Comparison of black carbon, primary and secondary brown carbon light absorption and direct solar absorption at the foothill and summit of Mt. Hua, China.

Atmospheric black carbon (BC), primary and secondary brown carbon (BrCpri and BrCsec) are the light-absorbing carbonaceous aerosol components. The vertical changes in the BC and BrC distributions are not generally known. Here, we presented a study of the spectral light absorption properties, direct solar absorption, and potential source areas of BC and BrC at the foothill (375 m a.s.l.) and summit (2060 m a.s.l.) of Mt. Hua, China. More than tripled BC and BrC light absorption coefficient were observed at the foothill compared to the summit. The dominant carbonaceous light-absorbing was attributed to BC with the percentages of 77 % (foothill) and 79 % (summit), respectively. The light absorption coefficient and direct solar absorption of BrCpri were much higher than those of BrCsec at foothill, especially in winter. The enhancing contributions of BrCsec light absorption coefficient and direct solar absorption were observed with high RH and visibility at the summit. The light absorption properties of BC, BrCpri, and BrCsec may be attributed to the emissions, meteorological conditions, and photochemical oxidation. The inferred potential source spatial distributions of BC and BrCpri showed different patterns at the foothill and summit. The results underlined the primary emission effects (including BC and BrCpri) at the foothill and the importance of BrCsec at the summit, respectively.

Feasibility of balanced steady-state free precession sequence at 1.5T for the evaluation of hepatic steatosis in obese children and adolescents.

OBJECTIVES: To determine the feasibility of balanced steady-state free precession (b-SSFP) imaging for measuring hepatic steatosis in obese children and adolescents, using proton magnetic resonance spectroscopy (1H MRS) as reference standard. METHODS: 182 obese Chinese paediatric patients underwent conventional T1-weighted dual echo MRI, 1H MRS and b-SSFP imaging for non-invasive assessment of hepatic steatosis. RESULTS: There was a strong positive correlation between liver fat fraction (FF) on T1-weighted dual echo MRI and 1H MRS-determined liver fat content (LFC) (r = 0.964, p < .001), and a strong negative correlation between the ratio of liver signal intensity (SI) to spleen SI (L/S) on b-SSFP and LFC (r = -0.896, p < .001). ROC curve analysis based on a diagnostic threshold of 1H MRS-determined LFC >50 mg/g (>5 % by wet weight) showed areas under the curves for FF and L/S at 0.989 (0.976-1.000) and 0.926 (0.888-0.964), respectively. Optimal FF and L/S cut-off values identified patients with hepatic steatosis with 97.9 % and 86.5 % sensitivity and 93.4 % and 93.4 % specificity, respectively. CONCLUSIONS: Following further validation, b-SSFP at 1.5T has potential as a feasible technique for evaluation of hepatic steatosis in obese paediatric patients with limited breath-holding capacity. KEY POINTS: • L/S on b-SSFP images closely correlated with 1 H MRS-determined LFC. • b-SSFP has high diagnostic accuracy for hepatic steatosis in obese children. • 100% of obese paediatric subjects are imaged successfully using b-SSFP sequence. • b-SSFP has potential to evaluate hepatic steatosis in children with poor breath-hold.

Role of interferon regulatory factor-1 in lipopolysaccharide-induced mitochondrial damage and oxidative stress responses in macrophages.

