After Biophotonics '09
6-13 June 2009, Ven, Sweden
About the best poster awards 2009
During the school, the students presented their projects and/or results at two poster sessions. The level of these two session was at an outstanding high level both in terms of the scientific content and the presentations themselves.
The poster presentations were evaluated by:
- Professor Kishan Dholakia
- Professor Steven L. Jacques
- Professor Eva Sevick-Muraca
- Professor, MD Katarina Svanberg
- Professor Roy Taylor
- Professor Hubert van den Bergh
- Professor Stefan Andersson-Engels
- Professor Peter E. Andersen
The following main criteria were applied:
- The visual appearance of poster
- The oral presentation accompanying the presentation
- The current and/or future scientific impact of the content within the field of biophotonics
Because of the outstanding level of the presentation, the evaluation committee decided to name one winner and in addition five honorable mentioning's for outstanding presentations.
The Best Poster Award 2009 consists of a diploma and a cash prize (400 Euro) sponsored by Thorlabs Sweden AB.
The Honorable Mentioning 2009 Award consists of a diploma. Five prizes were awarded, see below.
Sebastian Berning received the Best Poster Award 2009
(Profs. Stefan Andersson-Engels (left)) sponsored by
Thorlabs Sweden AB.
Best Poster Presentation Award 2009
Sebastian Berning
Max Planck Institute for Biophysical Chemistry
NanoBiophotonics
Göttingen 37077, Germany
sbernin@gwdg.de
Poster title: Developing STED microscopy for deep imaging
Abstract: In the last decade, a number of techniques have been developed in order to overcome the fundamental resolution limit in far-field microscopy imposed by diffraction. All of these techniques rely on non-linear photophysical properties in fluorescence microscopy to make sure that only a small, strongly localized fraction of the flurophores within a diffraction-limited excitation volume is able to contribute to the fluorescence signal at a time, for instance by switching the fluorescence of the surrounding fluorophores reversibly off. In Stimulated Emission Depletion (STED) microscopy, this kind of switching is achieved with a second laser beam enclosing the focal excitation spot with a doughnut-shaped illumination pattern exhibiting a point of zero intensity at its centre. The wavelength of this STED-beam is chosen such as that it will suppress the fluorescence anywhere within the excitation area but at this point of zero-intensity through the mechanism of stimulated emission. In this way, impressive resolutions in the range of a few tens of nm have been routinely demonstrated in a multitude of biological samples. What remains challenging is the imaging of deeper layers of samples with a low refractive index close to that of water, as commonly found in in-vivo experiments. In this case, using a high-NA oil-immersion microscope objective will introduce spherical aberrations causing the resolution advantage of STED over confocal microscopy to significantly decrease with increasing depth. As a first step in the development of a new STED microscope specially designed for deep imaging applications, different objectives were therefore systematically screened for their ability to maintain good imaging properties over a large depth range in aqueous mounting media. The results are very promising, as it could be shown that STED microscopy is applicable for these samples even at depths exceeding 100 microns if certain precautions are taken. The overall complexity of the optical setup could at the same time be kept on a well-manageable level.
