Abstract:

Biological materials can grow, catalyze reactions, and adapt to their environment. Harnessing these functions within artificial systems requires integrating bio-derived components into hybrid materials with tunable mechanical and stimuli-responsive properties. A key challenge is that most biological systems demand mild aqueous conditions for stability, whereas synthetic polymers are commonly processed under harsh conditions such as melt extrusion or organic solvent casting. To expand the design space of biohybrids and biocomposites, robust biological building blocks are essential. Bacillus subtilis spores provide such a foundation, as they withstand dehydration, organic solvents, ultraviolet irradiation, and extreme temperatures. Building on these attributes, we developed spore-based biohybrid composite materials with tunable and robust mechanical properties, achieved through rationally designed synthetic polymers and their controlled interaction with spore surface functional groups. Boronate ester linkages with surface glycans produced self-healing, recyclable hydrogels, while thia-Michael linkages with surface cysteines in organic solvents yielded dry composites with high tensile stiffness. Reaction equilibria could be manipulated through structural and environmental variables, as confirmed by NMR, Raman, and fluorescence spectroscopy. Material disassembly and recycling were achieved using competitive binding or entropy-driven bond reversal. Finally, engineered spores with surface enzymes yielded reusable catalytic materials. Together, this work introduces a modular platform for engineering mechanically and genetically programmable biohybrid composites through the independent design and assembly of polymers and microbes, opening new possibilities for the development of sustainable, multifunctional materials with diverse applications.