Investigation of tumor cell targeting of a dendrimer nanoparticle using a double-clad optical fiber probe

Fluorescence quantification in tissues using conventional techniques can be difficult due to the absorption and scattering of light in tissues. Our previous studies have shown that a single-mode optical fiber (SMF)-based, two-photon optical fiber fluorescence (TPOFF) probe could be effective as a minimally invasive, real-time technique for quantifying fluorescence in solid tumors. We report improved results with this technique using a solid, double-clad optical fiber (DCF). The DCF can maintain a high excitation rate by propagating ultrashort laser pulses down an inner single-mode core, while demonstrating improved collection efficiency by using a high-numerical aperture multimode outer core confined with a second clad. We have compared the TPOFF detection efficiency of the DCF versus the SMF with standard solutions of the generation 5 poly(amidoamine) dendrimer (G5) nanoparticles G5-6TAMRA (G5-6T) and G5-6TAMRA-folic acid (G5-6T-FA). The DCF probe showed three- to five-fold increases in the detection efficiency of these conjugates, in comparison to the SMF. We also demonstrate the applicability of the DCF to quantify the targeted uptake of G5-6T-FA in mouse tumors expressing the FA receptor. These results indicate that the TPOFF technique using the DCF probe is an appropriate tool to quantify low nanomolar concentrations of targeted fluorescent probes from deep tissue.

Fiber-based multispeckle detection for time-resolved diffusing-wave spectroscopy: characterization and application to blood flow detection in deep tissue

We present a technique for the measurement of temporal field autocorrelation functions of multiply scattered light with subsecond acquisition time. The setup is based on the parallel detection and autocorrelation of intensity fluctuations from statistically equivalent but independent speckles using a fiber bundle, an array of avalanche photodiodes, and a multichannel autocorrelator with variable integration times between 6.5 and 104 ms. Averaging the autocorrelation functions from the different speckles reduces the integration time in diffusing-wave spectroscopy experiments drastically, thus allowing us to resolve nonstationary scatterer dynamics with single-trial measurements. We present applications of the technique to the measurement of arterial and venous blood flow in deep tissue. We find strong deviations both of the shape and characteristic decay time of autocorrelation functions recorded at different phases of the pulsation cycle from time-averaged autocorrelation functions.

Endotracheal intubation with flexible fiberoptic bronchoscopy in patients with abnormal anatomic conditions of the head and neck

We performed a retrospective chart review to evaluate the indications for endotracheal intubation via flexible fiberoptic bronchoscopy in patients who were scheduled for surgery or who were hospitalized in the intensive care unit of our 1100-bed, tertiary care university hospital. We reviewed 9201 clinical records of anesthetic procedures during which endotracheal intubation had been performed from January to December 2002. We identified 66 patients who had been intubated with flexible fiberoptic bronchoscopy. On preanesthetic examination, 61 of these patients had been found to be poor candidates for conventional laryngoscopic intubation-51 because of abnormal head and neck anatomy and 10 because of reduced visual access to the airway (Mallampati class IV). The remaining 5 patients were intubated via flexible fiberoptic bronchoscopy after conventional intubation had failed during emergency surgery. Our study emphasizes (1) the importance of the preanesthetic examination of surgical patients, to identify those in whom conventional intubation would likely be problematic, and (2) the need to have fiberoptic bronchoscopes and an anesthesiologist or bronchoscopist skilled in their use available in operating suites and intensive care units.

Common-path optical coherence tomography with side-viewing bare fiber probe for endoscopic optical coherence tomography

All-fiber-optic common-path optical coherence tomography (OCT) using a side-viewing bare fiber probe has been demonstrated and analyzed. A bare single mode fiber tip is angle cleaved at approximately 49 degrees to enable side illumination due to total internal reflection. The bare fiber probe was inserted in an arterial tissue and a circumferential OCT scan was obtained. The research is aimed at realizing highly miniaturized monolithic probes for possible applications in miniature endoscopic OCT or intravascular OCT. The effects of the angle of the cleaved fiber on reference reflection and the sensitivity of the common-path OCT system have been studied theoretically. The angle cleaved fiber probe is also used in series with a microlens to analyze and optimize its performance in a common-path OCT system. Our research aims to explore the combined advantages of common-path OCT and extremely simplified miniature probe design and to discuss how it may greatly simplify the endoscopic OCT instrumentation eventually.

