Group synthesizes gold particles for potential use in nanomedicine

Goal of research carried out in Brazil and presented in Germany is to study the interaction between nanoparticles and proteins

By Karina Toledo, in Munich

Agência FAPESP – The synthesis of ultrasmall gold particles with potential applications in nanomedicine is the goal of a FAPESP-funded project being carried out at the Federal University of São Paulo (Unifesp).

Preliminary data were presented by Prof. Alioscka Sousa of the Department of Biochemistry on Thursday (10/16/14) in Germany, during FAPESP Week Munich.

“Several groups have worked with 10 or 22 nanometer (nm) gold particles. Our goal is to synthesize particles that measure less than 3 nm because in vivo studies by other researchers have shown that these are small enough to be excreted by the kidneys and therefore do accumulate in the body,” Sousa said in an interview with Agência FAPESP.

According to the researcher, data from the scientific literature reveals that this type of metal particle, despite its small size, demonstrates a certain preference for lodging in tumor tissue where there is rich vasculature and little lymphatic drainage.

Although its potential therapeutic use has not yet been tested in vivo, theory suggests that the ultrasmall metal particles could serve as carriers of cancer-fighting drugs.

“One concern of our project is in synthesizing extremely uniform spherical particles because we think that slight differences in size could have different biological effects. Up to now, most of the studies published by other groups have shown the particles to be generally quite heterogeneous,” Sousa said.

To characterize the particle after synthesis, the Unifesp team uses techniques such as scanning electron microscopy and analytical ultracentrifugation. Together, these methodologies allow high-resolution detection of small differences in size and shape.

Sousa explained that another important aspect to be considered is the chemical composition of the particle’s surface, since it along with size is a factor that determines how the particle behaves in the biological medium.

“All metal particles need an organic layer that give them solubility. In our project, we propose adorning the surface of the particles with different combinations of small peptides – having only three amino acids – and studying how this modifies the protein interaction,” the researcher explained.

To study the interaction between the metal particles and different model proteins, the group uses several biophysical techniques. In particular, it has tested a methodology known as surface plasmon resonance (SPR) – normally used in studies that seek to reveal the interaction between two proteins.

“The equipment allows us to calculate the affinity as well as the kinetic velocity with which the interaction occurs, if it occurs. We are already conducting initial tests,” he said.

The experiments have benefited from the collaborative efforts of researcher Peter Schuck from the National Institute of Biomedical Imaging and Bioengineering – one of the bodies associated with the National Institutes of Health (NIH), in the United States.

“From the standpoint of basic science, we are trying to understand how the biological activity is affected by changing the structure of the particle – whether it be its size, shape or its surface chemistry. We believe that this knowledge could be useful in the future to develop nanoparticles that have better biological responses,” the researcher said.

Magnetic nanoparticles

On the same panel devoted to the topic of nanotechnology and photonics, researcher Stefan Lyer, Deputy Head of the Division of Experimental Oncology and Nanomedicine of the Department of Otorhinolaryngology of the University Hospital Erlangen, Germany, presented the findings of a project whose goal was to develop magnetic nanoparticles to be used as carriers of cancer-fighting drugs.

“We are synthesizing magnetic nanoparticles with an iron oxide nucleus and a biocompatible outside layer. The particles are stabilized and used to carry chemotherapy drugs. The idea is that they can deliver large concentrations of medicines directly to the tissue affected by the tumor,” he explained.

The safety and effectiveness of the method have already begun to be tested in pre-clinical trials. In the event that new clinical trials are successful, it is believed that the technology could reduce the costs and side effects of cancer treatment, in addition to increasing its effectiveness.