(617d) A Novel Method of Spatially Controlled Vesicle Capture Using Hydrophobically Modified Chitosan in Breath Figures

Breath Figures are a morphological class of porous polymers with highly ordered structures. They can be fabricated by simply casting a polymer solution in a volatile organic solvent under humid conditions. The cooling effect produced by the solvent evaporation leads to condensation of water droplets on the surface. These ordered arrays of droplets stay apart and once they sink inside the polymer solution, more water droplets condense on the surface around which a polymer film forms. Upon complete evaporation of the solvent and water, pore formation takes place. We hypothesized that if we used an aerosol mist carrying cargo instead of humid air, we could place the contents of the mist exclusively in the ordered pores of the breath figures.

We synthesized breath figure films by spin coating a solution of polystyrene by exposing them to a humid aerosol mist of a solution of hydrophobically modified chitosan (HMC) as they spun. HMC stayed in the condensed water droplets and as the droplets evaporated, the HMC deposited only inside the pores of the breath figures. The mechanism of the formation of these HMC microarrays will be discussed. Once the HMC was deposited selectively in the pores, it was used to capture liposomes in the pores. HMC is fabricated by covalently attaching alkyl groups to the chitosan backbone. The spatially ordered vesicle capture was facilitated by the hydrophobes attached to the chitosan backbone in HMC as they have a tendency to insert themselves in the bilayer hydrophobic region of the liposomes. This lead to tethering of the liposomes only inside the pores which was confirmed by epifluorescent, confocal and electron microscopy. Furthermore, cryo scanning electron microscopy analysis showed that these captured vesicles were intact. Thus a simple process to fabricate a highly ordered polymer film for spatially controlled vesicle capture is realized. The technique employed does not require the use of any lithography based procedures and is easy to scale as it is based on an aerosolization method. The low cost of the materials make this as a strong candidate for sensing applications which require the capture of any type of vesicles for example cells, liposomes, exosomes etc. This work was supported by the National Science Foundation.