Layer-by-layer assembly of -casein amyloid fibrils for the preparation of hollow microcapsules

Abstract

Amyloids are known to self-assemble into fibril forms derived from natural or artificial proteins exhibiting superior mechanical properties, stability, and biocompatibility. However, few studies have investigated the applications of amyloid fibrils. Herein, the layer-by-layer growth of zwitterionic -casein amyloid fibrils (CFs) to prepare stable hollow microcapsules is investigated, which is potentially applicable to drug delivery systems. The growth of CFs increases linearly when electrostatic interactions between the constituent pair become more prominent, for instance, cationic CFs paired with poly(sodium 4-styrenesulfonate) (PSS), and anionic CFs paired with poly(diallyldimethylammonium chloride). In contrast, the increase in film thickness shows the exponential-to-linear transition when hydrogen bonding is responsible for adsorption between cationic CFs and poly(acrylic acid) (PAA). It is thus concluded that stable CF/PSS hollow microcapsules are prepared by using the electrostatic interaction. However, the CF/PAA hollow microcapsules are ruptured due to the breakage of hydrogen bonding upon removal of sacrificial templates.