Sepsis causes many early deaths; both macrophage mitochondrial damage and oxidative stress responses are key factors in its pathogenesis. Although the exact mechanisms responsible for sepsis-induced mitochondrial damage are unknown, the nuclear transcription factor, interferon regulatory factor-1 (IRF-1) has been reported to cause mitochondrial damage in several diseases. Previously, we reported that in addition to promoting systemic inflammation, IRF-1 promoted the apoptosis of and inhibited autophagy in macrophages. In the present study, we hypothesized that lipopolysaccharide (LPS)-induced IRF-1 activation in macrophages may promote mitochondrial damage and oxidative stress. In vitro, LPS was found to promote IRF-1 activation, reactive oxygen species (ROS) production, adenosine triphosphate (ATP) depletion, superoxide dismutase (SOD) consumption, malondialdehyde (MDA) accumulation and mitochondrial depolarization in macrophages in a time- and dose-dependent manner. These effects were abrogated in cells in which IRF-1 was knocked down. Furthermore, IRF-1 overexpression increased LPS-induced oxidative stress responses and mitochondrial damage. In vivo, peritoneal macrophages obtained from IRF-1 knockout (KO) mice produced less ROS and had less mitochondrial depolarization and damage following the administration of LPS, when compared to their wild-type (WT) counterparts. In addition, IRF-1 KO mice exhibited a decreased release of mitochondrial DNA (mtDNA) following the administration of LPS. Thus, IRF-1 may be a critical factor in augmenting LPS-induced oxidative stress and mitochondrial damage in macrophages.

Multinodule abnormalities of the tracheobronchus: bronchoscopy findings and clinical diagnosis.

BACKGROUND AND AIMS: Bronchoscopy is an important method for diagnosing respiratory disease. Multiple tracheobronchial nodules are rarely reported and their causes remain unclear. OBJECTIVES: The aim of this study was to describe the clinical characteristics of multiple nodule tracheobronchial abnormalities found under bronchoscopy caused by different diseases. METHODS: Eighty-seven patients with multiple tracheobronchial nodules were enrolled in this study. The characteristics of the multinodule lesions and the patient were diagnosed based on the pathology findings in our hospital. Chest computed tomography images were retrospectively reviewed by pulmonologists and radiologist. RESULTS: In 55 patients with definite pathological diagnosis, 16 (29%) patients were diagnosed as tuberculosis (TB) granuloma; 23 (41.8%) cases were diagnosed as malignant disease; 12 (21.8%) cases were diagnosed as tracheobronchopathia osteochondroplastica; 2 (3.6%) cases were diagnosed as sarcoidosis; and one case (1.8%) was diagnosed as lymphoma and one case (1.8%) as fungal infection. There were 32 cases of chronic inflammation. There was no relationship between nodule distribution and the pathological diagnosis. Malignant nodules usually smaller with a pale outlook, while nodules with larger size and smooth and intact mucosa usually turn out to be granuloma of unknown reason. CONCLUSION: The major causes of mutinodule lesions observed using bronchoscopy are tumor and TB. The presence of multiple endotracheobronchial nodules suggest that pulmonary lesion is present, and biopsy should be performed. Malignant nodules can be diagnosed by appearance and biopsy. Pathology results of TB, sarcoidosis and fungal infection can turn out to be granuloma of unknown reason. Further diagnosis needs other clinical materials.

The clock gene PER1 plays an important role in regulating the clock gene network in human oral squamous cell carcinoma cells.

The various clock genes in normal cells, through their interaction, establish a number of positive and negative feedback loops that compose a network structure. These genes play an important role in regulating normal physiological activities. The expression of clock gene PER1 is decreased in many types of cancer. PER1 is highly correlated with the initiation and progression of cancer by regulating numerous downstream genes. However, it is still unclear whether the lower expression of PER1 in cancer can influence the expression of other clock genes in the clock gene network. In this study, we used short hairpin RNA interference to knock down PER1 effectively in SCC15 human oral squamous cell carcinoma cells. These cancer cells later were subcutaneously injected into the back of nude mice. We discovered that after PER1 knockdown, apoptosis was decreased and cell proliferation and in vivo tumor formation were enhanced. Quantitative real-time PCR result indicated that in vitro and in vivo cancer cells after PER1 knockdown, PER2, DEC1, DEC2, CRY1, CRY2 and NPAS2 were significantly down-regulated at the mRNA level, while PER3, TIM, RORα and REV-ERBα were significantly up-regulated. It prompts that the role of PER1 in carcinogenesis is exerted not only by regulating downstream genes, but also through the synergistic dysregulation of many other clock genes in the clock gene network.

