{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,16]],"date-time":"2026-09-16T13:18:10Z","timestamp":1789564690156,"version":"build-2803163510"},"reference-count":54,"publisher":"MDPI AG","issue":"1","license":[{"start":{"date-parts":[[2019,1,8]],"date-time":"2019-01-08T00:00:00Z","timestamp":1546905600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["IJMS"],"abstract":"<jats:p>The use of titanium suboxides, known as Magn\u00e9li phase TiOx, is expected to increase in the near future due to their desirable properties. In order to use Magn\u00e9li phase TiOx nanoparticles safely, it is necessary to know how nanoparticles interact with biological systems. In this study, the cytotoxicity of three different Magn\u00e9li TiOx nanoparticles was evaluated using human lung A549 cells and the results were compared with hazard data on two different TiO2 nanoparticles whose biological interactions have already been extensively studied. After A549 cells were exposed to nanoparticles, the metabolic activity was measured by the Resazurin assay, the amount of cellular proteins was measured by the Coomassie Blue assay, and lysosomal integrity was measured by the Neutral Red Uptake assay. In order to investigate possible modes of particle actions, intracellular Ca2+ level, reactive oxygen species (ROS) production, and photo-oxidative disruptions of lysosomal membranes were assessed. All experiments were performed in serum-containing and in serum-deprived cell culture mediums. In addition, the photocatalytic activity of Magn\u00e9li TiOx and TiO2 nanoparticles was measured. The results show that Magn\u00e9li TiOx nanoparticles increase intracellular Ca2+ but not ROS levels. In contrast, TiO2 nanoparticles increase ROS levels, resulting in a higher cytotoxicity. Although Magn\u00e9li TiOx nanoparticles showed a lower UV-A photocatalytic activity, the photo-stability of the lysosomal membranes was decreased by a greater extent, possibly due to particle accumulation inside lysosomes. We provide evidence that Magn\u00e9li TiOx nanoparticles have lower overall biological activity when compared with the two TiO2 formulations. However, some unique cellular interactions were detected and should be further studied in line with possible Magn\u00e9li TiOx application. We conclude that Magn\u00e9li phase nanoparticles could be considered as low toxic material same as other forms of titanium oxide particles.<\/jats:p>","DOI":"10.3390\/ijms20010196","type":"journal-article","created":{"date-parts":[[2019,1,9]],"date-time":"2019-01-09T03:06:06Z","timestamp":1547003166000},"page":"196","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":31,"title":["In Vitro Cytotoxicity Evaluation of the Magn\u00e9li Phase Titanium Suboxides (TixO2x\u22121) on A549 Human Lung Cells"],"prefix":"10.3390","volume":"20","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-3066-0328","authenticated-orcid":false,"given":"Veno","family":"Kononenko","sequence":"first","affiliation":[{"name":"Department of Biology, Biotechnical Faculty, University of Ljubljana, Ve\u010dna pot 111, 1000 Ljubljana, Slovenia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5970-7460","authenticated-orcid":false,"given":"Damjana","family":"Drobne","sequence":"additional","affiliation":[{"name":"Department of Biology, Biotechnical Faculty, University of Ljubljana, Ve\u010dna pot 111, 1000 Ljubljana, Slovenia"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2019,1,8]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"De Matteis, V. (2017). Exposure to inorganic nanoparticles: Routes of entry, immune response, biodistribution and in vitro\/in vivo toxicity evaluation. Toxics, 5.","DOI":"10.3390\/toxics5040029"},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"Irache, J.M., Mart\u00edn-Arbella, N., Ojer, P., Azqueta, A., and de Cerain, A.L. (2016). Toxicological Aspects of Polymer Nanoparticles. Polymer Nanoparticles for Nanomedicines, Springer.","DOI":"10.1007\/978-3-319-41421-8_16"},{"key":"ref_3","doi-asserted-by":"crossref","unstructured":"Berger, E., Breznan, D., Stals, S., Jasinghe, V.J., Gon\u00e7alves, D., Girard, D., Faucher, S., Vincent, R., Thierry, A.R., and Lavigne, C. (2017). Cytotoxicity assessment, inflammatory properties, and cellular uptake of Neutraplex lipid-based nanoparticles in THP-1 monocyte-derived macrophages. Nanobiomedicine, 4.","DOI":"10.1177\/1849543517746259"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"6500","DOI":"10.1021\/acs.nanolett.8b03032","article-title":"Predicting Nanotube Fibrogenicity through Stem Cell-Mediated Fibroblast Focus and Spheroid Formation","volume":"18","author":"He","year":"2018","journal-title":"Nano Lett."