Design and fabrication of functionally graded 3D polymeric scaffolds for simultaneous cell support and localized MicroRNA delivery.

Scaffolds have proven useful as matrices for cell culture, tissue ingrowth, organ formation, mechanical support, drug screening platforms, and localized delivery systems. Their performance depends on multiple structural and material properties that determine their suitability for specific applications. In this study, we developed a multifunctional scaffold designed to provide both cell culture support and gradual microRNA (miRNA, miR) delivery. A method was first introduced for generating heterogeneous triply periodic minimal surface (TPMS)-based scaffold architectures. Compared with existing methods, the proposed approach provides a more user-friendly strategy for generating functionally graded structures and enables irregular architectural variations throughout the scaffold. The scaffolds were fabricated using fused filament deposition (FFD) and evaluated for printing fidelity. A gelatin/polyethyleneimine (PEI)-based delivery system was developed to immobilize miRNA on the scaffold surface, and its release profile was optimized. The scaffolds were further evaluated for cell attachment, proliferation, infiltration, and transfection efficiency. The proposed design method successfully generated complex architectural deformations while maintaining printability. The scaffold surface supported favorable cell attachment and proliferation, whereas cell infiltration was influenced by both porosity and geometry. The developed delivery system provided gradual miRNA release over 7 days and effectively transfected primary cells, achieving a transfection efficiency of 67% in human mesenchymal stromal cells without significant cytotoxicity. These findings demonstrate a multifunctional scaffold that combines advanced architectural design with gradual nucleic acid delivery for tissue engineering applications.