Biopsy Confirmed Doxycycline Induced Gastric Mucosal Injury

Doxycycline (DOX) is a tetracycline antibiotic that is prescribed for treating a variety of infections involving the skin, respiratory tract, and urogenital system. Adversely, esophageal mucosal injury due to DOX is well described; however, gastric mucosal injury is less commonly reported and may result in severe gastrointestinal hemorrhage and occasionally, perforation. In most reported cases of DOX-induced gastric lesions, patients are symptomatic upon presentation leading to endoscopic evaluation and diagnosis with biopsy. However, severe gastric insults may go unrecognized in rare cases of asymptomatic patients, increasing the risk of mortality.

The Clinical Course and Management of Severe Esophagitis Dissecans Superficialis: A Case Report

Esophagitis dissecans superficialis is a rare clinical endoscopic finding with poorly understood pathogenesis and ill-defined management. A 71-year-old man is admitted with progressively worsening dysphagia and odynophagia with endoscopic features most consistent with severe esophagitis dissecans superficialis. Extensive workup did not reveal an etiology, and he was subsequently treated with steroids, resulting in rapid, almost complete clinical and endoscopic recovery.

Efficacy of Glecaprevir and Pibrentasvir in Patients With Genotype 1 Hepatitis C Virus Infection With Treatment Failure After NS5A Inhibitor Plus Sofosbuvir Therapy

BACKGROUND & AIMS

Treatment options are limited for patients with hepatitis C (HCV) infection with treatment failure after sofosbuvir plus an NS5A inhibitor. There are some data for the efficacy of glecaprevir/pibrentasvir (G/P) in these patients. We performed a randomized trial of the safety and efficacy of 12 and 16 weeks of G/P, with or without ribavirin, in patients with HCV genotype 1 infection with treatment failure after sofosbuvir and an NS5A inhibitor.

METHODS

We performed a phase 3b, open-label study of patients with chronic HCV genotype 1 infection who received previous treatment with sofosbuvir plus an NS5A inhibitor. Patients without cirrhosis were randomly assigned to groups that received G/P for 12 weeks (n = 78, group A) or 16 weeks (n = 49, group B). Patients with compensated cirrhosis were randomly assigned to groups that received G/P and ribavirin for 12 weeks (n = 21, group C) or G/P for 16 weeks (n = 29, group D). The primary end point was a sustained virologic response 12 weeks after treatment. Samples collected at baseline and at time of treatment failure were sequenced for resistance-associated substitutions in NS3 and NS5A.

RESULTS

Of the 177 patients in the 4 groups, 81% were men, 79% had HCV genotype 1a infection, and 44% were black. Proportions of patients with sustained virologic response 12 weeks after treatment in groups A, B, C, and D were 90%, 94%, 86%, and 97%, respectively. The treatment failed in 13 (7.3%) patients with HCV genotype 1a infection, 6 (7.9%) in group A, 3 (6.1%) in group B, 3 (6.1%) in group C (6.1%), and 1 (3.4%) in group D. Most patients had baseline resistance-associated substitutions in NS5A. Treatment-emergent resistance-associated substitutions in NS3 and NS5A were observed in 9 and 10 patients with treatment failure, respectively. G/P was well tolerated. Ribavirin increased adverse events but did not increase efficacy.

CONCLUSIONS

In a randomized study of patients with chronic HCV genotype 1 infection who received previous treatment with sofosbuvir plus an NS5A inhibitor, 16 weeks treatment with G/P produced sustained virologic response 12 weeks after treatment in >90% of patients, including those with compensated cirrhosis. ClinicalTrials.gov, Number: NCT03092375.

Coherent electronic and nuclear dynamics in a rhodamine heterodimer-DNA supramolecular complex

Elucidating the role of quantum coherences in energy migration within biological and artificial multichromophoric antenna systems is the subject of an intense debate. It is also a practical matter because of the decisive implications for understanding the biological processes and engineering artificial materials for solar energy harvesting. A supramolecular rhodamine heterodimer on a DNA scaffold was suitably engineered to mimic the basic donor-acceptor unit of light-harvesting antennas. Ultrafast 2D electronic spectroscopic measurements allowed identifying clear features attributable to a coherent superposition of dimer electronic and vibrational states contributing to the coherent electronic charge beating between the donor and the acceptor. The frequency of electronic charge beating is found to be 970 cm^-1 (34 fs) and can be observed for 150 fs. Through the support of high level ab initio TD-DFT computations of the entire dimer, we established that the vibrational modes preferentially optically accessed do not drive subsequent coupling between the electronic states on the 600 fs of the experiment. It was thereby possible to characterize the time scales of the early time femtosecond dynamics of the electronic coherence built by the optical excitation in a large rigid supramolecular system at a room temperature in solution.

Electrostatically stabilized hybrids of carbon and maghemite nanoparticles: electrochemical study and application

Peculiar electrocatalytic properties emerged in electrostatically stabilized binary hybrids composed of maghemite nanoparticles and differently charged carbon nanomaterials.

Continuous variables logic via coupled automata using a DNAzyme cascade with feedback

The concentration of molecules can be changed by chemical reactions and thereby offer a continuous readout. Yet computer architecture is cast in textbooks in terms of binary valued, Boolean variables. To enable reactive chemical systems to compute we show how, using the Cox interpretation of probability theory, one can transcribe the equations of chemical kinetics as a sequence of coupled logic gates operating on continuous variables. It is discussed how the distinct chemical identity of a molecule allows us to create a common language for chemical kinetics and Boolean logic. Specifically, the logic AND operation is shown to be equivalent to a bimolecular process. The logic XOR operation represents chemical processes that take place concurrently. The values of the rate constants enter the logic scheme as inputs. By designing a reaction scheme with a feedback we endow the logic gates with a built in memory because their output then depends on the input and also on the present state of the system. Technically such a logic machine is an automaton. We report an experimental realization of three such coupled automata using a DNAzyme multilayer signaling cascade. A simple model verifies analytically that our experimental scheme provides an integrator generating a power series that is third order in time. The model identifies two parameters that govern the kinetics and shows how the initial concentrations of the substrates are the coefficients in the power series.

