Biomedical scientists are dreaming of a technique showing the distribution of all the biomolecular constituents that make up biological tissue in high-resolution, three-dimensional maps. Such a visualization tool does not currently exist. Whereas fluorescence and refraction based techniques will never be able to identify an arbitrary molecular compound in tissue, vibrational imaging techniques offer much more promise.
They work label-free and non-invasively and they are able to identify many important groups.
The conventional vibrational imaging technique is Raman microscopy. Practical limitations have so far prevented Raman microscopy from reaching its full potential. The most important limitation is speed. The intrinsically weak Raman signals severely limit the achievable image acquisition rate. The development of coherent Raman scattering (CRS) microscopy techniques over the last decade has resulted in important steps toward resolving the speed issue.
In a feature article, Eric O. Potma and a team of scientists at the University of California (Irvine, USA) discuss several ways in which the improved speed of CRS microscopy has transformed the biomedical imaging field and touch on some of the challenges that lie ahead in moving towards the realization of a more generally applicable visualization technique.
Stronger signals are obtained because in CRS the molecules are driven coherently, which makes them radiate in unison. The resulting signal is coherently amplified through constructive interference in a well-defined, phase-matched direction which enables efficient detection of the Raman response.
For instance, when the microscopic focal volume is filled with lipids, the number of detected photons in coherent anti-Stokes Raman scattering (CARS), generated from the CH2 stretching mode, can easily exceed 102 per microsecond at 10 mW of illumination. With such high signal levels, real-time Raman imaging of biological tissues becomes feasible.
An important application of high speed CRS imaging is the visualization of large tissue segments. For example, neural injuries and myelination disorders in live spinal tissues have been mapped as well as atherosclerotic plaques in aortas. Tissue maps were generated that cover up to several centimeters in lateral and hundreds of microns in axial distance, while preserving the (sub-)micrometer resolution offered by the high numerical aperture objective.
The intrinsic movement of the tissue, due to pulsation of blood vessels, breathing, or positional adjustments by the subject, poses a challenge when imaging living tissues. Imaging at video-rate enables image acquisition in which the individual frames show minimal blurring due to movements. Another advantage of fast imaging is the reduction of possible photodamage in living tissues. Besides live tissue imaging in small animal models, CRS imaging has already been applied to the examination of human skin in vivo.
In addition, the fast imaging modalities enable a time- and space-resolved view of dynamic processes of biological relevance. Water diffusion in neutrophile cells, the dynamics of intracellular droplets, and the diffusion of pharmaceutically relevant agents through skin are examples of dynamic processes that have been visualized.
Single frequency CARS and SRS have already proven indispensable in the study of lipids and lipid metabolism in live tissues and cells. Because of its imaging speed and chemical contrast, CRS has pushed the concept of label-free and noninvasive chemical imaging closer to clinical biomedical applications. The challenge ahead is to marry the speed qualities of single frequency scanning with the superior spectral information of broadband Raman spectroscopy. Recent developments suggest several approaches by which this could occur and provide a glimpse toward the ideal of clinically relevant, real-time chemical inspection of live tissues.(Text contributed by K. Maedefessel-Herrmann)
Regina Hagen | WILEY-VCH Verlag
Cryo-electron microscopy achieves unprecedented resolution using new computational methods
24.03.2017 | DOE/Lawrence Berkeley National Laboratory
How cheetahs stay fit and healthy
24.03.2017 | Forschungsverbund Berlin e.V.
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
24.03.2017 | Materials Sciences
24.03.2017 | Physics and Astronomy
24.03.2017 | Physics and Astronomy