Artificial virus shells to be used as containers for nano-manufacturing
29 January 2008
Researchers at the Technion-Israel Institute of
Technology and The Scripps Research Institute in California are designing an
artificial viral shell that could be used as a nano-container for
molecular-scale engineering such as pinpoint drug delivery vehicle, assembly
of molecular computing components, and a host of other applications.
Technion chemist Ehud Keinan and colleagues were inspired by the
construction of natural viral capsids, which enclose a virus’s genetic
material within a sphere made from identical protein building blocks.
Viral capsids assemble themselves with little prompting, making the capsid
an excellent model for artificial nano-capsules, the researchers reported in
the Proceedings of the National Academy of Sciences in December.
said the size of artificial capsids “is very important. It will determine
which molecules we’ll be able to pack inside the container. Small containers
will allow for drug delivery, big ones for delivering proteins and very big
for the delivery of genes.”
The researchers studied how their identical
parts of viral capsids come together. They built a handful of pentagonal
tiles with magnetic edges that mimic the chemically-bonding edges of natural
capsid proteins. In some of their first experiments, they simply shook the
magnetic tiles together in a plastic jar and watched the pieces snap
together to form a sphere.
“Although intellectually we knew that this type
of self-organization occurs spontaneously, watching it happen from random
shaking on the macroscopic scale was inspirational,” Keinan and colleagues
write in their paper.
The researchers then turned to computer simulations of capsid construction,
working with the dish-shaped chemical compound called corannulene. Also
called the buckybowl, corannulene has a five-sided symmetry and rigid curve
that makes it a potentially good building block for an artificial capsid.
In the simulations, Keinan and colleagues experimented with different
chemical “sticky edges” to the corannulene building blocks to determine the
conditions under which the corannulene units would self-assemble into a
ball. They created a half-sphere in the simulation, and expect to have a
full sphere soon.
By applying different kinds of chemical bonds at the
sticky edges — from weak hydrogen bonds to metal bonds to strong disulfide
bonds — the researchers believe they can alter the strength of the capsid
and affect the conditions under which it assembles or disassembles, Keinan
Although the researchers have yet to build an artificial capsid in
the lab, “the present study gives us confidence that we can design molecules
based on these principles that can assemble into chemical capsids,” they