An easy and effective method for synthesis and radiolabelling of risedronate as a model for bone imaging

Article abstract of DOI:10.1002/jlcr.3384

This study aimed to provide an easy method for synthesis of 1-hydroxy-2-(3-pyridyl) ethylidene bisphosphonic acid monosodium (sod. risedronate) with a high yield of 71%. The synthesized risedronate was labeled with technetium-99 m using two different reducing agents (SnCl₂.2H₂O and NaBH₄) where NaBH₄ gave stable complex and higher radiochemical yield more than SnCl₂.2H₂O. The results showed that, the radiochemical purity of ^99mTc(NaBH₄)-risedronate was 99.2 ± 0.6% and its stability was up to 6 h. Biodistribution study showed high uptake and long retention of ^99mTc(NaBH₄)-risedronate in bone starting from 15 min (29 ± 2.5% ID/organ) up to 4 h (35.1 ± 3.2 ID/organ) post injection. This research could introduce an easy and effective method for synthesis and labeling of risedrionate and affording a good tracer for bone imaging.

Full text of DOI:10.1002/jlcr.3384

Research article
Received 06 October 2015,
Revised 27 January 2016,
Accepted 05 February 2016
Published online 9 March 2016 in Wiley Online Library
(wileyonlinelibrary.com) DOI: 10.1002/jlcr.3384
An easy and effective method for synthesis
and radiolabelling of risedronate as a model
for bone imaging
a
a
a
a
M. A. Motaleb, * A. S. A. Adli, M. El-Tawoosy, M. H. Sanad, and
b
M. AbdAllah
This study aimed to provide an easy method for synthesis of 1-hydroxy-2-(3-pyridyl) ethylidene bisphosphonic acid
monosodium (sod. risedronate) with a high yield of 71%. The synthesized risedronate was labeled with technetium-99 m
using two different reducing agents (SnCl .2H O and NaBH ) where NaBH gave stable complex and higher radiochemical
2
2
4
4
9
9m
yield more than SnCl
2
.2H
2
O. The results showed that, the radiochemical purity of
Tc(NaBH )-risedronate was 99.2
4
99m
±
0.6% and its stability was up to 6 h. Biodistribution study showed high uptake and long retention of
4
Tc(NaBH )-
risedronate in bone starting from 15 min (29 ± 2.5% ID/organ) up to 4 h (35.1 ± 3.2 ID/organ) post injection. This research
could introduce an easy and effective method for synthesis and labeling of risedrionate and affording a good tracer for bone
imaging.
99m
Keywords: Bisphosphonate;
Tc; Synthesis; Risedronate; Imaging; Bone
Introduction
Risedronate and zoledronate are two of the most potent
19
antiresorptive BPs in several animal models because of the
nitrogen atom within the heterocyclic ring. Zoledronic acid,
one kind of the typical third-generation DPs, is currently the
most potent bisphosphonate. In preclinical models of bone
resorption, for example, zoledronate is at least 100 times more
Bisphosphonates (BPs) are an important class of compounds that
are used in the treatment of a variety of bone diseases, which are
associated with high bone resorption, such as metastatic bone
disease, Paget’s disease, and osteoporosis.
The efficient and early diagnosis of bone cancer in its early stages
allows the management of bone cancer patients with conventional
therapeutic strategies (chemotherapy, hormone therapy, external
beam radiation, and analgesics) and controlling bone pain or with
the systemic radiopharmaceutical therapy, which shows safe and
effective management of the advanced disease.
Technetium-99 m represents the radionuclide of choice in most
performed diagnostic nuclear medicine applications because of
its good physical properties: (t1/2 = 6.01 h, 140 keV γ-ray energy,
and very low abundance β-emission). Tc-bisphosphonate
derivatives are good bone targeting and used for bone imaging.
Technetium-99 m
ethylenediamine tetramethylene phosphonate, dicarboxy
propanediphosphonate, hydroxyethylidinediphosphonate,
potent than clodronate and pamidronate, and it is at least
20
1
,000 times more potent than etidronate.
