Analysis of luminescence in turbid biological media

Background: Quantitative luminescent analysis is widely used in biology, laboratory diagnostics and clinical medicine to study objects at various levels. However, the existing simplified algorithms for calculation of the luminophore concentration in diluted linear solutions cannot be applied to the turbid media with strong light scattering, which include the majority of living biological tissues. Today, the development of luminescence analysis in medicine goes towards the creation of non-destructive and non-invasive methods of in vivo monitoring. Therefore, the urgent question is about a formulation of the research purpose and the development of algorithms to compute the luminophore concentration based on the luminescence spectra recorded in the turbid media. Objective: To formulate and justify the tasks of elaboration of the algorithms to compute the luminophore concentration based on the luminescence spectra recorded under conditions of the optically turbid media. Materials and methods: We looked upon the physico-mathematical simulation of the process of formation of the induced fluorescence emission in the light-scattering medium based on the modified 2-flux Kubelka-Munch model. We conducted a series of laboratory experiments with macro-homogenous light-scattering model media to determine characteristics of the dependence of the fluorescence intensity detected from the surface of an optically turbid biological medium upon the factor of light scattering and the concentration of the fluorophore in the medium. Results: Both theoretical and experimental results demonstrate complex nonlinear dependence of the fluorescence intensity detected upon the optical properties and a  concentration of a  fluorophore in the turbid media. This dependence is very different from the known linear  C.  Parker's solution for transparent media, which makes it impossible to use it in the optically turbid media. Conclusion: Further studies searching a  closed-form analytical solution of the inverse optical problem for light-scattering and fluorescent media are necessary to calculate the luminophore concentration in a light-scattering media based on the recorded luminescence spectra.