Microcapsules with Protein Fibril-Reinforced Shells

Layer-by-layer adsorption of oppositely charged polymers on template particles is a well-established and extensively studied process for the formation of core-shell microcapsules. In this chapter we discuss how this process can be used to create microcapsules with a nanocomposite shell, consisting of layers of negatively charged flexible biopolymers (polysaccharides and polysaccharide–protein complexes), reinforced with stiff positively charged protein fibrils. The nanocomposite shell formed by these components has a mechanical strength which far exceeds the strength of shells consisting of flexible synthetic polymers. By using emulsion droplets as template particles, the size of the microcapsules can easily be controlled by the power input in the primary emulsification step. The structure of the shell was examined with both electron microscopy and confocal scanning laser microscopy. Mechanical strength was determined using temperature ramp tests. The release of hydrophobic probe molecules from the capsules was examined with proton transfer reaction–mass spectrometry.