Intracellular segregation of microparticles
Poornima Kolhar1, and Samir Mitragotri1,2
1
Biomolecular Science and Engineering, 2Department of Chemical Engineering, University of
California, Santa Barbara CA 93106, poornima.kolhar@umail.ucsb.edu
Abstract: Particulate drug delivery has received significant attention in the last few
decades. The effect of particle properties such as size, shape and surface properties on
particle-cell interaction has been studied. Here, we investigated intracellular accumulation
and subsequent spatial segregation of spherical and rod shaped microparticles.
We observed that both spherical and rod shaped particles exhibited perinuclear
accumulation. However, binary mixtures of particles were spatially segregated in the
cytoplasm based on their shape and size. When biparticle mixtures of spherical particles
were incubated on the endothelial cells, larger particles accumulated closer to the nucleus
in the perinuclear region compared to the smaller particles (Figure 1a). To further
investigate the segregation phenomenon, we incubated the cells with non-spherical
particles. Elongated polystyrene particles were fabricated using the film stretching method
developed in our lab. During the stretching process the volume of particles remains
constant.
Figure 1 (a) segregation 3µm and 1µm spheres (b) segregation of 3 µm spheres and rods
stretched from them
A sticking segregation pattern was also observed when elongated particles and spherical
particles of equal volume were incubated (Figure 1b). These experiments revealed that the
height of the particles was the most important parameter in the intracellular segregation.
The segregation force generated due to the height of the particle is higher for a taller
particle causing larger particles to be pushed towards the nucleus.
This observation throws more light on the intracellular organization and importance of
the size and shape of various organelles. Observing internalization and transport of various
sized and shaped particles can provide a new biophysical tool to study the cellular forces
and cellular transport.