Electron transport through supercrystals of atomically precise gold nanoclusters: a thermal bi-stability effect

Nanoparticles (NPs) may behave like atoms or molecules in the self-assembly into artificial solids with stimuli-responsive properties. However, the functionality engineering of nanoparticle-assembled solids is still far behind the aesthetic approaches for molecules, with a major problem arising from the lack of atomic-precision in the NPs, which leads to incoherence in superlattices. Here we exploit coherent superlattices (or supercrystals) that are assembled from atomically precise Au103S2(SR)41 NPs (core dia. = 1.6 nm, SR = thiolate) for controlling the charge transport properties with atomic-level structural insights. The resolved interparticle ligand packing in Au103S2(SR)41-assembled solids reveals the mechanism behind the thermally-induced sharp transition in charge transport through the macroscopic crystal. Specifically, the response to temperature induces the conformational change to the R groups of surface ligands, as revealed by variable temperature X-ray crystallography with atomic resolution. Overall, this approach leads to an atomic-level correlation between the interparticle structure and a bi-stability functionality of self-assembled supercrystals, and the strategy may enable control over such materials with other novel functionalities.

Understanding the Nascent Plasmons and Metallic Bonding in Atomically Precise Gold Nanoclusters

The metallic bond is arguably the most intriguing one among the three types of chemical bonds, and the resultant plasmon excitation (e.g. in gold nanoparticles) has garnered wide interest. Recent...

Double-helical assembly of heterodimeric nanoclusters into supercrystals

DNA has long been used as a template for the construction of helical assemblies of inorganic nanoparticles^1-5. For example, gold nanoparticles decorated with DNA (or with peptides) can create helical assemblies^6-9. But without such biological ligands, helices are difficult to achieve and their mechanism of formation is challenging to understand^10,11. Atomically precise nanoclusters that are protected by ligands such as thiolate^12,13 have demonstrated hierarchical structural complexity in their assembly at the interparticle and intraparticle levels, similar to biomolecules and their assemblies¹⁴. Furthermore, carrier dynamics can be controlled by engineering the structure of the nanoclusters¹⁵. But these nanoclusters usually have isotropic structures^16,17 and often assemble into commonly found supercrystals¹⁸. Here we report the synthesis of homodimeric and heterodimeric gold nanoclusters and their self-assembly into superstructures. While the homodimeric nanoclusters form layer-by-layer superstructures, the heterodimeric nanoclusters self-assemble into double- and quadruple-helical superstructures. These complex arrangements are the result of two different motif pairs, one pair per monomer, where each motif bonds with its paired motif on a neighbouring heterodimer. This motif pairing is reminiscent of the paired interactions of nucleobases in DNA helices. Meanwhile, the surrounding ligands on the clusters show doubly or triply paired steric interactions. The helical assembly is driven by van der Waals interactions through particle rotation and conformational matching. Furthermore, the heterodimeric clusters have a carrier lifetime that is roughly 65 times longer than that of the homodimeric clusters. Our findings suggest new approaches for increasing complexity in the structural design and engineering of precision in supercrystals.

Inhomogeneous Quantized Single-Electron Charging and Electrochemical-Optical Insights on Transition-Sized Atomically Precise Gold Nanoclusters

Small differences in electronic structures, such as an emerging energy band gaps or the splitting of degenerated orbitals, are very challenging to resolve but important for nanomaterials properties. A signature electrochemical property called quantized double layer charging, i.e., "continuous" one-electron transfers (1e, ETs), in atomically precise Au₁₃₃(TBBT)₅₂, Au₁₄₄(BM)₆₀, and Au₂₇₉(TBBT)₈₄ is analyzed to reveal the nonmetallic to metallic transitions (whereas TBBT is 4-tert-butylbenzenethiol and BM is benzyl mercaptan; abbreviated as Au₁₃₃, Au₁₄₄, and Au₂₇₉). Subhundred milli-eV energy differences are resolved among the "often-approximated uniform" peak spacings from multipairs of reversible redox peaks in voltammetric analysis, with single ETs as internal standards for calibration and under temperature variations. Cyclic and differential pulse voltammetry experiments reveal a 0.15 eV energy gap for Au₁₃₃ and a 0.17 eV gap for Au₁₄₄ at 298 K. Au₂₇₉ is confirmed metallic, displaying a "bulk-continuum" charging response without an energy gap. The energy gaps and double layer capacitances of Au₁₃₃ and Au₁₄₄ increase as the temperature decreases. The temperature dependences of charging energies and HOMO-LUMO gaps of Au₁₃₃ and Au₁₄₄ are attributed to the counterion permeation and the steric hindrance of ligand, as well as their molecular compositions. With the subtle energy differences resolved, spectroelectrochemistry features of Au₁₃₃ and Au₁₄₄ are compared with ultrafast spectroscopy to demonstrate a generalizable analysis approach to correlate steady-state and transient energy diagram for the energy-in processes. Electrochemiluminescence (ECL), one of the energy-out processes after the charge transfer reactions, is reported for the three samples. The ECL intensity of Au₂₇₉ is negligible, whereas the ECLs of Au₁₃₃ and Au₁₄₄ are relatively stronger and observable (but orders of magnitudes weaker than our recently reported bimetallic Au₁₂Ag₁₃). Results from these atomically precise nanoclusters also demonstrate that the combined voltammetric and spectroscopic analyses, together with temperature variations, are powerful tools to reveal subtle differences and gain insights otherwise inaccessible in other nanomaterials.

