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. Author manuscript; available in PMC: 2012 May 1.
Published in final edited form as: Expert Opin Med Diagn. 2011 May 1;5(3):241–251. doi: 10.1517/17530059.2011.566858

Fig. 2.

Fig. 2

Schematic shows design of the MMP-2-sensitive fluorescent probe for in vivo NIRF imaging. Fluorophores with excitation and emission wavelengths in the NIR spectrum were covalently coupled to a poly-l-lysine backbone (—Lys-Lys-Lys…—) sterically protected by methoxy polyethylene glycol (MPEG) side chains by means of a synthetic MMP-2 peptide substrate. Top: Owing to the proximity of the fluorophores, fluorescence resonance energy transfer occurs so that almost no fluorescent signal can be detected in the nonactivated state. Bottom: After MMP-2 cleavage of the peptide spacer, fluorophores are released from the carrier and become brightly fluorescent. Figure is reproduced and modified with permission from Radiology [53]. “Copyright (2001) The Radiological Society of North America (RSNA)”.