Functionalization of Recombinant Amelogenin Nanospheres Allows Their Binding to Cellulose Materials

Abstract

Protein engineering to functionalize the self-assembling enamel matrix protein amelogenin with a cellulose binding domain (CBD) is used. The purpose is to examine the binding of the engineered protein, rh174CBD, to cellulose materials, and the possibility to immobilize self-assembled amelogenin nanospheres on cellulose. rh174CBD assembled to nanospheres ≈35 nm in hydrodynamic diameter, very similar in size to wild type amelogenin (rh174). Uniform particles are formed at pH 10 for both rh174 and rh174CBD, but only rh174CBD nanospheres showes significant binding to cellulose (Avicel). Cellulose binding of rh174CBD is promoted when the protein is self-assembled to nanospheres, compared to being in a monomeric form, suggesting a synergistic effect of the multiple CBDs on the nanospheres. The amount of bound rh174CBD nanospheres reached ≈15 mg/g Avicel, which corresponds to 4.2 to 6.3 × 10 mole/m . By mixing rh174 and rh174CBD, and then inducing self-assembly, composite nanospheres with a high degree of cellulose binding can be formed, despite a lower proportion of rh174CBD. This demonstrates that amelogenin variants like rh174 can be incorporated into the nanospheres, and still retain most of the binding to cellulose. Engineered amelogenin nanoparticles can thus be utilized to construct a range of new cellulose based hybrid materials, e.g. for wound treatment.

Temperature and pH Controlled Self‐Assembly of a Protein–Polymer Biohybrid

“…Successful formation of the protein–polymer bioconjugate was verified by SDS‐PAGE ( Figure a). The strong band in lane 1 corresponded to AMEL before any functionalization . This band hardly changed after the attachment of the initiator molecules (lane 2), which was reasonable in consideration of the negligible molecular weight of the initiator molecules compared to proteins.…”

“…Additionally, its purification is facile and can be achieved by utilizing its unique pH solubility profile . The recombinant production also allows for protein engineering, making it possible to add new functionalities to AMEL and its self‐assembled nanospheres …”

Nanobiopolymers Fabrication and Their Life Cycle Assessments

“…In these nanobiopolymers, nanocelluloses has incomparable mechanical performance with modulus reach 100‐160 GPa, but its in vivo biodegradability is inferior to other biopolymers (Table ). In addition, nanocellulose, nanochitin, nanosilk, and nanostarch appear as aqueous dispersion, thus can only be processed via solution‐based methods, such as solution casting, vacuum filtration and freeze drying . In contrast, most microbial nanobiopolymers, polyesters for example, are thermoplastic, thus can be processed using polymer processing equipment, like extruder, injection molding, etc.…”