Silica nanoparticles, produced by the sol–gel
process that uses silicon alkoxides as starting materials,
have received much attention for many years because
of their practical importance in a variety of fields.
In recent years, the newly emerging area of in vitro
andin vivo diagnosis, analysis, and measurements inside
intact biologic systems (e.g., tissues, blood, and single
cells), with the use of nanoparticle devices, has at-
tracted considerable attention.