Maria Mosshammer: Novel Optical Sensing Approaches in Environmental and Biomedical Science Date: 29-01-2019    Supervisor: Michael Kühl

The focus of this thesis was the development, optimization, and application of optical, chemical sensor systems for different analytes. A general introduction to optical chemical sensors is given, different measuring geometries are introduced such as fiber optic sensors, planar optodes and optical sensor particles. Optical sensor particles are described in greater detail in the included review paper on aquatic applications of optical micro- and nanoparticle sensors.

Different read-out options for optical sensor systems are described as well, including a method paper, comparing two area scan cameras for luminescence lifetime imaging based on i) time-domain and ii) frequency domain measurements. Ratiometric luminescence intensity imaging and laser-ablation ICP-MS as well as a multi-analyte system are described in the appendix in two publications. These papers have their origin in my Master’s thesis, which is why they are attached only in the appendix. This encompasses a planar optode for simultaneous imaging of pH and dissolved O₂, as well as the irreversible chemical imaging technique diffusive gradient in thin film (DGTs). They are included for additional information on optical sensor systems.

In addition to reversible sensor systems irreversible probes are introduced. The analyte, H₂O₂, a reactive oxygen species (ROS), is of high importance in biomedicine as well as biology. To this date ROS have mainly been determined via irreversible probes, due to a lack of suitable sensor systems for quantitative analysis. Different irreversible sensor methods are introduced in the form of a review paper, where state of the art measurement techniques for H₂O₂ are described and compared to each other. One promising H₂O₂ sensing approach (based on a flow injection system) was chosen and modified to enable in-situ measurements of dynamic H₂O₂ concentration changes in liquid as well as semi-solid media. The novel measuring system, consisting of analyte acquisition via microdialysis probes and detection via flow injection analysis, is introduced in a paper. Later improvements to this method are summarized in a non-peer reviewed conference proceeding paper.

Unpublished results from measurements on oral neutrophils are summarized as well, to highlight the applicability of the system in biomedical applications. Other (unsuccessfully) investigated H₂O₂ sensor systems are summarized in a short chapter.