Synthesis And Research Of Novel Dual-ligand Modified Chitosan To Prepare Targeted Drug-loading Nanoparticles

In recent years, China’s environmental pollution has been gaining more and more attention from the public; especially the problem of haze caused by air pollution has triggered a nation-wide concern, and the resulting health hazards are increasingly raising people’s precaution awareness. According to newly published reports, the fatality rate of cancer has surpassed heart diseases in Wuhan for several consecutive years; in light of that fact, environmental pollution is mostly to be blamed for causing various cancers and pushing them to rise up as the number one health-killer. Confronted with the increasingly serious problem of high incidence of cancer, there is unfortunately no widely used effective treatment to cancer at the present; while the concept of "targeted drug delivery" formed a century ago has been developed into practical application in some areas, its potential use in the field of cancer treatment is heating the forefront of pharmaceutical researches among scientists and researchers and constantly making progresses. Based on both extensive and intensive researches conducted by former scientists, researchers, and predecessors as well, this study aimed to explore the synthesis of a novel dual-ligand conjugated material and its use in preparing nanoparticle systems, which could be potentially developed as a targeted drug delivery carrier; therefore a preliminary inquiry into the drug-loading performance of the nanoparticles was conducted, hoping to produce more research significance for the "targeted cancer therapy" field.Firstly, the naturally occurring polysaccharide- chitosan(CS) was selected in this study as the polymer matrix for its excellent biocompatibility, while Folic Acid(FA) and Biotin as dual cancer cell-targeting ligands, in order to attain functionally modified chitosan through the amidation reaction between a large number of aminos of chitosan molecular chains and the carboxyl groups of both FAs and Biotins; in the coupling reaction, EDC and DDC(Both are carbodiimide condensing agents; the former is water-soluble, whereas the latter oil-soluble.) were used to activate the carboxyl group of FA and Biotin respectively to react with amino, followed by simultaneously adding both active esters into the same reaction to prepare the dual ligands conjugated chitosan in a single procedure. Afterwards, different structural analytical techniques, e.g. FITR, UV-vis and 1H-NMR and so on, were applied to characterize the purified product, which proved the successful conjugation of the double ligands with chitosan, and grafting rate of each ligand, FA and Biotin, was 7% and 15% respectively, indicating chitosan was successfully functionalized as an innovatively synthesized dual-ligand modified polymer(FA-CS-Bio) that can be potentially built into targeted drug carriers against cancer cells.Secondly, an orthogonal optimization(L933) of synthesis of the folated chitosan(FA-CS) was implemented, and a consequent increase of FA’s grafting rate from 7% to 9% was obtained under the optimal set of synthetic conditions, which suggested the average number of coupled FAs to per chitosan molecule reaches 14, imparting the material a stronger capability of targeting corresponding receptors on cancer cell membrane. What’s more, using ionic cross-linking method, the sodium tripolyphosphate(TPP) was added into acidic chitosan solution so that the two components formed nanoparticles by electrostatic adsorption and gelation under mild conditions; the three main factors of gelation, e.g. chitosan concentration, pH, and CS/TPP mass ratio, were investigated and optimized by orthogonal experiment, from which a conclusion was drawn that the former two factors were found to have a more significant effect on the size of nanoparticles within the range of selected levels, and that the hydrated average particle diameter of the nanoparticles prepared under the optimal combination of the three conditions is 204.5nm with relatively narrow distribution; further observation by SEM showed most of the particles’ sizes range from 100 to 300 nm with regular spherical shape. Finally, as a model drug, 5-Fu was entrapped into nanoparticles prepared under the optimal set of conditions using different kinds of materials mentioned above to preliminarily test their drug-loading properties; results showed that when using FA-CS-Bio as matrix, the average hydrated diameter of nanoparticles was 148.3nm, and the drug encapsulating efficiency fluctuated between 2% and 7% as the varying properties of different materials led to changing sizes of their nanoparticles.