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Here, we present an overview of the research activities of division Biophotonics concerning the design and (bio)analytical application of molecular and nanoscale functional chromophores for e.g., biomarker analysis including methods for the reliable determination of their application relevant properties. This includes the absolute determination of their brightness and photoluminescemce quantum yield, determining the signal size from the material side, as well as the development of fluorescence standards for such measurements and instrument calibration strategies, thereby providing important prerequisites for the comparison of material performance, the mechanistic understanding of nonradiative decay channels, and the rational design of new optical reporters. Moreover, for particle-based systems, ranging from nm-sized semiconductor quantum dots to m-sized polymeric and silica beads, simple optical methods and assays for the assessment of their surface chemistry are presented, which enable the quantification of the number of total and derivatizable surface functionalities, ligands per particle and particle-bound biomolecules. In addition, validation concepts for such methods are introduced utilizing method comparisons, multimodal and cleavable probes.
Elemental imaging of biological samples using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) provides spatially resolved information on element distribution in thin sections. By rastering with a laser across the sample, a two-dimensional image of the elemental distribution can be reconstructed that shows the intensities of the respective elements. Using overlapping laser shots the area ablated from single cells or thin sections (thickness 5 to 10 µm) can be reduced significantly so that the pixel size of the intensity measurement is significantly reduced. Having in mind that a laser shot ablates thin biological samples completely, we can make use of a new concept for calibration in the laser ablation method: the concept of total consumption. This calibration strategy allows production of simple matrix matched standards and provides an internal standardisation by ink jet technology, where a metal containing inks is printed on as thin layer on top of a biological sample.
Different applications will be presented where our concepts have been applied. In the first example we used nanoparticle suspension of given particle numbers to quantify the uptake of metallic nanoparticles by biological cells. In the second example antibodies have been tagged by metals to measure protein expression in prostata cancer. In this approach application of house keeping proteins are investigated additionally to compensate variations in thickness and density of the biopsy samples. In the third application different nephrotoxic behaviour of Pt containing drugs have been investigated to study the local enrichement in kidney samples of mice treated with these three different compounds. Here the internal standard is required to allow intercomparisons between different individual mouse tissues.
At the end of the lecture future trends will be discussed for elemental microscopy.