Guiding in the visible with "colorful" solid-core Bragg fibers

We report on the fabrication and characterization of solid-core all-polymer Bragg fibers consisting of a large-diameter polymethyl methylacrylate (PMMA) core surrounded by 50 alternating PMMA/Polystyrene (PS) polymer layers. By modifying the reflector layer thickness we illustrate that bandgap position can be adjusted at will in the visible. Moreover, such fibers are intensely colored in both the transmission and the outside reflection modes. Potential applications of such fibers are discussed.

Determination of penicillamine in pharmaceuticals and human plasma by capillary electrophoresis with in-column fiber optics light-emitting diode induced fluorescence detection

In this paper, a capillary electrophoresis (CE) system with in-column fiber optics light-emitting diode (LED) induced fluorescence detection was developed for the determination of penicillamine (PA). The influence of buffer concentration, buffer pH, applied voltage and injection time was systematically investigated. Optimum separation conditions were obtained with 10 mM borate buffer at pH 9.1, applied voltage 20 kV and 8 s hydrodynamic injection at 30 mbar. The detection system displayed linear dynamic range from 3.2 x 10(-7) to 4.8 x 10(-5) mol L(-1) with a correlation coefficient of 0.9991 and good repeatability (R.S.D.=2.46%). The method was applied to the determination of PA in commercial tablets and human plasma, which the recoveries of standard PA added to tablets and human plasma sample were found to be in the range of 96.26-102.68 and 91.10-99.35%, respectively. The proposed method is cheap, rapid, easy, and accurate, and can be successfully applied to the formulation analysis and bioanalysis.

Microfluidic flow rate detection based on integrated optical fiber cantilever

We demonstrate an integrated microfluidic flow sensor with ultra-wide dynamic range, suitable for high throughput applications such as flow cytometry and particle sorting/counting. A fiber-tip cantilever transduces flow rates to optical signal readout, and we demonstrate a dynamic range from 0 to 1500 microL min(-1) for operation in water. Fiber-optic sensor alignment is guided by preformed microfluidic channels, and the dynamic range can be adjusted in a one-step chemical etch. An overall non-linear response is attributed to the far-field angular distribution of single-mode fiber output.

Bioluminescence measurements in mice using a skin window

Studies of bioluminescence in living animals, such as cell-based biosensor applications, require measurement of light at different wavelengths, but accurate light measurement is impeded by absorption by tissues at wavelengths<600 nm. We present a novel approach to this problem--the use of a plastic window in the skin/body wall of mice--that permits measurements of light produced by bioluminescent cells transplanted into the kidney. The cells coexpressed firefly luciferase (FLuc), a vasopressin receptor--Renilla luciferase (RLuc) fusion protein, and a GFP2-beta-arrestin2 fusion protein. Following coadministration of two luciferase substrates, native coelenterazine and luciferin, bioluminescence is measured via the window using fiber optics and a photon counter. Light emission from the two different luciferases, FLuc and RLuc, is readily distinguishable using appropriate optical filters. When coelenterazine 400a is administered, bioluminescence resonance energy transfer (BRET) occurs between the RLuc and GFP2 fusion proteins and is detected by the use of suitable filters. Following intraperitoneal injection of vasopressin, there is a marked increase in BRET. When rapid and accurate measurement of light from internal organs is required, rather than spatial imaging of bioluminescence, the combination of skin/body wall window and fiber optic light measurement will be advantageous.

Design and development of a hand-held optical probe toward fluorescence diagnostic imaging

Near-infrared optical imaging is an emerging noninvasive technology toward breast cancer diagnosis. The optical imaging systems available to date are limited either by flexibility to image any given breast volume, patient comfort, or instrument portability. Here, a hand-held optical probe is designed and developed, 1. employing a unique measurement scheme of simultaneous multiple point illumination and collection for rapid data acquisition and minimal patient discomfort, and 2. employing a curved probe head such that it allows flexible imaging of tissue curvatures. Simulation studies are carried out on homogeneous slab phantoms (5x10x8 cc) to determine an appropriate source-detector configuration for the probe head. These design features are implemented in the development of the probe, which consisted of six simultaneous illuminating and 165 simultaneous collecting fibers, spaced 0.5 cm apart on a 5x10 sq-cm probe head. Simulation studies on 3-D slab and curved phantoms demonstrate an increase in the total area of predicted fluorescence amplitude and overall signal strength on using simultaneous multiple point sources over a single point source. The probe is designed and developed such that on coupling with a detection system in the future, the hand-held probe based imager can be clinically assessed toward cancer diagnostic imaging.

