Abstract: In this paper, water in oil in water(W₁/O/W₂) double emulsion/solvent evaporation process was used to prepare poly(L-lactic acid)(PLLA) microbubbles. With the characterization technique of SEM, CLSM and PSA, we investigated how the experimental parameters would influence the properties of microbubbles. The results demonstrate that poly(vinyl alcohol)(PVA) was an excellent emulsifier in the outer aqueous phase for this system. By changing the concentration of PVA aqueous solution or the speed of homogenizer during the second emulsification, the average size of microbubbles can be controlled between 1 μm to 10 μm. The ratio of water to oil at the first emulsification will affect the hollow ratio of microbubbles to a great extent. It was confirmed that gas-filled PLLA microbubbles has an excellent ultrasound contrast ability.

Key words: Microbubbles, Double emulsion, Poly(L-lactic acid), Ultrasound contrast