1
|
Tosato M, Randhawa P, Lazzari L, McNeil BL, Dalla Tiezza M, Zanoni G, Mancin F, Orian L, Ramogida CF, Di Marco V. Tuning the Softness of the Pendant Arms and the Polyazamacrocyclic Backbone to Chelate the 203Pb/ 212Pb Theranostic Pair. Inorg Chem 2024; 63:1745-1758. [PMID: 38230993 PMCID: PMC10828988 DOI: 10.1021/acs.inorgchem.3c02610] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Revised: 12/18/2023] [Accepted: 12/20/2023] [Indexed: 01/18/2024]
Abstract
A series of macrocyclic ligands were considered for the chelation of Pb2+: 1,4,7,10-tetrakis[2-(methylsulfanyl)ethyl]-1,4,7,10-tetraazacyclododecane (DO4S), 1,4,7-tris[2-(methylsulfanyl)ethyl]-1,4,7,10-tetraazacyclododecane (DO3S), 1,4,7-tris[2-(methylsulfanyl)ethyl]-10-acetamido-1,4,7,10-tetraazacyclododecane (DO3SAm), 1,7-bis[2-(methylsulfanyl)ethyl]-1,4,7,10-tetraazacyclododecane-4,10-diacetic acid (DO2A2S), 1,5,9-tris[2-(methylsulfanyl)ethyl]-1,5,9-triazacyclododecane (TACD3S), 1,4,7,10-tetrakis[2-(methylsulfanyl)ethyl]-1,4,7,10-tetrazacyclotridecane (TRI4S), and 1,4,8,11-tetrakis[2-(methylsulfanyl)ethyl]-1,4,8,11-tetrazacyclotetradecane (TE4S). The equilibrium, the acid-mediated dissociation kinetics, and the structural properties of the Pb2+ complexes formed by these chelators were examined by UV-Visible and nuclear magnetic resonance (NMR) spectroscopies, combined with potentiometry and density functional theory (DFT) calculations. The obtained results indicated that DO4S, DO3S, DO3SAm, and DO2A2S were able to efficiently chelate Pb2+ and that the most suitable macrocyclic scaffold for Pb2+ is 1,4,7,10-tetrazacyclododecane. NMR spectroscopy gave insights into the solution structures of the Pb2+ complexes, and 1H-207Pb interactions confirmed the involvement of S and/or O donors in the metal coordination sphere. Highly fluxional solution behavior was discovered when Pb2+ was coordinated to symmetric ligands (i.e., DO4S and DO2A2S) while the introduction of structural asymmetry in DO3S and DO3SAm slowed down the intramolecular dynamics. The ligand ability to chelate [203Pb]Pb2+ under highly dilute reaction conditions was explored through radiolabeling experiments. While DO4S and DO3S possessed modest performance, DO3SAm and DO2A2S demonstrated high complexation efficiency under mild reaction conditions (pH = 7, 5 min reaction time). The [203Pb]Pb2+ complexes' integrity in human serum over 24 h was appreciably good for [203Pb][Pb(DO4S)]2+ (80 ± 5%) and excellent for [203Pb][Pb(DO3SAm)]2+ (93 ± 1%) and [203Pb][Pb(DO2A2S)] (94 ± 1%). These results reveal the promise of DO2A2S and DO3SAm as chelators in cutting-edge theranostic [203/212Pb]Pb2+ radiopharmaceuticals.
Collapse
Affiliation(s)
- Marianna Tosato
- Department
of Chemical Sciences, University of Padova, 35131 Padova, Italy
- Radiopharmaceutical
Chemistry Section, Nuclear Medicine Unit, AUSL-IRCCS Reggio Emilia, 42122 Reggio Emilia, Italy
- Department
of Chemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
- Life
Sciences Division, TRIUMF, Vancouver, British Columbia V6T 2A3, Canada
| | - Parmissa Randhawa
- Department
of Chemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
- Life
Sciences Division, TRIUMF, Vancouver, British Columbia V6T 2A3, Canada
| | - Luca Lazzari
- Department
of Chemical Sciences, University of Padova, 35131 Padova, Italy
| | - Brooke L. McNeil
- Department
of Chemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
- Life
Sciences Division, TRIUMF, Vancouver, British Columbia V6T 2A3, Canada
| | - Marco Dalla Tiezza
- Department
of Chemical Sciences, University of Padova, 35131 Padova, Italy
| | - Giordano Zanoni
- Department
of Chemical Sciences, University of Padova, 35131 Padova, Italy
| | - Fabrizio Mancin
- Department
of Chemical Sciences, University of Padova, 35131 Padova, Italy
| | - Laura Orian
- Department
of Chemical Sciences, University of Padova, 35131 Padova, Italy
| | - Caterina F. Ramogida
- Department
of Chemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
- Life
Sciences Division, TRIUMF, Vancouver, British Columbia V6T 2A3, Canada
| | - Valerio Di Marco
- Department
of Chemical Sciences, University of Padova, 35131 Padova, Italy
| |
Collapse
|
2
|
Ingham A, Kostelnik TI, McNeil BL, Patrick BO, Choudhary N, Jaraquemada-Peláez MDG, Orvig C. Getting a lead on Pb 2+-amide chelators for 203/212Pb radiopharmaceuticals. Dalton Trans 2021; 50:11579-11595. [PMID: 34352061 DOI: 10.1039/d1dt01653a] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Amide-based chelators DTPAm, EGTAm and ampam were synthesized to investigate which chelator most ideally coordinates [nat/203Pb]Pb2+ ions for potential radiopharmaceutical applications. 1H NMR spectroscopy was used to study each metal-ligand complex in the solution state. The 1H NMR spectrum of [Pb(DTPAm)]2+ revealed minimal isomerization and fluxional behaviour compared to [Pb(EGTAm)]2+ and [Pb(ampam)]2+, both of which showed fewer spectral changes indicative of less static behaviour. The solid-state coordination properties of each complex were also examined from single crystal structures that were studied by X-ray diffraction (XRD). In the solid-state, octadentate DTPAm coordinated Pb2+ to form an eight-coordinate hemidirected complex; octadentate EGTAm coordinated Pb2+ forming a ten-coordinate holodirected complex with a bidentate NO3- ion also coordinated to the metal centre; decadentate ampam completely encapsulated the Pb2+ ion to form a ten-coordinate holodirected complex with a C2 axis of symmetry. Potentiometric titrations were carried out to assess the thermodynamic stability of each metal-ligand complex. The pM values obtained for [Pb(DTPAm)]2+, [Pb(EGTAm)]2+ and [Pb(ampam)]2+ were 9.7, 7.2 and 10.2, respectively. The affinity of each chelator for Pb2+ ions was tested by [203Pb]Pb2+ radiolabeling studies to evaluate their prospects as chelators for [203/212Pb]Pb2+-based radiopharmaceuticals. DTPAm radiolabeled [203Pb]Pb2+ ions achieving molar activities as high as 3.5 MBq μmol-1 within 15 minutes, at 25 °C, whereas EGTAm and ampam produced lower molar activities of 0.25 MBq μmol-1 within 30 minutes, at 37 °C. EGTAm and ampam were therefore deemed unsuitable for [203/212Pb]Pb2+-based radiopharmaceutical applications, while DTPAm warrants further studies.
Collapse
Affiliation(s)
- Aidan Ingham
- Medicinal Inorganic Chemistry Group, Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia V6 T 1Z1, Canada.
| | | | | | | | | | | | | |
Collapse
|