A Grand Avenue to Au Nanocluster Electrochemiluminescence

In most cases of semiconductor quantum dot nanocrystals, the inherent optical and electrochemical properties of these interesting nanomaterials do not translate into expected efficient electrochemiluminescence or electrogenerated chemiluminescence (ECL) because of the surface-state induction effect. Thus, their low ECL efficiencies, while very interesting to explore, limit their applications. As their electrochemistry is not well-defined, insight into their ECL mechanistic details is also limited. Alternatively, gold nanoclusters possess monodispersed sizes with atomic precision, low and well defined HOMO-LUMO energy gaps, and stable optical and electrochemical properties that make them suitable for potential ECL applications. In this Account, we demonstrate strong and sustainable ECL of gold nanoclusters Au₂₅^z (i.e., Au₂₅(SR)₁₈^z, z = 1-, 0, 1+), Au₃₈(SR)₂₄, and Au₁₄₄(SR)₆₀, where the ligand SR is 2-phenylethanethiol. By correlation of the optical and electrochemical features of Au₂₅ nanoclusters, a Latimer-type diagram can be constructed to reveal thermodynamic relationships of five oxidation states (Au₂₅²⁺, Au₂₅⁺, Au₂₅⁰, Au₂₅^-, and Au₂₅^2-) and three excited states (Au₂₅^-*, Au₂₅⁰*, and Au₂₅⁺*). We describe ECL mechanisms and reaction kinetics by means of conventional ECL-voltage curves and novel spooling ECL spectroscopy. Notably, their ECL in the presence of tri-n-propylamine (TPrA), as a coreactant, is attributed to emissions from Au₂₅^-* (950 nm, strong), Au₂₅⁰* (890 nm, very strong), and Au₂₅⁺* (890 nm, very strong), as confirmed by the photoluminescence (PL) spectra of the three Au₂₅ clusters electrogenerated in situ. The ECL emissions are controllable by adjustment of the concentrations of TPrA· and Au₂₅^-, Au₂₅⁰, and Au₂₅⁺ species in the vicinity of the working electrode and ultimately the applied potential. It was determined that the Au₂₅^-/TPrA coreactant system should have an ECL efficiency of >50% relative to the Ru(bpy)₃²⁺/TPrA, while those of Au₂₅⁰/TPrA and Au₂₅⁺/TPrA reach 103% and 116%, respectively. Au₂₅^-* is the main light emission source for Au₂₅^z in the presence of benzoyl peroxide (BPO) as a coreactant, with a relative efficiency of up to 30%. For Au₃₈, BPO leads to the Au₃₈^-* excited state, which emits light at 930 nm. In the Au₃₈/TPrA coreactant system, we find that highly efficient light emission at 930 nm is mainly from Au₃₈⁺* (and also Au₃₈³⁺*), with an efficiency 3.5 times that of the Ru(bpy)₃²⁺/TPrA reference. We show that the ECL and PL of the various Au₃₈ charge states, namely, Au₃₈^2-, Au₃₈^-, Au₃₈⁰, Au₃₈⁺, Au₃₈²⁺, and Au₃₈⁴⁺, have the same peak wavelength of 930 nm. Finally, we demonstrate ECL with a peak wavelength of 930 nm from the Au₁₄₄/TPrA coreactant system, which is released from the electrogenerated excited states Au₁₄₄⁺* and Au₁₄₄³⁺*. In our opinion, these gold nanoclusters represent a new class of effective near-IR ECL emitters, from which applications such as bioimaging, biological testing, and medical diagnosis are anticipated once they are made water-dispersible with hydrophilic capping ligands.

Advanced electroanalytical chemistry at nanoelectrodes

Nanoelectrodes, with dimensions below 100 nm, have the advantages of high sensitivity and high spatial resolution. These electrodes have attracted increasing attention in various fields such as single cell analysis, single-molecule detection, single particle characterization and high-resolution imaging. The rapid growth of novel nanoelectrodes and nanoelectrochemical methods brings enormous new opportunities in the field. In this perspective, we discuss the challenges, advances, and opportunities for nanoelectrode fabrication, real-time characterizations and high-performance electrochemical instrumentation.

