PCL-gelatin scaffold with atorvastatin and silybin: unlocking bone regeneration in rat calvarial defects and investigating bone genes (osteocalcin, collagen I, RUNX, and RANK/BMP).

Effective bone regeneration requires scaffolds that closely resemble the extracellular matrix and encourage cellular responses. Combining bioactive small molecules with biodegradable scaffolds presents a promising way to improve bone repair. This research focused on developing and testing a poly(ε-caprolactone)/gelatin (PCL/Gel) scaffold that was co-loaded with atorvastatin and silybin, two small molecules that promote bone growth, to enhance bone regeneration in a rat calvarial defect model. The scaffolds were made using thermally induced phase separation (TIPS), incorporating different amounts of atorvastatin and silybin. Physicochemical characterization included SEM, FTIR, porosity, compressive strength, degradation rate, contact angle, and drug release profile. In vitro, evaluations involved checking MG63 cell viability, hemocompatibility, and cytotoxicity. In vivo, performance was assessed in a rat model of critical-size calvarial defects using micro-CT, histology, and quantitative real-time PCR to measure key gene expression related to bone formation. The optimized scaffold (PCL/Gel with 24 μg/mL silybin and 19.75 μg/mL atorvastatin) showed high porosity (80 %), suitable mechanical strength (8.02 ± 0.95 MPa), and sustained drug release (atorvastatin: 68 % at 288 h; silybin: 48 % at 576 h). Cell viability exceeded 100 %, and hemolysis remained below 5 %. In vivo findings showed a 19.4 % closure of the bone defect after 8 weeks, which was higher than the single-drug group (7.2-17.5 %) or the drug-free group (15.2 %). RT-qPCR analysis indicated a significant increase in BMP, RUNX, COLa, and RANK gene expression in the dual-drug scaffold group. The co-loaded PCL/Gel scaffold demonstrated combined effect that promotes bone growth, integrating beneficial mechanical and biological properties with the affordable delivery of small molecules. These results highlight its potential for use in bone tissue engineering and the repair of critical-size defects.