Construction Of Polymer Drug Delivery System For In-situ Generation Of NO Activated By Reactive Oxygen Species And Its Biomedical Application

As an emerging field,gas therapy has attracted more and more attention in the treatment of many diseases.At present,a lot of research has focused on the unique dual role of nitric oxide?NO?gas therapy.At low concentrations,NO can promote tumor growth;at high concentrations,NO can not only directly kill cancer cells,but also a kind of attractive antibacterial agent while avoiding the emergence of drug resistance.However,the loading of NO molecules is extremely unstable and difficult,the half-life of low molecular weight NO donor compounds is relatively short,and the difficulty of targeted delivery of NO hinders clinical application.L-Arginine?L-Arg?is a natural amino acid that can be used as a donor of NO,has good biocompatibility,and can controllably release NO in the presence of ROS.Therefore,this paper designs pH-responsive materials based on the specificity of the tumor and bacterial microenvironment,and uses the sequential induction process to generate reactive oxygen species?ROS?to activate the NO macromolecular prodrugs to generate the active drug molecule NO in situ.Specific research contents include:?1?In recent years,NO gas therapy has attracted extensive attention.L-Arg can react with ROS in tumor cells to generate NO,which is an effective method of tumor treatment.However,endogenous ROS in most types of tumor cells still cannot respond effectively.?-Lapa can promote the increase of H₂O₂ concentration in tumor cells,making it an effective method to increase ROS in tumor cells,and then high concentration of H₂O₂ can oxidize L-Arg to NO to kill tumor cells.In order to form more toxic hydroxyl radicals?·OH?and peroxynitrite?ONOO^-?in tumor cells,we introduced ferrocene?Fc?into this nano drug-loading system.The Fc-catalyzed Fenton reaction produces·OH.In addition,·O₂^-,which is produced by Fc and H₂O₂through the Haber-Weiss reaction,can react rapidly with NO to produce ONOO^-.In order to avoid premature leakage of L-Arg during in vivo transportation,a PCL-b-PArg?NO macromolecular donor?rich in arginine was synthesized.The hydrophilic chain?PArg?of PCL-b-PArg can be used as the donor of NO,and its side groups are rich in positively charged guanidine groups,which can be internalized better by tumor cells.In addition,the hydrophobic chain?PCL?can be loaded with hydrophobic drugs??-lapa and Fc?.In order to hide its penetrating ability in the circulation of the body,we synthesized a negatively charged pH-sensitive hydrophilic diblock polymer PEG-b-PDMA.First,PCL-b-PArg is self-assembled to for m positively charged nanoparticles,and then PEG-b-PDMA is coated on the particle surface through electrostatic interaction.Cell experiments have shown that L-Arg and?-lapa are almost non-toxic in a certain concentration range when used alone,and have a good therapeutic effect due to the production of NO when used in combination;the results of cell fluorescence experiments confirmed that HeLa cells had a good endocytosis effect on nanoparticles and the effective production of NO;animal experiments further confirmed that the nanoparticles had good antitumor effects.Both in vivo and in vitro experiments show that this cascade synergistic therapy through ROS generation and NO release has a significant inhibitory effect on cancer cells,providing new idea for NO gas therapy.?2?Two kinds of polymers,Ac-Starch-PAsp and CS-b-PArg,were designed and synthesized,and self-assembled with glucose oxidase?GOD?and?-1,4-glucan glucohydrolace?GOH?on the sponge by electrostatic adsorption to form a pH-responsive antibacterial dressing?GOH/GOD/Starch/CS-b-PArg?for promoting wound healing,which can be used for effective wound antibacterial treatment.In the acidic microenvironment of wound infection,the acetal bond that protects the starch hydroxyl group is broken,exposing the starch molecules,which are hydrolyzed to glucose under the action of GOH,and then generates a large amount of H₂O₂ at the wound site under the catalysis of GOD.H₂O₂ further catalyzes the in situ production of NO by macromolecular donor CS-b-PArg,thereby promoting wound healing.Bacterial experiments show that the dressing can effectively produce H ₂O₂ and NO under acidic conditions,and has excellent antibacterial effect.The sequential induction process of ROS and NO generation provides new ideas for wound healing of bacterial infections.This paper mainly designs responsive materials based on changes in the microenvironment of tumor tissues and bacterial infection wounds,and then studies their anti-tumor and antibacterial abilities that are activated by ROS in situ to produce NO,which provides a new idea for the construction of NO release system.