Preparation And Pharmacokinetics Study On Lipid Microbubbles Loaded 10-Hydroxycamptotheci

HCPT (10-hydroxycamptothecin) is a kind of the alkaloids or semi-synthetics which is extracted from the camptotheca acuminata, it has broad spectrum of anti-tumor, without cross-resistance with other commonly used anticancer drugs, so it also has the effect on the drug-resistant tumors. A number of studies show that HCPT is the most active drug in the camptothecin family.It not only has the certain effect on the type of ascites liver cancer, head and neck cancer, stomach cancer, non-small cell lung cancer and leukemia ,but also has the potential selective damaging effect on the liver cancer cells. Though HCPT is the more promising anti-cancer drug, it has a number of problems ,such as the low solubility of its own existence, active lactone ring instability,a larger toxicity and adverse reactions. Currently HCPT is used by adding sodium hydroxide to its structure (open lactone ring)in clinic , which has a low activity of anticancer, short half-life (t1/2 approximately 5 min), as a cell cycle specific drug, the short lifetime in vivo and a low-concentration in organizations become the main limiting factors for improving its therapeutic effect, so it is particularly important to look for a new effective drug delivery system to make up for the deficiencies of the drug itself.Lipid ultrasound microbubble not only has these advantages such as increasing drug solubility like liposome, protect the drug activity structure, extend the residence time in plasma and reduce the toxicity, but also has the effect of targeted delivery. Ultrasound-mediated cavitation can deliver gene or drug targetly, so as to achieve the purpose of treating diseases. Therefore, in order to solve the technology of pharmacokinetics problems of HCPT, including the bad stability, the short half-life and poor water-soluble, the study aims to prepare a new lipid ultrasound microbubble loaded HCPT(HLM) and check its physical properties, and explore its pharmacokinetics in mice, which could provide reliable experimental basis for a new long-term and targeted formulations of HCPT.The study included the following two parts:PARTⅠ:STUDY ON PREPARATION AND CHARACTERISTICS OF LIPID ULTRASOUND MICROBUBBLES CONTAINTING 10-HYDROXYCAMPTOTHECINObjective To screen the optimal formulation and preparation of the containting 10-hydroxycamptothecin (HCPT) lipid ultrasound microbubble and to study its characteristics and to evaluate it as a new Ultrasound contrast agent for chemotherapeutic drug delivery.Methods The lipid ultrasound microbubble containting HCPT was prepared by mechanical vibration and orthogonal design was used to select the optimal formulation.Ultraviolet spectrophotometry and reversed phase high-performance liquid chromatography (RP-HPLC) were used to determine the entrapment efficiency and the drug-loading amounts of the HCPT lipid microbubble. The optimal one was studied for appearance, mean diameter, entrapment efficiency before and after irradiance of 60CoγRay . The liver imaging was observed.Results The concentration of the optimal formulation was (3.07±0.58)×109 / ml,the mean diameter range of the self-made lipid microbubbles containting HCPT was (1.10±0.20)μm, the mean diameter was 1.10μm, zeta potential was ?(3.90±0.80)mV, the drug entrapment efficiency was 86.70%, the drug-loading amounts was 21.70%.After sterilization with irradiance of 60Coγ, the mean diameter and entrapment efficiency did not change obviously. The liver imaging of the rabbit could be enhanced obviously and persistently.Conclusion The self-made lipid microbubbles containting HCPT had higher entrapment efficiency and drug-loading amounts,and was effective for the enhancement of ultrasound imaging in vivo.Based on this phenomenon,the future studies for ultrasound-mediated drug delivery would be expected. PARTⅡ: STUDY ON PHARMACOKINETICS OF LIPID MICROBUBBLES LOADED 10-HYDROXYCAMPTOTHECINObjective To prepare the lipid ultrasound microbubble loading HCPT(HLM) and check its appearance, mean diameter range, zata potential.To explore the pharmacokinetics in plasma and the HCPT concentrations in liver after HLM was destructed by ultrasound.Methods The HLM was prepared by mechanical vibration,the light microscope was used to evaluate its appearance, the Malvern laser particle size measuring instrument was used to evaluate its mean diameter range and the zata potential.In pharmacokinetics study,HCPT concentrations in plasma of the mice at different time points were processed by 3P97 program.After the mice were divided into 4 groups (HLM, HLM with ultrasound, HCPT injection, HCPT injection with ultrasound),the HCPT injection and HLM were intravenous injection into the mice respectively and destructed by ultrasound from its body surface,then the concentrations of HCPT in liver were determined by HPLC- fluorometric method.Results The light microscope imaging showed that the HLM exhibited a spherical shape, the mean diameter range of which was (1.1±0.2)μm.The mean diameter was 1.1μm.Zeta potential was ?(3.9±0.8)Mv. The concentration-time curve of HLM and HCPT injection were in accordance with a two compartment model.HCPT plasma concentrations of HLM were higher than those of HCPT injection at almost all sampling time.It also showed longer elimination period (6.70 h) than the HCPT injection (1.12 h).Its circulation period was prolonged and bioavailability of HCPT was increased.Its AUC was 5.5 times of that of HCPT injection. After HLM and HCPT injection were destructed by ultrasound from body surface of mice,the concentrations of HCPT in liver in the HLM group were the highest among the other groups.Conclusions The HLM can prolong circulation period in mice,and promote to release drug obviously in target tissue after destructed by a certain ultrasound energy from body surface.