Using a simple, single-step process, engineers and scientists at the University of California at Berkeley recently developed a technique to direct benign, filamentous viruses called M13 phages to serve as structural building blocks for materials with a wide range of properties. By controlling the physical environment alone, the researchers caused the viruses to self-assemble into hierarchically organized thin-film structures, with complexity that ranged from simple ridges, to wavy, chiral strands, to truly sophisticated patterns of overlapping strings of material--results that may also shed light on the self-assembly of biological tissues in nature. Each film presented specific properties for bending light, and several films were capable of guiding the growth of cells into structures with precise physical orientations. Led by University of California at Berkeley bioengineer Seung-Wuk Lee and his student and lead author Woo-Jae Chung, the researchers published their findings in Nature.
"We are very curious how nature can create many diverse structures and functions from single structural building blocks, such as collagens for animals and celluloses for plants," says Lee. "We have thought that periodic changes in cell activity--such as from day to night, or summer to winter--cause cells to secrete different amounts of macromolecules into confined and curved micro-environments, which might play critical roles in the formation of such sophisticated structures. We believe that biological helical nanofiber structures play a critical role in that process, yet for collagen and cellulose, it has proven quite difficult to engineer their chemical and physical properties to study their assembly process. Therefore, we have been looking for new, helical engineering materials."
The fundamental unit of the novel films is the bacteria-hunting virus, M13. In nature, the virus attacks Escherichia coli (E.coli), but in bioengineering laboratories, the virus is emerging as a nanoscale tool that can assemble in complex ways due to its long, slender shape and its chiral twist.
"Fortunately," adds Lee, "M13 also possesses an elegant helical surface that makes it a best fit for this study."
"We strongly believe that our novel approach to constructing biomimetic 'self-templated', supramolecular structures closely mimics natural helical fiber assembly," says Lee. "One important reason is that we not only mimicked the biological structures, but we also discovered structures that have not been seen in nature or the laboratory, like the self-assembled 'ramen-noodle structures' with six distinct order-parameters."
This story is reprinted from material from NSF, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original article.