Scientists from Russia and Switzerland have probed into nanostructures covering
the corneas of the eyes of small fruit flies. Investigating them the team
learned how to produce the safe biodegradable nanocoating with antimicrobial,
anti-reflective, and self-cleaning properties in a cost-effective and
eco-friendly way. The protection coating might find applications in diverse
areas of economics including medicine, nanoelectronics, automotive industry,
and textile industry. The article describing these discoveries appears in
Nature.
Scientists
from Far Eastern Federal University (FEFU, Russia) teamed up with colleagues
from University of Geneva, The University of Lausanne, and Swiss Federal
Institute of Technology in Zurich for an interdisciplinary research project
during which they were able to artificially reproduce the nanocoating of the
corneas of fruit flies (Drosophila flies) naturally designed to protect the
eyes of the insects from the smallest dust particles and shut off the
reflection of light.
The craft
of nanocoating meets demands in various fields of economics. It can wrap up any
flat or three-dimensional structure, and, depending on the task, give it
anti-reflective, antibacterial, and hydrophobic properties, including
self-cleaning. The latter, for example, is a very important feature for
expensive reusable overnight ortho-k lenses that correct the eyesight. Similar
anti-reflective coatings are already known though created by more complex and
costly methods. They are being used on the panels of computers, glasses,
paintings in museums can be covered with them in order to exclude reflection
and refraction of light.
“We are
able to produce the nanocoating in any required quantity given that its design
is more cost-effective compared to the modern methods of manufacturing similar
structures. The work with natural components requires no special equipment nor
significant energy consumption and constraints of chemical etching,
lithography, and laser printing,†Vladimir Katanaev explains, the head of the
research and Head of the Laboratory of Pharmacology of Natural Compounds in the
School of Biomedicine of FEFU.
“The
development has broad applications. For example, it could be the structural
dying of textiles that would change the color depending on the angle of view.
It is possible to create a disguise coat based on metamaterials, an
antibacterial layer for medical implants, and a self-cleaning coating for
contact lenses and windshields. We also believe that if we reinforce the
nanocoating, it might be utilized as a basis of flexible miniature transistors
prototypes designed for modern electronics.â€
Step-wise
increases in magnification are shown, from a macroscale image of a Drosophila
head to an atomic force microscopy (AFM) image of a single nipple-type
nanostructure coating an ommatidial lens. Credit: Mikhail Kryuchkov, Department
of Cell Physiology and Metabolism, Faculty of Medicine, University of Geneva,
Geneva, Switzerland. Department of Pharmacology and Toxicology, University of
Lausanne, Lausanne, Switzerland
Scientists
managed to rebuild the corneal coating of small fruit flies via direct and
reverse bioengineering methods. First, they took the protective layer apart
into its constituent components, which turned out to be retinin (protein) and
corneal wax (lipids) and then reassemble it under room temperature conditions,
covering glass and plastic surfaces.
According
to Vladimir Katanaev, any other types of materials can be nanocoated too.
Combinations with different types of wax and genetic manipulations of the
retinin protein allow the design of highly diverse and complex functional
nanocoatings.
The
scientist explains that the mechanism underlying the formation of the
protective nanostructures on the corneas of Drosophila flies is a
self-organizing process, described by Alan Turing back in 1952 as a
reaction-diffusion mechanism. That is consistent with the mathematical modeling
performed during the research. This mechanism is also responsible for the
patterns forming, for example, on the fur of a zebra or a leopard. The
nanostructures that protect the corneas of Drosophila eyes are the first
established example of Turing patterns at the nanoscale.
In the
course of the research project, scientists made a detailed characterization of
the properties of retinin, as this protein has been little studied so far. It
turned out that this initially unstructured protein forms a globular structure
when interacting with corneal waxes. Thus, scientists took a look deep into the
biophysical nature of the self-organization abiding to the Turing model,
highlighting an important molecular process likely at the core of the
self-organization – the initiation of the protein structuring.
At next
stages, the research team aims at developing a model of three-dimensional
nanostructuring (with nano-funnels, nanocolumns, nanorolls within the layer of
the coating), also based on the Turing mechanism. This work would lie at the
very frontier of modern scientific knowledge and can have promising fundamental
and technological consequences.
Professor
Vladimir Katanaev started studying the structure of the eye of Drosophila fly
about 10 years ago. According to the scientist, the first data were obtained
almost impromptu by means of atomic force microscopy. During collaboration with
the laboratory of Prof. Igor Serdyuk from the Institute of Protein Research (Russian
Academy of Sciences), it was discovered that the surface of the corneas of the
flies was not smooth but was covered with beautiful patterns of pseudo-ordered
nanoscale outgrowths. As it turned out, nanocoatings of this kind were
described back in the late 1960s on the surface of the eyes of moths, larger
insects to whom these structures also provide an anti-reflex function, reducing
the reflection of incident light to zero and allowing to optimize light
perception in the darkness.