Inhibition of Alveolar Macrophage Pyroptosis Reduces Lipopolysaccharide-induced Acute Lung Injury in Mice.

BACKGROUND: Pyroptosis is the term for caspase-1-dependent cell death associated with pro-inflammatory cytokines. The role of alveolar macrophage (AM) pyroptosis in the pathogenesis of the acute lung injury and acute respiratory distress syndrome (ALI/ARDS) remains unclear. METHODS: C57BL/6 wild-type mice were assigned to sham, lipopolysaccharide (LPS) + vehicle, LPS + acetyl-tyrosyl-valyl- alanyl-aspartyl-chloromethylketone (Ac-YVAD-CMK) and LPS + Z-Asp-Glu-Val-Asp-fluoromethylketone groups. Mice were given intraperitoneal (IP) injections of LPS. Drugs were IP injected 1 h before LPS administration. Mice were sacrificed 16 h after LPS administration, and AMs were isolated. Western blot analysis for active caspase-1 and cleaved caspase-3, evaluation of lung injury and a cytokine release analysis were performed. AMs were treated with LPS and adenosine triphosphate (ATP); caspase-1-dependent cell death was evaluated using flow cytometry; the apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) pyroptosomes were examined by immunofluorescence. RESULTS: The expression of activated caspase-1 in AMs was enhanced following LPS challenge compared with the sham group. In the ex vivo study, the caspase-1/propidium iodide-positive cells, caspase-1 specks and ASC pyroptosomes were up-regulated in AMs following LPS/ATP stimulation. The specific caspase-1 inhibitor Ac-YVAD-CMK inhibited the activation of caspase-1 and pyroptotic cell death. Ac-YVAD-CMK also reduced the lung injury, pulmonary edema and total protein in bronchoalveolar lavage fluid (BALF). In addition, Ac-YVAD-CMK significantly inhibited interleukin-α2 (IL-1α2) release both in serum and BALF and reduced the levels of IL-18, tumor necrosis factor-α± (TNF-α±), High Mobility Group Box 1 (HMGB1) in BALF during LPS-induced ALI/ARDS. CONCLUSIONS: This study reported AM pyroptosis during LPS-induced ALI/ARDS in mice and has demonstrated that Ac-YVAD-CMK can prevent AM-induced pyroptosis and lung injury. These preliminary findings may form the basis for further studies to evaluate this pathway as a target for prevention or reduction of ALI/ARDS.

Epidemiology of Suicide and Associated Socio-Demographic Factors in Emergency Department Patients in 7 General Hospitals in Northwestern China.

BACKGROUND: This study aimed to illustrate the characteristics of suicide attempters treated in the Emergency Departments of 7 general hospitals in Xi'an and to provide relevant data for early psychological treatment. MATERIAL AND METHODS: Between October 2010 and September 2014, 155 suicide attempters were treated in the Emergency Departments. Data were collected using a semi-structured questionnaire. Descriptive statistics, chi-square tests, and multivariate analyses were used to identify the factors associated with suicidal behaviors. RESULTS: Females outnumbered males at a ratio of 3.7 to 1. The greatest proportion of cases was in the age group of 21 to 30 years (52.9%). Patients who finished middle school or high school accounted for most of the suicide attempters (50.3%). The most common method used for attempted suicide was drug ingestion (86.5%). The majority of cases attempted suicide at home (74.8%) during the night. Marriage frustration, work and study problems, family fanaticism and conflict, somatic disease, and history of mental disorders were all significantly associated with suicide attempts. The ratio of patients to be discharged or to die were similar in occupation, marital status, and the place of suicide attempt; however, the results were different in gender, age, educational level, methods used for suicide, time of day, and reason. CONCLUSIONS: Suicide is an important public health problem and is multidimensional in nature. Future studies with larger samples are expected to provide more specific knowledge of the effect of each social factor on the suicide risk in Chinese in order to improve the prevention of suicides.

