US Patent 7141431 - Nanoparticles Coupled to Polymeric Microparticle

http://www.freepatentsonline.com/7141431.pdf

This patent to a company called Luminex seems to claim a very basic use of identifiable (i.e. fluorescently stained) nanoparticles. Priority goes back as faras Aug.17, 1999. Claim 1 reads:

1. A carrier particle, comprising a polymeric microparticle coupled to a nanoparticle of a nanoparticle population, wherein the nanoparticle has a diameter in the range of about 1 and 1,000 nm, and wherein the nanoparticle has a characteristic that is distinguishable from a characteristic of nanoparticles of a different nanoparticle population.