| In recent decades,the morbidity and mortality of malignant tumors are increasing steadily,posing a serious threat to human health and life.The existing therapeutic methods,such as chemotherapy,surgery and radiotherapy,possess no tumor selectivity but significant side effects in clinical application.Photodynamic therapy(PDT),as a new type of treatment,attracted our attention since fluorescent imaging-guided photodynamic therapy can be acheived by choosing photosensitizer with excellent properties.With high sensitivity and avoidable side effects,PDT shows potential in cancer diagnosis and treatment.4,4-difluoro-4-bora-3a,a-diaza-sindacene(BODIPY)shows superior optical properties over other photosensitizers.By adjusting its conjuagated structure,its UV-vis absorption can be red shifted to near infrared(NIR)region,so that increasing the absorption and reducing the fluorescent background interference of biological tissues.In addition,its singlet oxygen generation efficiency can be effectively improved after the heavy atom modification,making it possible for simultinious fluorescence imaging and photodynamic therapy.However,most of the existing BODIPYs are too hydrophobic to be used directly as small molecule drugs for in vivo treatment.Therefore,in order to deliver it to the tumor site effectively,researchers have designed and developed kinds of nanomaterials,and we mainly focus on polypeptide based amphiphilic functional copolymers in this thesis.In the second chapter,firstly,we synthesized a BODIPY-Br2 with high fluorescence quantum yield and singlet oxygen generation yield.And then,poly aspartic acid(PAsp)was prepared via the ring opening polymerization(ROP)of N-carboxyanhydride of aspartic acid(Asp-NCA),and POEGMA as hydrophilic block was introduced via click reaction.Finally,a pH-responsive amphiphilic copolymer was prepared considering N,N-diisopropyl ethylenediamine could be protonized under acidic condition,showing obvious promoting release behavior.The BODIPY-Br2 was encapsulated into the micelles to test the PDT efficiency against HepG2 cancer cells in vitro.At a low concentration of photosensitizer(5.4 ?M)and extremely low energy density(635 nm,12 J/cm2)light irradiation,the cell inhibition rate was increased by 40%or more.At the same time,the endocytosis of nanoparticles by cells can be observed by near-infrared fluorescence imaging,indicationg the success of imaging and therapeutic synchronization.In the third chapter,we mainly studied the visualized photodynamic therapy behavior of galactose targeted polypeptides on hepatocellular carcinoma cells.Poly lysine(PLys)as hydrophobic segment was prepared via ROP of lysine-NCA,while POEGMA was synthesized for hydrophilic segments.By introducing galactose into the head end of copolymer to realize donor-receptor recognition,it could self-assemble into micelles in aqueous solution to load BODIPY-Br2.Compared with Hela cells,the nanoparticles showed excellent treatment effect in the targeted therapy of HepG2 cells,not only efficient cell endocytosis behavior,but also obvious cell inhibition rate increase at extremely low energy density(635 nm,25 mW/cm2,10 min)irridiation.In the previous studies,it was found that the efficiency of PDT could also be limited by some factors during treating process.Therefore,in Chapter 4,we firstly prepared a NHS-BODIPY-Br with excellent optical properties,which could be connected to polymer by chemical reaction.Then,using mPEG-OH as the initiator,the reductive responsive polypeptides based on cystine disulfide bonds were prepared,and DOX was then introduced to the nanogel via dialysis method.The near infrared nanogel showed apparent increased behavior of drug release in the presence of glutathione(10 mM),and satisfactory near infrared imaging capability,photodynamic therapy-chemotherapy combined treatment efficiency.In order to alleviate the limitation of PDT caused by hypoxia,we studied the photodynamic therapy behavior of the self-supplying oxygen systems in the following works.In the fifth chapter,based on the ability of MnO2to catalize the decomposition of H2O2 for oxygen production,we prepared a MnO2 loaded nanoparticle after the amino protection of PLys to reduce potassium permanganate.BODIPY-Br2 loading was conducted using emulsion-evaporation method for further self-assembly.The test results showed that this system could accelarate the decomposion of H2O2(250 ?M)for oxygen generation.In vitro studies against HepG2 and 4T1 tumor cells showed that,even under hypoxia atmosphere,the cell inhibition rate increased significantly after an extremely low energy density(635 nm,25 mW/cm2,10 min)light irriadtion.At the same time,the tracking imaging of cancer cells was achieved by the excellent near infrared fluorescence property of BODIPY-Br2.In Chapter 6,considering the oxygen carrying ability of blood red cells,we used polypeptide and hemoglobin to prepare an artificial red blood cell as an oxygen carrier to improve the effect of photodynamic therapy.The alkynyl modified PAsp and azide modified hemoglobin were combined through click reaction in aqueous solution,reserving the natural activities of protein.In addition,NHS-BODIPY-Br was binded with the amino group at the end of the polymer,which could self-assemble into micelles in aqueous solution to avoid the drug leakage during delivery process.In vitro studies against HepG2 cancer cells demonstrated the ability of the prepared nanoparticles to carry oxygen,trace and treat cancer cells.The system showed good biocompatibility and fluorescence imaging capability,and it could also significantly kill cancer cell even under hypoxia when exposed to low energy(635nm,25 mW/cm2,10 min)light irridiation.In summary,in this thesis,we took advantages of the fluorescence imaging and PDT ability of BODIPY photosensitizer,biocompatible and biodegradable properties of polypeptides.Based on them,we mainly prepared polypeptides via ROP of NCA to form functional nanoparticles for photosensitizer loading,aimimg to achieve near infrared imaging-guided photodynamic therapy. |
PDF Full Text Request