Acetobacteroides hydrogenigenes gen. nov., sp. nov., an anaerobic hydrogen-producing bacterium in the family Rikenellaceae isolated from a reed swamp.

A strictly anaerobic, mesophilic, carbohydrate-fermenting, hydrogen-producing bacterium, designated strain RL-C(T), was isolated from a reed swamp in China. Cells were Gram-stain-negative, catalase-negative, non-spore-forming, non-motile rods measuring 0.7-1.0 µm in width and 3.0-8.0 µm in length. The optimum temperature for growth of strain RL-C(T) was 37 °C (range 25-40 °C) and pH 7.0-7.5 (range pH 5.7-8.0). The strain could grow fermentatively on yeast extract, tryptone, arabinose, glucose, galactose, mannose, maltose, lactose, glycogen, pectin and starch. The main end products of glucose fermentation were acetate, H2 and CO2. Organic acids, alcohols and amino acids were not utilized for growth. Yeast extract was not required for growth; however, it stimulated growth slightly. Nitrate, sulfate, sulfite, thiosulfate, elemental sulfur and Fe(III) nitrilotriacetate were not reduced as terminal electron acceptors. Aesculin was hydrolysed but not gelatin. Indole and H2S were produced from yeast extract. The G+C content of the genomic DNA was 51.2 mol%. The major cellular fatty acids were iso-C15 : 0, anteiso-C15 : 0 and C16 : 0. The most abundant polar lipid of strain RL-C(T) was phosphatidylethanolamine. 16S rRNA gene sequence analysis revealed that the isolate belongs to the uncultured Blvii28 wastewater-sludge group (http://www.arb-silva.de/) in the family Rikenellaceae of the phylum Bacteroidetes, and shared low sequence similarities with the related species Alistipes shahii WAL 8301(T) (81.8 %), Rikenella microfusus ATCC 29728(T) (81.7 %) and Anaerocella delicata WN081(T) (80.9 %). On the basis of these data, a novel species in a new genus of the family Rikenellaceae is proposed, Acetobacteroides hydrogenigenes gen. nov., sp. nov. The type strain of the type species is RL-C(T) ( = JCM 17603(T) = DSM 24657(T) = CGMCC 1.5173(T)).

Biodegradation of decabromodiphenyl ether (BDE-209) by a metal resistant strain, Bacillus cereus JP12.

A metal resistant bacterial strain, Bacillus cereus JP12, could use decabromodiphenyl ether (BDE-209) as the sole carbon and energy source for growth in mineral salt medium. Under the conditions of pH 6.0, 30°C, 150 rpm and an inoculum of OD600=0.6, more than 88% of the initial BDE-209 (1mg/L) was degraded after 12 days. The addition of appropriate surfactants and additional carbon sources could enhance the biodegradation efficiency of BDE-209. The presence of Cu(2+) (≤ 8 mg/L) and Zn(2+) (≤ 15 mg/L) provided a slight stimulating effect on BDE-209 removal. However, BDE-209 biodegradation efficiency was decreased when adding higher levels of metals due to reduced substrate availability caused by excess metal adsorption into the cell surface. Biosorption of heavy metals by JP12 led to release of light metals such as K(+) and Na(+). A BDE-209 biodegradation pathway was proposed on the basis of metabolite identification.

Inhibition of nuclear factor-κB activity enhanced chemosensitivity to cisplatin in human lung adeno-carcinoma A549 cells under chemical hypoxia conditions.

