Beyond the Threshold: A Study of Chalcogenophene-Based Two-Photon Initiators.

A series of nine soluble, symmetric chalcogenophenes bearing hexyl-substituted triphenylamines, indolocarbazoles, or phenylcarbazoles was designed and synthesized as potential two-photon absorption (2PA) initiators. A detailed photophysical analysis of these molecules revealed good 2PA properties of the series and, in particular, a strong influence of selenium on the 2PA cross sections, rendering these materials especially promising new 2PA photoinitiators. Structuring and threshold tests proved the efficiency and broad spectral versatility of two selenium-containing lead compounds as well as their applicability in an acrylate resin formulation. A comparison with commercial photoinitiators Irg369 and BAPO as well as sensitizer ITX showed that the newly designed selenium-based materials TPA-S and TPA-BBS outperform these traditional initiators by far both in terms of reactivity and dose. Moreover, by increasing the ultralow concentration of TPA-BBS, a further reduction of the polymerization threshold can be achieved, revealing the great potential of this series for application in two-photon polymerization (2PP) systems where only low laser power is available.

Symmetric Mixed Sulfur-Selenium Fused Ring Systems as Potential Materials for Organic Field-Effect Transistors.

A reliable synthetic protocol toward a series of fused chalcogenopheno[1]benzochalcogenophene (CBC) building blocks was developed based on a Fiesselmann reaction. The obtained CBC units were applied in McMurry and Stille coupling reactions toward symmetric regioisomeric ene-linked dimers. These π-conjugated compounds were characterized regarding their photophysical and electrochemical properties and proved to be materials with reduced HOMO-LUMO gaps compared to their sulfur-based analogues. Single-crystal X-ray diffraction experiments revealed strong intermolecular selenium-selenium and selenium-carbon interactions depending on the position and number of incorporated selenium atoms. Good field-effect transistor performance with charge carrier mobilities up to 4×10-3  cm2 V-1 s-1 and high on/off ratios could be observed.

Selective single-molecule analytical detection of C-reactive protein in saliva with an organic transistor.

In the last decade, saliva has been suggested as non-invasive diagnostic fluid, suitable for clinical use alternatively to blood serum and plasma. However, the clinical applicability of saliva has been hampered so far by the inadequate sensitivity of current methods to detect the lower salivary concentrations of many biomarkers monitored in blood products. Herein, a label-free biosensor based on electrolyte-gated organic thin-film transistor (EGOTFT) has been developed for the detection at the physical limit of C-reactive protein (CRP) in human saliva. CRP is a key relevant biomarker for inflammatory processes and is routinely monitored for many clinical purposes. Herein, an electrolyte-gated thin-film transistor (EGOTFT) has been proposed as a transducer of the biorecognition event taking place at the gate electrode, functionalized with a self-assembled monolayer (SAM) of highly densely packed capturing anti-CRP proteins. Thanks to the SAM, the biosensing platform herein proposed is endowed with ultra-high sensitivity, along with an extremely high selectivity, assessed by measuring the dose curves of CRP interacting with a bovine serum albumin-functionalized gate. Moreover, the biosensing platform is compatible with low-cost fabrication techniques and applicable to the ultra-sensitive detection of a plethora of clinically relevant biomarkers. Therefore, the EGOTFT device herein proposed, being able to operate in physiologically relevant fluids such as saliva, will set the ground to a major revolution in biosensing applications for early clinical detection.

Single-molecule detection with a millimetre-sized transistor.

