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At least 55 records · Page 3Linked to original sources
PubMed2005

Effect of taper geometries and launch angle on evanescent wave penetration depth in optical fibers.

A large penetration depth of an evanescent wave is the key to success for developing an ultra high-resolution fiber-based evanescent wave biosensor. Tapering the fiber and launching light at an angle has the potential of increasing the penetration depth of evanescent wave manifolds. The effects of tapering, launch angle and taper length of the fiber have been explored in detail using a ray-tracing model to calculate the highest possible penetration depth of the evanescent field. Evanescent wave penetration depths of the order of the size of living cells have been achieved by optimizing the parameters relating geometry of tapered fibers.

Biosensing Techniques↗
PubMed2004

Rapid detection of Bacillus anthracis spores directly from powders with an evanescent wave fiber-optic biosensor.

There currently are no rapid, sensitive tests to directly and reliably detect Bacillus anthracis spores in common powders. Traditional culture is time consuming and molecular techniques cannot directly process powders. This study describes a biosensor assay that detects B. anthracis at concentrations of 3.2 x 10(5) spores/mg or higher in spiked powders in less than 1 h with minimal sample preparation.

Anthrax↗
PubMed2002

Multiple fiber-optic dual-beam UV/Vis system with application to dissolution testing.

A system for fiber-optic probing in dissolution testing of solid pharmaceutical formulations has been constructed. The system is based on an imaging spectrometer and a charged coupled device (CCD) detector and includes 12 fiber-optic probes with a novel dual-path design. UV light was produced by a small arc deuterium lamp illuminating an optical fiber bundle. Twelve fiber-optic dipping probes were constructed with a reflection geometry. A 5 mm diameter lens was used to achieve a parallel light beam. The light passed back and forth through the flow-through cuvette defined by a sapphire window and a coated aluminium mirror. The mirror was cut in half and each segment was tilted and set at different distances from the window to obtain two separate paths with different lengths. Two receiver fibers were used for each probe to collect the transmitted light. The 24 receiver fibers from the 12 probes were bunched to a linear bundle and fed to an imaging spectrometer and the corresponding spectra were detected with a 512 x 512 pixel cooled CCD detector. The sampling interval was typically a few seconds for all probes. A software package was developed for data recording and on-line analysis. The program includes tools for multi-component analysis. The system was tested for different tablet formulations. Prednisone 50 mg tablets, normally used for control tests of dissolution baths, were followed for 3 h. Secondly, an extended release low dosage tablet was followed for 7 h resulting in a linear dissolution profile. Finally, a combination tablet containing two active drugs was tested for 60 min profiles. In the latter case, separate dissolution curves for the two active components were obtained. Future work will mainly focus on further development of the multi-component capability of the system.

Chemistry, Pharmaceutical↗
PubMedDate not supplied

Diagnosis of human coronary atherosclerosis by morphology-based Raman spectroscopy.

BACKGROUND: Recent studies have shown that chemical composition and morphology, rather than anatomy (degree of stenosis), determine atherosclerotic plaque instability and predict disease progression. Current clinical diagnostic techniques provide accurate assessment of plaque anatomy, but have limited capability to assess plaque morphology in vivo. Here we describe a technique for a morphology-based diagnosis of atherosclerosis in the coronary arteries using Raman spectroscopy that can potentially be performed in vivo using optical fiber technology. METHODS: Raman tissue spectra were collected from normal and atherosclerotic coronary artery samples in different stages of disease progression (n=165) from explanted transplant recipient hearts (n=16). Raman spectra from the elastic laminae (EL), collagen fibers (CF), smooth muscle cells (SMC), adventitial adipocytes (AA) or fat cells, foam cells (FC), necrotic core (NC), cholesterol crystals (CC), beta-carotene containing crystals (beta-C), and calcium mineralizations (CM) were used as basis spectra in a linear least squares-minimization (LSM) model to calculate the contribution of these morphologic structures to the coronary artery tissue spectra. RESULTS: We developed a diagnostic algorithm that used the fit-contributions of the various morphologic structures to classify 97 coronary artery samples in an initial calibration data set as either nonatherosclerotic, calcified plaque, or noncalcified atheromatous plaque. The algorithm was subsequently tested prospectively in a second validation data set, and correctly classified 64 (94%) of 68 coronary artery samples. CONCLUSIONS: Raman spectroscopy provides information about the morphologic composition of intact human coronary artery without the need for excision and microscopic examination. In the future, it may be possible to use this technique to analyze the morphologic composition of atherosclerotic coronary artery lesions and assess plaque instability and disease progression in vivo.

