Preparation of bone marrow stromal cell antigen 2 targeted microbubbles and ultrasound molecular imaging for tumor vascular endothelial cells

Abstract

Objective To prepare the bone marrow stromal cell antigen 2 ( BST2)-targeted microbubbls (BST2-TMBs) for detecting the vascular endothelial cells of tumor via ultrasound molecular imaging technology.Methods The targeted microbubbles (BST2-TMBs) were obtained through linking anti-BST2 antibodies to the surface of microbubbles via biotin-avidin bridge.The morphology of TMBs was examined under microscope and size distribution was observed using an optical particle counter.The specific binding of TMBs to endothelial cells was detected by in vitro cell adhesion assay.Murine prostatic carcinoma was used to investigate the capability of TMBs in detecting the vascular endothelial cells and for validating the expression of BST2 proteins.The t test was used by SPSS 19.0 to analyze the data.Results The targeted microbubbles had the mean diameter of 1.61 μm,with 95％ microbubbles between 1 to 5 μm.The in vitro cell adhesion assay demonstrated that the TMBs were able to specifically bind to the surface of endothelial cells,with ( 165 ±25) TMBs per field of view,significantly higher than that of the non-targeted microbubbles ( ( 10 ± 3 ) microbubbles per field of view,t =10.662,P ＜ 0.01 ).The enhancement of ultrasonic signals of these cells bound with TMBs was also observed (TMBs:27.93 ± 5.14 (gray-level),non-targeted microbubbles:3.61 ± 1.67 (gray-level) ; t =7.239,P ＜ 0.01 ).Significant enhancement of signal intensity (gray-level:38.79 ±0.29 at 7 min,remaining 47.65％ of that (81.40 ±0.37) at 30 s) was found in the tumors of mice injected with BST2-TMBs,which was 4.27-fold higher than that (gray-level:9.46 ±0.17 at 7 min,remaining 11.39％ of that (83.01 ± 0.60) at 30 s) of mice injected with non-targeted microbubbles ( t =65.587,P ＜0.01 ).This finding was further confirmed through immunohistochemistry assay.Conclusion BST2TMBs can be used for detecting the vascular endothelial cells of tumors via ultrasound molecular imaging. Key words: Targeted microbubbles; Bone marrow stromal cell antigen 2; Neovascularization; Ultrasonography ; Mice