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We are pleased to provide downloads, or links, to a number of papers on aerosol or bioaerosol fluorescence detection which were produced using Vertilon's PhotoniQ DAQs.

 

Continuous Flow Real-Time PCR Device Using Multi-Channel Fluorescence Excitation and Detection 

Andrew C. Hatch, Tathagata Ray, Kelly Lintecum, Cody Youngbull

Lab on a Chip, Issue 3 2014

Copyright ©2014 Royal Society of Chemistry

 

High throughput automation is greatly enhanced using techniques that employ conveyor belt strategies with un-interrupted streams of flow. We have developed a 'conveyor belt' analog for high throughput real-time quantitative Polymerase Chain Reaction (qPCR) using droplet emulsion technology. We developed a low power, portable device that employs LED and fiber optic fluorescence excitation in conjunction with a continuous flow thermal cycler to achieve multi-channel fluorescence detection for real-time fluorescence measurements. Continuously streaming fluid plugs or droplets pass through tubing wrapped around a two-temperature zone thermal block with each wrap of tubing fluorescently coupled to a 64-channel multi-anode PMT. This work demonstrates real-time qPCR of 0.1-10 µL droplets or fluid plugs over a range of 7 orders of magnitude concentration from 1 x 10^1 to 1 x 10^7. The real-time qPCR analysis allows dynamic range quantification as high as 1 x 10^7 copies per 10 µL reaction, with PCR efficiencies within the range of 90-110% based on serial dilution assays and a limit of detection of 10 copies per rxn. The combined functionality of continuous flow, low power thermal cycling, high throughput sample processing, and real-time qPCR improves the rates at which biological or environmental samples can be continuously sampled and analyzed.

 

Classification and Selective Collection of Individual Aerosol Particles Using Laser-Induced Fluorescence 

Vasanthi Sivaprakasam, Timothy Pletcher, John E. Tucker, Alan L. Huston, Joseph McGinn, David Keller, and Jay D. Eversole

Applied Optics, Volume 48, Issue 4, pages B126-B136

Copyright ©2009 Optical Society of America

 

Described is the development and performance evaluation of a system for optical interrogation, subsequent selection, and collection of individual aerosol particles entrained in an inlet air stream. Elastic scatter and laser-induced fluorescence obtained from single particles on-the-fly provide compositional information for classification criteria. Individual particles could then be selectively electrically charged and captured to a conductive substrate with an electric potential. The optical subsystem also includes a novel two-beam velocimeter to provide accurate downstream timing. Good overall quantitative performance values are reported for particles in the size range of 1-8 micron at mean rates up to 4 kHz.

 

Linear and Non-Linear Spectroscopy of Microparticles: Basic Principles, New Techniques and Promising Applications 

Richard K. Chang and Yong-Le Pan

Faraday Discussions, 2008, 137, 9-36

Copyright ©2009 Royal Society of Chemistry

 

The basic principles of whispering gallery modes (WGMs) and their relationship with electromagnetic theory are presented. To simplify the mathematics, we only discuss an example from a 2-d case of light illumination perpendicular to the fiber axis. This 2-d example has relevance to semiconductor circular disk lasers, nonlinear optics in toroids, fibers and spheres at the tip of a fiber. The internal and near-field distribution of a WGM are graphically plotted to give the reader a chance to get a physical understanding of the spatial distribution as well as spectral distribution of WGMs. Several new techniques that enable the measurements of: (1) nanometer changes in the cladding diameter over a centimeter length of fiber; (2) some aspects of the morphology of micro-particles by elastic scattering; and (3) biochemical reactions at the interface of liquid media with a sphere at the end of a fiber. A few interesting nonlinear optical experimental results pertaining to stimulated Raman scattering (SRS) are touched upon. We present some preliminary results for promising applications in the area of bioaerosols. These include ambient aerosol characterization and identification with elastic scattering, fluorescence spectroscopy, and other optical and/or biochemical identifiers.

 

Multi-anode PMT Makes Possible the Detection, Discrimination, Enrichment, and Deposition of Bioaerosols On-the-Fly

Yong-le Pan, Richard K. Chang

Hamamatsu Corporation Applications

Copyright ©2006 Yong-le Pan and Richard K. Chang

 

An approach based on the analysis of UV laser-induced fluorescence spectra (UV-LIF), has resulted in instruments that can continually and rapidly discriminate bio-threat-like aerosols from many ambient aerosols. However, this approach struggles with specific identification and produces high false alarm rates, especially in instruments that rely on only two or three fluorescence bands. To overcome these limitations, a combined method has been devised, in which the dispersed spectroscopy of the UV-LIF signal is used as a first-stage discriminator to prescreen the background aerosol particles and rapidly get rid of interfering aerosols, while specific biochemical technology is used to identify suspect aerosols with high accuracy for bioaerosol detection and characterization.

