Synthesis and characterization of TCPP-PEG NPs. a) A scheme showing TCPP molecule conjugated with different molecular weight PEG molecules for 64Cu2+ labeling. b) TEM images of TCPP-PEG2K, TCPP-PEG5K, TCPP-PEG10K, and TCPP-PEG30K nanoparticles. c) The hydrodynamic diameters (HDs) of TCPP-PEG nanoparticles with various molecule weights after being incubated in water solution. The HDs of the particles were 4.6 ± 1.4 nm for TCPP-PEG2K, 7.5 ± 2.2 nm for TCPP-PEG5K, 10.1 ± 2.8 nm for TCPP-PEG10K, and 17.3 ± 3.2 nm for TCPP-PEG30K nanoparticles.