Electrodeposition of hierarchical ZnO nanorod-nanosheet structures and their applications in dye-sensitized solar cells

We present a two-step electrochemical deposition process to synthesize hierarchical zinc oxide (ZnO) nanorod-nanosheet structures on indium tin oxide (ITO) substrate, which involves electrodeposition of ZnO nanosheet arrays on the conductive glass substrate, followed by electrochemical growth of secondary ZnO nanorods on the backbone of the primary ZnO nanosheets. The formation mechanism of the hierarchical nanostructure is discussed. It is demonstrated that annealing treatment of the primary nanosheets synthesized by the first-step deposition process plays a key role in synthesizing the hierarchical nanostructure. Photovoltaic properties of dye-sensitized solar cells (DSSCs) based on hierarchical ZnO nanostructures are investigated. The hierarchical ZnO nanorod-nanosheet DSSC exhibits improved device performance compared to the DSSC constructed using photoelectrode of bare ZnO nanosheet arrays. The improvement can be attributed to the enhanced dye loading, which is caused by the enlargement of internal surface area within the nanostructure photoelectrode. Furthermore, we perform a parametric study to determine the optimum geometric dimensions of the hierarchical ZnO nanorod-nanosheet photoelectrode through adjusting the preparation conditions of the first- and second-step deposition process. By utilizing a hierarchical nanostructure photoelectrode with film thickness of about 7 μm, the DSSC with an open-circuit voltage of 0.74 V and an overall power conversion efficiency of 3.12% is successfully obtained.

Impact of luteolin on the production of alpha-toxin by Staphylococcus aureus

AIMS

To investigate the influence of subinhibitory concentrations of luteolin on the production of α-toxin in Staphylococcus aureus.

METHODS AND RESULTS

The minimal inhibitory concentrations (MICs) were determined using a broth microdilution method, and the MICs of luteolin against the tested Staph. aureus strains ranged from 16 to 64 μg ml(-1). Haemolysis, Western blot and real-time reverse transcription (RT)-PCR assays were used to evaluate the effect of luteolin on Staph. aureusα-toxin secretion and on the level of gene expression, respectively. The data indicated that subinhibitory concentrations of luteolin dose dependently decreased the production of α-toxin in both meticillin-sensitive Staph. aureus (MSSA) and meticillin-resistant Staph. aureus (MRSA). Furthermore, the transcriptional levels of agr (accessory gene regulator) in Staph. aureus were also inhibited by luteolin.

CONCLUSIONS

Luteolin decreases the production and/or secretion of α-toxin in Staph. aureus; the reduced production may be dependent, in part, upon the luteolin-induced inhibition of the agr locus.

SIGNIFICANCE AND IMPACT OF THE STUDY

The findings indicate that luteolin may be used as a basis for the development of antimicrobial agents aimed at bacterial virulence factors.

Density-controlled electrodeposition growth of zinc oxide nanorod arrays

Density-controlled zinc oxide (ZnO) nanorod arrays were synthesized on indium tin oxide (ITO) substrates via a potentiostatic electrodeposition method under different conditions. The effects of preparing conditions on the density of nanorods were systematically investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). It is demonstrated that the density and diameter of ZnO nanorods can be effectively controlled by varying the electrodeposition parameters, such as electrodeposition potential, concentration of Zn2+ precursor and growth temperature. Pre-treatment of the substrate also has great influence on the morphology of the electrodeposited ZnO nanorods. By coating the ITO substrates with an gold (Au) or ZnO nanoparticle seed layer, ZnO nanorod arrays with an average diameter of about 50 nm were synthesized, and the nanorod density can be controlled to above 50 x 10(8) rod cm(-2), which is several dozen times greater than that of the ZnO nanorod arrays synthesized on original ITO substrates.

Hypothalamic transcriptome plasticity in two rodent species reveals divergent differential gene expression but conserved pathways

We have addressed the question of how different rodent species cope with the life-threatening homeostatic challenge of dehydration at the level of transcriptome modulation in the supraoptic nucleus (SON), a specialised hypothalamic neurosecretory apparatus responsible for the production of the antidiuretic peptide hormone arginine vasopressin (AVP). AVP maintains water balance by promoting water conservation at the level of the kidney. Dehydration evokes a massive increase in the regulated release of AVP from SON axon terminals located in the posterior pituitary, and this is accompanied by a plethora of changes in the morphology, electrophysiological properties, biosynthetic and secretory activity of this structure. Microarray analysis was used to generate a definitive catalogue of the genes expressed in the mouse SON, and to describe how the gene expression profile changes in response to dehydration. Comparison of the genes differentially expressed in the mouse SON as a consequence of dehydration with those of the rat has revealed many similarities, pointing to common processes underlying the function-related plasticity in this nucleus. In addition, we have identified many genes that are differentially expressed in a species-specific manner. However, in many cases, we have found that the hyperosmotic cue can induce species-specific alterations in the expression of different genes in the same pathway. The same functional end can be served by different means, via differential modulation, in different species, of different molecules in the same pathway. We suggest that pathways, rather than specific genes, should be the focus of integrative physiological studies based on transcriptome data.

The effects of subinhibitory concentrations of costus oil on virulence factor production in Staphylococcus aureus

AIM

To determine the antimicrobial activity of costus (Saussurea lappa) oil against Staphylococcus aureus, and to evaluate the influence of subinhibitory concentrations of costus oil on virulence-related exoprotein production in staph. aureus.

