Assessing Cobalt Metal Nanoparticles Uptake by Cancer Cells Using Live Raman Spectroscopy

Erwan Rauwel1 ,* Siham Al-Arag2 ,* Hamideh Salehi,2 Carlos O Amorim,3 Frédéric Cuisinier,2 Mithu Guha,4 Maria S Rosario,5 Protima Rauwel1 1Institute of Technology, Estonian University of Life Sciences, Tartu, Estonia; 2LBN, University of Montpellier, Montpellier, France; 3Dpt. Of Physics & CICECO – Aveiro Institute of Materials, University of Aveiro, Aveiro, Portugal; 4Dpt. Of General & Molecular Pathology, Faculty of Medicine, University of Tartu, Tartu, Estonia; 5CICECO – Aveiro Institute of Materials, University of Aveiro, Aveiro, Portugal*These authors contributed equally to this workCorrespondence: Erwan Rauwel Email erwan.rauwel@emu.eePurpose: Nanotechnology applied to cancer treatment is a growing area of research in nanomedicine with magnetic nanoparticle-mediated anti-cancer drug delivery systems offering least possible side effects. To that end, both structural and chemical properties of commercial cobalt metal nanoparticles were studied using label-free confocal Raman spectroscopy.Materials and Methods: Crystal structure and morphology of cobalt nanoparticles were studied by XRD and TEM. Magnetic properties were studied with SQUID and PPMS. Confocal Raman microscopy has high spatial resolution and compositional sensitivity. It, therefore, serves as a label-free tool to trace nanoparticles within cells and investigate the interaction between coating-free cobalt metal nanoparticles and cancer cells. The toxicity of cobalt nanoparticles against human cells was assessed by MTT assay.Results: Superparamagnetic Co metal nanoparticle uptake by MCF7 and HCT116 cancer cells and DPSC mesenchymal stem cells was investigated by confocal Raman microscopy. The Raman nanoparticle signature also allowed accurate detection of the nanoparticle within the cell without labelling. A rapid uptake of the cobalt nanoparticles followed by rapid apoptosis was observed. Their low cytotoxicity, assessed by means of MTT assay against human embryonic kidney (HEK) cells, makes them promising candidates for the development of targeted therapies. Moreover, under a laser irradiation of 20mW with a wavelength of 532nm, it is possible to bring about local heating leading to combustion of the cobalt metal nanoparticles within cells, whereupon opening new routes for cancer phototherapy.Conclusion: Label-free confocal Raman spectroscopy enables accurately localizing the Co metal nanoparticles in cellular environments. The interaction between the surfactant-free cobalt metal nanoparticles and cancer cells was investigated. The facile endocytosis in cancer cells shows that these nanoparticles have potential in engendering their apoptosis. This preliminary study demonstrates the feasibility and relevance of cobalt nanomaterials for applications in nanomedicine such as phototherapy, hyperthermia or stem cell delivery.Keywords: Raman spectroscopy, cobalt nanoparticles, cancer cells, stem cells, cellular uptake, apoptosis, label-free tool