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).
Physics, photosynthesis and solar cells
01.12.2016 | University of California - Riverside
New process produces hydrogen at much lower temperature
01.12.2016 | Waseda University
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,...
Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water
In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...
The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.
Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
02.12.2016 | Medical Engineering
02.12.2016 | Agricultural and Forestry Science
02.12.2016 | Physics and Astronomy