Neurocognitive status is associated with all-cause mortality among psychiatric, high-risk liver transplant candidates and recipients

OBJECTIVE

Judicious selection of potential liver transplant candidates and close monitoring of progress are essential to successful outcomes. Pretransplant psychosocial evaluations are the norm, but the relationship between psychosocial (and neurocognitive status) and longer term medical outcomes is understudied. This exploratory study sought to examine the relationship between objective measures of pretransplant psychosocial and neurocognitive status and service utilization, transplant status, and all-cause mortality.

METHODS

This retrospective chart review examined outcomes among 108 psychiatric, high-risk liver transplant candidates up to four years following initial evaluation. Predictor variables of outcomes included demographic, medical, neurocognitive, psychological, and mental health treatment variables.

RESULTS

Transplant status and neurocognitive functioning were independently associated with all-cause mortality. None of the other variables were associated with outcomes.

CONCLUSIONS

Better neurocognitive functioning in high-risk liver transplant candidates may allow for greater involvement in medical care and/or compliance with treatment recommendations. More aggressive assessment and management of neurocognitive dysfunction may improve outcomes. Objective measures identified significant psychopathology typical of liver transplant candidates but were not associated with outcomes; engagement in specialized mental health care may have attenuated this relationship. Further study is needed to better understand the relationship between psychosocial functioning and outcomes.

Nanoparticle arrays on surfaces for electronic, optical, and sensor applications

Particles in the nanometer size range are attracting increasing attention with the growth of interest in nanotechnological disciplines. Nanoparticles display fascinating electronic and optical properties as a consequence of their dimensions and they may be easily synthesized from a wide range of materials. The dimensions of these particles makes them ideal candidates for the nanoengineering of surfaces and the fabrication of functional nanostructures. In the last five years, much effort has been expended on their organization on surfaces for the construction of functional interfaces. In this review, we address the research that has led to numerous sensing, electronic, optoelectronic, and photoelectronic interfaces, and also take time to cover the synthesis and characterization of nanoparticles and nanoparticle arrays.

Chronic pain among liver transplant candidates

CONTEXT

Little systematic research has been conducted to understand pain among persons with end-stage liver disease, especially among liver transplant candidates. Appropriate pain assessment and management are important areas of consideration as treatment options are limited.

OBJECTIVE

To describe the nature of chronic pain in patients with end-stage liver disease, the extent to which pain affects daily level of functioning, and the variety and effectiveness of current treatments.

DESIGN

Retrospective chart review.

SETTING

Academic medical center in the Southeastern United States.

PATIENTS

Data were collected from 108 consecutive adult liver transplant candidates.

RESULTS

Most (77%) reported having experienced moderate levels of bodily pain within the past 24 hours. Patients with only alcoholic cirrhosis reported less pain than patients with cirrhosis due to other causes (alcoholism and hepatitis C, nonalcoholic steatohepatitis, only hepatitis C). Pain interfered significantly across all 10 functional domains assessed. Although 90% reported being prescribed a variety of analgesic agents (most commonly short-acting opioids), patients reported experiencing only 33% pain relief.

CONCLUSIONS

Pain is a significant problem among liver transplant candidates, and current pain treatments are perceived to be relatively ineffective. Increased understanding is needed to safely and effectively evaluate and treat such medically complicated patients.

Photosensitized electron transfer processes in SiO(2) colloids and sodium lauryl sulfate micellar systems: Correlation of quantum yields with interfacial surface potentials

The effectiveness of negatively charged colloidal SiO(2) particles in controlling photosensitized electron transfer reactions has been studied and compared with that of the negatively charged sodium lauryl sulfate (NaLauSO(4)) micellar system. In particular, the photosensitized reduction of the zwitterionic electron acceptor propylviologen sulfonate (PVS(0)) with tris(2,2'-bipyridinium)ruthenium(II) [Ru(bipy)(3) (2+)] as the sensitizer and triethanolamine as the electron donor is found to have a quantum yield of 0.033 for formation of the radical anion (PVS([unk])) in the SiO(2) colloid compared with 0.005 in the homogeneous system and 0.0086 in a NaLauSO(4) micellar solution. The higher quantum yields obtained with the SiO(2) colloidal system are attributed to substantial stabilization against back reaction of the intermediate photoproducts-i.e., Ru(bipy)(3) (3+) and PVS([unk])-by electrostatic repulsion of the reduced electron acceptor from the negatively charged particle surface. The binding properties of the SiO(2) particles and NaLauSO(4) micelles were investigated by flow dialysis. The results show that the sensitizer binds to both interfaces and that the SiO(2) interface is characterized by a much higher surface potential than the micellar interface ( approximately -170 mV vs. -85 mV). The effect of ionic strength on the surface potential was estimated from the Gouy-Chapman theory, and the measured quantum yields of photosensitized electron transfer were correlated with surface potential at different ionic strengths. This correlation shows that the quantum yield is not affected by surface potentials smaller than approximately -40 mV. At larger potentials, the quantum yield increases rapidly. The quantum yield obtained in the micellar system at different strengths fits nicely on the correlation curve for the colloid SiO(2) system. These results indicate that the surface potential is the dominant factor in the quantum yield improvement for PVS(0) reduction.

Factors associated with advanced liver disease in adults with alpha1-antitrypsin deficiency

BACKGROUND & AIMS

Alpha 1 -antitrypsin deficiency (AAT) is an autosomal recessive disease that affects 1 in 2500 persons and might lead to cirrhosis. Our study aim was to characterize the liver disease in AAT and identify factors associated with advanced liver disease.

METHODS

A cohort of the Alpha-1 Foundation Registry who reported liver disease was surveyed with a liver disease questionnaire to obtain information related to liver disease, liver transplantation, and AAT phenotype.

