Optimization Study On Diagnosis And Treatment Parameters Of Melanin-Loaded Phase-Shift Nanodroplet

It is known that the heterogeneity and complexity of tumor microenvironment limit the penetration and accumulation of nanomaterials in tumor regions.Whereas,it significantly affect the effectiveness of nanomaterial-mediated tumor diagnosis and treatment.In view of the above problems,a ultrasonic/photoacoustic dual-modal phase-shift diagnostic nanodroplet will be prepared in the paper,which can mechanically destroy the tumor microenvironment.When the phase changes into microbubbles under photoacoustic combined stimulation,it will increase the penetration and accumulation of the carrying photothermal mediators and chemotherapeutic drugs in the tumor region.At the same time,ultrasound imaging and photoacoustic imaging can be used to monitor the effectiveness of drug controlled release,so as to achieve the purpose of integrated photoacoustic tumor diagnosis and treatment.Multifunctional liquid fluorocarbon nanodroplets of shell-loaded doxorubicin(DOX)and nuclear-loaded melanin by self-emulsification are first synthesized in the paper.By scanning electron microscopy(SEM),Zeta potentiometer,UV spectrophotometer and other equipment,it characterized the prepared nanodroplets.It was found that the encapsulated melanin structure was complete with an average size of 477.6±129.5 nm,surface potential of-17±4.2m V,and good light absorption ability in the near infrared region.Then in vitro cell test of the efficacy of nanodroplet treatment found that no DOX anti-cancer drug nanodroplet combined with 1 W/cm~2.The cell survival rate was reduced to 81.09±12.92%by laser irradiation unfolding photothermal therapy.Moreover,the cell survival rate was reduced to 39.54±7.84%by nano-droplet unfolding chemotherapy with individual shell-loaded DOX,while photothermal therapy combined with chemotherapy could kill all tumor cells.The further setting of a set of experimental platforms which can simultaneously perform laser and ultrasound synergistic excitation.The combined effect of ultrasonic energy and laser energy reduce the single energy threshold required for vaporized nanodroplets,defining the 0.82 MPa negative acoustic pressure ultrasound combined with 1 W/cm~2laser power can successfully induce phase-shift of nanodroplet.Finally,a nude mouse model of A375 melanoma tumor was constructed.Finally,a model of A375 melanoma tumor nude mice was constructed,and the photoacoustic signal of tumor region in different time was observed by live photoacoustic imager of small animals.So that it can determine the maximum tumor accumulation of melanin in 24 hours of injection.Three nanodroplet-mediated tumor therapy(days 0,4 and 9)significantly inhibited tumor growth,and the nanodroplet had good biological safety,which could be removed by metabolism without damaging normal tissue.In summary,the DOX-loaded and Melanin-cored phase-shift nanodroplet prepared by the work meet the requirements of nano-diagnostic agents on physical properties and characterization parameters.Furthermore,it can be used for photothermal/chemical combination therapy guided by ultrasound/photacoustic dual-modal imaging,which has laid a foundation for the application of nanodroplet in tumor treatment.