Standoff detection and classification of bacteria by multispectral laser-induced fluorescence

Abstract

Abstract:Biological hazardous substances such as certain fungi and bacteria represent a high risk for the broad public if fallen into wrong hands. Incidents based on bio-agents are commonly considered to have unpredictable and complex consequences for first responders and people. The impact of such an event can be minimized by an early and fast detection of hazards. The presented approach is based on optical standoff detection applying laser-induced fluorescence (LIF) on bacteria. The LIF bio-detector has been designed for outdoor operation at standoff distances from 20 m up to more than 100 m. The detector acquires LIF spectral data for two different excitation wavelengths (280 and 355 nm) which can be used to classify suspicious samples. A correlation analysis and spectral classification by a decision tree is used to discriminate between the measured samples. In order to demonstrate the capabilities of the system, suspensions of the low-risk and non-pathogenic bacteria Bacillus thuringiensis, Bacillus atrophaeus, Bacillus subtilis, Brevibacillus brevis, Micrococcus luteus, Oligella urethralis, Paenibacillus polymyxa and Escherichia coli (K12) have been investigated with the system, resulting in a discrimination accuracy of about 90%.

Optical Characteristics of Micro‐sized Biological Aerosol Particles

“…Moreover, fine particles can help transport a significant number of biological particles, pollens, and microorganisms like fungi and bacteria. 9,10 The quantum efficiency (QE) of fluorescence varies depending on the excitation light source. [1][2][3] Many countries are developing sensor systems that can be used for real-time detection of hazardous airborne particles, including biological particles.…”

Novel standoff detection system for the classification of chemical and biological hazardous substances combining temporal and spectral laser-induced fluorescence techniques⋆

“…One of the most widely used techniques for standoff detection of biological and chemical samples is laser-induced fluorescence (LIF) spectroscopy, since it provides high signal strength and thereby fast detection times on the order of seconds to minutes and long detection ranges up to a kilometer [5][6][7][8][9]. For aerosol samples, LIF spectroscopy is often combined with light detection and ranging (LIDAR) by making use of photon arrival time measurements [3,7,9].…”

“…For spectrally resolved LIF the rather broad spectral features of the specimens of interest allow for a downscaling of the spectroscopic resolution from 1024 spectral channels in ref. [5] to 32 spectral channels with no reduction of the classification performance as presented in ref. [11].…”

“…But, in comparison to other techniques the rather low information content provides limited identification prospects. Laser pulses with different central wavelengths can be used to excite different fluorophores [5,12], e.g. the amino acids tryptophan and tyrosine, using a laser wavelength of i.a.…”

“…The diverse spectral shapes of the fluorescence signals after excitation with these different laser pulses provide distinct information for the subsequent classification procedure. By combining the datasets of both excitation processes the classification performance can be improved significantly [5,11,13]. To further enhance the specificity in the presented setup we simultaneously acquire temporally resolved LIF signals for each excitation pulse using fast electronics.…”