Carriers based on upconversion nanoparticles (UCNPs) and cyanine dye are suitable for theranostic application in oncology, although care must be taken for selection of the surface coating material, UCNP surface charge, size, and dosage of the material. Investigation of influence of annealing temperature of particles on the upconversion luminescence properties and cytotoxic effect are relevant. The present work demonstrates the assessment of cytotoxicity UCNPs unannealed and annealed at 550 oC on different normal and cancer murine cell lines in vitro. The cell viability is scored for cytotoxic effects of UCNPs at dark conditions. UCNPs provide a dose-dependent and time-dependent cytotoxic effect on all studied cell lines which was most pronounced for the Raw264.7 cell line. It is probably caused by the high phagocytic activity of macrophages. The statistically significant differences in cell viability after 24, 48 and 72 h of incubation of cells with particles were observed just for the macrophage cell line. It is also worth noting that annealed particles are less toxic than unannealed ones.
The present work demonstrates the assessment of cytotoxicity upconversion nanoparticles (UCNPs) coated by SiO2 on different normal and cancer murine cell lines in vitro. The cell viability is scored for cytotoxic effects of UCNPs at dark conditions. UCNPs coated by silica shells provide a dose-dependent cytotoxic effect on all studied cell lines which was most pronounced for the Raw264.7 cell line. It is probably caused by the high phagocytic activity of macrophages. The less sensitive cell line was 4T1. The statistically significant differences in cell viability after 24 and 48 h of incubation of cells with particles were observed just for the macrophage cell line. It is worth notifying that after 48 h of incubation the cytotoxic effect on Raw 264.7 cell line increased which shows a possible negative effect on some subpopulations on blood cells. The obtained results confirm a high sensitivity of the UCNPs to the concentration variations within cells. Carriers based on UCNPs and dyes are promising alternatives to photosensitizer for traditional photodynamic therapy and possess prominent potentials in biological and clinical applications.
The luminescence spectra of upconversion NaYF4:Yb, Er nanoparticles located under layers of biological tissue of different thickness were experimentally obtained. Luminescence of the particles was excited by laser radiation with a wavelength of 980 nm through a layer of biological tissue. The radiation power was 0.5 W. Luminescence was collected using a collimator with an aperture of 0.15 located at a distance of 20 cm from the sample. The spectra were recorded using a QE 65000 spectrometer (Ocean Optics, US). As the tissue samples, layers of rat skin, muscle and adipose tissue were used. The thicknesses of the samples were varied in the range of 1-2 mm. Distortions of the luminescence spectra resulting from its attenuation in an absorbing-scattering sample are shown. The dependences of distortions on the type and thickness of the sample, as well as on the luminescence wavelength, are obtained. The results obtained are important in determining the temperature of nanoparticles from the luminescence spectra, since the distortions of the spectra lead to an error in determining the temperature.
The present work demonstrates the temperature dependences of the spectral characteristics of the skin measured in vitro. Changes in the spectral characteristics of the rat skin upon skin heat treatment at elevated temperatures have been characterized. The spectra were recorded with a stepwise increase in temperature in the range of 25-70ºC, as well as in the process of keeping the sample at a fixed temperature for 60 min. The dynamics of the changes in collimated transmittance of rat skin is shown to be temperature-dependent. It is assumed that the changes in spectral characteristics of the skin might be caused by changes in the size and refractive index of the scatterers.
When administered into the bloodstream, upconversion nanoparticles used in therapeutic / diagnostic purposes can affect red blood cells. In this work, using light optical microscopy, we show that the removal of citrate groups from the surface of NaYF4: Er3+ , Yb3+ nanoparticles synthesized by the hydrothermal method prevents the formation of large clod-like aggregates from a suspension of washed rat erythrocytes incubated with the nanoparticles. However, the tendency toward a change in cell shape with an increase in nanoparticles concentration is still manifested.
Temperature dependences of the spectral characteristics of the rat skin, muscle and fat tissues were obtained in vitro. The changes in the spectral characteristics of the rat skin subjected to 60 min thermal treatment at elevated (>40°C) temperatures have been characterized. The dynamics of the changes in collimated transmittance of rat skin at elevated temperature is shown to be temperature-dependent. It is assumed that the changes in spectral characteristics might be caused by changes in light scattering regime within the sample.
The excitation power dependence of upconversion luminescence intensity and temperature sensing characteristics are investigated in the NaYF4 : Er3 + , Yb3 + @ SiO2 particles synthesized in-house using a hydrothermal method. The effect of laser-induced heating of the upconversion particles is shown, which introduces distortions in the measured power and temperature dependences of the upconversion luminescence. We propose a technique for calibrating the temperature dependence of upconversion particle luminescence, which should improve the accuracy of temperature measurements. The technique is based on the stabilization of upconversion particles temperature, which provides the suppression of laser-induced heating of upconversion particles.
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