Objective   To investigate the effects of different technical conditions on the microvesicle size

envelopment rate

morphology of surface and so on in order to select the best technical conditions to prepare HCPT(10-hydroxy-camptothecin)-loaded PLGA microvesicles.    Methods   Microvesicles were prepared by a water/oil/water emulsion and solvent evaporation method. Various factors related to the envelopment rate and micmparticle size were studied

such as the ratio of water phase and oil phase

ultrasound power

and time

stirring time and so on. Single factor experiments and  orthogonal design testing was carried out to optimize the technology of microvesicles preparation.    Results   The best processing conditions for microvesicles preparation were as following: HCPT 25 mg

PLGA 1.875 g

the ratio of internal and external phases 1∶15

and the PVA concentration 3%. These preparative variables produced global

smooth and glossy microvesicles. Electric charges were probably between －40 to 0 mV

microvesicles sizes ranged from 500 to 1 000 nm

envelopment rate was 79.33%

drug loading to the microvesicles was 0.478 3%

and ultrasonic imaging was clear in vitro.    Conclusion   Our optimize technical conditions can prepare injectable microvesicles by ultrasound.