Chirality and Surface Bonding Correlation in Atomically Precise Metal Nanoclusters

Chirality is ubiquitous in nature and occurs at all length scales. The development of applications for chiral nanostructures is rising rapidly. With the recent achievements of atomically precise nanochemistry, total structures of ligand-protected Au and other metal nanoclusters (NCs) are successfully obtained, and the origins of chirality are discovered to be associated with different parts of the cluster, including the surface ligands (e.g., swirl patterns), the organic-inorganic interface (e.g., helical stripes), and the kernel. Herein, a unified picture of metal-ligand surface bonding-induced chirality for the nanoclusters is proposed. The different bonding modes of M-X (where M = metal and X = the binding atom of ligand) lead to different surface structures on nanoclusters, which in turn give rise to various characteristic features of chirality. A comparison of Au-thiolate NCs with Au-phosphine ones further reveals the important roles of surface bonding. Compared to the Au-thiolate NCs, the Ag/Cu/Cd-thiolate systems exhibit different coordination modes between the metal and the thiolate. Other than thiolate and phosphine ligands, alkynyls are also briefly discussed. Several methods of obtaining chiroptically active nanoclusters are introduced, such as enantioseparation by high-performance liquid chromatography and enantioselective synthesis. Future perspectives on chiral NCs are also proposed.

Fusion growth patterns in atomically precise metal nanoclusters

Atomically precise nanoclusters of coinage metals in the 1-3 nm size regime have been intensively pursued in recent years. Such nanoclusters are attractive as they fill the gap between small molecules (<1 nm) and regular nanoparticles (>3 nm). This intermediate identity endows nanoclusters with unique physicochemical properties and provides nanochemists opportunities to understand the fundamental science of nanomaterials. Metal nanoparticles are well known to exhibit plasmon resonances upon interaction with light; however, when the particle size is downscaled to the nanocluster regime, the plasmons fade out and step-like absorption spectra characteristic of cluster sizes are manifested due to strong quantum confinement effects. Recent research has revealed that nanoclusters are commonly composed of a distinctive kernel and a surface-protecting shell (or staple-like metal-ligand motifs). Understanding the kernel configuration and evolution is one of the central topics in nanoscience research. This Review summarizes the recent progress in identifying the growth patterns of atomically precise coinage nanoclusters. Several basic kernel units have been observed, such as the M₄, M₁₃ and M₁₄ polyhedrons (where, M = metal atom). Among them, the tetrahedral M₄ and icosahedral M₁₃ units are the most common ones, which are adopted as building blocks to construct larger kernel structures via various fusion or aggregation modes, including the vertex- and face-sharing mode, the double-strand and alternate single-strand growth, and cyclic fusion of units, as well as the fcc-based cubic growth pattern. The identification of the kernel growth pathways has led to deeper understanding of the evolution of electronic structure and optic properties.

P4760New minimally invasive and tailor-made strategy for cryoballoon ablation in patients with paroxysmal atrial fibrillation

Background

Currently, cryoballoon ablation (CBA) has proven to be highly effective in achieving free from atrial fibrillation (AF), especially paroxysmal AF. However, the optimal freezing protocol for each patient to achieve successful pulmonary vein isolation by only CBA is still uncertain. The aim of this study was to evaluate the clinical implications of a reduction in the freezing duration (<180s) during CBA guided by the time to target temperature.

Methods

From November 2015 to August 2018, 286 consecutive paroxysmal AF patients undergoing CBA were enrolled. We compared 107 patients undergoing a tailor-made CBA procedure (Group A; August 2017-August 2018) to 179 patients with a standard CBA procedure (Group B; November 2015–July 2017). In Group A, the freezing duration was reduced to 150s when the temperature reached ≤−40°C within 40s. Furthermore, we reduced it to 120s when it reached ≤−50°C within 60s. In the other patients, the freezing time was 180s except for excessive freezing over −60°C and/or emergent situations while monitoring the esophageal temperature and for phrenic nerve injury as in Group B.

Results

The baseline clinical characteristics were similar between two groups. In Group A, 89 patients (83%) underwent CBA with a reduction in the freezing time. The rate of having reduction time in left inferior PV (LIPV) and right inferior PV (RIPV) was lower compared with left superior PV (LSPV) and right superior PV (RSPV) (respectively 17%, 29%, 56%, and 63.5%). However, for right inferior PV, in 31 patients having the reduced freezing time, none of them required touch-up ablation. Although the procedure time and frequency of touch-up ablation did not differ between the 2 groups, total freezing time for each PV was significantly shorter in Group A than Group B as shown in figure (LSPV: 164±28s vs. 216±67s; p<0.001, LIPV: 187±44s vs. 218±69s; p<0.001, RSPV: 147±31s vs. 192±51s; p<0.001, RIPV: 180±50 vs. 218±73s; p<0.001). The AF free survival rate during the follow-up period (356±167 days) was similar between the 2 groups (log-rank test, p=0.38). Furthermore, the complication rate was similar 2 groups.

