Lateral flow immunoassays with fluorescent reporter technologies

Lateral flow assays (LFAs) are user-friendly diagnostic test devices most commonly known from the home pregnancy tests. Since their appearance in the market in 1980’s, LFAs have become well-established and products have been developed for various applications, but the most commonly sold LFAs still have the same basic features as the early products. Compared to other rapid diagnostic test (RDT) platforms, the main benefits of LFAs include inexpensive manufacturing costs, relatively fast assay development process, and the stand-alone capability of the test to be used without any instrumentation. The analytical membrane that provides the solid support for the bioassay reagents and allows the liquids to migrate through the binder lines by capillary force is almost exclusively manufactured of nitrocellulose. As the nitrocellulose remains the most widely used material, its optical properties, mechanical robustness, and chemical stability are not optimal for the RDT development. However, the established status of the nitrocellulose membrane in the RDT industry and the continuous product development suggests that the material will remain in LFAs for years to come. Typically, in LFAs, the coloured reporter particles form visible lines on the analytical membrane depending on the presence or absence of the analyte of interest. The visible lines can be interpreted visually without any instrumentation. However, the visual assessment of the assay read-out is prone to subjectivity in interpretation and can be affected by poor lighting conditions. Moreover, the visual read-out can only be used to generate a qualitative or a semi-quantitative result. The versatility of the lateral flow technology can be improved by using efficiently quantifiable reporter technologies such as fluorescent nanoparticles. However, the drawback of pursuing high analytical sensitivity and quantitative results by fluorescent reporter is the apparent need for a reader instrument. With fluorescent reporters, the optical properties of the assay membranes and sample fluids must be considered in order to achieve minimal interference to the detection of the reporters. Autofluorescence originating from the assay materials can be avoided by using the upconverting nanoparticle (UCNP) detection technology. Nevertheless, the non-analyte specific background signal can still occur from non-specific binding of the reporter particles. The aim of the thesis is to explore the opportunities arising from the use of different fluorescent reporter particles to improve the analytical sensitivities of LFAs, and to evaluate the feasibility of fluorescent reporter particles as a substitute for common visually detectable reporters. Exploiting the increased detectability of the reporter particles to improve the assay sensitivity requires careful re-optimization of the assay conditions

Gated frequency-resolved optical imaging with an optical parametric amplifier for medical applications

Implementation of optical imagery in a diffuse inhomogeneous medium such as biological tissue requires an understanding of photon migration and multiple scattering processes which act to randomize pathlength and degrade image quality. The nature of transmitted light from soft tissue ranges from the quasi-coherent properties of the minimally scattered component to the random incoherent light of the diffuse component. Recent experimental approaches have emphasized dynamic path-sensitive imaging measurements with either ultrashort laser pulses (ballistic photons) or amplitude modulated laser light launched into tissue (photon density waves) to increase image resolution and transmissive penetration depth. Ballistic imaging seeks to compensate for these {open_quotes}fog-like{close_quotes} effects by temporally isolating the weak early-arriving image-bearing component from the diffusely scattered background using a subpicosecond optical gate superimposed on the transmitted photon time-of-flight distribution. The authors have developed a broadly wavelength tunable (470 nm -2.4 {mu}m), ultrashort amplifying optical gate for transillumination spectral imaging based on optical parametric amplification in a nonlinear crystal. The time-gated image amplification process exhibits low noise and high sensitivity, with gains greater than 104 achievable for low light levels. We report preliminary benchmark experiments in which this system was used to reconstruct, spectrally upcovert, and enhance near-infrared two-dimensional images with feature sizes of 65 {mu}m/mm{sup 2} in background optical attenuations exceeding 10{sup 12}. Phase images of test objects exhibiting both absorptive contrast and diffuse scatter were acquired using a self-referencing Shack-Hartmann wavefront sensor in combination with short-pulse quasi-ballistic gating. The sensor employed a lenslet array based on binary optics technology and was sensitive to optical path distortions approaching {lambda}/100

