In vivo quantifying molecular specificity of Cy5.5-labeled cyclic 9-mer peptide probe with dynamic fluorescence imaging.

Yunpeng Dai,Jimin Liang,Jipeng Yin,Yajun Liu,Yongzhan Nie,Kaichun Wu,Xianghan Zhang,Yu Huang,Guodong Wang,Xueli Chen

doi:10.1364/boe.7.001149

Abstract

We quantified molecular specificity of Cy5.5-GX1 in vivo with dynamic fluorescence imaging to better understand its kinetic properties. According to whether or not free GX1 was injected and when it was injected, twelve of BGC-823 xenografted mice were randomly divided into three groups and underwent a 60 minute dynamic fluorescence scanning. Combined with a principal-component analysis, the binding potential (Bp) of the probe was determined by both Logan graphical analysis with reference tissue model (GARTM) and Lammertsma simplified reference tissue model (SRTM). The sum of the pharmacokinetic rate constants (SKRC) was quantified by the Gurfinkel exponential model (GEXPM). Cy5.5-GX1 specifically targeted tumor both in vitro and in vivo. We obtained similar quantification results of Bp (GARTM Bp = 0.582 ± 0.2655, SRTM Bp = 0.618 ± 0.2923), and obtained a good linear relation between the Bp value and the SKRC value. Our results indicate that the SKRC value is more suitable for an early-stage kinetic data analysis, and the Bp value depicts kinetic characteristics under the equilibrium state. Dynamic fluorescence imaging in conjunction with various kinetic models are optimal tools to quantify molecular specificity of the Cy5.5-GX1 probe in vivo.

Highlights

GX1 (CGNSNPKSC), a cyclic 9-mer peptide, was identified by Min Zhi et al in 2004 by using in vivo phage display technology [1], which binds to the gastric tumor-derived vascular endothelial cells
The binding potential (Bp) values obtained from simplified reference tissue model (SRTM) were statistically analyzed, and the results revealed that the Bp values of the non-block and 24h-block groups were significantly different from the Bp value of the 1h-block groups (p = 0.01, 0.023, respectively)
Introducing the singular value decomposition (SVD) method improved the accuracy of Bp value estimation, which is an indicator of the available receptor density and tracer specific binding, because the TAC of the tumor after SVD treatment is more consistent with the tracer specific binding component in the tumor region, while the TAC of muscle after SVD treatment is more in line with the non-specific binding component in the muscle region [12]

Summary

Introduction

GX1 (CGNSNPKSC), a cyclic 9-mer peptide, was identified by Min Zhi et al in 2004 by using in vivo phage display technology [1], which binds to the gastric tumor-derived vascular endothelial cells. Further research confirmed that GX1 was capable of effective specific targeting of the tumor vasculature and could be applied to anti-angiogenesis iatreusis of cancer, together with anti-neoplastic agents, as a novel tumor vascular marker [2,3,4,5,6]. Static optical imaging results revealed that Cy5.5-GX1 is highly sensitive, rapidly tumor targeting and has fast muscle tissue clearance, it was an ideal probe for optical imaging in living subjects. The binding potential (Bp) of the probe, which is a receptor density-related parameter obtained by early dynamic imaging data, has not been determined. Further investigation needs to be addressed to facilitate the clinical application of GX1

Methods

Results

Conclusion