Abstract
Nanoscale topography increases the bioactivity of a material and stimulates specific responses (third generation biomaterial properties) at the molecular level upon first generation (bioinert) or second generation (bioresorbable or bioactive) biomaterials.
We developed a technique (based upon the effects of nanoscale topography) that facilitated the in vitro expansion of bone graft for subsequent implantation and investigated the optimal conditions for growing new mineralised bone in vitro.
Two topographies (nanopits and nanoislands) were embossed into the bioresorbable polymer Polycaprolactone (PCL). Three dimensional cell culture was performed using double-sided embossing of substrates, seeding of both sides, and vertical positioning of substrates. The effect of Hydroxyapatite, and chemical stimulation were also examined.
Human bone marrow was harvested from hip arthroplasty patients, the mesenchymal stem cells culture expanded and used for cellular analysis of substrate bioactivity.
The cell line specificity and osteogenic behaviour was demonstrated through immunohistochemistry, confirmed by real-time PCR and quantitative PCR. Mineralisation was demonstrated using alizarin red staining.
Results showed that the osteoinduction was optimally conferred by the presence of nanotopography, and also by the incorporation of hydroxyapatite (HA) into the PCL. The nanopit topography and HA were both superior to the use of BMP2 in the production of mineralised bone tissue.
The protocol from shim production to bone marrow harvesting and vertical cell culture on nanoembossed HaPCL has been shown to be reproducible and potentially applicable to economical larger scale production.
