Insights into the Synergistic Effect and Inhibition Mechanism of Composite Conditioner on Sulfur-Containing Gases during Sewage Sludge Pyrolysis.

Sewage sludge odorous gas release is a key barrier to resource utilization, and conditioners can mitigate the release of sulfur-containing gases. The gas release characteristics and sulfur compound distribution in pyrolysis products under both single and composite conditioning strategies of CaO, Fe2O3, and FeCl3 were investigated. This study focused on the inhibition mechanisms of these conditioners on sulfur-containing gas emissions and compared the theoretical and experimental sulfur content in the products to evaluate the potential synergistic effects of the composite conditioners. The findings indicated that at 650 °C, CaO, Fe2O3, and FeCl3 inhibited H2S release by 35.8%, 23.2%, and 9.1%, respectively. Notably, the composite of CaO with FeCl3 at temperatures ranging from 350 to 450 °C and the combination of Fe2O3 with FeCl3 at 650 °C were found to exert synergistic suppression on H2S emissions. The strongly alkaline CaO inhibited the metathesis reaction between HCl, a decomposition product of FeCl3, and the sulfur-containing compounds within the sewage sludge, thereby exerting a synergistic suppression on the emission of H2S. Conversely, at temperatures exceeding 550 °C, the formation of Ca-Fe compounds, such as FeCa2O4, appeared to diminish the sulfur-fixing capacity of the conditioners, resulting in increased H2S emissions. For instance, the combination of CaO and FeCl3 at 450 °C was found to synergistically reduce H2S emissions by 56.3%, while the combination of CaO and Fe2O3 at 650 °C synergistically enhances the release of H2S by 23.6%. The insights gained from this study are instrumental in optimizing the pyrolysis of sewage sludge, aiming to minimize its environmental footprint and enhance the efficiency of resource recovery.

Synergistic Catalytic Effects on Nitrogen Transformation during Biomass Pyrolysis: A Focus on Proline as a Model Compound.

To investigate the control mechanisms of NOx precursors and the synergistic effects of composite catalysts during proline pyrolysis, a systematic series of experiments was conducted utilizing composite catalysts with varying Fe-Ca ratios. Product distribution analysis was employed to elucidate the catalysts' mechanisms in reducing NOx precursor emissions. The synergistic interactions between Fe and Ca were quantitatively assessed through comparative theoretical and experimental release calculations. The results indicate that an increase in the Fe content in the catalyst led to a rise in amine concentrations from 0.9% to 2.95%, implying that Fe facilitates the generation of amine-N through ring-opening and substitution reactions. When the Fe to Ca ratio was balanced at 1:1, nitrogen predominantly participated in the formation of purines via cyclization and substitution reactions. Additionally, all composite catalysts exhibited a suppressive effect on the release of NOx precursors, attributed to their significant enhancement of solid product retention. Fe-Ca composite catalyst synergistically inhibits the release of gaseous nitrogen. Notably, the strongest synergistic effect was observed with a 1:3 Fe to Ca ratio, which reduced the release of NH3 by 38.7% and HCN by 53.6% during proline pyrolysis. This study offers valuable insights into the control of NOx precursors and the optimization of nitrogen-rich biomass pyrolysis processes.

Positional Isomers of Covalent Organic Frameworks for Indoor Humidity Regulation.

Humidity is one of the most important indicators affecting human health. Here, a pair of covalent organic frameworks (COFs) of positional isomers (p-COF and o-COF) for indoor humidity regulation is reported. Although p-COF and o-COF have the same sql topology and pore size, they exhibit different water adsorption behaviors due to the subtle differences in water adsorption sites. Particularly, o-COF exhibits a steep adsorption isotherm in the range of 45-65% RH with a hysteresis loop, which is perfectly suitable for indoor humidity regulation. In the laboratory experiment, when the humidity of the external environment is 20-75% RH, o-COF can control the humidity of the room in the range of 45-60% RH. o-COF has shown great potential as a dual humidification/dehumidification adsorbent for indoor humidity regulation.

