Transglutaminase-mediated conjugation and nitride-technetium-99m labelling of a bis(thiosemicarbazone) bifunctional chelator

Nicola Salvarese; Barbara Spolaore; Selena Marangoni; Anna Pasin; Alessandro Galenda; Sergio Tamburini; Gianfranco Cicoria; Fiorenzo Refosco; Cristina Bolzati

doi:10.1016/j.jinorgbio.2018.02.023

Transglutaminase-mediated conjugation and nitride-technetium-99m labelling of a bis(thiosemicarbazone) bifunctional chelator

J Inorg Biochem. 2018 Jun:183:18-31. doi: 10.1016/j.jinorgbio.2018.02.023. Epub 2018 Mar 2.

Authors

Nicola Salvarese¹, Barbara Spolaore², Selena Marangoni², Anna Pasin², Alessandro Galenda³, Sergio Tamburini³, Gianfranco Cicoria⁴, Fiorenzo Refosco³, Cristina Bolzati⁵

Affiliations

¹ ICMATE-CNR, Corso Stati Uniti 4, 35127 Padua, Italy; Dipartimento di Scienze del Farmaco, Università Degli Studi di Padova, Via F. Marzolo 5, 35131 Padua, Italy. Electronic address: salvarese-lab@yahoo.it.
² Dipartimento di Scienze del Farmaco, Università Degli Studi di Padova, Via F. Marzolo 5, 35131 Padua, Italy.
³ ICMATE-CNR, Corso Stati Uniti 4, 35127 Padua, Italy.
⁴ Medical Physics Department, Azienda Ospedaliera Universitaria di Bologna, Policlinico S. Orsola-Malpighi, Via Massarenti 9, 40138 Bologna, Italy.
⁵ ICMATE-CNR, Corso Stati Uniti 4, 35127 Padua, Italy; Dipartimento di Scienze del Farmaco, Università Degli Studi di Padova, Via F. Marzolo 5, 35131 Padua, Italy. Electronic address: cristina.bolzati@cnr.it.

PMID: 29529469
DOI: 10.1016/j.jinorgbio.2018.02.023

Abstract

An assessment study involving the use of the transglutaminase (TGase) conjugation method and the nitride-technetium-99m labelling on a bis(thiosemicarbazone) (BTS) bifunctional chelating agent is presented. The previously described chelator diacetyl-2-(N⁴-methyl-3-thiosemicarbazone)-3-(N⁴-amino-3-thiosemicarbazone), H₂ATSM/A, has been functionalized with 6-aminohexanoic acid (ε-Ahx) to generate the bifunctional chelating agent diacetyl-2-(N⁴-methyl-3-thiosemicarbazone)-3-[N⁴-(amino)-(6-aminohexanoic acid)-3-thiosemicarbazone], H₂ATSM/A-ε-Ahx (1), suitable for conjugation to glutamine (Gln) residues of bioactive molecules via TGase. The feasibility of the TGase reaction in the synthesis of a bioconjugate derivative was investigated using Substance P (SP) as model peptide. Compounds 1 and H₂ATSM/A-ε-Ahx-SP (2) were labelled with nitride-technetium-99m, obtaining the complexes [^99mTc][Tc(N)(ATSM/A-ε-Ahx)] (^99mTc1) and [^99mTc][Tc(N)(ATSM/A-ε-Ahx-SP)] (^99mTc2). The chemical identity of ^99mTc1 and ^99mTc2 was confirmed by radio/UV-RP-HPLC combined with ESI-MS analysis on the respective carrier-added products ^99g/99mTc1 and ^99g/99mTc2. The stability of the radiolabelled complexes after incubation in various environments was investigated. All the results were compared with those obtained for the corresponding ⁶⁴Cu-analogues, ⁶⁴Cu1 and ⁶⁴Cu2. The TGase reaction allows the conjugation of 1 with the peptide, but it is not highly efficient due to instability of the chelator in the required conditions. The SP-conjugated complexes are unstable in mouse and human sera. However, indeed the BTS system can be exploited as nitride-technetium-99m chelator for highly efficient technetium labelling, thus making compound 1 worthy of further investigations for new targeted technetium and copper radiopharmaceuticals encompassing Single Photon Emission Computed Tomography and Positron Emission Tomography imaging.

Keywords: Bis(thiosemicarbazone); Copper; Substance P; Technetium; Transglutaminase.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Chelating Agents / chemistry
Substance P / chemistry
Technetium / chemistry*
Transglutaminases / metabolism*

Substances

Chelating Agents
Technetium-99
Substance P
Technetium
Transglutaminases