HN
N
NH
N
R
R
R
O
HN
N
N
N
N
COOH
COOH
HOOC
COOH
O
R =
OCH 2 COOH
25
3.3.10 Rhenium-186 and 188
188 Re generally exhibits the same chelation and radiolabeling chemistry as
99m Tc
[74]. Gamma ray-emitting
188 Re (t 1/2 = 16.9 h, b = 2.1 meV, c = 155 keV 15%) is
suitable for imaging and b emitting
186 Re (t 1/2 = 90 h, b = 1.07 meV,
c = 137 keV) offer potential for local radiotherapy [75]. A novel water-soluble
porphyrin, meso-tetrakis(3,4-bis(carboxymethyleneoxy)phenyl)porphyrin, 26 was
developed with dicarboxylic acid groups as aromatic substituents in the periphery
[76, 77]. This b emitting
186/188 Re compound was employed for biodistribution
studies in Swiss mice bearing fibrosarcomas and thymic lymphoma. Radionuclide
complex showed selectivity towards thymic lymphoma compared to fibrosarcoma.
Deng et al. reported a novel
188 Re-labeled meso-tetrakis(4-sulfophenyl) porphyrin
(TPPS4) 27 [78] as well as a meso-tetrakis(3,4-bis(carboxymethyleneoxy)phenyl)
porphyrin (T3,4CPP) 28 [79]. These were evaluated after intravenous injection in
tumor-bearing mice. Both compounds exhibited good tumor affinity.
3 Porphyrin and Phthalocyanine Radiolabeling
69