Multifunctional microcapsules made from metals and tannic acid
Microcapsules with a broad spectrum of applications in biomedicine, catalysis, and technology can be produced by using plant-derived, phenolic tannic acid and a variety of metals. The capsules are formed by a simple self-assembly process, and their properties can be controlled through the choice of metal, as demonstrated by a team of Australian and German researchers in the journal Angewandte Chemie.
Metals and organic molecules can combine to form coordination compounds whose structure and properties depend on the components. Examples from nature include the oxygen-binding heme groups in our red blood cells with their central iron atom or the magnesium complex at the heart of photosynthesis. Scientists have also explored the use of these types of compounds to build things, such as networked scaffold structures.
A team from the University of Melbourne, the Baker IDI Heart and Diabetes Institute (Melbourne, Australia), and the University Medical Center Freiburg (Germany), is particularly interested in structures in the form of hollow capsules. Led by Frank Caruso, these researchers haven now been able to demonstrate that a single organic ligand, tannic acid, can coordinate to 18 different metals to form capsules made of metal–phenolic networks (MPNs). The metals are aluminum, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, zirconium, molybdenum, ruthenium, rhodium, cadmium, cerium, europium, gadolinium, and terbium.
The production method is simple: just mix tannic acid with a solution of the desired metal ion in the presence of a suitable substrate—in this case microparticles. Removal of the substrate leaves behind hollow microcapsules.
The properties of the capsules depend on the type and number of metal ions. For example, capsules with aluminum have a property profile suitable for drug transport: while they are relatively stable at pH values typical of blood, they come apart at the lower pH values found in some cell compartments. They could thus be used to transport a drug though the blood and release it after entering a cell.
Capsules with europium and terbium ions can be used for multicolored fluorescence labeling of biological samples, as well as for technological applications like flexible color displays. Capsules with manganese are highly promising contrast agents for magnetic resonance imaging (MRI). Capsules with radioactive copper isotopes are good tracers for positron emission tomography (PET). Properties like size, shape, and surface chemistry could be tailored to control the distribution of the capsules in the body. Capsules with radioactive copper and europium could allow for tissue samples to undergo PET followed immediately by fluorescence microscopy.
Catalysis is another possible application. The researchers were able to show that capsules with rhodium catalyze the hydrogenation of quinoline at least as well as conventional rhodium catalysts.
About the Author
Frank Caruso is a professor and Australian Research Council (ARC) Laureate Fellow at The University of Melbourne, Australia. He is also a Director of the ARC Centre of Excellence in Convergent Bio-NanoScience and Technology and is a Fellow of the Australian Academy of Science. His research interests focus on developing advanced nano- and biomaterials.
Author: Frank Caruso, University of Melbourne (Australia), http://www.chemeng.unimelb.edu.au/people/staff.php?person_ID=16579
Title: Engineering Multifunctional Capsules through the Assembly of Metal–Phenolic Networks
Angewandte Chemie International Edition, Permalink to the article: http://dx.doi.org/10.1002/anie.201311136
Frank Caruso | Angewandte Chemie
Cells migrate collectively by intermittent bursts of activity
30.09.2016 | Aalto University
The structure of the BinAB toxin revealed: one small step for Man, a major problem for mosquitoes!
30.09.2016 | CNRS (Délégation Paris Michel-Ange)
Heavy construction machinery is the focus of Oak Ridge National Laboratory’s latest advance in additive manufacturing research. With industry partners and university students, ORNL researchers are designing and producing the world’s first 3D printed excavator, a prototype that will leverage large-scale AM technologies and explore the feasibility of printing with metal alloys.
Increasing the size and speed of metal-based 3D printing techniques, using low-cost alloys like steel and aluminum, could create new industrial applications...
Friction stir welding is a still-young and thus often unfamiliar pressure welding process for joining flat components and semi-finished components made of light metals.
Scientists at the University of Stuttgart have now developed two new process variants that will considerably expand the areas of application for friction stir welding.
Technologie-Lizenz-Büro (TLB) GmbH supports the University of Stuttgart in patenting and marketing its innovations.
Friction stir welding is a still-young and thus often unfamiliar pressure welding process for joining flat components and semi-finished components made of...
Optical quantum computers can revolutionize computer technology. A team of researchers led by scientists from Münster University and KIT now succeeded in putting a quantum optical experimental set-up onto a chip. In doing so, they have met one of the requirements for making it possible to use photonic circuits for optical quantum computers.
Optical quantum computers are what people are pinning their hopes on for tomorrow’s computer technology – whether for tap-proof data encryption, ultrafast...
The Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP has been developing various applications for OLED microdisplays based on organic semiconductors. By integrating the capabilities of an image sensor directly into the microdisplay, eye movements can be recorded by the smart glasses and utilized for guidance and control functions, as one example. The new design will be debuted at Augmented World Expo Europe (AWE) in Berlin at Booth B25, October 18th – 19th.
“Augmented-reality” and “wearables” have become terms we encounter almost daily. Both can make daily life a little simpler and provide valuable assistance for...
With the help of artificial intelligence, chemists from the University of Basel in Switzerland have computed the characteristics of about two million crystals made up of four chemical elements. The researchers were able to identify 90 previously unknown thermodynamically stable crystals that can be regarded as new materials. They report on their findings in the scientific journal Physical Review Letters.
Elpasolite is a glassy, transparent, shiny and soft mineral with a cubic crystal structure. First discovered in El Paso County (Colorado, USA), it can also be...
30.09.2016 | Event News
29.09.2016 | Event News
28.09.2016 | Event News
30.09.2016 | Materials Sciences
30.09.2016 | Earth Sciences
30.09.2016 | Life Sciences