Buffer modification: A case study with polystyrene beads, DU145-, and MCF7 cell lines

Abstract: Separation of cancer cells gives advantages in understanding the disease, guiding treatment decisions, and facilitating drug development. Overall, separation plays an important role in biological research. Acoustophoresis is a technique that utilizes acoustic waves to separate particles and cells suspended in a buffer medium. The efficiency of this separation process depends on the relative acoustic mobility of the cells and particles compared to the buffer medium. Factors such as density, size, and compressibility determine the mobility ratio, with a higher ratio indicating better separation. In this thesis, the mobility ratios between the particles and cells targeted for separation were evaluated, with the goal to select the optimal buffer medium that yields the highest separation. Polystyrene beads, DU145 prostate cancer cells, and MCF7 breast cancer cells were used for the experiments. By optimizing the buffer medium, the acoustic mobility of the particles and cells was modified. One of the findings was that the most effective buffer medium for separating polystyrene beads in varying sizes was determined to be 20\% Iodixanol, highlighting differences in material properties between the beads. For DU145 cells, the addition of Iodixanol to the buffer resulted in optimal separation from the polystyrene beads. Except in the case of 4.99 $\mu$m beads, where PBS proved to be the optimal buffer medium. For MCF7 cells, a sign change for the acoustic contrast factor was obtained when adding 10\% and 20\% Iodixanol to the buffer, indicating optimal separation. With this knowledge, the behaviour of these cell lines are clearer and future research can be made in order to obtain separation between these cells and other cells.