Biomimetic engineering of a fortified ice composite with enhanced mechanical properties.

This work presents BioPykrete, a high-performance sustainable bio-composite engineered from ice, cellulose nanocrystals (CNC), and a custom chimeric protein designed to facilitate interfacial adhesion. By genetically fusing the ice-binding protein AFPIII with the carbohydrate-binding module CBM3a, we developed a chimeric protein to act as a molecular "bioadhesive" bridging the crystalline reinforcement phase to the ice matrix. During the controlled solidification of the suspension, the CBM3a-AFPIII chimera is proposed to regulate the self-organisation of the CNC fibers into a reinforcing 3D network that encloses ice within micro-scale cells, a structural hierarchy that appears to arrest crack propagation at the pore level, enabling BioPykrete to bypass the characteristic sudden brittle failure of pure ice in favor of a gradual (progressive) ductile-like mechanical failure. Mechanical characterization via unconfined compression and fracture energy analysis reveals that BioPykrete achieves a 10-fold increase in compressive strength and a 70-fold increase in energy-to-failure compared to standard ice, with the addition of the chimera protein doubling both the strength and the energy-to-failure relative to an otherwise identical CNC-ice composite lacking the chimera. With compressive strength approaching that of concrete, BioPykrete is a promising proof-of-concept for a biodegradable, potentially low-carbon-footprint composite for Arctic environments, where traditional construction is economically and environmentally challenging. Establishing its suitability for infrastructure will require further durability, freeze-thaw, creep, and life-cycle testing. These results demonstrate that the engineering of multi-domain protein chimeras provides a powerful toolkit for the molecular-level manipulation of composite properties, paving the way for a new generation of "smart" biomimetic materials.