A series of
zoledronate derivatives MIPrDP, MIBDP and MIPeDP have been
1
99m
prepared and successfully labeled with
Tc in a high labeling
yield (with colloid formation) and good in vitro stability, showing
2,3
high selective uptake in the skeletal system and rapid clearance
21
99m
14
from soft tissues. One of the previous study is
Tc-TEDP,
4,5
TEDP is a simple arm of bisphosphonate like hydroxyl ethylene
diphosphonate, and the only difference between TEDP and
hydroxyl ethylene diphosphonate is the replacement of (OH)
group by (SH) group; but in our study, we use one of the third
generation of bisphosphonate that contains heterocyclic ring
containing nitrogen in the ring (risedronate), which is more
potent than other generations of bisphosphonate; also, we use
99m
6
labeled
methylenediphosphonate,
hydroxyl methylene-diphosphonate, 1-thioethylidene-1,1-
disodium phosphonate (TEDP), 1-hydroxypropylidene-1, 1-
disodium phosphonate, and ethane-1-amino-1, 1-diphosphonic
acid represent radiopharmaceuticals of choice for bone
scintigraphy especially in bone metastases, Paget’s disease, and
two reducing agent (SnCl
problems that appear by using SnCl
and we conclude that NaBH is more effective and easier than
O. Stannous chloride is used for reduction of sodium
2
.2H
2
O and NaBH
4
) to overcome the
2
.2H O as a reducing agent,
2
4
2 2
SnCl .2H
7
–16
osteoporosis.
The main
diphosphonates (DPs) is an interval of 2–6 h is needed between
99m
disadvantage
of
these
Tc-labeled
a
Labeled Compounds Department, Hot Laboratories Center, Atomic Energy
Authority, P.O. Box 13759Cairo, Egypt
14,17
injection and bone imaging.
Shortening this interval would
b
decrease the burden on patients in terms of the total length of
the examination and the dose of radiation absorbed. To enable
imaging at an earlier time after injection, a radiopharmaceutical
Faculty of Science, Department of Chemistry, Zagazig University, Zagazig, Egypt
*
Correspondence to: M. A. Motaleb, Labeled Compounds Department, Hot
Laboratories Center, Atomic Energy Authority, P.O. Box 13759, Cairo, Egypt.
E-mail: mamotaleb10@yahoo.com
18
with higher affinity for bone is required correspondingly.
J. Label Compd. Radiopharm 2016, 59 157–163
Copyright © 2016 John Wiley & Sons, Ltd.

M. A. Motaleb et al.
Figure 1. Sod. risedronate.
9
9m
Figure 3.
Tc-BPs, a proposed structure.
9
9m
ꢀ
4
pertechnetate (Na TcO ) to obtain lower valency state of Synthesis of risedronic acid monosodium salt
99m
Tc, but during labeling by this method, radiocolloids are
generated as main impurities.
This article reports one-pot method for synthesis of sodium
risedronate (Figure 1) with a high yield and also reports a rapid
and effective method for radiolabeling of risedronate by
using sodium borohydride as a reducing agent. Sodium
borohydride was used for reduction of
lower oxidation state, and subsequent complexation was done
with risedronate molecules without forming radiocolloid. This
22,23
Monosodium salt was obtained using the aforementioned procedure
with 3-pyridineacetonitrile (100.0 g, 0.847 mol), but the pH was adjusted
to 4.3 with 30% sodium hydroxide solution before diluting with
methanol (1500 mL). The resulting product was filtered and dried to yield
risedronic acid monosodium salt (210 g, 71%) as a white crystalline
hemipentahydrate solid (Figure 2).
9
9m
Tc
99m
Tc(VII) ions to the
9
9m
Preparation of
Tc-risedrinate complex
99m
Preparation of
Tc(Sn)-risedronate complex
article uses the two reducing agents (SnCl
2
and NaBH
Tc and compare between
them in terms of radiochemical yield and stability of the formed was separately transferred to evacuated penicillin vials. Exactly 1 μg of
4
) for
99m
radiolabeling of risedronate with
2
Exactly 5 mg of risedronate, dissolved in 1 mL N -purged distilled water,
complex.
Sn(II) was added to each vial along with different amounts of 0.1 N NaOH
or 0.1 N HCl to adjust pH in a range of 3–7. Then, 100 μL of freshly eluted
9
9m
ꢀ
4
TcO (~200 MBq) was added to each vial. The reaction mixtures were
Experimental
left at room temperature for 30 min. The same procedure was repeated
with varying Sn(II) amounts (0.5–5 μg), varying risedronate amounts (1–
20 mg), and different reaction times (5–360 min).
