Spectroscopically well-characterized RGD optical probe as a prerequisite for lifetime-gated tumor imaging.
Labeling of RGD peptides with near-infrared fluorophores yields optical probes for noninvasive imaging of tumors overexpressing ανβ3 integrins. An important prerequisite for optimum detection sensitivity in vivo is strongly absorbing and highly emissive probes with a known fluorescence lifetime. The RGD-Cy5.5 optical probe was derived by coupling Cy5.5 to a cyclic arginine-glycine-aspartic acid-d-phenylalanine-lysine (RGDfK) peptide via an aminohexanoic acid spacer. Spectroscopic properties of the probe were studied in different matrices in comparison to Cy5.5. For in vivo imaging, human glioblastoma cells were subcutaneously implanted into nude mice, and in vivo fluorescence intensity and lifetime were measured. The fluorescence quantum yield and lifetime of Cy5.5 were found to be barely affected on RGD conjugation but dramatically changed in the presence of proteins. By time domain fluorescence imaging, we demonstrated specific binding of RGD-Cy5.5 to glioblastoma xenografts in nude mice. Discrimination of unspecific fluorescence by lifetime-gated analysis further enhanced the detection sensitivity of RGD-Cy5.5-derived signals. We characterized RGD-Cy5.5 as a strongly emissive and stable probe adequate for selective targeting of ανβ3 integrins. The specificity and thus the overall detection sensitivity in vivo were optimized with lifetime gating, based on the previous determination of the probes fluorescence lifetime under application-relevant conditions.
Department of Molecular Biology of Neuronal Signals, Max-Planck-Institute for Experimental Medicine, Göttingen, Germany.
Julia Eva
JE
Mathejczyk
Jutta
J
Pauli
Christian
C
Dullin
Joanna
J
Napp
Lutz-F
LF
Tietze
Horst
H
Kessler
Ute
U
Resch-Genger
Frauke
F
Alves
D000818:Animals; D002232:Carbocyanines / Q000737:chemistry; D045744:Cell Line, Tumor; D005456:Fluorescent Dyes / Q000737:chemistry; D005909:Glioblastoma / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D039302:Integrin alphaVbeta3 / Q000378:metabolism; D008297:Male; D051379:Mice; D008819:Mice, Nude; D057054:Molecular Imaging / Q000379:methods*; D015335:Molecular Probes / Q000737:chemistry* / Q000378:metabolism; D009368:Neoplasm Transplantation; D009842:Oligopeptides / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D019265:Spectroscopy, Near-Infrared / Q000379:methods*; D014183:Transplantation, Heterologous
C098793:CY5.5 cyanine dye; D002232:Carbocyanines; D005456:Fluorescent Dyes; D039302:Integrin alphaVbeta3; D015335:Molecular Probes; D009842:Oligopeptides; C047981:arginyl-glycyl-aspartic acid