The freezing time for each PV

Conclusion

The safety and efficacy of the new tailor-made CBA strategy were non-inferior to the standard procedure. This study showed that the unnecessary freezing time could be reduced in most of paroxysmal AF patients.

P2694Early and late restenosis after excimer laser coronary angioplasty and paclitaxel-coated balloon combination therapy for drug-eluting stent restenosis

Background

Drug-eluting stent restenosis (DES-ISR) is associated with poorer outcomes than those of bare-metal stent restenosis after treatment with paclitaxel-coated balloon (PCB), and late restenosis after PCB angioplasty for DES-ISR is a residual problem. Excimer laser coronary angioplasty (ELCA) is thought to be advantageous for ISR treatment by removing neointima. However, whether the combination of ELCA and PCB angioplasty is more effective than the use of PCB only angioplasty in DES-ISR has not been studied so far.

Purpose

We evaluated the efficacy of ELCA and PCB combination therapy for DES-ISR at mid-and late-term after revascularization.

Methods

From January 2014 to March 2016, 166 DES-ISR lesions were treated with ELCA and no-ELCA prior to PCB. Two serial angiographic follow-ups were planned for the patients (at 6–12 and 18–24 months after procedure). Acute procedural and follow-up angiographic results were assessed by quantitative coronary angiography. ELCA and no-ELCA group included 74 lesions and 92 lesions, respectively.

Results

There was no significant difference between the two groups in the clinical characteristics except the prevalence of hemodialysis, the rate of first-generation DES (37.9% vs 36.8%, p=0.897), previous stent size (2.90±0.39 mm vs 2.77±0.39 mm, p=0.063), and reference vessel diameter (2.65±0.46 mm vs 2.60±0.65 mm, p=0.593). Early follow-up angiography was performed in 66 lesions (89.1%) of ELCA group, and was done in 76 lesions (82.6%) of no-ELCA group. In the ELCA group, percentage diameter stenosis (%DS) just after procedure and at 6–12 months later were significantly smaller than those of no-ELCA group. Besides, target lesion revascularization (TLR) rate at 6–12 months after procedure was tended to be lower in the ELCA group. Late follow-up angiography was performed for 93 lesions (81.6%) of the remaining 114 lesions (excluding TLR lesion), late restenosis was found 9 lesions (18.6%) in the ELCA group and 11 lesions (24.4%) in the no-ELCA group (p=0.504). Late luminal loss was similar in both groups (0.37±0.71 mm vs 0.24±0.82 mm, p=0.438), and %DS at 12–18 months after revascularization was not different between the two groups.

Changes of %DS and TLR rate

Conclusions

%DS in the ELCA group was smaller at just after procedure and the advantage was kept even after 1-year. However, late restenosis and TLR at 2-year after revascularization for DES-ISR could not be reduced by ELCA and PCB combination therapy.

Controlling magnetism of Au133(TBBT)52 nanoclusters at single electron level and implication for nonmetal to metal transition

The [Au₁₃₃(SR)₅₂]^q nanocluster is discovered to possess one spin per particle when q = 0, but no unpaired electron when q = +1.

The transition from the discrete, excitonic state to the continuous, metallic state in thiolate-protected gold nanoclusters is of fundamental interest and has attracted significant efforts in recent research. Compared with optical and electronic transition behavior, the transition in magnetism from the atomic gold paramagnetism (Au 6s¹) to the band behavior is less studied. In this work, the magnetic properties of 1.7 nm [Au₁₃₃(TBBT)₅₂]⁰ nanoclusters (where TBBT = 4-tert-butylbenzenethiolate) with 81 nominal “valence electrons” are investigated by electron paramagnetic resonance (EPR) spectroscopy. Quantitative EPR analysis shows that each cluster possesses one unpaired electron (spin), indicating that the electrons fill into discrete orbitals instead of a continuous band, for that one electron in the band would give a much smaller magnetic moment. Therefore, [Au₁₃₃(TBBT)₅₂]⁰ possesses a nonmetallic electronic structure. Furthermore, we demonstrate that the unpaired spin can be removed by oxidizing [Au₁₃₃(TBBT)₅₂]⁰ to [Au₁₃₃(TBBT)₅₂]⁺ and the nanocluster transforms from paramagnetism to diamagnetism accordingly. The UV-vis absorption spectra remain the same in the process of single-electron loss or addition. Nuclear magnetic resonance (NMR) is applied to probe the charge and magnetic states of Au₁₃₃(TBBT)₅₂, and the chemical shifts of 52 surface TBBT ligands are found to be affected by the spin in the gold core. The NMR spectrum of Au₁₃₃(TBBT)₅₂ shows a 13-fold splitting with 4-fold degeneracy of 52 TBBT ligands, which are correlated to the quasi-D₂ symmetry of the ligand shell. Overall, this work provides important insights into the electronic structure of Au₁₃₃(TBBT)₅₂ by combining EPR, optical and NMR studies, which will pave the way for further understanding of the transition behavior in metal nanoclusters.

