Now! Gold nanocages could image and treat tumours

Gold has been used in medicine for centuries, but nanotechnology has given it an entirely new role. Researchers led by Younan Xia at Washington University in St. Louis have developed hollow gold nanostructures — called nanocages — that could simultaneously image tumors and deliver drugs to destroy them, all in a single platform.

The nanocages are extraordinarily small, about 50 nanometers in size, and their hollow interiors can be loaded with drug molecules. Their gold walls can be engineered to absorb near-infrared (NIR) light — wavelengths that pass through tissue relatively easily. When NIR light hits the nanocages, two things happen: they emit Cerenkov radiation that can be detected in imaging, and they convert the light to heat, which can kill nearby tumor cells through photothermal therapy.

The Cerenkov Imaging Advantage

Cerenkov luminescence imaging is a relatively new technique that detects visible light emitted when charged particles (like those from radioactive tracers) travel through tissue faster than light does in that medium. By incorporating gold-198 — a radioactive isotope — directly into the walls of the nanocages, the team created particles that are self-labeling. The gold-198 provides both the imaging signal and becomes a permanent, structural part of the nanocage. Because the isotope is built into the cage wall rather than chemically attached, there's no risk of it separating from the nanoparticle during treatment — a common concern with conventional nanoparticle labeling approaches.

Drug Delivery and Combination Therapy

The hollow interior of the nanocages can be filled with chemotherapy drugs or other therapeutic agents. By attaching targeting molecules like peptides to the outer surface, the team hopes to direct the nanocages specifically to tumor cells, minimizing harm to healthy tissue. Once at the tumor site, the nanocages could deliver drugs, apply photothermal heat, or both simultaneously.

This kind of multifunctional nanoparticle — one that can image, target, and treat — represents the direction that cancer nanomedicine is heading. Combining diagnosis and therapy in a single agent, sometimes called theranostics, could make cancer treatment more precise and more efficient than approaches that handle imaging and treatment as separate steps.

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Source: Physics World

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Pico-gold clusters break catalysis record!!!

Clusters of just three gold atoms have exceptional
 catalytic activity ©

Chemists in Spain have shown that small clusters of gold atoms are excellent inorganic catalysts with record-breaking efficiency. The clusters, which have been used in the hydration of alkynes, exhibit catalytic turnover frequencies of up to 100,000 per hour at room temperature.

Interest in gold as a catalyst began 25 years ago when chemists realized that nano-sized gold particles could catalyse the oxidation of carbon monoxide better than anything previously known. Since then, gold has been found to catalyse a host of other important reactions, such as the formation of azo compounds, which are used as leather and textile dyes, or intermediates for the production of polyurethane.

But for the most part, industry hasn’t yet turned to gold as a catalyst. The problem is that a lot of the precious metal is required – loadings of about 5% by mole for just a few hundred milligrams of substrate. For this reason, interest in gold as a catalyst has remained primarily academic.




The researchers focused on the ester-assisted hydration of alkynes. In this reaction water turns alkynes into ketones; it used to be used by industry to form acetaldehyde for the production of acetic acid and other chemicals from acetylene using a mercury catalyst.


The Valencia chemists formed the gold clusters by adding the reactant substrate to a solution of gold chloride (AuCl) or chloroauric acid (HAuCl₄). Using ultraviolet spectroscopy and matrix-assisted laser–desorption–ionisation-time-of-flight (MALDI) mass spectroscopy, they found that the reaction began when clusters of between three and five gold atoms formed. Then the reaction proceeded swiftly, with a turnover frequency of 100,000 – that is, converting 100,000 substrate molecules per gold cluster per hour. Such catalytic activity is nearly five orders of magnitude higher than that previously reported, the researchers claim.

‘The higher the dilution, the better the formation of the clusters, [so] extremely low amounts of gold are sufficient to catalyse the reactions,’ says Corma. ‘Clusters are rearranging [with] time in the reaction mixture – but each reaction needs a type of cluster, i.e. a number of atoms of gold clustered, so control of the formation of [a] particular cluster would lead to an even more efficient process.’

The high catalytic turnover ‘is of significance for industrial applications’, says Stephen Hashmi, an organic chemist at Heidelberg University in Germany. ‘The fact that this is possible at room temperature is nice but, as most chemical engineers will confirm, for industrial reactors … room temperature reactivity is not crucial, [and] slightly higher temperatures are preferred.’

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