Objective       To prepare luteinising-hormone releasing hormone (LHRH) nanoliposomal microbubbles specifically targeting ovarian cancer cells and characterize their physiochemical properties and in vitro targeting ability.       Methods       Lyophilization/sonication method was used to prepare non-

targeting nano-liposomal microbubble (N-N-Mb). By using the biotin-avidin bridge method

conjugated biotinylated LHRH antibodies to N-N-Mb generated biotinylated LHRH nanoliposomal microbubble (LHRH-N-Mb) targeting specifically ovarian cancer cells. The morphology and shelf life of microbubbles was detected by light microscopy

and the particle size range and the surface potential were measured by zeta detector. The binding affinity of the secondary antibody with LHRH-N-Mb or N-N-Mb was determined by flow cytometry. The binding of LHRH-N-Mb to human OVCAR-3 ovarian cancer cells was detected by light microscopy.       Results      The rounded and uniformly distributed N-N-Mb and LHRH-N-Mb were successfully generated. The particle size was 372±45 nm with a mean of 360 nm for N-N-Mb

and 511±64 nm with a mean of 508 nm for LHRH-N-Mb. There was significant difference in the size between the 2 groups (

P

0.05)

while the surface potential of the 2 microbubbles remained no significant difference (-14.5±0.5 and -14.6±0.8 mV

P

0.05). After being kept at room temperature for 16 d

no significant difference of the LHRH-N-Mb’s physiochemical properties was detected compared with that of freshly prepared microbubbles. The secondary antibody binding rate of LHRH-N-Mb or N-N-Mb was 75.6% or 0.83% respectively

with significant difference (

P

0.05). Moreover

the rosette formation surrounding OVCAR-3 cells was observed under light microscope after cells were incubated with LHRH-N-Mb while pre-incubated biotinylated LHRH antibody blocked the rosette formation.       Conclusion       The LHRH nanoliposomal microbubbles specifically targeting ovarian cancer cells are successfully prepared through biotin-avidin mediation and lyophilization/sonication method. The key feature of LHRH nanoliposomal microbubbles are smaller size

stability and high efficiency of targeting human OVCAR-3 ovarian cancer cells in vitro.