Introduction. Improving the accuracy, effectiveness, and safety of magnetic contrast media for MRI diagnostics is an urgent task for both clinical medicine and researcher. Therefore, the introduction of new innovative drugs opens up additional opportunities for assessing the functional state of organs and tissues, significantly increasing the accuracy of diagnosis and the effectiveness of treatment.

Materials and methods. The parameters of acute toxicity, species and sexual sensitivity to an innovative drug containing gadolinium nanoparticles stabilized with arabinogalactane (GD-AH) and a commercial drug for MRI studies, Gadodiamide (a reference drug), were evaluated using the intragastric route of administration in outbred rats of both sexes at a dose of 2000 mg/kg body weight (b.w.). Additionally, acute toxicity assessment for the innovative drug GD-AG was performed with intraperitoneal administration in mice at doses of 2000 and 300 mg/kg b.w.

Results. Intragastric administration of Gadodiamide and the innovative Gd-AG nanocomposite to rats of both sexes caused neither the death of animals nor changes in internal organs during macroscopic examination. Intraperitoneal administration of 2000 mg/kg b.w. GD-AG to mice resulted in 100% death. A dose of 300 mg/kg b.w. did not cause death, but macroscopic changes in internal organs were observed.

Limitations. The study is limited to studying the acute toxicity parameters of an innovative drug containing gadolinium nanoparticles stabilized with arabinogalactane (GD-AG) and a commercial drug for MRI studies, Gadodiamide.

Conclusion. According to the toxicometric parameters of acute toxicity, the average lethal doses for intragastric administration of the commercial drug Gadodiamide and the innovative nanocomposite Gd-AG to rats do not differ from each other and are definted as >2000 mg/kg b.w., which characterizes them as substances with a low risk of acute toxicity (hazard class V). The average lethal dose for the intraperitoneal route of administration of Gd-AG nanocomposite is in the range of 300 mg/kg b.w. < LD50 < 2000 mg/kg b.w., which belongs to the IV class of acute toxicity according to the classification of K.K.Sidorov and is defined as a substance with low toxicity.

Compliance with ethical standards. The study was approved by the local Ethics Committee of the FSBSI VSIMEI (Protocol No. 8 dated 12/15/2023), conducted in accordance with the European Convention for the Protection of Vertebrate Animals Used for Experiments or Other Scientific Purposes (ETS N 123), Directive of the European Parliament and of the Council of the European Union 2010/63/EC dated 09/22/2010 on the protection of animals used for scientific purposes.

Contribution: Sosedova L.M. – research concept and design, statistical data processing, text writing, editing; Novikov M.A. – data collection and processing, statistical data processing, text writing; Titov E.A. – literary study, data collection and processing, statistical data processing; Pankova A.A. – data collection and processing, statistical data processing; Vokina V.A. – data collection and processing, statistical data processing, text writing; Konkova T.V. – data collection and processing, synthesis of nanocomposite, statistical data processing; Sukhov B.G. – research concept and design, editing. All authors are responsible for the integrity of all parts of the manuscript and approval of the manuscript final version.

Conflict of interest. The authors declare no conflict of interest.

Funding. The research was supported by a grant from the Russian Science Foundation. Project No. 25-25-00036 "Toxicity and diagnostic properties of a promising contrast agent containing gadolinium nanoparticles encapsulated in an arabinogalactan polymer matrix".

Received: July 8, 2025 / Accepted: October 15, 2025 / Published: April 17, 2026