Abstract
Poly-ether-ether-ketone (PEEK) is a biomaterial commonly used for spinal implants and screws. It is often desirable for orthopaedic implants to osseointegrate, but as PEEK is biologically inert this will not occur. The aim of this project was to determine if injection mould nanopatterning can be used to create a make PEEK bioactive and stimulate osteogenesis in vitro.
PEEK substrates were fabricated by injection mould nanopatterning to produce near-square (NSQ) nanopatterned PEEK and planar (FLAT) PEEK samples. Atomic force microscopy (AFM) and scanning electron microscopy were used to characterize the surface topography. Human bone marrow stromal cells (hBMSCs) were isolated from patients undergoing primary hip replacement operations and seeded onto the PEEK substrates. After 6 weeks the cells were stained using alizarin red S (ARS) stain (to detect calcium) and the von Kossa technique (to detect phosphate) and analyzed using CellProfiler image analysis software to determine: surface coverage; cell number; and expression of either calcium (ARS stain) or phosphate (von Kossa technique).
ARS stain showed calcium expression (quantified relative to the number of cells) was increased on NSQ PEEK compared to FLAT PEEK (not statistically significant) and the surface coverage was similar. Von Kossa staining revealed more surface coverage on FLAT PEEK (69.1% cf. 31.9%), cell number was increased on FLAT PEEK (9803 ± 4066 cf. 4068 ± 1884) and phosphate expression relative to cell number was also increased (seven-fold) on NSQ PEEK (P < 0.05) compared to FLAT PEEK.
Although hBMSCs may adhere to NSQ PEEK in smaller numbers, the cells expressed a relatively larger amount of calcium and phosphate. This indicates that the cells adopted a more osteoblastic phenotype and that nanopatterning PEEK induces hBMSC differentiation and stimulates osteogenesis. Injection mould nanopatterning therefore has the potential to improve osseointegration of PEEK implants in vivo.
