Phytochlorin [21H, 23H-Porphine-7-propanoicacid,
3-carboxy-5-(carboxymethyl)13-ethenyl-18-ethyl-7,
8-dihydro-2,8,12,17-tetramethyl-,(7S,8S)] was labeled with
99mTc and the factors affecting the labeling yield of 99mTcphytochlorin
complex were studied in details. At pH 10,
99mTc-phytochlorin complex was obtained with a high
radiochemical yield of 98.4 ± 0.6 % by adding 99mTc to
100 mg phytochlorin in the presence of 75 lg SnCl22H2O
after 30 min reaction time. The molecular modeling study
showed that the structure of 99mTc-phytochlorin complex
presents nearly linear HO–Tc–OH unit with an angle of
179.27 and a coplanar Tc(N1N2N3N4) unit. Biodistribution
of 99mTc-phytochlorin complex in tumor bearing mice showed
high T/NT ratio (T/NT = 3.65 at 90 min post injection). This
preclinical study showed that 99mTc-phytochlorin complex
is a potential selective radiotracer for solid tumor imaging
and afford it as a new radiopharmaceutical suitable to
proceed through the clinical trials for tumor imaging.