Micro-PET study of 68Ga-HZ20 in the
rhACE2-intraperitoneal liver model
To investigate the targeting ability of the 68Ga-HZ20
probe in different tissues and organs, we chose to perform PET imaging
studies after in situ injection of different doses of rhACE2 in
the liver of KM mice. PET imaging showed clear probe uptake in the
liver, and the uptake was rhACE2 dose dependent (Fig. 4A, Fig. S7).
Compared with the control group, the rhACE2 injection group showed a
higher SUVmax value at the liver injection site, and the SUVmax obtained
15 min after probe injection was 0.43±0.02, 0.52±0.02 and 0.76±0.01,
respectively (Fig. 4B). Similarly, the target ratio of liver to muscle
in the rhACE2 injection group was significantly higher than that in the
blank control group, and the ratio in the 0.4 nmol rhACE2 injection
group was higher than that in the 0.2 nmol rhACE2 injection group and
reached the highest rate at 60 min, at 1.3±0.20, 2.54±0.27 and
3.95±0.52, respectively (Fig. 4C). After probe injection for 150 min,
the liver was sampled for γ counter measurement. Consistent with the PET
imaging results, % ID/g in the liver also depended on rhACE2 injection
doses, which were 0.24± 0.01, 0.32±0.01, and 0.37±0.02 (Fig. 4D). The
correlation analysis between rhACE2 and SUVmax showed the highest
correlation 60 min after injection of the probe, and the
R2 was 0.9994 (Fig. 4E). There was almost no
expression of ACE2 in the liver tissue, but rhACE2 injection
artificially increased the protein levels (Fig. 4F).