More than 40 years ago, the foundation for optical tweezers was laid when Arthur Ashkin demonstrated that near the focus of a laser beam, momentum transfer between light and dielectric particles creates gradient forces large enough to pull the particle into the center of highest intensity and scattering forces that push it in the propagation direction of the beam.
Optical trapping of microparticles and cells can be established either by balancing the axial forces of two weakly-focused counter-propagating beams or by using a single tightly focused laser beam. These optical tweezers have developed into an important tool in cell biological research. Optical tweezers can be used not only to fix cells during manipulation but also to investigate the interconnection of a cell’s elasticity to its physiology: healthy and diseased cells differ notably in their mechanical responses, prominent examples being blood disorders, asthma and cancer.
Researchers from Max Planck Institute for the Science of Light, Erlangen, Germany now report a new tool for biomechanical studies of individual cells: Single red blood cells were laser-propelled through stationary liquid in a microfluidic channel over distances of up to 24 cm. Shear forces on the cell surface result in its deformation. This causes changes in speed that can conveniently be monitored using a non-imaging laser Doppler-velocimetric technique. Numerical simulations allowed the scientists to derive the optical force acting on different cell shapes.
Interestingly, the deformations occur over timescales of minutes which is rather slow compared to other cell rheological techniques. Re-arrangements of the cytoskeleton might be involved.
The scientists are currently aiming at studying suspended eukaryotic (cancer) cells. These cells are typically ellipsoidal in shape and more rigid than red blood cells, which prevents them from undergoing peculiar changes in shape.
Simulations of the optical forces would be possible, allowing for a complete theoretical analysis of the system. Beyond that, the method may find applications in on-chip cell transport. Cells might be held stationary against a mild counterflow carrying precise amounts of medical drugs.
Moreover, cell-cell interactions between suspended cells might be studied. (Text contributed by K. Maedefessel-Herrmann)
Unterkofler, S., et al; J. Biophotonics 6(9), 743-752 (2013); DOI http://dx.doi.org/10.1002/jbio.201200180
Journal of Biophotonics publishes cutting edge research on interactions between light and biological material. The journal is highly interdisciplinary, covering research in the fields of physics, chemistry, biology and medicine. The scope extends from basic research to clinical applications. Connecting scientists who try to understand basic biological processes using light as a diagnostic and therapeutic tool, the journal offers a platform where the physicist communicates with the biologist and where the clinical practitioner learns about the latest tools for diagnosis of diseases. JBP offers fast publication times: down to 20 days from acceptance to publication. Latest Journal Impact Factor (2012): 3.099 (ISI Journal Citation Reports 2012)Regina Hagen
Regina Hagen | Wiley-VCH
Closing the carbon loop
08.12.2016 | University of Pittsburgh
Newly discovered bacteria-binding protein in the intestine
08.12.2016 | University of Gothenburg
In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.
Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
08.12.2016 | Life Sciences
08.12.2016 | Physics and Astronomy
08.12.2016 | Materials Sciences