Remote Loading of 64Cu2+ into Liposomes without the Use of Ion Transport Enhancers

Jonas Rosager Henriksen, Anncatrine Luisa Petersen, Anders Elias Hansen, Christian Grundahl Frankær, Pernille Harris, Dennis Ringkjøbing Elema, Annemarie T. Kristensen, Andreas Kjær, Thomas Lars Andresen

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Abstract

Due to low ion permeability of lipid bilayers, it has been and still is common practice to use transporter molecules such as ionophores or lipophilic chelators to increase transmembrane diffusion rates and loading efficiencies of radionuclides into liposomes. Here, we report a novel and very simple method for loading the positron emitter 64Cu2+ into liposomes, which is important for in vivo positron emission tomography (PET) imaging. By this approach, copper is added to liposomes entrapping a chelator, which causes spontaneous diffusion of copper across the lipid bilayer where it is trapped. Using this method, we achieve highly efficient 64Cu2+ loading (>95%), high radionuclide retention (>95%), and favorable loading kinetics, excluding the use of transporter molecule additives. Therefore, clinically relevant activities of 200-400 MBq/patient can be loaded fast (60-75 min) and efficiently into preformed stealth liposomes avoiding subsequent purification steps. We investigate the molecular coordination of entrapped copper using X-ray absorption spectroscopy and demonstrate high adaptability of the loading method to pegylated, nonpegylated, gel- or fluid-like, cholesterol rich or cholesterol depleted, cationic, anionic, and zwitterionic lipid compositions. We demonstrate high in vivo stability of 64Cu-liposomes in a large canine model observing a blood circulation half-life of 24 h and show a tumor accumulation of 6% ID/g in FaDu xenograft mice using PET imaging. With this work, it is demonstrated that copper ions are capable of crossing a lipid membrane unassisted. This method is highly valuable for characterizing the in vivo performance of liposome-based nanomedicine with great potential in diagnostic imaging applications.
Original languageEnglish
JournalA C S Applied Materials and Interfaces
Volume7
Issue number41
Pages (from-to)22796-22806
Number of pages11
ISSN1944-8244
DOIs
Publication statusPublished - 2015

Keywords

  • Diagnostic
  • Ion permeability
  • Molecular imaging
  • Nanoparticles
  • Positron emission tomography
  • Remote loading

Cite this

Henriksen, Jonas Rosager ; Petersen, Anncatrine Luisa ; Hansen, Anders Elias ; Frankær, Christian Grundahl ; Harris, Pernille ; Elema, Dennis Ringkjøbing ; Kristensen, Annemarie T. ; Kjær, Andreas ; Andresen, Thomas Lars. / Remote Loading of 64Cu2+ into Liposomes without the Use of Ion Transport Enhancers. In: A C S Applied Materials and Interfaces. 2015 ; Vol. 7, No. 41. pp. 22796-22806.
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title = "Remote Loading of 64Cu2+ into Liposomes without the Use of Ion Transport Enhancers",
abstract = "Due to low ion permeability of lipid bilayers, it has been and still is common practice to use transporter molecules such as ionophores or lipophilic chelators to increase transmembrane diffusion rates and loading efficiencies of radionuclides into liposomes. Here, we report a novel and very simple method for loading the positron emitter 64Cu2+ into liposomes, which is important for in vivo positron emission tomography (PET) imaging. By this approach, copper is added to liposomes entrapping a chelator, which causes spontaneous diffusion of copper across the lipid bilayer where it is trapped. Using this method, we achieve highly efficient 64Cu2+ loading (>95{\%}), high radionuclide retention (>95{\%}), and favorable loading kinetics, excluding the use of transporter molecule additives. Therefore, clinically relevant activities of 200-400 MBq/patient can be loaded fast (60-75 min) and efficiently into preformed stealth liposomes avoiding subsequent purification steps. We investigate the molecular coordination of entrapped copper using X-ray absorption spectroscopy and demonstrate high adaptability of the loading method to pegylated, nonpegylated, gel- or fluid-like, cholesterol rich or cholesterol depleted, cationic, anionic, and zwitterionic lipid compositions. We demonstrate high in vivo stability of 64Cu-liposomes in a large canine model observing a blood circulation half-life of 24 h and show a tumor accumulation of 6{\%} ID/g in FaDu xenograft mice using PET imaging. With this work, it is demonstrated that copper ions are capable of crossing a lipid membrane unassisted. This method is highly valuable for characterizing the in vivo performance of liposome-based nanomedicine with great potential in diagnostic imaging applications.",
keywords = "Diagnostic, Ion permeability, Molecular imaging, Nanoparticles, Positron emission tomography, Remote loading",
author = "Henriksen, {Jonas Rosager} and Petersen, {Anncatrine Luisa} and Hansen, {Anders Elias} and Frank{\ae}r, {Christian Grundahl} and Pernille Harris and Elema, {Dennis Ringkj{\o}bing} and Kristensen, {Annemarie T.} and Andreas Kj{\ae}r and Andresen, {Thomas Lars}",
year = "2015",
doi = "10.1021/acsami.5b04612",
language = "English",
volume = "7",
pages = "22796--22806",
journal = "A C S Applied Materials and Interfaces",
issn = "1944-8244",
publisher = "American Chemical Society",
number = "41",

