Acoustofluidic Micromixing Enabled Hybrid Integrated Colorimetric Sensing, for Rapid Point-of-Care Measurement of Salivary Potassium.

The integration of microfluidics with advanced biosensor technologies offers tremendous advantages such as smaller sample volume requirement and precise handling of samples and reagents, for developing affordable point-of-care testing methodologies that could be used in hospitals for monitoring patients. However, the success and popularity of point-of-care diagnosis lies with the generation of instantaneous and reliable results through in situ tests conducted in a painless, non-invasive manner. This work presents the development of a simple, hybrid integrated optical microfluidic biosensor for rapid detection of analytes in test samples.

Effectiveness of a second life(®) simulation as a teaching strategy for undergraduate mental health nursing students.

Learning may be enhanced in mental health nursing education by applying virtual reality technologies in which students may safely practice communication and assessment skills with simulated patients. The purpose of this descriptive study was to assess the effectiveness of a Second Life(®) (SL) virtual simulation as a teaching strategy for undergraduate mental health nursing students. Data were collected via a researcher-developed survey questionnaire.

A design for simulating and validating the nuss procedure for the minimally invasive correction of pectus excavatum.

Surgical planners are used to achieve the optimal outcome for a surgery, especially in procedures where a positive aesthetic outcome is the primary goal, such as the Nuss procedure which is a minimally invasive surgery for correcting pectus excavatum (PE)--a congenital chest wall deformity. Although this procedure is routinely performed, the outcome depends mostly on the correct placement of the bar. It would be beneficial if a surgeon had a chance to practice and review possible strategies for placement of the corrective bar and the associated appearance of the chest.

Stimulatory current at the edge of an inactive conductor in an electric field: role of nonlinear interfacial current-voltage relationship.

Cardiac electric field stimulation is critical for the mechanism of defibrillation. The presence of certain inactive epicardial conductors in the field during defibrillation can decrease the defibrillation threshold. We hypothesized this decrease is due to stimulatory effects of current across the interface between the inactive conductor and the heart during field stimulation.

Myocardial electrical impedance as a predictor of the quality of RF-induced linear lesions.

Production of complete (i.e. continuous and transmural) cardiac lesions by radiofrequency (RF) ablation can cure certain cardiac arrhythmias.

Comparison of optical and electrical mapping of fibrillation.

Optical recordings with transmembrane potential (Vm)-sensitive fluorescent dye, or extracellular potential (Ve) recordings are used to map spatiotemporal patterns of cardiac excitation during ventricular fibrillation (VF). While the optical and electrical methods are accepted, there has not been a test of whether they yield equivalent excitation times during VF. Times may differ since previous results indicate optical Vm interrogates deeper than Ve.

Translesion stimulus-excitation delay indicates quality of linear lesions produced by radiofrequency ablation in rabbit hearts.

Failure of cardiac antiarrhythmic ablation to block action potential conduction produces poor outcomes which lead to repeat procedures. To overcome this, an intraoperative index of the quality of an ablation lesion is needed. We hypothesized that a rise in the translesion stimulus-excitation delay (TED) can indicate a continuous, transmural, linear lesion, and that the TED is related to the path length in the viable tissue around the lesion.

Development of a system for simultaneous 31P NMR and optical transmembrane potential measurement in rabbit hearts.

The aim of this study is to develop a system for the first simultaneous measurements using 31P NMR and optical transmembrane potential-sensitive fluorescence. 31P NMR is used to evaluate 5 metabolic markers (pH, sugar phosphates, phosphocreatine, phospholipid intermediates and ATP). Action potential duration is measured with a transmembrane potential-sensitive fluorescent dye, di-4ANEPPS.

Optical mapping of V(m) and Ca(i)(2+) in a model of arrhythmias induced by local catecholamine application in patterned cell cultures.

Catecholamines are known to provoke cardiac arrhythmias, but important aspects such as localization of the arrhythmia source in multicellular tissue and exact ionic mechanisms are not well-known. In this work, a multicellular model of arrhythmias caused by local epinephrine application was developed; V (m) and Ca(i)(2+) changes at the arrhythmia source were measured using fluorescent dyes and high-resolution optical mapping. Cultured strands of neonatal rat myocytes (width approximately 0.

Use of light absorbers to alter optical interrogation with epi-illumination and transillumination in three-dimensional cardiac models.

Cardiac optical mapping currently provides 2-D maps of transmembrane voltage-sensitive fluorescence localized near the tissue surface. Methods for interrogation at different depths are required for studies of arrhythmias and the effects of defibrillation shocks in 3-D cardiac tissue. We model the effects of coloading with a dye that absorbs excitation or fluorescence light on the radius and depth of the interrogated region with specific illumination and collection techniques.

