Study On Self-Assembling Hyaluronic Acid-Paclitaxel Drug Delivery System

Anti-cancer drug paclitaxel is a cytotoxic drug. In order to reduce its toxic side effects and increase drug targeting, we designed a novel drug delivery system, in which hyaluronic acid (HA) was used as carrier conjugating with paclitaxel. HA with a specific targeting property could increase the bioavailability of paclitaxel and control the release rate of the drug. It was demonstrated that drug delivery system with nanosize had a negative targeting effect. We synthesized amphiphilic HA-Amino acid-Paclitaxel conjugates as a type of novel prodrug, which can self-assemble to form nanoparticles in aqueous solution. The major findings are as follows:1. We synthesized hyaluronic acid (HA) as a carrier to conjugate with paclitaxel by inserting different amino acids as spacers, including valine, leucine, and phenylalanine, respectively. The structure of HA-amino acid-paclitaxel conjugates was characterized by nuclear magnetic resonance (NMR) and infrared spectroscopy (FT-IR). Gel permeation chromatography (GPC) was used to determine the molecular weight of the prodrug. The the drug loading is determined by UV-vis spectrophotometer and the percentage weight of drug was 10～15%.2. HA-amino acid-paclitaxel Prodrugs could self-assemble to form nanoparticles in aqueous solution. Their morphology was investigated by dynamic light scattering (DLS) and scanning electron microscopy (SEM). The average diameter of nanoparticles was about 280 nm. Nanoparticles were well-dispersed with spherical shape, and their surface zeta potentials were slightly positive. The kinetics of hydrolysis for drug delivery system was investigated. It was demonstrated that prodrugs could release paclitaxel under neutral and acidic phosphate buffer solution. The drug release rate decreased as pH decreased. It is observed the hydrolysis rate was greatly increased under enzymatic condition. Apparently, prodrug using phenylalanine as spacer showed a faster releasing rate than the other two prodrugs.3. In vitro cell inhibition for MCF-7 cells (human breast carcinoma) of prodrugs were measured by MTT method. It showed that the prodrugs exhibited higher cytotoxicity than free paclitaxel. IC50 values of HA-Amino acid-Paclitaxel prodrugs were 0.406 nM,0.253 nM and 0.336 nM (paclitaxel equivalent), which were lower than paclitaxel (0.795 nM). Hoechst-PI assay and flow cytometry (FCM) were used to analyze anti-cance mechanism of prodrugs. Consequently, results demonstrated that prodrugs significantly enhanced the extent of apoptosis-induced cell death.