Honorable Mentioning
Torsten Frosch
University Jena
Physical Chemistry
Jena 07743, Germany
torsten.frosch@uni-jena.de
Poster title: Raman spectroscopic investigation of drug-target-interactions
Abstract: Malaria is one of the most devastating infectious diseases on earth and resistances against key drugs like chloroquine arise on a global scale. However, the molecular mode of action of those drugs is not well understood. It is believed that the quinoline class of antimalarials acts by interfering with the detoxification process of the hemoglobin digestion by-products in the red blood cell state of the plasmodium’s asexual life cycle. In this contribution - the high sensitivity and selectivity of UV resonance Raman microscopy is demonstrated by a structural investigation of different drugs under physiological conditions. The protonation of the weak base chloroquine is crucial for the efficiency of the drug and has been modelled by means of DFT calculations. Also the new, promising active agent dioncophylline A was localized in situ in very low concentrations in the tropical liana Triphyophyllum peltatum. This was possible by exploiting the advantages of UV resonance Raman spectroscopy, namely: 1) the spectral separation of the Raman spectra from overlapping fluorescence signals, 2) the resonance enhancement and 3) the intrinsic enhancement of the scattering by using UV wavelengths. A convincing mode assignment of the resonance Raman spectra of the drugs was possible by means of a combination of NIR Raman spectra and DFT calculations. Also the biological target - the Malaria pigment hemozoin - was structurally investigated. Hemozoin was localized in Plasmodium falciparum infected red blood cells by means of Raman microscopy in the visible range, in resonance with the iron porphyrin. These in situ results were compared with spectra of extracted hemozoin as well as with synthesized ß-hematin. Importantly it was proofed that ß-hematin is the synthetic analogue of the malaria pigment and even more it was possible to distinguish between different morphologies of this structure. Also the dimeric unit cell of the malaria pigment was calculated for the first time. Those DFT calculations of the Raman spectra and the atomic displacements assisted much in the assignments and the understanding of the experimental results. The interactions of the drugs and hematin were studied. A dramatic change of the depolarization ratio of the v19-mode appeared in the polarization resolved Raman spectra. Those inverse polarized mode of hematin is very sensitive for symmetry lowering – in our case the docking of the chloroquine drug. To be able to detect the very small wavenumber shifts which occur due to the weak interactions, a novel device for Raman differences spectroscopy (RDS) was designed, that allows for detection of wavenumber shifts down to 1/100 of the linewidth. With help of this new RDS device we were able to monitor weak interactions of chloroquine and hematin for the first time. Once more the DFT calculations of the normal modes turned out to be very helpful for an interpretation of the experimental findings.
Honorable Mentioning
Anita Gollmer
University of Aarhus
Department of Chemistry
Aarhus 8000 C, Denmark
gollmer@chem.au.dk
Poster title: Detection of singlet oxygen using fluorescent chemical traps in sub-cellular domains of a single cell
Abstract: Singlet oxygen (1O2), the lowest excited electronic state of molecular oxygen, plays a major role in many chemical and biological processes, e.g. in photodynamic therapy. Several methods have been established to detect 1O2. Due to the experimental detection limits of these existing methods, we would like to introduce fluorescence probes which are chemical traps to detect 1O2 in single cells. Fluorescence probes are known to be excellent sensors for biomolecules, being sensitive, fast-responding and capable of affording high spatial resolution via microscope imaging. Chemical traps which are normally almost non fluorescent, can react with 1O2 forming a fluorescent endoperoxide. Measuring its fluorescence or monitoring the decrease in the amount of the trap provides a powerful tool to detect 1O2 with a higher sensitivity. Another promising advantage is that lower amounts of 1O2 are required to detect a signal. The fluorescence quantum yield of the endoperoxides are much higher than the phosphorescence quantum yield of 1O2. Therefore, the cells are less in risk of being damaged under unnecessarily harsh experimental conditions. The next step will be to specifically localize a photosensitizer and a trap into different parts of a single cell using, for example, protein labeling techniques. With this method we want to achieve a greater control of the generation and decay of 1O2 inside a cell.
Honorable Mentioning
Pier-Anne Lachance
University of Texas Health Science Center
Institute of Molecular Medicine Center for Molecular Imaging
Houston 77030 TX, United States
Pier-Anne.Lachance@uth.tmc.edu
Poster title: Validation of IRDye800 conjugated peptides imaging agent targeted to integrin α9 for optical imaging of lymphangiogenesis
Abstract: The lymphatic system is a major component of the circulatory system which functions are fluid balance, lipid absorption, and a site for immune surveillance. Due to the importance of the lymphatic’s functions for tissue homeostasis, pathologies which involve lymphatic dysfunctions are diverse and include lymphedema, inflammation, obesity, and cancer. The process of forming new lymphatic vessels is called lymphangiogenesis. There is a need to understand the mechanism and the role of lymphangiogenesis in diseases. Herein, there is a need for developing a molecular imaging agent which could image the process in vivo. The α9 integrin subunit has been linked to lymphangiogenesis through its direct interaction with the vascular endothelial growth factor family and the hepatocyte growth factor. In addition, α9 integrin is a critical in lymphatic vessel development, suggested by the lethality of α9 knockout mice. We believe that expression and affinity of α9 integrin are change during lymphangiogenesis to promote lymphatic cells proliferation and migration. Therefore, α9 integrin is a potential molecular target for imaging of lymphatic remodeling. In this study, we first would like to determine if integrin α9 is a marker for lymphangiogenesis. To answer this question, we are using in vivo and in vitro assay to determine the role and level of expression of integrin α9. We are in the process of developing an integrin α9 inducible tissue specific knockout mouse to assess the role and mechanism of integrin α9 in lymphangiogenesis. We have synthesized and labeled two peptides containing the MLDG motif and three peptides with the EIDGIEL motif, which are known to bind to the integrins α9. The peptides were conjugated to IRDye800 for near-infrared optical imaging. We have performed fluorescent microscopy studies validating binding of the conjugated peptides to integrin α9 using Caco-2 cells, and CHO-K1 cells overexpressing α9 subunit. Further characterization of the peptides specificity, affinity, and stability in vitro shows that these peptides are candidates for imaging of α9 integrin. This is the first step in developing and validating a new peptide agent for in vivo lymphangiogenesis imaging.
