic features of new bone formation around the grafted material.

CONCLUSION

Lateral wall maxillary sinus augmentation using PBB was associated with an acute sinus infection histologic appearance and with a 7-times-higher failure rate compared with previous reports. This serious adverse event suggests that PBB cannot be recommended for maxillary sinus augmentations.

Evaluation of the in vitro cytotoxicity and modulation of the inflammatory response by the bioresorbable polymers poly(D,L-lactide-co-glycolide) and poly(L-lactide-co-glycolide)

Bioresorbable polymers composed of poly(D,L-lactide-co-glycolide) (PDLLGA) and poly(L-lactide-co-glycolide) (PLLGA) have become increasingly popular for the preparation of bone substitute constructs. However, there are reports of a delayed inflammatory reaction occurring months or years after implantation. Due to the long polymer degradation times, in vitro tests carried out at physiological temperature, 37°C, tend to assess only the short-term biocompatibility of these materials. The aim of this work is to develop an in vitro protocol that can be used to assess the long-term cytotoxicity of bioresorbable polymers in a time efficient manner. This study used a previously developed and validated accelerated degradation protocol to obtain samples of PDLLGA and PLLGA at increasing levels of degradation. Samples were then applied to standard ISO 10993-5 direct contact cytotoxicity testing and it was found that PDLLGA samples showed increasing levels of cytotoxicity at the later stages of degradation, with PLLGA samples demonstrating significantly less cytotoxic behaviour. Following concern that accumulation of acidic degradation products in a closed multi-well culture environment could overestimate cytotoxicity, we developed and validated a new dynamic flow culture methodology, for testing the cytotoxicity of these degradable materials, by adapting a commercial "organ on a chip" flow culture system, Quasi Vivo®. In addition to cytotoxicity testing, we have carried out profiling of inflammatory cytokines released by cells in response to degraded PDLLGA and PLLGA, and have suggested mechanism by which lactide-based bioresorbable materials could modulate the inflammatory response through the G-protein coupled receptor (GPCR), hydroxycarboxylic acid receptor 1 (HCA₁). STATEMENT OF SIGNIFICANCE: Bioresorbable materials naturally disintegrate over time when implanted into the body. They are often used to make screws and clips for repair of broken bones. Unfortunately, some patients can react badly to the material, resulting in painful inflammation. Biomaterials scientists are interested in developing materials that are more compatible with the body. However, it is very difficult to predict the long-term compatibility of bioresorbable materials in the lab. In our study, we have developed a method that will allow us to study the effects of the materials as they continue to break down. This will help us understand why the materials may cause inflammation, and will support research into the development of new and improved materials for bone repair.

Genotoxic effects and molecular docking of 1,4-dioxane: combined protective effects of trans-resveratrol

In this study, the protective effects of trans-resveratrol (t-resv) against 1,4-dioxane-induced toxicity in meristematic cells were investigated. For this purpose, Allium test was used and the alterations in all experimental groups were examined by using physiological, cytogenetic, biochemical, and anatomical parameters. In order to elucidate the toxicity mechanism, interactions of 1,4-dioxane and intracellular antioxidant molecules were investigated by molecular docking. As a result of the analysis, it was determined that 1,4-dioxane causes serious abnormalities in Allium cepa meristematic cells. In 1,4-dioxane-treated group, germination percentage was regressed 1.6 times, root length was reduced 12.7 times, and weight gain was decreased 7.7 times compared to control group. T-resv administration with 1,4-dioxane resulted in an improvement in physiological parameters and reduced the relative injury rate from 0.4 to 0.16. Mitotic index (MI), micronucleus (MN), and chromosomal abnormality (CAs) frequencies were investigated as cytogenetic parameters. 1,4-Dioxane decreased MI index, and increased CAs and MN frequency. In addition, it was determined by the comet test that 1,4-dioxane caused deterioration in DNA integrity. T-resv treatment was found to cause a dose-dependent improvement in genotoxic effects. Changes in the antioxidant system in all experimental groups were determined by measuring malondialdehyde (MDA) and glutathione (GSH) levels, superoxide dismutase (SOD), and catalase (CAT) enzyme activities. 1,4-Dioxane caused alterations in all tested parameters, causing deterioration in the oxidant/antioxidant balance in the cell. A 200-mg/L t-resv+1,4-dioxane treatment caused a 1.9-fold decrease in MDA level which is indicator of lipid peroxidation compared to only 1,4-dioxane-treated group. The mechanism of the disruption in antioxidant/oxidant dynamics and genetic integrity was elucidated by molecular docking analysis of 1,4-dioxane with antioxidant molecules and DNA. In 1,4-dioxane treatment group, anatomical changes such as cell deformation, flattened cell nucleus, and thickening of cortex cell wall were observed. The frequency of these changes decreased with t-resv administration. As a result, it was determined that 1,4-dioxane caused a versatile toxicity in A. cepa meristematic cells, while t-resv was found to have a dose-dependent protective feature against 1,4-dioxane-induced toxicity.

Degradation of N-nitrosamines and 1,4-dioxane using vacuum ultraviolet irradiation (UV254+185 nm or UV172 nm)

Advanced oxidation processes (AOPs) play a vital role in attenuating contaminants of emerging concern (CECs) during potable water reuse. AOPs are conventionally performed by irradiating with a 254-nm low-pressure (LP) mercury-vapor (Hg) ultraviolet (UV) lamp along with chemical treatment. Compared with UV-C light treatment (200-280 nm), vacuum-UV (V-UV) light treatment (100-200 nm) is advantageous in terms of hydroxyl radical generation without the requirement for chemical treatment. This study assessed the potential of V-UV (172-nm Xe₂ excimer or 185 + 254-nm LP-Hg) lamps on the destruction of two major CECs in potable water reuse, namely N-nitrosodimethylamine (NDMA) and 1,4-dioxane. Direct irradiation using UV_{254 nm} or UV_{185+254 nm} lamps achieved ≥94% removal of N-nitrosamines, including NDMA, at a UV dose of 900 mJ/cm². In contrast, the Xe₂ excimer lamp (UV_{172 nm}) was less effective for N-nitrosamine removal, achieving up to 82% removal of NDMA. The removal of 1,4-dioxane by V-UV lamps at a UV dose of 900 mJ/cm² reached 51% (UV_{172 nm}) and 28% (UV_{185+254 nm}), both of which results were superior to that obtained using a conventional UV_{254 nm} lamp (10%). The addition of hydrogen peroxide during UV_{254 nm} or UV_{185+254 nm} irradiation was found to enhance the removal of 1,4-dioxane, while UV_{172 nm} irradiation without hydrogen peroxide addition still exhibited greater efficiencies than those UV_{254 nm} lamps-based AOPs. Overall, this study demonstrated that the removal of both NDMA and 1,4-dioxane can be successfully achieved using either a UV_{254+185 nm} lamp with hydrogen peroxide or a UV_{172 nm} Xe₂ excimer lamp without hydrogen peroxide.