BACKGROUND: Tumor hypoxia, one of the features of solid tumors, is associated with chemo-resistance. Recently, nuclear factor-κB (NF-κB) was found to be activated during hypoxia. However, the impact of NF-κB activation on chemo-resistance during hypoxia remains unknown. METHODS: Human lung adenocarcinoma A549 cells were transfected with NF-κB p65siRNA and treated with cobalt chloride (CoCl2) to mimic hypoxia in the presence or absence of cisplatin. NF-κB expression was measured by Western blotting, immune-fluorescence and real-time PCR. Hypoxia-inducible factor-1α (HIF-1α) and Bcl-2 expression were determined by Western blotting. Cell apoptosis and survival with half-maximum inhibitory concentration (IC50) of cisplatin were determined by Annexin V-FITC/PI and 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT), respectively. RESULTS: Exposure of A549 cells to CoCl2 increased nuclear HIF-1a protein expression, and enhanced NF-κB p65 protein nuclear accumulation (the mark of NF-κB activation) in a time and dose dependant manner. CoCl2 did not promote apoptosis in A549 cells; on the contrary, it reduced cisplatin-induced apoptosis and increased the IC50 of cisplatin. However, when we inhibited CoCl2-induced activation of NF-κB through NF-κB p65siRNA, cisplatin-induced apoptosis was increased and IC50 of cisplatin was reduced to levels similar to those in control cells. Meanwhile, CoCl2-induced Bcl-2 overexpression was down-regulated in the presence of cisplatin when NF-κB activity was inhibited. CONCLUSION: Up-regulating Bcl-2 might be involved in NF-κB activation induced resistance to cisplatin in A549 cells under CoCl2-induced chemical hypoxia.

Effect of copper on in vivo fate of BDE-209 in pumpkin.

A 60-day growth chamber experiments were performed to investigate the effect of Cu stress on the uptake, translocation and metabolism of decabromodiphenyl ether (BDE-209) by pumpkin. A total of nine debrominated metabolites (de-PBDEs), two hydroxylated PBDEs (OH-PBDEs) and one methoxylated PBDEs (MeO-PBDEs) were detected in the tested plants. Concentrations of the total debrominated, hydroxylated or methoxylated metabolites generally followed the order of roots>stems>leaves, and de-PBDEs>OH-PBDEs>MeO-PBDEs. These results indicate that metabolism occurred preferentially in roots than in stems and leaves. The addition of moderate dosage of Cu (50mg/kg) resulted in increment in OH-PBDE concentrations in plant tissues, whereas higher concentrations of Cu could inhibit uptake and metabolism of BDE-209. No in vivo mineralization of BDE-209 was detected in the plants. These results provide valuable information about the behavior of BDE-209 in plant tissues under heavy metal exposure.

[Effects of different patterns of hypoxia on renin angiotension system in serum and tissues of rats].

OBJECTIVE: To Investigate the influences of chronic intermittent hypoxia (CIH) and continuous hypoxia (CH) on renin angiotensin system (RAS) in serum and tissues of rats, and therefore to investigate the mechanism of CIH-induced hypertension and hypoxia induced pulmonary hypertension. METHODS: Eighteen male Sprague-Dawley (SD) rats were divided into 3 groups: CIH group, CH group and control group (UC). CIH rats were subjected to alternating cycles of hypoxia (6% ∼ 8% O(2) in N(2) for 20 ∼ 25 s) and normoxia (21% O(2) in N(2) for 2 min) every 180 s for 7 h/d. CH rats were consistently given nitrogen (oxygen concentration 8% - 12% in the cabin, 7 h/d), while the UC rats were not treated. RESULTS: Systolic blood pressure (SBP) in the CIH rats at the end of 6th week was significantly elevated compared with baseline SBP (P < 0.001), and that in the CH and the UC rats (P < 0.05). At the end of 6th week, the expression of ACE and ACE2 in the renal arteriole was significantly different (P < 0.05), and the levels of AngII in serum and kidney tissues were increased. Ang-(1-7) was decreased in the CIH rats compared with the CH and the UC rats (P < 0.05). The levels of AngII in pulmonary tissues were increased, while the levels of Ang-(1-7) were decreased in the CH rats compared with the CIH and the UC rats (P < 0.05). SBP showed a positive correlation with AngII in serum and kidney tissues, and a negative correlation with Ang-(1-7) in serum and kidney tissues. There were significant differences in arterial wall thickness, WT%, and WA% of renal arterioles and pulmonary arterioles among the 3 groups. Wall thickness of pulmonary arterioles and kidney arterioles was positively correlated with AngII in pulmonary and kidney tissues (r = 0.386, 0.414, P < 0.05), and negatively correlated with Ang-(1-7) (r = -0.401, -0.394, P < 0.05). CONCLUSION: CIH and CH showed different effects on RAS in the serum and the tissues of rats. CIH mainly affected levels of RAS in the serum, kidney tissues and renal arterioles, and was closely related with blood pressure. CH mainly affected the levels of RAS in lung tissues and pulmonary small arteries, which may be related with pulmonary, hypertension and pulmonary arterial remodeling.

