Ultrasound for         Particle size       Entrapment efficiency         Drug loading
first time（s）           (nm)                        (%)                                 (%)

10                              198.2                       44.3                              4.24
30                                99.9                       47.3                              4.51
60                              139.1                       49.3                              4.70
120                            105.7                       46.8                              4.47