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In vivo liquid biopsy, especially using the photoacoustic (PA) method, demonstrated high clinical potential for early diagnosis of deadly diseases such as cancer, infections, and cardiovascular disorders through the detection of rare circulating tumor cells (CTCs), bacteria, and clots in the blood background. However, little progress has been made in terms of standardization of these techniques, which is crucial to validate their high sensitivity, accuracy, and reproducibility. In the present study, we addressed this important demand by introducing a dynamic blood vessel phantom with flowing mimic normal and abnormal cells. The light transparent silica microspheres were used as white blood cells and platelets phantoms, while hollow polymeric capsules, filled with hemoglobin and melanin, reproduced red blood cells and melanoma CTCs, respectively. These phantoms were successfully used for calibration of the PA flow cytometry platform with high-speed signal processing. The results suggest that these dynamic cell flow phantoms with appropriate biochemical, optical, thermal, and acoustic properties can be promising for the establishment of standardization tool for calibration of PA, fluorescent, Raman, and other detection methods of in vivo flow cytometry and liquid biopsy. [ABSTRACT FROM AUTHOR]

Label-free characterization of cell subpopulations is a very promising biomedical approach. Nowadays, there are several label-free methods based on different physical properties such as size, density, stiffness, etc. allowing the characterization of biological objects. However, fluorescence properties are the most suitable feature for the label-free study of tissue and cells. Understanding the autofluorescence level peculiarities of normal and pathological / live and dead cells can become a helpful tool for cells' metabolic activity, viability evaluation, and diagnostics of a number of diseases. In this study, we applied a series of mouse cell lines (RAW 264.7 - macrophages, L929 - fibroblasts, C2C12 – myoblasts, and B16-F10 – melanoma) to compare cell autofluorescence of live and dead cells under 488 nm laser excitation and found the difference between their autofluorescence depending on a cell state and type. [ABSTRACT FROM AUTHOR]