Nuclei are complex, well-defined organelles carrying genetic information that is critical to the cell. Visualizing these organelles through fluorescence imaging techniques promises to reveal the mechanisms that govern genetic information and provide ways to predict and treat genetic diseases.
Working closely with Xinhai Zhang at the A*STAR Institute of Materials Research and Engineering, a research team led by Bin Liu at the National University of Singapore has now developed a method to create ultrasmall, highly selective fluorescent nanoprobes for a cellular nucleus imaging technique known as two-photon excited fluorescence (TPEF) microscopy.
Researchers have proposed a number of fluorescent substances to illuminate nuclei within cells. However, light-induced phenomena, such as cellular autofluorescence and severe photodamage, tend to degrade the performance of these probes.
In the TPEF technique, each nanoprobe produces a fluorescent signal by absorbing not one but two low-energy photons of near-infrared light. This two-photon process significantly reduces the effects of photodamage and cellular autofluorescence while enhancing resolution, making TPEF advantageous over traditional one-photon fluorescence microscopy.
“TPEF imaging is more powerful than one-photon imaging, in particular for in vivo and tissue imaging where strong biological autofluorescence exists,” say Zhang.
Instead of a traditional step-by-step synthesis, the researchers adopted a ‘bottom-up’ approach to synthesize the nanoprobes for their TPEF scheme. These nanoprobes consist of tiny inorganic silicon–oxygen cages surrounded by short positively charged polymer chains. The team obtained cages and chains separately before joining them together, and the synthesis lends itself well to producing TPEF nanoprobes with various light-emission colors and bio-recognition capabilities.
The small, rigid cages facilitate the incorporation of the probes into cellular nuclei, while the positively charged and light-sensitive chains contribute to water-solubility and optical properties. According to Liu, these features combine to ultimately produce TPEF-suitable light-up probes.
The team discovered that the fluorescence of the probes became substantially more intense upon exposure to nucleic acids, such as double-strand DNA and RNA. This is because the positively charged probes bind tightly to the negatively charged nucleic acids through attractive electrostatic interactions, increasing the micro-environmental hydrophobicity of the probes and their fluorescence. Furthermore, the probes selectively stained the nuclei of breast cancer and healthy cells with low toxicity.
The researchers are currently expanding their probe collection to include other intracellular target applications. They are also further optimizing the TPEF performance of the probes. “These nanoprobes can open up new ways of interrogating biological systems in a high-contrast and safe fashion,” say Zhang.
The A*STAR-affiliated researchers contributing to this research are from the Institute of Materials Research and Engineering
 Pu, K.-Y., Li, K., Zhang, X. & Liu, B. Conjugated oligoelectrolyte harnessed polyhedral oligomeric silsesquioxane as light-up hybrid nanodot for two-photon fluorescence imaging of cellular nucleus. Advanced Materials 22, 4186–4189 (2010).
New design improves performance of flexible wearable electronics
23.06.2017 | North Carolina State University
Plant inspiration could lead to flexible electronics
22.06.2017 | American Chemical Society
Computer scientists use wave packet theory to develop realistic, detailed water wave simulations in real time. Their results will be presented at this year’s SIGGRAPH conference.
Think about the last time you were at a lake, river, or the ocean. Remember the ripples of the water, the waves crashing against the rocks, the wake following...
An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.
Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...
Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.
Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...
Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.
As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...
Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.
With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...
19.06.2017 | Event News
13.06.2017 | Event News
13.06.2017 | Event News
29.06.2017 | Physics and Astronomy
29.06.2017 | Life Sciences
29.06.2017 | Health and Medicine