{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,20]],"date-time":"2026-10-20T02:05:25Z","timestamp":1792461925101,"version":"4.5.0"},"reference-count":30,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2026,8,24]],"date-time":"2026-08-24T00:00:00Z","timestamp":1787529600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001711","name":"Swiss National Science Foundation","doi-asserted-by":"publisher","award":["10002455"],"award-info":[{"award-number":["10002455"]}],"id":[{"id":"10.13039\/501100001711","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001711","name":"Swiss National Science Foundation","doi-asserted-by":"publisher","award":["207460"],"award-info":[{"award-number":["207460"]}],"id":[{"id":"10.13039\/501100001711","id-type":"DOI","asserted-by":"publisher"}]},{"award":["10002455"],"award-info":[{"award-number":["10002455"]}],"id":[{"id":"https:\/\/ror.org\/00yjd3n13","id-type":"ROR","asserted-by":"publisher"}]},{"award":["207460"],"award-info":[{"award-number":["207460"]}],"id":[{"id":"https:\/\/ror.org\/00yjd3n13","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Biomolecules"],"abstract":"<jats:p>Photodynamic therapy (PDT) exploits photoactivated materials that generate reactive oxygen species (ROS) to induce selective cancer cell death. Nitrogen-doped carbon dots (N-CDs) have emerged as promising photosensitizers owing to their favorable optical properties, while hybridization with titanium dioxide (TiO2) may further enhance photoinduced ROS generation through improved charge separation. Here, we synthesized a series of N-CD\/TiO2 hybrid composites with varying TiO2 content using a hydrothermal approach and systematically investigated the relationship between their physicochemical characteristics and biological activity. The hybrid materials were characterized by Fourier-transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, dynamic light scattering, and UV\u2013visible spectroscopy. Among the formulations investigated, the composite containing 90% N-CDs and 10% TiO2 (N-CDs10T) exhibited the smallest hydrodynamic diameter, a relatively narrow particle size distribution, favorable optical properties, and the strongest irradiation-dependent biological responses. Biological activity was evaluated in A549 lung adenocarcinoma and Kelly neuroblastoma cells. Under dark conditions, all formulations displayed relatively low intrinsic cytotoxicity. Following irradiation with 365 nm UVA light, however, N-CDs10T induced a marked increase in intracellular ROS production, activation of antioxidant response element (ARE)-dependent signaling, disruption of cell-cycle progression, apoptosis-associated cell death, and inhibition of cell proliferation and migration. Kelly cells exhibited greater sensitivity than A549 cells, with IC50 values decreasing from 0.98 mg\/mL under dark conditions to 0.52 mg\/mL following irradiation. Collectively, these findings demonstrate that N-CD\/TiO2 hybrid composites function as photoresponsive materials that enhance ROS-mediated cytotoxicity upon light activation. Beyond demonstrating phototoxicity, this study systematically links hybrid composition with oxidative stress signaling and multiple cellular responses, providing a comprehensive biological evaluation of N-CD\/TiO2 hybrid materials. While additional studies are required to identify the predominant ROS, evaluate selectivity in non-malignant cells, and optimize activation at clinically relevant wavelengths, the present work establishes a proof of concept for the development of N-CD\/TiO2 hybrid composites for photodynamic applications.