Melanin nanoparticle(MNP)was modified by polyethylene glycols(PEG),and the resulting compound(PEG-MNP)was obtained.The 68Ga labeled PEG-MNP was prepared by chelating radioactive 68Ga3+ions with high labeling yield(95.6％±1.9％)and radiochemical purity(＞95％).The stability of the labeling compound as well.Then 68Ga-PEG-MNP for simulating PM2.5 particles(particulate matter 2.5,size＜2.5 μm)was obtained through nebuliza-tion.After inhaling the nebulized particles,whole-body positron emission tomography(PET)in mice was performed.It revealed that nebulized 68Ga-PEG-MNP diffused from the trachea to the bilateral lobe area of the lungs and retained in the lungs.Quantification of PET images showed that the uptakes of the trachea and lung were(7.20± 2.44)％g-1,(4.46±1.04)％g-1,(4.91±2.48)％g-1,(4.71±2.39)％g-1,(3.34±1.14)％·g-1,and(17.90±3.75)％g-1,(18.10±4.52)％g-1,(19.49±6.11)％g-1,(19.19±2.83)％g-1,(20.87±2.40)％·g-1 at 0 min,30 min,1 h,2 h,4 h after administration of the nebulized 68Ga-PEG-MNP,respectively.The results were highly consistent with the findings of ex-vivo radiographic autoradiography.
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