RESULTS

One hundred sixty-five of the 2175 participants in the registry reported a history of jaundice or liver disease, and 139 (84.2%) completed the questionnaire. Of these, 71.3% were PiZZ, 18.0% were PiMZ, and 5.7% did not know their phenotype. Analysis of 104 participants with a known age of diagnosis included 30 participants diagnosed with liver disease before 18 years, of whom 15 had advanced liver disease defined as liver transplantation or listed for liver transplantation. No differences in age, age at diagnosis, gender, race, phenotype, or infant jaundice were identified. Seventy-four participants were diagnosed after age 18 years, of whom 25 had advanced liver disease. In this group, advanced liver disease was associated with male gender ( P = .006) and a greater mean body mass index ( P = .01), but not with race, Pi phenotype, infant jaundice, diabetes, or hypercholesterolemia. Viral hepatitis was more frequently reported in the nontransplant group (34.7% vs 8.0%, P = .01), and the mean daily alcohol use was significantly greater in this group ( P = .04).

CONCLUSIONS

Our results suggest that male gender and obesity but not alcohol or viral hepatitis predispose to advanced liver disease in adults with AAT.

Mesenteric Venous Thrombosis in a Patient with Pancreatitis and Protein C Deficiency

Mesenteric vein thrombosis is an uncommon manifestation of hypercoagulable states. A case is reported of superior mesenteric vein (SMV) thrombosis in a patient with pancreatitis and protein C deficiency. A discussion of SMV thrombosis identification, management, and outcomes is included. The patient presented with a significant history of alcohol abuse and constant, midepigastric abdominal pain associated with nausea and vomiting. Amylase and lipase were elevated, and the patient was treated for pancreatitis. His symptoms initially responded to intravenous fluid hydration, but soon his clinical picture worsened, with increased nausea and vomiting, abdominal pain, and distension. Contrasted computed tomography of the abdomen revealed SMV thrombosis. A hypercoagulable workup revealed protein C deficiency. After a 3-month course of oral anticoagulant therapy, the SMV thrombosis resolved.

Prospective evaluation of a 3.1-mm battery-powered esophagoscope in screening for esophageal varices in cirrhotic patients

OBJECTIVE

Standard esophagogastroduodenoscopy (EGD) is costly and uses conscious sedation that cirrhotic patients may tolerate poorly. This study aimed to determine the feasibility and acceptance of unsedated esophagoscopy with an ultrathin battery-powered endoscope (BPE) in cirrhotic patients for diagnosing esophageal varices (EV).

METHODS

We first studied the prevalence of significant gastroduodenal pathology that could be missed if only esophagoscopy were performed in cirrhotic patients undergoing liver transplant evaluation. A prospective study was then done to evaluate a BPE in EV screening. Unsedated per-oral endoscopy was first done by a single endoscopist using a BPE, followed by EGD by a second endoscopist who was masked to the BPE result. A visual analog score was used to determine patient tolerance. Patients were asked about their preference for endoscopy in the future. A paired Student t test and the kappa statistic were used in the statistical analysis.

RESULTS

In the retrospective study, 199 patients were reviewed; three patients (1.5%) had gastric ulcers, and two patients (1%) had duodenal ulcers. In the prospective study, 28 cirrhotic patients (16 women) were evaluated. EV were diagnosed in 14 patients with a BPE, and 13 were confirmed by standard EGD (sensitivity and negative predictive value 100%, specificity and positive predictive value 93%, kappa = 0.93). EV were graded as large in one and small in 13 patients with a BPE, but small varices diagnosed in one patient were not confirmed on EGD. Both procedures were well tolerated by all patients. Twenty-seven of 28 patients preferred unsedated endoscopy with a BPE over EGD.

CONCLUSIONS

Unsedated endoscopy with a BPE is safe and well tolerated. The diagnostic accuracy of a BPE for diagnosing EV is the same as by EGD. Esophagoscopy with a BPE is a potential alternative to EGD for EV screening.

Prediction of esophageal varices in patients with cirrhosis

GOALS

To identify predictors of esophageal varices (EV) using available clinical, laboratory, and diagnostic imaging variables.

BACKGROUND

Patients with cirrhosis frequently undergo screening endoscopy for varices so that prophylactic therapy and/or follow up can be planned. It is unclear how often patients should be screened endoscopically for varices, and there are few data on the relationship of varices to nonendoscopic variables.

STUDY

Charts were reviewed for 247 consecutive patients with cirrhosis who underwent screening esophagogastroduodenoscopy for varices.

RESULTS

A total of 184 patients (68 women) were studied. Ninety-four patients (51%) had varices; of whom, 90 had only EV (small, n = 66; large, n = 24), 13 had EV and gastric varices, and 4 had isolated gastric varices. The distribution of EV according to the Child-Turcotte-Pugh class was as follows: A, 35%; B, 60%; and C, 69%, with roughly equal prevalence of large varices (29%, 24%, and 24%, respectively) in each class. Independent predictors of large varices were thrombocytopenia ( p = 0.02) and splenomegaly ( p = 0.04) seen using imaging. A platelet count of less than 68,000/mm 3 had the highest discriminative value for large EV with a sensitivity of 71% and a specificity of 73%. Splenomegaly had sensitivity and specificity of 75% and 58%, respectively. Using these two variables, we placed patients into one of four groups, with a risk for large varices ranging from 4% to 34%.

CONCLUSIONS

The prevalence of EV in cirrhosis increases with the severity of liver disease, as expected. Thrombocytopenia and splenomegaly are independent predictors of large EV in cirrhosis. Further prospective studies might result in a discriminating algorithm to predict which patients with cirrhosis would benefit from early or regular endoscopy to detect clinically significant varices.