Three-orders-of-magnitude variation of carrier lifetimes with crystal phase of gold nanoclusters

We report a three-orders-of-magnitude variation of carrier lifetimes in exotic crystalline phases of gold nanoclusters (NCs) in addition to the well-known face-centered cubic structure, including hexagonal close-packed (hcp) Au₃₀ and body-centered cubic (bcc) Au₃₈ NCs protected by the same type of capping ligand. The bcc Au₃₈ NC had an exceptionally long carrier lifetime (4.7 microseconds) comparable to that of bulk silicon, whereas the hcp Au₃₀ NC had a very short lifetime (1 nanosecond). Although the presence of ligands may, in general, affect carrier lifetimes, experimental and theoretical results showed that the drastically different recombination lifetimes originate in the different overlaps of wave functions between the tetrahedral Au₄ building blocks in the hierarchical structures of these NCs.

Atomically Tailored Gold Nanoclusters for Catalytic Application

Recent advances in the synthetic chemistry of atomically precise metal nanoclusters (NCs) have significantly broadened the accessible sizes and structures. Such particles are well defined and have intriguing properties, thus, they are attractive for catalysis. Especially, those NCs with identical size but different core (or surface) structure provide unique opportunities that allow the specific role of the core and the surface to be mapped out without complication by the size effect. Herein, we summarize recent work with isomeric Au_n NCs protected by ligands and isostructural NCs but with different surface ligands. The highlighted work includes catalysis by spherical and rod-shaped Au₂₅ (with different ligands), quasi-isomeric Au₂₈ (SR)₂₀ with different R groups, structural isomers of Au₃₈ (SR)₂₄ (with identical R) and Au₃₈ S₂ (SR)₂₀ with body-centred cubic (bcc) structure, and isostructural [Au₃₈ L₂₀ (PPh₃ )₄ ]²⁺ (different L). These isomeric and/or isostructural NCs have provided valuable insights into the respective roles of the kernel, surface staples, and the type of ligands on catalysis. Future studies will lead to fundamental advances and development of tailor-made catalysts.

A Mono-cuboctahedral Series of Gold Nanoclusters: Photoluminescence Origin, Large Enhancement, Wide Tunability, and Structure-Property Correlation

The origin of the near-infrared photoluminescence (PL) from thiolate-protected gold nanoclusters (Au NCs, <2 nm) has long been controversial, and the exact mechanism for the enhancement of quantum yield (QY) in many works remains elusive. Meanwhile, based upon the sole steady-state PL analysis, it is still a major challenge for researchers to map out a definitive relationship between the atomic structure and the PL property and understand how the Au(0) kernel and Au(I)-S surface contribute to the PL of Au NCs. Herein, we provide a paradigm study to address the above critical issues. By using a correlated series of "mono-cuboctahedral kernel" Au NCs and combined analyses of steady-state, temperature-dependence, femtosecond transient absorption, and Stark spectroscopy measurements, we have explicitly mapped out a kernel-origin mechanism and clearly elucidate the surface-structure effect, which establishes a definitive atomic-level structure-emission relationship. A ∼100-fold enhancement of QY is realized via suppression of two effects: (i) the ultrafast kernel relaxation and (ii) the surface vibrations. The new insights into the PL origin, QY enhancement, wavelength tunability, and structure-property relationship constitute a major step toward the fundamental understanding and structural-tailoring-based modulation and enhancement of PL from Au NCs.

Sensitive X-ray Absorption Near Edge Structure Analysis on the Bonding Properties of Au30(SR)18 Nanoclusters

Au nanoclusters (NCs) with organothiolate protecting ligands are a field of great interest and X-ray absorption spectroscopy is a useful tool for the structure and property studies of these Au NCs. However, the Au NCs normally show broad and low-intensity features in the gold X-ray absorption near-edge structure (XANES) region, lowering the sensitivity of the technique and making it difficult to use for the analysis of Au NCs. In this work we report a sensitive gold L₃-edge XANES study on the bonding properties of the newly discovered Au₃₀(SR)₁₈ NCs utilizing a combined approach of the first derivative XANES spectra and quantum simulations. First derivative XANES spectra are compared with the well-studied Au₂₅(SR)₁₈ with the aim of determining the unique features of Au₃₀(SR)₁₈. It is found that the early XANES region of the Au NCs is significantly influenced by the gold-gold bonding environment in the surface sites, as the varying surface Au-Au bond lengths in Au₂₅(SR)₁₈ and Au₃₀(SR)₁₈ result in pronounced difference in the first derivative XANES. These findings can be consistently explained using site-selective quantum simulations of the XANES spectra based on the Au NC structural models. The XANES method presented in this work offers a useful tool for the sensitive analysis on structure and bonding properties of Au NCs.

