Objective       To determine the biodistribution and imaging of VEGF

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-derived peptides (QKRKRKKSRKKH

RKRKRKKSRYIVLS) with

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Re-labeling in A549 tumor bearing nude mice.       Methods      Ethylene dicysteine (EC) was used as the bifunctional chelating agent

and the labeling rates were measured by paper chromatography

and stabilities of the

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Re-peptides were tested in saline and human serum.  Biodistribution was studied by injecting labeled peptides through caudal vein of A549 tumor bearing nude mic

e

and the target/non-target radioactivity ratio (T/NT ratio) was measured and calculated. Single photon emission computed tomography (SPECT) was used for the planar imaging of tumor.        Results       Under the best labeling condition

the 2

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Re-EC-peptides showed high labeling efficiency of (85.34±2.05)% and (90.9±3.45)% respectively

and good stabilities in saline and human serum. Adding rhenium ammonium acid after the reaction significantly increased the stabilities of the labeled peptides. Biodistribution and SPECT planar imaging showed that high radioactivity concentration was accumulated in the A549 tumor site of the mice. Their T/NT ratios were 5.87±1.30 and 5.46±0.87 respective at 6 h

which were significantly higher than that of VEGF

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(1.75±0.72).        Conclusion     

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Re-EC-peptides show high labeling efficiency and high accumulation in A549 tumor tissue

and may be used as tumor-targeting imaging probes and therapy drugs.