Label-free single-molecule detection has been achieved so far by funnelling a large number of ligands into a sequence of single-binding events with few recognition elements host on nanometric transducers. Such approaches are inherently unable to sense a cue in a bulk milieu. Conceptualizing cells' ability to sense at the physical limit by means of highly-packed recognition elements, a millimetric sized field-effect-transistor is used to detect a single molecule. To this end, the gate is bio-functionalized with a self-assembled-monolayer of 1012 capturing anti-Immunoglobulin-G and is endowed with a hydrogen-bonding network enabling cooperative interactions. The selective and label-free single molecule IgG detection is strikingly demonstrated in diluted saliva while 15 IgGs are assayed in whole serum. The suggested sensing mechanism, triggered by the affinity binding event, involves a work-function change that is assumed to propagate in the gating-field through the electrostatic hydrogen-bonding network. The proposed immunoassay platform is general and can revolutionize the current approach to protein detection.

A novel selenoalkenyl-isoxazole based donor-acceptor nonlinear optical material.

The structure property relationships of untwinned enantiomorphic Z-(methylseleno)alkenyl-substituted phenyl-isoxazole and its isostructural triazole congener both crystallizing in the P212121 space group were investigated with respect to UV/vis absorption, thermal behaviour, and second harmonic generation ability. Differential scanning calorimetry revealed a significantly higher melting point of the novel isoxazole compound compared to the triazole derivative and therefore a broader thermal application window. The SHG efficiency of the isoxazole derivative is approximately two thirds the value of the triazole compound and approximately 27 times higher than potassium dihydrogen phosphate. Thus, the developed molecular scaffold represents an interesting novel type of nonlinear optical (NLO) chromophore.

Specific Monitoring of Excited-State Symmetry Breaking by Femtosecond Broadband Fluorescence Upconversion Spectroscopy.

Most quadrupolar molecules designed for large two-photon absorption cross section have been shown to undergo symmetry breaking upon excitation to the S1 state. This was originally deduced from their strong fluorescence solvatochromism and later visualized in real time using transient infrared spectroscopy. For molecules not containing clear IR marker modes, however, a specific real-time observation of the symmetry breaking process remains lacking. Here we show that this process can be resolved using broadband fluorescence upconversion spectroscopy by monitoring the instantaneous emission transition dipole moment. This approach is illustrated with measurements performed on two quadrupolar molecules, with only one of them undergoing excited-state symmetry breaking in polar solvents.

Characterization of Covalently Bound Anti-Human Immunoglobulins on Self-Assembled Monolayer Modified Gold Electrodes.

Bioconjugated gold surfaces constitute interesting platforms for biosensing applications. The immobilization of antibodies such as anti-immunoglobulin G and M (anti-IgG and anti-IgM) on gold electrodes via self-assembled monolayers (SAMs) is here studied as a model system for further immunoassays development. The biolayer is characterized by means of X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), a dedicated thin-film transistor (TFT)-based platform and electrochemical surface plasmon resonance (EC-SPR). XPS analysis confirms the presence of all the chemical species involved in the fabrication process as well as the covalent attachment of the antibodies with high reproducibility. Visualization of the biolayer topography by AFM shows nanostructures with a thickness consistent with the actual size of the protein, which is also verified by SPR measurements. EC-SPR allows taking advantage of complementary electrochemical and optical signals during the functionalization steps. Moreover, the functionalization of gold leads to a change in the work function, which is demonstrated in an electrolyte gated thin-film transistor configuration. Such configuration enables also to evaluate the electrostatic changes occurring on the gate that are connected with the threshold voltage shifts. The data support that functional biomodified gold surfaces can be reproducibly prepared, which is a prerequisite for further biosensor development.

Color Fine-Tuning of Optical Materials Through Rational Design.

We report on the feasibility for color fine-tuning of optical materials using rational design principles based on chemical reasoning. For this purpose, a modular framework for the construction of symmetrical cap-linker-cap compounds, using triarylamine caps and oligothiophene linkers, is applied. The chosen structural scaffolds are heavily used in recent industrial applications and provide five possibilities for altering their electronic and steric properties: electron donor/acceptor groups, planarization/deplanarization, and modulation of the π-conjugation length. Permutation of the used building blocks leads to a set of 54 different molecules, out of which 32 are synthesized and characterized in solution as well as in example fabricated OLED devices. This setup allows for color fine-tuning in the range of 412 nm to 540 nm with typical steps of 4 nm. In addition, to further benefit from the large experimental data set the spectroscopic results are used to benchmark quantum chemical computations, which show excellent agreement thus highlighting the potential of these calculations to guide future syntheses.

