doi:10.1002/adfm.202600051engEncinas-Gimenez, MiguelGarcia-Peiro, Jose I.Hueso, Jose L.Caleiras, EduardoNotario, LauraHornos, FelipeMartin-Duque, PilarDe la Vieja, AntonioSantamaria, JesusUltrasmall Platinum Nanoparticles for Radiation‐Enhanced Cancer TherapyART-2026-148948Despite decades of intense research, cancer remains a major global health challenge, with a clear need for new and more efficient therapies. Among emerging approaches, high atomic number (Z) nanomaterials capable of modulating the interaction between radiation and matter have attracted growing interest as radiotherapy enhancers. In this work, ultra‐small Platinum‐based nanoparticles with a metallic core diameter of 2–3 nm were synthesized from H2PtCl6 using polyvinylpyrrolidone as stabilizer. This nanomaterial exhibits low acute toxicity, catalase‐like activity and enhances DNA damage under pre‐clinical X‐ray irradiation, increasing the antitumoral effect of X‐ray alone. In vitro and in vivo studies, including intratumoral and intravenous administration, demonstrate improved tumor control and prolonged survival without detectable systemic toxicity under the tested conditions, establishing ultra‐small Pt‐nanoparticles as efficient materials for radiotherapy enhancement.2026http://zaguan.unizar.es/record/17044910.1002/adfm.202600051http://zaguan.unizar.es/record/170449oai:zaguan.unizar.es:170449info:eu-repo/grantAgreement/ES/AEI/PID2023-148732NB-I00info:eu-repo/grantAgreement/ES/UZ-DGA/T57-23Rinfo:eu-repo/grantAgreement/EC/H2020/742684/EU/Catalytic Dual-Function Devices Against Cancer/CADENCEThis project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No H2020 742684-CADENCEinfo:eu-repo/grantAgreement/ES/ISCIII-FEDER/CIBER-BBNinfo:eu-repo/grantAgreement/ES/MICIU/CEX2023-001286-SAdvanced Functional Materials (2026), e00051 [24 pp.]byhttps://creativecommons.org/licenses/by/4.0/deed.esinfo:eu-repo/semantics/openAccess