Controlling Transport Using Surface Porosity in Colloidosomes
Rachel Rosenberg
Colloidosomes are a hydrophilic encapsulation device, analogous to liposomes or
polymersomes, where a hollow or polymer-gel core is encased in a shell of self-assembled,
packed colloidal particles. The porosity of the shell is determined by the spacing between the
particles, which can range from nanometers to microns, set by the colloidal particle size and
packing density. Colloidosomes have a wide range of applications and various advantages over
other encapsulation methods, including the ability to control surface porosity, mechanical
stability, and 100% encapsulation efficiency. In this work we characterize the transport through
colloidosome shells, where gel-based cores are fabricated through use of microfluidic devices
and electrostatic forces facilitate adhesion of the colloidal particles to form the shell.
The colloidal shell can inhibit transport through two mechanisms: a reduction in area
available for transport, since diffusants cannot penetrate the colloidal particles, as well as slower
transport through the colloidosome shell, where transport may be reduced by size exclusion. For
loosely packed shells, our experiments show that the reduction in transport (when compared to
an uncoated gel) is largely independent of particle size. This is in contrast to previous studies,
where the transport through densely packed monolayer shell, or through multi-layered ones, was
found to vary with the colloidal particle dimensions. The predictions of the theoretical model we
derived are in excellent agreement with all experimental observations, and can be used to tailor
transport through colloidosome shells in applications ranging from cellular implantation to
cosmetics.