Ex vivo measurement of lumbar intervertebral disc pressure using fibre-Bragg gratings

Methods were developed to measure intervertebral disc pressure using optical fibre-Bragg gratings (FBGs). The FBG sensor was calibrated for hydrostatic pressure in a purpose-built apparatus and the average sensitivity was determined to be -5.7 +/- 0.085 pm/MPa (mean +/- SD). The average coefficient of determination (r(2)) for the calibration data was 0.99, and the average hysteresis of the sensor was 2.13% of full scale. The FBG was used to measure intradiscal pressure response to compressive load in five lumbar functional spine units. The pressure measured by the FBG sensor varied linearly with applied compressive load with coefficients of determination ranging from 0.84 to 0.97. The FBG sensor's sensitivity to compressive load ranged from 0.702 +/- 0.043 kPa/N (mean +/- SD) in a L1-L2 specimen, to 1.07 +/- 0.069 kPa/N in a L4-L5 specimen. These measurements agree with those of previous studies in lumbar spines. Two strain gauge pressure sensors were also used to measure intradiscal pressure response to compressive load. The measured pressure sensitivity to load ranged from 0.251 kPa/N (L4-L5) to 0.850 kPa/N (L2-L3). The average difference in pressure sensitivity to load between Sensors 1 and 2 was 12.9% of the value for Sensor 1, with a range from 1.1% to 20.4%, which suggests that disc pressure was not purely hydrostatic. This may have contributed to the difference between the responses of the FBG and strain gauge sensors.

All-normal-dispersion femtosecond fiber laser with pulse energy above 20 nJ

We report a study of the scaling and limits to pulse energy in an all-normal-dispersion femtosecond fiber laser. Theoretical calculations show that operation at large normal cavity dispersion is possible in the presence of large nonlinear phase shifts, owing to strong pulse shaping by spectral filtering of the chirped pulse in the laser. Stable pulses are possible with energies of tens of nanojoules. Experimental results from Yb-doped fiber lasers agree with the trends of numerical simulations. Stable and self-starting pulses are generated with energies above 20 nJ, and these can be dechirped to <200 fs duration. Femtosecond pulses with peak powers near 100 kW are thus available from this simple and practical design.

Nanoparticle-mediated coupling of light into a nanowire

We show that a nanoparticle can serve as an efficient antenna for coupling of visible light into propagating plasmons of an Ag nanowire. For long wires, the coupling is maximal for incident light polarized perpendicular to the nanowire. For sub-10-mum nanowires, the polarization corresponding to maximum emission from the ends of the nanowire was found to be strongly dependent on the nanowire geometry and position of the vicinal nanoparticle. This nanoparticle antenna-based approach offers a potential strategy for optimizing plasmon coupling into nanoscale metallic waveguides.

Direct observation of surface mode excitation and slow light coupling in photonic crystal waveguides

A scanning near-field optical microscope (SNOM) is used to systematically study the properties of guided modes in linear and slow-light regimes of silicon-on-insulator (SOI)-based photonic crystal waveguides (PhCWs) with different terminations of the photonic lattice. High quality SNOM images are obtained for light at telecom wavelengths propagating in the PhCW, demonstrating directly, for the first time to our knowledge, drastic widening of the PhCW guided mode in the slow-light regime and excitation of surface waves at the PhCW interface along with their feeding into the guided mode for the lattice terminations corresponding to significantly reduced coupling loss.

In vivo ultrasound real-time motion of the cervical spine during intubation under manual in-line stabilization: a comparison of intubation methods

BACKGROUND AND OBJECTIVE

In emergency trauma situations, manual in-line stabilization of the cervical spine is recommended to reduce cervical spine movement during intubation. The aim of this study was to compare the effect of manual in-line stabilization during different intubation techniques on three-dimensional cervical spine movements and times to intubation.