Image scanning fluorescence emission difference microscopy based on a detector array

We propose a novel imaging method that enables the enhancement of three-dimensional resolution of confocal microscopy significantly and achieve experimentally a new fluorescence emission difference method for the first time, based on the parallel detection with a detector array. Following the principles of photon reassignment in image scanning microscopy, images captured by the detector array were arranged. And by selecting appropriate reassign patterns, the imaging result with enhanced resolution can be achieved with the method of fluorescence emission difference. Two specific methods are proposed in this paper, showing that the difference between an image scanning microscopy image and a confocal image will achieve an improvement of transverse resolution by approximately 43% compared with that in confocal microscopy, and the axial resolution can also be enhanced by at least 22% experimentally and 35% theoretically. Moreover, the methods presented in this paper can improve the lateral resolution by around 10% than fluorescence emission difference and 15% than Airyscan. The mechanism of our methods is verified by numerical simulations and experimental results, and it has significant potential in biomedical applications.

Ubiquitination and regulation of AURKA identifies a hypoxia-independent E3 ligase activity of VHL

The hypoxia-regulated tumor-suppressor von Hippel-Lindau (VHL) is an E3 ligase that recognizes its substrates as part of an oxygen-dependent prolyl hydroxylase (PHD) reaction, with hypoxia-inducible factor α (HIFα) being its most notable substrate. Here we report that VHL has an equally important function distinct from its hypoxia-regulated activity. We find that Aurora kinase A (AURKA) is a novel, hypoxia-independent target for VHL ubiquitination. In contrast to its hypoxia-regulated activity, VHL mono-, rather than poly-ubiquitinates AURKA, in a PHD-independent reaction targeting AURKA for degradation in quiescent cells, where degradation of AURKA is required to maintain the primary cilium. Tumor-associated variants of VHL differentiate between these two functions, as a pathogenic VHL mutant that retains intrinsic ability to ubiquitinate HIFα is unable to ubiquitinate AURKA. Together, these data identify VHL as an E3 ligase with important cellular functions under both normoxic and hypoxic conditions.

Trends in Hydrophilicity/Lipophilicity of Phosphonium Ionic Liquids As Determined by Ion-Transfer Electrochemistry

Ionic liquids (ILs) have become valuable new materials for a broad spectrum of applications including additives or components for new hydrophobic/hydrophilic polymer coatings. However, fundamental information surrounding IL molecular properties is still lacking. With this in mind, the microinterface between two immiscible electrolytic solutions (micro-ITIES), for example, water|1,2-dichloroethane, has been used to evaluate the hydrophobicity/lipophilicity of 10 alkylphosphonium ILs. By varying the architecture around the phosphonium core, chemical differences were induced, changing the lipophilicity/hydrophilicity of the cations. Ion transfer (IT) within the polarizable potential window (PPW) was measured to establish a structure-property relationship. The Gibbs free energy of IT and the solubility of their ILs were also calculated. For phosphonium cations bearing either three butyl or three hydroxypropyl groups with a tunable fourth arm, the latter displayed a wide variety of easily characterizable IT potentials. The tributylphosphonium ILs, however, were too hydrophobic to undergo IT within the PPW. Utilizing a micro-ITIES (25 μm diameter) housed at the tip of a capillary in a uniquely designed pipet holder, we were able to probe beyond the traditional potential window and observe ion transfer of these hydrophobic phosphonium ILs for the first time. A similar trend in lipophilicity was determined between the two subsets of ILs by means of derived solubility product constants. The above results serve as evidence of the validation of this technique for the evaluation of hydrophobic cations that appear beyond the conventional PPW and of the lipophilicity of their ILs.

Identifying barriers to charge-carriers in the bulk and surface regions of Cu2ZnSnS4 nanocrystal films by x-ray absorption fine structures (XAFSs)

Solar cell performance is most affected by the quality of the light absorber layer. For thin-film devices, this becomes a two-fold problem of maintaining a low-cost design with well-ordered nanocrystal (NC) structure. The use of Cu₂ZnSnS₄ (CZTS) NCs as the light absorber films forms an ideal low-cost design, but the quaternary structure makes it difficult to maintain a well-ordered layer without the use of high-temperature treatments. There is little understanding of how CZTS NC structures affect the photoconversion efficiency, the charge-carriers, and therefore the performance of the device manufactured from it. To examine these relationships, the measured photoresponse from the photo-generation of charge-carrier electron-hole pairs was compared against the crystal structure, as short-range and long-range crystal orders for the films. The photoresponse simplifies the electronic properties into three basic steps that can be associated with changes in energy levels within the band structure. These changes result in the formation of barriers to charge-carrier flow. The extent of these barriers was determined using synchrotron-based X-ray absorbance fine structure to probe the individual metal centers in the film, and comparing these to molecular simulations of the ideal extended x-ray absorbance fine structure scattering. This allowed for the quantification of bond lengths, and thus an interpretation of the distortions in the crystal lattice. The various characteristics of the photoresponse were then correlated to the crystallographic order and used to gain physical insight into barriers to charge-carriers in the bulk and surface regions of CZTS films.

