  We report on the construction and the dynamics of monodisperse star-shaped
particles, mimicking, at the mesoscale, star polymers. Such multi-arm star-like
particles result from the self-assembly of gold nanoparticles, forming the
core, with tip-linked filamentous viruses - M13 bacteriophages - acting as
spines in a sea urchin-like structure. By combining fluorescence and dark-field
microscopy with dynamic light scattering, we investigate the diffusion of these
hybrid spiny particles. We reveal the internal dynamics of the star particles
by probing their central metallic core, which exhibits a hindered motion that
can be described as a Brownian particle trapped in a harmonic potential. We
therefore show that the filamentous viruses and specifically their tip proteins
behave as entropic springs, extending the relevance of the study of such hybrid
mesoscopic analogs of star polymers to phage biotechnology.
