The antimicrobial and osteoinductive properties of silver nanoparticle/poly (DL-lactic-co-glycolic acid)-coated stainless steel.

Implant-associated bacterial infections are one of the most serious complications in orthopedic surgery. Treatment of these infections often requires multiple operations, device removal, long-term systemic antibiotics, and extended rehabilitation, and is frequently ineffective, leading to worse clinical outcomes and increased financial costs. In this study, we evaluated silver nanoparticle/poly(DL-lactic-co-glycolic acid) (PLGA)-coated stainless steel alloy(SNPSA) as a potential antimicrobial implant material. We found that SNPSA exhibited strong antibacterial activity in vitro and ex vivo, and promoted MC3T3-E1 pre-osteoblasts proliferation and maturation in vitro. Furthermore, SNPSA implants induced osteogenesis while suppressing bacterial survival in contaminated rat femoral canals. Our results indicate that SNPSA has simultaneous antimicrobial and osteoinductive properties that make it a promising therapeutic material in orthopedic surgery.

NELL-1-dependent mineralisation of Saos-2 human osteosarcoma cells is mediated via c-Jun N-terminal kinase pathway activation.

PURPOSE: NELL-1 is a novel osteoinductive growth factor that has shown promising results for the regeneration of bone. Moreover, NELL-1 has been used successfully in bone regeneration in the axial, appendicular and calvarial skeleton of both small and large animal models. Despite increasing evidence of NELL-1 efficacy and future usefulness as an alternative to traditional bone graft substitutes, much has yet to be understood regarding the mechanisms of action of this novel protein. The activation of the mitogen-activated protein kinase (MAPK) pathway has been well studied in the setting of growth factor-mediated changes in osteogenic differentiation. METHODS: In this study, we provide evidence of the involvement of MAPK signalling pathways in NELL-1-induced terminal osteogenic differentiation of Saos-2 human osteosarcoma cells. Activation of extracellular signal-regulated kinase (ERK1/2), P38 and c-Jun N-terminal kinase (JNK) pathways were screened with MAPK signalling protein array after recombinant human (rh)NELL-1 treatment. Next, the mineralisation and intracellular phosphate levels after rhNELL-1 stimulation were assessed in the presence or absence of specific MAPK inhibitors. RESULTS: Results showed that rhNELL-1 predominantly increased JNK pathway activation. Moreover, the specific JNK inhibitor SP600125 blocked rhNELL-1-induced mineralisation and intracellular phosphate accumulation, whereas ERK1/2 and P38 inhibitors showed no effect. CONCLUSIONS: Thus, activation of the JNK pathway is necessary to mediate terminal osteogenic differentiation of Saos-2 osteosarcoma cells by rhNELL-1. Future studies will extend these in vitro mechanisms to the in vivo effects of NELL-1 in dealing with orthopaedic defects caused by skeletal malignancies or other aetiologies.