Direct optical trapping of T cells

Since the first optical trap was reported in the late 1970s it has been shown to be a hugely versatile tool when it comes to biological applications and Life Science research. As the number of applications increases and the optical trapping technology becomes more advanced there is an increasing need to be able to perform accurate, quantitative experiments that directly trap the cell of interest without the need to introduce exogenous beads into the sample. The issue with trapping cells directly is that they are often larger than beads and are distinctly non-uniform with varying refractive indices. This has practical implications in terms of trapping the cell as a whole rather than just a small feature of the cell, preventing the cell from re-orientating during experiments and, most importantly, performing reliable measurements on the sample and cell which most often involves accurately tracking the cell’s position. I will present a series of experiments and mathematical models that aim to address these issues, highlighting novel beam shapes that can be used to trap the cell as a whole and fluorescent imaging techniques that allowing accurate cell position tracking. My interest is in optically trapping T cells, which are part of the immune system, although the approaches presented are not limited to T cells and could easily be adapted to suit the sample of interest. Using the techniques developed I will demonstrate how optical tweezers can be used probe the dynamic interactions that occur between cells in the adaptive immune system.