Protein–mineral hybrid capsules from emulsions stabilized with an amphiphilic protein

Biomineralization comprises a most promising process to produce novel materials in an energy-efficient way. We present a straightforward route for the production of hybrid capsules composed of the amphiphilic protein hydrophobin and hydroxyapatite; the synthesis is water-based and can be performed without toxic ingredients. Emulsion droplets stabilized with hydrophobin serve as templates for the growth of a mineral shell, permeable for small molecules. The system is sensitive to the choice of oil and the mineralization time, offering ample opportunities to tune capsule properties like shell thickness and morphology. The mineral phase as well as the behaviour of the capsules upon thermal treatment is investigated. The resulting capsules could find applications as microreactors or in the field of drug delivery.