Design and characterization of bioinstructive gold nanocomposite hydrogels for 3D bioprinting.

The rational design of hybrid nanocomposites that bridge nanoscale functionality and macroscale processability is central to advancing multifunctional materials for biofabrication and regenerative medicine. Craniofacial bone regeneration demands materials that provide mechanical stability while instructing stem-cell behavior toward functional tissue formation. Here, we present a rationally designed nanocomposite hydrogel integrating gold nanoparticles (AuNPs) functionalized with polyethylene glycol (PEG) and glutathione (GSH) into a gelatin methacrylate (GelMA) matrix to couple rheological tunability with biological activity. AuNPs were synthesized via chemical reduction, PEGylated for colloidal and thermal stability, and conjugated with GSH to introduce bioactive thiol and carboxyl groups that promote osteogenic signaling. Comprehensive physicochemical analyses confirmed successful functionalization, uniform dispersion, and stability across physiological conditions. Incorporation of PEG-GSH-AuNPs at optimized concentrations enhanced the complex viscosity, yield stress, and print fidelity of GelMA while preserving its shear-thinning behavior essential for extrusion-based bioprinting. Periodontal ligament stem cells (PDLSCs) encapsulated within the printed constructs maintained >90% viability and exhibited pronounced mineralization and upregulation of osteogenic markers, confirming the instructive potential of the hybrid bioink. This study establishes a modular strategy that bridges nanoscale material design with macroscale biofabrication, yielding a thermally stable, biologically active hydrogel capable of directing stem-cell fate. The resulting nanocomposite platform offers broad potential for precision bioprinting and next-generation bone and craniofacial tissue regeneration.