All of the chemical reagents were of analytical reagent grade; Carbon-13
nuclear magnetic resonance ( C NMR, Jeol JNM-Ex- 67.8 MHz FT NMR
system using tetramethylsilane as an internal standard; Jeol Ltd,
Hertfordshire, UK), and proton nuclear magnetic resonance ( H NMR, Jeol
EX-270 MHz FT using tetramethylsilane as an internal standard; Jeol Ltd,
NRC, Cairo, Egypt) were used for the characterization of the synthesized
13
99m
Preparation of
Tc(NaBH )-risedronate complex
4
1
Exactly 0.5 mg of risedronate, dissolved in 1 mL distilled water, was
separately transferred to penicillin vials. Exactly 5 mg of NaBH was
4
9
9m
ꢀ
4
from
added to each vial along with different amounts of 0.1 N NaOH or 0.1 N
HCl to adjust pH in a range of 3–13. Then, 100 μL of freshly eluted
sodium risedronate. Technetium-99 m was eluted as
TcO
9
9m
99m
Mo/ Tc generator (radionuclidic purity: 99.99 %; radiochemical
9
9m
ꢀ
4
TcO
left at room temperature for 15 min. The same procedure was repeated
with varying NaBH amounts (2–20 μg), varying risedronate amounts
0.1–5 mg), and different reaction times (5–360 min).
Bisphosphonate compounds are strong chelating agents, the reaction
of bisphosphonate compounds with technetium gave only three species
(~200 MBq) was added to each vial. The reaction mixtures were
purity: 99.99 %; Activity: 1 Ci; Elutec, Brussels, Belgium). Albino mice, each
of 20–25 g, were used for the biological distribution study. A NaI(Tl) γ-ray
scintillation counter (Scaler Ratemeter SR7, Nuclear Enterprises,
Edinburgh, UK) was used for the measurement of γ-ray radioactivity.
4
(
9
9m
ꢀ
99m
Synthesis of 1-hydroxy-2-(3-pyridyl)ethylidenebisphosphonic (free pertechnetate
TCO
4
, colloid, and
Tc-complex) where the
acid (risedronic acid)
structure of the complex is formed from two molecules of
bisphosphonate and one technetium atom like all previously reported
2
1,24–28
Aqueous methanesulfonic acid (85%, 432.5 mL) was added to
bisphosphonates
as shown in Figure 3.
3-pyridineacetonitrile (100.0 g, 0.847 mol) and heated to 98–100 °C for 8 h
(
Figure 2), then cooled the reaction temperature to 65 °C, and phosphorus
99m
Radiochemical yield of
Tc-risedronate complex
trichloride (396.0 g, 2.880 mol) was added over 25 min. After 5 h of stirring
at 65–70 °C, the reaction temperature was cooled to 30 °C, and pre-cooled
water (1000 mL) was added very slowly in 30 min. The reaction temperature
was heated to 98 °C. After 15 h of stirring, the temperature was cooled to
Paper chromatography analysis
9
9m
The percent labeling yield of the labeled
Tc-risedronate complex was
determined using ascending paper chromatographic technique. Strips of
Whatman No.1 paper chromatography (Whatman International Ltd,
Maidstone, Kent, UK) of 13 cm long and 1 cm wide were marked at a
distance of 2 cm from the lower end and lined into sections 1 cm each
up to 10 cm.
5
0 °C, and methanol (1500 mL) was added. After 2 h of stirring at 5–10 °C,
the product was collected by filtration and dried to give risedronic acid
201.5 g, 79%) as a white monohydrate solid.
(
9
9m
99m
In case of
Tc(Sn)-risedronate complex, a spot from
Tc(Sn)-
risedronate complex solution was applied using hypodermic syringe,
and then, the strip was developed in an ascending manner in a closed
jar filled with N gas to prevent oxidation of the labeled phosphonate
2
spot. The developing solvents were acetone for developing one paper
and saline for developing a second paper strip.
9
9m
99m
In case of
Tc(NaBH
4
)-risedronate complex, a spot from
Tc
(
NaBH )-risedronate complex solution was applied using hypodermic
4
syringe, and then, the strip was developed in an ascending manner in
a jar using only acetone as a developing solvent. After complete
development, the strips were dried and cut into fragments 1 cm each.
