Stromal cell-derived factor-1-targeted ultrasound contrast agent tightly binds to vascular endothelial cells

ABSTRACT

BACKGROUND:

Stromal cel-derived factor-1 (SDF-1) is one of the most powerful chemokines in myocardial infarction region and plays a particularly pivotal role in the homing of stem cels to an injured myocardium and promoting angiogenesis. On the other hand the microbubble and acoustics active substances carrying targetable ligands can be prepared into targeted ultrasound contrast agents that can be combined with living cels used for molecular imaging. The key of ultrasonic molecular imaging is to find imaging targets, and to successfuly prepare targeted ultrasound contrast agent which can be combined with the imaging target specificaly and efficiently.

To prepare and evaluate targeted microbubble contrast agents with SDF-1 monoclonal antibody.

Targeted microbubble contrast agent with SDF-1 monoclonal antibody was prepared using the biotin-streptavidin method. The physiochemical properties of targeted microbubble contrast agent were evaluated by appearance, pH, particle diameter, optical and fluorescence microscope and flow cytometry test. Four minipigs underwent ligation of the left anterior descending coronary artery to complete the establishment of acute myocardial infarction model, and another two minipigs were subject to thoracotomy but no ligation of the coronary artery. Then, al animals were injected with microbubble contrast agents. The stability of microbubbles was assessed by immunofluorescence testin vivo. RESULTS AND

SDF-1 and microbubbles were combined by biotin-streptavidin method.In vitro appearance of the contrast agent was translucent yelow or green, and stratified after standing. pH vaule was 7.02±0.12 for non-targeted contrast agent and 6.10±0.19 for targeted microbubble contrast agent. Under the fluorescence microscope, the distribution and size of targeted microbubbles were uniform, and the microbubbles were surrounded by bright and ring shaped green fluorescence that had no changes after highly shaking. The diameter of microbubbles was (2 422.62±238.82) nm after carrying the SDF-1 antibody. Flow cytometry results showed that the carrying rate of targeted contrast agents was stable in different periods.In vivo test showed that targeted microbubbles gathered in vascular endothelial cel surface after acute myocardial infarction. These findings indicate that the targeted microbubble contrast agent carrying SDF-1 monoclonal antibody prepared by biotin-streptavidin method can be combined with vascular endothelial cels, and the binding rate is high and stablein vitro.