Synthesis And Characterization Of Hyaluronic Acid-camptothecin Conjugates And Folic Acid-Hyaluronic Acid-Camptothecin Conjugates

Camptothecin (CPT) is an alkaloid which originally isolated from the Chinese tree Camptotheca acuminate. CPT has good curative effect on the treatment of liver cancer, bladder cancer, leukemia and other malignant tumors. However, its clinical use is restricted by its water-insolubility, cell toxicity and forming inactivation open-loop easily. In order to overcome these problems, hyaluronic acid and folic acid which have good water-solublity and biocompatiblity was connected to CPT to obtain a conjugate. The performances of these conjugates on tumor cells as target drugs were investigated. The work was summarized as following:1. 3,3′-dithiodipropionic acid was synthesized from 3-thiopropionic acid. Then camptothecin-20-O-3,3′-dithiodipropanoate was synthesized with camptothecin and 3,3′-dithiodipropionic acid as start materials through esterification. A hyaluronic acid-dipodihydrazide-camptothecin conjugate in nano-meter size was prepared by amidation of hyaluronic acid and camptothecin-20-O-3,3′-dithiodipropanoate with dipodihydrazide. Fluorescein isothiocyanate was used as a fluorescence reagent to label the conjugate. The obtained conjugate was characterized by FT-IR,1H-NMR and TEM. The drug loading for the conjugate, which was characterized by high-performance-liquid chromatography (HPLC), was 34.7%. The drug release of the conjugat was 28.5% in pH 7.4 phosphate buffer solution under 37℃after 72 hour. This value is 2.9% in pH 5.0 phosphate buffer solution. As a target drug, the congjugate could selectively recognize HepG2 cell and HeLa cell. The in vitro cytotoxicity is significantly increased than camptothecin for HepG2 cell and HeLa cell. 2. Ethylenediamine was used as a link reagent to connect folic acid to hyaluronic acid- camptothecin-20-O-3,3′-dithiodipropanoate-dipodihydrazide conjugate throughγ-carboxyl group of folic acid. The conjugate was characterized by UV/Vis spectroscopy and H1-NMR. The drug loading, which was evaluated by high-performance-liquid chromatography, was 25.6%. The drug release of the conjugat was 31.2% in pH 7.4 phosphate buffer solution under 37℃after 72 hour. This value is 4.3% in pH 5.0 phosphate buffer solution. The in vitro cytotoxicity is significantly increased than hyaluronic acid-dipodihydrazide-camptothecin conjugate for HepG2 cell and HeLa cell.