Iron removal from kaolin using thiourea assisted by ultrasonic wave.

In the present study a bleaching process of a kaolinite was carried out using thiourea as the leachant agent in the iron removal process, in the absence and presence of ultrasound. The effect of thiourea was investigated together with other factors, such as thiourea concentration, temperature, treatment time, and ultrasonic parameters. The optimum conditions for the maximum whiteness of 89% with ultrasound were determined as follows: reaction temperature, 20 °C; ultrasound frequency, 80 kHz; ultrasound power, 500 W; thiourea concentration, 0.4 wt.%; pH, 3.0; reaction time, 20 min. The assistance of ultrasound led to a remarkable acceleration for the iron leaching process, and dramatic reduction in the concentration of leach reagent, irradiation time, and reaction temperature, when compared with the conventional bleaching method using thiourea in the absence of ultrasound.

[A study of the related pathways of oxidative stress in chronic intermittent hypoxia rats and the effect of N-acetylcysteine].

OBJECTIVE: To study the relation of oxidative stress with systolic blood pressure (SBP) and renin-agiotensin system (RAS) in a rat model of chronic intermittent hypoxia (CIH), and to investigate the preventive effect and mechanism of N-acetylcysteine (NAC) in CIH-induced hypertension. METHODS: Twenty-four male Sprague-Dawley (SD) rats were divided into 4 groups: CIH+NAC group (CIH1), CIH+normal saline (NS) group (CIH2), CIH control group (CIH3) and blank control group (UC). CIH rats were subjected to alternating cycles of hypoxia (6%-8% O2 in N2 for 20-25 s) and normoxia (21% O2 in N2 for 2 min) every 180 s for 7 h per day. Rats in the CIH1 group were treated with NAC (800 ml×kg(-1)×d(-1)) by intraperitoneal injection, and those in the CIH2 group were treated with NS (5 ml×kg(-1)×d(-1)). RESULTS: SBP in the CIH2 and CIH3 groups at the end of 6th week was significantly elevated compared with the baseline SBP (P<0.001) and those in the CIH1 and the UC groups (P<0.05). The expression of angiotensin-converting enzyme (ACE) and ACE2 in renal arterioles was significantly different (P<0.05), and the levels of angiotensin II (AngII) in the serum and kidney tissues, oxidation of low density lipoprotein (ox-LDL) and malondialdehyde (MDA) in the serum were increased. Ang-(1-7) and the inhibitory capability for hydroxyl free radicals in the serum were decreased significantly in CIH2 and CIH3 groups compared with CIH1 and UC (P<0.05) groups at the end of 6th week. SBP showed a positive correlation with AngII in serum and kidney tissues, but showed a negative correlation with Ang-(1-7) in serum and kidney tissues. The levels of MDS and ox-LDL in serum showed a positive correlation with AngII in serum and kidney tissues respectively, but showed a negative correlation with Ang-(1-7) in serum and kidney tissues respectively. The inhibitory capability for hydroxyl free radicals in serum showed a positive correlation with Ang-(1-7), but a negative correlation with AngII. The level of ox-LDL showed a positive correlation with MDA, but a negative correlation with the inhibitory capability for hydroxyl free radicals. There were no significant difference between CIH1 and UC groups in parameters except of SBP and AngII (P<0.05). All the data were not different between CIH2 and CIH3 groups (P>0.05). CONCLUSIONS: CIH caused oxidative stress and RAS imbalance in rats. The imbalance of RAS in CIH rats was related with oxidative stress. The imbalance of RAS and oxidative stress may be one of the important mechanisms for CIH-induced hypertension. NAC can prevent CIH-induced hypertension through modulation of RAS by its anti-oxidative effect.

