Preparation And In Vitro And In Vivo Study Of Hydroxycamptothecin Nanocrystals

10-Hydroxycamptothecin (10-HCPT) is a promising anticancer drug with a wide spectrum of antitumor activities. Since the lactone form of 10-HCPT is poorly soluble in water, the carboxylate form-based injections is used in clinic.But the activity of the carboxylate form is reduced in contrast to the lactone form and susceptible to hydrolysis which leads to a short half-life of only 11 min, limiting its clinical application. In order to develop a simple, safe and highly effective drug delivery system, a modified acid-base microprecipitation combined with a high-pressure homogenization technique was adopted to prepare 10-HCPT nanocrystals. And the in vitro characterizations of 10-HCPT nanocrystals was performed, and their antiproliferative activity and cellular uptake characteristics was also investigated.1. The particle size, drug loading content and storage stability were used as the main index to evaluate the preparation method, stabilizers, and technological parameters of 10-hydroxycamptothecin nanocrystals in single factor screening. The reproducibility of preparation process and the properties of the resultant nanocrystals were investigated after scale-up. As a result, the microprecipitation through alkali-solubilization followed bycontrolled acidification combined with high pressure homogenization proved to be efficient way to prepare 10-HCPT nanocrystal with no need of organic solvents or stabilizers. PI88 could be used as a good cryoprotectant for the lypholization of 10-HCPT nanocrystals. When the preparation was scaled up to 1000.0 mg 10-hydroxycamptothecin, the resultant particle size of 10-hydroxycamptothecin nanocrystals was (141.0±0.4) nm, the polydispersity index was 0.14±0.02, and the zeta potential was (-26.0±1.1).2. The in vitro characterization of 10-HCPT nanocrystals displayed that the nanocrystals were spherical with the encapsulated 10-HCPT still in the original crystalline. The in vitro drug release behaviour fitted well in Higuchi equation. In MTT assay,10-HCPT nanocrystals showed higher cell proliferation inhibitory activity compared to the commercially availabe 10-HCPT injections against 4T1, MCF-7, HepG2, A549 and Hela cells. The cellular uptake of 10-HCPT nanocrystals by 4T1 cells was significantly higher than that of 10-HCPT injections. The enhanced uptake was mainly due to the clathrin-mediated endocytosis.3. The subsequent in vivo investigation demonstrated that 10-HCPT nanocrystals significantly increased the plasma half-life of HCPT (p<0.01) and AUC0-24h (p<0.01) in comparision with 10-HCPT injections; 10-HCPT nanocrystals also greatly increased drug accumulation in tumor by 6.25 fold when i.v. administrated at the same dose of 5mg/kg, 10-HCPT nanocrystals greatly enhanced the tumor inhibition rate than 10-HCPT injections (74.84% vs 37.93%, p<0.001).