Design, Synthesis And Evaluation In Vitro Of An Amphiphilic Anticancer Drug-drug Conjugate Delivery System

Currently, most anticancer drugs have some limitations includingpoor water solubility，short drug half-life, rapid blood clearance, low tumorselectivity and severe side effects for healthy tissues. These drawbackslimit the clinic applications of the drugs. In order to improve thebioavailability of the drugs, a lot of nanosized materials are used ascarriers of the drugs to enhance their water solubility, prolong theircirculation in blood compartments, reduce side effects to normal tissuesand increase the accumulation of the drugs in tumor sites via the enhancedpermeability and retention (EPR) effect. With the help of nanocarriers, thedrugs show better efficacy against the tumor than that of free drugs.However, the nanocarriers usually have no direct therapeutical effect bythemselves. Furthermore, many carriers may arouse side-effects tokidneves and other organs in the course of metabolism and excretion, suchas toxicity and inflammation. To answer these questions, we design andsynthesize a kind of an amphiphilic anticancer drug-drug conjugatethrough a biodegradable ester bond. The amphiphilic conjugate canself-assemble into nanopaticles in water to construct an amphiphilicanticancer drug-drug conjugate delivery system (AADDCDS). The nano-particles have both advantages of free drugs and nanocarriers. The detailsare described as follows:(1) The synthesis, self-assembly and in vitro anticancer activity ofgemcitabine-chlorambucil (Gem-Cb) conjugate: An amphiphilic Gem-Cb conjugate was synthesized through anesterification. The chemical structure of Gem-Cb conjugate wascharacterized by1H NMR,13C NMR, MS, FTIR and UV-Vis. Owing to itsamphiphilic property, the Gem-Cb conjugate can self-assemble intonanoparticles in water. The results of DLS and TEM demonstrated that theGem-Cb nanoparticles (Gem-Cb NPs) were spherical micelles with anarrow unimodal distribution and an average hydrodynamic diameter ofapproximate154.4nm. The in vitro release behavior of Gem-Cb NPsindicated that the free Gem and Cb could be released at a weakly acidicenvironment (pH5.0). The cytotoxicity and anticancer activity of Gem-CbNPs were estimated using MTT assays. The results show that Gem-Cb NPshad low cytotoxocity against normal cells (L929cells) but much morecytotoxocity to MCF-7cancer cells. The results of flow cytometry andfluorescence microscope showed that showed that Gem-Cb nanoparticlescould be internalized by MCF-7cells efficiently.(2) The synthesis and characterization of cytarabine-camptothecin(Ara-C-CPT) conjugate linked by a succinic acid as a spacer.Hydrophilic anticancer drug cytarabine (Ara-C) reacted with succinicanhydride to form an esterification product with a carboxyl group at first.Then the product reacted with hydrophobic anticancer drug camptothecin(CPT) through another esterification to produce an amphiphilic drug-drugconjugate (Ara-C-CPT).1H NMR,13C NMR and MS techniques wereused to characterize the chemical structures of Ara-C-CPT conjugate andits intermediates.