Abstract:

Objective Conventional approaches for articular cartilage repair such as microfracture and autologous chondrocyte implantation face significant drawbacks including fibrocartilage formation and donor site morbidity. This study addresses these critical challenges by developing advanced 3D-printed scaffolds, focusing on creating silk fibroin (SF)/gelatin (GEL) composite scaffolds with optimized structural and biological properties to support cartilage regeneration. By investigating material composition and preparation parameters, this work aims to establish a reliable platform for producing scaffolds that meet both mechanical and biological requirements for effective cartilage repair, while addressing key issues of structural stability, pore structure control, and cell-material interactions.

Method The research employed extrusion-based 3D printing technology to prepare SF/GEL scaffolds at three different mass ratios (70∶30, 50∶50, 30∶70). Printing was conducted at 4 ℃ using a custom-built direct-write system with a 0.9 mm nozzle diameter. The scaffolds underwent post-treatment with 75% ethanol for 30 min to induce crosslinking, followed by freeze-drying to create porous structures. Comprehensive characterization included microstructural analysis using scanning electron microscopy (SEM), microstructural evaluation through Fourier-transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). Biological performance was evaluated using mouse embryonic osteoblasts, with cell proliferation quantified by MTT assay and cell morphology analyzed via confocal microscopy over 1, 3, and 7 d culture periods.

Results Extrusion 3D printing was proven to be successful in preparing grid shaped SF/GEL scaffolds with different mass ratios (70∶30, 50∶50, 30∶70). When the mass ratio of SF to GEL was 50∶50, the printed hydrogel scaffolds appeared linear and regular, and ethanol treatment was more beneficial to the molding of 3D printing SF/GEL scaffold materials. The microstructure of SF/GEL scaffolds presented a honeycombed porous structure. After ethanol treatment, the structure of the scaffold became compact, with fewer pores and smaller pore sizes. FT-IR and XRD characterizations indicated the presence of hydrogen bonding between SF and GEL. After ethanol crosslinking, the microstructure of the scaffold changed from random curling to β folding, and the crystallinity of the scaffold increased. Cell experiments showed that SF/GEL scaffolds with different mass ratios supported the proliferation of mouse embryonic osteoblasts. After 7 d culture, the cells were arranged in a spindle shaped and isotropic manner, indicating that the scaffolds have good biocompatibility.

Conclusion This study successfully developed 3D-printed SF/GEL scaffolds with adjustable properties suitable for cartilage tissue engineering applications. The research provides substantial evidence that these scaffolds can support cell attachment, proliferation, and extracellular matrix production while maintaining appropriate mechanical properties. The findings advance the understanding in the field of cartilage repair by offering a reproducible preparation method that addresses critical challenges in scaffold design, including the balance between structural stability and bioactivity. The demonstrated combination of material properties and cellular responses suggests strong potential for clinical translation, though further investigation through in vivo studies and long-term implantation evaluations will be necessary to fully assess the therapeutic potential of the scaffolds. This work establishes a foundation for future development of more complex, functionally graded scaffolds for osteochondral tissue engineering.

Key words: 3D printing, silk fibroin, gelatin, microstructure, biocompatibility, cartilage scaffold, tissue engineering