Biophotonics. Fluorescence and replectance in living organisms

Abstract

The light that emerges from a biological entity is relevant from many aspects. In thefirst place, it allows the construction of the organism?s image and consequently itis responsible for visual perception and communication. Secondly, it can becomean important tool in obtaining both physiological and chemical information fromthe observed entity, in a non-destructive way. When an organism is illuminated,the non-absorbed energy emerges as transmitted or reflected light. Additionally,fluorescence, phosphorescence or bioluminescence may be emitted. In ourresearch group, we have studied and modelled the light released as reflectanceand fluorescence for different biological systems like flowers, fruits, plant leaves,canopies, bird?s plumage and amphibians. In this review, we present the advances we have made in this area. They rangefrom the development of theoretical approaches to the implementation of optical methodologies for practical applications.The analysis of light interaction with biological material, which is the domain of biophotonics, has recently acquired greatimportance in view of the increasing use of optical techniques to the study of living tissues. However, the interpretationof the photophysical and spectroscopic properties of these systems is usually complicated by several factors: elevatedchromophore?s concentration, optical inhomogeneity, multi-scattering of photons and presence of multi-layered structuresin most cases. Because of these, the accurate modelling of the interaction with light helps to avoid artifacts and to betterinterpret the processes that take place. Physical models used in the analysis of chlorophyll fluorescence in leaves andcanopies with application in remote sensing, optical methodologies for food control and quantification of fluorescence in vivofor evaluation of its biological relevance are examples of the use of the emission of light and will be presented in this review.