Chronopotentiometry and Faradaic impedance spectroscopy as signal transduction methods for the biocatalytic precipitation of an insoluble product on electrode supports: routes for enzyme sensors, immunosensors and DNA sensors

The biocatalyzed precipitation of an insoluble product produced on electrode supports is used as an amplification path for biosensing. Enzyme-based electrodes, immunosensors and DNA sensors are developed using this biocatalytic precipitation route. Faradaic impedance spectroscopy and chronopotentiometry are used as transduction methods to follow the precipitation processes. While Faradaic impedance spectroscopy leads to the characterization of the electron-transfer resistance at the electrode, chronopotentiometry provides the total resistance at the interfaces of the modified electrodes. A horseradish peroxidase, HRP, monolayer-functionalized electrode is used to sense H(2)O(2) by the biocatalyzed oxidation of 4-chloro-1-naphthol (1), to the insoluble product benzo-4-chlorohexadienone (2). An antigen monolayer electrode is used to sense the dinitrophenyl antibody, DNP-Ab, applying an anti-antibody-HRP conjugate as a biocatalyst for the oxidative precipitation of 1 by H(2)O(2) to yield the insoluble product 2. An oligonucleotide (3) functionalized monolayer electrode is used to sense the DNA-analyte (4), that is one of the Tay-Sachs genetic disorder mutants. Association of a biotin-labeled oligonucleotide to the sensing interface, followed by the association of the avidin-HRP conjugate and the biocatalyzed precipitation of 2 leads to the amplified sensing of 4. The amount of the precipitate accumulated on the conductive support is controlled by the concentration of the respective analytes and the time intervals employed for the biocatalytic precipitation of 2. The electron-transfer resistances of the electrodes covered by the insoluble product (2) are derived from Faradaic impedance measurements, whereas the total electrode resistances are extracted from chronopotentiometric experiments. A good correlation between the total electrode resistances and the electron-transfer resistances at the conducting supports are found. Chronopotentiometry is suggested as a rapid transduction means (a few seconds). The precautions needed to apply chronopotentiometry in biosensors are discussed.

Electrochemical and quartz crystal microbalance detection of the cholera toxin employing horseradish peroxidase and GM1-functionalized liposomes

An ultrasensitive method for the detection of the cholera toxin (CT) using electrochemical or microgravimetric quartz crystal microbalance transduction means is described. Horseradish peroxidase (HRP) and GM1-functionalized liposomes act as catalytic recognition labels for the amplified detection of the cholera toxin based on highly specific recognition of CT by the ganglioside GM1. The sensing interface consists of monoclonal antibody against the B subunit of CT that is linked to protein G, assembled as a monolayer on an Au electrode or an Au/ quartz crystal. The CT is detected by a "sandwich-type" assay on the electronic transducers, where the toxin is first bound to the anti-CT-Ab and then to the HRP-GM1-ganglioside-functionalized liposome. The enzyme-labeled liposome mediates the oxidation of 4-chloronaphthol (2) in the presence of H2O2 to form the insoluble product 3 on the electrode support or the Au/quartz crystal. The biocatalytic precipitation of 3 provides the amplification route for the detection of the CT. Formation of the insulating film of 3 on the electrode increases the interfacial electron-transfer resistance, Ret, or enhances the electrode resistance, R', parameters that are quantitatively derived by Faradaic impedance measurements and chronopotentiometric analyses, respectively. Similarly, the precipitate 3 formed on the Au/quartz crystal results in a mass increase on the transducer that is reflected by a decrease in the resonance frequency of the crystal. The methods allow the detection of the CT with an unprecedented sensitivity that corresponds to 1.0 x 10(-13) M.

An N,N'-dialkyl-4,4'-bipyridinium-modified titanium-dioxide photocatalyst for water remediation--observation and application of supramolecular effects in photocatalytic degradation of pi-donor organic compounds

The photocatalytic activity of TiO2 (Degussa P-25) modified with a 4,4'-bipyridinium monolayer (V2+-TiO2) has been compared with that of conventional TiO2-P-25 by investigating the efficiency of degradation of a series of four organic model compounds with increasing pi-donor capacity (2,4-xylidine, 2,4-dimethylphenol, hydroquinone, and dimethylhydroquinone). As far as the mechanism of the first oxidation reaction is concerned, evidence for the formation of supramolecular donor-acceptor complexes with the bipyridinium units at the semiconductor surface was obtained by comparison of the Langmuir-adsorption characteristics and the efficiencies of photodegradation of the different substrates. Furthermore, the main intermediates of the photocatalytic degradation of 2,4-xylidine were identified, and the presence of 2,4-dimethylphenol indicates that the main pathway of substrate oxidation proceeds via electron transfer from the adsorbed organic substrate to the "holes" within the valence band of the photoexcited semiconductors V2+-TiO2 and TiO2. The efficiencies of photocatalytic degradation by both V2+-TiO2 and TiO2 were limited by the trapping efficiency of the conduction band electrons by molecular oxygen.

Nanoparticles as structural and functional units in surface-confined architectures

The nanoscale engineering of functional chemical assemblies has attracted recent research effort to provide dense information storage, miniaturized sensors, efficient energy conversion, light-harvesting, and mechanical motion. Functional nanoparticles exhibiting unique photonic, electronic and catalytic properties provide invaluable building blocks for such nanoengineered architectures. Metal nanoparticle arrays crosslinked by molecular receptor units on electrodes act as selective sensing interfaces with controlled porosity and tunable sensitivity. Photosensitizer/electron-acceptor bridged arrays of Au-nanoparticles on conductive supports act as photoelectrochemically active electrodes. Semiconductor nanoparticle composites on surfaces act as efficient light collecting systems, and nanoengineered semiconductor 'core-shell' nanocrystal assemblies reveal enhanced photoelectrochemical performance due to effective charge separation. Layered metal and semiconductor nanoparticle arrays crosslinked by nucleic acids find applications in the optical, electronic and photoelectrochemical detection of DNA. Metal and semiconductor nanoparticles assembled on DNA templates may be used to generate complex electronic circuitry. Nanoparticles incorporated in hydrogel matrices yield new composite materials with novel magnetic, optical and electronic properties.