Then, the sections were counted in a NaI(Tl) γ-ray scintillation counter.
Figure 2. Synthesis of risedronic acid monosodium salt hemipentahydrate.
www.jlcr.org
Copyright © 2016 John Wiley & Sons, Ltd.
J. Label Compd. Radiopharm 2016, 59 157–163

M. A. Motaleb et al.
Re(NaBH
4
)-risedronate complexwas prepared by the same method that
Tc(NaBH )-risedronate and was examined using HPLC (Figure 5) with
the same separation condition of
9
9m
of
4
9
9m
4
Tc(NaBH )-risedronate. The HPLC
chromatogram of Re-risedronate showed one peak at retention time
ꢀ
1
0.1 min for Re-risedronate and another beak at 4.2 for ReO
4
. Technetium
complex was washed out with longer retention time than the
corresponding rhenium complex, because technetium complex was more
hydrophobic than the corresponding rhenium complex, because of the
2
9
different atomic radii of technetium and rhenium. Similar unmatched
3
0
retention times have also been observed previously.
Biodistribution study
Experiments were performed using the procedure that was approved by
the Animal Ethics Committee and was in accordance with the guidelines
set out by the Egyptian Atomic Energy Authority. Male Albino Swiss mice
weighing 20–25 g were used.
In-vivo biodistribution studies were carried out in five groups of Albino
mice where each animal was injected in the tail vein with 0.2 mL solution
9
9m
containing 5–10 kBq of
Tc-risedronate. The mice were put in metabolic
cagesfortherequiredtime. Themiceweresacrificedbycervicaldislocation
in groups at various time intervals after injection, and the organs or tissues
of interest were removed, weighted and counted. The weights of blood,
bone, and muscles were assumed to be 7, 10, and 40% of the total body
9
9m
Figure 4. Radiochromatogram of
radioactivity.
4
Tc(NaBH )-risedronate complex, UV
3
1
weight, respectively.
To correct for physical decay and to calculate uptake of the radiolabel
The radiochemical yield was further confirmed by HPLC. The sample compound in each tissue sample as a fraction of the injected dose,
High performance liquid chromatography analysis
volume was 20 μL injected into the column (C18 (4.6 × 150 mm, 5 mm,
aliquots of the injected dose were counted simultaneously. The results
Make: Thermosil), and UV detection of 262 nm at ambient temperature).
were expressed as percentage injected dose per gram of tissue or organ
The column was eluted with mobile-phase mixture of acetonitrile/ (% ID/g or organ).
methanol/H2O mixture in ratio 30:30:40, and the flow rate was adjusted
to 1/2 mL/min, then fractions of 1/2 mL were collected separately up to
Results and discussion
60 fractions and counted in a well-type NaI(Tl) detector connected to a
single-channel analyzer.
The HPLC radiochromatogram of
Characterization of the synthesized 1-hydroxy-2-(2pyridyl)
ethylidenebis-phosphonic acid monosodium (sod.
risedronate)
9
9m
4
Tc(NaBH )-risedronate. Two
99m
ꢀ
4
peaks appeared at retention times 5 and 11 min for free
TcO
and
9
9m
Tc(NaBH
9.2 ± 0.6% radiochemical yield of
4
)-risedronate, respectively. The radiochromatogram showed
99m
9
Tc(NaBH
4
)-risedronate complex The chemical structure of sod. risedronate ( molecular formula,
coinciding with the results of the analysis using ascending paper
chromatography as shown in Figure 4.
C
7
H
10NO
7
P
2
Na. 2.5 H
2
O) was confirmed by the following: IR
ꢀ1
(
[
KBr, cm ) 3440, 3007, 2933, 1642, 1254, 1074; MS (m/z): 306
M+ H] ; H NMR (D O) δ 2.45 (OH, alcohol), 4.85 (t, 2H,
2
+
1
J = 12.1 Hz), 7.45 (m, 1H), 8.20 (dd, 1H, J = 8.2, 5.5Hz), 8.50 (d, 1H,
13
J = 7.2Hz), 8.70 (dd, 1H, J = 9.1, 8.2 Hz); C-NMR (300 MHz, D
2
O) δ
9
1
1
(CH aliphatic), 39(C, aliphatic), 122(CH, aromatic in position 5),
2
33(CH aromatic in position 4), 139(C, aromatic in position 3),
46(CH aromatic in position 6), 148(CH aromatic in position 2).;
3
1
P NMR (D O) δ 17.1.