 

Selective Deflection and Localization of Flowing Aerosols onto a Substrate

Matt Frain, David P. Schmidt, Yong-Le Pan, Richard K. Chang

Aerosol Science and Technology, 40:218–225, 2006

Copyright ©2006 American Association for Aerosol Research

 

Pulsed airflow cued by the fluorescence spectrum of a particular aerosol can be used to distinguish and deflect particles of biological origin out of an aerosol stream, permitting concentration of these particles for subsequent analysis. However, these high velocity pulses of air have an inherent tendency to scatter particles, confounding efforts to concentrate these deflected particles for analysis. The ability to concentrate large numbers of biological particles into a small area on a collection substrate is particularly important for more species-specific techniques such as Raman and FTIR (Fourier Transform Infra-Red) spectroscopy, which require long integration times due to their weak signal strength. Here, a simple method is developed for deflecting and localizing particles after classification by a pulsed airflow. The concept is both modelled and experimentally tested. A specially designed funnel is used to localize the scattered particles onto an area of substrate as small as 1 mm in diameter. Computational fluid dynamics simulations were performed to investigate the interaction of the pulsed airflow with the deflected particles and the localizing funnel, in order to gain insight into design parameters and operating conditions that affect the efficiency of this technique. The results show that the combination of pulsed airflow with a localizing funnel effectively deflects and localizes the concentrated bioaerosol onto a small area of substrate or an opening of a microfluidic cell.

 

LIBS Leaves the Lab for Field Work in Industry and Defense 

Kathy Kincade

Laser Focus World, Volume 39, Issue 8, August 2003

 

Laser-induced breakdown spectroscopy (LIBS) has experienced a surge of growth in recent years, particularly for field-based applications. The development of new laser sources and portable instrumentation is helping LIBS find a niche in everything from environmental monitoring and materials analysis to homeland security, medical diagnostics, and even space-based research. In addition, the emergence of the echelle spectrometer and low-cost broadband spectrometers both of which afford higher spectral coverage and resolution has opened up new applications in molecular and biological matter detection and sorting of metals and plastics.

 

290 and 340 nm UV LED Arrays for Fluorescence Detection from Single Airborne Particles

Kristina Davitt, Yoon-Kyu Song, William R. Patterson III, Arto V. Nurmikko, Maria Gherasimova, Jung Han,  Yong-Le Pan, Richard K. Chang

Optics Express 9548, Volume 13, Number 23, November 14, 2005

Copyright ©2005 OSA

 

A compact system is demonstrated, incorporating a 32-element linear array of ultraviolet (290 nm and 340 nm) light-emitting diodes (LEDs) and a multi-anode photomultiplier tube, to the in-flight fluorescence detection of aerosolized particles, here containing the biological molecules tryptophan and NADH. This system illustrates substantial advances in the growth and fabrication of new semiconductor UV light emitting devices and an evolution in packaging details for LEDs tailored to the bio-aerosol warning problem. Optical engineering strategies are employed which take advantage of the size and versatility of light-emitting diodes to develop a truly compact fluorescence detector.

 

Separating Hazardous Aerosols from Ambient Aerosols: Role of Fluorescence-Spectral Determination, Aerodynamic Deflector and Pulse Aerodynamic Localizer (PAL)

Yong-le Pan, Patrick J. Cobler, Scott A. Rhodes, Justin Halverson, Richard K. Chang

Proceedings of SPIE Vol. 5990 59900Y-1

 

An aerosol deflection technique based on the single-shot UV-laser-induced fluorescence spectrum from a flowing particle is presented as a possible front-end bio-aerosol/hazardous-aerosol sensor/identifier. Cued by the fluorescence spectra, individual flowing bio-aerosol particles (1-10 um in diameter) have been successfully deflected from a stream of ambient aerosols. The electronics needed to compare the fluorescence spectrum of a particular particle with that of a pre-determined fluorescence spectrum are presented in some detail. The deflected particles, with and without going through a funnel for pulse aerodynamic localization (PAL), were collected onto a substrate for further analyses. To demonstrate how hazardous materials can be deflected, TbCl3·6H2O (a stimulant material for some chemical forms of Uranium Oxide) aerosol particles (2 um in diameter) mixed with Arizona road dust was separated and deflected with our system.

