Development of Functionalized Protein Materials

Sammanfattning: Many proteins are available as side-streams from food production, and in some cases even from industrial waste-streams. This means that proteins are available in large scale and at a relatively low price. As protein are highly complex molecules it is interesting to try to use protein as starting materials in for applications in materials science. Most proteins have the ability to self-assemble into nanofibrils. These fibrils have a regular repeating substructure that consists of β-strands running perpendicular to the fibril axis, resulting in cross-β sheets that run parallel along the fibril axis. The extended β-sheets structure results in the formation of hydrophobic grooves that can act as potential binding sites organic molecules. This means that the functionality of the material may be modified by addition of e.g. light emitting molecules or drug molecules. By such functionalization the protein material may accordingly be suitable for applications such as light-conversion materials (e.g. for use as coatings of light emitting diodes (LEDs)) or for drug-delivery. For such applications, the protein fibrils must be processes into macroscopic structures such as films or gels.  Against this background, we employ the food proteins hen egg white lysozyme and β-lactoglobulin as model proteins for fibrillation and functionalization. Through a mechanochemical process the hydrophobic dyes can conveniently be combined with proteins, that can be converted into functionalized protein nanofibrils by liquid-phase self-assembly. By employing protein fibrils functionalized with three dyes, we have been able to form films that enables conversion of UV light to white light (and can thus be employed as a coating on UV-LEDs) with protein fibrils functionalized with multiple dyes. By mixing biodegradable polymers with functionalized protein fibrils, luminescent bioplastic films can be prepared that are processable when wet; a cut film will also self-heal if water is applied. We have also turned functionalized protein fibrils into gel states, including hydrogels or aerogels. In the case of protein fibrils functionalized with Hydantoins (a type of drug molecule) hydrogels were prepared, and the release of the drug was investigated. In addition, aerogels can be prepared from hydrogels by freeze drying, and in this manner lightweight functionalized aerogels are achieved. By functionalization with an electrically conductive polymer, an elastic conductive aerogel is formed that employed as a piezoelectric pressure sensor. In summary a wide range of materials have been prepared suitable for various applications demonstrating the flexibility of the developed functionalization methodology and that the structural richness of protein self-assembly can be employed to prepare a wide variety of types of materials of varying functionality.