Gold Nanoparticles May Make Vaccines More Effective

Could chiral gold solve the adjuvant problem?

A recent study published in the peer-reviewed journal Nature by an international team of 19 scientists based in China, Brazil, and the United States, found that chiral gold nanoparticles can act like keys to the immune system, turning on a potentially robust immune response.

What Are Nanoparticles?

Nanoparticles are very tiny structures of matter. Researchers have become particularly interested in them because there are nanoparticles that are harmful, like plastic nanoparticles that can invade the body and harm human and animal health and nanoparticles in sunscreen that can similarly get into the body and problems. At the same time, scientists are learning to make an use nanoparticles to potentially improve medicine and health. Though they are very small, nanoparticles are still much larger than molecules. And, like molecules, they can be chiral.

What Does Chiral Mean?

Nanoparticles aren’t just strings of atoms: They have a 3D shape. Sometimes the same atoms can make up the same kind of molecule, but in the mirror image, like your right hand and your left hand.

Scientists call these forms “chiral,” from the Greek word for “hand.” This is complicated but stay with me. Some nanoparticles can come in both left and right-hand versions. When they do, they are called enantiomers, meaning opposites. These nanoparticle pairs sometimes work the same in living systems—and your body often does not differentiate them—but in living systems enantiomers can sometimes act very differently, even dangerously so.

Think of a pair of nice leather driving gloves. One fits only on the right hand. One fits only on the left. Enantiomers are nanoparticles like these gloves. Now think of a pair of ugly blue surgical gloves, shaped symmetrically and designed for single use. These surgical gloves have the thumb straight off the side so they fit either hand. In other words, they are no-handed. Scientists call these “no-handed” nanoparticles “achiral.”

Screenshot from a January 2022 article in the Journal Nature Reviews Chemistry, “Self-assembled inorganic chiral superstructures,” that explains chiroptical properties and applications

The Experiment Published in Nature

These scientists created nanoparticles that contained small amounts of gold. As they were forming the gold nanoparticles, the researchers shone polarized light on the atoms to push the particles into the left or right-hand forms. Polarized light uses filters just like polarized sunglasses. Instead of light waves wiggling every which way, which is how natural light behaves, a polarized filter only lets through light that is all lined up in the same direction. The lined-up light, when shined on the atoms as they formed into nanoparticles, pushed the nanoparticles into one shape or another.

Creating nanoparticles in this way allowed the scientists to study how they behaved. And what they found was that the left-hand particles acted differently from the right-handed ones, both in Petri dishes and in a living system.