Urease-coupled systems and materials: Design strategies, scope and applications

Synthetic systems have co-opted urease, a crucial enzyme serving many biological functions, to recapitulate complex biological features. Therefore, the urease-urea feedback reaction network (FCRN) is reciprocated with soft materials to induce various animate-like features, including self-regulation, error correction, and decision-making capabilities, that are processed through a variety of non-linear functions. Although free-urease-based homogeneous systems are capable of adhering to many non-linear characteristics, they lack the ability to showcase the diffusion-controlled spatiotemporal phenomena. Therefore, it demands urease immobilization, whereby a compartmentalized reaction hub can facilitate the interplay of FCRN with reaction diffusion to regulate the system's operation, allowing various non-linear responses and spatiotemporal self-organization. Indeed, the beneficial framework of urease-based commercial systems in modern technology necessitates the accessibility, reusability, and long-term stability of urease. Consequently, several techniques for urease immobilization merit attention. This review highlights the diverse covalent and non-covalent approaches for urease immobilization on different substrates and illustrates several chemical reactions and non-covalent interactions as tools for creating targeted systems and soft materials to realize many on-demand functions. We also emphasize how the advancement of systems chemistry has propelled research in soft materials to comprehend system-level applications by demonstrating several emerging non-linear functions with potent applications in many directions, including sensing, soft robotics, regulation of material properties and many more.