Microfluidic Mechanoporation: Current Progress and Applications in Stem Cells.

Intracellular delivery, the process of transporting substances into cells, is crucial for various applications, such as drug delivery, gene therapy, cell imaging, and regenerative medicine. Among the different approaches of intracellular delivery, mechanoporation stands out by utilizing mechanical forces to create temporary pores on cell membranes, enabling the entry of substances into cells. This method is promising due to its minimal contamination and is especially vital for stem cells intended for clinical therapy. In this review, we explore various mechanoporation technologies, including microinjection, micro-nano needle arrays, cell squeezing through physical confinement, and cell squeezing using hydrodynamic forces. Additionally, we highlight recent research efforts utilizing mechanoporation for stem cell studies. Furthermore, we discuss the integration of mechanoporation techniques into microfluidic platforms for high-throughput intracellular delivery with enhanced transfection efficiency. This advancement holds potential in addressing the challenge of low transfection efficiency, benefiting both basic research and clinical applications of stem cells. Ultimately, the combination of microfluidics and mechanoporation presents new opportunities for creating comprehensive systems for stem cell processing.

Three-dimensional DNA nanomachine biosensor coupled with CRISPR Cas12a cascade amplification for ultrasensitive detection of carcinoembryonic antigen.

The detection of carcinoembryonic antigen (CEA) holds significant importance in the early diagnosis of cancer. However, current methods are hindered by limited accessibility and specificity. This study proposes a rapid and convenient Cas12a-based assay for the direct detection of CEA in clinical serum samples, aiming to address these limitations. The protocol involves a rolling machine operation, followed by a 5-min Cas12a-mediated cleavage process. The assay demonstrates the capability to detect human serum with high anti-interference performance and a detection limit as low as 0.2 ng/mL. The entire testing procedure can be accomplished in 75 min without centrifugation steps, and successfully reduced the limit of detection of traditional DNA walking machine by 50 folds. Overall, the testing procedure can be easily implemented in clinical settings.

A Smartphone-Enabled Colorimetric Platform Based on Enzyme Cascade Amplification Strategy for Detection of Staphylococcus aureus in Milk.

Staphylococcus aureus (S. aureus) is a pathogenic bacterium-contaminating milk and dairy foods causing food poisoning and foodborne pathogens. In this work, a smartphone-enabled enzyme cascade-triggered colorimetric platform was constructed using cascade bio-nanozyme formed by immobilized glucose oxidase (GOx) on the Fe3O4@Ag for rapid detection of S. aureus. Benefiting from reasonable experimental design, a bio-nanozyme cascade-triggered reaction was achieved through H2O2 produced by GOx oxidation of glucose, followed by in situ catalysis of 3,3',5,5'-tetramethylbenzidine (TMB) by the inherent peroxidase-like activity of Fe3O4@Ag to produce color signals. S. aureus detection could be performed through naked-eye observation and smartphone measurement, the developed assay can achieve quantitative and qualitative detection of S. aureus. The on-site nanoplatform had satisfactory specificity and sensitivity with a low detection limit of 6.9 cfu·mL-1 in 50 min. Moreover, the nanoplatform has good practicality in the detection of S. aureus in milk samples. Therefore, the assay has potential application prospects in food safety inspection.

Colorimetry/fluorescence dual-mode detection of Salmonella typhimurium based on self-assembly of MCOF with Au NPs nanozyme coupled AIEgen.