A Comparative Pharmacokinetic Study by UHPLC-MS/MS of Main Active Compounds after Oral Administration of Zushima-Gancao Extract in Normal and Adjuvant-Induced Arthritis Rats.

A sensitive and rapid ultra high-performance liquid-chromatography tandem mass spectrometry (UHPLC-MS/MS) method has been applied to investigate the influence of rheumatoid arthritis (RA) on the pharmacokinetics of nine analytes (daphnetin, daphnoretin, 7-hydroxycoumarin, liquiritin, isoliquiritin, liquiritigenin, isoliquiritigenin, glycyrrhizin, and glycyrrhetinic acid), which are major active components in Zushima-Gancao extract. The analytes and internal standard (IS) were separated in a Hypersil Gold C18 column and detected on a triple-stage quadrupole mass spectrometer using the validated method. All analytes exhibited good linearities (R² > 0.98), and the lower limit of quantification (LLOQs) were sufficient for quantitative analysis. Intra- and inter-batch precision were all within 14.96% while the accuracy of nine analytes ranged from -17.99 to 14.48%, and these results were all within acceptance criteria. The extraction recoveries, matrix effects, and stabilities were all satisfactory. Main pharmacokinetic parameters of each compound were compared, and significant differences were found in parameters of daphnetin, daphnoretin, liquiritin, isoliquiritin, isoliquiritigenin, glycyrrhizin, and glycyrrhetinic acid, especially the last one, between the two groups. Therefore, adjuvant-induced arthritis has different effects on the pharmacokinetics of ingredients in Zushima-Gancao extract. The comparative pharmacokinetic study between normal and adjuvant-induced arthritis rats might provide more comprehensive information to guide the clinical usage of Zushima-Gancao extract for treating RA.

Genetic association between TAP1 and TAP2 polymorphisms and ankylosing spondylitis: a systematic review and meta-analysis.

OBJECTIVES: Ankylosing spondylitis (AS) is a chronic inflammatory joint disease. The transporter associated with antigen processing (TAP) has been identified to play an important role in immune response as well as the HLA-associated diseases. The aim of our meta-analysis was to investigate the contribution of TAP (TAP1 and TAP2) polymorphisms to the risk of AS. METHODS: Meta-analyses were performed between 2 polymorphisms in TAP1 (TAP1-333, -637) and 3 polymorphisms in TAP2 (TAP2-379, -565, and -665) and AS. RESULTS: The meta-analyses were involved with 6 studies with 415 cases and 659 controls. Significant association was found between TAP1-333Val, TAP1-637Gly, and TAP2-565Thr and AS compared with combined control group (TAP1-333Val: p = 0.009, OR = 1.40, 95% CI 1.09-1.80; TAP1-637Gly: p = 0.002, OR = 1.48, 95% CI 1.15-1.91; p = 0.03, OR = 1.38, 95% CI 1.04-1.84). Subgroup analysis shown that significant association was only found in AS when compared with HLA-B27-negative controls (TAP1-333Val: p = 0.004, OR = 1.53, 95% CI 1.14-2.06; TAP1-637Gly: p = 0.004, OR = 1.52, 95% CI 1.15-2.02; p = 0.02, OR = 1.56, 95% CI 1.09-2.24), but not in AS when compared with HLA-B27-positive controls (p > 0.05). Moreover, no significant associations were found between haplotypes in TAP1 and TAP2 in both the combined and the subgroup analyses (p > 0.05). CONCLUSIONS: TAP1-333Val, TAP1-637Gly, and TAP2-565Thr were likely to be associated with AS.

Regulation of membrane fixation and energy production/conversion for adaptation and recovery of ZnO nanoparticle impacted Nitrosomonas europaea.

