Characterization of Cytoskeletal Pore Size Using Quantum Dots

Cytoskeletal pore size is a key factor in determining the intracellular molecular transportation, yet it is technically challenging to investigate correlations between the cytoskeletal pore size and cytoplasmic diffusion. Here, we report the application of quantum dots (QD) to measure the cytoskeletal pore size. QDs are first transfected into a cell, leading to different sizes of QD-encapsulating vesicles. The distribution of QD vesicles in cells reflects the cytoskeletal pore size. Further, we can predict the cytosolic viscosity from the measured pore size using the poroelasticity scaling theory. This predicted cytosolic viscosity is verified by measuring Brownian motions of the QDs in cells and transforming the motion characteristics into cytosolic viscosity via the Stocks-Einstein relation. This strategy also provides a practical method for quantifying the cytoskeletal pore sizes. Together, this research demonstrates the efficacy of applying QDs in further studies of intracellular physical properties that play key roles in intracellular molecular transports.