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Background and Objectives: The object of the study was the cytotoxicity of various types of coated upconversion nanoparticles. The aim is to overview the literature on the cytotoxicity of various types of upconversion nanoparticles without/with coating and to search for their maximum permissible concentration when applied to cell. Materials and Methods: The approach used has been the analysis of recent publications on the topic. Results: Upconversion nanoparticles are promising for fluorescence imaging and cancer therapy. Nanoparticles with additional shells or functionalized by surface coating with targeted or photoactive molecules are considered. The toxicological effect of nanoparticles on living organisms is of decisive importance when they are used in therapy or diagnostics. The “dark” cytotoxicity of particles is considered. The cytotoxicity of particles depends on the total number of nanoparticles that have penetrated into the cell. Conclusion: Based on the analysis of a large number of publications, it can be concluded that nanoparticles coated with silicon dioxide (SiO2) are characterized by the least cytotoxic effect, which opens up prospects for the use of this type of nanoparticles in medical practice.

Background and Objectives: Knowledge of the optical and thermal human tissues properties is essential for optimizing laser therapy and optical diagnostics. Most studies are carried out at room temperature of the sample. At the same time, it is known that the optical properties of biological tissues depend on temperature even in the physiological temperature range, that is, in the range of normal functioning of the body. Accordingly, there is a possibility that the use of literature data will lead to an incorrect assessment of the conditions for the propagation of light through biological tissue in a living object. Incorrect data on the optical properties of biological tissues at physiological temperature can lead to unreliable results in medical optical diagnostics or therapy. Therefore, studies of the temperature dependences of the optical properties of biological objects are undoubtedly topical. This work shows the differences in the optical properties of rat muscle tissue before and after heating the samples to physiological temperature. Materials and Methods: The spectra of collimated transmission, total transmission and diffuse reflection of rat muscle tissue were recorded. The spectra were recorded at 25°C (room temperature) and 38–39°C (physiological temperature). For each measured point of the sample, the spectral dependences of the absorption coefficients, transport scattering coefficient, and anisotropy factor of the studied samples were calculated. Results and conclusion: It has been shown that the optical properties of muscle tissue differ for room and physiological temperatures. In this case, the absorption and scattering coefficients practically do not change. The main parameter that changes with temperature is the anisotropy factor. This change also leads to a change in the transport scattering coefficient.

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.