METHODS

Forty-eight subjects without any history of trauma, inflammatory or degenerative disorder of the cervical spine were randomly grouped, regardless of gender or age. All underwent elective surgery under general anaesthesia. Under manual in-line stabilization, laryngeal intubation with Macintosh laryngoscope, intubating laryngeal mask airway, fibre-endoscopic oral intubation and fibre-endoscopic nasal intubation was performed. During the intubation process, cervical three-dimensional motion was detected by an ultrasound real-time motion analysis system and intubation times were measured.

RESULTS

Cervical spine range in the extension/flexion direction of orolaryngeal intubation with Macintosh (17.57 +/- 8.23 degrees ) showed significantly more movement than using the intubating laryngeal mask airway (4.60 +/- 1.51 degrees ) and fibreoptic procedures. Intubating laryngeal mask airway was significantly different than the fibreoptic intubation techniques. There was also a significant difference between oral (3.61 +/- 2.25 degrees ) nasal and (5.88 +/- 3.11 degrees ) fibreoptic intubation. Times to intubation all differed significantly (P < 0.05) for the Macintosh laryngoscope (27.25 +/- 8.56 s) and for the intubating laryngeal mask airway (16.5 +/- 9.76 s). Fibreendoscopic laryngoscopic oral (52.91 +/- 56.27 s) and nasal (82.32 +/- 54.06 s) intubation resulted in further prolongation of the times to intubation.

CONCLUSIONS

The intubating laryngeal mask airway with manual in-line stabilization is a potentially useful adjunct to intubation of patients with potential cervical spine injury, if there are no contraindications to these methods. These results predict that fibreoptic procedures may be a safe instrument for airway management in patients with potential cervical spine injuries; however, the main disadvantages are the longer intubation times.

Fiberoptic system for recording dendritic calcium signals in layer 5 neocortical pyramidal cells in freely moving rats

Calcium influx into the dendritic tufts of layer 5 neocortical pyramidal neurons modifies a number of important cellular mechanisms. It can trigger local synaptic plasticity and switch the firing properties from regular to burst firing. Due to methodological limitations, our knowledge about Ca2+ spikes in the dendritic tuft stems mostly from in vitro experiments. However, it has been speculated that regenerative Ca2+ events in the distal dendrites correlate with distinct behavioral states. Therefore it would be most desirable to be able to record these Ca2+ events in vivo, preferably in the behaving animal. Here, we present a novel approach for recording Ca2+ signals in the dendrites of populations of layer 5 pyramidal neurons in vivo, which ensures that all recorded fluorescence changes are due to intracellular Ca2+ signals in the apical dendrites. The method has two main features: 1) bolus loading of layer 5 with a membrane-permeant Ca2+ dye resulting in specific loading of pyramidal cell dendrites in the upper layers and 2) a fiberoptic cable attached to a gradient index lens and a prism reflecting light horizontally at 90 degrees to the angle of the apical dendrites. We demonstrate that the in vivo signal-to-noise ratio recorded with this relatively inexpensive and easy-to-implement fiberoptic-based device is comparable to conventional camera-based imaging systems used in vitro. In addition, the device is flexible and lightweight and can be used for recording Ca2+ signals in the distal dendritic tuft of freely behaving animals.

Monitoring ibuprofen release from multiparticulates: in situ fiber-optic technique versus the HPLC method: a technical note

The objective of the study was to produce rapidly dissolving formulations of the poorly water-soluble drug repaglinide using an innovative new technology, ultra-rapid freezing (URF), and to investigate the influence of excipient type on repaglinide stability. Repaglinide compositions containing different types and levels of excipients and different drug potencies (50%–86%) were produced by the URF technology. Repaglinide/excipient solutions were frozen on a cryogenic substrate, collected, and lyophilized to form a dry powder. Surfactants, including sodium dodecyl sulfate, and alkalizing agents such as diethanolamine (DEA) and tromethamine (TRIS) were incorporated into the compositions. Forced degradation of repaglinide was conducted under stressed conditions (eg, elevated temperature, exposure to peroxide) to determine the stability of the drug in such environments. The solubility of repaglinide increased as a function of increasing pH; therefore, incorporation of an alkalizing agent into the URF formulations increased the drug's solubility. Drug instability resulted when the drug was exposed to pH values above 9.0. URF formulations containing alkalizing agents showed no degradation or spontaneous recrystallization in the formulation, indicating that increased stability was afforded by processing. URF processing created nanostructured drug/excipient particles with higher dissolution rates than were achieved for unprocessed drug. Alkalizing agents such as TRIS and DEA, present at levels of 25% to 33% wt/wt in the formulations, did not cause degradation of the drug when processed using URF. URF processing, therefore, yielded fast-dissolving formulations that were physically and chemically stable, resistant to alkali degradation or spontaneous recrystallization in the formulation.