Adipocytes↗
PubMedDate not supplied

Factors influencing successful intubation in the prehospital setting.

OBJECTIVE: To explore the determinants influencing oral/nasal endotracheal intubation (OETI/NETI) and determine which cognitive, therapeutic, and technical interventions may assist prehospital airway management. DESIGN, SETTING, AND PARTICIPANTS: Prospective review of run reports and structured interviews of paramedics involved in OETI/NETI attempts were conducted in a high-volume, inner-city, advanced life support (ALS) system during an eight-month period (July 1991 to February 1992). Data were abstracted from run reports, and paramedics were asked in structured interviews to describe difficulties in OETI/NETI attempts. RESULTS: Of 236 patients studied, 88% (208) were intubated successfully. Success/failure rate was not related statistically to patients' ages (p = 0.78), medical or trauma complaint (89% vs 85%, p = 0.35), oral versus nasal route (88% vs 85%, p = 0.38), care time (scene+transport times: success, 18 minutes; failure, 20 minutes, p = 0.30), paramedic seniority (p = 0.13), or number of attempts per paramedic (p > 0.05). Increased level of consciousness (LOC) was associated with decreased success rate (p = 0.04). Paramedics reported difficulties in endotracheal intubation (ETI) attempts in 110 (46.6%) of patients. Factors reported to increase ETI difficulty were: 1) technical problems (35.6%); 2) mechanical problems (15.6%); and 3) combative patients (12.7%). CONCLUSIONS: Oral endotracheal intubation and NETI success rates identified in this study are similar to those described in the literature, although innovative strategies could be used to facilitate prehospital airway management. Many of the factors found to increase ETI difficulty could be ameliorated by the administration of paralytic agents, that is, for combative patients. Focused training in cadaver and animal labs coupled with recurrence training in the operating suites should be used on a regular basis to decrease difficulties in visualization. Interventions directed at alleviating mechanical difficulties that should be explored include new-to-the-field techniques, such as retrograde intubation, fiber-optic technology, and surgical tracheal access.

Adult↗
PubMed1989

Multicomponent fluorometric analysis using a fiber-optic probe.

Single-frequency phase-resolved fluorometry through single and bifurcated fiber-optic probes is used to quantify mixtures of spectrally similar fluorophores. Correlation coefficients from correlation plots are greater than 0.98, and standard errors of estimate are less than 0.13 microM for 80 binary mixtures. Quantification of fluorophores at up to 10:1 molar ratios with lifetime separations of less than 200 ps is possible. The simultaneous quantification of the individual components of ternary and quaternary synthetic mixtures is demonstrated. Application of phase resolution to ambient light rejection is reported also. In this case, the emission spectrum of 10 nM Rhodamine 6G is easily obtained in the presence of a fluctuating, unmodulated background.

Anthracenes↗
PubMed1990

Noninvasive method for monitoring ethanol in fermentation processes using fiber-optic near-infrared spectroscopy.

Short-wavelength near-infrared (SW-near-IR) spectroscopy (700-1100 nm) is used for the determination of ethanol during the time course of a fermentation. Measurements are performed noninvasively by means of a photodiode array spectrometer equipped with a fiber-optic probe placed on the outside of the glass-wall fermentation vessel. Pure ethanol/water and ethanol/yeast/water mixtures are studied to establish the spectral features that characterize ethanol and to show that determination of ethanol is independent of the yeast concentration. Analysis of the second-derivative data is accomplished with multilinear regression (MLR). The standard error of prediction (SEP) of ethanol in ethanol/water solutions is approximately 0.2% over a range of 0-15%; the SEP of ethanol in ethanol/yeast/water solutions is 0.27% (w/w). Results from the mixture experiments are then applied to actual yeast fermentations of glucose to ethanol. By use of a gas chromatographic method for validation, a good correlation is found between the intensity of backscattered light at 905 nm and the actual ethanol. Additional experiments show that a calibration model created for one fermentation can be used to predict ethanol production during the time course of others with a prediction error of 0.4%.

Ethanol↗
PubMed2002

Capillary-electrode alignment by an optical-fiber connector for amperometric detection in capillary electrophoresis.

