Binding studies of [(18)F]-fluoride and polyphosphonates radiolabelled with [(111)In], [(99m)Tc], [(153)Sm], and [(188)Re] on bone compartments: a new model for the pre vivo evaluation of bone seekers?
BACKGROUND
Although the first polyphosphonates were already introduced in the early 1970s, mechanisms involved in uptake still remain speculative. The present work aimed to establish a new method to rate the influence of various factors on the uptake and to evaluate new bone-seekers on these bone compartments.


METHODS
Radioactive-labelled diphosphonates and [(18)F]-fluoride were added to a vial containing hydroxyapatite (HA), collagen, or amorphous calcium phosphate (ACP) in 3 ml of Hanks' Balanced Salt Solution (HBSS). After incubation, these suspensions were filtered, the radioactivity was measured in the gamma-counter, and the percentage of irreversibly bound radioactivity was calculated.


RESULTS
Kinetic experiments revealed uptake increase over time for [(99m)Tc]-MDP and [(18)F]-fluoride on various amounts of matrix. After 120 min, static studies on HA yielded: [(99m)Tc]-EDTMP < [(188)Re]-/Re-EDTMP < [(99m)Tc]-/11 microl Re-EDTMP < [(99m)Tc]-/In-EDTMP < [(99m)Tc]-/15 microl Re-EDTMP < nca [(188)Re]-EDTMP < [(111)In]-/Re-EDTMP < [(111)In]-EDTMP < [(111)In]-/In-EDTMP < [(99m)Tc]-DPD < [(99m)Tc]-/80 microl Re-EDTMP < [(99m)Tc]-EDTMP "boiled" < [(99m)Tc]-/150 microl Re-EDTMP < [(153)Sm]-EDTMP < [(99m)Tc]-/11 microl Re-EDTMP "boiled" < [(18)F]-ions < [(99m)Tc]-MDP. Collagen showed very low uptake. Reincubation experiments suggest that bone tracers are irreversibly bound.


CONCLUSIONS
The presented method is rapid and feasible to examine the adsorption of radioactive-labelled substances on bone components. Correlations between our findings and published in vivo data support the application as a simple model.
Mitterhauser
Markus
M
Department of Nuclear Medicine, Medical University of Vienna, Vienna, Austria. markus.mitterhauser@akh-wien.ac.at
Tögel
Stefan
S
Wadsak
Wolfgang
W
Mien
Leonhard-Key
LK
Eidherr
Harald
H
Wiesner
Karoline
K
Viernstein
Helmut
H
Kletter
Kurt
K
Dudczak
Robert
R
D001859:Bone Neoplasms / Q000556:secondary*; D005459:Fluorides / Q000378:metabolism*; D006801:Humans; D008954:Models, Biological; D063065:Organophosphonates / Q000378:metabolism*; D011868:Radioisotopes / Q000378:metabolism*
D063065:Organophosphonates; D011868:Radioisotopes; D005459:Fluorides