Management of the Airway in Patients Undergoing Cervical Spine Surgery

The perioperative management of the airway in patients with cervical spine disease requires careful consideration. In an observational prospective cohort study, we assessed the preoperative factors that may have influenced the anesthesiologists' choice for the technique of intubation and the incidence of postoperative airway complications. We recorded information from 327 patients: mean (+/-SD) age 51+/-15 year, 138 females and 189 males, for anterior surgical approach (n=195) and posterior (n=132). The technique of intubation used was awake fiberoptic bronchoscopy (FOB) in 39% (n=128), asleep FOB 32% (n=103), asleep laryngoscopy 22% (n=72), and other asleep 7% (n=24). Awake FOB was predominately chosen for intubating patients with myelopathy (45%), unstable/fractured spine (73%), and spinal stenosis (55%) but patients with radiculopathy had more asleep FOB (49%) (P<0.001). There was no association between method of intubation and postoperative airway complications. Acute postoperative airway obstruction occurred in 4 (1.2%) patients requiring reintubation. The technique of management of the airway for cervical spine surgery varied considerably among the anesthesiologists, although the choice was not associated with postoperative airway complications.

Subsurface and transcutaneous Raman spectroscopy and mapping using concentric illumination rings and collection with a circular fiber-optic array

Different spatial separations between an illumination ring and a bundle of 50 collection fibers focused to collect light in the center of the ring were used to investigate the recovery of subsurface Raman spectra. The depth of Raman signal recovery and the preservation of spatial information in the recovered signal were investigated using polymer blocks stacked in different geometries. The illumination rings were then combined into a single data set to increase variation in the signal. Multivariate data analysis was used to recover the Raman spectra of the subsurface component. The Raman spectrum of a Delrin target was recoverable at depths up to 22.6 mm of overlying Teflon. Spatial information was lost at approximately 6.5 mm below the Teflon surface. The same protocols were used to recover canine bone spectra transcutaneously at depths up to 5 mm below the skin's surface. The recovered bone spectra were validated by exposed bone measurements.

Case report: Use of two balloon-tipped catheters during thoracoscopic repair of a type C tracheoesophageal fistula in a neonate

PURPOSE

To describe a novel airway management technique for thoracoscopic repair of a type C tracheoesophageal fistula (TEF) in a neonate.

CLINICAL FEATURES

A full-term neonate with a type C TEF presented for thoracoscopic repair. The fistula was at the level of the carina, making its isolation from positive pressure ventilation using traditional techniques difficult. In addition, non-ventilation of the right lung was required. The use of two Fogarty type balloon-tipped embolectomy catheters placed alongside the endotracheal tube successfully achieved the goal of blocking ventilation of the fistula and the right lung. The use of fibreoptic bronchoscopy greatly facilitated placement of the blockers. The patient made an uneventful recovery.

CONCLUSION

Placing two balloon-tipped blockers, one in the TEF and the other in the right mainstem bronchus, is a viable technique for thoracoscopic fistula repair when the fistula is at or very close to the level of the carina.

