A separation method that isolates protein-protected gold clusters enables improved sensing of toxic mercury compounds and pesticides.
Fluorescence-based detection of pesticides and other environmentally harmful chemicals is limited by the ability of current methods to reliably and selectively sense specific chemical species. A*STAR researchers have now developed a co-precipitation process that removes excess reagents to improve the efficiency of fluorescent sensors.
Schematic illustrations and fluorescence images depicting the purification of BSA-protected gold (Au25) clusters through the centrifugation and removal of free BSA (green squiggles).
Reproduced, with permission, from Ref. 1 © 2014, Royal Society of Chemistry
The fluorescence properties of protein-protected gold clusters make them useful for detecting and sensing various chemical species, such as hydrogen peroxide and mercury. However, the detection sensitivity is hampered by any free protein molecules that remain in the cluster solution, as these proteins may reduce the fluorescence or interact with the chemical species under detection. Commonly used methods for isolating protein-protected gold clusters (for example, ultracentrifugation, chromatography and dialysis) are often blighted by practical problems such as solubility issues or insufficient separation if the protein is too large or similar in size to the protected metal clusters.
Ming-Yong Han, Yong-Wei Zhang and colleagues at the A*STAR Institute of Materials Research and Engineering, the A*STAR Institute of High Performance Computing and the National University of Singapore have discovered a simple way to remove excess bovine serum albumin (BSA) from a solution of BSA-protected gold (Au25) clusters following modification of the clusters.
Their separation method involves the co-precipitation of Au25 clusters and zinc hydroxide in a basic solution, followed by centrifugation and removal of the supernatant, which contains the free BSA (see image). When re-dispersed in buffer solution, the precipitate forms a transparent solution of BSA-protected gold clusters.
Han’s team proposes that the co-precipitation process involves the binding of hydroxide ions with the surface Au(I) ions of the clusters and the subsequent interaction between zinc ions and hydroxide ions, resulting in zinc hydroxide being precipitated.
The mechanism is also effective using copper (II), cadmium (II) and lead (II) ions in strong, basic solutions and leads to the formation of the corresponding metal hydroxides.
“Once purified, the BSA-protected clusters are highly sensitive in detecting hydrogen peroxide and mercury ions and prove to be a visually selective detection method for four different pesticides,” says Han.
In the future, the team intends to investigate the use of the surface-binding interactions to grow gold nanoparticles from the clusters. “We also hope to use the purified clusters to develop new fluorescent sensors that have a high sensitivity and selectivity,” explains Han. “Moreover, we plan to extend the purification method to other clusters, such as platinum and silver, and study their atomic structure and potential for enhanced performance in sensing and detection applications.”
1. Guan, G., Zhang, S.-Y., Cai, Y., Liu, S., Bharathi, M. S. et al. Convenient purification of gold clusters by co-precipitation for improved sensing of hydrogen peroxide, mercury ions and pesticides. Chemical Communications 50, 5703–5705 (2014).
Lee Swee Heng | Research SEA News
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