A nanoparticle amplification based quartz crystal microbalance DNA sensor for detection of Escherichia coli O157:H7.

A quartz crystal microbalance (QCM) DNA sensor, based on the nanoparticle amplification method, was developed for detection of Escherichia coli O157:H7. A thiolated single-stranded DNA (ssDNA) probe specific to E. coli O157:H7 eaeA gene was immobilized onto the QCM sensor surface through self-assembly. The hybridization was induced by exposing the ssDNA probe to the complementary target DNA, and resulted in the mass change and therefore frequency change of the QCM. Streptavidin conjugated Fe(3)O(4) nanoparticles (average diameter=145 nm) were used as "mass enhancers" to amplify the frequency change. Synthesized biotinylated oligonucleotides as well as E. coli O157:H7 eaeA gene fragments (151 bases) amplified using asymmetric PCR with biotin labeled primers were tested. As low as 10(-12)M synthesized oligonucleotides and 2.67 x 10(2) colony forming unit (CFU)/ml E. coli O157:H7 cells can be detected by the sensor. Linear correlation between frequency change and logarithmic number of bacterial cell concentration was found for E. coli O157:H7 from 2.67 x 10(2) to 2.67 x 10(6)CFU/ml.

A QCM immunosensor for Salmonella detection with simultaneous measurements of resonant frequency and motional resistance.

A quartz crystal microbalance (QCM) immunosensor was described for the detection of Salmonella Typhimurium with simultaneous measurements of the resonant frequency and motional resistance. The immunosensor was fabricated using protein A for the antibody immobilization. High-frequency impedance analysis indicated that the changes in resonant frequency and motional resistance (DeltaF and DeltaR) of the QCM were significant while the changes in static capacitance, motional capacitance, and motional inductance were insignificant. In the direct detection of S. Typhimurium in chicken meat sample, DeltaF and DeltaR were proportional to the cell concentration in the range of 10(5) - 10(8) and 10(6) - 10(8) cells/ml, respectively. Using anti-Salmonella-magnetic beads as a separator/concentrator for sample pretreatment as well as a marker for signal amplification, the detection limit was lowered to 10(2) cells/ml based on the DeltaR measurement; however, DeltaF was not related to the cell concentration. No interference was observed from E. coli K12 or the sample matrix.

Evaluation of a capillary immunoassay system for detection of Salmonella typhimurium in poultry products.

A capillary immunoassay system was constructed and optimized for detection of Salmonella Typhimurium. The system consisted of a capillary bioseparator-bioreactor and a flow-injection electrochemical detector. Three methods were compared for immobilizing antibodies on the inner surface of silica capillary columns; these methods were based on the use of a homobifunctional cross-linker glutaraldehyde, a heterobifunctional cross-linker N-succinimidyl-4-maleimidobutyrate, and biotin-streptavidin chemistry, respectively. The glutaraldehyde method gave the best reproducibility with a relative standard deviation of 1 to 6% for detection of Salmonella Typhimurium. The optimized immunoassay system could detect Salmonella Typhimurium in chicken breast and ground turkey meats with a detection limit of 2.4 x 10(3) and 2.4 x 10(4) CFU/ml, respectively. The total detection time was less than 2.5 h without any preenrichment. When stored at 4 degrees C, the immunocolumns could retain their activities for at least 3 months.

Magnetic nanoparticle-antibody conjugates for the separation of Escherichia coli O157:H7 in ground beef.

