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Intracellular Transport Dynamics of Endosomes Containing DNA Polyplexes along the Microtubule Network

Rajan P. Kulkarni ^*, Kenneth Castelino , Arun Majumdar  and Scott E. Fraser 

^* Option in Biochemistry and Molecular Biophysics, and Division of Biology, Division of Engineering and Applied Science, California Institute of Technology, Pasadena, California 91125; and Department of Mechanical Engineering, University of California, Berkeley, California 94720

Correspondence: Address reprints and inquires to Scott E. Fraser, Tel.: 626-395-2790; E-mail: sefraser{at}caltech.edu.

We have explored the transport of DNA polyplexes enclosed in endosomes within the cellular environment by multiple particle tracking (MPT). The polyplex-loaded endosomes demonstrate enhanced diffusion at short timescales (t < 7 s) with their mean-square displacement (MSD) x(t)² scaling as t^1.25. For longer time intervals they exhibit subdiffusive transport and have an MSD scaling as t^0.7. This crossover from an enhanced diffusion to a subdiffusive regime can be explained by considering the action of motor proteins that actively transport these endosomes along the cellular microtubule network and the thermal bending modes of the microtubule network itself.