2
9
9m
Radiolabeling of
Tc-risedronate complex
Using ascending paper chromatographic technique, the
99m
radiochemicalpurityoftheformed
Tc(Sn)-risedronatecomplex
was checked by using acetone as a developing solvent where free
9
9m
ꢀ
4
TcO
wasmovedwiththesolventfront(R
f
= 1)whileotherspecies
99m
99m
(reduced hydrolyzed- Tc colloid and
Tc(Sn)-risedronate
complex) remained at the point of spotting. The percentage of the
99m
reducedhydrolyzed- Tcwascalculatedusingsalineasadeveloping
99m
solvent where reduced hydrolyzed- Tc colloid remained at the
9
9m
ꢀ
4
99m
origin(R = 0),whilefree TcO and Tc(Sn)-risedronatecomplex
f
99m
migratetothetopofthepaper.Thepercentof Tc(Sn)-risedronate
complexweredeterminedasfollows:
À% free99m
TcO4 þ % reduced hydrolyzed Tc colloid :
Á
ꢀ
99m
Labeling yield ¼ 100 ꢀ
9m
9
In case of
Tc(NaBH )-risedronate complex, only one
4
99m
ꢀ
Figure 5. UV absorbance of Re-risedronate complex.
developing solvent is used (acetone). Free
TcO migrate to
4
J. Label Compd. Radiopharm 2016, 59 157–163
Copyright © 2016 John Wiley & Sons, Ltd.
www.jlcr.org

M. A. Motaleb et al.
9
9m
99m
Figure 6. Radiochemical yield of
Tc(Sn)-risedronate as a function of pH.
Figure 8. Radiochemical yield of
Tc(Sn)-risedronate as a function of Sn(II)
Reaction conditions: 1 μg of Sn(II), 5 mg sod.risedronate, 100 μL(~200 MBq) of
amount. Reaction conditions: 5 mg sod.risedronate, pH 4, 100 μL(~200 MBq) of
9
9m
ꢀ
99m
ꢀ
TcO
4
solution, room temperature, 30 min.
TcO
4
solution, room temperature, 30 min.
99m
the top of the paper, while
Tc(NaBH ) risedronate complex Effect of reducing agent content
4
still down (there is no colloid formed).
Stannous chloride is the most commonly used reducing agent
9
9m
Effect of pH of the reaction medium
in acidic medium in preparations of most
Tc-labeled
3
2,33
compounds.
Although stannous chloride is the most
Figures 6 and 7 clearly show the effect of pH on radiochemical
commonly used reducing agent in preparations of most
9
9m
99m
yield of both
complexes.
In case of
Tc(Sn)-risedronate and
4
Tc(NaBH )-risedronate
99m
Tc-labeled compounds, but radiolabelling by SnCl2
method generates radiocolloids, the biodistribution of desired
molecule is affected by these radiocolloids. We have to
optimize the amount of stannous salts and pH of the reaction
for getting maximum labelling efficiency. Some time, we have
to pass the mixture of compounds through a column to obtain
9
9m
Tc(Sn)-risedronate complex, at pH below or
above the optimum pH of the reaction medium, the
radiochemical yield was low because of the formation of
9
9m
RH- Tc, which was the main radiochemical impurity; the
optimum pH was 4, which give maximum radiochemical yield
of 84.5 ± 3.5%.
34
radiocolloids free-labeled compound. These processes are
9
9m
time consuming, so sodium borohydride is used as a reducing
agent to avoid the aforementioned problems. Boric acid is
generated as a by-product when sodium borohydride is used
In case of
Tc(NaBH )-risedronate complex (Figure 7) (there
4
is no colloid formation), the radiochemical yield increased with
increasing of the pH; where at pH 3, the radiochemical yield
was low (8.9 ± 0.2%), while at pH 9, the maximum radiochemical
yield (99.2 ± 0.6%) was obtained; where at this pH value, the
risedronate combined all the reduced technetium. When the
pH value was increased, above pH 9, the percent labeling yield
was slightly decreased.
35
in radiolabelling purpose, which act as stabilizing agent.