Workshop on Advanced Technologies for Planetary Instruments, part 1

This meeting was conceived in response to new challenges facing NASA's robotic solar system exploration program. This volume contains papers presented at the Workshop on Advanced Technologies for Planetary Instruments on 28-30 Apr. 1993. This meeting was conceived in response to new challenges facing NASA's robotic solar system exploration program. Over the past several years, SDIO has sponsored a significant technology development program aimed, in part, at the production of instruments with these characteristics. This workshop provided an opportunity for specialists from the planetary science and DoD communities to establish contacts, to explore common technical ground in an open forum, and more specifically, to discuss the applicability of SDIO's technology base to planetary science instruments

Development of CCD and EM-CCD Technology for High Resolution X-Ray Spectrometry

This thesis discusses the development of Charge-Couple Device (CCD) and Electron Multiplying CCD (EM-CCD) technology for high resolution X-ray spectroscopy. Of particular interest is the spectral resolution performance of the devices alongside the optimisation of the quantum efficiency through the use of back-illuminated CCDs, thin filter technology and improved passivation techniques. The early chapters (1 through 5) focus on the background and theory that is required to understand the purpose of the work in this thesis and how semiconductors can be used as the detector of high resolution X-ray spectrometers. Chapter 6 focuses on the soft X-ray performance of three different types of conventional CCD using the PTB beamline at BESSY II. The results show that there is degradation in spectral resolution in all three devices below 500 eV due to incomplete charge collection and X-ray peak asymmetry. The Hamamatsu device is shown to degrade faster than the CCD30-11 variants and this is attributed to the thickness of the active silicon (>50 μm) in the device and also its thicker dead-layer (~75 nm) which is found by evaluating the device's soft X-ray QE). The charge loss at the back-surface generation/recombination centres is also investigated and is found to be higher in the Hamamatsu device, again due to its thicker dead-layer. Chapter 7 is an investigation of the Modified Fano Factor which aims to describe the spectral resolution degradation that is expected when an EM-CCD is used to directly detect soft X-rays. The factor is predicted analytically, modelled and then verified experimentally allowing EM-CCD performance over the soft X-ray range to be predicted with high levels of confidence. Chapter 8 is a detailed look into work completed for the phase 0 study of the off plane X-ray grating spectrometer on the International X-ray Observatory. The work includes a detailed contamination study, effective area analysis, the pointing knowledge requirement and the use of filters to minimise optical background

Innovative approaches to selective detection and remote analysis : developments in surface-enhanced raman scattering (sers)-based and separations-based fiberoptic chemical sensors

This two-part study investigates the feasibility of selective detection in remote analysis based on 1) surface-enhanced Raman scattering (SERS), and 2) separations-based fiberoptic sensing (SBFOS). For the first case, the extremely sharp spectral features of Raman scattering can sometimes allow the analysis of multicomponent samples without complicated sample pretreatment steps. Furthermore, the giant signal-enhancing effect of SERS can enable trace level detection. A solid, surface-based metallic substrate approach is taken for the development of a practical SERS technology. Various substrates are described, including silver-coated alumina, silver-coated Ti02, and silver islands. These substrates are economical and easy to fabricate with a high degree of reproducibility. Furthermore, they are readily integrated with fiberoptic sensors for remote SERS detection. Three fiberoptic SERS sensor systems are described in this work. The surface-based substrates are also applied to the detection of organic vapors. In the latter case, the high separation efficiency of capillary electrophoresis is coupled with laser-induced fluorescence (LIF) detection in the development of a fiberoptic sensor. Although LIF can offer exceptional detectability, its application to the analysis of complex samples can be difficult due to the broadband nature of fluorescence. It often requires sample pretreatment steps such as separations. In the SBFOS approach, separations can be performed remotely. Several complications are associated with the development of CE-based SBFOSs and are described in this work. Four SBFOS designs are described and applied to analysis environmentally and biomedically significant samples