Sensitive, accurate, simple and quick monitoring of Salmonella typhimurium (S. typhimurium) in food is significant for preventing food poisoning, but still remains a challenge. Herein, a colorimetry/fluorescence dual-mode sensing strategy was fabricated to detect S. typhimurium by integrating the self-assembly of magnetic covalent organic framework (MCOF) with gold nanoparticles (Au NPs) as the peroxidase-mimicking nanozyme and aggregation-induced emission luminogen (AIEgen). S. typhimurium could competitive bind to aptamer conjugated Au NPs (Au NPs@apt), inhibit the self-assembly of MCOF with Au NPs, and shield the catalytic activity of AuNPs. After adding H2O2 and TPE-4A, the dark green solution changed to light with increasing S. typhimurium concentration, on the contrary, the fluorescent signals were generated. As a result, in colorimetry/fluorescence modes, S. typhimurium could be detected in the linear ranges of 103-108 CFU mL-1 and 101-107 CFU mL-1, with LODs of 1000 and 10 CFU mL-1, respectively. Importantly, different colors consistent with various S. typhimurium concentrations can be accurately classified by smartphone app and linear discriminant analysis (LDA). The smartphone-assisted data interpretation can generate complementary colorimetry and fluorescence signals without any sophisticated equipment and achieve on-site detection. Moreover, the proposed strategy could be explored for S. typhimurium monitoring in milk with satisfactory recoveries (97.6-100.4 %) in colorimetry and fluorescence mode and good classification and prediction performance in smartphone/LDA system, suggesting the feasibility and potential applications of the sensing platform.

A CRISPR/Cas12a-assisted bacteria quantification platform combined with magnetic covalent organic frameworks and hybridization chain reaction.

The total bacterial count is an important indicator of food contamination in food safety supervision and management. Recently, the CRISPR/Cas12a system integrated with nucleic acid amplification has increasingly shown tremendous potential in microorganism detection. However, a general quantification strategy for total bacteria count based on the CRISPR/Cas12a system has not yet been developed. Herein, we established a sensitive bacterial quantification strategy based on the CRISPR/Cas12a system combined with magnetic covalent organic frameworks (MCOFs) and hybridization chain reaction (HCR). MCOFs acted as a carrier, adsorbing the ssDNA as HCR trigger sequence through π-π stacking. Then, the HCR circuit produces DNA duplexes containing the PAM sequences that activate the trans-cleavage activity of Cas12a for further signal amplification. Under the optimal conditions, the proposed method can quantify total bacteria in 50 min with a minimum detection concentration of 10 CFU/mL. The successful applications in food samples confirmed the feasibility and broad application prospects.

Novel low-shrinkage dental resin containing microcapsules with antibacterial and self-healing properties.

Dental resin restorations commonly fail because of fractures and secondary caries. The aim of this research was to synthesize a novel low-shrinkage dental resin with antibacterial and self-healing properties. The low-shrinkage dental resin was obtained by incorporating a 20 wt% anti-shrinkage mixture of an expanding monomer 3,9-diethyl-3,9-dimethylol -1,5,7,11-tetraoxaspiro[5,5] undecane and an epoxy resin monomer diallyl bisphenol A diglycidyl ether (1:1, referred as "UE") and different mass fractions of self-healing antibacterial microcapsules (0%, 2.5%, 5%, 7.5%, and 10%) were incorporated into the matrix to prepare multifunctional dental resin. Polymerization shrinkage, mechanical properties, antibacterial activity, self-healing ability, and cytotoxicity of this dental resin were evaluated. The polymerization volumetric shrinkage of resin containing 20 wt% UE and 7.5 wt% microcapsules was reduced by 30.12% (4.13% ± 0.42%) compared with control. Furthermore, it exhibited high antibacterial activity and a good self-healing efficiency of 71% without adversely affecting the mechanical property and cell viability. This novel multifunctional dental resin with low polymerization shrinkage and excellent antibacterial activity and self-healing capability has potential application as a dental resin material to decrease the incidence of fractures and secondary caries.

Novel antimicrobial and self-healing dental resin to combat secondary caries and restoration fracture.

OBJECTIVE: Dental resin composites have been the most popular materials for repairing tooth decay in recent years. However, secondary caries and bulk fracture are the major hurdles that affect the lifetime of dental resin composites. This current study synthesized a novel antimicrobial and self-healing dental resin containing nanoparticle-modified self-healing microcapsules to combat secondary caries and restoration fracture. METHODS: Multifunctional dental resins containing 0-20% nanoparticle-modified self-healing microcapsules were prepared. The water contact angle, antimicrobial properties, mechanical properties, cell toxicity, and self-healing capability of the dental resins were tested. RESULTS: A novel multifunctional dental resin was synthesized. When the microcapsule mass fraction was 10%, the resin presented a strong bacteriostasis rate (80.3%) and excellent self-healing efficiency (66.1%), while the hydrophilicity, mechanical properties, and cell toxicity were not affected. SIGNIFICANCE: The novel antimicrobial self-healing dental resin is a promising candidate for use in clinical practice, which provides a simple and highly efficient strategy to combat secondary caries and restoration fracture. This novel dental resin also gives the inspiration to prolong the service life of dental restorations.