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"689","DOI":"10.1039\/C6EN00402D","article-title":"Carbon nanotubes induced fibrogenesis on nanostructured substrates","volume":"4","author":"Wang","year":"2017","journal-title":"Environ. Sci. Nano"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"28","DOI":"10.1186\/s12951-015-0087-3","article-title":"Effect of carbon black nanomaterial on biological membranes revealed by shape of human erythrocytes, platelets and phospholipid vesicles","volume":"13","author":"Krek","year":"2015","journal-title":"J. Nanobiotechnol."},{"key":"ref_7","first-page":"713","article-title":"Overview on biological implications of metal oxide nanoparticle exposure to human alveolar A549 cell line","volume":"11","author":"Martin","year":"2017","journal-title":"Nanotoxicology"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"256","DOI":"10.1016\/j.tiv.2017.01.015","article-title":"Comparative in vitro genotoxicity study of ZnO nanoparticles, ZnO macroparticles and ZnCl2 to MDCK kidney cells: Size matters","volume":"40","author":"Kononenko","year":"2017","journal-title":"Toxicol. In Vitro"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"419","DOI":"10.1080\/17435390.2017.1309704","article-title":"Harmful at non-cytotoxic concentrations: SiO2-SPIONs affect surfactant metabolism and lamellar body biogenesis in A549 human alveolar epithelial cells","volume":"11","author":"Kononenko","year":"2017","journal-title":"Nanotoxicology"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"64","DOI":"10.1016\/j.jfda.2014.01.005","article-title":"Mechanisms of nanotoxicity: Generation of reactive oxygen species","volume":"22","author":"Fu","year":"2014","journal-title":"J. Food Drug Anal."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"B321","DOI":"10.1149\/1.2833310","article-title":"Stability of corrosion-resistant Magn\u00e9li-phase Ti4O7-supported PEMFC catalysts at high potentials","volume":"155","author":"Ioroi","year":"2008","journal-title":"J. Electrochem. Soc."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"3646","DOI":"10.1038\/s41598-017-03509-y","article-title":"Highly conductive nano-sized Magn\u00e9li phases titanium oxide (TiOx)","volume":"7","author":"Arif","year":"2017","journal-title":"Sci. Rep."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"6342","DOI":"10.1016\/j.electacta.2010.05.011","article-title":"The continuing development of Magn\u00e9li phase titanium sub-oxides and Ebonex\u00aeelectrodes","volume":"55","author":"Walsh","year":"2010","journal-title":"Electrochim. Acta"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"316","DOI":"10.1016\/j.electacta.2014.11.178","article-title":"Highly-ordered magn\u00e9li Ti4O7 nanotube arrays as effective anodic material for electro-oxidation","volume":"153","author":"Geng","year":"2015","journal-title":"Electrochim. Acta"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"10131","DOI":"10.1021\/cr400625j","article-title":"Titanium dioxide nanomaterials for sensor applications","volume":"114","author":"Bai","year":"2014","journal-title":"Chem. Rev."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"737","DOI":"10.1038\/353737a0","article-title":"A low-cost, high-efficiency solar cell based on dye-sensitized colloidal TiO2 films","volume":"353","year":"1991","journal-title":"Nature"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"33","DOI":"10.1016\/j.progsolidstchem.2004.08.001","article-title":"Photoinduced reactivity of titanium dioxide","volume":"32","author":"Carp","year":"2004","journal-title":"Prog. Solid State Chem."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"1401","DOI":"10.1016\/j.msec.2017.02.150","article-title":"A review of TiO2NTs on Ti metal: Electrochemical synthesis, functionalization and potential use as bone implants","volume":"76","author":"Awad","year":"2017","journal-title":"Mater. Sci. Eng. C"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"169","DOI":"10.1016\/j.jphotochemrev.2012.06.001","article-title":"TiO2 photocatalysis: Design and applications","volume":"13","author":"Nakata","year":"2012","journal-title":"J. Photochem. Photobiol. C Photochem. Rev."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"153","DOI":"10.1016\/bs.abl.2017.06.002","article-title":"Phototoxicity of mesoporous TiO2+Gd microbeads with theranostic potential","volume":"Volume 26","author":"Rappolt","year":"2017","journal-title":"Advances in Biomembranes and Lipid Self-Assembly"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"1700349","DOI":"10.1002\/smll.201700349","article-title":"Multifunctional Gadolinium-Doped Mesoporous TiO2 Nanobeads: Photoluminescence, Enhanced Spin Relaxation, and Reactive Oxygen Species Photogeneration, Beneficial for Cancer Diagnosis and Treatment","volume":"13","author":"Imani","year":"2017","journal-title":"Small"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"38","DOI":"10.1016\/j.ssi.2012.10.003","article-title":"AC electrical properties of TiO2 and Magn\u00e9li phases, TinO2n\u22121","volume":"229","author":"Regonini","year":"2012","journal-title":"Solid State Ionics"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"194","DOI":"10.1038\/s41467-017-00276-2","article-title":"Discovery and ramifications of incidental Magn\u00e9li phase generation and release from industrial coal-burning","volume":"8","author":"Yang","year":"2017","journal-title":"Nat. Commun."