Punch biopsy guided by both colposcopy and HR-HPV status is more efficient for identification of immediate high-grade squamous intraepithelial lesion or worse among HPV-infected women with atypical squamous cells of undetermined significance

OBJECTIVES

To investigate the accuracy of colposcopy for diagnosing high-grade squamous intraepithelial lesion (HSIL) or worse (HSIL+) in human papillomavirus (HPV)-infected patients with atypical squamous cells of undetermined significance (ASCUS) cytology, and determine whether genotyping and viral load quantitation can be useful for detecting immediate HSIL+ risk in these patients.

STUDY DESIGN

This study included 620 cases with ASCUS and positive for high-risk (HR)-HPV within 1 month before or after cervical cytology at Qilu Hospital between February 2013 and February 2014. Based on the colposcopic impression, lesion-targeted punch biopsy, endocervical curettage biopsy or random cervical punch biopsy in four quadrants was performed on these patients within 1 month. The accuracy of colposcopy for diagnosing HSIL+ was evaluated through comparison with the biopsy results. HR-HPV status determined by Hybrid Capture 2 or HPV genotyping was analysed retrospectively as a possible predictor of HSIL+.

RESULTS

Agreement between colposcopic impression and cervical pathology was matched perfectly in 89.2% of cases (553/620), and the strength of agreement with the κ statistic was 0.698 (p<0.001). Colposcopy had high specificity (96.9%) but low sensitivity for detecting HSIL+ (67.5%). The risk of HSIL+ was significantly higher in patients with HPV-16 infection (52.3%) than in patients infected with other types of HPV (17.9%, p<0.001). HSIL+ and virus load was correlated at cut-offs (CO) of 50 relative light units (RLU)/CO and 100 RLU/CO (p=0.024 and 0.044, respectively). If considering HPV16 infection or high virus load (at 50 RLU/CO) as a diagnostic standard of HSIL+ when colposcopic impression was negative, sensitivity was improved to 74.7% and 81.0%, respectively.

CONCLUSIONS

Good agreement was found between colposcopic and pathologic diagnosis. HR-HPV genotyping or virus load is relevant to the detection of HSIL+ among HPV-infected patients with ASCUS cytology. In these patients, biopsies considering HPV-16 infection or virus load ≥50 RLU/CO may be helpful for increasing the HSIL+ detection rate.

Elevational pattern of bird species richness and its causes along a central Himalaya gradient, China

This study examines the relative importance of six variables: area, the mid-domain effect, temperature, precipitation, productivity, and habitat heterogeneity on elevational patterns of species richness for breeding birds along a central Himalaya gradient in the Gyirong Valley, the longest of five canyons in the Mount Qomolangma National Nature Reserve. We conducted field surveys in each of twelve elevational bands of 300 m between 1,800 and 5,400 m asl four times throughout the entire wet season. A total of 169 breeding bird species were recorded and most of the species (74%) were small-ranged. The species richness patterns of overall, large-ranged and small-ranged birds were all hump-shaped, but with peaks at different elevations. Large-ranged species and small-ranged species contributed equally to the overall richness pattern. Based on the bivariate and multiple regression analyses, area and precipitation were not crucial factors in determining the species richness along this gradient. The mid-domain effect played an important role in shaping the richness pattern of large-ranged species. Temperature was negatively correlated with overall and large-ranged species but positively correlated with small-ranged species. Productivity was a strong explanatory factor among all the bird groups, and habitat heterogeneity played an important role in shaping the elevational richness patterns of overall and small-ranged species. Our results highlight the need to conserve primary forest and intact habitat in this area. Furthermore, we need to increase conservation efforts in this montane biodiversity hotspot in light of increasing anthropogenic activities and land use pressure.

First case of hepatopancreatic necrosis disease in pond-reared Chinese mitten crab, Eriocheir sinensis, associated with microsporidian

An epidemic of hepatopancreatic necrosis disease (HPND) with a high mortality rate (40%-50%) recently occurred in the cultured Chinese mitten crab, Eriocheir sinensis, which is a very important economic crustacean species in China. Histology revealed infection by a microsporidian parasite within the cytoplasm of the epithelial cells of the hepatopancreas. Numerous discrete inclusions in the infected cells and presumably free parasite spores were also observed. By negative staining using electron microscopy, a typical morphology of spores was observed with a protuberant front of the anchoring disc. Infection was confined to the epithelial cells of the hepatopancreas, with no other organ implicated. By sequencing the PCR products using specific primers based on conserved regions of microsporidian small subunit (18S) ribosomal DNA, it was revealed that the parasite from HPND ponds had 99% sequence identity to that of Hepatospora eriocheir. Phylogentic analysis also placed the microsporidian in the same lineage as H. eriocheir. This study reported the first case of widespread infections of H. eriocheir associated with HPND found in the pond-reared Chinese mitten crab, E. sinensis. The description of microsporidian in this important commercial host is fundamental for future consideration of factors affecting stock health and sustainability.

