Preparation Of Hemoglobin-loaded Drug Delivery Systems And Their Studies In Photodynamic Therapy

The hypoxia in tumor environment inpaires the efficacy of photodynamic therapy,and the excessively consumption of oxygen for PDT further deteriorates the hypoxia of tumours,leading to a vicious circle.To sovle this,this thesis used two kind of Hemoglobin based oxygen carrier to improve the production of singlet oxygen and PDT efficacy.Firstly,an amphiphilic triblock copolymer mPEG-b-PAA-b-PS was synthesized via ATRP and tert-butyl group removed by trifluoroacetic acid.The resulted triblock copolymer could self-assemble to form spherical nano-sized micelles in an aqueous solution.With a carbodiimide chemistry,we conjugated a photosensitizer 5,10,15,20-Tetra(4-carboxyphenyl)porphyrin(TCPP)onto the hemoglobin,then conjugated the TCPP-conjugated Hemoglobin onto the triblock polymer in the form of micelles with the same strategy.After conjugated with TCPP and polymer chains,Hemoglobin remained the capacity of O2 carrying and releasing,which was similar to that of unmodified Hb.HbTcMs could generate more singlet oxygen(1O2),owing to the supply of oxygen by Hb.MTT assay showed that HbTcMs could exert great phototoxicity on 4T1 cells and oxy-HbTcMs exerted the greatest phototoxicity.Furthermore,novel pH-responsive nano-micelles conjugated Hemoglobin(Hb)to supply adequate oxygen was designed,with a hydrophobic core to encapsulate doxorubicin(DOX)and photosensitizers chlorin e6(Ce6)for the combination of chemotherapy and photodynamic therapy.An amphiphilic block copolymer PDPA-(PAA-co-PPEGMEA)was synthesized via RAFT,the resulted copolymer could self-assemble to form spherical nano-sized micelles in an aqueous solution.The nanocomposite showed obvious pH-responsive function,and drug release of DOX from the carrier confirmed that the nanocomposite helped the DOX accumulate in acidic tumor environment.The conjugated Hb remained the capacity of O2 carrying and releasing via redox activity,which was similar to that of unmodified Hb.Compared with the native Hb,the conjugated Hb with the shield of polymer chains showed better anti-oxidation stability.Results showed that the conjugated Hb with oxygen supply generated more singlet oxygen(1O2)for enhanced photodynamic therapy.Cellular uptake on 4T1 cells showed that Ce6 encapsulated in carriers could internalized faster than free Ce6.The CCK-8 assays showed that the carriers were nontoxic and biocompatible in darkness,and further confirmed that better in vitro anti-tumor effects are achieved with the combination of chemo-and photodynamic therapy interfered by extra oxygen.