Development of a microfluidic device for gaseous formaldehyde sensing = Développement d\u27un dispositif microfluidique pour la détection de formaldéhyde à l\u27état gazeux

Formaldehyd (HCHO) ist eine chemische Verbindung, die bei der Herstellung einer großen Zahl von Haushaltsprodukten verwendet wird.Charakteristisch ist seine hohe Flüchtigkeit aufgrund einer niedrigen Siedetemperatur ($T = - 19\ ℃$). Daher ist HCOH fast überall als Luftschadstoff in Innenräumen vorhanden. Die Miniaturisierung analytischer Systeme zu Handheld-Gerät hat das Potenzial, nicht nur effizientere, sondern auch empfindlichere Instrumente für die Echtzeitüberwachung dieses gefährlichen Luftschadstoffs zu ermöglichen. Die vorliegende Doktorarbeit präsentiert die Entwicklung eines Mikrofluidik-Geräts für die Erfassung von HCHO basierend auf der Hantzsch-Reaktion.Hierbei wurde der Schwerpunkt auf die Komponente für Fluoreszenzdetektion gelegt. Es wurde eine umfangreiche Literaturrecherche durchgeführt, die es erlaubt, den Stand der Technik auf dem Gebiet der Miniaturisierung des Fluoreszenzsensors zusammenzufassen. Auf Grund dieser Studie wurde ein modulares Fluoreszenzdetektionskonzept vorgeschlagen, das um einen CMOS-Bildsensor (CIS) herum entwickelt wurde. Zwei dreischichtige Fluidikzellenkonfigurationen (Konfiguration 1: Quarz - SU-8 3050 - Quarz und Konfiguration 2: Silizium - SU-8 3050 - Quarz) wurden in Betracht gezogen und parallel unter den gleichen experimentellen Bedingungen getestet. Die Verfahren der Mikrofabrikation der fluidischen Zellen wurden detailliert beschrieben, einschließlich des Integrationsprozesses der Standardkomponenten und der experimentellen Verfahren. Der CIS-basierte Fluoreszenzdetektor bewies seine Leistungsfähigkeit, eine anfängliche HCHO-Konzentration von 10 µg/L vollständig in 3,5-Diacetyl-1,4-dihydrolutidin (DDL- derivatisiert) sowohl für die Quarz- als auch für die Silizium-Fluidikzellen zu detektieren. Beide Systemewiesenein Abfragevolumen von 3,5 µL auf. Ein offensichtlich höheres Signal-Rausch-Verhältnis (SNR) wurde für die Silizium-Fluidzelle ($\text{SNR}_{\text{silicon}} = 6.1$) im Vergleich zur Quarz-Fluidzelle ($\text{SNR}_{\text{quartz}} = 4.9$) beobachtet. Die Verstärkung der Signalintensität in der Silizium-Fluidzelle ist wahrscheinlich auf den Silizium-Absorptionskoeffizienten bei der Anregungswellenlänge zurückzuführen,$a\left( \lambda_{\text{abs}} = 420\ nm \right) = 5 \bullet 10^{4}\text{cm}^{- 1}$. Dieser Koeffizient ist ungefähr fünfmal höher als der Absorptionskoeffizient bei der Fluoreszenzemissionswellenlänge $a\left(\lambda_{\text{em}} = 515\ nm \right) = 9.25 \bullet 10^{3}\text{cm}^{- 1}$. HCHO wird aufgrund seiner relativ hohen Konstanten für das Henry-Gesetz sehr schnell in ein flüssiges Reagenz aufgenommen. Somit hängt die Auswahl des molekularen Einfangverfahrens (Schwallströmung, Ringströmung oder membranbasierte Strömungswechselwirkung) von derLeistungsfähigkeit des Fluoreszenzdetektors ab. Ein vorläufiges Konzept, das auf der Verwendung einer Gas-Flüssigkeitsmembran-basierten Wechselwirkung zum ständigen Abfangen des gasförmigen HCHO basiert, wurde eingeführt. Hierzu wurden kompatible Materialien und Herstellungsmethoden identifiziert. Darüber hinaus wurden CFD-Simulationen durchgeführt, um die Mikrokanallänge unter verschiedenen hydrodynamischen Bedingungen abzuschätzen, die für eine vollständige HCHO-Derivatisierung erforderlich sind. Eine Verbesserung und Vereinfachung auf der Grundlage von sehrnempfindlichen Fluoreszenzdetektoren mit niedrigen Detektionsgrenzen könnte zukünftig basierend z. B. auf Schwallströmung oder Ringströmung möglich sein