Honorable Mentioning
William Lo
University of Toronto
Department of Medical Biophysics
Toronto M5G 2M9, Canada
wlo@uhnres.utoronto.ca
Poster title: Hardware-accelerated MC Simulation for PDT Treatment Planning using FPGAs and GPUs
Abstract: Monte Carlo (MC) simulations are being used extensively in the field of medical biophysics, particularly for modeling light propagation in tissues. The high computation time for MC limits its use to solving only the forward solutions for a given source geometry, emission profile, and optical interaction coefficients of the tissue. However, applications such as photodynamic therapy treatment planning or image reconstruction in diffuse optical tomography require solving the inverse problem given a desired dose distribution or absorber distribution, respectively. A faster means for performing MC simulations would enable the use of MC-based models for accomplishing such tasks. To explore this possibility, a digital hardware design of an MC simulation based on the Monte Carlo for Multi-Layered media (MCML) software was implemented on multiple field-programmable gate arrays (FPGAs). The hardware performed the MC simulation approximately 80 times faster on a development platform called the TM-4 with four Stratix I FPGA chips (20x per chip) compared to MCML executed on a 3-GHz Intel Xeon processor based on Pentium 4 technology. By migrating to the modern DE3 board, a 42-fold speedup was achieved with one Stratix III device. For comparison, MCML was also implemented on a multi-GPU system with 2 NVIDIA GTX280 graphics cards comprising 480 cores. This approach led to a 113x speedup (56.5x per device) compared to the same Intel processor. However, compared to a 3-GHz Intel Xeon 5160 processor with better CPU architecture, the performance gap was narrowed by 1.5 times. Both the FPGA-accelerated and GPU-accelerated MCML implementations were validated with a skin model and the isofluence lines generated closely matched those produced by MCML in software. The development process will also be discussed to highlight the key differences between FPGA-based custom hardware design and GPU-based CUDA programming for high performance computing.
Honorable Mentioning
Tilman Schmoll
Medical University Vienna
Center of Biomedical Engineering and Physics
Vienna 1090, Austria
tilman.schmoll@meduniwien.ac.at
Poster title: In-vivo Assessment of Photoreceptor Response with Functional Optical Coherence Microscopy
Abstract: Probing the retina with flicker light of defined frequencies allowed to offset the detection for intrinsic signals from proband motion artifacts as well as blood flow. In addition the fast imaging sequence capability of FDOCT is promising for the assessment of fast physiologic changes within retinal structures. For the present study two measurement protocols are evaluated: first, taking fast tomogram series across a flickered region, and then constructing via frequency analysis and bandpass filtering a functional OCT tomogram similar to fMRI. The second protocol consists of a fast local A-scan series at 17kHz rate with 1Hz flicker. “Light-on” time is 250ms. “Lights off” time is 750ms. 500ms before “light-on” is used for calculating the baseline. Finally the average over 5 cycles is taken. A clear negative response is found at the outer photoreceptor segment for both “light-on” and “light-off” edge. The response appears to be stronger for the “light off” edge. The shape of the responses is analysed and might eventually be used in linear regression models to enhance the sensitivity of our fOCT approach.
