File Name : figure s1.tif

Caption : figure s1. epr spectrum of prepared melanin nanoparticles. 

File Name : figure s2.tif

Caption : figure s2. t1-weighted images of melanin nanoparticles with different concentration. 

File Name : figure s3.tif

Caption : figure s3. tem images of mnp-peg-gd with different gd3+:mnp mass ratio: (a) gd3+:mnp=0.05:1, (b) gd3+:mnp=0.1:1, (c) gd3+:mnp=0.5:1, (d) gd3+:mnp=1:1, (e) gd3+:mnp=3:1 and (f) gd3+:mnp=5:1.

File Name : figure s4.tif

Caption : figure s4. relative viabilities of rat h9c2 cardiomyocytes incubated with mnp-peg-m nanoparticles at various concentrations for 24 h by cck-8 assay. 

File Name : figure s5.tif

Caption : figure s5. t1-weighted mri axial and coronal images of balb/c mice at 4 h after intravenously injected mnp-peg-m at 1 mg / per mouse performed on a 3.0 t clinical mri scanning. the bladders were indicated by yellow arrows.