Sodium borohydride (NaBH
medicine by Suberamanian and McAfee, 1969. The influence
of Sn(II) content on the percent labeling yield of the
4
) was introduced into nuclear
36
99m
Tc
(
Sn)-risedronate complex was investigated in a range of 0.5–
5
μg as shown in Figure 8. Using too little stannous chloride
9
9m
ꢀ
4
may lead to incomplete reduction of free
unreliable yield of the
TcO , and hence,
9
9m
Tc(Sn)-risedronate complex was
obtained because of the low Sn(II) content, which was
9
9m
ꢀ
4
insufficient for the complete reduction of the free
giving rise to high percentage of the free
TcO
,
9
9m
ꢀ
TcO
4
. By
increasing the Sn(II) content from 0.5 to 1 μg, the labeling
yield increased from 82.3 to 84.5 ± 3.5%. By increasing Sn(II)
greater than 1 μg, the labeling yield was decreased again
because of formation of Tc-Sn-colloid. So, the optimum
amount of Sn(II) content for the formation of maximum
9
9m
Tc(Sn)-risedronate complex (84.5 ± 3.5) was 1 μg.
Effect of NaBH4 on the percent labeling yield of
NaBH )-risedronate complex was shown in Figure 9; 1 mg
9
9m
Tc
(
4
9
9m
ꢀ
4
NaBH4 is insufficient to complete reduction of
form
TcO to
9
9m
99m
ꢀ
4
Tc-complex, so the percentage of
TcO was high
and equal to 54.7 ± 0.4%. By increasing the amount of NaBH4,
the labeling yield was increased, where the maximum labeling
9
9m
Figure 7. Radiochemical yield of
Tc(NaBH
, 0.5 mg sod.risedronate, 100 μL(~200 MBq) of
solution, room temperature, 15 min.
4
)-risedronate as a function of pH.
yield was achieved at 5 mg NaBH . Increasing the NaBH4
4
Reaction conditions: 5 mg NaBH
4
9
9m
ꢀ
greater than 5 mg, the labeling yield was slightly decreased.
TcO
4
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Copyright © 2016 John Wiley & Sons, Ltd.
J. Label Compd. Radiopharm 2016, 59 157–163

M. A. Motaleb et al.
9
9m
9
9m
Figure 12. Radiochemical yield of
Tc(Sn)-risedronate as a function of time.
Figure 9. Radiochemical yield of
4 4
Tc(NaBH )-risedronate as a function of NaBH
Reaction conditions: 1 μg of Sn(II), 5 mg sod.risedronate, pH 9, 100 μL(~200 MBq)
amount. Reaction conditions: 0.5 mg sod.risedronate, pH 9, 100 μL(~200 MBq) of
99m
TcO
ꢀ
9
9m
TcO
ꢀ
of
4
solution, room temperature.
4
solution, room temperature, 15 min.
Effect of sodium risedronate content
The effect of sodium risedronate content was studied in a range
of 0.1–20 mg as shown in Figures 10 and 11. Low percent
radiochemical yield (70.55 ± 2.5%) was obtained at low
risedronate amount (1 mg) where the labeling yield was
increased with increasing the risedronate amount until it
reaching the highest yield of 84.5 ± 3.5% at 5 mg of risedronate,
when Sn(II) is used as a reducing agent (Figure 10). Increasing
the risedronate amount more than 10 mg, the labeling yield
was slightly decreased.
99m
But in case of
4
Tc(NaBH )-risedronate complex (Figure 11),
the maximum radiochemical yield (99.2 ± 0.6%) was obtained
at 0.5 mg risedronate, At low risedronate amount (0.1 mg), the
labeling yield was small and equal to 72.8 ± 0.5% because of
the amount of risedronate was insufficient to form complex with
99m
ꢀ
all of the formed reduced technetium, so the percent of
TcO
4
was high and equal to 27.2 ± 0.3%. The radiochemical yield was
increased with increasing the risedronate amount where a
maximum labeling yield of 99.2 ± 0.6% was obtained at 0.5 mg
risedronate. By increasing the risedronate amount above
9
9m
Figure 10. Radiochemical yield of
Tc(Sn)-risedronate as a function of sod.
Risedronate amount. Reaction conditions: 1 μg of Sn(II), pH4, 100 μL(~200 MBq)
9
9m
TcO
ꢀ
of
4
solution, room temperature, 30 min.