We describe here an electrochemical cell ideal for routine analysis of CE-EC experiments (capillary electrophoresis coupled with electrochemical detection). The cell was modified from a fiber-optic connector, named MT, which allowed frequent change and fast alignment between a pair of 4-strand fiber ribbons. The relative standard deviations of the current response and migration time for 100 microM dopamine were, respectively, 3.7 and 0.5% in five repetitive routines of disconnecting, polishing, and assembling the CE cell. The time required for alignment of the separation capillary and the working electrode was < 10 s, once all components were assembled in an MT fiber-optic plug. These features enabled CE-EC users to polish the working electrode and reassemble the EC cell as in HPLC-EC. However, to accommodate the channel dimensions of the commercially available MT, a special order capillary with outer diameter of 125 microm is necessary at this stage.

Catecholamines↗
PubMed2005

Fiber-optic probes for in vivo Raman spectroscopy in the high-wavenumber region.

In vivo Raman spectroscopy, using fiber-optic probes is hindered by the intense background signal, which is generated in the fused-silica fibers, in the fingerprint region of the Raman spectrum (approximately 0-2000 cm(-1)). Optical filtering is necessary to obtain tissue spectra of sufficient quality. The complexity of fiber-optic probes for fingerprint Raman spectroscopy, in combination with size constraints and flexibility requirements for in vivo use have been a major obstacle in the development of in vivo diagnostic tools based on Raman spectroscopy. A setup for remote Raman spectroscopic tissue characterization in the high-wavenumber region ( approximately 2400-3800 cm(-1)) is presented. It makes use of a single, unfiltered, optical fiber for guiding laser light to the sample and for collecting scattered light and guiding it back to a spectrometer. Such a simple configuration is possible because the fused-silica core and cladding of the fiber present almost no Raman background signal at these wavenumbers. Several commercially available optical fibers were tested with respect to Raman signal background, to determine their suitability for in vivo Raman spectroscopy measurements in the high-wavenumber region. Different fiber core, cladding, and coating materials were tested. Silica core-silica clad fibers, with an acrylate coating and a black nylon jacket, proved to be one of the best candidates. In vitro measurements on brain tissue of a 6-month-old pig were obtained with a remote high-wavenumber Raman setup. They illustrate the low background signal generated in the setup and the signal quality obtained with a collection time of 1 s.

Animals↗
PubMed1996

Fluorescent fiber-optic calcium sensor for physiological measurements.

A new optical sensor based on covalent immobilization of a newly synthesized calcium-selective, long-wavelength, fluorescent indicator has been constructed, with a response dynamic range optimal for physiological measurements. Immobilization occurs via photoinitiated copolymerization of the indicator with acrylamide on the distal end of a silanized 125 micrograms diameter multimode optical fiber. The working lifetime of this sensor is limited only by photobleaching of the indicator. Due to the inherent hydrophilic nature of the acrylamide polymer, the response time of this new sensor is governed by simple aqueous diffusion of the ionic calcium. This results in sensor response times fast enough to monitor some concentration fluctuations at physiological rates. The ability to monitor calcium concentration fluctuations in a high background level of magnesium is also demonstrated with a calculated selectivity of 10(-4.5).

Biosensing Techniques↗
PubMed1999

A fiber-optic evanescent wave DNA biosensor based on novel molecular beacons.

We have prepared a novel optical fiber evanescent wave DNA biosensor using a newly developed molecular beacon DNA probe. The molecular beacons (MB) are oligonucleotide probes that become fluorescent upon hybridization with target DNA/RNA molecules. Biotinylated MBs have been designed and immobilized on an optical fiber core surface via biotin-avidin or biotin-streptavidin interactions. The DNA sensor based on a MB does not need labeled analyte or intercalation reagents. It can be used to directly detect, in real-time, target DNA/RNA molecules without using competitive assays. The sensor is rapid, stable, highly selective, and reproducible. We have studied the hybridization kinetics of the immobilized MB by changing the ionic strength of the hybridization solution and target DNA concentration. Our result shows divalent cations play a more important role than monovalent cations in stabilizing the MB stem hybrids and in accelerating the hybridization reaction with target DNA/RNA molecules. The concentration detection limit of the MB evanescent wave biosensor is 1.1 nM. The MB DNA biosensor has been applied to the analysis of specific gamma-actin mRNA sequences amplified by polymerase chain reaction.

Actins↗
PubMed2005

UV-Vis microspectroscopy: probing the initial stages of supported metal oxide catalyst preparation.

A UV-vis microspectroscopy methodology for monitoring the speciation and macrodistribution of catalyst-precursor species inside catalyst-support bodies at the initial stages of catalyst preparation has been developed. The setup is based upon optical-fiber technology and allows spatially resolved analysis of bisected catalyst bodies. The potential of this tool is demonstrated by two pore-volume impregnation studies involving Ni2+ d-d transition bands and Cr6+ charge-transfer bands.

Journal Article↗