Synthetic and biological nanoparticles combined
to produce new metamaterials

Scientists have succeeded in organising virus particles and other protein cages into crystalline materials with other nanoparticles. Dr Mauri Kostiainen of Aalto University Department of Applied Physics led the research, and the results have now been published in Nature Nanotechnology. The Academy of Finland has funded the study.

Layer structures, or superlattices, of crystalline nanoparticles have been extensively studied in recent years. The research aims to develop hierarchically structured nanomaterials with tuneable optical, magnetic, electronic and catalytic properties.

"Binary nanoparticle lattices have received so much attention because they can provide a way to prepare multifunctional metamaterials – periodic artificial materials not found in nature. In them, new properties arise from collective behaviour," explains Kostiainen.

These nanomaterials are important for applications in sensing, optics, electronics and drug delivery. They can also provide a fundamental understanding to aid the construction of different superlattice structures.

However, so far combinations of both synthetic and biological building blocks in a single structure have remained underutilised.

"Such biohybrid superlattices of nanoparticles and proteins would allow the best features of both particle types to be combined. They would comprise the versatility of synthetic nanoparticles and the highly controlled assembly properties of biomolecules."

In their article in Nature Nanotechnology, the Aalto University-led research group shows that virus or ferritin protein cages can be used to guide the assembly of RNA molecules or iron oxide nanoparticles into three-dimensional binary superlattices. The lattices are formed through tuneable electrostatic interactions with charged gold nanoparticles.

"The gold nanoparticles and viruses adopt a special kind of crystal structure. It doesn't correspond to any known atomic or molecular crystal structure and it has previously not been observed with nano-sized particles."

"Virus particles – the old foes of mankind – can do much more than infect living organisms. Evolution has rendered them with the capability of highly controlled self-assembly properties. Ultimately, by utilising their building blocks, we can bring multiple functions to hybrid materials that consist of both living and synthetic matter," Kostiainen trusts.

Kostiainen and his colleagues also discovered magnetic self-assemblies of ferritin protein cages and gold nanoparticles. These magnetic assemblies can modulate efficiently spin–spin relaxation times of surrounding protons in water by enhancing the spin dephasing and consequently provide contrast enhancement in magnetic resonance imaging (MRI).

The online article provides an in-depth description of this research project:

Youtube video link:

More information:

Mauri Kostiainen, postdoctoral researcher
tel. +358 50 362 7070
Aalto University School of Science
Department of Applied Physics 

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