Osteoblasts exhibit a more differentiated phenotype and increased bone morphogenetic protein production on titanium alloy substrates than on poly-ether-ether-ketone

Abstract

Background Context Multiple biomaterials are clinically available to spine surgeons for performing interbody fusion. Poly-ether-ether-ketone (PEEK) is used frequently for lumbar spine interbody fusion, but alternative materials are also used, including titanium (Ti) alloys. Previously, we showed that osteoblasts exhibit a more differentiated phenotype when grown on machined or grit-blasted titanium aluminum vanadium (Ti6Al4V) alloys with micron-scale roughened surfaces than when grown on smoother Ti6Al4V surfaces or on tissue culture polystyrene (TCPS). We hypothesized that osteoblasts cultured on rough Ti alloy substrates would present a more mature osteoblast phenotype than cells cultured on PEEK, suggesting that textured Ti6Al4V implants may provide a more osteogenic surface for interbody fusion devices. Purpose The aim of the present study was to compare osteoblast response to smooth Ti6Al4V (sTiAlV) and roughened Ti6Al4V (rTiAlV) with their response to PEEK with respect to differentiation and production of factors associated with osteogenesis. Study Design This in vitro study compared the phenotype of human MG63 osteoblast-like cells cultured on PEEK, sTiAlV, or rTiAlV surfaces and their production of bone morphogenetic proteins (BMPs). Methods Surface properties of PEEK, sTiAlV, and rTiAlV discs were determined. Human MG63 cells were grown on TCPS and the discs. Confluent cultures were harvested, and cell number, alkaline phosphatase–specific activity, and osteocalcin were measured as indicators of osteoblast maturation. Expression of messenger RNA (mRNA) for BMP2 and BMP4 was measured by real-time polymerase chain reaction. Levels of BMP2, BMP4, and BMP7 proteins were also measured in the conditioned media of the cell cultures. Results Although roughness measurements for sTiAlV (Sa=0.09±0.01), PEEK (Sa=0.43±0.07), and rTiAlV (Sa= 1.81±0.51) varied, substrates had similar contact angles, indicating comparable wettability. Cell morphology differed depending on the surface. Cells cultured on Ti6Al4V had lower cell number and increased alkaline phosphatase specific activity, osteocalcin, BMP2, BMP4, and BMP7 levels in comparison to PEEK. In particular, roughness significantly increased the mRNA levels of BMP2 and BMP4 and secreted levels of BMP4. Conclusions These data demonstrate that rTiAlV substrates increase osteoblast maturation and produce an osteogenic environment that contains BMP2, BMP4, and BMP7. The results show that modifying surface structure is sufficient to create an osteogenic environment without addition of exogenous factors, which may induce better and faster bone during interbody fusion.

Decreased bacteria activity on Si3N4 surfaces compared with PEEK or titanium

“…Other authors have supported these observations as they relate to PEEK and Ti. 67,68 The anti-infectivity of Si 3 N 4 may also relate to surface chemistry, and the authors' observations are consistent with previous data with polymeric coatings containing chitosan, a material similar to Si 3 N 4 in terms of a net positive charge and the presence of amine groups at the surface. [52][53][54][55][56] The interaction of these groups with negatively charged bacteria reportedly leads to membrane disruption and lysis in chitosan-containing polymers.…”

Fortifying the Bone-Implant Interface Part 1: An In Vitro Evaluation of 3D-Printed and TPS Porous Surfaces

“…34 Previous work has found that an implant's surface topology and roughness can be strategically tailored to optimize and accelerate in vitro cellularmaterial interactions. 35,36 Inspiration for such work stems from investigating natural bone turnover and healing, where osteoclasts prepare the surface to be remodeled with micron-scale roughness that aids in initiating subsequent osteoblastic activity. 37 Therefore, spinal implant surfaces modified to have micron-scale roughness may similarly stimulate osteoblasts to form bone matrix on the surface.…”

Fabrication of open-cellular (porous) titanium alloy implants: osseointegration, vascularization and preliminary human trials

“…Rapuano et al [28] reported that Ti-alloy can form a superficial oxide layer which promoted osteoblast attachment through binding of adsorbed fibronectin to surface-expressed osteoblast integrins. Moreover, Olivares-Navarrete et al [29] found that culture of MG 63 osteoblast-like cells on Ti6Al-4V can promote osteogenic maturation and create an osteogenic environment that could enhance bone formation and implant stability. Mechanical property of the implant is another factor which affects osseointegration.…”