Toxicity of upconversion nanoparticles. Overview

Background and Objectives: The object of the study was the toxicity of upconversion nanoparticles. The aim is to overview the literature on the toxicity of various types of upconversion nanoparticles and to search for their maximum permissible concentration when administered to laboratory animals in vivo. Materials and Methods: The approach used has been the analysis of recent publications on the topic. Results: Upconversion particles are promising for visualization of the structure of biological tissues and organs in fluorescent light, as well as for use in diagnostics of diseases and photoinduced therapy. Nanoparticles with additional shells or functionalized by surface coating with targeted or photoactive molecules, allowing the creation of particles with several modalities, are considered. The phototoxicity of such particles is considered separately. When using nanoparticles for therapy or diagnostics of the state of living objects, the issue of toxicity is urgent. The toxic effect of upconversion nanoparticles on the body depends on their concentration upon administration, as well as on the total amount of nanoparticles correlated with the body weight. Conclusion: From the considered concentration dependences, based on the results of histological and biochemical studies, it was shown that, as a rule, no noticeable toxicity was observed in such particles, and the maximum permissible concentration of particles can be considered 2 mg/ml.