Effects of thermal cycling on bonding properties of novel low-shrinkage resin adhesive.

OBJECTIVES: The current study aimed to investigate the bonding properties of a novel low-shrinkage resin adhesive containing expanding monomer and epoxy resin monomer after thermal cycling aging treatment. METHODS: Expanding monomer of 3,9-diethyl-3,9-dimethylol-1,5,7,11-tetraoxaspiro-[5,5] undecane (DDTU) as an anti-shrinkage additive and unsaturated epoxy monomer of diallyl bisphenol A diglycidyl ether (DBDE) as a coupling agent were synthesized. A blend of DDTU and DBDE at a mass ratio of 1∶1, referred to as "UE", was added into the resin matrix at the mass fraction of 20% to prepare a novel low-shrinkage resin adhesive.Then, the methacrylate resin adhesive without UE was used as the blank control group, and a commercial resin adhesive system was selected as the commercial control group. Moreover, the resin-dentin bonding and micro-leakage testing specimens were prepared for the thermal cycling aging treatment. The bonding strength was tested, the fracture modes were calculated, the bonding fracture surface was observed by scanning electron microscope (SEM), and the dye penetration was used to evaluate the tooth-restoration marginal interface micro-leakage. All the data were analyzed statistically. RESULTS: After aging, the dentin bonding strength of the experimental group was (19.20±1.03) MPa without a significant decrease (P>0.05), that of the blank control group was (11.22±1.48) MPa with a significant decrease (P<0.05) and that of the commercial control group was (19.16±1.68) MPa without a significant decrease (P>0.05). The interface fracture was observed as the main fracture mode in each group after thermal cycling by SEM. The fractured bonding surfaces of the experimental group often occurred on the top of the hybrid layer, whereas those of the blank and commercial control groups mostly occurred on the bottom of the hybrid layer. Micro-leakage rating counts of specimens before and after thermal cycling were as follows: the experimental group was primarily 0 grade, thereby indicating that a relatively ideal marginal sealing effect could be achieved (P>0.05); meanwhile, the blank control group was primarily 1 grade, and the penetration depth of dye significantly increased after thermal cycling (P<0.05); the commercial control group was primarily 0 grade without statistical difference before and after thermal cycling (P>0.05), while a significant difference was observed between the commercial control group and experimental group after thermal cycling (P<0.05). CONCLUSIONS: The novel low-shrinkage resin adhesive containing 20%UE exhibited excellent bonding properties even after thermal cycling aging treatment, thereby showing a promising prospect for dental application.

KRASG12C mutation-induced TOPK overexpression contributes to tumour progression in non-small cell lung cancer.

KRAS mutation is the most frequent type of genetic mutation in non-small cell lung cancer (NSCLC), especially in lung adenocarcinoma. However, KRAS mutation can affect many biological processes and the mechanisms underlying KRAS mutation-mediate carcinogenesis in NSCLC have not been fully understood. In this research, we found that KRASG12C mutation was associated with the upregulation of T-LAK cell-originated protein kinase (TOPK), which is a well-known serine/threonine MAPK-like protein kinase implicated in tumorigenesis. The overexpression of TOPK significantly promoted the malignant phenotype of A549 cells, and TOPK silencing impaired the malignant phenotype with KRASG12C mutation. Moreover, we demonstrated that TOPK level was regulated by MAPK/ERK signalling and the transcription factor Elk1. TOPK was also found to promote the activation of NF-κB signalling in A549 cells with KRASG12C mutation via facilitating the phosphorylation of TAK1. In the in vivo tumorigenesis model, the administration of TOPK inhibitor OTS514 enhanced the anticancer effect of 5-FU, and the combinatory use of OTS514 and KRASG12C inhibitor AMG510 showed synergistic anti-tumour effect. These results suggest that KRAS-TOPK axis contributes to the progression of NSCLC and targeting this axis could synergize with anticancer effect of the existing chemotherapeutics.

