Bioengineering toughened, stretchable bacterial cellulose-based films inspired by spider silk

Bacterial cellulose (BC) has emerged as a promising sustainable biomaterial with potential across multiple fields. However, its intrinsic stiffness and limited toughness restrict its use in applications such as textiles or wearable devices. Spider silk is one of nature's toughest materials, combining high strength and extensibility. The recombinant mini-spidroin (A₃I)₃-A₁₄, a minimized synthetic variant of a spider silk protein, can be spun under mild conditions into ductile and tough fibers. Here, we present a bioinspired strategy to toughen BC with (A₃I)₃-A₁₄ by tuning the incorporation route and protein conformation to achieve lower stiffness, higher extensibility, and improved energy dissipation. A motile strain, E. coli JM109 (DE3), was used as a heterologous production host and active delivery vehicle to introduce the mini-spidroin within the BC hydrogel. Guided by glucose-gradient-driven colonization of the porous BC nanofiber network, followed by controlled sodium dodecyl sulfate (SDS)-alkali-mediated cell lysis, this approach enabled deeper in situ incorporation of (A₃I)₃-A₁₄ within the BC matrix. The resulting BC-silk composites exhibited an >240% increase in toughness, primarily driven by a significant enhancement of the strain at break. This balanced combination of softness, strain tolerance, and energy absorption highlights the potential of BC-silk composites as crease-resistant bio-based films.