Treballs Finals de Grau d'Enginyeria Biomèdica. Facultat de Medicina i Ciències de la Salut. Universitat de Barcelona. Curs: 2020-2021. Director: Amy Beedle, Tutor: Pere Roca-Cusachs Soulere.Cells in our body are constantly sensing and generating forces through the cytoskeleton. The
cytoskeleton is a network of protein filaments that mechanically connects the cells to their substrate and
to their nucleus, thus allowing the transmission of mechanical stimuli from the membrane of the cell to
the nucleus. More importantly, mechanical forces acting on the nucleus can trigger changes in gene
expression and regulate cell behaviour. A recent finding indicates that fibrillar adhesions, a type of cellsubstrate
adhesions located under the nucleus, alter the transmission of mechanical stimuli from the
membrane of the cell to the nucleus, making the nucleus less susceptible to mechanical perturbations.
Here, we hypothesise that they do it by tuning the mechanical properties of the cytoplasm. In order to
test this hypothesis, we first develop a protocol to acquire microrheological measurements of the
cytoplasm with an optical tweezers setup by following three steps: (1) defining a protocol to allow cells to
internalise optical tweezers beads in their cytoplasm; (2) establishing a method to acquire
microrheological measurements of the cytoplasm with an optical tweezers setup and, furthermore,
proving the correct functioning of the system by adding a control that tunes its mechanical properties; (3)
implementing a MATLAB program to automatically display and statistically test the data obtained. Once
the system is optimised, we measure the mechanical properties of the cytoplasm with and without fibrillar
adhesions and we find that cells with fibrillar adhesions exhibit a softer cytoplasm, suggesting a
mechanism by which fibrillar adhesions can shield the nucleus from external mechanical perturbations
