Electrochemical Determination of Fentanyl Using Carbon Nanofiber-Modified Electrodes.

In this work, we report the direct electrochemical oxidation of fentanyl using commercial screen-printed carbon electrodes (SPCEs) modified with carboxyl-functionalized carbon nanofibers (fCNFs). CNFs have surface chemistry and reactivity similar to carbon nanotubes (CNTs), yet they are easier to produce and are of a lower cost than CNTs. By monitoring the current produced during the electrochemical oxidation of fentanyl, variables such as fCNF loading, fentanyl accumulation time, electrolyte pH, and differential pulse voltammetry parameters were optimized. Under an optimized set of conditions, the fCNF/SPCEs responded linearly to fentanyl in the concentration range of 0.125-10 µM, with a limit of detection of 75 nM. The fCNF/SPCEs also demonstrated excellent selectivity against common cutting agents found in illicit drugs (e.g., glucose, sucrose, caffeine, acetaminophen, and theophylline) and interferents found in biological samples (e.g., ascorbic acid, NaCl, urea, creatinine, and uric acid). The performance of the sensor was also successfully tested using fentanyl spiked into an artificial urine sample. The straightforward electrode assembly process, low cost, ease of use, and rapid response make the fCNF/SPCEs prime candidates for the detection of fentanyl in both physiological samples and street drugs.

Nanostructured nickel oxide electrodes for non-enzymatic electrochemical glucose sensing.

Nanostructured nickel (Ni) and nickel oxide (NiO) electrodes were fabricated on Ni foils using the glancing angle deposition (GLAD) technique. Cyclic voltammetry and amperometry showed the electrodes enable non-enzymatic electrochemical determination of glucose in strongly alkaline media. Under optimized conditions of NaOH concentration and working potential (~ 0.50 V vs. Ag/AgCl), the GLAD electrodes performed far better than bare Ni foil electrodes, with the GLAD NiO electrode showing an outstanding sensitivity (4400 µA mM-1 cm-2), superior detection limit (7 nM), and wide dynamic range (0.5 µM-9 mM), with desirable selectivity and reproducibility. Based on their performance at a low concentration, the GLAD NiO electrodes were also used to quantify glucose in artificial urine and sweat samples which have significantly lower glucose levels than blood. The GLAD NiO electrodes showed negligible response to the common interferents in glucose measurement (uric acid, dopamine, serotonin, and ascorbic acid), and they were not poisoned by high amounts of sodium chloride. Graphical abstract The figures depict (A) SEM image of vertical post-GLAD NiO electrodes used for non-enzymatic electrochemical glucose monitoring, and (B) calibration plots of the three different electrodes.

An in vitro study of comparative evaluation of efficacy of electrochemically activated water as a root canal irrigant in smear layer removal.

AIM: The aim was to compare and evaluate the efficacy of electrochemically activated water (ECA) against maleic acid, Mixture of tetracycline, acid and detergent. ie; 3% doxycycline, 4.25% citric acid, and 0.5% Tween 80 detergent (MTAD), Sodium hypochlorite (NaOCl), and saline as root canal irrigants in removing the smear layer. MATERIALS AND METHODS: Twenty single canal mandibular premolars were randomly divided into five groups (n = 4), decoronated, prepared to working length, and instrumented till F3 using protaper gold rotary files. Each group was assigned a different irrigant. Saline-negative control and NaOCl-positive control. Teeth were sectioned and subjected to Scanning Electron Microscopic analysis. ECA was prepared using a custom-made apparatus having two chambers of capacity 50 ml each separated by a polymer membrane. About 40 ml of tap water was collected in each chamber. Two graphite electrodes were connected to the top of the compartments, linked to a power supply which initiates electrolysis, and the solutions obtained in anodic and cathodic compartments were collected. Statistical analysis was done using one-way ANOVA and Post hoc Tukey analysis. RESULTS: NaOCl, maleic acid, and ECA had similar smear layer removal efficacy. MTAD was less efficient than the other irrigants tested. Saline did not remove the smear layer. CONCLUSION: Electrochemically activated water has promising smear layer removal efficacy and is comparable with conventional root canal irrigants.

