Objective　　　 To prepare DiO-labeled microbubbles

and to investigate their physicochemical property

fluorescent labeling conditions and the enhance effects for liver contrast imaging.　　　 Methods　　　 The DiO-labeled microbubbles were prepared with a freeze-dried powder and mixed Dimethyl sulfoxide (DMSO) dissolved DiO. Then we replaced the air in the bottles with perfluoropropane. Finally the DiO-labeled microbubbles were made by high speed mechanical agitation. The physicochemical property and fluorescent labeling conditions of DiO-labled microbubbles were investigated.

Six healthy male New Zealand white rabbits which weighted between 2.0 and 2.5 kg were injected through auricular vein with the DiO-labeled microbubbles. Then we dynamically observed the microbubbles enhanced ultrasound images of the rabbit liver parenchyma. Fluorescence microscopy was used to observe the deposition of green fluorescein in a small portion of frozen section liver tissues.　　　 Results　　　 DiO-labeled microbubbles were round in shape and uniform in size

with a concentration of (4-7)×10

9

/mL and a size of 429±119 nm. The outer shell of DiO-labeled microbubbles was green under confocal laser scanning microscope. Liver imaging using DiO-labeled microbubbles showed significant and persistent enhancement. Little fluorescein was distributed in the liver under fluorescence microscope.　　　 Conclusion　　　 DiO-labeled microbubbles are uniform in size and can access the pulmonary circulation. They significantly enhance the liver images in contrast enhanced ultrasound.