Neural networks based on attention architecture are robust to data missingness for early predicting hospital mortality in intensive care unit patients.

Background: Although the machine learning model developed on electronic health records has become a promising method for early predicting hospital mortality, few studies focus on the approaches for handling missing data in electronic health records and evaluate model robustness to data missingness. This study proposes an attention architecture that shows excellent predictive performance and is robust to data missingness. Methods: Two public intensive care unit databases were used for model training and external validation, respectively. Three neural networks (masked attention model, attention model with imputation, attention model with missing indicator) based on the attention architecture were developed, using masked attention mechanism, multiple imputation, and missing indicator to handle missing data, respectively. Model interpretability was analyzed by attention allocations. Extreme gradient boosting, logistic regression with multiple imputation and missing indicator (logistic regression with imputation, logistic regression with missing indicator) were used as baseline models. Model discrimination and calibration were evaluated by area under the receiver operating characteristic curve, area under precision-recall curve, and calibration curve. In addition, model robustness to data missingness in both model training and validation was evaluated by three analyses. Results: In total, 65,623 and 150,753 intensive care unit stays were respectively included in the training set and the test set, with mortality of 10.1% and 8.5%, and overall missing rate of 10.3% and 19.7%. attention model with missing indicator had the highest area under the receiver operating characteristic curve (0.869; 95% CI: 0.865 to 0.873) in external validation; attention model with imputation had the highest area under precision-recall curve (0.497; 95% CI: 0.480-0.513). Masked attention model and attention model with imputation showed better calibration than other models. The three neural networks showed different patterns of attention allocation. In terms of robustness to data missingness, masked attention model and attention model with missing indicator are more robust to missing data in model training; while attention model with imputation is more robust to missing data in model validation. Conclusions: The attention architecture has the potential to become an excellent model architecture for clinical prediction task with data missingness.

A methylation-related signature for predicting prognosis and sensitivity to first-line therapies in gastric cancer.

Background: Methylation modification patterns play a crucial role in human cancer progression, especially in gastrointestinal cancers. We aimed to use methylation regulators to classify patients with gastric adenocarcinoma and build a model to predict prognosis, promoting the application of precision medicine. Methods: We obtained RNA sequencing data and clinical data from The Cancer Genome Atlas (TCGA) database (n=335) and Gene Expression Omnibus (GEO) database (n=865). Unsupervised consensus clustering was used to identify subtypes of gastric adenocarcinoma. We performed functional enrichment analysis, immune infiltration analysis, drug sensitivity analysis, and molecular feature analysis to determine the clinical application for different subtypes. The univariate Cox regression analysis and the LASSO regression analysis were subsequently used to identify prognosis-related methylation regulators and construct a risk model. Results: Through unsupervised consensus clustering, patients were divided into two subtypes (cluster A and cluster B) with different clinical outcomes. Cluster B included patients with a better prognosis outcome and who were more likely to respond to immunotherapy. We then successfully built a predictive model and found five methylation-related genes (CHAF1A, CPNE8, PHLDA3, SPARC, and EHF) potentially significant to the prognosis of patients. The 1-, 3-, and 5-year areas under the curve of the risk model were 0.712, 0.696, and 0.759, respectively. The risk score was an independent prognostic factor and had the highest concordance index among common clinical indicators. Meanwhile, the tumor microenvironment, sensitivity of chemotherapeutic drugs, molecular features, and oncogenic dedifferentiation differed significantly across the risk groups and subtypes. Conclusions: We classified patients with gastric adenocarcinoma based on methylation regulators, which has positive implications for first-line clinical treatment. The prognostic model could predict the prognosis of patients and help to promote the development of precision medicine.

Research progress of dental self-healing microcapsule materials / 口腔医学

@#The self-healing microcapsule material is one of the smart materials that can self-identify and self-heal microcracks. Adding microcapsules to dental resin composites can resist generation of microcracks and prolong service life of resin restorations. In this literature, the overview of self-healing microcapsule materials, the combined application of self-healing microcapsule materials and other modified materials, the silanization treatment of dental self-healing microcapsules, the dynamic mechanics, fatigue and aging studies on self-healing dental resins were comprehensively presented and reviewed. In addition, prospects of dental self-healing microcapsule materials were also discussed.