An impedimetric biosensor for E. coli O157:H7 based on the use of self-assembled gold nanoparticles and protein G.

Two kinds of electrochemical impedimetric biosensors for the detection of E. coli O157:H7 are described and compared. They were fabricated using self-assembled layers of thiolated protein G (PrG-thiol) on (i) planar gold electrodes and (ii) gold nanoparticles (Au NPs) modified gold electrodes. The fabrications of the biosensors were characterized using cyclic voltammetry, electrochemical impedance spectroscopy, scanning electron microscopy and atomic force microscopy techniques. The modification of the planar gold electrode by Au NPs via self-assembled monolayer of 1,6-hexadithiol as a linker molecule increased the electrochemically active surface area by about 2.2 times. The concentration of PrG-thiol and its incubation time, as well as the concentration of IgG were optimized. The Au NP-based biosensor exhibited a limit of detection of 48 colony forming unit (cfu mL-1) which is 3 times lower than that of the planar gold electrode biosensor (140 cfu mL-1). It also showed a wider dynamic range (up to 107 cfu mL-1) and sensitivity. The improved analytical performance of the Au NP-modified biosensor is ascribed to the synergistic effect between the Au NPs and the PrG-thiol scaffold. The biosensor exhibited high selectivity for E. coli O157:H7 over other bacteria such as Staphylococcus aureus and Salmonella typhimurium. Graphical abstract Schematic representations of sensor fabrication using Au NP-modified electrode (HKEC = heat- killed E. coli O157:H7).

Resistance to torsional failure and cyclic fatigue resistance of ProTaper Next, WaveOne, and Mtwo files in continuous and reciprocating motion: An in vitro study.

AIMS: The purpose of this study was to evaluate the resistance to torsional failure and cyclic fatigue resistance of ProTaper Next (PTN), WaveOne, and Mtwo files in continuous and reciprocating motion. SETTINGS AND DESIGN: Randomized control trial in a tertiary care setting. SUBJECTS AND METHODS: A total of 10 new size 25.06 taper PTN X2, 25.06 taper Mtwo files, and 25.08 taper WaveOne primary files each was selected. A custom fabricated cyclic fatigue testing device with a 70° angle of curvature and 3 mm width; curvature starting at 6 mm from the tip was used. All instruments were rotated and reciprocated till fracture occurred and time till fracture of each instrument was recorded in seconds. For torsional failure testing 5 mm tip of each file was embedded in composite resin block and uniform torsional stresses (300 rpm, 2.0 Ncm) were applied repetitively by an endodontic motor with auto stop mode until file succumbed to torsional failure. Number of load applications leading to failure was recorded. STATISTICAL ANALYSIS USED: Data were analyzed using t-test for equality of means, Pearson correlation, and ANOVA test. RESULTS: All the files showed superior resistance to cyclic fatigue in reciprocating motion when compared with continuous rotation mode. WaveOne primary files displayed maximum resistance to cyclic fatigue both in continuous and reciprocating motion. WaveOne primary files also demonstrated maximum resistance to torsional failure followed by PTN with Mtwo files exhibiting least resistance. CONCLUSIONS: Operating files in reciprocating motion enhances their cyclic fatigue resistance. WaveOne files showed maximum resistance to cyclic fatigue and torsional failure due to their cross-sectional diameter coupled M-Wire technology.

Three-dimensional evaluation of surface roughness of resin composites after finishing and polishing.

AIM: This study aims to investigate the effects of finishing and polishing procedures on four novel resin composites using three-dimensional optical profilometer. MATERIALS AND METHODS: Four composites classified according to their filler size, were selected: Filtek™ Z350 XT/Nanofill (3M™ ESPE™), Esthet-X HD/Hybrid (Dentsply Caulk), Te Econom/Microfill (Ivoclar Vivadent(®)), Tetric EvoCeram(®) /Nanohybrid (Ivoclar Vivadent(®)). Composite specimens were made in Plexiglass mold and polished with Soflex (3M ESPE), Enhance + Pogo (Dentsply Caulk). Both the systems were used according to the manufacturers' instructions, and the polished surfaces were assessed with an optical profilometer. STATISTICAL ANALYSIS USED: Kruskal-Wallis test and further pairwise comparison were performed by Mann-Whitney test. RESULTS: The smoothest surfaces for all the resin composites tested were obtained from the Mylar strip; statistically significant differences were observed among them (P = 0.001). The order of composites was ranked from the lowest to highest surface roughness; Filtek Z350 XT < Te Econom < Tetric EvoCeram < Esthet XHD. Pairwise multiple comparison with Mann-Whitney test showed Filtek Z350 to have the smoothest surface and the least with Teric EvoCeram. Among the polishing systems, Soflex showed the smoothest surface and was significantly different from Pogo (P = 0.046). CONCLUSIONS: The effectiveness of the polishing systems seems to be dependent on the material used, treatment modality and also on the filler particle size.