The ZnO nanoparticle (NP) effects on typical ammonia-oxidizing bacteria, Nitrosomonas europaea in a chemostat bioreactor, and the cells' toxicity adaptation and recovery potentials were explored. Hardly any inhibition was observed when the NP concentration was high up to 10 mg/L. The cells exposed to 50 mg/L ZnO NPs displayed time-dependent impairment and recovery potentials in terms of cell density, membrane integrity, nitrite production rate, and ammonia monooxygenase activity. The 6-h NP stress impaired cells were nearly completely restored during a 12-h recovery incubation, while the longer exposure time would cause irretrievable cell damage. Microarray analysis further indicated the transcriptional adaptation of N. europaea to NP stress. The regulations of genes encoding for membrane permeability or osmoprotectant, membrane integrity preservation, and inorganic ion transport during NP exposure and cell recovery revealed the importance of membrane fixation and the associated metabolisms for cells' self-protection and the following recovery from NP stress. The oxidative phosphorylation, carbon assimilation, and tricarboxylic acid (TCA) cycling pathways involved in the cells' antitoxicity activities and would promote the energy production/conversion efficiency for cell recovery. The heavy metal resistance, histidine metabolism, toxin-antitoxin defense, glycolysis, and sulfate reduction pathways were also suggested to participate in the cell detoxication and recovery processes. All these findings provided valuable insights into the mechanisms of cell-mediated ZnO NP cytotoxicity and their potential impacts on wastewater nitrogen removal system.

Development of an optimized RPA-PfAgo detection system for MTHFR C677T polymorphism genotyping.

This study introduces an efficient RPA-PfAgo detection system for the MTHFR C677T polymorphism, proposing a potential strategy to simplify the genotyping process. By optimizing recombinase polymerase amplification (RPA) with Pyrococcus furiosus Argonaute (PfAgo) nucleases, we achieved DNA amplification at a constant temperature. The assay was fine-tuned through meticulous primer and guide DNA selection, with optimal conditions established at 2.0 µL of MgAc, a reaction temperature of 42 °C, and a 10-minute reaction time for RPA. Further optimization of the PfAgo cleavage assay revealed the ideal concentrations of MnCl2, guide DNA, molecular beacon probes, the PfAgo enzyme, and the RPA product to maximize sensitivity and specificity. Clinical validation of 20 samples showed 100% concordance with Sanger sequencing, confirming the method's precision. The RPA-PfAgo system is a promising tool for on-site genotyping, with broad applications in personalized medicine and disease prevention.

Development and application of a novel recombinase polymerase amplification-Pyrococcus furiosus argonaute system for rapid detection of goose parvovirus.

Rapid and accurate detection of goose parvovirus (GPV) is crucial for controlling outbreaks and mitigating their economic impact on the poultry industry. This study introduces recombinase polymerase amplification combined with the Pyrococcus furiosus argonaute (RPA-PfAgo) system, a novel diagnostic platform designed to address the limitations of traditional GPV detection methods. Capitalizing on the rapid DNA amplification of RPA and stringent nucleic acid cleavage by the PfAgo protein, the RPA-PfAgo system offers high specificity and sensitivity in detecting GPV. Our optimization efforts included primer and probe configurations, reaction parameters, and guided DNA selection, culminating in a detection threshold of 102 GPV DNA copies per microlitre. The specificity of the proposed method was rigorously validated against a spectrum of avian pathogens. Clinical application to lung tissues from GPV-infected geese yielded a detection concordance of 100%, surpassing that of qPCR and PCR in both rapidity and operational simplicity. The RPA-PfAgo system has emerged as a revolutionary diagnostic modality for managing this disease, as it is a promising rapid, economical, and onsite GPV detection method amenable to integration into broad-scale disease surveillance frameworks. Future explorations will extend the applicability of this method to diverse avian diseases and assess its field utility across various epidemiological landscapes.

A novel FCTF evaluation and prediction model for food efficacy based on association rule mining.

