Optical labeling of individual melanoma cells using photoconvertible microparticles

Background and Objectives: Photoconvertible markers are a useful approach for conducting complex fundamental and applied research in medicine and biology. Usually, photoconvertible proteins or dyes are used for this, but have some disadvantages (low stability, requirement for genetic modification, etc.). The goal of this research was to develop safe and stable photoconvertible markers for cell application. Materials and Methods: The polymer markers were obtained from polyelectrolyte microcapsules under hydrothermal synthesis with fluorescent dye rhodamine B. The spectral properties were studied using confocal microscopy and spectrometry. Results: Photoconversion of microparticles under the influence of laser irradiation was carried out due to the ability of rhodamine B molecules to hypsochromic shift the emission band, catalyzed by carbon structures formed in the shells of microparticles during hydrothermal synthesis. Hydrothermal synthesis also significantly changed the size and shape of microparticles. The thermally treated polyelectrolyte microparticles had high stability and a bright fluorescent signal. The microparticles were actively internalized by the B16F10 mouse melanoma cell line, providing labeling for 70$\%$ of all cells in the population at a ratio of 10 microparticles per cell. At the same time, metabolic activity did not decrease below 85$\%$, and the morphology and ability of B16F10 cells to synthesize melanin remained within normal limits. It has been shown that microparticles can be safely photoconverted inside B16F10 cells under laser irradiation. Conclusion: The proposed strategy is useful for complex studies on the behavior of individual melanoma cancer cells in genetically and phenotypically heterogeneous populations, and also for studying a metastatic process.