Influence of upconversion nanoparticles on the refractive properties of tumor tissue under photodynamic therapy

Background and Objectives: To develop and improve the efficiency of minimally invasive cancer therapy methods, accurate data on the optical properties of biological tissues and their changes after photodynamic therapy using upconversion nanoparticles (UCNPs) of various types are required. One of the optical methods proposed for diagnostics and assessment of tumor tissue development is the method of multiwave refractometry. Materials and methods: In the presented study, a model of alveolar liver cancer (cholangiocarcinoma, PC1) development in rats was used. Photodynamic therapy was carried out using 5 different UCNPs. The refractive index was measured on an Abbe DR-M2/1550 multiwave refractometer (Atago, Japan). Results: The dispersion dependence of tissue samples of model alveolar liver cancer was analyzed in the spectral range of 480–1550 nm after the introduction of 5 different types of UCNPs, as well as after photodynamic therapy. According to the obtained result, the highest value of the Abbe number (53.67 $\pm$ 0.68) is characteristic of intact tumor tissue, while UCNPs lead to a decrease in the Abbe number (53.29 $\pm$ 0.69), an even lower value of the Abbe number (53.12 $\pm$ 0.69) is observed in tissue samples from groups of animals after photodynamic therapy. Conclusions: The results presented in this paper have shown that the introduction of UCNPs of various types and the use of photodynamic therapy cause a change in the refractometric properties of tissues. The presented results can be useful for many methods of laser therapy and optical diagnostics of skin diseases and localization of subcutaneous tumors.