Introduction: Food-components-target-function (FCTF) is an evaluation and prediction model based on association rule mining (ARM) and network interaction analysis, which is an innovative exploration of interdisciplinary integration in the food field. Methods: Using the components as the basis, the targets and functions are comprehensively explored in various databases and platforms under the guidance of the ARM concept. The focused active components, key targets and preferred efficacy are then analyzed by different interaction calculations. The FCTF model is particularly suitable for preliminary studies of medicinal plants in remote and poor areas. Results: The FCTF model of the local medicinal food Laoxianghuang focuses on the efficacy of digestive system cancers and neurological diseases, with key targets ACE, PTGS2, CYP2C19 and corresponding active components citronellal, trans-nerolidol, linalool, geraniol, α-terpineol, cadinene and α-pinene. Discussion: Centuries of traditional experience point to the efficacy of Laoxianghuang in alleviating digestive disorders, and our established FCTF model of Laoxianghuang not only demonstrates this but also extends to its possible adjunctive efficacy in neurological diseases, which deserves later exploration. The FCTF model is based on the main line of components to target and efficacy and optimizes the research level from different dimensions and aspects of interaction analysis, hoping to make some contribution to the future development of the food discipline.

A novel fluorescence probe for the recognition of Cd2+ and its application.

A facile fluorescence probe BQBH was synthesized and investigated on its spectrum property. The result showed that the BQBH had high sensitivity and selectivity for Cd2+ with lowest detection determined as 0.14 µM by fluorescence response. The 1: 1 binding ratio between BQBH and Cd2+ was determined by Job's plot, and the binding details were further confirmed by 1H NMR titration, FT-IR spectrum and HRMS analysis. The applications including on test paper, smart phone and cell image were all also investigated.

Absorption and interaction of the main constituents from the traditional Chinese drug pair Shaoyao-Gancao via a Caco-2 cell monolayer model.

Shaoyao-Gancao (Paeoniae Radix Alba and Glycyrrhizae Radix et Rhizoma) is a traditional Chinese drug pair widely used in decoctions for relieving pains, especially abdominal pain. We aimed to determine the intestinal absorption and interaction of three active compounds (glycyrrhizic acid, liquiritin, and paeoniflorin) in this drug pair. We investigated the transport of these compounds across intestinal epithelial cells by using the Caco-2 cell monolayer in both the apical-to-basolateral (A-B) and B-A directions. All compounds could only travel through the Caco-2 cell monolayer at a low level when the cells were treated with single component solutions. In the presence of verapamil, an inhibitor of P-glycoprotein (P-gp), the absorptive permeability (P(AB)) of paeoniflorin and liquiritin increased significantly (p < 0.05) and efflux ratios decreased, while the absorption of glycyrrhizic acid did not change significantly, which indicated that paeoniflorin and liquiritin might be P-gp substrates. In addition, when liquiritin and glycyrrhizic acid in Gancao extract and paeoniflorin in Shaoyao extract were examined, P(AB) of paeoniflorin and liquiritin were significantly higher, while glycyrrhizic acid retained the same absorption level compared to the corresponding single component solutions, which suggested that some certain ingredients in the extracts can promote the absorption of paeoniflorin and liquiritin, but not that of glycyrrhizic acid. Furthermore, compared to the results of treatment with individual extracts, treatment of cells with a mixture of the two extracts considerably increased (p < 0.05) the absorption of glycyrrhizic acid and paeoniflorin and showed no change in the absorption of liquiritin, which implied that the transport of glycyrrhizic acid and paeoniflorin is increased by some ingredients from the complementary drug in the drug pair, while that of liquiritin remains unaffected.

[Discussion on a new model of holistic treatment for chronic critical illness patients by internal cross-disciplinary team in the department of intensive care unit: clinical data analysis of a case of acute exacerbation of chronic obstructive pulmonary disease].

