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Bovine blood keeps gold nanoparticles stable

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Two vials in a Rice University lab show gold nanoparticles in saline water. At left, the nanoparticles have been stabilized in bovine serum albumin and are dispersed in the solution. At right, without albumin, the nanoparticles clump together and sink to the bottom. (Image Credit: Rice University; Photo by Sergio Dominguez-Medina/Link Research Group)

A protein from cow blood has the remarkable ability to keep gold nanoparticles from clumping in a solution. The discovery could lead to improved biomedical applications and contribute to projects that use nanoparticles in harsh environments. Bovine serum albumin (BSA) forms a protein “corona” around gold nanoparticles that keeps them from aggregating, particularly in high-salt environments like seawater. The new research was conducted by Rice University chemists Stephan Link and Christy Landes. Link’s primary interest is in the plasmonic properties of nanoparticles. Landes’ work incorporates protein binding and molecular transport. The BSA research combines their unique talents with those of Sergio Dominguez-Medina, a graduate student in Link’s lab who studied to be a physicist at Monterrey Tech and was drawn to this interdisciplinary project during an undergraduate fellowship at Link’s Rice lab. IInitially, we wanted to look at nanoparticles in solution with something they would encounter frequently in blood: serum albumin,” Landes said. “In our first experiments, Sergio reported the very efficient, reasonably fast and irreversible binding the moment he put nanoparticles into a solution that contained serum albumin.” “It turned out the salt is actually driving this binding,” Dominguez-Medina said. Without BSA, gold nanoparticles in a salty solution quickly aggregate and fall to the bottom. “That by itself is undesirable for biomedical or industrial applications, because it could lead to toxicity issues,” he said. “The nanoparticles get more hydrophobic because in the presence of salts, the excess charges on the surface (which discourage clumping) are actually removed.” But if BSA is present, the proteins are drawn to the nanoparticles faster than the particles are drawn to each other. “Once the protein is bound, it gives a super protection against any type of salt-induced aggregation. We think this could be used for the stabilization of nanoparticles in environments where, right now, it hasn’t been achieved,” Dominguez-Medina said. He said the discovery also offers the possibility that nanoparticles might be made more compatible for treating humans by using a patient’s own albumin. “Albumin is really easy to purify and the process is well-established,” he said.