Genetic diversity, antibiotic resistance, and virulence profiles of Listeria monocytogenes from retail meat and meat processing.

Human listeriosis outbreaks are often associated with consumption of contaminated food, especially meat products. To better understand meat contamination of L. monocytogenes, whole genome sequencing(WGS) was performed on all detected isolates to investigate genetic relationships between retail markets and slaughterhouses. 110 and 13 isolates were isolated from 1914 food samples and 67 food and environmental samples, respectively. IIa (51/123,41.5%) and IIc (7/123,5.7%) were detected as the dominant serogroups of 123 L. monocytogenes isolates.Most isolates were penicillin-resistant (22/123,17.9%) in the phenotypic test, and all isolates were also found to be susceptible to ampicillin, meropenem, and vancomycin. All of them harbored virulence-associated genes and premature stop codons (PMSCs) in inlA genes were occurred in 35 strains. 22 multilocus sequence types and 19 clonal complexes were identified with ST9 being most common. This study also showed the prevalence and uniqueness of strains from Jilin, China compared with worldwide epidemic international strains. The findings of this study will contribute to the epidemiological understanding of transmission of L. monocytogenes from production and circulation in the region of northern China.

Multi-omics consensus portfolio to refine the classification of lung adenocarcinoma with prognostic stratification, tumor microenvironment, and unique sensitivity to first-line therapies.

Background: Molecular classification of lung adenocarcinoma (LUAD) based on transcriptomic features has been widely studied. The complementarity of data obtained from multilayer molecular biology could help the LUAD classification via combining multi-omics information. Methods: We successfully divided samples from the The Cancer Genome Atlas (TCGA) (n=437) into four subtypes (CS1, CS2, CS3 and CS4) by 10 comprehensive multi-omics clustering methods in the "movics" R package. Meanwhile, external validation sets from different sequencing technologies proved the robustness of the grouping model. The relationship between subtypes, prognosis, molecular features, tumor microenvironment and response to first-line therapy was further analyzed. Next we used univariate Cox regression analysis and Lasso regression analysis to explore the application of biomarkers in clinical prognosis and constructed a prognostic model. Results: CS1 showed the worst overall survival (OS) among all four clusters, possibly related to its poor immune infiltration, higher tumor mutation and worse chromosomal stability. Patients in different subtypes differed significantly in cancer stem cell characteristics, activation of cancer-related pathways, sensitivity to chemotherapy and immunotherapy. The prognostic model showed good predictive performance. The 1-, 2- and 3-year areas under the curve of risk score were 0.779, 0.742 and 0.678, respectively. Seven genes (DKK1, TSPAN7, ID1, DLGAP5, HHIPL2, CD40 and SEMA3C) used to build the model may be potential therapeutic targets for LUAD. Conclusions: Four LUAD subtypes with different molecular characteristics and clinical implications were identified successfully through bioinformatic analysis. Our results may contribute to precision medicine and inform the development of rational clinical strategies for targeted and immune therapies.

Novel antibacterial dental resin containing silanized hydroxyapatite nanofibers with remineralization capability.

OBJECTIVES: Secondary caries is the primary issue that causes restoration failure. The objectives of this study were to: (1) synthesize silanized hydroxyapatite nanofibers loaded with erythromycin (s-HAFs@EM); (2) evaluate the mechanical property, antibacterial activity, and remineralization capability of the novel dental resin containing s-HAFs@EM. METHODS: s-HAFs were prepared by the solvothermal approach and loaded with EM. Characterization and antibacterial activity were evaluated. Subsequently, s-HAFs@EM were incorporated into dental resin at different mass fractions (5 %, 10 %, 15 %, and 20 %), and then they were submitted to characterization, including mechanical property, antibacterial activity, remineralization capability, and cytotoxicity. RESULTS: s-HAFs@EM were successfully synthesized, and they exhibited excellent antibacterial activity. Resin containing 15 % s-HAFs@EM exhibited the best flexural strength (118.67 ± 15.71 MPa) and elastic modulus (2.02 ± 0.30 GPa) (P < 0.05), which were increased by 65.43 % and 90.7 %, compared to those of neat resin, respectively. Resin with 15-20 % s-HAFs@EM showed high antibacterial rate (>85 %) when compared control group (P < 0.05). Furthermore, resin also exhibited a definite remineralization capability and good biosafety in vitro. SIGNIFICANCE: This novel multifunctional resin with improved mechanical property, desirable antibacterial activity and remineralization capability is promising to combat secondary caries.