Malignant arrhythmia with benign tumour: fibrolipoma of the left ventricle.

We report a case of young male referred for evaluation of recent onset recurrent syncope. Inhospital electrocardiogram revealed an episode of ventricular flutter which reverted spontaneously to sinus rhythm. Transthoracic echocardiogram showed hyperechoic mass in the left ventricle. For further tissue characterization a cardiac magnetic resonance imaging was done which revealed a left ventricular mass with predominant fat content. The tumor was surgically resected. Histopathological examination confirmed the diagnosis of cardiac fibrolipoma. The patient recovered and is currently asymptomatic.

Methyl-CpG-binding protein 2 (MECP2) mutation type is associated with disease severity in Rett syndrome.

BACKGROUND: Rett syndrome (RTT), a neurodevelopmental disorder that primarily affects girls, is characterised by a period of apparently normal development until 6-18 months of age when motor and communication abilities regress. More than 95% of individuals with RTT have mutations in methyl-CpG-binding protein 2 (MECP2), whose protein product modulates gene transcription. Surprisingly, although the disorder is caused by mutations in a single gene, disease severity in affected individuals can be quite variable. To explore the source of this phenotypic variability, we propose that specific MECP2 mutations lead to different degrees of disease severity. METHODS: Using a database of 1052 participants assessed over 4940 unique visits, the largest cohort of both typical and atypical RTT patients studied to date, we examined the relationship between MECP2 mutation status and various phenotypic measures over time. RESULTS: In general agreement with previous studies, we found that particular mutations, such as p.Arg133Cys, p.Arg294X, p.Arg306Cys, 3° truncations and other point mutations, were relatively less severe in both typical and atypical RTT. In contrast, p.Arg106Trp, p.Arg168X, p.Arg255X, p.Arg270X, splice sites, deletions, insertions and deletions were significantly more severe. We also demonstrated that, for most mutation types, clinical severity increases with age. Furthermore, of the clinical features of RTT, ambulation, hand use and age at onset of stereotypies are strongly linked to overall disease severity. CONCLUSIONS: We have confirmed that MECP2 mutation type is a strong predictor of disease severity. These data also indicate that clinical severity continues to become progressively worse regardless of initial severity. These findings will allow clinicians and families to anticipate and prepare better for the needs of individuals with RTT.

Redox-gated three-terminal organic memory devices: effect of composition and environment on performance.

The performance of redox-gated organic nonvolatile memory (NVM) based on conducting polymers was investigated by altering the polymer structure, composition, and local environment of three-terminal devices with a field-effect transistor (FET) geometry. The memory function was dependent on the presence of a redox active polymer with high conducting and low conducting states, the presence of a redox counter-reaction, and the ability to transport ions between the polymer and electrolyte phases. Simultaneous monitoring of both the "write" current and "readout" current revealed the switching dynamics of the devices and their dependence on the local atmosphere. Much faster and more durable response was observed in acetonitrile vapor than in a vacuum, indicating the importance of polar molecules for both ion motion and promotion of electrochemical reactions. The major factor determining "write" and "erase" speeds of redox-gated polymer memory devices was determined to be the rate of ion transport through the electrolyte layer to provide charge compensation for the conducting polarons in the active polymer layer. The results both confirm the mechanism of redox-gated memory action and identify the requirements of the conducting polymer, redox counter reaction, and electrolyte for practical applications as alternative solid-state nonvolatile memory devices.

Multiple ventricular septal rupture after blunt trauma.

