Upload
others
View
5
Download
0
Embed Size (px)
Citation preview
A bis(phosphonate) mono-amideanalogue of DOTA: a potential agent
for bone-targeting
Charles University, Prague Delft University of Technology
Bis(phosphonates)
PO3H2
PO3H2
R1
R2
OPO3H2
PO3H2
Pyrophosphate
Geminal bis(phosphonate)
Commercial name R1 R2
Aledronate
Clodronate
Etidronate
Ibadronate
Pamidronate
Risedronate
Tiludronate H
Cl Cl
OH
OH
OH
OH
OH
(CH3)3 NH2
CH3
(CH3)2 N(CH2)4
CH3
CH3
(CH3)2 NH2
CH2
N
S Cl
Charles University, Prague Delft University of Technology
Ligand BPAMD
Bis(phosphonic acid) group – bone targeting group
DOTA monoamide – chelating group for lanthanide(III) ions
N
N
N
NHOOC
HOOC
PO3H2
PO3H2HN
O
COOH
Charles University, Prague Delft University of Technology
Synthesis
HPO(OEt)2PO3Et2
PO3Et2Bn2NHC(OEt)3 HNBn2 ++
PO3Et2
PO3Et2H2N
N
N
N
Nt-BuOOC
t-BuOOC
PO3Et2
PO3Et2HN
O
COOt-Bu
PO3Et2
PO3Et2HN
O
Cl
N
N
N
NHOOC
HOOC
PO3H2
PO3H2HN
O
COOH
ClCH2COCl
t-Bu3DO3A
Charles University, Prague Delft University of Technology
Complexation of Ln(III) ions
The signals of excess of the free ligand are marked with asterisks
3 step process:
• pH 2–4: only phosphonates are coordinated
• pH 7–9: “out of cage” complex (A)
• After heating: DOTA-like complex (B)
Charles University, Prague Delft University of Technology
Ln-BPAMD complexes
The signals of excess of the free ligand are marked with asterisks
• All pendants coordinated
• One molecule of water in the inner coordination sphere
• Bis(phosphonic acid) group is not coordinated
• Phosphorus atoms are nonequivalent
Charles University, Prague Delft University of Technology
Relaxometry of Gb-BPAMD
a Powell, D. H.; Dhubhghaill, O. M. N.; Pubanz, D.; Helm, L.; Lebedev, Y. S.; Schlaepfer, W.; Merbach, A. E. J. Am. Chem. Soc. 1996, 118, 9333–9346b Aime, S.; Botta, M.; Garino, E.; Geninatti Crich, S.; Giovenzana, G.; Pagliarin, R.; Palmisano, G.; Sisti, M. Chem. Eur. J. 2000, 6, 2609–2617
• Slow water exchange
• High value of relaxivity
• Expected second hydration sphere
Charles University, Prague Delft University of Technology
LigandΔ2
[s–2/1019]τv[ps]
τr[ps]
τM[μs]
r1 (20 MHz)[s–1 mM–1]
BPAMD 3.7 ± 0.2 17 ± 1 88 ± 3 1.18 ± 0.6 5.3
DOTAa 1.6 11 77 0.244 4.8
DOTA-bis(methylphosphonic) monoamideb 1.8 21 97 1.6 6.2
Relaxometry of Gb-BPAMD
pH dependence of relaxivity
• Two steps in relaxivity: pH = 2–3 and 6–8
protonation of bis(phosphonic) acid group
• Increase in basic region:
prototropic exchange
5
5.5
6
6.5
7
7.5
2 4 6 8 10 12pH
r 1 [s
-1m
M-1
]
Charles University, Prague Delft University of Technology
8
10
12
14
16
18
20
0 1 2 3 4 5 6 7ratio Ca/Gd
17O
1/T
1ir1
05 [s-1
]
• 1:1 complex formation – logβ = 2.2
• 2 times shorter 17O T1ir increase of rotation correlation time
• Formation of 2+2 complexes – 8 member ring typical for phosphonate complexes
P
O
OR
O
P
O
O R
O
M
M
Interaction of Gd-BPAMD with Ca(II) ions
Charles University, Prague Delft University of Technology
0
4
8
12
16
0.01 0.1 1 10 100Larmor frequency[MHz]
r 1[s
-1m
M-1
]
without Ca(II)with Ca(II)
Interaction of Gd-BPAMD with Ca(II) ions
12
13
14
15
2.7 2.9 3.1 3.3 3.51000K/T
17O
ln(1
/T2i
r)
9
10
11
12
13
2.7 2.9 3.1 3.3 3.51000K/T
17O
ln(1
/T1i
r)
• Increase of relaxivity upon interaction with Ca(II) ions
• Unusually flat 17O temperature relaxation profiles
• Different complexing mode at higher temperature
Charles University, Prague Delft University of Technology
Sorption of Tb-BPAMD complexon the hydroxyapatite (HA)
0
10
20
30
40
50
0 0.5 1 1.5
c [mmol dm-3]
