Recent prototypes have shown that artificial cilia, when allowed to self-organize, spontaneously begins behaving like biological cilia.
tiny hair-like structures that perform feats such as clearing
microscopic debris from the lungs and determining the correct location
of organs during development, move in mysterious ways. Their beating
motions are synchronized to produce metachronal waves, similar in
appearance to “the wave” created in large arenas when audience members
use their hands to produce a pattern of movement around the entire
to the importance of ciliary functions for health, there is great
interest in understanding the mechanism that controls the cilias’
beating patterns. But learning exactly how cilia movement is coordinated
has been challenging.
may be beginning to change as a result of the creation, by a team of
Brandeis researchers, of artificial cilia-like structures that
dramatically offers a new approach for cilia study.
a recent paper published in the journal Science, Associate Professor of
Physics Zvonimir Dogic and colleagues present the first example of a
simple microscopic system that self-organizes to produce cilia-like
shown that there is a new approach toward studying the beating,” says
Dogic. “Instead of deconstructing the fully functioning structure, we
can start building complexity from the ground up.”
complexity of these structures presents a major challenge as each
cilium contains more than 600 different proteins. For this reason, most
previous studies of cilia have employed a top-down approach, attempting
to study the beating mechanism by deconstructing the fully functioning
structures through the systematic elimination of individual components.
interdisciplinary team consisted of physics graduate student Timothy
Sanchez and biochemistry graduate student David Welch who worked with
biologist Daniela Nicastro and Dogic. Their experimental system was
comprised of three main components: microtubule filaments — tiny hollow
cylinders found in both animal and plant cells, motor proteins called
kinesin, which consume chemical fuel to move along microtubules and a
bundling agent that induces assembly of filaments into bundles.
and colleagues found that under a particular set of conditions these
very simple components spontaneously organize into active bundles that
beat in a periodic manner.
Artificial cilia exhibit spontaneous beating.
addition to observing the beating of isolated bundles, the researchers
were also able to assemble a dense field of bundles that spontaneously
synchronized their beating patterns into traveling waves.
processes of many kinds have recently become a focus of the physics
community. These processes range in scale from microscopic cellular
functions and swarms of bacteria to macroscopic phenomena such as
flocking of birds and traffic jams. Since controllable experiments with
birds, crowds at football stadiums and traffic are virtually impossible
to conduct, the experiments described by Sanchez and colleagues could
serve as a model for testing a broad range of theoretical predictions.
addition, the reproduction of such an essential biological
functionality in a simple system will be of great interest to the fields
of cellular and evolutionary biology, Dogic says. The findings also
open a door for the development of one of the major goals of
nanotechnology — to design an object that’s capable of swimming
The Dogic lab is currently planning refinements to the system to study these topics in greater depth.
Study abstract: Cilia-Like Beating of Active Microtubule Bundles