Synthesis And In Vitro Evaluation Of Tumor-Targeted Heparin-Campotothecin Conjugates

Camptothecin(CPT) is a alkaloid isolated from the Camptotheca acuminata, and has shown a broad range of anticancer activity in animal models. However, clinical use of CPT has been severely restricted by its water-insolubility and toxicity stemming in part from the instability of E-lactone ring at physiological pH. In order to overcome these problems, a folate-targeted polysaccharide heparin-based conjugates of CPT was synthesized. This thesis is composed of the following parts:1. Preparation of folate-heparin conjugate and its cell recognition studies. Folate-heparin conjugate was synthesized by connecting folate with heparin through an ethylenediamine (EDA) linker. The fluorescence labelled folate-heparin conjugate could selectively recognize CNE2 cells (folate receptor overexpressed cell lines) from A549 cells (no detectable folate receptor cell lines), indicating that folate remained high activity after conjugation with heparin. The folate-heparin conjugate could be hopefully used as an anticancer drug carrier for site-directed therapy.2. Synthesis and in vitro evaluation of water-soluble heparin-campotothecin conjugate. In this chapter, campotothecin was covalently connected with heparin through a glycine linker to get a water-soluble heparin-campotothecin conjugate (Hep-CPT). The Hep-CPT was characterized by FT-IR and High-performance liquid chromatography (HPLC). The drug loading of the Hep-CPT conjugate was 7.2%. The Hep-CPT was stable in pH 7.4 phosphate buffered saline under 37℃. The amount of CPT released from the conjugate was less than 15% in 24 h. The release of CPT decreased remarkably in low pH. In vitro experiment indicated that the cytotoxicity of CPT in the form of Hep-CPT decreased more than 50% over free CPT. The Hep-CPT was hopefully accumulated in tumor tissue as a macromolecular prodrug through enhanced permeability and retention(EPR) effect, resulting lower toxic side effects and improved therapeutic efficacy.3. Synthesis and in vitro evaluation of folate-heparin-campotothecin conjugate. In this chapter, the folate-EDA was covalently connected with heparin- campotothecin by carbodiimide activation to get a folate-heparin-campotothecin conjugate (FA-Hep-CPT). The drug loading of the FA-Hep-CPT was 3.2%. During 24 hours, the amount of CPT released from the conjugate was 21.3% in pH 7.4 PBS under 37℃. The release rate of CPT decreased dramaticly in low pH. In vitro experiment indicated that the cytotoxicity of CPT in the form of FA-Hep-CPT increased remarkably in comparison with free CPT and Hep-CPT conjugate.