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Olivier Sandre1 2 3 Gauvin Hemery1 2 3 Emmanuel Ibarboure1 2 3 Elisabeth Garanger1 2 3 Sébastien Lecommandoux1 2 3 Coralie Genevois4 Franck Couillaud1 4 Sabrina Lacomme5 1 6 Etienne Gontier5 1 6 Sarah MacEwan7 Ashutosh Chilkoti7

1, CNRS, PESSAC, , France
2, Univ Bordeaux, Pessac, , France
3, Bordeaux INP, Pessac, , France
4, Univ Bordeaux, Bordeaux, , France
5, Univ Bordeaux, Bordeaux, , France
6, Inserm, Bordeaux, , France
7, Duke University, Durham, North Carolina, United States

This communication reports the grafting onto iron oxide nanoparticles (IONPs) of recombinant polypeptides made of di-block elastin-like peptide (ELP40-60) and cell-penetrating peptide (Tat) sequences.1 The ELP40 block is thermosensitive and undergoes a water de-swelling transition at a critical temperature around 42 °C in solution, the ELP60 block is hydrophilic and provides colloidal stability to the resulting γ-Fe2O3@ELP40-60-Tat core-shell IONPs. Magnetic cores were synthesized by a polyol pathway with controlled spherical morphology, size-dispersity and suitable heating efficiency under an alternating magnetic field (AMF).2 The bio-functionalization of these IONPs with the di-block ELP40-60-Tat was achieved by a convergent strategy through strong coordination bonding of a phosphonate group introduced near the N-terminus of the polypeptide. To the best of our knowledge, this is the first report on a thermosensitive ELPm-n polypeptide brush grafting onto magnetic IONPs. Large temperature variations of the sample (up to 30 °C) could be obtained in a few minutes by applying an AMF. Fast size changes of the magnetic core-thermosensitive shell nanoparticles were measured by dynamic light-scattering (DLS) in situ while the AMF was on. Variations of the hydrodynamic size were compared to the classical polymer brush model revised for the highly curved surface of nanoparticles. Cellular internalization and toxicity assays were performed on a human glioblastoma (U87) cell line in view of applications for drug delivery activated magnetically. Superior cellular uptake of the IONPs@ELP40-60-Tat was evidenced compared to IONPs@PEG control nanoparticles prepared from the same magnetic cores. The internalization pathway in lysosomes was monitored by electron microscopy on microtomes and confocal optical microscopy on live cells. Cellular toxicity after AMF application with these core-shell IONPs was ascribed to lysosomal membrane rupture and leakage into the cytosol. The intra-cellular fate of such IONPs, from their internalization to the effect of an AMF application, validates the use of thermosensitive peptide brushes on IONPs as drug delivery systems, addressing lysosomal compartments and triggering leakage of their content by external AMF application. Preliminary in vivo experiments evidenced the positive effect of the Tat peptide end-sequence compared to the PEG brush control on the bio-distribution, with similar contents in the liver and in U87 model tumor in mice. Long term fate (after 48 h) is discussed in view of the cell division with equal sharing of the magnetically loaded lysosomes among daughter cells, possibly envisioning the successive application of magnetic hyperthermia on time scales superior to the cellular life cycle.
1 E Garanger, S MacEwan, O Sandre, A Brûlet, L Bataille, A Chilkoti, S Lecommandoux, Macromol. 2015, 48, 6617
2 G Hemery, A Keyes, E Garaio, I Rodrigo, J A Garcia, F Plazaola, E Garanger, O Sandre, Inorg. Chem. 2017, 56, 8232

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