Internal fixation of femoral neck fracture using screws coated with vascular endothelial growth factorloaded nanographene

Abstract

Objective To evaluate the internal fixation screws coated with vascular endothelial growth factor (VEGF)-loaded nanographene in the treatment of femoral neck fracture. Methods Screws with nanographene coating were prepared by direct liquidphase exfoliation of the graphite. After the surface characteristics were observed through scanning electron microscopy (SEM), the nanographene coating was loaded with VEGF through physical adsorption and controlled release of the VEGF was examined by ELISA. Femoral neck fracture models were built in 10 healthy adult canines to examine both the angiogenic and osteogenic properties of the screws coated with VEGF-loaded nanographene which were implanted at the experimental sides while the screws with mere nanographene coating at the contralateral sides as controls. X-ray and histopathologic evaluations were used to assess the fracture healing progress. Results SEM demonstrated that the screws were coated successfully with VEGF-loaded nanographene. The coating did not increase the cytotoxity of screws. The accumulative release of VEGF clearly increased during the entire testing period (9 days) with a maximum release of 9.51±0.23 ng. X-ray and histopathologic examination proved better fracture healing at the experimental sides than at the contralateral sides. The percentage of trabecular area at the experimental sides (50.8%±3.3%) was insignificantly larger than at the control sides (43.7%±3.9%), and the trabecular width at the experimental sides (146.8±19.5 μm) was insignificantly greater than at the control sides (129.0±10.2 μm) (P>0.05). The area of new bone trabecula at the experimental sides (17.3%±1.5%) was significantly larger than at the control sides (8.3%±1.6%), and the microvessel density (MVD) at the experimental sides (113.4±12.5) was also significantly greater than at the control sides (61.2±9.4) (P<0.05). Conclusions The nanographene coating can load and release VEGF effectively. The screws coated with VEGF-loaded nanographene possess a certain degree of bioactivity which may promote vascular repair in the treatment of femoral neck fracture. Key words: Femoral neck fractures; Fracture fixation, internal; Bone nails; Nanocomposites; Vascular endothelial growth factor