Research Highlights

A simple but powerful technique for producing virus-like nanoparticles that have chemically ‘patchy’ surfaces has been developed by an AIMR researcher and collaborators¹. Such nanoparticles promise to be useful for a wide range of applications, including cell delivery and photonic materials.

Viruses range in size from about 20 to 400 nanometers. Scientists have been able to create artificial nanoparticles in the same size range, but the surfaces of such nanoparticles are typically chemically uniform. In contrast, the surfaces of viruses are highly variable. Producing artificial nanoparticles that have chemically variable surfaces would greatly enhance their applicability in many areas.

“Chemically modified patchy nanoparticles are important not only for creating functional nanomaterials for efficient catalysts and biosensors, but also for enabling us to control the nanoscale features of synthetic polymer particles to be like a virus,” says Hiroshi Yabu of the AIMR at Tohoku University.

Now, Yabu and colleagues have come up with a straightforward method for producing such chemically patchy nanoparticles. It involves dissolving molecules consisting of two different polymers, each with a functional chemical group attached, in an organic solvent. Since the polymers are hydrophobic, when water is added and the organic solvent is evaporated, the polymer molecules are forced together so that they form nanoparticles made up of the two polymers. They do this in such a way that molecules of the same polymer tend to clump together.

The distribution of the two polymers in the nanoparticles can be controlled by varying the preparation conditions. For example, stripy nanoparticles made up of alternating disks of polymers (see image), nanoparticles with circles on their surfaces, and nanoparticles with an onion-layer structure can be fabricated by varying the conditions, such as the polymer concentration.

By attaching a fluorescent dye to one of the polymers, the researchers were able to obtain images of the various nanoparticle structures.

“This method for producing functional nanostructured particles brings us one step closer to interfacial mimics of natural nanoparticles, and as such, may give access to interesting materials for fundamental biological studies or biotechnological uses,” notes Yabu.

The functional chemical groups protrude from the surface of the nanoparticles and can be easily modified through chemical reactions. This opens up a wide range of exciting possibilities.

The team plans to explore the potential of these nanoparticles. “We intend to chemically modify nanoparticles with enzymes and antibodies so that they can be used as biosensors for immunoassays and as intelligent drug carriers,” says Yabu. “Furthermore, we hope to use them as templates for chemical catalysts that have arrays of different enzymes for realizing cascade reactions like those that occur in living bodies.”