Proinflammatory cytokine expression of IL-1β and TNF-α by human osteoblast-like MG-63 cells upon exposure to silicon nitride in vitro

This study was designed to determine the effect of Si₃N₄ disks and particulates on human osteoblast-like MG-63 cells in vitro. The MG-63 (10⁵/mL) cells were plated onto 24-well polystyrene plates fitted with either sintered reaction-bonded (SRBSN) or reaction-bonded (RBSN) 15mm disks. Controls consisted of wells without Si₃N₄ disks. Cells propagated at 37°C, 5% CO₂ for 48 h on Si₃N₄ disks and control polystyrene surfaces exhibited similar proliferative capacities (7000 and 4000 cpm/10⁵ cells, respectively, p > 0.05). Cells incubated with 1, 10, or 100 μg/ml of Si₃N₄ particles (<1.00 to 5.00 μm) for 24 h did not exhibit a decrease in DNA synthetic activity: 12 ± 1.3 x 10⁴, 10.5 ± 1.5 x 10⁴, and 11.0 ± 1.7 x 10⁴ cpm, respectively, compared to 11.6 ± 2.6 x 10⁴ cpm/10⁵ for the control cells, as indicated by ³H-thymidine uptake. Cells propagated on RBSN displayed increased expression of cytokines IL-1β and TNF-α compared to the control cells, as shown by reverse transcriptase-polymerase chain reaction (RT-PCR). In contrast, cells propagated on SRBSN surfaces expressed the same level of IL-1β and TNF-α as that of control cells. Incubation of MG-63 cells with 1- 10 μg/mL of particles did not increase IL-1β expression. However, at 100 μg/mL, TNF-α expression was greater than that of the control cells. Silicon nitride, evaluated here as disks or as particulates (1-10 μg/mL), is biocompatible and does not hinder the proliferation or induce proinflammatory cytokine expression of human osteoblast-like MG-63 cells in vitro.