Ultrafast Hole/Electron Transfer Dynamics in a CdSe Quantum Dot Sensitized by Pyrogallol Red: A Super-Sensitization System

To find a suitable hole-transporting adsorbate for CdSe quantum dots (QDs), a pyrogallol red (PGR) molecule was chosen where PGR also can sensitize CdSe QDs. Energy level diagrams suggest that the photoexcited hole can be transferred to PGR and photoexcited PGR can inject an electron into CdSe QDs. Steady-state and time-resolved emission studies suggest that the photoexcited hole is transferred to PGR; however, the process is too fast to monitor with the subnanosecond time-resolution spectroscopic technique. Femtosecond transient absorption spectroscopy has been employed to monitor the charge-transfer behavior of the above system in an early time scale. Photoexcitation of pure PGR and CdSe QDs at 400 nm laser light gives the transient absorption due to the photoexcited singlet state of PGR and charge carriers (electron/hole) in CdSe QDs, respectively, in the visible/near-IR region of the absorption spectra. However, on photoexcitation of the CdSe/PGR composite at 400 nm, the PGR cation radical and electron in the CdSe QD were detected in the transient absorption spectra. Hole transfer time from the photoexcited CdSe QD to PGR is found to be 500 fs. The transient signal due to the PGR cation and electron in the CdSe QD also contributed to photoexcitation of PGR on the CdSe QD, where electron injection is found to be <150 fs. Charge recombination dynamics were found to be very slow with time constants of 4 ps (15%) and >200 ps (85%) confirming a grand charge-separated state in the CdSe/PGR composite system

Green, Water-Dispersible Photoluminescent On–Off–On Probe for Selective Detection of Fluoride Ions

Considering the high toxicity and widespread availability of fluoride ions in different environmental matrices, it is imperative to design a probe for its detection. In view of this, a selective fluorescent on–off–on probe based on carbon quantum dots (CQDs) and Eu³⁺ has been designed. We have synthesized water-soluble carboxylic acid-functionalized CQDs and monitored their interaction with Eu³⁺. Luminescence quenching in the CQD emission was observed (switch-off) on adding Eu³⁺ ions. We investigate the reason for this luminescence quenching using time-resolved emission and high-resolution transmission electron microscopy (HRTEM) studies and observed that both electron transfer from CQDs to Eu³⁺ and aggregation of CQDs are responsible for the luminescence quenching. ζ-Potential and X-ray photoelectron spectroscopy studies confirm Eu³⁺ binding with the COOH groups on CQD surface. Interestingly, luminescence regains after the addition of fluoride ions to the CQDs/Eu³⁺ system (switch-on). This has been assigned to the removal of Eu³⁺ from the CQD surface due to the formation of EuF₃ and is confirmed by X-ray diffraction and HRTEM measurements. The sensitivity of the probe was tested by carrying out experiments with other competing ions and was found to be selective for fluoride ions. Experiments with variable concentrations of fluoride ions suggest that the working range of the probe is 1–25 ppm. The probe has been successfully tested for the detection of fluoride ions in a toothpaste sample and the results were compared to those of ion chromatography. To the best of our knowledge, this is the first report based on CQDs and Eu³⁺ for the detection of fluoride ions, wherein a clear mechanism of the detection has been demonstrated, which, in turn, will help to develop better detection methods. The suggested probe is green, economical, rapid, efficient, and, most importantly, selective and can be used for the detection of fluoride ions in real environmental samples

Clinical Impact of De-Regulated Notch-1 and Notch-3 in the Development and Progression of HPV-Associated Different Histological Subtypes of Precancerous and Cancerous Lesions of Human Uterine Cervix

