  The rapid worldwide spread of severe viral infections, often involving novel
modifications of viruses, poses major challenges to our health care systems.
This means that tools that can efficiently and specifically diagnose viruses
are much needed. To be relevant for a broad application in local health care
centers, such tools should be relatively cheap and easy to use. Here we discuss
the biophysical potential for the macroscopic detection of viruses based on the
induction of a mechanical stress in a bundle of pre-stretched DNA molecules
upon binding of viruses to the DNA. We show that the affinity of the DNA to the
charged virus surface induces a local melting of the double-helix into two
single-stranded DNA. This process effects a mechanical stress along the DNA
chains leading to an overall contraction of the DNA. Our results suggest that
when such DNA bundles are incorporated in a supporting matrix such as a
responsive hydrogel, the presence of viruses may indeed lead to a significant,
macroscopic mechanical deformation of the matrix. We discuss the biophysical
basis for this effect and characterize the physical properties of the
associated DNA melting transition. In particular, we reveal several scaling
relations between the relevant physical parameters of the system. We promote
this DNA-based assay for efficient and specific virus screening.
