Electrosprayed naringin-loaded microsphere/SAIB hybrid depots enhance bone formation in a mouse calvarial defect model

The burst release of active osteogenic factors, which is not beneficial to osteogenesis, is commonly encountered in bone tissue engineering. The aims of this study were to prepare naringin-loaded microsphere/sucrose acetate isobutyrate (Ng-m-SAIB) hybrid depots, reduce the burst release of naringin (Ng), and improve osteogenesis. The morphology and size distributions of electrosprayed Ng-microspheres were characterized by scanning electron microscopy (SEM). The Ng-microspheres and Ng-m-SAIB depots were characterized by Fourier transform infrared spectroscopy (FTIR) and in vitro release studies. In vitro osteoblast-microsphere interactions and in vivo osteogenesis were assessed after implantation of Ng-m-SAIB depots. The addition of sucrose acetate isobutyrate (SAIB) to monodisperse Ng-microspheres did not cause a change in the chemical structure. The performances of the microspheres in osteoblast-microsphere interactions were better when the naringin content was 4% than when it was at 2% and 6%. On the first day following the loading of Ng-microspheres (2%, 4%, and 6%) into SAIB depots, the burst release was reduced dramatically from 70.9% to 6.3%, 73.1% to 7.2%, and 73.9% to 9.9%, respectively. In addition, after 8 weeks, the new bone formation rate in the calvarial defects of SD rats receiving Ng-m-SAIB was 53.1% compared to 21.2% for the control group and 16.1% for the microsphere-SAIB group. These results demonstrated that Ng-m-SAIB hybrid depots may have promise in bone regeneration applications.