Biophotonics

Available fluorescence techniques (enlarged picture)

The Division Biophotonics focuses on the design, characterisation and application of functional chromophore systems, the design and validation of innovative spectroscopic methods for these applications as well as the design and fabrication of certified standards and calibration tools and validation strategies for various fluorescence techniques.

The functional chromophore systems under study comprise organic and inorganic fluorophores, nanocrystalline materials (e.g. quantum dots), particle-based systems, probes and labels for surface functionalities, and dye-biomolecule conjugates (e.g. optical probes for molecular imaging). The corresponding research activities comprehend the systematic spectroscopic characterisation of these materials as well as investigations dedicated to the application of these systems including multiplexing and signal enhancement strategies. Another key aspect presents the development of methods for the measurement of absolute fluorescence quantum yields and the characterisation of the optical properties of scattering and fluorescent systems like suspensions of nm- to µm-sized particles.

The central research area “standardisation of fluorescence measurements” includes the design, validation, and certification of format-adaptable fluorescence standards for different fluorometric quantities (e.g. relative and absolute fluorescence quantum yield, fluorescence lifetime) and fluorescence techniques (e.g. standards for the spectral responsivity, day-to-day performance, and fluorescence quantum yield) as well as the validation of suitable fluorescence methods and protocols. In the focus of these research activities are e.g. classical fluorescence spectroscopy, methods for the characterisation of scattering and luminescent systems (e.g. integrating sphere setups) as well as methods for the readout of fluorescence assays (e.g. fluorescence microscopy and microarray technology).

Within these key activities, we perform traceable temperature and polarisation-dependent absorption and fluorescence measurements (steady state; time-resolved: ps to ms time domain) and fluorescence microscopic investigations (spectrally resolved confocal laser scanning microscopy (CLSM)) with liquid and solid, transparent and scattering samples in the ultraviolet (UV), visible (VIS) and near-infrared (NIR) spectral region (250 nm to 1700 nm).

The international comparability of the measurement capabilities of the research group has been demonstrated and assured in an interlaboratory comparison with the National Institute of Standards and Technology (NIST, USA), the National Research Council (NRC, Canada), and the Physikalisch-Technische Bundesanstalt (PTB). The spectroscopic methods used are covered by the accreditation (DAkkS) of Department 1.

These efforts also led to application-oriented research activities such as the optimisation of labeling densities of dye-biomolecule conjugates and dye staining of particles as well as the quantification of surface functional groups on scattering nano- and microparticles and on 2D-substrates.

Key activities

Functional chromophore systems (enlarged picture)

• Spectroscopic characterisation of chromophore systems in different matrices and on surfaces
• Methods for the optimisation of fluorescence signals including signal enhancement strategies (Rolling Circle Amplification (RCA); FRET)
• Multiplexing strategies (spectral; lifetime)
• Design and characterisation of functional dye-biomolecule conjugates
• Design and characterisation of luminescent nano- and microparticles
• Investigation of the interactions of chromophore systems and nanoparticles with biological systems (e.g. proteins, cells)
• Standardisation of fluorescence measurements: Design, development, validation, and fabrication of format-adaptable fluorescence standards for intensity, spectral, and temporal quantities
• Methods for the determination of relative and absolute fluorescence quantum yields of liquid and solid, transparent and scattering systems in the UV/VIS/NIR spectral region
• Methods for the determination of the optical properties (absorption, scattering, reflectance) of liquid and solid scattering systems like particle suspensions
• Methods for the quantification and characterisation of functional groups on particle surfaces and 2D-substrates

Cooperations

Formate-adatable fluorescence standards (enlarged picture)

• J. Kneipp (BAM Division 1.0 and Institut für Chemie, Humboldt-Universität zu Berlin) and H.-J. Kunte (BAM Division 4.1): Interaction of nano particles with biological systems
• I. Hilger (Universitätsklinikum Jena), F. Alves (MPI Experimental Medicine Goettingen), F. Kiessling (RWTH, Aachen), and K. Licha (Mivenion GmbH): Highly fluorescent dye-biomolecule conjugates for in vivo near-infrared fluorescence imaging
• A. Eychmüller (Universität Dresden), H. Weller (Universität Hamburg) and T. Nann (University of South Australia): Nanocrystalline labels and probes for (bio)analytical applications

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