Toward the Tailoring Chemistry of Metal Nanoclusters for Enhancing Functionalities

Ultrasmall metal nanoparticles (often called nanoclusters) possess unique geometrical structures and novel functionalities that are not accessible in conventional nanoparticles. Recent progress in their synthesis and structural determination by X-ray crystallography has led to deep understanding of the structural evolution, structure-property correlation, and growth modes, such as the layer-by-layer growth in face-centered cubic (fcc)-type nanoclusters, linear assembly of vertex-shared icosahedral units, and other unique modes. The enriched knowledge on the correlation between the structure and the properties has rendered metal nanoclusters a new class of functional nanomaterials. Despite the significant achievements in structural determinations, mapping out the structure-property correlation is still very challenging because of the core-shell structures of nanoclusters (e.g., Au _n(SR) _m protected by thiolate ligands) with metal atoms partitioned between the core and the shell. In such structures, the core and the surface are entangled and cannot be separately studied because changing the core structure would inevitably change the surface (or vice versa). Thus, it is of great importance to develop the "tailoring" chemistry for structural modification of the core (or surface) while retaining the other parts, in order to achieve fundamental understanding of what part of the nanocluster structure plays what role in the functionalities. In this Account, we summarize some recent work on the strategies to control the atomic structures of metal nanoclusters for tuning their properties, such as stability, optical absorption, excited-state electron dynamics, and photoluminescence, as well as their catalytic reactivity. The development of a ligand-based strategy has permitted the synthesis of structural isomers of nanoclusters with the same size but different functionalities. Successful modification of the core (or surface) structure while maintaining the other components has led us to gain some fundamental understanding of the respective roles of the core and the surface in the nanocluster functionalities. Such "tailoring" chemistry on metal nanoclusters can provide a strong basis for functional nanomaterials consisting of nanocluster components with desired properties. Further development of the tailoring chemistry will guide materials chemists to new directions and tailor-made functional nanomaterials for specific applications.

Oxidation-Induced Transformation of Eight-Electron Gold Nanoclusters: [Au23(SR)16]- to [Au28(SR)20]0

Here we report an oxidation-induced transformation of [Au₂₃(S-c-C₆H₁₁)₁₆]^-TOA⁺ (S-c-C₆H₁₁: cyclohexanethiolate; TOA: tetraoctylammonium) to the [Au₂₈(S-c-C₆H₁₁)₂₀]⁰ nanocluster by H₂O₂ treatment under ambient conditions. This is the first example of oxidation-induced transformation of one stable size to another with atomic precision. The product was crystallized and analyzed by X-ray crystallography. Further insights into the transformation process were obtained by monitoring the process with optical spectroscopy and also by electrochemical analysis. This work adds a new dimension to the recently established transformation chemistry of nanoclusters that involves size and structure transformations.

Randomized clinical trial comparing two vessel-sealing devices with crush clamping during liver transection

Background

Previous RCTs have failed to demonstrate the usefulness of combining energy devices with the conventional clamp crushing method to reduce blood loss during liver transection. Here, the combination of an ultrasonically activated device (UAD) and a bipolar vessel-sealing device (BVSD) with crush clamping was investigated.

Methods

Patients scheduled to undergo hepatectomy at the University of Tokyo Hospital or Nihon University Itabashi Hospital were eligible for this parallel-group, single-blinded randomized study. Patients were assigned to a control group (no energy device used), an UAD group or a BVSD group. The primary endpoint was the volume of blood loss during liver transection. Outcomes of the control group and the combined energy device groups (UAD plus BVSD) were first compared. Pairwise comparisons among the three groups were made for outcomes for which the combined energy device group was superior to the control group.

Results

A total of 380 patients were enrolled between July 2012 and May 2014; 116 patients in the control group, 122 in the UAD group and 123 in the BVSD group were included in the final analysis. Median blood loss during liver transection was lower in the combined energy device group (245 patients) than in the control group (116 patients): median 190 (range 0–3575) versus 230 (range 3–1570) ml (P = 0·048). Pairwise comparison revealed that blood loss was lower in the BVSD group than in the control group (P = 0·043).

Conclusion

The use of energy devices combined with crush clamping reduced blood loss during liver transection. Registration number: C000008372 (www.umin.ac.jp/ctr/index.htm).

Partially oxidized iridium clusters within dendrimers: size-controlled synthesis and selective hydrogenation of 2-nitrobenzaldehyde

Iridium clusters nominally composed of 15, 30 or 60 atoms were size-selectively synthesized within OH-terminated poly(amidoamine) dendrimers of generation 6. Spectroscopic characterization revealed that the Ir clusters were partially oxidized. All the Ir clusters efficiently converted 2-nitrobenzaldehyde to anthranil and 2-aminobenzaldehyde under atmospheric hydrogen at room temperature in toluene via selective hydrogenation of the NO2 group. The selectivity toward 2-aminobenzaldehyde over anthranil was improved with the reduction of the cluster size. The improved selectivity is ascribed to more efficient reduction than intramolecular heterocyclization of a hydroxylamine intermediate on smaller clusters that have a higher Ir(0)-phase population on the surface.

Isomerism in Au28(SR)20 Nanocluster and Stable Structures

Understanding the isomerism phenomenon at the nanoscale is a challenging task because of the prerequisites of precise composition and structural information on nanoparticles. Herein, we report the ligand-induced, thermally reversible isomerization between two thiolate-protected 28-gold-atom nanoclusters, i.e. Au28(S-c-C6H11)20 (where -c-C6H11 = cyclohexyl) and Au28(SPh-(t)Bu)20 (where -Ph-(t)Bu = 4-tert-butylphenyl). The intriguing ligand effect in dictating the stability of the two Au28(SR)20 structures is further investigated via dispersion-corrected density functional theory calculations.

