[Preliminary study of mesothelin-loaded paclitaxel nanoparticles for ultrasound molecular imaging and treatment of ovarian cancer].

<b>Objective:</b> To prepare mesothelin-loaded paclitaxel (PTX) phase change nanoparticles and evaluate their targeting effect and therapeutic effect on ovarian cancer. <b>Methods:</b> PTX-loaded phase-change nanoparticles PTX-NPs were prepared by the thin-film hydration method, and targeted mesothelin-loaded PTX phase-change nanoparticles Ab-PTX-NPs were prepared by attaching anti-mesothelin antibody to the nanoparticles using the biotin-affinity method. Zeta potential and particle size were determined by applying a zeta potential and a particle size analyzer, and the encapsulation rate and the amount of drug loading of PTX was measured by applying a UV spectrophotometer. Flow cytometry was used to detect the connectivity of anti-mesothelin antibody with PTX-NPs. The phase transition of Ab-PTX-NPs was induced by low-power focused ultrasound, and its ultrasonography imaging was observed; laser scanning confocal microscopy and flow cytometry were used to detect the targeting ability of Ab-PTX-NPs on ovarian cancer SKOV3 cells. The targeting and killing ability of Ab-PTX-NPs on ovarian cancer SKOV3 cells was observed by <i>in vitro</i> targeting assay and apoptosis detection assay. The ovarian cancer model of BALB/c nude mice was constructed to observe the distribution of Ab-PTX-NPs <i>in vivo</i> as well as the effects on blood biochemistry and important organs of nude mice. <b>Results:</b> Ab-PTX-NPs were successfully prepared with a zeta potential of -(8.37±2.71) mV, a diameter of (690.46±28.75) nm, an encapsulation rate of (88.2±4.4)% for PTX, a drug loading capacity of (27.3±0.9)%, and a linkage rate of (94.9±2.8)% between anti-mesothelin antibody and PTX-NPs. Low-intensity focused ultrasound could successfully induce phase transition of Ab-PTX-NPs to realize ultrasonography imaging, and 6 W was the optimal excitation power for low-intensity focused ultrasound. Ab-PTX-NPs showed excellent targeting and killing ability to SKOV3 cells, and the apoptosis and necrosis rate of SKOV3 cells in the Ab-PTX-NPs group reached 79.6%. <i>In vivo</i> imaging showed that the fluorescence intensity at the tumor site of nude mice in the Ab-PTX-NPs group was significantly higher than that in the PTX-NPs group. Biosafety assay showed that 15 d after Ab-PTX-NPs administration, the serum aspartate aminotransferase, alanine aminotransferase, creatine kinase, low-density lipoprotein, blood creatinine, and urea nitrogen concentrations of nude mice were (174.163±20.596)U/L, (33.297±2.573)U/L, (1 959.978±72.212)U/L, (22.033±5.030)μmol/L, (0.393±0.058)mmol/L, and (26.405±4.957)mmol/L, which were not significantly different from those of the phosphate buffer solution (PBS) group, the NPs group, and the PTX-NPs group. The organs such as the heart, the liver, the spleen, the lungs and the kidneys remained intact, and what was seen by the naked eye and microscope was similar with those of the PBS group, NPs group and PTX-NPs group. <b>Conclusion:</b> Ab-PTX-NPs were successfully prepared, which had good ovarian cancer targeting ability and killing effect and effectively reduced the toxicity of PTX.