Sacral nerve stimulation in patients after rectal resection--preliminary report.

INTRODUCTION: Sacral nerve stimulation is a widely accepted therapeutic option for neurogenic fecal incontinence. More recently, case reports showed a positive effect of sacral nerve stimulation in patients with fecal incontinence following low anterior resection. The purpose of this study was to gain more information for this selected indication for sacral nerve stimulation through a nationwide survey. MATERIAL AND METHODS: In the period 2002 to 2005, three Austrian departments reported data of patients who underwent SNS for fecal incontinence following rectal resection. Data were available of seven patients (two female, five male) with a median age of 57 years (min 42; max 79). Six patients had undergone rectal resection as a treatment for low rectal cancer. One patient had undergone rectal resection for Crohn's disease, one patient subtotal colectomy and ileorectostomy for slow colon transit constipation. RESULTS: Test stimulation was performed in the foramen S3 unilaterally over a median period of 14 days (2-21 days). Seven patients reported a marked reduction of episodes of incontinence during the observation period and received a permanent stimulation system. After a median follow-up of 32 months (17-46), five patients reported a marked improvement of their continence situation. CONCLUSION: Despite a nationwide survey experiences with SNS as a treatment for fecal incontinence following rectal resection is still limited. Our observations show an improvement of the continence function following SNS. However, the promising results of our series as well as others need further research and more clinical data by a larger number of patients in a prospective trial.

Do geographic and educational factors influence the quality of life in rectal cancer patients with a permanent colostomy?

PURPOSE: This study was designed to evaluate possible social and geographic factors that could have an impact on quality of life in patients after abdominoperineal excision of the rectum. Although the number of patients with rectal cancer who need to be treated with abdominoperineal excision of the rectum and construction of permanent colostomy has greatly decreased in the past, there is still controversy about the influence on quality of life caused by this procedure. METHODS: In a prospective trial, patients operated on for low rectal cancer by abdominoperineal excision of the rectum were evaluated by a quality of life questionnaire, modified from The American Society of Colon and Rectal Surgeons questionnaire, to assess fecal incontinence. The results for the four domains of quality of life (lifestyle, coping behavior, embarrassment, depression), as well as for subjective general health, were evaluated with regard to age, gender, education, and geographic origin in univariate and multivariate analyses. RESULTS: Thirteen institutions in 11 countries included data from 257 patients. Although the analysis of general health did not reveal any significant differences, the analysis of the four quality of life domains showed the significant influence of geographic origin. The presence of a permanent colostomy showed a consistently negative impact on patients in southern Europe as well as for patients of Arabic (Islamic) origin. On the other hand, age, gender, and educational status did not reveal a statistically significant influence. CONCLUSIONS: This is the first study to show the influence of geographic origin on quality of life of patients with a permanent colostomy. Possible factors that may influence the outcome of patients after surgical treatment of rectal cancer, such as weather, religion, or culture, should be taken into account when quality of life evaluations are considered.

Technique and long-term results of intersphincteric resection for low rectal cancer.

