Microwavephysics and Atmospheric Physics
Biomedizinische Photonik
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Ultrafast Science and Technology
Last update: 13.09.2017
HS 2015: Seminare über Biomedizinische Photonik
Wednesday 10-12
Vorträge, die innerhalb der nächsten Tage stattfinden, sind speziell markiert.
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Mittwoch, 16.09.2015

The delivery of molecules into corneal grafts by nanoparticles activated by femtosecond laser

Zeit: 10:15 Uhr
Hörsaal: A97
 
Dr. Clotilde Jumelle
Biology Imaging Engineering for Corneal Graft Laboratory, Saint-Etienne University, France

Corneal endothelial cells (CEC) are essential for corneal transparency. However, on humans, they are unable of proliferation, making corneal endothelial monolayer particularly vulnerable. The gene and drug delivery represents a promising solution to maintain CEC viability. Unfortunately, the major difficulty of this technique is the transport across the cell membrane, normally impermeable to high-size molecules. Several techniques of molecules delivery have already been tested on corneal tissue but none of them gives results sufficiently convincing to be used in clinical applications. Our goal was to adapt and develop a new technique of intracellular molecules delivery, based on cell perforation via photoacoustic effect induced by the activation of carbon nanoparticles by femtosecond laser, on in vitro and ex vivo models of corneal endothelium.

 
Mittwoch, 23.09.2015

Optimization of Gold Nanorods for Photoacoustic Applications: Size, Coating and Cellular Uptake

Zeit: 10:15 Uhr
Hörsaal: A97
 
Dr. Lucia Cavigli
Institute of Applied Physics, National Research Council of Italy, Firenze, Italy

The high absorbance of gold nanorods in the near-infrared region combined with the inertness of gold make these particles excellent candidates to improve the contrast in photoacoustic imaging and as phototransducers for the selective photothermolysis of cancer. However, gold nanorods still suffer from limitations. Their cylindrical profile is unstable against overheating and tends to revert into more spherical shapes without optical absorbance in the near infrared window. Within the nanosecond duration regime of principal interest for photoacoustic applications, this transformation begins at optical fluences that fall well below the maximum permissible exposure and restricts the use of gold nanorods. Here, I introduce our method to analyse the damage thresholds of gold nanorods. This quantitative approach enables a systematic optimization of relevant parameters. The influence of gold nanorods size has been investigated and has been observed that smaller particles exhibit higher damage thresholds, which correlates with their larger specific surface area and faster thermalization with their environment. Another option to improve the stability of gold nanorods is the design of functional coatings, which may serve both as an effective mold against their reshaping and as a solution to reduce their interfacial thermal resistance. Another critical issue before the application of gold nanorods is their efficient delivery to tumors. To date, one of the most common approaches to deliver GNRs into tumors is their direct injection into the bloodstream. However, this pathway remains problematic, because most of the particles are captured by the immune system and their optical behavior undergoes modifications in the body. One alternative may be the use of cellular vehicles that exploit the tropism of tumor-associated macrophages. These cells exhibit an inborn capacity to migrate to a tumor and may be harvested from a patient, loaded with gold nanorods and used as Trojan horses for their delivery. Here, I introduce multiple approaches to provide gold nanorods with biocompatibility and cationic profiles, in order to promote their efficient internalization into macrophages. The mechanism of cellular uptake involves endocytotic pathways, which drives the flocculation of gold nanorods within tight intracellular vesicles. The effect of these conditions on the damage thresholds of the particles has been investigated.

 
Mittwoch, 07.10.2015

Determining the optical properties of tissues: Set-up and optimisation of extinction and double integrating sphere measurements (Bachelor Thesis)

Zeit: 10:15 Uhr
Hörsaal: A97
 
Patrick Stähli
Institute of Applied Physics
University of Bern

 
Mittwoch, 14.10.2015

Improving Optoacoustic Microscope Performance using Nanoparticles as Contrast Agents

Zeit: 10:15 Uhr
Hörsaal: A97
 
Florentin Spadin
Institute of Applied Physics
University of Bern

 
Mittwoch, 21.10.2015

Microthermometric data of stretched and super-cooled liquid water obtained from high-density sythetic fluid inclusions

Zeit: 10:15 Uhr
Hörsaal: A97
 
Chen Qiu
Institute of Applied Physics
University of Bern

 
Mittwoch, 28.10.2015

Engineering of Absorbable Fiber Reinforced Bone Substitute Materials

Zeit: 10:15 Uhr
Hörsaal: A97
 
Elias Mulky
Institute of Applied Physics
University of Bern
and RMS Foundation, Bettlach