X [m
mol
g-1
]
K = X/(c.(Xm – X))
0
10
20
30
40
0 0.5 1 1.5c [mmol dm-3]
c/X
[g d
m-3
]
c/X = 1/KXm + c/Xm
c – equilibrium concentration; X – specific adsorbed amount; Xm – maximum adsorption capacity; K – affinity constant
• Fast and fully reversible sorption
• Maximum adsorption capacity Xm = 4.0×10-5 mol g-1 (specific surface of HA 53 m2g-1)indicates monomolecular layer formation
• Affinity constant K = 2.1×105 dm3mol-1
Charles University, Prague Delft University of Technology
Sorption of Tb-BPAMD complexon the hydroxyapatite (HA)
0
20
40
60
80
100
0.0 1.0 2.0 3.0 4.0 5.0
overall concentration of BPAMD [mmol dm-3]
activ
ity in
solu
tion
[%]
• Very strong interaction of Tb-BPAMD complex with HA surface
• Identical sorption abilities of free ligand BPAMD and its Tb(III) complex
• α-amido-bis(phosphonic acid) group – responsible for exceptional properties
bis(phosphonate)affinity constant
K ×103 [mol–1dm–3]HEDPa,b 3.3
MDPa,b 0.7
Tb-BPAMD 210a HEDP - 1-hydroxy-ethane-1,1-bis(phosphonic acid)
MDP – methanebis(phosphonic acid)b Claessens, R. A. M. J.; Kolar, I. Z. Langmuir 2000, 16, 1360–1367
Charles University, Prague Delft University of Technology
Relaxometry of the hydroxyapatite slurry
0
2
4
6
8
buffer Gd-BPAMD Gd-DTPA
1 H R
1 [s-1
]
SolutionSlurry
Solution
Solution
SlurrySuspension
Slurry
• Gd-BPAMD complex is fully adsorbed in the slurry
• Value of the relaxivity of adsorbed Gd-BPAMD comparable with that obtained for the slurry containing Gd-DTPA complex
• Same concentration of Gd-DTPA in the solution and in the slurry different relaxivities due to physicochemical conditions
Charles University, Prague Delft University of Technology
Relaxometry of the hydroxyapatite slurry
0
102030
40
5060
70
80
0.01 0.1 1 10 100
Proton Larmor frequency [MHz]
R1 [
s-1]
(Gd-BPAMD)-HA
0
102030
40
5060
70
80
0.01 0.1 1 10 100
Proton Larmor frequency [MHz]
R1 [
s-1]
(Gd-BPAMD)-HA
the diamagnetic contribution
0
102030
40
5060
70
80
0.01 0.1 1 10 100
Proton Larmor frequency [MHz]
R1 [
s-1]
(Gd-BPAMD)-HA
the paramagnetic contribution
the diamagnetic contribution
0
102030
40
5060
70
80
0.01 0.1 1 10 100
Proton Larmor frequency [MHz]
R1 [
s-1]
the paramagnetic contribution
Gd-BPAMD in ageous solution
• Superposition of a paramagnetic contribution from the complex and a diamagnetic contribution coming from HA
• Paramagnetic contribution shows a maximum at 10 – 20 MHz typical for Gd(III)complexes with slow rotation of the molecule
• 3-5 times higher milimolar relaxivity than the Gd-BPAMD complex in the solutionas result of the hindered rotation
Charles University, Prague Delft University of Technology
Conclusion
• new bis(phosphonate) containing DOTA monoamide
• three step lanthanide complexation
• DOTA-like Ln(III) complexes
• interaction with Ca(II) ions
• fast and strong adsorption of Ln(III)complexes on hydroxyapatite
• increase of rotation corelation time and relaxivity upon binding on hydroxyapatite
Charles University, Prague Delft University of Technology
Financial support• Marie Curie training site host fellowship (QLK5-CT-2000-60062) • Grant Agency of the Czech Republic (No. 203/03/0168) • COST D18 Action • EU Network of Excellence (NoE) “European Molecular Imaging Laboratory” (EMIL).
PragueIvan Lukeš
Petr Hermann
Jakub Rudovský
Jan Kotek
DelftJoop A. Peters
Hubert Th. Wolterbeek
Zvonimir I. Kolar
Kristina Djanashili
MonsRobert N. Muller
Luce Vander Elst
Sophie Laurent
Acknowledgement
Charles University, Prague Delft University of Technology