The immunomagnetic separation with magnetic nanoparticle-antibody conjugates (MNCs) was investigated and evaluated for the detection of Escherichia coli O157:H7 in ground beef samples. MNCs were prepared by immobilizing biotin-labeled polyclonal goat anti-E. coli antibodies onto streptavidin-coated magnetic nanoparticles. For bacterial separation, MNCs were mixed with inoculated ground beef samples, then nanoparticle-antibody-E. coli O157:H7 complexes were separated from food matrix with a magnet, washed, and surface plated for microbial enumeration. The capture efficiency was determined by plating cells bound to nanoparticles and unbound cells in the supernatant onto sorbitol MacConkey agar. Key parameters, including the amount of nanoparticles and immunoreaction time, were optimized with different concentrations of E. coli O157:H7 in phosphate-buffered saline. MNCs presented a minimum capture efficiency of 94% for E. coli O157:H7 ranging from 1.6 x 10(1) to 7.2 x 10(7) CFU/ml with an immunoreaction time of 15 min without any enrichment. Capture of E. coli O157:H7 by MNCs did not interfere with other bacteria, including Salmonella enteritidis, Citrobacter freundii, and Listeria monocytogenes. The capture efficiency values of MNCs increased from 69 to 94.5% as E. coli O157:H7 decreased from 3.4 x 10(7) to 8.0 x 10(0) CFU/ml in the ground beef samples prepared with minimal steps (without filtration and centrifugation). An enrichment of 6 h was done for 8.0 x 10(0) and 8.0 x 10(1) CFU/ml of E. coli O157:H7 in ground beef to increase the number of cells in the sample to a detectable level. The results also indicated that capture efficiencies of MNCs for E. coli O157:H7 with and without mechanical mixing during immunoreaction were not significantly different (P > 0.05). Compared with microbeads based immunomagnetic separation, the magnetic nanoparticles showed their advantages in terms of higher capture efficiency, no need for mechanical mixing, and minimal sample preparation.

Quantum dot biolabeling coupled with immunomagnetic separation for detection of Escherichia coli O157:H7.

A sensitive, specific, and rapid method for the detection of E. coli O157:H7 was demonstrated using quantum dots (QDs) as a fluorescence marker coupled with immunomagnetic separation. Magnetic beads coated with anti-E. coli O157 antibodies were employed to selectively capture the target bacteria, and biotin-conjugated anti-E. coli antibodies were added to form sandwich immuno complexes. After magnetic separation, the immuno complexes were labeled with QDs via biotin-streptavidin conjugation. This was followed by a fluorescence measurement using a laptop-controlled portable device, which consisted of a blue LED and a CCD-array spectrometer. The peak intensity of the fluorescence emission was proportional to the initial cell concentration of E. coli O157:H7 in the range of 10(3)-10(7) CFU/mL with a detection limit at least 100 times lower than that of the FITC-based method. The total detection time was less than 2 h. Neither E. coli K12 nor Salmonella typhimurium interfered with the detection of E. coli O157:H7.

A self-assembled monolayer-based piezoelectric immunosensor for rapid detection of Escherichia coli O157:H7.

A piezoelectric immunosensor was developed for rapid detection of Escherichia coli O157:H7. It was based on the immobilization of affinity-purified antibodies onto a monolayer of 16-mercaptohexadecanoic acid (MHDA), a long-chain carboxylic acid-terminating alkanethiol, self-assembled on an AT-cut quartz crystal's Au electrode surface with N-hydroxysuccinimide (NHS) ester as a reactive intermediate. The binding of target bacteria onto the immobilized antibodies decreased the sensor's resonant frequency, and the frequency shift was correlated to the bacterial concentration. The stepwise assembly of the immunosensor was characterized by means of both quartz crystal microbalance (QCM) and cyclic voltammetry techniques. Three analytical procedures, namely immersion, dip-and-dry and flow-through methods, were investigated. The immunosensor could detect the target bacteria in a range of 10(3)-10(8)CFU/ml within 30-50 min, and the sensor-to-sensor reproducibility obtained at 10(3) and 10(5) colony-forming units (CFU)/ml was 18 and 11% R.S.D., respectively. The proposed sensor was comparable to Protein A-based piezoelectric immunosensor in terms of the amount of immobilized antibodies and detection sensitivity.