Phosphorylation-dependent cleavage regulates von Hippel Lindau proteostasis and function

Loss of von Hippel Lindau (VHL) protein function is a key driver of VHL diseases, including sporadic and inherited clear cell renal cell carcinoma. Modulation of the proteostasis of VHL, especially missense point-mutated VHL, is a promising approach to augmenting VHL levels and function. VHL proteostasis is regulated by multiple mechanisms including folding, chaperone binding, complex formation and phosphorylation. Nevertheless, many details underlying the regulations of VHL proteostasis are unknown. VHL is expressed as two variants, VHL30 and VHL19. Furthermore, the long-form variant of VHL was often detected as multiple bands by western blotting. However, how these multiple species of VHL are generated and whether the process regulates VHL proteostasis and function are unknown. We hypothesized that the two major species are generated by VHL protein cleavage, and the cleavage regulates VHL proteostasis and subsequent function. We characterized VHL species using genetical and pharmacological approaches and showed that VHL was first cleaved at the N-terminus by chymotrypsin C before being directed for proteasomal degradation. Casein kinase 2-mediated phosphorylation at VHL N-terminus was required for the cleavage. Furthermore, inhibition of cleavage stabilized VHL protein and thereby promoted HIF downregulation. Our study reveals a novel mechanism regulating VHL proteostasis and function, which is significant for identifying new drug targets and developing new therapeutic approaches targeting VHL deficiency in VHL diseases.

Sensing cisplatin-induced permeation of single live human bladder cancer cells by scanning electrochemical microscopy

Cisplatin is a widely used anti-cancer agent, which was believed to trigger apoptosis of cancer cells by forming DNA adducts. However, recent studies evidenced a cisplatin-induced extrinsic apoptotic pathway through interaction with plasma membranes. We present quantitative time-course imaging of cisplatin-induced permeation of ferrocenemethanol to single live human bladder cancer cells (T24) using scanning electrochemical microscopy (SECM). Simultaneous quantification of cellular topography and membrane permeability was realized by running SECM in the depth scan mode. It was demonstrated that the acute addition of cisplatin to the outer environment of T24 cells immediately induced membrane permeability change in 5 min, which indicated a loosened structure of the cellular membrane upon cisplatin dosage. The cisplatin-induced permeation of T24 cells might be a one-step action, an extrinsic mechanism, since the cell response was quick, and no continuous increase in the membrane permeability was observed. The time-lapse SECM depth scan method provided a simple and facile way of monitoring cisplatin-induced membrane permeability changes. Our study is anticipated to lead to a methodology of screening anti-cancer drugs through their interactions with live cells.

Association between high visceral fat area and postoperative complications in patients with Crohn's disease following primary surgery

AIM

The aim of this study was to determine the association between visceral fat area (VFA) on CT and postoperative complications after primary surgery in patients with Crohn's disease (CD).

METHOD

Inclusion criteria were patients with a confirmed diagnosis of CD who had preoperative abdominal CT scan. The areas of total fat, subcutaneous fat and visceral fat were measured using an established image-analysis method at the lumbar 3 (L3) level on CT cross-sectional images. Visceral obesity was defined as a visceral fat area (VFA) of ≥ 130 cm(2) . Clinical variables, intra-operative outcomes and postoperative courses within 30 days were analysed.

RESULTS

A total of 164 patients met the inclusion criteria. Sixty-three (38.4%) patients had postoperative complications. The mean age of the patients with complications (the study group) was 40.4 ± 15.4 years and of those without complications (the control group) was 35.8 ± 12.9 years (P = 0.049). There were no differences in disease location and behaviour between patients with or without complications (P > 0.05). In multivariable analysis, VFA [odds ratio (OR) = 2.69; 95% confidence interval (CI): 1.09-6.62; P = 0.032] and corticosteroid use (OR = 2.86; 95% CI: 1.32-6.21; P = 0.008) were found to be associated with postoperative complications. Patients with visceral obesity had a significantly longer operative time (P = 0.012), more blood loss (P = 0.019), longer bowel resection length (P = 0.003), postoperative ileus (P = 0.039) and a greater number of complications overall (P < 0.001).

CONCLUSION

High VFA was found to be associated with an increased risk for 30-day postoperative complications in patients with CD undergoing primary surgery.