Construction And Application Of Nanoparticle-based Ph-responsive Drug Delivery System

Cancer is a kind of disease that seriously threats human health,and chemotherapy is one of the major therapies to cancer.Traditional chemotherapy treats cancer by systemic administration of anticancer drugs without specificity,causing a decrease on drug utilization rate.What’s more,drug distribution over the whole body leads to side effect on normal cells and tissues.Another obstacle of chemotherapy is multiple drug resistance(MDR).Development of resistance in cancer cells greatly reduces anti-cancer efficiency of drugs.To overcome the mentioned problems in chemotherapy,nanoparticle-based drug delivery system is widely used in recent years.The nano-sized carriers process enhanced permeability and retention(EPR)effect in vivo,leading to prioritized accumulation in tumor site.With further design and construction,some delivery systems release drug controllably in trigger of special biotic environment inside cancer cells.The stimuli-responsive nanocarrier releases drug in a spatially and temporally controlled manner,maximizing the therapeutic efficacy of drug and minimizing the side effects to normal cells.Considerable development of stimuli-responsive nanocarrier has been achieved.In addition,it’s also employed in clinic.In this work,a nanoparticle-based,pH-responsive drug delivery system,NP-NaHCO3,was constructed.The nanoparticle was made of poly(D,L-lactic-co-glycolic acid)(PLGA),a biocompatible polymer,with NaHCO3 loaded inside.NP-NaHCO3 was uptake by endocytosis and got into lysosome,in which the pH value is as low as 5.0-5.5.The acidity promotes NaHCO3 to generate CO2 bubbles,breaking the nanoparticle.When co-loaded with anti-cancer drug,the nanoparticle releases drug inside cancer cells.The size of NP-NaHCO3 was optimized and the morphology was characterized by SEM.Diameter tested every day in five days changed little,suggesting good stability.To evaluate the pH-responsive drug release ability,DOX was employed as a model drug.In vitro release at different pH value was performed,and NP-NaHCO3-DOX showed higher release rate at pH 5.0 than pH 7.4,indicating that the nanoparticle released drug faster in response to acidity.Fluorescent confocal microscope characterization showed good co-localization of NP-NaHCO3-DOX and lysosome,proving that nanoparticle was uptake and got into lysosome,At last,cytotoxicity of NP-NaHCO3-DOX was measured in MCF-7 and A549-DDP cells.The toxicity of NP-NaHCO3-DOX was pretty high,and even higher than free dox and NP-DOX without pH-responsive function,showing that the constructed nanoparticle was efficient as an anticancer system.In the second part,cisplatin and TPEN,a zinc chelator,was loaded into the constructed nanoparticle to overcome cisplatin resistance,based on previous research in our group.One of the major cisplatin-resistance mechanism is related to the over expression of cellular glutathione(GSH),and GSH concentration up-regulates through a zinc ion mediated passway in stimuli of cisplatin.TPEN can chelate with Zn2+ in cells and cut the Zn2+ participated passway which increases GSH concentration,thereby reducing cisplatin combination with GSH and excretion,and finally decrease cancer cell’s resistance to cisplatin.The NP-NaHCO3-CDDP-TPEN prepared in this part was cultured with cisplatin resistant cell A459-DDP.Fluorescent microscope and fluorescent confocal microscope characterizations showed that the nanoparticle was uptake by cells in 24 h,and was co-localized with lysosome.The CDDP in nanoparticle also released faster in acidity environment than in neutral environment.While the NP-NaHCO3-CDDP-TPEN was possible to be applied to overcome cisplatin resistance,the work is unfinished and more research is still required.