Synthesis of hexa aza cages, SarAr-NCS and AmBaSar and a study of their metal complexation, conjugation to nanomaterials and proteins for application in radioimaging and therapy

Abstract

A novel hexa aza cage, N(1)-(4-isothiocyanatobenzyl)-3,6,10,13,16,19-hexaazabicyclo[6.6.6]icosane-1,8-diamine (SarAr-NCS) was synthesized in good yield and characterized by (1)H NMR and electrospray mass spectrometry. A new method for the synthesis of the related N(1)-(4-carboxybenzyl)-3,6,10,13,16,19-hexaazabicyclo[6.6.6]icosane-1,8-diamine (AmBaSar) using the p-carboxybenzaldehyde is reported. The complexation of Cu(2+), Co(2+) and Zn(2+) by the two ligands over a range of pHs was found to be similar to the parent derivative SarAr. SarAr-NCS was conjugated to both silica particles (≈90 nm diam.) and the model B72.3 murine antibody. The SarAr-NCSN-silica particles were radiolabeled with Cu(2+) doped (64)Cu and the number of ligands conjugated was calculated to be an average of 7020 ligands per particle. Conjugation of SarAr-NCS to the B72.3 antibody was optimized over a range of conditions. The SarAr-NCSN-B72.3 conjugate was stored in buffer and as a lyophilized powder at 4 °C over 38 days. Its radiolabeling efficiency, stability and immunoreactivity were maintained. The development of a high yielding synthesis of SarAr-NCS should provide an entry point for a wide range of Cu and Zn radiometal PET imaging agents and potentially radiotherapeutic agents with (67)Cu.

Bifunctional 64Cu-labelled macrobicyclic cage amine isothiocyanates for immuno-positron emission tomography

“…15 A modified version of SarAr featuring a phenylisothiocyanate functional group (SarAr-NCS) has been used to introduce a cage amine ligand to the B72.3 antibody and to silica particles. 16 Isothio-cyanates react with nucleophilic primary and secondary amines. 17,18 The secondary amines of (NH 2 ) 2 sar are nucleophilic and react with alkyl halides and aldehydes in preference to the primary amines.…”

Radiometals: towards a new success story in nuclear imaging?

“…This barrier has recently been challenged by E. Mume et al, who developed a high yielding synthesis method. 79 Two new cyclam ( pycup2Bn) 80 and cyclen (L 1 ) 81 crossbridged macrocycles (Fig. 5) form stable complexes with Cu(II) (log K CuL = 23.25 for L 1 ) and demonstrate very good kinetic inertness towards acid-assisted dissociation (t 1/2 = 20.3 h in 5 M HCl at 90 °C for Cu-pycup2Bn and t 1/2 = 30.8 d in 12 M HCl at 90 °C for L 1 ).…”

“…65 Additional information can also be found in more recent reviews. 41,118,126 Activated carboxylic acid with succinimidyl ester (NHS), 84,127 isothiocyanate, [128][129][130] N-hydroxysulfosuccinimidyl ester (SNHS), 131 tetrafluorophenol (TFP) 132 or peptide coupling reagents such as EDCI, HATU, HOBt etc. can easily react with primary amines to form a stable peptidic bond (Fig.…”

Synthesis, complex stability and small animal PET imaging of a novel 64Cu-labelled cryptand molecule

“…1), which form robust complexes (cryptates) with [ 64 Cu]Cu 2+ that are highly resistant towards transchelation. [22][23][24] While the Sar-based cryptands offer excellent Cu 2+ chelating properties, the challenging synthetic route to obtain bifunctional Sar derivatives has undoubtedly hampered their wider application within the imaging community.…”

“…This is consistent with the reported high kinetic inertness of [ 64 Cu]Cu-Sar complexes. [22][23][24] Challenge experiments of [ 64 Cu]Cu-CryptTM with EDTA and NOTA gave higher rates of trans-chelation with EDTA for both This journal is © The Royal Society of Chemistry 2014 used stoichiometric ratios (1 : 1 and 1 : 100) within the rst 40 min of the experiment. This nding is surprising as Cu(II)-EDTA complex exhibits a thermodynamic complex stability constant three magnitudes lower compared to that of the Cu(II)-NOTA complex.…”