Criteria for drain removal following liver resection

BACKGROUND

Abdominal drains have been placed prophylactically and removed in liver resection without robust evidence. The present study was designed to establish the optimal time for removal of such drains.

METHODS

Data on abdominal prophylactic drains were analysed in a consecutive series of patients who underwent liver resection for malignancy between 2006 and 2009. Bilirubin levels in drain fluid were measured and bacteriological cultures were taken on days 1, 3, 5 and 7 after surgery. Drains were removed on day 3 if the drain-fluid bilirubin level was less than 5 mg/dl and bacteriological cultures were negative. Drains remained in situ until these conditions were met.

RESULTS

A total of 514 abdominal drains were placed in 316 patients operated on in the study period. Fifty-eight patients (18·4 per cent) had positive drain-fluid cultures and 14 (4·4 per cent) had bile leakage (drain-fluid bilirubin level 5 mg/dl or more). Only one patient required ultrasound-guided abdominal drainage. On multivariable analysis, drain-fluid bilirubin level on day 3 after surgery was the strongest predictor of infection (odds ratio 15·11, 95 per cent confidence interval 3·04 to 92·11; P < 0·001). The area under the receiver operating characteristic curve on day 3 had the highest predictive value: 83·6 per cent accuracy and 3·9 per cent false-positive rate for a drain-fluid bilirubin level of 3·01 mg/dl (51·5 µmol/l).

CONCLUSION

The '3 × 3 rule' (drain-fluid bilirubin level below 3 mg/dl on day 3 after operation) is an accurate criterion for removal of prophylactically placed abdominal drains in liver resection.

COX/PGE(2) axis critically regulates effects of LPS on eosinophilia-associated cytokine production in nasal polyps

BACKGROUND

Lipopolysaccharide (LPS) has shown heterogeneous effects on eosinophilic inflammation in airways. However, little is known about how LPS regulates pathogenesis of chronic rhinosinusitis with nasal polyps, a major form of eosinophilic inflammation in the upper airway.

OBJECTIVE

We sought to investigate the effect of LPS on cytokine production by dispersed nasal polyp cells (DNPCs).

METHODS

Either diclofenac-treated or untreated DNPCs were cultured with or without staphylococcal enterotoxin B (SEB) in the presence or absence of LPS, after which the levels of IL-5, IL-13, IL-17A and IFN-γ within the supernatant were measured. The effects of PGE(2) on LPS-induced responses by diclofenac-treated DNPCs were also examined. LPS-induced PGE(2) production and mRNA expression of COX-1, COX-2 and microsomal PGE(2) synthase-1 (m-PGES-1) were measured.

RESULTS

Staphylococcal enterotoxin B induced IL-5, IL-13, IL-17A and IFN-γ production by DNPCs. Pre-treatment with LPS prior to SEB stimulation inhibited production of these cytokines. After stimulation with LPS, PGE(2) production and expression of COX-2 and m-PGES-1 mRNA by DNPCs increased significantly. In the presence of diclofenac, the suppressive effects of LPS were eliminated. LPS pre-treatment enhanced SEB-induced IL-5, IL-13 and IL-17A production in diclofenac-treated DNPCs, while addition of PGE(2) inhibited IL-5, IL-13 and IFN-γ production. LPS alone induced IL-5, IL-13 and IFN- γ production by diclofenac-treated DNPCs, while the addition of EP2 and EP4 receptor-selective agonists, as well as PGE(2) itself, inhibited IL-5 and IL-13 production.

CONCLUSIONS AND CLINICAL RELEVANCE

These results suggest that the regulatory effects of LPS on eosinophilic airway inflammation are controlled via the COX-2/PGE(2) axis. For clinical implications, indiscreet use of non-steroidal anti-inflammatory drugs should be avoided in patients with chronic rhinosinusitis with nasal polyps.

Lipopolysaccharide induces proinflammatory cytokines and chemokines in experimental otitis media through the prostaglandin D2 receptor (DP)-dependent pathway

Otitis media is one of the most common and intractable ear diseases, and is the major cause of hearing loss, especially in children. Multiple factors affect the onset or development of otitis media. Prostaglandin D₂ is the major prostanoid involved in infection and allergy. However, the role of prostaglandin D₂ and prostaglandin D2 receptors on the pathogenesis of otitis media remains to be determined. Recent studies show that D prostanoid receptor (DP) and chemoattractant receptor-homologous molecule expressed on T helper type 2 (Th2) cells (CRTH2) are major prostaglandin D₂ receptors. In this study, homozygous DP single gene-deficient (DP⁻(/)⁻) mice, CRTH2 single gene-deficient (CRTH2⁻(/)⁻) mice and DP/CRTH2 double gene-deficient (DP⁻(/)⁻ CRTH2⁻(/)⁻) mice were used to investigate the role of prostaglandin D₂ and its receptors in otitis media. We demonstrate that prostaglandin D₂ is induced by lipopolysaccharide (LPS), a major component of Gram-negative bacteria, and that transtympanic injection of prostaglandin D₂ up-regulates macrophage inflammatory protein 2 (MIP-2), interleukin (IL)-1β and IL-6 in the middle ear. We also show that middle ear inflammatory reactions, including infiltration of inflammatory cells and expression of MIP-2, IL-1β and IL-6 induced by LPS, are reduced significantly in DP⁻(/)⁻ mice and DP⁻(/)⁻ CRTH2⁻(/)⁻ mice. CRTH2⁻(/)⁻ mice display inflammatory reactions similar to wild-type mice. These findings indicate that prostaglandin D₂ may play significant roles in LPS-induced experimental otitis media via DP.