METHODS AND RESULTS

Minimal inhibitory concentrations (MICs) were determined using a broth microdilution method, and the MICs of costus oil against 32 Staph. aureus strains ranged from 0.15 to 0.6 μl ml(-1) . The MIC(50) and MIC(90) were 0.3 and 0.6 μl ml(-1) , respectively. Western blot, haemolytic, tumour necrosis factor (TNF) release and real-time RT-PCR assays were performed to evaluate the effects of subinhibitory concentrations of costus oil on virulence-associated exoprotein production in Staph. aureus. The data presented here show that costus oil dose dependently decreased the production of α-toxin, toxic shock syndrome toxin 1 (TSST-1) and enterotoxins A and B in both methicillin-sensitive Staph. aureus (MSSA) and methicillin-resistant Staph. aureus (MRSA).

CONCLUSION

Costus oil has potent antimicrobial activity against Staph. aureus, and the production of α-toxin, TSST-1 and enterotoxins A and B in Staph. aureus was decreased by costus oil.

SIGNIFICANCE AND IMPACT OF THE STUDY

The data suggest that costus oil may deserve further investigation for its potential therapeutic value in treating Staph. aureus infections. Furthermore, costus oil could be rationally applied in food products as a novel food preservative both to inhibit the growth of Staph. aureus and to repress the production of exotoxins, particularly staphylococcal enterotoxins.

Meta-analysis: polymorphisms in TNF-alpha gene promoter and Crohn's disease

BACKGROUND

Tumour necrosis factor alpha (TNF-alpha) is involved in the pathogenesis of Crohn's disease (CD). However, results on the association between the polymorphisms in TNF-alpha promoter and the risk of CD are inconsistent.

AIM

To perform a quantitative synthesis for the genetic polymorphisms in TNF-alpha promoter and CD risk.

METHODS

Databases were searched (up to 2009) and 31 studies were included. Risks of CD associated with the polymorphisms in TNF-alpha promoter were assessed.

RESULTS

Overall, individuals with -1031 TC+CC genotype had a slightly increased risk to develop CD compared with individuals with -1031 TT genotype (OR, 1.32; 95% CI, 1.03-1.70). In the further stratified analysis, we found Asians with the -1031T>C, -863 C>A and -857 C>T variant polymorphisms have almost one and a half CD risk compared with other genotypes (OR, 1.58; 95% CI, 1.16-2.15; OR, 1.55; 95% CI, 1.18-2.02; OR, 1.54; 95% CI, 1.19-1.99 respectively). We did not find -308 G>A variant associated with CD location and disease behaviours in stratified analysis.

CONCLUSIONS

TNF-alpha polymorphisms in the promoter region might be used as a biomarker for CD risk prediction. Larger studies with mixed ethnicity subjects and stratified by clinical and sub clinical characteristics are needed to validate our findings.

Persistent expression of biologically active anti-HER2 antibody by AAVrh.10-mediated gene transfer

Trastuzumab (Herceptin) is a recombinant humanized monoclonal antibody directed against an extracellular region of the HER2 protein. We hypothesized that a single adeno-associated virus mediated genetic delivery of an anti-HER2 antibody should be effective in mediating long term production of anti-HER2 and in suppressing the growth of human tumors in a xenograft model in nude mice. The adeno-associated virus gene transfer vector AAVrh.10αHER2 was constructed based on non-human primate AAV serotype rh.10 to express the cDNAs for the heavy and light chains of monoclonal antibody 4D5, the murine precursor to trastuzumab. The data demonstrates that genetically transferred anti-HER2 selectively bound human HER2 protein and suppressed proliferation of HER2 positive tumor cell lines. A single administration of AAVrh.10αHER2 provided long term therapeutic levels of anti-HER2 antibody expression without inducing anti-idiotype response, suppressed the growth of HER2 positive tumors and increased survival of the tumor-bearing mice. In the context that trastuzumab therapy requires frequent, repeated administration, this strategy might be developed as an alternate platform for delivery anti-HER2 therapy.

Quantitation of thyroid-stimulating hormone receptor mRNA with real-time PCR for early diagnosis of papillary thyroid microcarcinoma

Recently, the value of thyroid-stimulating hormone receptor(TSHR) mRNA as a molecular marker in diagnosis of thyroid cancer has been greatly explored. However, its role in detecting thyroid microcarcinoma has never been reported. In this study, we aim to investigate the value of TSHR mRNA in diagnosis of papillary thyroid microcarcinoma(PTMC). To do that, TSHR mRNA levels were measured by real time PCR in 30 healthy subjects and 72 patients (benign thyroid nodules, n=38; PTMC, n=34). TSHR mRNA levels were then compared with cancer volume in surgical specimen. We found that TSHR mRNA levels in PTMC were significantly higher than benign thyroid nodules(P<0.01). At a cutoff value of 0.71 ng/microg total RNA, the TSHR mRNA correctly classified 77.8% of patients preoperatively (sensitivity= 76.5%; specificity= 79.4%). Comparatively, it performed better in larger PTMC of 0.5-1.0 cm than <0.5 cm(sensitivity, 83.4% vs 72.4%; specificity, 88.5% vs 74.1%). Combining TSHR mRNA and ultra sound examination correctly detect 97.1% of PTMC and could spared surgery in 86.8% of patients with benign thyroid nodules. Thus, TSHR mRNA measured with real time PCR enhances the preoperative detection of PTMC in patients with thyroid nodules, which dramatically reduces unnecessary surgeries.

KEYWORDS

thyroid-stimulating hormone receptor, papillary thyroid microcarcinoma, diagnosis.