Imprinting of chiral molecular recognition sites in thin TiO2 films associated with field-effect transistors: novel functionalized devices for chiroselective and chirospecific analyses

(R)- or (S)-2-Methylferrocene carboxylic acids, (R)-1 or (S)-1, (R)- or (S)-2-phenylbutanoic acid, (R)-2 or (S)-2, and (R)- or (S)-2-propanoic acid, (R)-3 or (S)-3, can be imprinted in thin TiO2 films on the gate surface of ion-sensitive field-effect transistor (ISFET) devices. The imprinting is performed by hydrolyzing the respective carboxylate TiIV butoxide complex on the gate surface, followed by washing off the acid from the resulting TiO2 film. The imprinted sites reveal chiroselectivity only towards the sensing of the imprinted enantiomer. The chiral recognition sites reveal not only chiroselectivity but also chirospecificity and, for example, the (R)-2-imprinted film is active in the sensing of (R)-2, but insensitive towards the sensing of (R)2-phenylpropanoic acid, (R)-3, which exhibits a similar chirality. Similarly, the (R)-3-imprinted film is inactive in the analysis of (R)-2. The chiroselectivity and chirospecificity of the resulting imprinted films are attributed to the need to align and fit the respective substrates in precise molecular contours generated in the cross-linked TiO2 films upon the imprinting process.

Lithium reduction of the bowl-shaped C60 fragment diindeno[1,2,3,4-defg;1',2',3',4'-mnop]chrysene: an interplay between experiment and calculation

Diindeno[1,2,3,4-defg;1',2',3',4'-mnop]chrysene (DIC) (one of the smallest symmetrical bowl-shaped fragments of C60) and its tetra-tert-butyl derivative are reduced with lithium metal to yield dianions and tetraanions. Due to the high degree of symmetry (C2v) of DIC and its derivative, their NMR spectra cannot be assigned using the standard two-dimensional NMR techniques. A novel carbon-edited NOESY method was used to complete the assignments of the neutral and dianion species, whereas the tetraanions are aided by DFT calculations for their assignment. Experimental charge-distribution patterns were obtained and match those of the calculations. An extension of the empirical approach for estimating the charge distribution from the 13C NMR spectra enables a direct comparison between experimentally derived charge-distribution data and the computed electron density in each of the lowest unoccupied molecular orbitals. The overall picture evolving from the orbital structure of DIC is presented and reflects the surface reactivity of C60.

Amplified detection of DNA and analysis of single-base mismatches by the catalyzed deposition of gold on Au-nanoparticles

A novel amplification route for DNA detection based on the deposition of gold on a 10 nm Au-colloid/avidin conjugate label acting as a 'seeding' catalyst, is described. Microgravimetric quartz-crystal-microbalance measurements are employed to transduce the catalyzed deposition of gold on the piezoelectric crystals. Three different DNA detection schemes are described: (i) analysis of a 27-base nucleic acid fragment; (ii) analysis of the entire M13phi DNA (7229 bases); and (iii) detection of a single-base mismatch in a DNA. Ultrasensitive detection of DNA is accomplished by the catalyzed deposition of gold, detection limit approximately 1 x 10(-15) M.

The decision-making value of magnetic resonance cholangiopancreatography in patients seen in a referral center for suspected biliary and pancreatic disease

OBJECTIVE

To assess the ability of MRCP to alter the differential diagnosis and to prevent diagnostic and/or therapeutic ERCP. The diagnostic accuracy of magnetic resonance cholangiopancreatography (MRCP) for biliary and pancreatic disease is well documented. Some believe MRCP may prevent diagnostic ERCP or add useful information, however there are no reports of its impact on clinical management.

METHODS

Consecutive patients referred for ERCP underwent clinic evaluation, then MRCP, and then ERCP. In Phase 1, the number of differential diagnoses and the perceived need for diagnostic ERCP were evaluated after each step by the endoscopist who performed the ERCP. In Phase 2, the process was repeated after presenting clinical information and MRCP results to different individual physicians: another endoscopist, a hepatologist, a radiologist, and a surgeon (all were blinded to ERCP results).

RESULTS

Forty patients were enrolled. Clinical contexts were jaundice (19.7%), abnormal liver enzymes (42.6%), abdominal pain (11.5%), recurrent acute pancreatitis (11.5%), and suspected complications of chronic pancreatitis (14.7%). In Phase 1, adding MRCP information to diagnostic ERCP information did not change the mean number of differential diagnoses significantly and prevented no therapeutic ERCP. In Phase 2, adding MRCP to clinical information only (without ERCP) reduced the differential diagnosis significantly for the radiologist and the surgeon only and would have prevented < or =3% of diagnostic and therapeutic ERCP for all physicians.

CONCLUSION

The value of MRCP information may be limited if patient selection is inappropriate and may differ in physicians depending on their speciality.

Electronic transduction of DNA sensing processes on surfaces: amplification of DNA detection and analysis of single-base mismatches by tagged liposomes

Tagged, negatively charged, liposomes are used to amplify DNA sensing processes. The analyses of the target DNA are transduced electrochemically by using Faradaic impedance spectroscopy, or by microgravimetric measurements with Au-quartz crystals. By one method, a probe oligonucleotide (1) is assembled on Au-electrodes or Au-quartz crystals. The formation of the double-stranded assembly with the analyte DNA (2) is amplified by the association of the 3-oligonucleotide-functionalized liposomes to the sensing interface. The target DNA is analyzed by this method with a sensitivity limit that corresponds to 1 x 10(-12) M. A second method to amplify the sensing of the analyte involves the interaction of the 1-functionalized electrode or Au-quartz crystal with the target DNA sample (2) that is pretreated with the biotinylated oligonucleotide (4). The formation of the three-component double-stranded assembly between 1/2/4 is amplified by the association of avidin and biotin-labeled liposomes to the sensing interfaces. By the secondary association of avidin and biotin-tagged liposomes, a dendritic-type amplification of the analysis of the DNA is accomplished. The analyte DNA (2) is sensed by this method with a sensitivity limit corresponding to 1 x 10(-13) M. The biotin-tagged liposomes are also used to probe and amplify single-base mismatches in an analyte DNA. The 6-oligonucleotide-functionalized Au-electrode or Au-quartz crystal was used to differentiate the single-base mismatch (G) in the mutant (5) from the normal A-containing gene (5a). Polymerase-induced coupling of the biotinylated-C-base to the double-stranded assembly generated between 6 and 5 followed by the association of avidin and biotin-tagged liposomes is used to probe the single base mismatch. The functionalized liposomes provide a particulate building unit for the dendritic amplification of DNA sensing.