 

Multiple UV Wavelength Excitation and Fluorescence of Bioaerosols

Vasanthi Sivaprakasam, Alan L. Huston, Cathy Scotto, Jay D. Eversole

Optical Sciences Division, Naval Research Laboratory,  Optics Express 4457, Volume 12, Number 19, September 20, 2004

Copyright ©2004 OSA

 

A two-wavelength laser-induced fluorescence technique is described for detecting and classifying biological aerosols. Single aerosols, smaller than 10 m, are interrogated with 266 nm and 355 nm laser pulses separated in time by 400 ns. Fluorescence signals excited by these pulses are detected in three broad spectral bands centered at 350 nm, 450 nm and 550 nm. The results indicate that bacterial spores, vegetative bacterial cells and proteins can be differentiated based on the two wavelength excitation approach. Estimates of the fluorescence cross sections for 16 bioaerosol simulants and interferents are presented.

 

Single-Particle Fluorescence Spectrometer for Ambient Aerosols

Yong-Le Pan, Justin Hartings, Ronald G. Pinnick, Steven C. Hill, Justin Halverson, and Richard K. Chang

Aerosol Science and Technology 37: 627–638, 2003

Copyright ©2003 American Association for Aerosol Research

 

A fluorescence particle spectrometer (FPS) for real-time measurement of the fluorescence spectra of aerosol particles in the size range 1-10 um diameter is reported. The prototype FPS has a sufficiently high sample rate (from 5 to 28 l/min for 3.5 um to 11 um diameter particles) to measure aerosol within buildings at practical rates (from 1 up to 600 particle fluorescence spectra per minute). Previously reported bioaerosol prototype detectors for measurement of single particle spectra were unable to sample the ambient environment; air containing particles had to be forced under pressure into a sample cell. In addition, sample rates were so small (less than 0.01 l/min) as to be impractical for most applications. The present design overcomes these deficiencies by the use of an airtight cell that highly concentrates micrometer-sized particles. A virtual impactor first concentrates aerosol particles, which are then drawn under negative pressure through an aerodynamic focusing nozzle in the inlet of the instrument, through the sample region, providing further concentration. The rate of particle spectra measured by the FPS increases significantly when the particle inlet is within a few meters of some common sources of indoor biological particles, e.g., a person coughing, sneezing, or rubbing his skin, or the presence of a dog. The spectra obtained have a variety of spectral shapes. The FPS may be useful in a variety of areas, e.g., in studying and monitoring airborne particles that cause diseases or allergies.

 

Spectroscopic Sorting of Aerosols by a Compact Sensor Employing UV LEDs

Kristina Davitt, Yoon-Kyu Song, William R. Patterson III, Arto V. Nurmikko, Yong-Le Pan, Richard K. Chang, Jung Han,  Maria Gherasimova, Patrick J. Cobler, Paul D. Butler, Vincent Palermo

Aerosol Science and Technology, 40:1047–1051, 2006

Copyright ©2006 American Association for Aerosol Research

 

A compact sensor for physically sorting bioaerosols based on fluorescence spectra from single particles excited using arrays of ultraviolet light emitting diodes (UV LEDs) is presented. The optical system integrates electronics for real-time processing of spectral data and a miniaturized aerodynamic deflector for particle separation. Fluorescent polystyrene latex spheres are used to demonstrate fluorescence collection on-the-fly, operation of a real-time spectral algorithm, and physical separation of individual particles. This sensor illustrates the utility of recently developed UV LEDs, in conjunction with novel optical design and custom electronics, to shrink the size of aerosol fluorescence detection systems.

 

High-speed, High-sensitivity Aerosol Fluorescence Spectrum Detection Using a 32-anode Photomultiplier Tube Detector

Yong-le Pan, Patrick Cobler, Scott Rhodes, Alexander Potter, Tim Chou, Stephen Holler, Richard K. Chang,  Ronald G. Pinnick, Jean-Pierre Wolf

Review of Scientific Instruments, Volume 72, Number 3, March 2001

Copyright ©2001 American Institute of Physics

 

A 32-anode photomultiplier tube (PMT) is employed in a fluorescence detection system to demonstrate its ability to record broad fluorescence spectra at frame rates in excess of 1400 Hz, which is 56 times faster than the frame rate of an intensified charge coupled device detector. The multi-anode PMT has single-photon detectable sensitivity. A new data acquisition and processing system for the multi-anode PMT, together with the system-controlling software, has been developed. The performance characteristics of the fluorescence detection system, including the data rate capability, dynamic range, signal-to-noise ratio, and crosstalk among the different anodes, are reported. The 32-anode PMT and acquisition system are suitable for a real-time, field-portable, multichannel optical analyzer.