Sticky gold

Scientists at the US Department of Energy’s Brookhaven National Laboratory have managed to attach gold nanoparticles to proteins to form sheets of protein-gold.


The technique of attaching nanoparticles to protein can be used to analyse protein structures, identify functional parts of proteins and to ‘glue’ together new protein complexes. The researchers suggested possible applications including catalysts that convert biomass to energy, to the targeted delivery of drugs in the body.


‘Our study demonstrates that nanoparticles are appealing templates for assembling functional biomolecules with extensive potential impact across the fields of energy conversion, structural biology, drug delivery and medical imaging,’ said Minghui Hu, a PhD student working on the project at the Brookhaven Lab.


The creation of single layers of densely packed enzymes, which make up the functional part of catalytic electrodes used to convert organic fuels such as ethanol to electricity, has previously been a challenge to scientists.


With the new technology, however, scientists can ‘glue’ enzymes together using the gold nanoparticles to form ordered single layers stable enough to be transferred onto a solid surface, such as an electrode, to be used in energy conversion.


Hu explained how he and his team manipulated size-controllable nanoparticles coated with organic molecules designed to react with specific protein sites.


‘First, we designed the specific interactions between gold nanoparticles and the proteins by coating the gold nanoparticles with functional organic molecules using a biocompatible linker. Then we added a genetically engineered sequence of peptides, called a ‘tag’, to the protein molecule, which acted as the binding site for the gold nanoparticles. Finally, we incubated the nanoparticles with the protein solution to allow the nanoparticles and proteins to bind, transferred the solution onto a transmission electron microscopy grid, and analysed the complexes using electron microscopes.’


The scientists tried out the technology in a biomedical environment.


In the main study, the scientists attached gold nanoparticles to an enzyme complex that helps drug-resistant tuberculosis bacteria survive. With further research, they hoped to develop the process by tailoring the nanoparticles to inactivate the enzyme complex, thus combating drug-resistant TB.


In another part of the study, the researchers used proteins found on the surface of adenovirus, which causes the common cold by binding to the human cells it infects. They suggested that modified forms of adenovirus could be used to transport drugs to target specific cells, such as those that make up tumours.


In order to carry our efficient drug delivery, the binds to the target cells would have to be enlargened and made stronger, which the scientists did by attaching multiple viral proteins to the gold nanoparticles.


When used to study proteins, the scientists found that they were able to better analyse the structure and regions of protein molecules that carry out all the functions of living cells, the break down of which can lead to disease.


According to the researchers, by adding nanoparticles, the resolution of the imaging technique known as cryo-electron microscopy increased significantly. The benefits of this could be employed in the analysis of small biological macromolecules and complexes that are currently being analysed using cryo-electron microscopy or x-ray crystallography.