A team of researchers affiliated with multiple institutions in China, the U.S. and Brazil has used "handedness" in chiral gold nanoparticles to enhance immune response to the influenza virus in mice. The group describes their work in the journal Nature. Alexander Hooftman and Luke A. J. O'Neill have published a News and Views piece describing the work done by the team on this new effort in the same journal issue.

Chirality refers to structures that are asymmetric, which means they have handedness—they are the same but opposite, like human hands. In this new effort, the researchers looked at the ways that the handedness of gold nanoparticlesthey created could impact cell types. They first looked at the impact of circularly polarized light on their gold nanoparticles. Prior research has shown that this type of light impacts left and right handedness differently. They were able to use it to customize the degree of handedness in their nanoparticles. They then looked at how they could use this customization to impact how their nanoparticles would behave when exposed to macrophages or dendritic cells—both play key roles in the initial recognition of foreign proteins in the body, which is a clear sign of an infection.

The researchers found that left-handed nanoparticles were more easily able to enter such cells, though both types engaged equally with CD97 and EMRI, which are important receptor cells. They also found that both eventually went through endocytosis, in which a material is allowed through the cell membrane and into the cell. And once they were in, they both triggered a process that leads to potassium ion channels opening inside of the cell membrane, which leads to activation of proteins that incite inflammation known as inflammasomes. That in turn led to the cells producing cytokines, which are known to mediate immune response. The researchers found that when they injected the nanoparticles into mice infected with the flu, the immune response was stronger for nanoparticles with left handedness than for those with right handedness. They suggest that it might be possible to use this new knowledge regarding handedness to improve vaccines.

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