Preparation Of Chitosan-Based Stimuli-Responsive Drug Delivery System And In Vitro Evaluation

Chemotherapy,as one of the important way,was applied to treat various cancers.However,chemotherapy agents can cause severe side effects due to lack of specificity.In order to improve the efficacy of treatment and reduce side effects,researchers pay more attention to nano-drug delivery systems,which can improve the dissolution and stability of chemotherapy agents.In addition,it can be passively targeted to tumor tissues by the enhanced permeability and retention（EPR）effect.There are some differences in physical and chemical properties between tumor tissues and normal physiological tissues,such as p H,GSH,H₂O₂,etc.The differences can be applied to design stimuli-responsive drug delivery systems to improve the therapeutic efficacy.Different stimuli-responsive drug delivery systems based on functionalized chitosan（PEGylation,grafted PDPA,carboxymethyl and modified with maleic acid）were fabricated with different interaction（π-πstacking,electrostatic interaction and hydrophobic interaction）.Furthermore,magnetic targeted drug delivery was prepared by introducing superparamagnetic Fe₃O₄nanoparticles.The main research contents are listed follows:1.Core-shell-corona chitosan-based micelles were designed for the tumor intracellular p H-triggered doxorubicin（DOX）delivery,via a facile in-situ micellization in an aqueous solution of DOX and polyethylene glycol（PEG）and poly（2-（diisopropylamino）ethylmethacrylate）（PDPA）dual-modified chitosan（PEG-g-CS-g-PDPA）.The effect of the PDPA modification on the diameter,drug loading-capacity（DLC）and p H-triggered drug release was investigated for the three different polymerization degrees（25,32 and 42）of PDPA.Compared with other micelles prepared,the core-shell-corona DOX/PEG-g-CS-g-PDPA₃₂micelles possessed a mean hydrodynamic diameter（D_h）of 211 nm and DLC of 54%,showing an excellent p H-triggered drug release with negligible premature drug leakage,indicating the potential application for drug delivery system.2.The morphology of the drug delivery systems（DDSs）has been recognized to play an important role in their phagocytosis,cellular interaction and distribution.However,it is a technical challenge to simply prepare the non-spherical nanoscaled DDSs.By adding aqueous solution of PEG and MAH dual-modified chitosan（PEG-SS-CS-MAH）into DOX solution,the p H/hypoxia dual-responsive nanowires was prepared via electrostatic interaction.As meanwhile,the nanopraticles was fabricated by adding DOX solution into PEG-SS-CS-MAH solution.The PEG-SS-CS-MAH/DOX nanowires（NWs）possessed a higher drug loading capacity of 58%and better p H/hypoxia dual-triggered DOX release performance with higher drug release in the simulated tumor intracellular microenvironment but a much lower premature drug leakage in the simulated normal physiological medium.The results MTT and flow cytometry demonstrated the higher tumor inhibition of NWs.3.As a zwitterionic derivative of chitosan,carboxymethyl chitosan exhibit different surface charge in different p H medium.p H responsive charge reversal carboxymethyl chitosan-based drug delivery system was prepared for p H and reduction dual-responsive triggered DOX release.PDPA,as a p H responsive core to load DOX,was grafted on PEGylation carboxymethyl chitosan via reducing responsive disulfide bonds.The proposed PEG-CMCS-SS-PDPA/DOX nanoparticles,with a high drug loading capacity of>36%and drug-loading only in their cores,showed excellent p H and reduction dual-responsive triggered disintegration and DOX release performance.Among all the reported CMCS-based DDSs,the drug delivery system possessed the lowest premature drug leakage in the simulated normal physiological medium,demonstrating the enhanced antitumor efficacy and minimized systemic toxicity.4.The toxic side effects and possible drug resistance of the chemotherapeutics hinder their antitumor efficacy.Here,a p H/reactive oxygen species（ROS）dual-triggered nanodrug was developed for the tumor-specific self-boosted drug release and synergistic chemo/chemodynamic therapy,by formulating ROS-cleavable DOX-dimer（DOX-TK-DOX）with bi-functionalized chitooligosaccharide（COS-Fc-TK）with ferrocenecarboxylic acid（Fc）and thioketal（TK）.The resultant DOX-TK-DOX/COS-Fc-TK nanoparticles with a high DOX content of 47.60%showed tumor-specific self-boosted drug release,which was triggered by highly toxic·OH generated via Fc-catalyzed Fenton reaction of the endogenous H₂O₂in tumor intracellular microenvironment.Therefore,a synergistic chemo/chemodynamic therapy with combination index（CI）of 0.94 was achieved for selective treatment of tumors.5.Superparamagnetic nanoparticles have attracted more and more interesting in advanced biomedical applications such as targeted drug release,theranostic and hyperthermia,especially the Fe₃O₄nanoparticles owing to their biodegradability and superparamagnetic characteristics.The hybrid cluster bombs were fabricated baesd on PEGylated chitosan via simply co-precipitation of poly（ethylene glycol）modified Chitosan（CS-PEG）,oleylamine modified Fe₃O₄（OA-Fe₃O₄）nanoparticles and DOX.In the presence of OA-Fe₃O₄,the hybrid cluster bomb possessed a decreased diameter,high drug loading capacity of 24.3%and saturation magnetization（Ms）of 4.11 emu/g,respectively.The cluster bomb showed excellent biocompatibility and could be uptaken into Hep G2 cells with enhanced anti-cancer efficacy in comparison with free DOX.In the tumor intracellular micro-environment,the stimuli-responsive hybrid cluster bombs disassembled and re-selfassembled into the OA-Fe₃O₄nanoparticle clusters with higher Ms for MR imaging-guided diagnosis.