OBJECTIVE: To explore the effect of setting up an internal-cross disciplinary team (ICDT) in the intensive care unit (ICU) on a new model of overall treatment for patients with chronic critical illness (CCI). METHODS: A 60-year-old male patient with acute exacerbation of chronic obstructive pulmonary disease (AECOPD) admitted to ICU in the Second Affiliated Hospital of Fujian Medical University was introduced. The role of ICDT composed of physicians, nurses, respiratory therapists, physiotherapists, clinical dietitians and patients' family members in ventilator withdrawal and super-early rehabilitation was analyzed in this case. RESULTS: The patient was diagnosed as AECOPD, type II aspiration penumonia respiratory failure, septic shock. The ICDT in ICU carried out early rehabilitation treatment for the patient on the basis of traditional infection control and supportive treatment. Under the care of the ICDT, peripheral blood white blood cell count (WBC), neutrophil count (NEU), procalcitonin (PCT), arterial partial pressure of carbon dioxide (PaCO2), maximum inspiratory pressure (MIP), maximum expiratory pressure (MEP), right excursion of diaphragm, sputum viscosity, tidal volume (VT) and respiratory rate (RR) were improved. Subsequently, the ventilator mode was gradually changed and the ventilator parameters were down-regulated. The ventilator was successfully weaned on the 10th day of treatment. After weaning, the patient's bedside pulmonary function indicators improved, and he was transferred out of ICU on the 15th day of treatment and discharged on the 20th day. The mental state of the patients was good and the quality of life was greatly improved in CCI outpatient follow-up. CONCLUSIONS: ICDT cooperation is very important for monitoring and treatment of CCI patients, which is beneficial to the super-early rehabilitation and prognosis improvement of critically ill patients.

A Highly Stable Ortho-Ketoenamine Covalent Organic Framework with Balanced Hydrophilic and Hydrophobic Sites for Atmospheric Water Harvesting.

Atmospheric moisture is a sustainable clean water source that can solve the shortage of fresh water in arid areas. Herein a 2D covalent organic framework (COF-ok) was reported as a promising porous sorbent for solar-driven atmospheric water harvesting. COF-ok with ortho-ketoenamine linkage was extremely stable in harsh environment, including in boiling water, strong acids and bases. Because of the balanced hydrophilic and hydrophobic sites in channels, COF-ok showed a high water uptake of 0.33 g g-1 at a low relative humidity of 34 % featuring a characteristic S-shaped water sorption isotherm with low regeneration temperature (∼45 °C) and excellent cyclic stability. A laboratory-scale water harvesting system could collect water of 161 g kg-1 under sunlight.

Broadband short-range surface plasmon structures for absorption enhancement in organic photovoltaics.

We theoretically demonstrate a polarization-independent nanopatterned ultra-thin metallic structure supporting short-range surface plasmon polariton (SRSPP) modes to improve the performance of organic solar cells. The physical mechanism and the mode distribution of the SRSPP excited in the cell device were analyzed, and reveal that the SRSPP-assisted broadband absorption enhancement peak could be tuned by tailoring the parameters of the nanopatterned metallic structure. Three-dimensional finite-difference time domain calculations show that this plasmonic structure can enhance the optical absorption of polymer-based photovoltaics by 39% to 112%, depending on the nature of the active layer (corresponding to an enhancement in short-circuit current density by 47% to 130%). These results are promising for the design of organic photovoltaics with enhanced performance.

Integration of a photonic crystal polarization beam splitter and waveguide bend.

In this work, we present the design of an integrated photonic-crystal polarization beam splitter (PC-PBS) and a low-loss photonic-crystal 60 degrees waveguide bend. Firstly, the modal properties of the PC-PBS and the mechanism of the low-loss waveguide bend are investigated by the two-dimensional finite-difference time-domain (FDTD) method, and then the integration of the two devices is studied. It shows that, although the individual devices perform well separately, the performance of the integrated circuit is poor due to the multi-mode property of the PC-PBS. By introducing deformed airhole structures, a single-mode PC-PBS is proposed, which significantly enhance the performance of the circuit with the extinction ratios remaining above 20 dB for both transverse-electric (TE) and transverse-magnetic (TM) polarizations. Both the specific result and the general idea of integration design are promising in the photonic crystal integrated circuits in the future.

Magnetic/Gold Core-Shell Hybrid Particles for Targeting and Imaging-Guided Photothermal Cancer Therapy.