Ferulic acid alleviates alveolar epithelial barrier dysfunction in sepsis-induced acute lung injury by activating the Nrf2/HO-1 pathway and inhibiting ferroptosis.

CONTEXT: Ferulic acid (FA) has antioxidative and anti-inflammatory effects, and is a promising drug to treat sepsis. OBJECTIVE: To study the therapeutic effect of FA in sepsis-induced acute lung injury (ALI) and its underlying mechanisms. MATERIALS AND METHODS: The caecal ligation and puncture (CLP) manoeuvre was applied to establish a murine model of sepsis-induced ALI, and female BALB/c mice (6 mice per group) were subjected to 100 mg/kg FA or 0.8 mg/kg ferrostatin-1 (Fer-1, ferroptosis inhibitor) treatment to clarify the role of FA in preserving alveolar epithelial barrier function and inhibiting ferroptosis. Lipopolysaccharide (LPS; 500 ng/mL)-induced cell models were prepared and subjected to FA (0.1 µM), sh-Nrf2, and Fe (Fe-citrate, ferroptosis inducer; 5 M) treatment to study the in vitro effect of FA on LPS-induced alveolar epithelial cell injury and the role of the Nrf2/HO-1 pathway. RESULTS: We found that FA decreased the lung injury score (48% reduction), lung wet/dry weight ratio (33% reduction), and myeloperoxidase activity (58% reduction) in sepsis-induced ALI. Moreover, FA inhibited ferroptosis of alveolar epithelial cells and improved alveolar epithelial barrier dysfunction. The protective role of FA against alveolar epithelial barrier dysfunction could be reversed by the ferroptosis inducer Fe-citrate, suggesting that FA alleviates alveolar epithelial barrier dysfunction by inhibiting ferroptosis. Mechanistically, we found that FA inhibited ferroptosis of alveolar epithelial cells by activating the Nrf2/HO-1 pathway. CONCLUSION: Collectively, our data highlighted the alleviatory role of ferulic acid in sepsis-induced ALI by activating the Nrf2/HO-1 pathway and inhibiting ferroptosis, offering a new basis for sepsis treatment.

Quantitative structure-toxicity relationships of halobenzoquinone isomers on DNA reactivity and genotoxicity.

Halobenzoquinones (HBQs) are an emerging class of drinking water disinfection byproducts that have been predicted as bladder carcinogens. However, data on the genotoxicity of HBQs are still scarce. This study performed a quantitative structure-toxicity relationship (QSTR) analysis of HBQ isomers on DNA reactivity and genotoxicity. The interaction of HBQs with calf thymus DNA (ct-DNA) was studied using multi-spectroscopic and molecular docking techniques. UV-Vis absorption spectra observed a significant hyperchromic effect with the increase of HBQ concentration. The fluorescence intensity of both probe-ct-DNA decreased with the increasing concentration of HBQs, indicating that the interaction mode between each HBQs and DNA was quite complicated, and there were both minor groove binding and intercalation binding. Molecular docking showed that HBQs interacted with DNA predominantly via hydrogen bond at guanine-rich areas in the minor groove of DNA. The genotoxicity of HBQs on human hepatocytes (L-02) was evaluated by micronucleus test, and the results showed that HBQs could cause significant chromosomal damage. The rank order of HBQ isomers on DNA reactivity and genotoxicity was 2,5-HBQs > their corresponding 2,6-HBQs. QSTR analysis found that dipole moment is the key structural descriptor influencing both DNA reactivity and genotoxicity of HBQ isomers. This study suggested that HBQs have caused genotoxicity which was influenced by their isomeric effects, warranting a comprehensive understanding of the genotoxic and carcinogenic risks associated with HBQs exposure.

