Published online Jun 15, 2000. doi: 10.3748/wjg.v6.i3.348
Revised: April 3, 2000
Accepted: April 28, 2000
Published online: June 15, 2000
AIM: To directly radiolabel an anti-hepatoma mAb fragment HAb18 F(ab')2 with 99mTc by stannous-reduced method, and assess the stability, biodistribution and radioimmun oimaging (R II).
METHODS: Immunoreactive fraction was determined according to Lin dmo's method. Ellman's reagent was used to determine the number of thiols in the reduced F(ab')2. Labeling efficiency and homogeneity were measured by paper chromatography, sodium dodecylsulphate polyacrylamide gel electrophoresis (SDS-PAGE) and autora diography. Challenge assay involved the incubation of aliquots of labeled antibody in ethylenediaminetetraacetate (EDTA) and L-cysteine (L-cys) solutions with different molar ratio at 37 °C for 1 h, respectively. Investigations in vivo utilized nude mice bearing human hepatocellular carcinoma (HHCC) xenografts with gamma camera imaging and tissue biodistribution studies at regular intervals.
RESULTS: The labeling procedure was finished within 1.5 h compared with the "pretinning" method which would take at least 21 h. In vitro studies demonstrated that the radiolabeled mAb fragment was homogen eous and retained its immunoreactivity. Challenge studies indicated that 99mTc-labeled HAb18 F(ab')2 in EDTA is more stable than in L-cys. Imaging and biodistribution showed a significant tumor uptake at 24 h post-injection of 99mTc-labeled HAb18 F(ab')2. The blood, kidney, liver and tumor uptakes at 24 h were 0.56 ± 0.09, 56.45 ± 11.36, 1.43 ± 0.27 and 6.57 ± 3.01 (%ID/g), respectively.
CONCLUSION: 99mTc-HAb18 F(ab')2 conjugate prepare d by this direct method appears to be an effective way to detect hepatoma in nude mice model.