Templated synthesis of chitosan nanocapsules with controllable shell thickness and porosity

This study demonstrates the successful production of monodispersed, homogeneous chitosan nanocapsules ranging from 600 - 750 nm in diameter. Through the use of a solid core silica template with a tunable mesoporous shell (SC/MS), hollow nanocapsules with wall thickness ranging from ca. 40 - 100 nm have been synthesized which were characterized using transmission and scanning electron microscopy. In addition, capsules with varying porosity have been produced via two methods - either by varying the amount of porogen used in the synthesis of the template, or by varying the pH conditions during the infiltration of the polymer into the template. At lower pH, the potential gradient increases which aids in greater polymer infiltration increasing the capsule wall density as well as decreasing porosity. These have been characterized using the AFM and TEM of microtomed slices of the capsules embedded in resin. The study provides a facile approach for controlling the thickness of polymer nanocapsules using a single-step method and has potential for controlled drug- and vaccine-delivery