Immobilization mechanism of cesium in geopolymer: Effects of alkaline activators and calcination temperature.

Geopolymer is always regarded as a promising material for the immobilization of radioactive waste. In the present study, the stabilization of Cs in geopolymers activated by NaOH and Na2SiO3 solutions and calcined at various temperatures was studied via toxicity characteristic leaching procedure (TCLP), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope and energy dispersive spectroscopy (SEM-EDS), solid-state nuclear magnetic resonance (SSNMR), and N2 adsorption-desorption isotherm. For both NaOH-activated and Na2SiO3-activated geopolymers, the leaching concentrations of Cs decreased with the increase of calcination temperature. Specifically, most of the amorphous substance was crystallized to nepheline at 1000 °C for NaOH-activated geopolymer, and Cs+ can be incorporated into the structure of nepheline, contributing to the reduction of Cs leaching concentration. However, the amorphous structure was still maintained for Na2SiO3-activated geopolymer even after calcination at 1000 °C. It has been deduced that the main structure of Na2SiO3-activated geopolymer after calcination at 1000 °C should be in short-range order and Cs+ can be locked in a micro "crystal" structure. In addition, the change of specific surface area was not fully consistent with the decreasing trend of Cs leaching concentration. Therefore, the inner structure and the specific surface area of geopolymer should have a combined effect on the leaching behavior of Cs. This study can provide new insights into the application of geopolymer to immobilize radionuclides.

Evolution of polycyclic aromatic hydrocarbons in the surface sediment of southern Jiaozhou Bay in northern China after an accident of oil pipeline explosion.

The 2013 "Qingdao oil pipeline explosion" contaminated about 2.5 km of shoreline in the Jiaozhou Bay area and aroused widespread concern because of the serious casualties even though it was not the most severe oil-spill contamination in China. To evaluate the long-term impact, we collected thirty-three surface sediment samples after 3 years of the accident, with sixteen polycyclic aromatic hydrocarbons (PAHs) detected. Spatial-temporal variation in PAHs revealed that a minimal impact might still be present after 3 years. Source analysis combined with a one-way ANOVA showed that pyrolytic sources were consistently predominant. The environmental impact was already minimal 3 years later and negligible thereafter. Although the cancer risk has decreased over the years, there has always been a potential hazard to human for specific occupation, with all of the risk values exceeded 10-6. This study offers a reference for assessing the long-term impact of oil spills in similar bay areas.

Influence of aluminate and silicate on selenate immobilization using alkaline-earth metal oxides and ferrous salt.

Effects of aluminate and silicate species on the SeO42- immobilization using alkali-earth metal oxides and ferrous species have not been clearly elucidated. In the present study, Al and Si species were separately added into MgO/Fe(II) and CaO/Fe(II) reactions containing SeO42-, studied by toxicity characteristic leaching procedure (TCLP), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray absorption fine structure (XAFS), and PHREEQC simulation. Approximately 42 % of SeO42- was reduced to SeO32- for MgO/Fe(II) reaction in the presence of Al species, being consistent with the case without Al species. The Al species only showed slight inhibition of Se leaching for the MgO/Fe(II) reaction. Most of Se oxyanions were adsorbed onto Mg(OH)2 through outer-sphere complexation. For CaO/Fe(II) reaction, all of SeO42- was reduced to SeO32- with or without Al species. However, the Se leaching amount (3 %) of sample added with Al species (CE3) is much lower than that (12 %) of sample without Al species (CE2). This is mainly because SeO32- can be sorbed onto the iron-based minerals through binuclear bidentate corner-sharing (2C) complexation instead of monodentate mononuclear corner-sharing (1V) complexation of the case without Al species. On the other hand, SeO42- was not reduced to SeO32- in the presence of silicate, and almost all of Se was leached out for silicate-contained samples except CaO/Fe(II) reaction with the addition of Al species. This is due to the polymerization of Al and Si species under a high-alkalinity environment, thereby stabilizing SeO42- in the amorphous silicon-aluminum structure and contributing to the decrease of Se leaching.