Multispectral analysis of biological agents to implement a quick tool for stand-off biological detection

With the aim of identifying an approach to exploit the differences in the fluorescence signatures of biological agents BAs, we have investigated the response of some BAs simulants to a set of different excitation wavelengths in the UV spectral range (i.e. 266, 273, 280, 300, 340, 355 nm). Our preliminary results on bacterial spores and vegetative forms, dispersed in water, showed that the differences in the fluorescence spectra can be enhanced, and more easily revealed, by using different excitation wavelengths. Specifically, the photo luminescence (PL) spectra coming from different species of Bacillus, in the form of spores (used as simulants of Bacillus anthracis), show significant differences under excitation at all the wavelengths, with slightly larger differences at 300, 340, 355 nm. On the other hand, the vegetative forms of two Bacillus species, did not show any appreciable difference, i.e. the PL spectra are virtually identical, for the excitation wavelengths of 266, 273, 280 nm. Conversely, small yet appreciable difference appear at 300, 340, 355 nm. Finally, large difference appear between the spore and the vegetative form of each species at all the wavelengths, with slightly larger variations at 300, 340, 355 nm. Together, these preliminary results support the hypothesis that a multi-wavelength approach could be used to improve the sensitivity and specificity of UV-LIF based BAs detection systems. The second step of this work concerns the application of a Support Vector Regression (SVR) method, as evaluated in our previous work to define a methodology for the setup of a multispectral database for the stand-off detection of BAs