PURPOSE: Intersphincteric resection of low rectal tumors is a surgical technique extending rectal resection into the intersphincteric space. This procedure is performed by a synchronous abdominoperineal approach with mesorectal excision and excision of the entire or part of the internal sphincter. This study was designed to evaluate the long-term results of this method focused on continence function and oncologic results. METHODS: From 1984 to 2000, a total of 121 patients were operated on. The patients were evaluated prospectively according to a detailed preoperative and postoperative program. RESULTS: One hundred seventeen patients had rectal cancers, two had dysplastic villous adenomas, and two had carcinoid tumors. Cancers were staged according to the Dukes classification (Stage A in 41 percent, Stage B in 28 percent, and Stage C in 31 percent; median distance from the anal margin, 3 (range, 1-5) cm). Postoperative complications were: one death because of pulmonary embolism, 5.1 percent developed an anastomotic fistula, one patient had a fistula to the bladder requiring reoperation, one patient with ileus needed relaparotomy as well as one for intra-abdominal hemorrhage and a small-bowel fistula. One patient developed a fistula after closing the protective colostomy. Five patients developed late strictures of the coloanal anastomosis. After a median follow-up of 72.86 months, 5.3 percent of patients developed local recurrence. The continence status was satisfactory with 16 patients (13.7 percent) showing continence for solid stool only, and 1 patient (0.8 percent) showing episodes of incontinence. A transient problem was a high stool frequency after closure of the protective stoma. CONCLUSIONS: Intersphincteric resection is a valuable procedure for sphincter-saving rectal surgery. We showed that this technique has satisfactory long-term results in functional and oncologic respects. An important prerequisite is a careful preoperative evaluation of local tumor spread with rectal magnetic resonance imaging excluding infiltration of the external sphincter.

Magnetic resonance imaging predicts sphincter invasion of low rectal cancer and influences selection of operation.

BACKGROUND: With the development of numerous sphincter-saving surgical techniques in the last 2 decades, the indication for abdominoperineal resection in radical-elective operations has been markedly reduced. The preoperative assessment of the extent of local tumor growth is essential for the planning of the optimal surgical procedure. Magnetic resonance imaging (MRI) proved to be a reliable method for local staging of low rectal carcinoma. The objective of this study was to determine the frequency of sphincter invasion in an unselected population with low rectal cancer. METHODS: From 1997 to 1999, 40 patients with histologically verified adenocarcinoma of the lower rectum (+/-5 cm above the linea dentata) without evidence of metastases underwent a MRI with a body coil (no anal endocoil). The MRI results were compared with the operative situs and with pathohistologic findings. RESULTS: An infiltration of the sphincter ani internus was observed in 11 cases (28%), and a combined infiltration of the sphincter ani internus and externus was found in 2 patients (5%). The median distance of the lower tumor edge to the upper border of the anal canal was 2.0 cm (range, 0-4.5 cm). No infiltration of the external sphincter was observed in patients with cancers above the anal canal. Nine patients (22%) were treated with intersphincteric resection and coloanal anastomosis, 12 (30%) with ultralow resection, and 11 (28%) with low anterior resection of the rectum in conjunction with coloanal anastomosis or a stapled anastomosis. Eight (17%) of the patients were treated with abdominoperineal resection. CONCLUSION: An infiltration of the internal sphincter occurs only in 28% of low rectal cancers; an infiltration of the external anal sphincter is extremely rare and occurred only in patients with cancers located in the anal canal. Pelvic MRI offers a precise preoperative visualization of sphincter infiltration in patients with low rectal cancers and is therefore a valuable tool for planning of rectal surgery.

Efficacy of diagnosis of mechanical cholestasis by magnetic resonance cholangiography.

The aims of this study were to evaluate the effectiveness of magnetic resonance cholangiography (MRC) in diagnosing patients with cholestasis and to compare these results to those obtained with endoscopic retrograde cholangiopancreaticography(ERCP). From January 1996 to December 1998 a total of 85 consecutive patients who were candidates for ERCP because of a suspected diagnosis of mechanical cholestasis were included in this study. All patients underwent MRC and consecutive ERCP 24 to 48 hours later. The sensitivity for detecting common bile duct stones was 93%,specificity 74%, positive predictive value 89%, and negative predictive value 82%. For the determination of tumorous bile duct stenosis the sensitivity and specificity were both 100%. MRC might be an ideal method for evaluating patients with unclear laboratory or ultrasonography findings before laparoscopic cholecystectomy, thereby avoiding unnecessary invasive diagnostic tests with possible harmful complications.