Biomaterials integrated with electronic elements: en route to bioelectronics

Bioelectronics is a progressing interdisciplinary research field that involves the integration of biomaterials with electronic transducers, such as electrodes, field-effect-transistors or piezoelectric crystals. Surface engineering of biomaterials, such as enzymes, antigen-antibodies or DNA on the electronic supports, controls the electrical properties of the biomaterial-transducer interface and enables the electronic transduction of biorecognition events, or biocatalyzed transformation, on the transducers. Bioelectronic sensing devices, biosensors of tailored sensitivities and specificities, are being developed.

Electronically transduced molecular mechanical and information functions on surfaces

Supramolecular chemistry and nanotechnology, along with their use in the construction of functional assemblies and devices, have merged into a challenging field of study. The development of methodologies for the integration and interfacing of molecular building blocks with solid supports and electronic transducers is essential for this research. We address recent applications of molecular, macromolecular, and biomolecular substances in the organization of signal-activated, electronically transduced molecular architectures on electrode surfaces. Photonic, electronic, magnetic, and chemical stimuli are used to trigger the switchable functions of these systems, which demonstrate either mechanical (e.g., translocation) or computational (e.g., memory) functions and provide enlightening insight and directions for the future evolution of the field.

An integrated relay/nitrate reductase field-effect transistor for the sensing of nitrate (NO3-)

An integrated enzyme-functionalized field-effect transistor (ENFET) device for the sensing of nitrate ions is described. An aminosiloxane-functionalized gate interface is modified with N-methyl-N'-(carboxyalkyl)-4,4'-bipyridinium relay units. The complex formed between nitrate reductase and the bipyridinium units on the gate surface is crosslinked with glutaric dialdehyde to yield a stable relay-enzyme layer on the gate interface. In the presence of sodium dithionite as electron donor, the biocatalyzed reduction of nitrate to nitrite ion is stimulated. The ratio between the oxidized and reduced states of the bipyridinium sites regulates the gate potential, and is controlled by the concentration of NO3- ions in the system. The effect of the chain length tethering the N-methyl-N'-(carboxyalkyl)-4,4'-bipyridinium units to the gate surface on the biocatalyzed reduction of NO3- ions, and on the NO3- FET sensor performance is discussed. The devices that include the bipyridinium units tethered to the gate interface with methylene chain length, -(CH2)n, where n > or = 7, reveal a detection limit of 7 x 10(-5) M for nitrate and a sensitivity of 52 +/- 2 mV dec-1. The response time of the device is as low as 50 s, and the operational time of the system is ca. 85 s. We estimate the surface coverage of nitrate reductase on the gate surface to be ca. 1.2 x 10(-12) mol cm-2.

An integrated NAD+-dependent enzyme-functionalized field-effect transistor (ENFET) system: development of a lactate biosensor

An integrated NAD+-dependent enzyme field-effect transistor (ENFET) device for the biosensing of lactate is described. The aminosiloxane-functionalized gate interface is modified with pyrroloquinoline quinone (PQQ) that acts as a catalyst for the oxidation of NADH. Synthetic amino-derivative of NAD+ is covalently linked to the PQQ monolayer. An affinity complex formed between the NAD+/PQQ-assembly and the NAD+-cofactor-dependent lactate dehydrogenase (LDH) is crosslinked and yields an integrated biosensor ENFET-device for the analysis of lactate. Biocatalyzed oxidation of lactate generates NADH that is oxidized by PQQ in the presence of Ca2+-ions. The reduced catalyst, PQQH2, is oxidized by O2 in a process that constantly regenerates PQQ at the gate interface. The biocatalyzed formation of NADH and the O2-stimulated regeneration of PQQ yield a steady-state pH gradient between the gate interface and the bulk solution. The changes in the pH of the solution near the gate interface and, consequently, the gate potential are controlled by the substrate (lactate) concentration in the solution. The device reveals the detection limit of 1 x 10(-4) M for lactate and the sensitivity of 24+/-2 mV dec(-1). The response time of the device is as low as 15 s.

Lanthanide oxide-doped titanium dioxide photocatalysts: novel photocatalysts for the enhanced degradation of p-chlorophenoxyacetic acid

The photocatalytic degradation of p-chlorophenoxyacetic acid has been investigated in oxygenated aqueous suspensions of lanthanide oxide-doped TiO2 photocatalysts. Complete mineralization was achieved. The enhanced degradation is attributed to the formation of Lewis acid-base complex between the lanthanide ion and the substrate.

Biomaterial engineered electrodes for bioelectronics

A series of single-cysteine-containing cytochrome c, Cyt c, heme proteins including the wild-type Cyt c (from Saccharomyces cerevisiae) and the mutants (V33C, Q21C, R18C, G1C, K9C and K4C) exhibit direct electrical contact with Au-electrodes upon covalent attachment to a maleimide monolayer associated with the electrode. With the G1C-Cyt c mutant, which includes the cysteine residue in the polypeptide chain at position 1, the potential-induced switchable control of the interfacial electron transfer was observed. This heme protein includes a positively charged protein periphery that surrounds the attachment site and faces the electrode surface. Biasing of the electrode at a negative potential (-0.3 V vs. SCE) attracts the reduced Fe(II)-Cyt c heme protein to the electrode surface. Upon the application of a double-potential-step chronoamperometric signal onto the electrode, where the electrode potential is switched to +0.3 V and back to -0.3 V, the kinetics of the transient cathodic current, corresponding to the re-reduction of the Fe(III)-Cyt c, is controlled by the time interval between the oxidative and reductive potential steps. While a short time interval results in a rapid interfacial electron-transfer, ket1 = 20 s-1, long time intervals lead to a slow interfacial electron transfer to the Fe(III)-Cyt c, ket2 = 1.5 s-1. The fast interfacial electron-transfer rate-constant is attributed to the reduction of the surface-attracted Fe(III)-Cyt c. The slow interfacial electron-transfer rate constant is attributed to the electrostatic repulsion of the positively charged Cyt c from the electrode surface, resulting in long-range electron transfer exhibiting a lower rate constant. At intermediate time intervals between the oxidative and reductive steps, two populations of Cyt c, consisting of surface-attracted and surface-repelled heme proteins, are observed. Crosslinking of a layered affinity complex between the Cyt c and cytochrome oxidase, COx, on an Au-electrode yields an electrically-contacted, integrated, electrode for the four-electron reduction of O2 to water. Kinetic analysis reveals that the rate-limiting step in the bioelectrocatalytic reduction of O2 by the integrated Cyt c/COx electrode is the primary electron transfer from the electrode support to the Cyt c units.

