Galactosylated Chitosan For Colon Targeted Oral Drug Delivery System

Colorectal cancer(CRC)is the third most lethal gastrointestinal cancer in the world.Colon-specific drug delivery system can directly deliver chemotherapeutic drugs to the targeted site and reduce unwanted side effects caused by non-specific drug accumulation.Galactosylated chitosan(GC),a derivative of chitosan which is hydrophilic at neutral pH,is synthesized by covalently binding D-galactose units to CS through O-1,6 glycosidic linkages.GC exhibits better solubility,mucoadhesion,cell compatibility than CS and maintains low toxicity.Although a number of literatures have demonstrated that GC can significantly enhance hepatocyte-targeting ability compared with chitosan due to specific ligand-receptor interactions between galactose-moieties and asialoglycoprotein receptors(ASGPRs),studies on colon-specific delivery systems are limited.The present study aims to developing a targeted drug delivery system based on GC functionalized nanoparticles,which has capability of hosting high amounts of 5-fluorouracil(5-FU)and can deliver drugs in a cell-targeting manner.Intravenous infusion or bolus injection of FU/LV(leucovorin)has become the first-line treatment for colorectal cancer worldwide.Compared with 5-FU alone,it can significantly improve the overall survival rate,but LV drug delivery system is rarely studied.In this paper,three kinds of colon-specific drug delivery systems were designed based on galactosylated chitosan nanomaterials and used for drug targeting delivery.The main contents are as follows:1.Formulation of galactosylated chitosan/tripolyphosphate nanoparticles for targeting colon cancer cellsTo improve the solubility and specificity of chitosan to target colon cells,GC is synthesized by covalently binding D-galactose units to CS through C6-OH.Then,GC nanoparticles were used to encapsulate 5-Fluorouracil(5-FU).The nanoparticles were prepared by ionic gelation using galactosylated chitosan and sodium tripolyphosphate(TPP)in a mass ratio of 5:1.DLS analysis confirmed the size ranging from 160 to 280 nm,while surface charge of nanoparticles ranged from 18 to 25 mV.The optimized nanoparticles showed a particle size of 257±20 nm with zeta potential of 21.6 mV and drug loading of 20.11±2%.Adhesion experiments showed that GC have better adhesion property.The empty nanoparticles showed safety without relevant cytotoxicity against SW480 cells,but nanoparticles demonstrated a significant cytotoxicity against SW480 cells and SW620 cells.The specific recognization and bind to cancer cells by the galectins receptor on SW480 and SW620 were confirmed by fluorescence microscopy and flow cytometry.pre-addition of galactose in the medium,with competitive binding to the galectins receptor of SW480 and SW620 cells,resulted in a decrease in the binding of MSN-NH2/GC to the galectins receptor.Subsequently,the results that 5-FU@GC-NPs induced tumor cell death by depolarizated mitochondrial membrane on SW620 cells in vitro were confirmed by mitochondrial membrane potential measurements.It demonstrated GC could be used as a promising drug delivery carrier for the targeted delivery of drug into colonic cancer cells to improve therapeutic index and reduce side effects.2.5-Fluorouracil loaded Galactosylated chitosan-functionalized mesoporous silica nanoparticles for targeting colon cancer cellsHerein,we developed a 5FU-loaded mesoporous silica nanoparticles(5-Fu@MSN-NH2/GC)based galactosylated chitosan,which are galactose receptor-mediated materials for colon specific drug delivery system.Both unmodified and functionalized nanoparticles were characterized by scanning electron microscopy(SEM),transmission electron microscope(TEM),X-ray diffraction(XRD),Fourier transform infrared(FT-IR),nitrogen sorption,particle size,zeta potential,drug loading capacity,and drug release properties.5-FU@MSN-NH2/GC show high loading capacity and possessed much higher cytotoxicity on SW620 cells than 5-Fu@MSN-NH2 and free 5-FU.But MSN-NH2/GC did not show significant cytotoxicity.Subsequently,MSN-NH2/GC anticancer activity on SW620 cells in vitro was confirmed by cell apoptosis analysis,cell cycle and mitochondrial membrane potential measurements.These are consistent with the cellular uptake results through fluorescence microscopy and flow cytometry,which displayed MSN-NH2/GC could specifically recognize and bind to cancer cells by the galectins receptor recognition.On the other hand,it is found that pre-addition of galactose in the medium,leading to competitive binding to the galectins receptor of SW620 cells,resulted in a decrease in the binding of MSN-NH2/GC to the galectins receptor.Results demonstrated the inorganic-organic nanocomposite could be used as a promising drug delivery carrier for the targeted delivery of drug into galectins positive colon cancer cells to improve therapeutic index while reducing side effects.3.LV loaded Galactosylated chitosan-functionalized mesoporous silica nanoparticles for targeting colon cancer cellHerein,the synthesis of COOH functionalized mesoporous silica was performed by a two-step grafting.Then,we developed a LV-loaded mesoporous silica nanoparticles(LV@MSN-COOH/GC).Both unmodified and functionalized nanoparticles were characterized by SEM,TEM,XRD,FT-IR,nitrogen sorption,zeta potential,drug loading capacity,and drug release properties.LV@MSN-COOH/GC showed high loading capacity,and the release rates of LV from LV@MSN-COOH/GC showed more preferable release behavior with longer equilibrium time and higher cumulative release,indicating the drug release behavior was mainly controlled by diffusion mechanism.LV@MSN-COOH/GC and 5-FU@MSN-NH2/GC showed synergistic cytotoxicity and could down-regulate the expression of TS to galectins over-expressing colon cancer SW620 cells.The specific recognization and bind to cancer cells by the galectins-receptor recognition of MSN-COOH/GC on SW620 cells were confirmed by fluorescence microscopy and flow cytometry.Results demonstrated co-delivery of LV and 5-FU by galactosylated chitosan-functionalized mesoporous silica nanoparticles could enhance intracellular drug concentrations and achieve synergistic effects in colon cancer therapy.