On the incorporation of functionalities into hydroxyapatite capsules.

Abstract

Nature is capable of building materials with tailor-made properties under ambient conditions for specific applications. We apply some of the basic building principles of biomineralization in this paper: we stabilize an oil/water emulsion with the protein hydrophobin and mineralize this emulsion, resulting in hollow mineral capsules. The use of an emulsion as a liquid template enables precise size control over the final capsules. We mimic nature by using complexing agents and surfactants as additives to alter the properties of the growing mineral. We also modify the mineral itself by addition of different cations. Furthermore, we show the inclusion of silver into the capsules. This should add antibacterial properties to the capsules and shows exemplarily that catalytically active metals can be included. While the manual process needs numerous working steps and long waiting times, we ease the whole process by automation and use phosphatases to shorten synthesis time. Our experiments show the flexibility and adaptability of our system, making it an ideal platform for various possible applications such as drug transport and especially as microreactors.