Detection of single-base DNA mutations by enzyme-amplified electronic transduction

Here we describe a method for the sensitive detection of a single-base mutation in DNA. We assembled a primer thiolated oligonucleotide, complementary to the target DNA as far as one base before the mutation site, on an electrode or a gold-quartz piezoelectric crystal. After hybridizing the target DNA, normal or mutant, with the sensing oligonucleotide, the resulting assembly is reacted with the biotinylated nucleotide, complementary to the mutation site, in the presence of polymerase. The labeled nucleotide is coupled only to the double-stranded assembly that includes the mutant site. Subsequent binding of avidin-alkaline phosphatase to the assembly, and the biocatalyzed precipitation of an insoluble product on the transducer, provides a means to confirm and amplify detection of the mutant. Faradaic impedance spectroscopy and microgravimetric quartz-crystal microbalance analyses were employed for electronic detection of single-base mutants. The lower limit of sensitivity for the detection of the mutant DNA is 1 x 10-14 mol/ml. We applied the method for the analysis of polymorphic blood samples that include the Tay-Sachs genetic disorder. The sensitivity of the method enables the quantitative analysis of the mutant with no PCR pre-amplification.

Tailored chemosensors for chloroaromatic acids using molecular imprinted TiO2 thin films on ion-sensitive field-effect transistors

The SiO2 gate of an ion-sensitive field-effect transistor, (ISFET), is functionalized with a TiO2 film that includes imprinted molecular sites for 4-chlorophenoxy acetic acid, (1), or 2,4-dichlorophenoxy acetic acid, (2). The functionalized devices that include the imprinted interfaces reveal an impressive selectivity in the sensing of the imprinted substrates Na+ -1 or Na+ -2. The detection limit for Na+ -1 is (5+/-2) x 10(-4) M, which corresponds to 38 mV x dec(-1) in the concentration range of 0.5 to 6 mM. The detection limit for the analysis of Na+ -2 is (1.0+/-0.2) x 10(-5) M, which corresponds to 28 mV dec(-1) in the concentration range 0.1-9.0 mM. The equilibration time of the devices is ca. 5 min.

Liposomes labeled with biotin and horseradish peroxidase: a probe for the enhanced amplification of antigen--antibody or oligonucleotide--DNA sensing processes by the precipitation of an insoluble product on electrodes

Liposomes labeled with biotin and the enzyme horseradish peroxidase (HRP) are used as a probe to amplify the sensing of antigen-antibody interactions or oligonucleotide-DNA binding. The HRP-biocatalyzed oxidation of 4-chloro-1-naphthol (1) in the presence of H2O2, and the precipitation of the insoluble product 2 on electrode supports, are used as an amplification route for the sensing processes. The anti-dinitrophenyl antibody (DNP-Ab) is sensed by a dinitrophenyl-L-cysteine antigen monolayer associated with an Au electrode. A biotinylated anti-IgG-antibody (Fc-specific) is linked to the antigen-DNP-Ab complex, and the biotin-labeled HRP-liposomes associate with the assembly through an avidin bridge. The biocatalyzed precipitation of 2 on the electrode increases the electron-transfer resistances at the electrode-solution interface or the electrode resistance itself. The binding events of the different proteins on the electrode and the biocatalyzed precipitation of 2 on the conductive support are followed by Faradaic impedance spectroscopy or constant-current chronopotentiometry. DNP-Ab concentrations as low as 1 x 10(-11) g x mL(-1) can be detected by this method. The labeled liposomes were also used for the amplified detection of DNA 3. The oligonucleotide 4, complementary to a part of the target DNA 3 that is a model nucleic acid sequence for the Tay-Sachs genetic disorder, is assembled on an Au electrode. Hybridization of the analyte 3 followed by the association of the biotin-tagged oligonucleotide 5 yields a three-component double-stranded assembly. Sensing of the analyte 3 is amplified by the association of avidin, the labeled liposomes, and the subsequent biocatalyzed precipitation of 2 on the electrodes. The DNA 3 is detected with a sensitivity that corresponds to 6.5 x 10(-13) M. Faradaic impedance spectroscopy and chronopotentiometry were employed to follow the stepwise assembly of the systems and the electronic transduction of the detection of the analyte DNA 3.

Nanoparticle arrays on surfaces for electronic, optical, and sensor applications

Particles in the nanometer size range are attracting increasing attention with the growth of interest in nanotechnological disciplines. Nanoparticles display fascinating electronic and optical properties as a consequence of their dimensions and they may be easily synthesized from a wide range of materials. The dimensions of these particles makes them ideal candidates for the nanoengineering of surfaces and the fabrication of functional nanostructures. In the last five years, much effort has been expended on their organization on surfaces for the construction of functional interfaces. In this review, we address the research that has led to numerous sensing, electronic, optoelectronic, and photoelectronic interfaces, and also take time to cover the synthesis and characterization of nanoparticles and nanoparticle arrays.

