Evolution of nanoparticle-induced distortion on viral polyhedra.

Morphological changes in the polyhedra of the Bombyx mori L. nuclear polyhedrosis virus (BmNPV), a baculovirus causing the deadly grasserie disease in silkworms, brought about by mixing with lipophilically capped amorphous silica nanoparticles (LASN, average size 10 ± 2 nm) were studied with scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. SEM shows that the regular octagonal polyhedra facets are replaced by a larger number of newly formed irregular ones. The average number of facets reveals a nonlinear growth pattern with nanoparticle (NP) concentration, where an initial linear region ends in a plateau. IR bands corresponding to vibration modes of the capping show (a) a saturation of the area under the band with NP concentration, indicating a correlation with attachment to viral polyhedra and (b) a narrowing of the band per NP from the linear to the plateau portions of the distortion curve, suggesting non-equilibrium and equilibrium situations, respectively.