<\/jats:p>","DOI":"10.3390\/biom16091229","type":"journal-article","created":{"date-parts":[[2026,8,24]],"date-time":"2026-08-24T17:20:28Z","timestamp":1787592028000},"page":"1229","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Nitrogen-Doped Carbon Dot\/TiO2 Hybrid Composites Induce Light-Dependent ROS-Mediated Cytotoxicity in Cancer Cells"],"prefix":"10.3390","volume":"16","author":[{"given":"Assia","family":"Azouaghe","sequence":"first","affiliation":[{"name":"Laboratory of Molecular Chemistry, Materials and Environment (LCM2E), Department of Chemistry, Faculty of Applied Sciences, University Mohamed I, Nador 60700, Morocco"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6159-3813","authenticated-orcid":false,"given":"Florence","family":"Back","sequence":"additional","affiliation":[{"name":"Section of Medicine, Department of Endocrinology, Metabolism and Cardiovascular System, University of Fribourg, Chemin Du Mus\u00e9e 5, 1700 Fribourg, Switzerland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6562-0580","authenticated-orcid":false,"given":"Walid","family":"Daoudi","sequence":"additional","affiliation":[{"name":"Laboratory of Education, Sciences and Techniques, Higher School of Education and Training of Berrechid, Hassan First University, Settat 26100, Morocco"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0147-8407","authenticated-orcid":false,"given":"Abdelmalik El","family":"Aatiaoui","sequence":"additional","affiliation":[{"name":"Laboratory of Molecular Chemistry, Materials and Environment (LCM2E), Department of Chemistry, Faculty of Applied Sciences, University Mohamed I, Nador 60700, Morocco"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"C\u00e9line","family":"Spack","sequence":"additional","affiliation":[{"name":"Section of Medicine, Department of Endocrinology, Metabolism and Cardiovascular System, University of Fribourg, Chemin Du Mus\u00e9e 5, 1700 Fribourg, Switzerland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0001-8949-9631","authenticated-orcid":false,"given":"Diana","family":"Potes Vecini","sequence":"additional","affiliation":[{"name":"Department of Chemistry, University of Fribourg, Chemin Du Mus\u00e9e 9, 1700 Fribourg, Switzerland"},{"name":"Swiss National Center for Competence in Research (NCCR) Bio-Inspired Materials, University of Fribourg, Chemin des Verdiers 4, 1700 Fribourg, Switzerland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5547-6004","authenticated-orcid":false,"given":"David","family":"Hoogewijs","sequence":"additional","affiliation":[{"name":"Section of Medicine, Department of Endocrinology, Metabolism and Cardiovascular System, University of Fribourg, Chemin Du Mus\u00e9e 5, 1700 Fribourg, Switzerland"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,8,24]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Akturk, O. (2024). Biocompatibility, Toxicity, and Immunological Effects of Functionalized Carbon Nanostructures. Handbook of Functionalized Carbon Nanostructures, Springer.","DOI":"10.1007\/978-3-031-32150-4_73"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"12736","DOI":"10.1021\/ja040082h","article-title":"Electrophoretic Analysis and Purification of Fluorescent Single-Walled Carbon Nanotube Fragments","volume":"126","author":"Xu","year":"2004","journal-title":"J. Am. Chem. Soc."},{"key":"ref_3","doi-asserted-by":"crossref","unstructured":"Cui, L., Ren, X., Sun, M., Liu, H., and Xia, L. (2021). Carbon Dots: Synthesis, Properties and Applications. Nanomaterials, 11.","DOI":"10.3390\/nano11123419"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"210","DOI":"10.1186\/s12951-024-02479-4","article-title":"Carbon dots as a novel photosensitizer for photodynamic therapy of cancer and bacterial infectious diseases: Recent advances","volume":"22","author":"Sun","year":"2024","journal-title":"J. Nanobiotechnol."},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Jovanovi\u0107, S., Markovi\u0107, Z., Budimir, M., Prekodravac, J., Zmejkoski, D., Kepi\u0107, D., Bonasera, A., and Markovi\u0107, B.T. (2023). Lights and Dots toward Therapy\u2014Carbon-based quantum dots as new agents for photodynamic therapy. Pharmaceutics, 15.","DOI":"10.3390\/pharmaceutics15041170"},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Karagianni, A., Zourou, A., Ntziouni, A., Qu, C., Terrones, M., Argirusis, C., Alexandratou, E., and Kordatos, K.V. (2026). Carbon Dots\u2013TiO2 Hybrid Nanomaterials with Enhanced Photochemical Properties and Photodynamic Therapy Activity. Processes, 14.","DOI":"10.3390\/pr14071048"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"2663","DOI":"10.1039\/D2RA07150A","article-title":"Novel N-doped carbon dots derived from citric acid and urea: Fluorescent sensing for determination of metronidazole and cytotoxicity studies","volume":"13","author":"Qi","year":"2023","journal-title":"RSC Adv."