Role of fungal antigens in eosinophilia-associated cellular responses in nasal polyps: a comparison with enterotoxin

BACKGROUND

Fungi and/or Staphylococcus aureus enterotoxins (SEs) may participate in the pathogenesis of eosinophilic inflammation in cases of chronic rhinosinusitis with nasal polyps (CRSwNP). Objective We sought to determine the effects of fungal antigens on eosinophilia-associated cellular responses in nasal polyps.

METHODS

Dispersed nasal polyp cells (DNPCs) were prepared from 13 patients with CRSwNP. DNPCs were cultured with fungal extracts (Aspergillus, Alternaria and Candida) or SEB for 72 h, after which the levels of IL-5, IL-13 and RANTES were measured within the supernatant. Responses to β-d-glucan, mannan and chitin were also examined.

RESULTS

38.5%, 69.2% and 30.8% of DNPCs produced IL-5, IL-13 and RANTES, respectively, in response to 200 μg/mL of Aspergillus. 53.8%, 53.8% and 7.7% of DNPCs produced IL-5, IL-13 and RANTES, respectively, in response to 200 μg/mL of Alternaria. 53.8%, 38.5% and 15.4% of DNPCs produced IL-5, IL-13 and RANTES, respectively, in response to 200 μg/mL of Candida. All DNPCs produced these cytokines in response to 0.1 μg/mL of SEB. SEB induced significantly greater cytokine levels than the fungal extracts. No correlation between cytokine production following exposure to each of the fungal extracts or SEB and various clinical features, including nasal polyp eosinophilia and radiological severity of sinusitis was observed. Neither sensitization to fungus nor comorbidity with bronchial asthma was correlated with the fungal extract-induced cytokine production by DNPCs. β-d-glucan, mannan and chitin did not induce significant cytokine production.

CONCLUSIONS

These results suggest that, although DNPCs produce IL-5, IL-13 and RANTES in response to fungal extracts, fungal antigens including major carbohydrates are less capable of inducing eosinophilia-associated cellular responses in nasal polyps than SEB.

Allergen-specific immunotherapy alters the expression of B and T lymphocyte attenuator, a co-inhibitory molecule, in allergic rhinitis

BACKGROUND

B7/CD28 family co-signalling molecules play a key role in regulating T cell activation and tolerance. Allergen-specific immunotherapy (SIT) alters allergen-specific T cell responses. However, the effect of SIT on the expression of various co-signalling molecules has not been clarified.

OBJECTIVE

We sought to determine whether SIT might affect the expression of three co-inhibitory molecules, programmed death (PD)-1, B7-H1 and B and T lymphocyte attenuator (BTLA), in Japanese cedar pollinosis (JCP).

METHODS

Peripheral blood mononuclear cells (PBMCs) were isolated from JCP patients who had or had not received SIT. PBMC were cultured in the presence or absence of Cry j 1, after which the cell surface expression of PD-1, B7-H1 and BTLA, as well as IL-5 production, were determined. In addition, the effect of BTLA cross-linking on IL-5 production was examined.

RESULTS

After Cry j 1 stimulation, no significant differences in PD-1 and B7-H1 expression were observed between SIT-treated and SIT-untreated patients. BTLA expression was down-regulated in untreated patients after Cry j 1 stimulation and up-regulated in SIT-treated patients. Up-regulation of BTLA in SIT-treated patients was particularly apparent in a CD4(+) T cell subset. IL-5 production was clearly reduced among SIT-treated patients, and the observed changes in BTLA expression correlated negatively with IL-5 production. Moreover, immobilization of BTLA suppressed IL-5 production in JCP patients.

CONCLUSION

These results suggest that both IL-5 production and down-regulation of BTLA in response to allergen are inhibited in SIT-treated patients with JCP. BTLA-mediated co-inhibition of IL-5 production may contribute to the regulation of allergen-specific T cell responses in patients receiving immunotherapy.