}

Remote Loading of 64Cu2+ into Liposomes without the Use of Ion Transport Enhancers. / Henriksen, Jonas Rosager; Petersen, Anncatrine Luisa; Hansen, Anders Elias; Frankær, Christian Grundahl; Harris, Pernille; Elema, Dennis Ringkjøbing; Kristensen, Annemarie T.; Kjær, Andreas ; Andresen, Thomas Lars.

In: A C S Applied Materials and Interfaces, Vol. 7, No. 41, 2015, p. 22796-22806.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - Remote Loading of 64Cu2+ into Liposomes without the Use of Ion Transport Enhancers

AU - Henriksen, Jonas Rosager

AU - Petersen, Anncatrine Luisa

AU - Hansen, Anders Elias

AU - Frankær, Christian Grundahl

AU - Harris, Pernille

AU - Elema, Dennis Ringkjøbing

AU - Kristensen, Annemarie T.

AU - Kjær, Andreas

AU - Andresen, Thomas Lars

PY - 2015

Y1 - 2015

N2 - Due to low ion permeability of lipid bilayers, it has been and still is common practice to use transporter molecules such as ionophores or lipophilic chelators to increase transmembrane diffusion rates and loading efficiencies of radionuclides into liposomes. Here, we report a novel and very simple method for loading the positron emitter 64Cu2+ into liposomes, which is important for in vivo positron emission tomography (PET) imaging. By this approach, copper is added to liposomes entrapping a chelator, which causes spontaneous diffusion of copper across the lipid bilayer where it is trapped. Using this method, we achieve highly efficient 64Cu2+ loading (>95%), high radionuclide retention (>95%), and favorable loading kinetics, excluding the use of transporter molecule additives. Therefore, clinically relevant activities of 200-400 MBq/patient can be loaded fast (60-75 min) and efficiently into preformed stealth liposomes avoiding subsequent purification steps. We investigate the molecular coordination of entrapped copper using X-ray absorption spectroscopy and demonstrate high adaptability of the loading method to pegylated, nonpegylated, gel- or fluid-like, cholesterol rich or cholesterol depleted, cationic, anionic, and zwitterionic lipid compositions. We demonstrate high in vivo stability of 64Cu-liposomes in a large canine model observing a blood circulation half-life of 24 h and show a tumor accumulation of 6% ID/g in FaDu xenograft mice using PET imaging. With this work, it is demonstrated that copper ions are capable of crossing a lipid membrane unassisted. This method is highly valuable for characterizing the in vivo performance of liposome-based nanomedicine with great potential in diagnostic imaging applications.

AB - Due to low ion permeability of lipid bilayers, it has been and still is common practice to use transporter molecules such as ionophores or lipophilic chelators to increase transmembrane diffusion rates and loading efficiencies of radionuclides into liposomes. Here, we report a novel and very simple method for loading the positron emitter 64Cu2+ into liposomes, which is important for in vivo positron emission tomography (PET) imaging. By this approach, copper is added to liposomes entrapping a chelator, which causes spontaneous diffusion of copper across the lipid bilayer where it is trapped. Using this method, we achieve highly efficient 64Cu2+ loading (>95%), high radionuclide retention (>95%), and favorable loading kinetics, excluding the use of transporter molecule additives. Therefore, clinically relevant activities of 200-400 MBq/patient can be loaded fast (60-75 min) and efficiently into preformed stealth liposomes avoiding subsequent purification steps. We investigate the molecular coordination of entrapped copper using X-ray absorption spectroscopy and demonstrate high adaptability of the loading method to pegylated, nonpegylated, gel- or fluid-like, cholesterol rich or cholesterol depleted, cationic, anionic, and zwitterionic lipid compositions. We demonstrate high in vivo stability of 64Cu-liposomes in a large canine model observing a blood circulation half-life of 24 h and show a tumor accumulation of 6% ID/g in FaDu xenograft mice using PET imaging. With this work, it is demonstrated that copper ions are capable of crossing a lipid membrane unassisted. This method is highly valuable for characterizing the in vivo performance of liposome-based nanomedicine with great potential in diagnostic imaging applications.

KW - Diagnostic

KW - Ion permeability

KW - Molecular imaging

KW - Nanoparticles

KW - Positron emission tomography

KW - Remote loading

U2 - 10.1021/acsami.5b04612

DO - 10.1021/acsami.5b04612

M3 - Journal article

VL - 7

SP - 22796

EP - 22806

JO - A C S Applied Materials and Interfaces

JF - A C S Applied Materials and Interfaces

SN - 1944-8244

IS - 41

ER -