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"103","DOI":"10.1007\/s10895-019-02474-1","article-title":"Ecofriendly Synthesis of Fluorescent Nitrogen-Doped Carbon Dots from Coccinia grandis and its Efficient Catalytic Application in the Reduction of Methyl Orange","volume":"30","author":"Chandrasekaran","year":"2020","journal-title":"J. Fluoresc."},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Bhattacharya, T., Shin, G.H., and Kim, J.T. (2023). Carbon dots: Opportunities and challenges in cancer therapy. Pharmaceutics, 15.","DOI":"10.3390\/pharmaceutics15031019"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"2310587","DOI":"10.1002\/smll.202310587","article-title":"Engineering Nitrogen-Doped Carbon Quantum Dots: Tailoring Optical and Chemical Properties through Selection of Nitrogen Precursors","volume":"20","author":"Nguyen","year":"2024","journal-title":"Small"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"2162","DOI":"10.1002\/asia.201900416","article-title":"Pheophytin Derived Near-Infrared-Light Responsive Carbon Dot Assembly as a New Phototheranotic Agent for Bioimaging and Photodynamic Therapy","volume":"14","author":"Wen","year":"2019","journal-title":"Chem. Asian J."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"104370","DOI":"10.1016\/j.jddst.2023.104370","article-title":"TiO2-based nanocomposites for cancer diagnosis and therapy: A comprehensive review","volume":"82","author":"Pourmadadi","year":"2023","journal-title":"J. Drug Deliv. Sci. Technol."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"720491","DOI":"10.1155\/2012\/720491","article-title":"Enhanced Visible-Light Photocatalytic Performance of Nanosized Anatase TiO2 Doped with CdS Quantum Dots for Cancer-Cell Treatment","volume":"2012","author":"Huang","year":"2012","journal-title":"J. Nanomater."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"135","DOI":"10.1016\/j.cej.2013.02.047","article-title":"Hydrothermal synthesis of a concentrated and stable dispersion of TiO2 nanoparticles","volume":"223","author":"Souvereyns","year":"2013","journal-title":"Chem. Eng. J."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"72","DOI":"10.1007\/s10565-026-10190-3","article-title":"Titanium dioxide nanoparticles in oncology: Synthesis, application, and challenges","volume":"42","author":"Agarwal","year":"2026","journal-title":"Cell Biol. Toxicol."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"1155","DOI":"10.1089\/ars.2019.7868","article-title":"The Antioxidative Role of Cytoglobin in Podocytes: Implications for a Role in Chronic Kidney Disease","volume":"32","author":"Randi","year":"2020","journal-title":"Antioxid. Redox Signal."},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"De Backer, J., Maric, D., Zuhra, K., Bogaerts, A., Szabo, C., Vanden Berghe, W., and Hoogewijs, D. (2022). Cytoglobin Silencing Promotes Melanoma Malignancy but Sensitizes for Ferroptosis and Pyroptosis Therapy Response. Antioxidants, 11.","DOI":"10.3390\/antiox11081548"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"100165","DOI":"10.1016\/j.snr.2023.100165","article-title":"Improving the quantum yield of nitrogen-doped carbon dots by varying dopant ratios and pH","volume":"6","author":"Prado","year":"2023","journal-title":"Sens. Actuators Rep."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"622","DOI":"10.1016\/j.saa.2013.09.037","article-title":"Structural, optical and morphological analyses of pristine titanium di-oxide nanoparticles\u2013Synthesized via sol\u2013gel route","volume":"117","author":"Praveen","year":"2014","journal-title":"Spectrochim. Acta Part A Mol. Biomol. Spectrosc."