Viruses are often associated with disease, but they can also be useful. Viruses infect many organisms other than humans, including plants and bacteria. Aside from being infectious, the actual structure of a virus can be harnessed as a material. For example, a virus cage can be used to deliver drugs to our cells or to protect catalytic cargo. This is possible because of the amazing structural properties that viruses exhibit.
The two basic components of a standard virus are 1) the genetic information that codes for the creation of more viruses (either DNA or RNA) and 2) the protective protein cage that surrounds that genetic information. For materials scientists, it is this protective cage that is a source of bio-inspiration. The cage is composed of various proteins that self-assemble into three-dimensional shapes (usually sphere-like) around the DNA or RNA in the same way carefully designed magnetic puzzle pieces ‘click’ into place when shaken (pictured right).
One important point about using virus cages as vaccines or drug delivery carriers is that if the genetic information is removed from the protein cage, then that virus is no longer infectious. The same way a building cannot be constructed without blueprints, viral progeny cannot be created without the genetic information that encodes for its make-up.
With this in mind, scientists at Indiana University have begun to construct Virus-Like Particles (VLPs), which are solely composed of the protein cage. The Douglas Lab studies P22, a semi-porous 60-nanometer (1 nanometer is roughly one millionth the thickness of your fingernail) VLP, which self-assembles from many copies of two types of protein (left). The production of these two proteins in a host organism results in the formation of a uniform population of VLPs-instant nano-containers!
But what’s so exciting about a nano-container? Alone-maybe nothing, until you put something in it. The Douglas Lab and others have trapped enzymes that produce useful chemicals inside of VLPs. In the P22 system, this encapsulation is accomplished by fusing the enzyme to one of the VLP proteins so that the cargo becomes encapsulated during the assembly process. Once encapsulated, enzymes remain active but are protected from the potentially harmful exterior environment. By preserving the structure of the enzymes and subsequently their catalytic function, they remain active under harsher conditions for a longer period of time. This is of special interest to chemical companies who are interested in the production of certain chemicals. For example, by protecting an enzyme that produces isopropanol (rubbing alcohol) from being degraded, large amounts of the chemical can be produced without creating new enzymes, thus lowering production costs.
Scientists are exploring many ways to harness the design principles of nature. From self-cleaning paint, inspired by the self-cleaning properties of the lotus leaf, to strong but removable adhesives, inspired by the gecko foot, the instances of bio-inspiration and biomimicry are leading to the creation of many novel materials. Viruses, in particular are proving to be an effective blueprint for designing a plethora of new nanomaterials. Perhaps someday, viruses will be known not only for causing diseases but also for preventing them.