FOAM VERSUS FIBRE SCAFFOLDS FOR MECHANICAL STIMULATION OF CELLS IN BONE TISSUE ENGINEERING

Introduction The morphology of a substrate on which cells are seeded is known to affect cells in multiple ways including morphology, proliferation differentiation and matrix production. However, it is difficult to characterise the effects of mechanical loading on cells seeded in scaffolds of different morphology but identical chemistry. The aim of this project is to create polyurethane foam and fibre scaffolds from the same linear polyurethane and to analyse the effect of scaffold morphology on mechanical properties, cell viability, and cell morphology. The current work aims to produce scaffolds of sufficient mechanical strength for mechanical stimulation experiments. Materials and Methods Foams were fabricated from a polypropylene oxide polyol and a toluene diisocyanate (TDI) by the direct foaming technique. Fibres were fabricated by dissolving the foam overnight in a 20wt% solution of dimethylacetamide under stirring conditions. The fibres were spun using an electrospinning rig with a 15kV electric field, 30cm working distance, flow rate of 3.5ml/hr and collected on a rotating drum. MC-3T3-E1 osteoblastic cells were seeded onto 2cm diameter, thin discs of each scaffold type at a density of 100 x 10 cells per sample. The seeded scaffolds were then left for 1hr to allow cell attachment before immersion in 3ml of media and culture for 21 days with a media change every 3 days. The distribution of viable cells was analysed by an assay of metabolic activity (MTS). Results Both foam and fibre morphologies are suitable for support of cell growth over medium term culture periods (21 days). Cell viability analysis showed no significant difference between the two morphologies. Microscopy analysis indicated cell attachment and survival within the pores of the foam scaffold with cells adhering to the struts. Both scaffolds can be cut into disk or dumbbell shapes suitable for mechanical stimulation in compression or tension respectively.