Folic Acid Modified Polydopamine Coated Copper Oxide Nanoparticles For Synergistic Therapy Of Tumor

Cancer is one of the leading causes of death in most countries.China has become a"cancer country"because of its large population base.At present,almost all the traditional cancer treatments have the defects of poor specificity and serious side effects.With the development of nanotechnology,it has been found that some nanostructures have similar catalytic properties to natural enzymes.Since it was found that iron-based materials have peroxidase（POD）enzyme activity,they can react with hydrogen peroxide（H₂O₂）to produce reactive oxygen species（ROS）.Many metal ions such as Cu²⁺also have POD enzyme activity,which can produce ROS for chemical dynamic therapy（CDT）.Recently,it has been found that CuO nano-leaves can adsorb glucose and oxidize it to gluconic acid,which is similar to glucose oxidase（GOD）for starvation therapy（ST）,and Cu²⁺in CuO can mediate Fenton-like reaction,so CuO nanoparticles（NPs）have dual enzyme-like activities of POD and GOD.CuO nano-enzyme is a kind of metal oxide,which is also toxic to normal cells,so it is necessary to modify CuO to improve its biocompatibility and give it the ability of active targeting and stimulus response release without affecting its double enzyme activity.Monotherapy is often limited in the treatment of tumors,so synergistic therapy has attracted much attention.Because tumor cells are less heat-resistant than normal cells,photothermal therapy（PTT）has also become a popular method for specific treatment of tumors.Heat shock protein suppresses the warming effect,resulting in poor therapeutic effect of PTT,but the combination of ST,PTT and CDT reduces the synthesis of ATP due to the consumption of glucose,which reduces the expression of heat shock protein and improves the effect of PTT.ST produces gluconic acid,reduces pH in tumor microenvironment（TME）,increases the rate of Fenton-like reaction and enhances the therapeutic effect of CDT.The temperature increase caused by PTT can undoubtedly promote the rate of Fenton-like reaction and glucose oxidation,and the three methods can play a synergistic effect in the treatment of tumors.Polydopamine（PDA）is a photothermal conversion agent with good biocompatibility.Its modification on the surface of the substrate can not only reduce its toxicity to normal cells,but also can be used as a photothermal agent for PTT.Based on the above considerations,we prepared a kind of copper oxide nanoparticles（CuO NPs）with folic acid（FA）modified PDA coating.The prepared CuO NPs has small size,large surface area and efficient double enzyme activity of POD and GOD,so it can be used in CDT and ST.Dopamine hydrochloride was self-oxidized and polymerized on the surface of CuO NPs to form PDA coating,which gave CuO the ability of response and release under acidic conditions,improved biocompatibility,and its good photothermal properties could be used in PTT.Finally,the outer layer is modified with FA group to give the material active targeting ability.The morphology and properties of the synthesized nanoparticles were characterized by transmission electron microscope（TEM）,Fourier transform infrared spectroscopy（FT-IR）,nano-particle size potential analyzer and X-ray photoelectron spectroscopy（XPS）.The results show that CuO@PDA-FA NPs with a particle size of about 190 nm was prepared.The experiments of degradation of methylene blue（MB）and glucose oxidation confirmed that the material had POD enzyme activity and GOD enzyme activity.When glucose reacted with copper oxide with the same molar ratio,the yield of gluconic acid reached 60.6%.The yield of gluconic acid increased to 82.6%at 45℃.Photothermal conversion experiments show that the material has good photothermal effect and photothermal stability,and the photothermal conversion rate is 17.58%.The results of cytotoxicity test,cell uptake test and ROS production test showed that CuO@PDA-FA NPs could actively target tumor cells and kill tumor cells through photothermal therapy（PTT）/chemical kinetic therapy（CDT）/starvation therapy（ST）.The apoptosis rate of cells treated with synergism reached 59.9%.This multi-group modified nano-enzyme has potential application value in targeted and cooperative therapy of tumor.