Advanced technologies for planetary instruments

The planetary science community described instrumentation needed for missions that may go into development during the next 5 to 10 years. Then the DoD community to informed their counterparts in planetary science about their interests and capabilities, and to described the BMDO technology base, flight programs, and future directions. The working group sessions and the panel discussion synthesized technical and programmatic issues from all the presentations, with a specific goal of assessing the applicability of BMDO technologies to science instrumentation for planetary exploration.edited by J. Appleby.Clementine II: A Double Asteroid Flyby and Impactor Mission / Boain, R.J. -- The APX Spectrometer for Martian Missions / Economou, T. -- Clementine Sensor Processing System / Feldstein, A.A. -- The Ultraviolet Plume Instrument (UVPI) / Horan, D.M. -- New Technologies for UV Detectors / Joseph, C.L

Design and Characterization of a High-resolution Cardiovascular Imager

Fluoroscopic imaging devices for interventional radiology and cardiovascular applications have traditionally used image-intensifiers optically coupled to either charge-coupled devices (CCDs) or video pick-up tubes. While such devices provide image quality sufficient for most clinical applications, there are several limitations, such as loss of resolution in the fringes of the image-intensifier, veiling glare and associated contrast loss, distortion, size, and degradation with time. This work is aimed at overcoming these limitations posed by image-intensifiers, while improving on the image quality. System design parameters related to the development of a high-resolution CCD-based imager are presented. The proposed system uses four 8 x 8-cm three-side buttable CCDs tiled in a seamless fashion to achieve a field of view (FOV) of 16 x 16-cm. Larger FOVs can be achieved by tiling more CCDs in a similar manner. The system employs a thallium-doped cesium iodide (CsI:Tl) scintillator coupled to the CCDs by straight (non-tapering) fiberoptics and can be operated in 78, 156 or 234-microns pixel pitch modes. Design parameters such as quantum efficiency and scintillation yield of CsI:Tl, optical coupling efficiency and estimation of the thickness of fiberoptics to provide reasonable protection to the CCD, linearity, sensitivity, dynamic range, noise characteristics of the CCD, techniques for tiling the CCDs in a seamless fashion, and extending the field of view are addressed. The signal and noise propagation in the imager was modeled as a cascade of linear-systems and used to predict objective image quality parameters such as the spatial frequency-dependent modulation transfer function (MTF), noise power spectrum (NPS) and detective quantum efficiency (DQE). The theoretical predictions were compared with experimental measurements of the MTF, NPS and DQE of a single 8 x 8-cm module coupled to a 450-microns thick CsI:Tl at x-ray beam quality appropriate for cardiovascular fluoroscopy. The measured limiting spatial resolution (10% MTF) was 3.9 cy/mm and 3.6 cy/mm along the two orthogonal axes. The measured DQE(0) was ~0.62 and showed no dependence with incident exposure rate over the range of measurement. The experimental DQE measurements demonstrated good agreement with the theoretical estimate obtained using the parallel-cascaded linear-systems model. The temporal imaging properties were characterized in terms of image lag and showed a first frame image lag of 0.9%. The imager demonstrated the ability to provide images of high and uniform spatial resolution, while preserving and potentially improving on DQE performance at dose levels lower than that currently used in clinical practice. These results provide strong support for potential adaptation of this type of imager for cardiovascular and pediatric angiography