Ventricular septal rupture occurring as a result of blunt trauma is a very rare clinical condition. Compression of the heart between the sternum and the vertebral column during late diastole or isovolumetric contraction resulting in sudden increase in the intracardiac pressure is a prerequisite for its occurrence. Sudden relief of the inner pressure becomes impossible when the heart is full, thereby resulting in myocardial contusion and rupture. We report a case of a young schoolboy who presented to us with this serious disease and was successfully treated with surgical closure of the defect with a polytetrafluoroethylene patch.

Spatially resolved Raman spectroelectrochemistry of solid-state polythiophene/viologen memory devices.

A three terminal molecular memory device was monitored with in situ Raman spectroscopy during bias-induced switching between two metastable states having different conductivity. The device structure is similar to that of a polythiophene field effect transistor, but ethylviologen perchlorate was added to provide a redox counter-reaction to accompany polythiophene redox reactions. The conductivity of the polythiophene layer was reversibly switched between high and low conductance states with a "write/erase" (W/E) bias, while a separate readout circuit monitored the polymer conductance. Raman spectroscopy revealed reversible polythiophene oxidation to its polaron form accompanied by a one-electron viologen reduction. "Write", "read", and "erase" operations were repeatable, with only minor degradation of response after 200 W/E cycles. The devices exhibited switching immediately after fabrication and did not require an "electroforming" step required in many types of memory devices. Spatially resolved Raman spectroscopy revealed polaron formation throughout the polymer layer, even away from the electrodes in the channel and drain regions, indicating that thiophene oxidation "propagates" by growth of the conducting polaron form away from the source electrode. The results definitively demonstrate concurrent redox reactions of both polythiophene and viologen in solid-state devices and correlate such reactions with device conductivity. The mechanism deduced from spectroscopic and electronic monitoring should guide significant improvements in memory performance.

Room temperature synthesis of upconversion fluorescent nanocrystals.

Synthesis of nanocrystals that exhibit strong upconversion (UC) luminescence upon infrared excitation has been challenging due to the stringent control needed over experimental variables. Herein, we report a method to synthesize nanocrystals demonstrating high UC at room temperature in aqueous solution on graphene.

Self-assembly of alkylthiosulfates on gold: role of electrolyte and trace water in the solvent.

Spontaneous self-assembly of alkylthiosulfates on gold produce monolayers similar to the corresponding alkanethiols. Alkylthiosulfate self-assembly from THF solutions is inhibited in the presence of tetrabutylammonium tetrafluoroborate electrolyte. The mechanism of alkylthiosulfate self-assembly and the role of electrolyte and trace water in the solvent are investigated using open-circuit potential measurements, contact angle goniometry and redox electron transfer blocking experiments to explore the hypothesis that trace water present in the solvent facilitates monolayer formation on gold. Furthermore, the unique behavior of tetrabutylammonium tetrafluoroborate, compared to other tetrabutylammonium electrolytes, on the inhibition of alkylthiosulfate self-assembly has been explained.

Deep-tissue access with confocal fluorescence microendoscopy through hypodermic needles.

We report on the design and implementation of a gradient-index microendoscope suitable for accessing tissues deep within the body using confocal fluorescence imaging. The 350-µm diameter microendoscope has a length of 27 mm, which enables it to be inserted through a 22-gauge hypodermic needle. A prototype imaging system is demonstrated to obtain images of tissue samples at depths of ~15 mm with a lateral resolution of ~700 nm. To the best of our knowledge, this is the highest resolution and imaging depth reported for a confocal probe of these dimensions. We employ a scanning arrangement using a lensed fiber that can conveniently control the input beam parameters without causing off-axis aberrations typically present in the optical relay lenses used in galvanometer-mirror scanning systems.

Dispersion-based pulse shaping for multiplexed two-photon fluorescence microscopy.

We demonstrate selective two-photon excited fluorescence microscopy with shaped pulses produced with a simple yet efficient scheme based on dispersive optical components. The pulse train from a broadband oscillator is split into two subtrains that are sent through different amounts of glass. Beam recombination results in pulse-shape switching at a rate of 150MHz. Time-resolved photon counting detection then provides two simultaneous images resulting from selective two-photon excitation, as demonstrated in a live embryo. Although less versatile than programmable pulse-shaping devices, this novel arrangement significantly improves the performance of selective microscopy using broadband shaped pulses while simplifying the experimental setup.

