Preparation Of PH Responsive Silica Nano-drug Delivery Systems For Researching Of Antitumor Activity

Traditional cancer treatments including surgical treatment,radiotherapy and chemotherapy in clinical,and chemotherapy is the most commonly used.However,due to the side effects of drugs and multi-drug resistance?MDR?,the therapeutic effect of chemotherapy is limited,meanwhile,the patient suffered great pain during the treatment.In order to solve these two challenges,the stimulus-responsive nano-drug delivery system?NDDS?,which can reduce the leakage of drugs in the normal tissue environment,has been developed and widely used.When the NDDS was took into a specific location of cancer cells,the release of drugs by stimulating the environment to reduce the toxicity to normal tissue and cell.Nobel Prize winner Christian de Duve suggested that cell death can be caused by lysosomes to overcome MDR of cancer cells.The dissolution of the lysosome membrane makes the autolysis upon rupture of some cells,once the lysosome membrane permeabilization?LMP?and the release of certain cathepsins from the lysosome into the cytoplasm is considered to trigger cell death by apoptosis or apoptosis-like pathways.This approach effectively overcomes the MDR of cancer cells,it can provide a new direction for cancer treatment.The application of silica nanoparticles as a carrier of NDDS has become a hot pints in nano-medicine research,mainly because of their non-toxic,uniform particle size,large surface area,excellent biocompatibility and stability.Especially with a certain response of the nano-carrier,through the stimulus factor to achieve a controlled release of the drug,which is important to improve the therapeutic effect.Based on this research,two kinds of pH responses NDDS were constructed by using two different structures of silica as carrier.The drug release of NDDS was explored in different pH environment and studied the inhibitory effect on the cell viability of Michigan Cancer Foundation-7?MCF-7?and Michigan Cancer Foundation-7/drug resistant?MCF-7/ADR?cells.Includes the following three parts:?1?Construction of NDDS based on Mesoporous Silica and to study its controlled release.MSNs were prepared according to a simple and efficient synthesis method,take cetyltrimethylammonium chloride?CTAC?as the surface active agent,tetraethylorthosilicate?TEOS?as the source,triethyl alcohol amine?TEA?as the alkali source.The physical and chemical properties of MSNs were characterized using TEM and IR.it was found that they were composed of a uniform and arranged in regular.To obtain DOX@MSNs,DOX,as a drug model molecule,was loaded into the MSNs.The in vitro release of DOX was examined with different pH values.The experimental result show that the loading efficiency and the encapsulation efficiency of DOX was 5.8% and 27.7%.The release of drug have a pH response,with less release?7.62%?and very slow release at pH 7.4,and the release rate was increased?up to 42.2%?in a weakly acidic environments.This release characteristics can play a better role of tumor inhibition.The results of cytotoxicity test showed that MSNs was non-toxic to cells and had a excellent biocompatibility.This NDDS has a potential application value and it is expected to be used in controlled release of nano-drug delivery systems in tumors.?2?Construction of pH response NDDS based on hollow mesoporous silica?HMSNs?.HMSNs was prepared by modified Stober mothed.Firstly,silica microspheres was synthesized by taking trimethoxy?octadecyl?silane?C18TMS?as the surface active agent,TEOS as the source,ammonia as the alkali source.And then,the nanoparticles were dispersed into 0.2 M sodium carbonate solution at 80 o C for 2 h.Finally,the C18 TMS was removed by calcination at600�C for 6 h.The characteristic of HMSNs exhibited a uniform size and excellent monodispersed by TEM.For the preparation of DOX-HMSNs?DMSNs?,DOX was loaded into the HMSNs.Then,to obtained BGNSs-SBC and BGNSs-AC,the DMSNs were dispersed into0.2 M sodium bicarbonate?SBC?and ammonium carbonate?AC?solution.The loading efficiency of drug was improved after being treated with SBC and AC.The result showed that the drug has been loaded into the HMSNs cavity by TEM characterizes.The drug release test results show that there was a small amount of drug leakage in normal physiological conditions.However,in intracellular lysosomal conditions of the cells at pH 5.0,the release rate was increased and the cumulative release from BGNSs-SBC and BGNSs-AC could reach 51.4%and 44.9%,respectively.BGNSs-SBC can release more DOX and faster than BGNSs-AC in acidic intracellular compartments.Ultrasound images assay showed that a large number of bubbles formed when BGNSs-SBC and BGNSs-AC were treated with a pH 5.0 buffer and BGNSs-SBC generated more bubbles at a higher speed than BGNSs-AC.These confirm that a significantly greater number of CO₂ bubbles were generated to promote the release of drug with a weak acid environment.?3?The application of BGNSs-SBC and BGNSs-AC in inhibiting the activity of cancer cells.Use MCF-7 and MCF-7/ADR as cell models,the anticancer activity and the effects on drug resistance cell of BGNSs-SBC and BGNSs-AC were investigated.The results of MCF-7cell activity showed that BGNSs-SBC and BGNSs-AC had high anticancer activity.MCF-7/ADR cell activity test results showed that BGNSs-SBC and BGNSs-AC anti-drug activity was better than free DOX,and the best effect of inhibition is BGNSs-SBC.Indicating that these two NDDS can effectively overcome the resistance of cancer cells.CLSM was used to detect the DOX distribution in MCF-7 cells,free DOX is distributed in the nucleus,whereas DOX released from BGNSs-SBC and BGNSs-AC is mainly distributed in the cytoplasm and lysosome.The DOX did not enter the nucleus,but also had a high anti-tumor activity,suggesting that the anti-tumor mechanism of these two NDDS is different from the others NDDS.The result of lysosome imaging and Caspase-3 activity was found that the LMP of cancer cells was significantly improved when treated by BGNSs-SBC and BGNSs-AC,In contrast,the BGNSs-SBC increased more.This result makes the release of certain cathepsins from the lysosome into the cytoplasm to trigger cell death by apoptosis or apoptosis-like pathways.Compared to BGNSs-AC,BGNSs-SBC can more effectively overcome the MDR of cancer cells.