Gold nanoparticles could be a safe tool for improving the effectiveness of vaccines and other medicines that need to target the B cells of the immune system, according to new research.

The number of medical uses for nanoparticles has grown steadily over the last 20 years. However, doctors and scientists remain concerned about their safety and how they might affect the immune system.

The human body tolerates gold well, and the metal is easy to manipulate. In the form of nanoparticles, gold offers the potential to target cells in specific ways. Drug delivery in precision medicine could be a promising area. Previous studies have already established that gold nanoparticles can work with larger immune cells, such as macrophages, in safe, biocompatible ways.

Now, for the first time, scientists have investigated how gold nanoparticles interact with B lymphocytes, or white blood cells, which are smaller and less easy to manage. The new study is the work of researchers from Switzerland and the United Kingdom, and it features in a recent ACS Nano paper.

B cells are largely responsible for the production of antibodies in the immune system.

"Nanoparticles," says co-senior study author Carole Bourquin, a professor in the faculties of medicine and science at the University of Geneva in Switzerland, "can form a protective vehicle for vaccines—or other drugs—to specifically deliver them where they can be most effective while sparing other cells."

Effect of gold nanoparticles on B cells

Bourquin and her colleagues investigated interactions between different forms of gold nanoparticles and "freshly isolated human B lymphocytes."

They ran experiments in which they exposed the B cells to coated and uncoated rod-shaped and spherical gold nanoparticles. By observing activation markers on the B cell surfaces, the team could see the extent to which the different types of nanoparticle activated or inhibited immune responses.

None of the gold nanoparticle types that the team tested produced adverse side effects. However, the nanoparticles differed in terms of their ability to produce an immune response.

The researchers found that the type of surface on the gold nanoparticles and their shape had a significant effect on their interactions with B cells. Uncoated spherical gold nanoparticles proved unsuitable because they showed a tendency to form clumps. The best performers were the polymer-coated, spherical gold nanoparticles. These were stable and did not interfere with the function of the B cells.

Rod-shaped gold nanoparticles, on the other hand, were not usable because they reduced the immune response rather than activating it. The researchers suggest that this could be because they were heavier and likely interfered with processes in the cell membranes.

Potential of gold 'nanodrugs'

To be effective, vaccine drugs need to reach B cells before the body destroys them. Using gold nanoparticles to deliver them could be an effective way to preserve the drugs during their perilous journey to their targets.

B cells can be targets not only for vaccines but also for drugs that treat other diseases, such as cancer and autoimmune conditions.

The researchers see the gold nanoparticles that they have developed as a potential vehicle for delivering drugs directly to B cells. Such a delivery vehicle could reduce the dosage of drugs and their associated side effects.

Gold nanoparticles are potentially ideal delivery vehicles for brain cancer drugs because they are small enough to pass through the blood-brain barrier. Investigations into how to use nanoparticles to help treat brain tumors are already underway.

Another potentially useful property of gold nanoparticles is that they can absorb light and then release the energy as heat. This feature could make the nanoparticles an ideal tool for precision therapy in cancer. Doctors could target gold nanoparticles to enter tumors, then shine a light on them so that they selectively destroy the cancer cells with heat.

An important feature of the study is that the team developed a systematic approach for investigating the safety and compatibility of nanoparticles with B cells. No study prior to this had used this methodology.

"This could be especially useful for future research, as the use of nanoparticles in medicine still requires clear guidelines."

—Professor Carole Bourquin