Studies On Synthesis,Self-assembly And NIR Photothermal Conversion Property Of Amphiphilic Block Copolymers Modified By Ketocyanine

As a research hotspot in recent years,nanomaterials have been widely used in biomedical,information transmission and other fields.Those ones generated by self-assembly from amphiphilic block copolymers,which are used as drug carriers,play key role in tumor threapy.Polymeric drug nanocarriers are with low toxicity,good biocompatibility and long circulation time.They also could inhibit selective elimination of the reticuloendothelial system.With above advantages,polymeric drug nanocarriers have wide applications in tumor targeted therapy.With the help of enhanced permeability and retention(EPR)effect of tumor tissues,nanomaterials with photothermal conversion property can gather to tumor tissue spontaneously.Under irradiation with external light,it can increase the temperature of the tumor issue in a short time.As the result,the raised temperature does great harm to the tumor until kill them,and this is so-called photothermal therapy(PTT).Based on the efficient near-infrared(NIR)photothermal conversion property of ketocyanine dyes,this thesis aims at the study of controlled synthesis,self-assembly,and NIR photothermal conversion property of amphiphilic block copolymers containing ketocyanine dyes.The work will provide some new ideas for expanding the application of amphiphilic block copolymers in tumor therapy.Here are our main research contents and related conclusions:1.Synthesis,self-assembly and NIR photothermal conversion property of amphiphilic block copolymers with PPEGMA as hydrophilic chainsIn this system,we synthesized a series of amphiphilic block copolymers PBnMA-b-P(BAPMA-co-PEGMA)with special structure via reversible addition-fragmentation chain transfer(RAFT)polymerization.In the structure of block copolymer,benzyl methacrylate(BnMA)is the lipophilic monomer,and poly(ethylene glycol)methyl ether methacrylate(PEGMA)is the hydrophilic monomer.Besides.BAPMA meant 3-(BOC amino)propyl methacrylate.Themolecular weights and molecular weight distributions as well as degree of polymerization(DP)of the monomers were determined using gel permeation chromatography(GPC)and nuclear magnetic resonance(1H NMR).The self-assembly of block copolymers was studied in mixed solvent of CH3OH/H2O.and we investigated the effect of the length of hydrophilic chains on the size and polydispersity index(PDI)of the formed micelles by using dynamic light scattering(DLS).The data showed that when the length of the lipophilic chains kept constant,the size of the micelles increased with the longer hydrophilic chains.The BOC protecting group of BAPMA could be removed with trilluoroacetic acid(TFA),and the deprotected copolymer PBnmA-b-P(APMA-co-PEGMA)could react with ketocyanine dye NIR 800,which has excellent NIR photothermal conversion performance.The self-assembly of the post-modified copolymer was also applied in CH3OH/H2O.The morphologies of the micelles before and after modification were observed under transmission electron microscope(TEM).Both the micelles were spherical,and the diameter of the micelles decreased to 38 nm from 52 nm after post-modification.In addition,the post-modified micelles showed excellent NIR photothermal conversion property,which can be confirmed from the fact that the temperature of the modified micelles aqueous solution increased to 53? from 20?under irradiation with NIR light(?max=810 nm,0.028 W/cm2)for 1 h.The result confirmed that we obtained the micelles with NIR photothermal conversion propertity successfully.Therefore,it is possible to be used in photothermal therapy of tumors.2.Synthesis,self-assembly,NIR photothermal conversion property and controlled drug release of amphiphilic block copolymers with PNIPAAm as hydrophilic chainsBased on the research of the above system.in order to increase the function of the amphiphilic block copolymers,N-isopropylacrylamide(NIPAAm)was selected in this system to replace PEGMA,and the thermo-sensitive amphiphilic triblock copolymer PBnMA-b-P(BAPMA-co-NIPAAm)-b-PNIPAAm was synthesized by RAFT polymerization.We systematically investigated the effect of the length of different chains on the size of micelles and post-modification efficiency.After optimization.the amphiphilic triblock copolymer composed of PBnMA24-b-P(BAPMA6-co-NIPAAm3)-b-PNIPAAm6(T5)was modified with NIR 800 and we obtained spherical micelles with diameter of 123 nm.PDI of 0.115 from self-assembly in dimethyl formamide(DMF)/H2O.At this time.the modification efficiency of NIR 800 was 18.8%.Under irradiation with NIR light(?max=810 nm,0.028 W/cm2),the temperature of the micelles solution just increased from 20? to 35? in 1 h,and the temperature rising tendency was not obvious.When the degree of polymerization(DP)of BAPMA was increased to 10,the modification efficiency of the triblock copolymer composed of PBnMA18-b-P(BAPMA10-co-NIPAAm5)-b-PNIPAAm19(T14-3)increased to 60.5%.Under the same irradiation conditions,the temperature of the micelles solution could increase from 20? to above 50?,indicating better NIR photothermal conversion property.We measured the transmittance of deprotected copolymer aqueous solution at different temperatures through the UV-vis spectrum and we calculated the phase transition temperature was about 41?.The temperature controlled drug release ability of the post-modified micelles was investigated using camptothecin(CPT)as the model drug.The relevant cumulative release efficiency at 55? was 70%higher than that at 25?,which verified the thermal-sensitivity of post-modified micelles from the side.Besides the controlled release of CPT,the post-modified micelles also had stable and efficient NIR photothermal conversion property.In addition,cytotoxicity experiments showed low toxicity of NIR 800,PBnMA-b-P(BAPMA-co-NIPAAm)-b-PNIPAAm and PBnMA-b-P(APMA-co-NIPAAm)-b-PNIPAAm@NIR800 towards human vein endothelial cells.Therefore,we successfully obtained the thermo-sensitive micelles modified by NIR 800.They were endowed with NIR responsive bifunction of both potential controlled drug release and photothermal therapy.3.Investigation of synthesis of amphiphilic block copolymers with NIR photothermal conversion property via ADMET polymerizationBoth of the above systems are based on post-modification method to connect ketocyanine dyes onto polymer chains.This is because ketocyanine dyes have the ability of capturing free radicals,and it is not suitable for preparing corresponding polymers by direct radical polymerization.In this system,we designed and synthesized ketocyanine monomer NIR-M with non-conjugated diene structure and hydrophilic non-conjugated diene monomer PEG600-C6.which were fit for acyclic diene metathesis(ADMET)polymerization.It is intended to use ADMET polymerization to obtain amphiphilic block copolymers with NIR photothermal conversion property directly The UV-vis spectrum showed that NIR-M also had strong absorption at 800 nm.Under irradiation with NIR light(Zmax=810 nm.0.028 W/cm2).the temperature of NIR-M solution(0.5 mg/mL,in DMF)increased from 25? to more than 60?.in 1 h,which showed the extraordinary NIR photothermal conversion properity.Subsequently,1,9-decadiene was selected as the lipophilic monomer,Firstly,during the ADMET polymerization of 1,9-decadiene,the following reaction conditions were selected:the Schlenk tube was the reaction vessel;the polymerization was applied at 70 0C and Ar atmosphere;used dry oxygen-free solvent and Grubbs II catalyst;ethyl vinyl ether was used to quench the reaction.Secondly,the effect of the amount of Grubbs II catalyst on the homopolymerization of various monomers was explored.The polymerization results proved that with more catalyst,we could obtain polymers with high molecular weights.Now,we have successfully obtained various homopolymers by ADMET polymerization.This provides the possibility for the subsequent preparation of amphiphilic block copolymers with NIR photothermal conversion property through ADMET polymerization.