Planar fiber-optic chips for broadband spectroscopic interrogation of thin films

A planar fiber-optic chip (FOC) has been developed using side-polished optical fibers and characterized for broadband absorbance and fluorescence detection of molecular films. FOC technology combines the sensitivity of an attenuated total reflection (ATR) element with the ease of use of fiber-optic-based spectrometers and light sources to create an improved platform for spectroscopic analysis of molecular adsorbates. A multi-mode optical fiber (core diameter = 50 mum, numerical aperture = 0.22, stepped refractive index profile) mounted in a glass V-groove block was side-polished to create a planar platform that allows access to the evanescent field escaping from the fiber core. For this generation of FOC technology, the exposed evanescent field has an interaction length of approximately 17.2 mm. The FOC platform was independently characterized through measurements of thin-film and bulk absorbing samples. The device performance was compared to the existing ATR technology and methods for increasing sensitivity of the FOC were investigated and validated. Additionally, we have demonstrated the ability of the FOC to both evanescently excite and collect fluorescence through guided modes of the optical fiber for a surface-confined luminescent semiconductor nanoparticle film (4 nm diameter, ligand capped, CdSe core). The FOC described here with a supported planar interface can facilitate the use of conventional planar deposition technologies and provide a robust planar platform that is amenable for incorporation into various sensor technologies.

A simple confocal fibre-optic laser method for intraocular lens power measurement

PURPOSE

To develop novel confocal fibre-optic laser method (CFOLM) for accurate and objective measuring of the dioptric power of both positive and negative intraocular lenses (IOLs).

METHODS

The CFOLM principle of operation is based on a simple apertureless single-mode fibre laser confocal design. The key element is a single-mode fibre coupler that serves simultaneously as a point light source (3-5 microm fibre diameter) used for the formation of a collimated Gaussian beam, and as a confocal point receiver that is highly sensitive to spatial displacements of the focused backreflectance laser emission. The basic CFOLM systems include IOL testing set-ups for the measurement of both positive and negative IOLs.

RESULTS

The CFOLM designs provide high accuracy (

CONCLUSIONS

The presented IOL power testing method offers a simple, accurate, objective, quick, and relatively inexpensive approach for dioptric power measurement of positive and negative IOLs. It provides an independent source of IOL power measurement data and information for evaluating the effectiveness and safety of novel IOL products.

Collapse

Key Words

• intraocular lens dioptric power
• confocal fibre-optic laser method
• single-mode fibre coupler

Collapse

MESH Headings

• Diagnostic Techniques, Ophthalmological/instrumentation
• Equipment Design
• Fiber Optic Technology/methods
• Humans
• Lasers
• Lenses, Intraocular
• Optics and Photonics

Collapse

Grants

• FD999999 Intramural FDA HHS

Collapse

Tracheoscopy assisted repair of tracheo-esophageal fistula (TARTEF): a 10-year experience

BACKGROUND

Fiberoptic tracheoscopy assisted repair of tracheoesophageal fistula (TARTEF) has been reported to be useful for the surgeon with regards to identification of the fistula and proper fistula ligation. The aim of this article is to report our 10-year experience using TARTEF with intermittent positive pressure ventilation (IPPV) during tracheoesophageal fistula (TEF) repair in newborns.

METHODS

With ethical committee approval, we included all patients undergoing TARTEF from 1995-2005. Variables of interest were (1) respiratory deterioration caused by gastric inflation because of IPPV during surgery and endoscopy; (2) detection of additional airway anomalies; (3) success of intubation of the fistula; (4) other side effects or adverse events. Data are given in median and range.

RESULTS

Forty-seven neonates with TARTEF were included. Mean gestational age was 37 weeks (31-42) and mean weight was 2.5 kg (1.1-3.8). The patients were intubated with tracheal tubes size 2.5-3.5 mm ID. Appropriately sized fiberoptic bronchoscopes with an outer diameter of 2.0, 2.4 and 2.8 mm were used; passed through the lumen of the tracheal tube (TT) thereby requiring the use of IPPV to ensure adequate ventilation. No respiratory deterioration was noted as a consequence of intraoperative fiberoptic manipulation within the trachea or because of gastric hyperinflation with IPPV. In all patients, the TEF was successfully penetrated with the fiberscope and this clearly helped the surgeon to rapidly identify and dissect the fistula. In two patients a tracheal bronchus was identified. In two patients accidental extubation occurred during endoscopic confirmation of successful fistula repair.

CONCLUSIONS

While fiberoptic TARTEF through the tracheal tube with IPPV did expedite and facilitate surgery, it did not cause clinically relevant impairment of ventilation. Careful manipulation during fiberoptic assessment is required to avoid tube displacement.