The development of hybrid particles for tumor diagnosis and therapy has received considerable attention because they are capable of combining tumor diagnosis and treatment concurrently. So far hybrid particles for efficient and safe tumor theranostics are still very limited. Herein we have designed a new type of hybrid particles and evaluated its potential to be used in image-guided cancer diagnosis and therapy without the need of any toxic anticancer or contrast agents. The hybrid particles, consist of magnetic nanoparticles which are embedded in the poly(methyl methacrylate) (PMMA) cores and gold shells on chitosan (CTS) (γ-Fe2O3 @PMMA/CTS@Au). The hybrid particles were synthesized through initial formation of the core-shell structured γ-Fe2O3 @PMMA/CTS particles containing approximately 20% loading of magnetic nanoparticles. A gold layer was then built on top of the core-shell magnetic particles via a reduction of gold salt by amines from the chitosan assisted with the reducing agent NaBH4, followed by growing to complete gold shells in the presence of ascorbic acid (42.6% Au content). The properties of the composite particles including their chemical composition, morphology, particle size, size distribution, surface charge, magnetic responsiveness and photothermal ability were systematically characterized. The potential application of the γ-Fe2O3 @PMMA/CTS@Au hybrid particles in tumor diagnosis and therapy was assessed in vitro and in vivo using 4T1 tumor cells and 4T1 tumor-bearing mice through combining magnetic targeting, photoacoustic (PA)/computed tomography (CT) imaging and photothermal therapy. Results suggest that the γ-Fe2O3 @PMMA/CTS@Au particles can serve as a multifunctional tumor theranostic nanoplatform for magnetically targeted photothermal therapy. Breast cancer has been effectively eliminated without the use of any anticancer drugs or contrast agents. Therefore, this type of core-shell hybrid particles represents a new composite particle design for effective and safe tumor theranostics.

TLR4 rs41426344 increases susceptibility of rheumatoid arthritis (RA) and juvenile idiopathic arthritis (JIA) in a central south Chinese Han population.

BACKGROUND: The aim of the study was to determine whether polymorphisms in toll-like receptor 4 (TLR4) confer susceptibility to rheumatoid arthritis (RA) and juvenile idiopathic arthritis (JIA) in a central south Chinese Han population. METHODS: Genotyping for six well studied polymorphisms (rs4986790, rs4986791, rs10759932, rs41426344, rs11536889 and rs7873784) in TLR4 gene were conducted in 1074 unrelated patients with RA and 1692 healthy control subjects, as well as in 217 unrelated patients with JIA and 378 healthy control subjects using direct sequencing technique. Comparisons between cases and controls in alleles, genotypes and haplotypes were carried out using Fisher's exact test. RESULTS: Significant genetic associations were detected between the 3'UTR rs41426344C and RA (p < 0.001, p adj < 0.001, OR = 2.24) and JIA (p < 0.001, p adj < 0.001, OR = 2.05). In addition, rs4986790G was found to be significantly associated with the susceptibility for RA (p = 0.005, p adj = 0.03, OR = 3.43), but not for JIA (p = 0.06, p adj = 0.36, OR = 2.65). Furthermore, significant increasing in the distributions of haplotypes H4 and H10 in RA (H4: p = 0.001, OR = 1.13; H10: p = 0.001, OR = 1.15) and JIA (H4: p = 0.04, OR = 2.06; H10: p = 0.02, OR = 2.47) were also found. Moreover, the frequency of rs41426344C significantly increased in RF-positive and anti-CCP positive subjects both in RA (RF+: p <0.0001, OR = 2.33; anti-CCP+: p =0.008, OR = 2.79) and JIA (RF+: p =0.02, OR = 2.91; anti-CCP+: p = 0.02, OR = 2.78). CONCLUSIONS: Our study suggested that rs41426344 and rs4986790 of TLR4 might contribute to RA, and rs41426344 might contribute to JIA pathogenesis in central south Chinese Han population.

The Association between 5HT2A T102C and Behavioral and Psychological Symptoms of Dementia in Alzheimer's Disease: A Meta-Analysis.

