Study On The One-step Synthesis And Photothermal Therapy Of Dextran-polypyrrole Nanoassemblies

Photothermal therapy is a new treatment method which transforms light energy into heat energy.It is widely concerned because of its strong selectivity and wide adaptability.In photothermal therapy,the photothermal effect of photothermal agents directly determines the therapeutic effect,and there are many kinds of photothermal agents,including inorganic photothermal agents and organic photothermal agents.Among them,polypyrrole showed good stability and strong photothermal effect.Nano materials based on polypyrrole have unique photothermal treatment and photoacoustic imaging capabilities,showing a good application prospect in the biomedical field.Although polypyrrole based nanomaterials have many advantages as mentioned above which make it become a kind of biological nanomaterials of great concern in recent years,but there are still a series of problems in their synthesis methods and biological applications.First of all,the biocompatibility of polypyrrole based nanomaterials needs to be further improved.On the other hand,most of polypyrrole based nanomaterials polymerized first and assembled later,so the preparation efficiency and size control of which are not satisfactory.Therefore,it is an urgent problem to explore new methods to synthesize polypyrrole based nanomaterials with good biocompatibility,high efficiency and controllable size.In the early stage of our group,we designed and prepared polysaccharide composite nano-assemblies based on polysaccharide and propylene monomers,and we proposed a novel “one-step polymerization/assembly process” to improve the preparation efficiency of nano-assemblies.On this basis,the “one-step polymerization/assembly process” was extended to the preparation of conducting polymers such as polypyrrole for the first time to prepare nano-assemblies.Starting from the dextran and pyrrole monomers,the dextran-polypyrrole nano-assemblies(Dex-PPy NAs)with dextran as the shell were prepared in one step,and both the preparation effectively and biocompatibility of Dex-PPy NAs were improved.Furthermore,the preparation method,functionality and biomedical application feasibility of Dex-PPy NAs were systematically studied.Specifically speaking,this research has done the following work.In this research,dextran-polypyrrole nano-assemblies were synthesized by “one step polymerization/assembly” for the first time.The size of the nano-assemblies was about 100 nm,and the size of the nano-assemblies could be adjusted by changing the amount of initiator and pyrrole.The results of dynamic laser light scattering and zeta potential show that the nanoassemblies have excellent colloidal stability in water and can be placed for up to 5 months without precipitation.In addition,the nano-assemblies have excellent photothermal properties and its photothermal conversion efficiency can reach 41%.The in vitro photoacoustic test shows that Dex-PPy NAs are composed of dextran and polypyrrole and it show strong photoacoustic effect which makes it become a potential photoacoustic imaging agent.On the basis of the successful preparation of Dex-PPy NAs,the biocompatibility,photothermal treatment ability and photoacoustic imaging ability in vivo were explored.The results showed that the Dex-PPy NAs had excellent biocompatibility and showed no significant toxicity to 4T1 cells(mouse breast cancer cells),HUVECs cells(human umbilical vein endothelial cells)and A549 cells(human lung adenocarcinoma cells).Compared with the control group(phosphate buffer solution combined with808 nm laser light),the experimental group(Dex-PPy NAs combined with808 nm laser light)can significantly inhibit the tumor growth of mice.Finally,after injecting Dex-PPy NAs solution into mice,the structure of tumor tissue of mice was clearly shown by photoacoustic imaging.In conclusion,a new photothermal material: Dex-PPy NAs was successfully prepared by “one-step polymerization/assembly”.On the one hand,it expands the scope of application of “one-step polymerization/assembly” method reported by our group,on the other hand,it also explores new methods to prepare polypyrrole based nanomaterials and improve its preparation efficiency and biocompatibility.In addition,cell and small animal level studies have confirmed that Dex-PPy NAs have excellent photothermal treatment effect and photoacoustic imaging ability,so it is a new photothermal material with good application prospects.