Metal-ion coordinated self-assembly of human insulin directs kinetics of insulin release as determined by preclinical SPECT/CT imaging

Research output: Contribution to journalJournal articleResearchpeer-review

  • Gokce Engudar
  • Cristina Rodríguez-Rodríguez
  • Narendra Kumar Mishra
  • Marta Bergamo
  • Guillaume Amouroux
  • Jensen, Knud Jørgen
  • Katayoun Saatchi
  • Urs O. Häfeli

Human insulin (HI) has fascinating metal-facilitated self-assembly properties that are essential for its biological function. HI has a natural Zn2+ binding site and we have previously shown that covalently attached abiotic ligands (e.g., bipyridine, terpyridine) can lead to the formation of nanosized oligomeric structures through the coordination of metal ions. Here we studied the hypothesis that metal ions can be used to directly control the pharmacokinetics of insulin after covalent attachment of an abiotic ligand that binds metal ions. We evaluated the pharmacokinetics (PK) and biodistribution of HI self-assemblies directed by metal ion coordination (i.e., Fe2+/Zn2+, Eu3+/Zn2+, Fe2+/Co3+) using preclinical SPECT/CT imaging and ex vivo gamma counting. HI was site-specifically modified with terpyridine (Tpy) at the PheB1 or LysB29 position to create conjugates that bind either Fe2+ or Eu3+, while its natural binding site (HisB10) preferentially coordinates with either Zn2+ or Co3+. HI was also functionalized with trans-cyclooctene (TCO) opposite to Tpy at PheB1 or LysB29, respectively, to allow for tetrazine-TCO coupling via a tetrazine-modified DTPA followed by 111In-radiolabeling for SPECT/CT imaging. When the 111In-B29Tpy-HI conjugate was coordinated with Fe2+/Zn2+, its retention at the injection site 6 h after injection was ~8-fold higher than the control without the metal ions, while its kidney accumulation was lower. 111In-B1Tpy-HI showed comparable retention at the injection site 6 h after injection and slightly increased retention at 24 h. However, higher kidney accumulation and residence time of degraded 111In-B1Tpy-HI was observed compared to that of 111In-B29Tpy-HI. Quantitative PK analysis based on SPECT/CT images confirmed slower distribution from the injection site of the HI-metal ion assemblies compared to control HI conjugates. Our results show that the Tpy-binding site (i.e., PheB1 or LysB29) on HI and its coordination with the added metal ions (i.e., Fe2+/Zn2+ or Fe2+/Co3+) directed the distribution half-life of HI significantly. This clearly indicates that the PK of insulin can be controlled by complexation with different metal ions.

Original languageEnglish
JournalJournal of Controlled Release
Pages (from-to)347-360
Publication statusPublished - 2022

Bibliographical note

Funding Information:
This research was made possible by a grant from the Novo Nordisk Foundation funding the Center for Biopharmaceuticals and Biobarriers in Drug Delivery (BioDelivery; Grand Challenge Program; NNF16OC0021948 ). The Lundbeck Foundation of Denmark (UBC-SUND Lundbeck Foundation Professorship to UOH; project number 2014-4176) is also acknowledged. We would also like to thank the Canada Foundation for Innovation (project number 25413 ) for its support of the imaging facility used in this study, the UBC in vivo Imaging Center ( ). KS acknowledges generous support of BWXT Isotope Technology Group (BWXT ITG) for the supply of the radioisotope. We are grateful to Maryam Osooly for her assistance with the animal studies.

Publisher Copyright:
© 2022

    Research areas

  • Insulin, Metal-ion controlled, Pharmacokinetics, Self-assembly, SPECT/CT imaging

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