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"34241","DOI":"10.1039\/C8RA06681G","article-title":"Synthesis and characterization of TiO2\/graphene oxide nanocomposites for photoreduction of heavy metal ions in reverse osmosis concentrate","volume":"8","author":"Zhang","year":"2018","journal-title":"RSC Adv."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"5723","DOI":"10.1007\/s10854-016-4484-7","article-title":"Efficient nanophotocatalyt of hydrothermally synthesized Anatase TiO2 nanoparticles from its analogue metal coordinated precursor","volume":"27","year":"2016","journal-title":"J. Mater. Sci. Mater. Electron."},{"key":"ref_22","doi-asserted-by":"crossref","unstructured":"Ghadiry, M., Gholami, M., Lai, C.K., Ahmad, H., and Chong, W.Y. (2016). Ultra-Sensitive Humidity Sensor Based on Optical Properties of Graphene Oxide and Nano-Anatase TiO2. PLoS ONE, 11.","DOI":"10.1371\/journal.pone.0153949"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"136678","DOI":"10.1016\/j.snb.2024.136678","article-title":"Dual color carbon dots for simultaneous dynamic fluorescence tracking of mitochondria and lysosomes","volume":"422","author":"Li","year":"2025","journal-title":"Sens. Actuators B Chem."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"13155","DOI":"10.1021\/acsanm.3c01885","article-title":"Nitrogen-Doped Carbon Dots with Oxidation Stress Protective Effects for Reactive Oxygen Species Scavenging on Hepatic Ischemia\u2013Reperfusion Injury","volume":"6","author":"Chen","year":"2023","journal-title":"ACS Appl. Nano Mater."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"2296","DOI":"10.1039\/D1DT03788A","article-title":"F,N-Doped carbon dots as efficient Type I photosensitizers for photodynamic therapy","volume":"51","author":"Wu","year":"2022","journal-title":"Dalton Trans."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"74","DOI":"10.1016\/j.carbon.2019.12.002","article-title":"Precise photodynamic therapy: Penetrating the nuclear envelope with photosensitive carbon dots","volume":"159","author":"Xu","year":"2020","journal-title":"Carbon"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"13139","DOI":"10.1021\/acs.langmuir.2c01857","article-title":"Light-Activated Reactive Oxygen Species-Responsive Nanocarriers for Enhanced Photodynamic Immunotherapy of Cancer","volume":"38","author":"Peng","year":"2022","journal-title":"Langmuir"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"137236","DOI":"10.1016\/j.ijbiomac.2024.137236","article-title":"Reactive oxygen species augmented polydopamine-chlorin e6 nanosystem for enhanced chemo\/photothermal\/photodynamic therapy: A synergistic trimodal combination approach in vitro & in vivo","volume":"283","author":"Pal","year":"2024","journal-title":"Int. J. Biol. Macromol."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"80","DOI":"10.1039\/D2RA06888E","article-title":"Effects of morphology and size of nanoscale drug carriers on cellular uptake and internalization process: A review","volume":"131","author":"Zhang","year":"2023","journal-title":"RSC Adv."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"e2106342","DOI":"10.1002\/smll.202106342","article-title":"Carbon Dot Therapeutic Platforms: Administration, Distribution, Metabolism, Excretion, Toxicity, and Therapeutic Potential","volume":"18","author":"Truskewycz","year":"2022","journal-title":"Small"}],"container-title":["Biomolecules"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2218-273X\/16\/9\/1229\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,8,26]],"date-time":"2026-08-26T04:25:06Z","timestamp":1787718306000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2218-273X\/16\/9\/1229"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,8,24]]},"references-count":30,"journal-issue":{"issue":"9","published-online":{"date-parts":[[2026,9]]}},"alternative-id":["biom16091229"],"URL":"https:\/\/doi.org\/10.3390\/biom16091229","relation":{},"ISSN":["2218-273X"],"issn-type":[{"value":"2218-273X","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,8,24]]}}}