Recent progress in living cell imaging of plant cytoskeleton and vacuole using fluorescent-protein transgenic lines and three-dimensional imaging

In higher-plant cells, microtubules, actin microfilaments, and vacuoles play important roles in a variety of cellular events, including cell division, morphogenesis, and cell differentiation. These intracellular structures undergo dynamic changes in their shapes and functions during cell division and differentiation, and to analyse these sequential structural changes, the vital labelling technique, using the green-fluorescent protein or other fluorescent proteins, has commonly been used to follow the localisation and translocation of specific proteins. To visualise microtubules, actin filaments, and vacuoles, several strategies are available for selecting the appropriate fluorescent-protein fusion partner: microtubule-binding proteins, tubulin, and plus-end-tracking proteins are most suitable for microtubule labelling; the actin binding domain of mouse talin and plant fimbrin for actin microfilament visualisation; and the tonoplast-intrinsic proteins and syntaxin-related proteins for vacuolar imaging. In addition, three-dimensional reconstruction methods are indispensable for localising the widely distributed organelles within the cell. The maximum intensity projection method is suitable for cytoskeletal structures, while contour-based surface modelling possesses many advantages for vacuolar membranes. In this article, we summarise the recent progress in living cell imaging of the plant cytoskeleton and vacuoles using various fusions with green-fluorescent proteins and three-dimensional imaging techniques.

Clonal chromosomal aberrations accompanied by strong telomerase activity in immortalization of human B-lymphoblastoid cell lines transformed by Epstein-Barr virus

Human B-lymphoblastoid cell lines transformed by Epstein-Barr (EBV-LCLs) are considered to be immortalized, although most of them show a normal diploid karyotype. Recently, we and others have shown that only part of EBV-LCLs is immortalized by developing strong telomerase activity that stabilizes the telomeres. In this study, we investigated the change in karyotypes during immortalization. All the eight immortalized cell lines developed clonal chromosomal aberrations accompanied by the development of strong telomerase activity. Interestingly, abnormal chromosomes were not shared among the immortalized cell lines. These results strongly suggest that chromosomal rearrangements and induction of strong telomerase activity are two events that take place in parallel in the process of immortalization of EBV-LCLs, and indicate that EBV-LCLs are clearly divided into two distinct groups, pre-immortal cell lines mostly with a normal diploid karyotype and post-immortal cell lines with a clonally abnormal karyotype.

Effect of cicletanine on the nitric oxide pathway in human umbilical vein endothelial cells

The purpose of this study was to evaluate the effects of cicletanine, a slightly diuretic antihypertensive drug, on human vascular endothelial cells with regard to nitric oxide, intracellular calcium concentration ([Ca2+]i), cyclic nucleotide, inositol 1,4,5-trisphosphate (IP3), and prostacyclin generation. Primary cultured human umbilical vein endothelial cells were used in this study. [Ca2+]i was measured by fura-2/AM. Cyclic adenosine monophosphate (AMP), cyclic guanosine monophosphate (GMP), IP3, and prostacyclin were measured by radioimmunoassay. Nitric oxide was measured by the Griess method. Cicletanine had no effect on [Ca2+]i. Cicletanine (10(-6)-10(-4) M) increased cyclic GMP but decreased prostacyclin generation. Cicletanine had no stimulating effect on cyclic AMP or IP3 generation. IP3 increased 45Ca release from storage sites. Cicletanine decreased prostacyclin generation via increase in cyclic GMP. Cicletanine had no stimulating effect on nitrogen oxides for 2 h after incubation but increased it after 3-24 h. Pretreatment with L-N(G)-monomethyl-arginine (L-NMMA) prevented this increase. The inhibitory effect of L-NMMA was prevented by pretreatment with L-arginine. These results indicate that nitric oxide and cyclic GMP may contribute to the antihypertensive action of cicletanine.

Effects of bradykinin on prostaglandin I(2) synthesis in human vascular endothelial cells

The effects of bradykinin on the regulatory mechanisms of prostacyclin synthesis in endothelial cells were investigated in association with intracellular Ca(2+) kinetics, cytosolic phospholipase A(2) (cPLA(2)) activity, and mRNA expression of cPLA(2) and prostaglandin H synthase (PGHS) isoforms. Bradykinin enhanced prostacyclin release from endothelial cells time-dependently, but pretreatment with EGTA H-7 or HOE 140 inhibited bradykinin-induced prostacyclin release. Bradykinin increased both the influx of extracellular Ca(2+) and Ca(2+) release from the intracellular Ca(2+) storage sites. These reactions occurred within 5 minutes after bradykinin stimulation. Within 15 minutes, bradykinin activated cPLA(2) to 1.3-fold the control level. The constitutive expressions of mRNA of cPLA(2), PGHS-1, and PGHS-2 was 87, 562, and 47 amol/microg RNA, respectively. With the stimulation of bradykinin, cPLA(2) mRNA increased to 746 amol/microg RNA in 15 minutes, PGHS-1 mRNA increased to 10 608 amol/microg RNA, and PGHS-2 mRNA increased to 22 400 amol/microg RNA in 180 minutes. Pretreatment with cycloheximide superinduced cPLA(2) and PGHS-2 mRNA expression but almost completely inhibited PGHS-1. Pretreatment with EGTA had effects similar to pretreatment with cycloheximide in the case of cPLA(2) and PGHS-1 but did not affect PGHS-2. These findings suggest that the elevation of cPLA(2) activity caused by the increase of intracellular Ca(2+) concentration is important in the early phase of bradykinin-induced prostacyclin synthesis and that the mechanisms regulating cPLA(2) are different from those regulating PGHS isoforms in endothelial cells.