9
9m
99m
Figure 11. Radiochemical yield of
Tc(NaBH
4
)-risedronate as a function of sod.
, pH 9, 100 μL
Figure 13. Radiochemical yield of
Tc(NaBH
4
)-risedronate as a function of time.
risedronatesod.risedronate. Reaction conditions: 5 mg of NaBH
4
Reaction conditions: 5 mg of NaBH
4
,
0.5 mg sod.risedronate, pH 9, 100 μL
9
9m
TcO
ꢀ
99m
TcO
ꢀ
(
~200 MBq) of
4
solution, room temperature, 15 min.
(~200 MBq) of
4
solution, room temperature.
J. Label Compd. Radiopharm 2016, 59 157–163
Copyright © 2016 John Wiley & Sons, Ltd.
www.jlcr.org

M. A. Motaleb et al.
99m
Table 1. Biological distribution of
Tc-risedronate complex in mice as a function of time
Organs
% Injected dose/organ and body fluid at different time post injection (min)
and body
Fluids
15
30
60
120
240
Bone
29.2 ± 2.5
14.25 ± 1.2
12.65 ± 1
30.25 ± 3
8.05 ± 0.9
7.23 ± 0.8
1.75 ± 0.09
2.55 ± 0.12
1.83 ± 0.15
0.8 ± 0.07
0.92 ± 0.1
1.1 ± 0.09
0.39 ± 0.03
45.18 ± 4
33.85 ± 3.2
3.56 ± 0.4
3.67 ± 0.3
1.26 ± 0.1
1.73 ± 0.15
1.51 ± 0.12
0.52 ± 0.03
0.82 ± 0.07
0.86 ± 0.08
0.23 ± 0.02
52.01 ± 4.1
34.21 ± 3.1
2.24 ± 0.21
2.2 ± 0.22
0.85 ± 0.07
1.13 ± 0.1
35.1 ± 3.2
2.11 ± 0.2
1.23 ± 0.1
0.62 ± 0.05
1.1 ± 0.1
1.09 ± 0.09
0.43 ± 0.02
0.8 ± 0.05
0.74 ± 0.05
0.06 ± 0.01
56.67 ± 4.5
Muscles
Kidneys
Blood
Intestine
Liver
Stomach
Lungs
Spleen
Heart
9.45 ± 0.95
3.22 ± 0.3
2.02 ± 0.25
0.89 ± 0.1
0.94 ± 0.1
1.54 ± 0.14
0.41 ± 0.05
25.36 ± 2.7
1.17 ± 0.1
0.45 ± 0.02
0.82 ± 0.05
0.73 ± 0.05
0.096 ± 0.01
56.15 ± 3.9
Urine
0
.5 mg, the labeling yield remained nearly stable at maximum technetium-99 m using NaBH4 as a reducing agent to give
labeling yield.
high radiochemical yield of 99.2 ± 0.6%, which was higher
than the method used Sn(II) as a reducing agent that gives a
radiochemical yield of 84.5 ± 3.5% because of forming
Effect of reaction time and in vitro stability
The influence of the reaction time on the percent radiochemical radiocolloid impurities, so NaBH is more effective and easier
4
9
9m
99m
yield of
Tc-risedronate complex (Figures 12 and 13) was than SnCl .2H O.
4
Tc(NaBH )-risedronate showed high and
2
2
investigated as a function of time from 5 min up to 6 h. It was long uptake of the radioactivity in bone starting from 15 min
found that the rate of complexation was relatively fast in case (29.2 ± 2.5 ID/g) to 4 h (35.1 ± 3.2 ID/g) showing the high
9
9m
of NaBH
4
, and high percent radiochemical yield was achieved affinity of
4
Tc(NaBH )-risedronate complex to the bone, so
9
9m
(99.2 ± 0.6%) within about 15 min and then remained around
Tc(NaBH )-risedronate could be used as
a
good
4
maximum value up to 6 h. Figure 13
radiopharmaceutical for skeletal imaging.
In case of Sn(II) method, the reaction starts slowly where the
labeling yield was low (80.9 ± 2.9%) at 5 min and labeling yield
was increased with time till reach its maximum labeling yield at References
99m
3
0 min. The formed
Tc-risedronate complex has high in vitro
[
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99m
Table 1 shows the biodistribution of
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Tc-risedronate
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