Radio-labeled Nanoparticles for Biomedical Imaging - Nanotechnology for Biomedical Imaging and Diagnostics - page 199

table 7.2 Nuclear characteristics of selected pet Radionuclides for Nanoparticles a

Radionuclide T 1/2 Decay (%) main photon KeV (%) production

68 ga

67.7 min β + (89) 511 (178.3)

68 ge/ 68 ga generator

eC (11)

18 f

109.7 min β + (96.7) 511 (193.5)

18 O (p, n) 18 f

eC (0.1)

64 Cu

12.7 h β + (17) 511 (34.8)

64 Ni (p, n) 64 Cu

eC (44)

76 br

16.2 h β + (55) 511 (109), 559 (74)

76 Se (p, n) 76 br

eC (45) 657 (15.9), 1854 (14.7)

76 Se (d, 2n) 76 br

86 Y

14.7 h β + (33) 511 (63.9), 1077 (82.5)

86 Sr (p, n) 86 Y

eC (66) 1115 (30.5), 627 (32.6)

89 Zr

3.3 d β + (23) 909 (100)

89 Y(p, n) 89 Zr

eC(77)

124 I

4.18 d β + (23) 511 (46), 603 (62.9)

124 Te (p, n) 124 I

eC (77) 723 (10.3)

124 Te (d, 2n) 124 I

a based in part on Ref. [41].

higher tumor accumulation (three- to six-fold increase) at 48 h p.i. Additionally,
embedding the egfR into the liposomes allowed for improved solubility of the
lipophilic nanoparticle, increased blood circulation, and bioavailability for tumor
targeting [91]. 18 f was also used for radiolabeling peg-liposomes by the SophT
method. In contrast to [ 18 f]fDg, biodistribution studies showed enhanced blood
retention and high ReS accumulation of [ 18 f]Step2-labeled peg-liposomes. Although
the brain tumor uptake was lower than with [ 18 f]fDg, the peT images obtained using
[ 18 f]Step2-labeled peg-liposomes were clearer due to lowered background as com-
pared with [ 18 f]fDg [92].

7.4.3 Radiolabeled iron oxides for pet imaging

magnetic nanoparticles, especially iron oxide nanoparticles, have also been widely
explored for peT and peT/mRI applications because of their inherently high T 2
relaxivity for enhanced contrast [93, 94]. To date, radiolabeling strategies resulting in
high labeling yield and specific activity have been established for labeling iron oxide
nanoparticles with positron emitters such as 64 Cu, 68 ga, and 124 I. The in vivo biodis-
tribution and targeting efficiency of these radiolabeled nanoparticles have been
studied in a variety of animal disease models [95-98]. After coating the iron oxide
surface with the carbohydrate dextran and conjugating with DTpA, 64 Cu-radiolabeled
iron oxide nanoparticles ( 64 Cu-TNp) were used to target macrophages in an apolipo-
protein e-deficient (apoe −/− ) mouse model of aneurysms. The high specific activity
(3.7 × 10 8 bq/mg fe of nanoparticle) ensured lower-dose administration (1.5 mg fe/kg
body weight) than that used in oncology clinical trials (2.6 mg fe/kg body weight)
and sensitive detection of nanoparticle accumulation in various organs. The in vivo
biodistribution of 64 Cu-TNp showed sufficient blood circulation ( t 1/2 ≥ 4 h) and major