Integration of Layered Redox Proteins and Conductive Supports for Bioelectronic Applications

Integration of redox enzymes with an electrode support and formation of an electrical contact between the biocatalysts and the electrode is the fundamental subject of bioelectronics and optobioelectronics. This review addresses the recent advances and the scientific progress in electrically contacted, layered enzyme electrodes, and discusses the future applications of the systems in various bioelectronic devices, for example, amperometric biosensors, sensoric arrays, logic gates, and optical memories. This review presents the methods for the immobilization of redox enzymes on electrodes and discusses the covalent linkage of proteins, the use of supramolecular affinity complexes, and the reconstitution of apo-redox enzymes for the nanoengineering of electrodes with protein monolayers of electrodes with protein monolayers and multilayers. Electrical contact in the layered enzyme electrode is achieved by the application of diffusional electron mediators, such as ferrocene derivatives, ferricyanide, quinones, and bipyridinium salts. Covalent tethering of electron relay units to layered enzyme electrodes, the cross-linking of affinity complexes formed between redox proteins and electrodes functionalized with relay-cofactor units, or surface reconstitution of apo-enzymes on relay-cofactor-functionalized electrodes yield bioelectrocatalytic electrodes. The application of the functionalized electrodes as biosensor devices is addressed and further application of electrically "wired" enzymes as catalytic interfaces in biofuel cells is discussed. The organization of sensor arrays, self-calibrated biosensors, or gated bioelectronic devices requires the microstructuring of biomaterials on solid supports in the form of ordered micro-patterns. For example, light-sensitive layers composed of azides, benzophenone, or diazine derivatives associated with solid supports can be irradiated through masks to enable the patterned covalent linkage of biomaterials to surfaces. Alternatively, patterning of biomaterials can be accomplished by noncovalent interactions (such as in affinity complexes between avidin and a photolabeled biotin, or between an antibody and a photoisomerizable antigen layer) to provide a means of organizing protein microstructures on surfaces. The organization of patterned hydrophilic/hydrophobic domains on surfaces, by using photolithography, stamping, or micromachining methods, allows the selective patterning of surfaces by hydrophobic, noncovalent interactions. Photoactivated layered enzyme electrodes act as light-switchable optobioelectronic systems for the amperometric transduction of recorded photonic information. These systems can act as optical memories, biomolecular amplifiers, or logic gates. The photoswitchable enzyme electrodes are generated by the tethering of photoisomerizable groups to the protein, the reconstitution of apo-enzymes with semisynthetic photoisomerizable cofactor units, or the coupling of photoisomerizable electron relay units.

Sensing of acetylcholine by a tricomponent-enzyme layered electrode using faradaic impedance spectroscopy, cyclic voltammetry, and microgravimetric quartz crystal microbalance transduction methods

A three-enzyme layered assembly on Au electrodes or Au-quartz crystals, consisting of horseradish peroxidase, HRP, choline oxidase, ChO, and acetylcholine esterase, AChE, is used to sense acetylcholine by the HRP-mediated oxidation of 3,3',5,5'-tetramethylbenzidine, TMB (1), by H2O2, and the formation of the insoluble product (2) on the respective transducers. The analyte-substrate, acetylcholine, is hydrolyzed by AChE to choline that is oxidized by ChO and O2 to yield the respective betaine and H2O2. The amounts of generated H2O2 and the resulting insoluble product on the transducers correlate with the concentration of acetylcholine in the samples. The formation of the insoluble product (2) on electrode supports is followed by faradaic impedance spectroscopy that probes the increased interfacial electron-transfer resistance upon the formation of 2, and by cyclic voltammetry that reflects electron-transfer barriers upon the formation of the precipitate. The frequency of the Au-quartz crystal decreases as a result of the accumulation of the insoluble precipitate. The amount of insoluble product formed on the transducers is controlled by the concentration of acetylcholine and by the time interval of biocatalyzed precipitation. The generation of the insoluble product provides a means to amplify the sensing processes. Acetylcholine concentrations corresponding to 1 x 10(-5) M are easily sensed by the different transducers.

An Au nanoparticle/bisbipyridinium cyclophane-functionalized ion-sensitive field-effect transistor for the sensing of adrenaline

A film consisting of polyethyleneimine (PEI), Au nanoparticles (12 +/- 1 nm) and coadsorbed cyclobis(paraquat-p-phenylene) (1) was assembled as a sensing interface on the Al2O3 insulating layer of an ion-sensitive field-effect transistor (ISFET). Adrenaline (2) was sensed by the functionalized ISFET with a detection limit of 1 x 10(-6) M. The sensing ability of the nanostructured device for the analysis of adrenaline originates from the preconcentration of the analyte in the cyclophane by pi-pi donor-acceptor interactions. Analysis of adrenaline is accomplished by the measurement of the source-drain current, Isd, or by the gate-source voltage, Vgs. The sensing device is reusable (at least 100 cycles) and exhibits high stability.

Precipitation of an insoluble product on enzyme monolayer electrodes for biosensor applications: characterization by Faradaic impedance spectroscopy, cyclic voltammetry, and microgravimetric quartz crystal microbalance analyses

Precipitation of an insoluble, insulating product on monolayer-functionalized electrodes enables the development of new electrochemical biosensors. Faradaic impedance spectroscopy and cyclic voltammetry are used to probe the electron-transfer resistance at the conductive support upon the accumulation of the insoluble product on the electrode surface. Similarly, microgravimetric quartz crystal microbalance, QCM, analyses were used to assay the formation of the precipitate on the electrode. A horseradish peroxidase, HRP, monolayer electrode is used to analyze H2O2 via the biocatalyzed oxidation of 4-chloro-1-naphthol (1) and the precipitation of the insoluble product (2). A bienzyme-layered electrode consisting of HRP and glucose oxidase, GOx, is used to sense glucose. Biocatalyzed oxidation of glucose by O2, in the presence of GOx, yields H2O2, and the generated hydrogen peroxide effects the formation of the insoluble product (2) in the presence of HRP. The insoluble product accumulated on the electrode, and the extent of the resulting electron-transfer resistance, correlated with the amounts of H2O2 or glucose, and appropriate calibration curves are extracted.