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. Author manuscript; available in PMC: 2009 Oct 9.
Published in final edited form as: Small. 2008 Sep;4(9):1307–1312. doi: 10.1002/smll.200701319

Figure 1.

Figure 1

Schematic depiction of removable polymer coatings that veil and unveil bioactive ligands on a nanoparticle surface. A hydrophilic polymer (wavy-gray) linked via MMP cleavable substrates (jagged-yellow) veils the activity of a cell-internalizing domain (jagged-blue) on the surface of a magnetofluorescent nanoparticle. Veiled particles have extended circulation times that enable their passive accumulation in tumors. Extravasated particles are activated by MMP-2 in the micro-environment to unveil internalizing domains, which associate with the cell membrane and shuttle nanoparticles into cells.