Self-setting calcium phosphate based scaffolds are used as bone fillers when excellent biocompatibility is required. Their disadvantages lie in their poor mechanical properties. Reinforcement with polymer fibers has produced mixed results in the past. We demonstrate a method to consistently improve the mechanical properties of scaffolds by improving the fiber dispersion within. The method is then applied to engineer a series of scaffolds with different fiber sizes and contents. Electrospun PLLA fibers with mean diameters of 244 ± 78 nm, and 1.0 ± 0.3 µm were dispersed in Brushite based composited at ratios of 5% and 30% v/v. The mechanical and structural properties of the reinforced cements are examined and compared with composites containing undispersed fibers. Finally we examine methods to further improve the mechanical strength by modifying the fiber-scaffold interfacial adhesion strength.

 
Mittwoch, 04.11.2015

Improving the surgical procedure of cochlear implant using laser radiation (Master's thesis presentation)

Zeit: 10:15 Uhr
Hörsaal: A97
 
Arushi Jain
Institute of Applied Physics
University of Bern

Cochlea implantation is a surgical procedure performed on patients suffering from sensorineural hearing loss. The implantation requires the surgeon to perform mastoidectomy, which is an invasive procedure. This surgical procedure comprises the risk of damaging the facial nerve during the surgery, which can cause facial paralysis. Our research is aimed at making the implantation less invasive and safer. On the one hand, we want to replace the mechanical drilling with laser-drilling in order to drill a hole, whose width matches the diameter of the implantation-electrode's (roughly 1.5mm) and whose depth is approximately 20mm. On the other hand, we wish to stimulate the facial nerve and to gain a simultaneous feedback during the drilling process. The drilling was achieved with a high power diode-pumped Er:YAG laser (2.9µm wavelength), which was provided to us by Pantec Engineering, Lichtenstein. We were able to drill holes in the bovine cortical bones: holes with a width of 1.5mm and a depth of >10mm were formed. For nerve stimulation, the nerve cord of an anesthetized and dissected earthworm was used as a model. For the optical stimulation we used a flash lamp pumped Ho:YAG laser (2.1µm wavelength). The optically induced action potentials were recorded by placing electrodes close to the nerve. A dependence of the amplitude of action potential was observed as a function of radiant exposure. The obtained results are very promising and pave the way for future in-vivo applications.

 
Mittwoch, 11.11.2015

Electrospun patch for laser tissue soldering: investigations of the chromophore concentration, extinction coefficient and leakage

Zeit: 10:15 Uhr
Hörsaal: A97
 
Annemarie Schönfeld
Institute of Applied Physics
University of Bern

 
Mittwoch, 18.11.2015

Quantitative Speed of Sound imaging

Zeit: 10:15 Uhr
Hörsaal: A97
 
Dr. Michael Jaeger
Institute of Applied Physics
University of Bern

 
Mittwoch, 25.11.2015

Fluence-based dosimetry for radiotherapy with carbon ions

Zeit: 10:15 Uhr
Hörsaal: A97
 
Leonie Ulrich
Universität Heidelberg
Deutsches Krebsforschungszentrum (DKFZ)
Abteilung Medizinische Physik in der Strahlentherapie
Heidelberg, Germany

Radiotherapy with carbon ions allows for a high dose conformation which is essential for the irradiation of tumors close to critical organs. The interaction mechanisms of carbon ions in tissue make them biologically very effective and favorable also for radioresistant tumors. However, the enhanced biological effectiveness poses a challenge to dosimetry aiming to predict the therapeutic effect of the radiation. Track-by-track dosimetry using fluorescent solid state detectors offers a possibility to examine the particle spectrum present in a clinical beam and allows for the assessment of physical quantities that determine the tissue response.

 
Mittwoch, 02.12.2015

Quantitative Photoacoustic Imaging: Towards the quantitative assessment of chromophore concentrations

Zeit: 10:15 Uhr
Hörsaal: A97
 
Gerrit Held
Institute of Applied Physics
University of Bern

 
Mittwoch, 09.12.2015

Physical objects and boundaries: geometric considerations in light propagation problems

Zeit: 10:15 Uhr
Hörsaal: A97
 
Dr. Günhan Akarçay
Institute of Applied Physics
University of Bern

 
Mittwoch, 13.01.2016

Acoustic radiation force-mediated localized vibration tagging (LOVIT) for clutter reduction in epi-optoacoustic imaging

Zeit: 10:15 Uhr
Hörsaal: A97
 
Tigran Petrosyan
Institute of Applied Physics
University of Bern