The serotonin receptor gene (5-HT2A) has been reported to be a susceptible factor in behavioral and psychological symptoms of dementia (BPSD) in Alzheimer's disease (AD). However, previous results were conflicting. We aim to investigate the association of 5-HT2A T102C with BPSD in AD using a meta-analysis. Studies were collected using PubMed, Web of Science, the Cochrane Library databases, Chinese National Knowledge Infrastructure (CNKI), and Embase. Pooled odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess associations. Nine studies with 1899 AD patients with/without BPSD were included in this meta-analysis. The 102C and CC genotypes were associated with psychosis in AD (102C: p < 0.00001, OR [95% CI] = 3.19 [2.12-4.79]; CC: p < 0.00001, OR [95% CI] = 7.24 [3.60-14.59]). The TT genotype was significantly associated with hallucinations, aberrant motor behavior, and psychosis in AD (hallucinations: p = 0.001, OR [95% CI] = 0.52 [0.36-0.77]; aberrant motor behavior: p = 0.03, OR [95% CI] = 0.58 [0.35-0.95]; and psychosis: p = 0.002, OR [95% CI] = 0.34 [0.17-0.67]). No association was observed between T102C alleles or genotypes and delusions, agitation/aggression, depression, and apathy (p > 0.05). Thus, the 5HT2A T102C might be a susceptible factor for hallucinations, aberrant motor behavior, and psychosis in AD. The potential mechanism of this polymorphism in BPSD in AD requires further exploration.

Physiological and transcriptional responses of Nitrosomonas europaea to TiO2 and ZnO nanoparticles and their mixtures.

The short-term combined effects of two most extensively used nanoparticles (NPs) TiO2 NPs (n-TiO2) and ZnO NPs (n-ZnO) versus their individual cytotoxicities on a model ammonia-oxidizing bacterium, Nitrosomonas europaea, were investigated at both physiological and transcriptional levels. n-ZnO exerted more serious impairment effects on cell morphology, cell density, membrane integrity, and ammonia monooxygenase activity than n-TiO2. However, the co-existing n-TiO2 displayed a dose-dependent mitigation effect on n-ZnO cytotoxicity. Consistently, the n-TiO2 and n-ZnO mixture-impacted global transcriptional expression profile, obtained with the whole-genome microarray technique, was more comparable to the n-TiO2-impacted one than that impacted by n-ZnO. The expressions of numerous genes associated with heavy metal scavenging, DNA repair, and oxidative stress response were less up-regulated under the binary impacts of NP mixture than n-ZnO. Moreover, only n-ZnO alone stimulated the up-regulations of heavy metal resistance genes, which further implied the capacity of co-existing n-TiO2 to alleviate n-ZnO cytotoxicity. In addition, the damage of cell membrane structures and the suppression of cell membrane biogenesis-related gene expressions under the influence of either individual NPs or their combinations strongly suggested that the interruption of cell membranes and the associated metabolic activities would probably be one of NPs' critical cytotoxicity mechanisms.

Toxicity of binary mixtures of metal oxide nanoparticles to Nitrosomonas europaea.

Although the widely used metal oxide nanoparticles (NPs) titanium dioxide NPs (n-TiO2), cerium dioxide NPs (n-CeO2), and zinc oxide NPs (n-ZnO) have been well known for their potential cytotoxicities to environmental organisms, their combined effects have seldom been investigated. In this study, the short-term binary effect of n-CeO2 and n-TiO2 or n-ZnO on a model ammonia oxidizing bacterium, Nitrosomonas europaea were evaluated based on the examinations of cells' physiological, metabolic, and transcriptional responses. The addition of n-TiO2 mitigated the negative effect of more toxic n-CeO2 and the binary toxicity (antagonistic toxicity) of n-TiO2 and n-CeO2 was generally lower than the single NPs induced one. While the n-CeO2/n-ZnO mixture exerted higher cytotoxicity (synergistic cytotoxicity) than that from single NPs. The increased addition of the less toxic n-CeO2 exaggerated the binary toxicity of n-CeO2/n-ZnO mixture although the solubility of n-ZnO was not significantly affected, which excluded the contribution of the dissolved Zn ions to the enhancement of the combined cytotoxicity. The cell membrane disturbances and NP internalizations were detected for all the NP impacted cultures and the electrostatic interactions among the two distinct NPs and the cells were expected to play a key role in mediating their direct contacts and the eventual binary nanotoxicity to the cells.