Calcium Imparts Advanced Functionalities to Silk Hydrogels for Biofabrication and Biomedical Innovation

Abstract

Photocrosslinked silk hydrogels offer a versatile platform for biomedical applications, thanks to their elasticity and compatibility with advanced manufacturing techniques. Here, a rapid and scalable strategy to enhance di-tyrosine photocrosslinking by incorporating calcium ions (Ca²⁺), inspired by their role in natural silk spinning, is presented. Using a visible-light based photoinitiating system, Ca²⁺-supplemented hydrogels demonstrate superior transparency, stretchability, and toughness, supporting high-fidelity digital light processing and volumetric printing. These silk inks remain stable and printable after extended storage at room temperature, enabling on-demand fabrication and eliminating the need for the cold chain. Notabl²⁺ imparts humidity-responsive and adhesive properties, as well as strong interlayer bonding. This enables the creation of modular, multizonal, and multilayered constructs, which can be permanently fused via autoclaving. Beyond structural advantages, silk-calcium hydrogels exhibit enhanced thermal diffusivity and electrical conductivity, making them suitable for passive cooling and bioelectronic interfaces. Subcutaneous implantation in mice confirms biocompatibility. This work introduces a multifunctional silk hydrogel platform with rapid photocrosslinking, long-term ink stability, and modular assembly capabilities, advancing the design of stimuli-responsive biomaterials for tissue engineering, wound healing, and wearable technologies.