Development of a fluorescence-based point detector for biological sensing

Abstract

This paper presents the status of an ongoing development of a point detector for biological warfare agent sensing based on ultraviolet laser-induced fluorescence from single particles in air. The detector will measure the fluorescence spectra of single particles in a sheath flow air beam. The spectral detection part of the system consists of a grating and a photomultiplier tube array with 32 channels, which measure fluorescence spectra in the wavelength band from 300 nm to 650 nm. The detector is designed to measure laser induced fluorescence from single laser pulses and has been tested by measuring fluorescence from simulants of biological warfare agents in aqueous solution. The solutions were excited with laser pulses at the wavelengths of 293 nm and 337 nm. The paper also presents preliminary results on the sheath flow particle injector and time-resolved measurements of fluorescence from biological warfare agent simulants in solution.

Development of Fluorescence-based LIDAR Technology for Biological Sensing

“…In water solution OA gives a relatively narrow fluorescence ranging from 300 to 425 nm with a peak at 345 nm and the dominating emission decay constant being 6.7 ns [6]. A representative series of spectra of the OA aerosol is displayed in Fig.…”

“…However, the 1 µs long integration of PMT array signal started slightly before the UV laser pulse, in order to comprise the whole fluorescence signal which occurs in the ns range, partially within the excitation pulse. It is known that for similar species in solution the decay time of the fluorescence is typically in the order of 3 -10 ns [6]. A schematic of the trigger PMT signal during a data acquisition cycle and the sequential triggering events is shown in Fig.…”

“…This method can provide a close to real-time warning and improve the classification of the particles, resulting in a lower degree of false positive alarms. We have previously demonstrated the successful use of a UV laser at different wavelengths to excite molecular aggregates such as proteins and bacteria in solutions [4][5][6]. Moreover, multivariate data analysis (principal component analysis (PCA)) of spectral fluorescence data has been used to classify different BWA simulants and distinguish them from background compounds in field trials [7].…”

“…Biogenic chemicals associated with cell metabolism, such as reduced nicotinamide adenine dinucleotide (NADH) and riboflavin have their maximum absorption cross-section at around 340 nm and the resulting fluorescence peaks between 450 nm and 560 nm [2]. The route we are pursuing is based on LIF at several excitation wavelengths with spectrally resolved detection [3][4][5][6][7]. This method can provide a close to real-time warning and improve the classification of the particles, resulting in a lower degree of false positive alarms.…”

Tailored UV-laser source for fluorescence spectroscopy of biomolecules

“…The PMT-array from Hamamatsu (model H7260-4) has 32 channels linearly spaced, and it was connected to a spectrograph from Oriel (model 77442), with a fiber connection [19]. The UV light from the laser was coupled into a 10 m long quartz fiber, with a diameter of 1 mm and an NA of 0.39, seen in Fig.…”