Field enhanced charge carrier reconfiguration in electronic and ionic coupled dynamic polymer resistive memory.

Dynamic resistive memory devices based on a conjugated polymer composite (PPy(0)DBS(-)Li(+) (PPy: polypyrrole; DBS(-): dodecylbenzenesulfonate)), with field-driven ion migration, have been demonstrated. In this work the dynamics of these systems has been investigated and it has been concluded that increasing the applied field can dramatically increase the rate at which information can be 'written' into these devices. A conductance model using space charge limited current coupled with an electric field induced ion reconfiguration has been successfully utilized to interpret the experimentally observed transient conducting behaviors. The memory devices use the rising and falling transient current states for the storage of digital states. The magnitude of these transient currents is controlled by the magnitude and width of the write/read pulse. For the 500 nm length devices used in this work an increase in 'write' potential from 2.5 to 5.5 V decreased the time required to create a transient conductance state that can be converted into the digital signal by 50 times. This work suggests that the scaling of these devices will be favorable and that 'write' times for the conjugated polymer composite memory devices will decrease rapidly as ion driving fields increase with decreasing device size.

Electrochemically assisted self-assembly of alkylthiosulfates and alkanethiols on gold: the role of gold oxide formation and corrosion.

Electrochemically directed self-assembly of alkylthiosulfates enables the selective formation of monolayers on gold surfaces. These monolayers are identical to those formed from the corresponding alkanethiols. However, the mechanistic details of monolayer formation under electrochemical conditions as well as the role of other variables and residual water in the solvent have not been extensively studied. A systematic investigation shows that self-assembly is not a result of an outer-sphere one-electron oxidation of alkylthiosulfate. Voltammetry and electrochemical quartz crystal microbalance techniques reveal that self-assembly involving alkylthiosulfates as well as alkanethiols under oxidative conditions proceed through direct reaction with gold oxide and in some cases is accompanied by corrosion. X-ray photoelectron spectroscopy indicates that monolayers can undergo rapid exchange with molecules in solution under electrochemically directed self-assembly conditions.

Multiplexed two-photon microscopy of dynamic biological samples with shaped broadband pulses.

Coherent control can be used to selectively enhance or cancel concurrent multiphoton processes, and has been suggested as a means to achieve nonlinear microscopy of multiple signals. Here we report multiplexed two-photon imaging in vivo with fast pixel rates and micrometer resolution. We control broadband laser pulses with a shaping scheme combining diffraction on an optically-addressed spatial light modulator and a scanning mirror allowing to switch between programmable shapes at kiloHertz rates. Using coherent control of the two-photon excited fluorescence, it was possible to perform selective microscopy of GFP and endogenous fluorescence in developing Drosophila embryos. This study establishes that broadband pulse shaping is a viable means for achieving multiplexed nonlinear imaging of biological tissues.

Analysis of the influence of spherical aberration from focusing through a dielectric slab in quantitative nonlinear optical susceptibility measurements using third-harmonic generation.

The third-order nonlinear susceptibility (chi(3)) can be measured quantitatively using third-harmonic generation (THG) from two different interfaces. For the first time it is demonstrated both in experiments and theory that the magnitude of the THG signals from the two interfaces is not only determined by material properties (refractive index and chi(3)), but also by optical aberrations. It is found that this method of chi(3) determination can be applied without additional correction factors only for focusing conditions with a numerical aperture (NA)

Imaging colloidal particle induced topological defects in a nematic liquid crystal using third harmonic generation microscopy.

The nature of the third-harmonic generation (THG) process in a nematic liquid crystal is investigated for the case of tightly focused, low intensity, laser beams. Colloidal particle induced topological defects in a liquid crystal are visualized in three-dimensions using the dependence of the THG signal on both changes in non-linear susceptibility and the orientation of the liquid crystal director relative to the incident laser polarization state. We have found that the interpretation of THG images in a liquid crystal is complicated not only by the change in polarisation of the electric field as it propagates through the medium but also by anisotropic refractive index mismatch induced aberrations.