A Preliminary Research On A Tumor Cell Specific Activated Nano Drug Delivery System

Tumors are serious threat to health of human beings,to date,chemotherapy is still the main treatment,however,there are several shortcomings of traditional chemotherapy drugs,such as poor targeting effect,large side effects,low compliance and poor treatment effects.In recent years,Nano-drug delivery systems?NDDSs?,especially stimuli-responsive DDSs have been developed to overcome the side effects of chemotherapeutic agents,therefor,them have drawn wide attention.But,a large number of stimuli-responsive DDSs that are based on microenvironment of tumor,such as low pH,high glutathione?GSH?,inflammation also has a similar environment,thus,the tumor tissue specificity is low.Furthermore,in order to improve specificity,some studies have used ultrasound,light and other physical stimulationin to cancer therapy,however,the sensitivity is limited due to the exponential decay of light and ultrasound in vivo.Based on the above analysis,how to construct DDSs that respond to biomolecules that are aberrantly expressed in tumor cells that activated a rapid and sensitive drug release,there is an urgent need for stimuli-responsive DDSs to realize tumor cell activated drug release.For the above issues,by modifying,we construct a kind of magnetic compound nanoparticles that combine magnetic targeting with tumor cell activated ability,the therapeutic agents can be quickly delivered to the tumor tissue and specifically released with a magnetic field,therefore,significantly enhanced the antitumor efficacy and decreased the side effect of DOX.The DDS achieves the above objectives through three aspects.1.the gatekeeper of pore structure provides structural basis for tumor cells specific-response controlled drug release;2.the recognizition and conformational changes properties of the designed DNA strands could be used as a desirable gatekeeper for tumor biomarker specific-response controlled drug release;3.magnetic targeting lays the foundation for the system arriving at tumor tissue smoothlly and efficiently.Iron oxide nanoparticles?IONPs?show stable superparamagetism,high magnetic response and magnetic resonance imaging.Mesoporous silica nanoparticles?MSNs?as drug nanocarriers have many advantages,such as large specific surface area,biocompatibility,low toxicity,large pore volume and ease of functionalization.In this paper,firstly,we get IONP by chemical precipitation method,the core-shell structure?core:IONP;shell:MSN?nanoparticals were synthesized through sol-gel method,then,nanoparticles were modified with azide-functionalized,the unique pore structure made it possible to load chemotherapy drug Doxorubicin?DOX?,finally,by cycloaddition reaction,the tail of the hairpin structure DNA modified with alkyne with specific miRNA-21 recognizition is wrapped on the surface of the magnetic drug depot.The hairpin structure DNA is not only as the gatekeeper,to avoid unexpected DOX release,the head sequence of the hairpin DNA could completely complementray to miRNA-21,the DNA could specificly recognize and exclusively response to miRNA-21 through complementray base pairing to form double-stranded structure,causing conformational changes,which was from hairpin to straight chain,thus,DOX could efficiently and rapidly release without gatekeeper.Through the abovepreparationprocess,wedesigneddrugdeliverysystem?IONP@MSN/DOX-DNA?exhibited magnetic-targeting property and tumor cell triggered drug release for activated cancer therapy.In this subject,we have approved that we incorporated IONP,IONP@MSN and IONP@MSN-N₃ successfully by series of characterization analysis,such as fourier transform infrared spectroscopy?FT-IR?,X-ray diffraction?XRD?and energy dispersive spectrometer?EDS?,fourier transform infrared spectroscopy and UV-Vis spectrum of IONP@MSN-DNA showed that a hairpin structure DNA is wrapped on the surface of IONP@MSN-N_3.Based on the transmission electron microscopy?TEM?,we demonstrate that we have got the core-shell structure nanoparticals?IONP@MSN-N₃?,the average size about 150 nm.The specific surface areas,total pore volumes and pore-size of IONP@MSN-N₃ were calculated to be767.1698 m2/g,1.03 cm³/g and 3.04 nm by nitrogen adsorption and desorption experiments,therefore,the pore size of IONP@MSN-N₃ was suitable for loading DOX.The results of UV-visible scanning and drug loading results showed that IONP@MSN-N₃ were successfully and efficiently loaded with Doxorubicin?Dox?,the loading efficiency of DOX achieved 89.4%,furthermore,once the miRNA-21molecules were added,abundant release of Dox was observed,the release rate of DOX in 48 hours highly achieved 65.7%,In comparison,the release rate of DOX in the absence of mi RNA-21 is only 11%.the average size about 170 nm was showed by TEM,furthermore,magnetism measurement showed that IONP@MSN/DOX-DNA had stable superparamagetism.We used the HepG2?human liver cancer?cells as model and HL-7702?normal liver cells?as control to evaluate the designed tumor cell activated drug delivery system's anti-tumor ability in-vitro.the miRNA-21 levels of HepG-2 and HL-7702cells were investigated via RT-PCR,the miRNA-21 level in HePG-2 cells is 3.57times that in HL-7702 cells,the difference is significant.In the case of IONP@MSN/DOX-DNA treated HePG-2 cells and HL-7702 cells for 8 hours under the same conditions,the intracellular release of DOX within HePG-2 and HL-7702cells were observed by confocal laser scanning microscope?CLSM?,a large amount of DOX was observed in HePG-2 cells,On the contrary,almost no DOX was observed in HL-7702 cells,the above studies demanstrated the tumor cell?mi RNA-21high expression?activated DOX release ability of the prepared.In the cases of IONP@MSN/DOX-DNA?20?g/mL?treated groups,the cell inhibition rate in HepG-2 cells and HL-7702 cells in 24 hours achieved 68.7%and 25.2%respectively,the apoptosis rate achieved 58.50%and 18.01%respectively,indicating that the therapy of nano-drug delivery system induced tumor cell selected apoptosis significantly.Furthermore,the apoptosis rates of IONP@MSN/DOX-DNA*?DNA*,hairpin structure,no response to miRNA-21?treated HepG-2 cells and HL-7702 cells were 14.74%and 12.2%with no significant difference,indicating the tumor cell activated therapeutic effect of IONP@MSN/DOX-DNA,decreasing the severe side effect of DOX to normal cells.We used the HepG2 tumor-bearing BLAB/C nude mice as models to evaluate the designed tumor cell activated drug delivery system's anti-tumor ability in-vivo.The distribution of IONP@MSN/IR783-DNA in nude mice was investigated by NIR fluorescence imaging system,compared with the free IR783 group,the IONP@MSN/IR783-DNA could extend the in vivo circulation time of IR783 and had passive targeting,more importantly,in the case of a magnet glued onto tumor site,the magnetic targeting property of IONP@MSN-DNA significantly.Pharmacodynamics results showed that the tumor growth inhibition rates of IONP@MSN/DOX-DNA group and IONP@MSN/DOX-DNA+MF group were 72.4%and 84.2%,and IONP@MSN/DOX-DNA*did not have effect to tumor,it indicated that the designed tumor cell activated drug delivery system has significantly anti-tumor activity.The pathological results confirmed the tumor growth inhibition effect of IONP@MSN/DOX-DNA and reduced the toxic side effects of DOX obviously.The MR imaging result in nude mice showed that the IONP@MSN-DNA had a great MR imaging ability.