<div><p>Background</p><p>Cervical cancer is the leading cause of cancer related deaths among women in India. Limited reports are available for Notch-1 and Notch-3 protein in cervical carcinoma, which play crucial role in cell proliferation, differentiation, and apoptosis.</p><p>Methods</p><p>This study was designed to evaluate the role of Notch-1 and Notch-3 with context to HPV infection in cervical carcinoma. A total of 168 tissue biopsy samples comprising of tumor specimens (n = 98), precancer (n = 30) and non-neoplastic cervical tissues (n = 40) were screened for HPV infection by PCR and expression of Notch-1 and Notch-3 protein by Immunohistochemistry and Immunoblotting.</p><p>Results</p><p>80% (24/30) were found to be positive for HPV in precancer and 86.7% (85/98) in cancer patients. Notch-1 expression of precancer and cancer cases was found to be significantly down-regulated with severity of disease in nuclear (3.43±0.29; 2.04±0.19, p = 0.0001, p = 0.0001) and cytoplasm (3.07±0.29; 2.29±0.17, p = 0.0001, p = 0.0001) obtained from different stages as compared to normal cervix tissue (5.40±0.19, 4.97±0.15; p<0.001; p<0.001). However, Notch-3 expression of above cases was significantly up-regulated with severity of disease and showed intense nuclear (4.17±0.39; 4.74±0.18, p = 0.0001, p = 0.0001) and cytoplasm (3.67±0.36; 4.48±0.18, p = 0.0001, p = 0.0001) of different stages as compared to normal cervix tissue (0.95±0.20, 0.70±0.20; p<0.001; p<0.001) respectively.</p><p>Conclusions</p><p>These findings suggest that Notch-1 and Notch-3 may play an important role with synergistic effect of HPV in regulating development and proliferation of cervical cancer through the deregulation of Notch signalling. This study also shows the clinical utility of both proteins which may be used as predictable biomarkers in diagnosing different histological sub-types of HPV associated cervical cancer. Nevertheless, abnormal activation of this pathway may provide legitimate targets for cervical cancer therapy.</p></div

Total score (Intensity score + Percentage positivity, Mean ± S.E) of Notch-1 and Notch-3 expression in normal, precancerous and cancer tissues.

<p>p-values are calculated using the chi-square test.</p><p>* p≤0.05 was considered significant.</p>▾<p>Downregulation;^▴Upregulation.</p

Analysis of Notch-3 protein expression in ISCC and its correlation with demographic and clinico-pathological parameters.

<p>*p≤0.05 is considered as significant.</p

Correlation of HPV infection with Notch-3 protein expression in precancer.

<p>*p≤0.05 is considered as significant.</p

Detection of Human Papilloma virus genotypes 16 and 18 in precancer & cervical cancer patients by In vitro nucleic acid amplification test.

<p>(<b>A</b>) β-globin, 288bp (<b>B</b>) HPV-L1, 450bp (<b>C</b>) HPV-16, 217bp (<b>D</b>) HPV-18, 100bp as indicated in Materials and Methods section.</p

Correlation of HPV infection with Notch-1 protein expression in ISCC.

<p>*p≤0.05 is considered as significant.</p

Correlation of HPV infection with Notch-3 protein expression in ISCC.

<p>*p≤0.05 is considered as significant.</p

Immuno-histochemical analysis of Notch-1 and Notch-3 showing expression pattern of Notch-1 and Notch-3 in normal, precancerous and cancer tissues of uterine cervix.

<p>(<b>A</b>) Negative control of Notch-1 in normal tissue, 200X. (<b>B</b>) Intense nuclear, cytoplasmic expression and loss of membranous expression of Notch-1 in normal cervix, 200X. (<b>C</b>) Moderate nuclear expression of Notch-1 in precancrous tissue, 200X. (<b>D</b>) Negative control (ISCC, 200X). (<b>E</b>) Mild cytoplasmic localization and loss of nuclear Notch-1 in ISCC, 200X. (<b>F</b>) Membranous positive and loss of nuclear expression of Notch-1 in ISCC, 400X. (<b>G</b>) Negative control of Notch-3, 200X. (<b>H</b>) Cytoplasmic localization and loss of nuclear Notch-3 in normal cervix, 200X. (<b>I</b>) Cytoplasmic and nuclear localization of Notch-3 in precancer, 200X. (<b>J</b>) Negative control of Notch-3 (ISCC, 200X). (<b>K</b>) Cytoplasmic and Nuclear localization And loss of membranous Notch-3 in ISCC, 200X as indicated in Materials and Methods section. (<b>L</b>, <b>M</b>) Bar graph showing distribution of total scores of Notch-1 and Notch-3 protein in Normal cervix, Precancer and Invasive squamous cervical carcinoma (ISCC) tissues. The vertical axis shows the total Immunostaining score (cytoplasmic or nuclear respectively), obtained as described in the Methods section. (<b>N</b>) Western blots showing expression pattern of Notch-1 and Notch-3 protein during the progression of cervical cancer. Protein extracts from cervical tumor biopsies as well as normal tissues were separated in 10% SDS-PAGE and detected by specific antibodies of Notch-1 and Notch-3 protein. All the blots were stripped and reprobed for β-actin levels to confirm equal loading and the quantitation of bands was performed densitometrically as indicated in Materials and Methods section.</p