Researchers investigate how nanoparticles can eliminate bacteria more efficiently

According to a study performed in Brazil, components of biological fluids, such as peptides and sugars, similar to those in blood can form a nanoparticle surface coating and affect the action of nanodrugs.

By Maria Fernanda Ziegler  |  Agência FAPESP – Nanoparticle-based drugs have been considered an important contribution to personalized medicine for more than two decades. Potentially deliverable directly to tumors, infections and inflammations in a patient’s body, nanodrugs enable the combination of ideal dosing with precise targeting of the site of interest.

To make this type of individualized treatment viable, two interconnected problems that can affect the efficiency of nanodrugs have to be surmounted. One is nanoparticle maintenance, which involves colloidal stability. As soon as nanoparticles come into contact with a biological fluid such as blood, their surface potential tends to change. The other problem is the formation of a non-specific coating on the nanoparticle surface via accumulation of smaller molecules such as peptides, sugars and proteins. 

For the first time, Brazilian researchers have succeeded in demonstrating the impact of biological components other than proteins, as these species are usually overlooked in corona formation. In an article featured on the cover of Journal of Materials Chemistry B, Maiara Emer and Mateus Borba Cardoso, researchers at the National Energy & Materials Research Center (CNPEM), show that nanoparticle efficiency is affected by relevant components of the corona besides proteins, such as peptides, sugars and other kinds of molecules. 

Many studies of the protein corona can be found in the literature, and researchers have previously described corona formation by other components. Nevertheless, the fact that the portion of the corona formed by non-proteins has a direct impact on the biological response to nanoparticles has never been shown before. 

“There’s no shortage of research on the protein corona, but all that was known about the biomolecular corona was that it existed and possibly didn’t affect any aspect of nanoparticles. We show, however, that this isn’t the case. It does have an impact, and this shouldn’t be overlooked,” Cardoso told Agência FAPESP.

In the study, silica nanoparticles with different surfaces were incubated with bacterial cultures of Escherichia coli and Staphylococcus aureus in an assay without protein. The medium in which the bacteria were grown contained several biomolecular corona components.

The researchers tested the growth and death of the bacteria and the efficiency of nanoparticles against the bacteria. The results showed a close correlation between biomolecular corona formation and nanoparticle bactericidal effect.

“We observed that nanoparticles with different surfaces adsorb different amounts of these components. Greater or smaller adsorption capacity is associated with the nanodrug’s efficiency in terms of killing bacteria,” Cardoso said.

They also showed that how nanoparticles bind to the components of biomolecular fluids can influence colloidal stability. “Depending on the nanoparticle surface, there may be more or less binding among molecules. This is reflected by the nanoparticles’ capacity to kill bacteria,” he explained.

The researchers are now working on a new strategy to avoid protein and biomolecular corona formation on nanoparticles.

The article “Biomolecular corona formation: nature and bactericidal impact on surface-modified silica nanoparticles” (doi: http://dx.doi.org/10.1039/c7tb01744h) by Maiara Emer and Mateus Borba Cardoso, published in Journal of Materials Chemistry B, can be retrieved from pubs.rsc.org/en/content/articlelanding/2017/tb/c7tb01744h#!divAbstract.