Construction And Performance Study Of Multifunctional Nano-drug Delivery System Sctivated By Tumor Microenvironment

Chemotherapy is the most conventional cancer treatment in clinical practice.In order to solve the drug resistance caused by a single chemotherapy,it is impossible to diagnose and monitor the distribution of the drug in the tumor site at any time,and the curative effect is not good,and the side effects are serious.In the field of tumor therapy,the multifunctional drug delivery system（DDS）for cancer treatment has attracted great interest.The development of early diagnosis and monitoring capabilities,enhanced drug delivery,effective biodegradation and multiple treatment methods Co-treatment of DDS is still a scientific challenge.Multifunctional DDS is the integration of multiple treatment methods and imaging technologies in a single nano-platform,which combines the advantages of each single therapy and makes up for the shortcomings of each therapy,thus producing a stronger synergistic therapeutic effect than these theoretical combinations.Realize a multi-mode collaborative treatment and imaging system,and improve the rationality of cancer treatment development methods.The research content of this paper is mainly composed of the following three parts:1.A functionalized nano-drug delivery vehicle with a tumor microenvironment（TME）p H（4.5-6.5）and H₂O₂ specific activation of its self-destructive structure was constructed:poly（（hydroxyethyl methacrylate-methoxybenzene）Boric acid pinacol ester）-（ethylene glycol methyl methacrylate）-（diethylenetriaminepentaacetic acid）-（1-vinylimidazole）-（4-vinylphenylboronic acid）)（PBEM-PEG-DTPA-VI-PBA）.We characterized the structure of hydrophobic monomers and polymers by ~1H NMR,and characterized the particle size and morphology of polymers by dynamic light scattering（DLS）and transmission electron microscopy.The hydrodynamic size of the nano-medicine delivery carrier is about 112 nm,with a spherical distribution.The nanoparticles self-assemble into amphiphilic"core-shell"nanomicelles in the water phase,which can embed the anticancer drug DOX in the hydrophobic core.At the same time,vinylimidazole（VI）can be equipped with low-toxic cadmium-free quantum dots（QD）for photodynamic therapy（PDT）and imaging.It can produce cytotoxic hydroxyl radicals（·OH）and DOX forms a synergistic treatment system of chemotherapy and PDT.The PBEM structure is stimulated by TME to produce a methylquinone compound,which can consume glutathione（GSH）in the tumor site,thereby enhancing the oxidative stress at the tumor site.It is worth noting that we use PBA as a tumor cell targeting ligand to specifically target sialic acid or sialic acid residues on the surface of tumor cells,so that the nano-drug delivery system can better accumulate in the tumor site and minimize the drug Off-target toxicity.At the same time,DTPA chelated ^99mTc⁴⁺radioisotope is introduced for single-photon emission computed tomography（SPECT）imaging,which forms a dual-mode complementary imaging system with fluorescence imaging of QDs to realize the functions of diagnosis,monitoring and operation guidance of the nano-drug delivery system.2.A polymer micelle with specific activation of tumor microenvironment（TME）was designed by the reversible addition-fragmentation chain transfer（RAFT）polymerization method:poly（（methacryloyl chloride-trimethylolethane-Tert-butylphenylboronicacid）-（ethyleneglycolmethylmethacrylate）-（diethylenetriaminepentaacetic acid）-（1-vinylimidazole）-（folic acid））（TBPBA-PEG-DTPA-VI-FA）、Through the p H and H₂O₂ sensitivity of the borate bond,polymer micelles that can self-assemble into an amphiphilic"core-shell"structure in the aqueous phase are synthesized,and the anticancer drug DOX can be embedded in the hydrophobic core.The TBPBA structure is specifically activated in TME and its self-destructive structure is specifically activated.The polymer micelles swell and split,and then the embedded drug DOX is released to complete the chemotherapy phase.Secondly,cadmium-free AgInS₂ QDs with high extinction coefficient,strong photoluminescence,high light stability,wide absorption band,narrow emission band and low toxicity were synthesized in the water phase for photodynamic therapy.QDs can generate cytotoxic hydroxyl radicals（·OH）under light conditions,and form a dual-mode synergistic treatment system with DOX embedded in the polymer micelle core.In this experiment,we tested and characterized the fluorescence emission,ultraviolet absorption,stability,particle size and morphology of QDs and polymers,and studied the drug release and anti-tumor properties.The results show that QDs have a spherical distribution with a particle size of about 4 nm and have good light stability.The hydrodynamic size of the nano-drug delivery vehicle is about 115 nm,with a spherical distribution,with enhanced tumor penetration and retention（EPR）effect,and passively targeting tumor tissues.And we introduced FA into the nanostructure as an active targeting ligand to target the over-expressed FA receptor FR on the surface of tumor cells,so that the nano-drug delivery system can better accumulate at the tumor site and minimize drug off-target toxicity.It is worth noting that two biological imaging methods are used in the nanoparticles at the same time,SPECT imaging and fluorescence imaging for treatment,monitoring and guided surgery.The anti-tumor performance structure in vivo and in vitro shows that the nanoparticles have good p H and H₂O₂ responsiveness and biocompatibility,can accurately deliver loaded drugs to tumor cells,have good drug release properties,and generate hydroxyl groups under light conditions.Free radicals.Compared with free DOX,this chemotherapy and PDT synergistic treatment system has a lower IC₅₀,can better inhibit tumor growth and metastasis,and shows a good synergistic therapeutic effect.3.In view of the fact that the intra-tumor transport of nanoparticles depends on their diffusion and mobility in the tumor interstitium,the size of nanoparticles has been shown to play an important role in controlling tumor penetration.In this experiment,we designed a nano-drug delivery vehicle whose size can be changed:Dex₂₀₀₀₀-FA@Dex₆₀₀₀@DTPA-CDI-PBA@AgInS₂@Zn O@DOX,which has the potential to overcome systemic and local barriers.Passive targeting（EPR effect）and active targeting of FA promote the effective accumulation of nanoparticles at tumor sites and minimize drug off-target toxicity.It is worth noting that this multifunctional size transformable nano-drug delivery system forms a borate bond through the PBA in Dex₆₀₀₀@DTPA-CDI-PBA and the adjacent hydroxyl group in Dex₂₀₀₀₀-FA.Under stimulation,Dex₆₀₀₀@DTPA-CDI-PBA@AgInS₂@Zn O@DOX coated with Dex₂₀₀₀₀-FA is released,and then Zn O is dissolved into Zn²⁺to release DOX,and at the same time the size of the nanoparticles is transformed,and a deeper tumor penetration depth is obtained.A nano-imaging therapeutic agent with synergistic treatment of chemotherapy and PDT and dual-mode imaging of SPECT and fluorescence is formed.The results of vitro experiments showed that light-induced AgInS₂ QDs generated hydroxyl radicals（·OH）in cells.Compared with free DOX,Dex₂₀₀₀₀-FA@Dex₆₀₀₀@DTPA-CDI-PBA@AgInS₂@Zn O@DOX significantly inhibited the proliferation of B16F10tumor cells,showing a good tumor suppression efficiency.