Imaging of cardiac movement using ratiometric and nonratiometric optical mapping: effects of ischemia and 2, 3-butaneodione monoxime.

Transmembrane voltage-sensitive fluorescent dyes are used to study electrical activity in hearts. Green and red fluorescence emissions from di-4-ANEPPS excited with 488 nm light indicate both transmembrane voltage changes and heart movement. We have previously shown that the ratio, green fluorescence divided by red fluorescence, indicates the transmembrane voltage without effects of movement.

Two-photon excitation of di-4-ANEPPS for optical recording of action potentials in rabbit heart.

Cardiac action potentials have been measured with single-photon excitation (SPE) of transmembrane voltage-sensitive fluorescent dye. Two-photon excitation (TPE) may have advantages for localization and depth of the tissue region from which the action potential is measured. However measurements of action potentials with SPE have not been demonstrated.

Use of translucent indium tin oxide to measure stimulatory effects of a passive conductor during field stimulation of rabbit hearts.

Biomathematical models and experiments have indicated that passive extracellular conductors influence field stimulation. Because metallic conductors prevent optical mapping under the conductor, we have evaluated a passive translucent indium tin oxide (ITO) thin-film conductor to allow mapping of transmembrane potential (V(m)) and stimulatory current under the conductor. A 1-cm ITO disk was patterned photolithographically and positioned between 0.

Cardiac optical mapping under a translucent stimulation electrode.

Major effects of stimulation on cardiac transmembrane potentials (Vm) are thought to occur under the electrode, however these have not been optically mapped due to blockage of light by electrodes. Here we optically mapped under translucent indium tin oxide (ITO) electrodes in hearts stained with transmembrane voltage sensitive fluorescent dye, di-4-ANEPPS excited at 488 nm. Emissions in wavelength bands 510-570 nm and >590 nm were similarly affected by changes in ITO transmittance due to electrochemical effects of current at the electrode interface.

Spatial localization of cardiac optical mapping with multiphoton excitation.

Depth and radius of regions interrogated by cardiac optical mapping with a laser beam depend on photon travel inside the heart. It would be useful to limit the range of depth and radius interrogated. We modeled the effects of a condensing lens to concentrate laser light at a target depth inside the heart, and near infrared excitation to increase penetration and produce two-photon absorption.

Emission ratiometry for simultaneous calcium and action potential measurements with coloaded dyes in rabbit hearts: reduction of motion and drift.

Introduction: Optical measurements of the cardiac calcium transient (Ca) and transmembrane action potential (AP) may be performed simultaneously with emission ratiometry to lessen motion artifacts and photobleaching effects. We examined changes in emission spectrum in perfused rabbit hearts coloaded with Rh237 and a green-emitting Ca dye (Fluo-4 or Oregon Green BAPTA 1) to determine wavelength bands for emission ratiometry and to test whether ratiometry reduces motion artifacts and drift.

Methods And Results: A 488-nm laser illuminated hearts while a spectrofluorometer collected fluorescence from 489 to 838 nm at 1 kHz.

Simultaneous electrical and optical mapping in rabbit hearts.

Local cardiac excitation is measured from either extracellular voltage (Ve) or optical transmembrane voltage (Vm) with fluorescent dye. We used a transparent electrode array and a laser scanner to test whether Ve and coepicentral optical Vm give equivalent excitation times during epicardial pacing and sinus beats. To help explain time differences, we estimated interrogation width/depth ratios for Ve and optical Vm with dipole and Monte Carlo models.

Modulation of triggered activity by uncoupling in the ischemic border. A model study with phase 1b-like conditions.

Objective: Triggered beats during regional ischemia may depend upon the electrical source and sink charge interactions between adjacent regions of normal and ischemic cardiac tissue that are partly controlled by electrical coupling.

Methods: To study these relationships, we modified parameters in the Luo-Rudy dynamic membrane equations to reflect physiologic conditions associated with phase 1b arrhythmias. Superthreshold delayed afterdepolarizations (DADs) formed after pacing.

Intelligent multichannel stimulator for the study of cardiac arrhythmias.

An intelligent multichannel stimulator (IMS) has been designed and built for use in a cardiac research environment. The device is capable of measuring and responding to cardiac electrophysiological phenomena in real time with carefully timed and placed electrical stimuli. The system consists of 16 channels of sense/stimulation electronics controlled by a digital signal processor (DSP) data acquisition card and a host computer and can be expanded to include more channels.