},{"key":"ref_24","unstructured":"Jemec Kokalj, A., Novak, S., Talaber, I., Kononenko, V., Bizjak Mali, L., Vodovnik, M., \u017degura, B., Eler\u0161ek, T., Kal\u010dikova, G., and \u017dgajnar Gotvajn, A. (2019). Jemec Kokalj manuscript. Environ. Sci. Nano, submitted for publication."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"26","DOI":"10.1002\/smll.201303947","article-title":"Toxicity of metal oxide nanoparticles: Mechanisms, characterization, and avoiding experimental artefacts","volume":"11","author":"Leung","year":"2015","journal-title":"Small"},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Huang, Y.W., Cambre, M., and Lee, H.J. (2017). The Toxicity of Nanoparticles Depends on Multiple Molecular and Physicochemical Mechanisms. Int. J. Mol. Sci., 18.","DOI":"10.3390\/ijms18122702"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"20","DOI":"10.1186\/1743-8977-9-20","article-title":"Autophagy and lysosomal dysfunction as emerging mechanisms of nanomaterial toxicity","volume":"9","author":"Stern","year":"2012","journal-title":"Part. Fibre Toxicol."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"1150","DOI":"10.1002\/jat.3160","article-title":"Intracellular calcium levels as screening tool for nanoparticle toxicity","volume":"35","author":"Meindl","year":"2015","journal-title":"J. Appl. Toxicol."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"45","DOI":"10.1016\/j.tiv.2009.09.007","article-title":"Oxidative stress, calcium homeostasis, and altered gene expression in human lung epithelial cells exposed to ZnO nanoparticles","volume":"24","author":"Huang","year":"2010","journal-title":"Toxicol. In Vitro"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"1125","DOI":"10.1038\/nprot.2008.75","article-title":"Neutral red uptake assay for the estimation of cell viability\/cytotoxicity","volume":"3","author":"Repetto","year":"2008","journal-title":"Nat. Protoc."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"616","DOI":"10.1016\/S0891-5849(97)00007-5","article-title":"Photo-oxidative disruption of lysosomal membranes causes apoptosis of cultured human fibroblasts","volume":"23","author":"Brunk","year":"1997","journal-title":"Free Radic. Biol. Med."},{"key":"ref_32","first-page":"1","article-title":"Three-dimensional graphene foam as a biocompatible and conductive scaffold for neural stem cells","volume":"3","author":"Li","year":"2013","journal-title":"Sci. Rep."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"5478","DOI":"10.1021\/nn2007496","article-title":"Effect of gold nanoparticle aggregation on cell uptake and toxicity","volume":"5","author":"Albanese","year":"2011","journal-title":"ACS Nano"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"6287","DOI":"10.1039\/C4CS00487F","article-title":"Nanoparticle colloidal stability in cell culture media and impact on cellular interactions","volume":"44","author":"Moore","year":"2015","journal-title":"Chem. Soc. Rev."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"7309","DOI":"10.1021\/es100417s","article-title":"Dispersion and stability optimization of TiO2 nanoparticles in cell culture media","volume":"44","author":"Ji","year":"2010","journal-title":"Environ. Sci. Technol."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"1941","DOI":"10.1002\/smll.200700378","article-title":"Size-dependent cytotoxicity of gold nanoparticles","volume":"3","author":"Pan","year":"2007","journal-title":"Small"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"8","DOI":"10.1016\/j.mrgentox.2015.11.011","article-title":"Characterization of in vitro genotoxic, cytotoxic and transcriptomic responses following exposures to amorphous silica of different sizes","volume":"796","author":"Decan","year":"2016","journal-title":"Mutat. Res. Toxicol. Environ. Mutagen."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"331","DOI":"10.1002\/jbt.21798","article-title":"Differential genomic effects of six different TiO2 nanomaterials on human liver HepG2 cells","volume":"30","author":"Thai","year":"2016","journal-title":"J. Biochem. Mol. Toxicol."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"4083","DOI":"10.1021\/nn3004845","article-title":"Effects of serum adsorption on cellular uptake profile and consequent impact of titanium dioxide nanoparticles on human lung cell lines","volume":"6","author":"Tedja","year":"2012","journal-title":"ACS Nano"},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"3818","DOI":"10.1021\/nl072471q","article-title":"Oligonucleotide loading determines cellular uptake of DNA-modified gold nanoparticles","volume":"7","author":"Giljohann","year":"2007","journal-title":"Nano Lett."