A smart nanocomposite bioactive ink for controlled siRNA delivery in calvarial mesenchymal stromal cells as a minimally invasive treatment for craniosynostosis

: Craniosynostosis (CS), characterized by the premature fusion of cranial sutures, often results from aberrant activation of Fibroblast growth factor receptor 2 (FGFR2), a major regulator of osteogenic differentiation in cranial mesenchyme. Despite surgical interventions, recurrence and complications remain common, underscoring the need for targeted molecular therapies. In this study, we developed a novel formulation of bioactive nanocomposite hydrogel-based ink designed for localized, sustained delivery of therapeutic small interfering RNAs (siRNAs) targeting FGFR2. The delivery system combines gelatin methacryloyl (GelMA), a biocompatible and photo-crosslinkable hydrogel, with poly-lactic-co-glycolic acid (PLGA) nanoparticles (NPs), creating an injectable and mouldable platform with potential for future craniofacial application. Selected siRNAs achieved up to 90% FGFR2 mRNA knockdown and reduced downstream protein signalling activation, including pFGFR2 (60%), pERK1/2 (37%) and RUNX2 (43%) in patient-derived cells. PLGA NPs demonstrated high siRNA encapsulation efficiency, efficient cytoplasmic delivery and lysosomal escape. When embedded in GelMA and 3D-printed, the GelMA-NP system showed sustained NP retention and a controlled-release profile, maintaining functional gene silencing for up to 20 days. This multifunctional platform not only supports FGFR2 modulation in CS but also holds translational promise as a customizable scaffold for delivering other bioactive compounds, advancing paediatric cranioplasty outcomes.