Zone specific 3D-printed meniscus scaffold from nanohydroxyapatite-reinforced polycaprolactone/hydrogel bioinks

This research aimed to engineer a 3D-printed meniscus scaffold designed to functionally and structurally mimic the native human meniscus, which exhibits zone-specific biochemical composition. Specifically, the design incorporated a fibrous outer region and a cartilaginous inner region. To achieve this, a composite material consisting of polycaprolactone (PCL) reinforced with nanohydroxyapatite (HA) was selected as the base material. This choice was based on the material’s mechanical properties, which closely approximate those of the native meniscus tissue. Two distinct hydrogels were employed as bioinks: gelatin methacrylate (GelMA) for the outer region, hypothesized to promote fibrogenesis, and a combination of glycidyl methacrylate-modified poly(vinyl alcohol) and glycidyl methacrylate-modified silk fibroin (PVA-g-GMA/SF-g-GMA) for the inner region, designed to induce chondrogenesis. A dual-nozzle 3D printing technique was utilized to fabricate the scaffold, allowing for the precise deposition of the PCL/HA composite and the two hydrogel bioinks in their respective zones. Following a 28-day in vitro culture period, the outer PCL/HA/GelMA region exhibited elevated expression of type I collagen (COL1A1), a marker indicative of fibrous tissue formation. Conversely, the inner PCL/HA/PVA-g-GMA/SF-g-GMA region demonstrated increased expression of type II collagen (COL2A1), aggrecan (ACAN), and SRY-box transcription factor 9 (SOX9), all of which are key markers of cartilage tissue development. These findings confirm that the outer region successfully exhibited fibrogenic characteristics, while the inner region displayed chondrogenic properties, effectively resembling the zonal biochemical composition of the native meniscus. Furthermore, the 3D-printed PCL/HA/hydrogel scaffold demonstrated mechanical properties comparable to those of the human meniscus, ensuring structural integrity. The scaffold closely resembled the anatomical shape of both the medial and lateral menisci. In conclusion, this study demonstrates the feasibility of fabricating a 3D-printed meniscus scaffold that aligns with the anatomical, biochemical, and mechanical characteristics of the native human meniscus. This scaffold holds significant potential for applications in meniscus tissue engineering and regenerative medicine.