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"377","DOI":"10.1177\/0960327109105158","article-title":"Preparation of nanoparticle dispersions for in-vitro toxicity testing","volume":"28","author":"Vippola","year":"2009","journal-title":"Hum. Exp. Toxicol."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"1322","DOI":"10.1002\/smll.201100001","article-title":"Cellular uptake, intracellular trafficking, and cytotoxicity of nanomaterials","volume":"7","author":"Zhao","year":"2011","journal-title":"Small"},{"key":"ref_43","doi-asserted-by":"crossref","unstructured":"L\u00fcllmann-Rauch, R. (2005). History and morphology of the lysosome. Lysosomes, Springer.","DOI":"10.1007\/0-387-28957-7_1"},{"key":"ref_44","doi-asserted-by":"crossref","unstructured":"Brini, M., Cal\u00ec, T., Ottolini, D., and Carafoli, E. (2013). Intracellular calcium homeostasis and signaling. Metallomics and the Cell, Springer.","DOI":"10.1007\/978-94-007-5561-1_5"},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"322","DOI":"10.1016\/j.carbon.2016.10.015","article-title":"Autophagy and lysosomal dysfunction: A new insight into mechanism of synergistic pulmonary toxicity of carbon black-metal ions co-exposure","volume":"111","author":"Kong","year":"2017","journal-title":"Carbon"},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"723","DOI":"10.1083\/jcb.201208152","article-title":"Lysosomal storage disorders: The cellular impact of lysosomal dysfunction","volume":"199","author":"Platt","year":"2012","journal-title":"J. Cell Biol."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1186\/1743-8977-7-10","article-title":"Carbon black and titanium dioxide nanoparticles elicit distinct apoptotic pathways in bronchial epithelial cells","volume":"7","author":"Hussain","year":"2010","journal-title":"Part. Fibre Toxicol."},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"1871","DOI":"10.1021\/tx800179f","article-title":"Cytotoxicity of Titanium Dioxide Nanoparticles in Mouse Fibroblast Cells Cytotoxicity of Titanium Dioxide Nanoparticles in Mouse Fibroblast","volume":"21","author":"Jin","year":"2008","journal-title":"Chem. Res. Toxicol."},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"297","DOI":"10.1034\/j.1399-3003.2000.15b13.x","article-title":"Increased calcium influx in a monocytic cell line on exposure to ultrafine carbon black","volume":"15","author":"Stone","year":"2000","journal-title":"Eur. Respir. J."},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"1163","DOI":"10.3390\/nano5031163","article-title":"Nanotoxicity: An Interplay of Oxidative Stress, Inflammation and Cell Death","volume":"5","author":"Khanna","year":"2015","journal-title":"Nanomaterials"},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"89","DOI":"10.1111\/j.1365-2796.2009.02187.x","article-title":"Safety assessment for nanotechnology and nanomedicine: Concepts of nanotoxicology","volume":"267","year":"2010","journal-title":"J. Intern. Med."},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"99","DOI":"10.1016\/j.impact.2017.08.002","article-title":"In vitro approaches to assess the hazard of nanomaterials","volume":"8","author":"Drasler","year":"2017","journal-title":"NanoImpact"},{"key":"ref_53","doi-asserted-by":"crossref","first-page":"533","DOI":"10.3109\/08958379509015211","article-title":"Chronic inhalation exposure of Wistar rats and two different strains of mice to diesel engine exhaust, carbon black, and titanium dioxide","volume":"7","author":"Heinrich","year":"1995","journal-title":"Inhal. Toxicol."},{"key":"ref_54","doi-asserted-by":"crossref","first-page":"1229","DOI":"10.1080\/17435390.2016.1196251","article-title":"Multilaboratory evaluation of 15 bioassays for (eco) toxicity screening and hazard ranking of engineered nanomaterials: FP7 project NANOVALID","volume":"10","author":"Bondarenko","year":"2016","journal-title":"Nanotoxicology"}],"container-title":["International Journal of Molecular Sciences"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1422-0067\/20\/1\/196\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T12:24:08Z","timestamp":1760185448000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1422-0067\/20\/1\/196"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2019,1,8]]},"references-count":54,"journal-issue":{"issue":"1","published-online":{"date-parts":[[2019,1]]}},"alternative-id":["ijms20010196"],"URL":"https:\/\/doi.org\/10.3390\/ijms20010196","relation":{},"ISSN":["1422-0067"],"issn-type":[{"value":"1422-0067","type":"electronic"}],"subject":[],"published":{"date-parts":[[2019,1,8]]}}}