Polyglycerol based Nanoparticles as an EGFR specific multimodal imaging agent


Polyglycerol based Nanoparticles as an EGFR specific multimodal imaging agent

Pant, K.; Zarschler, K.; Neuber, C.; Pufe, J.; Pietzsch, J.; Spiccia, L.; Graham, B.; Stephan, H.

Purpose: Dendritic polyglycerols (dPG) are globular, highly biocompatible macromolecular scaffold which can be synthesized with a broad range of molecular weights and sizes for their desired application.[1] They show a size dependent blood circulation, no protein interactions and a very fast renal clearance.[2] The multiple peripheral groups gives them an advantage of multivalent interactions and thus, multiple moieties for e.g. for PET imaging or optical imaging can be integrated on a single probe for an enhanced resolution leading to an early diagnosis. The purpose of the work was to use these polyglycerols based nanoparticles to attach 64Cu based PET tracer, a dye to the scaffold. For a receptor mediated targeting, a camelid single domain antibody (SdAb) was used which is known to bind to the epidermal growth factor receptors (EGFR).
Experimental description: Dendritic polyglycerol with peripheral hydroxyl groups of a size of 10 kDa and a hydrodynamic volume of 6.5 ± 1.5 nm was prepared in a one pot reaction using ROMBP. Amine groups (9.5%) were introduced to the scaffold for further functionalization. For synthesizing the multimodal agent, the dPG was thiolated using iminothiolane. To the thiolated dPG in a one pot reaction, a maleimide containing DMPTACN based 64Cu chelator, a maleimide containing Cy3 (in vitro) or Cy7 (in vivo) dye were added in a slow monomer type addition. For the targeting unit, the SdAb was attached to the polyglycerol via a maleimide containing PEG linker.
Results: Purification was done using dialysis and several chromatographic techniques. The conjugates were then characterized by UV-Vis, radiometric titrations and microscopy experiments. Radiolabeling was done using 64CuCl2 at physiological conditions with a 99% RCY. Uptake and binding studies were done using A431 and FaDu cell lines using 64Cu labeled conjugate. Confocal scanning laser microscopy was performed for colocalization and internalization studies. In vivo PET and bio distribution studies were done on an A431-tumor mouse model. To confirm receptor specific binding, in vitro as well as in vivo blocking studies were done. The results show a pronounced affinity and active targeting of the dPG multimodal conjugate.
Conclusions: Soft matter nanoparticles based on dendritic polyglycerols are a promising platform for multimodal imaging and theranostics.

Acknowledgements: This study is part of a research initiative “Technologie und Medizin – Multimodale Bildgebung zur Aufklärung des in-vivo Verhaltens von polymeren Biomaterialien” of the Helmholtz-Portfoliothema. Financial support by the Helmholtz Virtual Institute NanoTracking (Agreement Number VH-VI-421) is gratefully acknowledged.

References :

[1] H.Frey, R. Haag; Rev.Mol. Biotechn. 2002, 90, 257-67.
[2] K. Pant, D. Gröger, R. Bergmann, J. Pietzsch, J. Steinbach, B. Graham, L. Spiccia, F. Berthon, B. Czarny, L. Devel, V. Dive, H. Stephan, R. Haag; Bioconjugate Chem. 2015, 26, 906-18

Keywords: Polyglycerols; PET imaging; Nanoparticles; Optical imaging; Antibodies; Multimodality

  • Poster
    2nd International Symposium on Nanoparticles/Nanomaterials and Applications (ISN2A 2016), 18.-21.01.2016, Lisbon, Portugal

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