<title>Luminescence lifetime imaging system using imaging fibers to measure the 2D distribution of O2 in biological samples</title>

Abstract

A new sensor head and imaging application with planar oxygen optodes is presented. It combines the versatility of the recently presented modular luminescence lifetime imaging system (MOLLI) and the oxygen measuring features of planar optodes to investigate the 2D-distribution of oxygen with a high spatial resolution. The marine sediments are settled by micro-organisms. They are characterized by steep gradients of solutes perpendicular to the interface. Oxygen as the most favorable electron acceptor plays an important role in these communities and exhibits steep gradients within distances of 100 micrometer to a couple of millimeters. Traditionally these gradients are commonly accessed by either oxygen microelectrodes or oxygen micro-optodes, that measure single oxygen depth profiles at spatial resolutions in the range of 50 - 5 micrometer. As the influences on the metabolism of these organisms are complex, profiles that are measured at one location exhibit a natural heterogeneity. To address this problem by using the potential of planar oxygen optodes first measurements with optodes fixed to an aquarium wall (Glud et al. 1996) based on luminescence intensity measurements have been published. They showed the large amount of information that can be gathered by this method. We further developed this approach by combining the planar optode with the capabilities of imaging fibers that form an endoscope. We developed a periscope type sensor head that can be independently applied in biological samples. It has an overall diameter of 2.5 mm and a calculated pixel resolution of 12 micrometer. The according measuring system compared to the published system has a different excitation light setup and corresponding endoscope optics to measure the lifetime based images. We present the adapted system, sensor head and the first results of an application.