Surface engineering, characterisation and applications of synthetic polymers for tissue engineering and regenerative medicine. Investigation of the response of MG63 osteosarcoma cell line to modified surface topographies, mechanical properties and cell-surface interactions using different synthetic polymers fabricated in house with various topographical features

Abstract

At present there is an extraordinary need to overcome barriers in regards to discovering novel and enhanced biomaterials for various tissue engineering applications. The need for durable orthopaedic implants is on the rise to limit issues such as revision surgery. A promising pathway to enhance fixation is to accelerate the onset and rate of early cellular adhesion and bone growth through nanoscale surface topography at the implant surface. The main aim of this research project was to investigate cellular response to altered physical and mechanical characteristics of materials suitable for orthopaedic applications. Four injection moulded polymeric substrates were produced, each with varied compositional and topographical characteristics. The four materials fabricated are Polyether-ether-ketone (PEEK), PEEK with 30% glass fibre (GL/PEEK) composite, PEEK and GL/PEEK with grooved topography. SEM and AFM analysis was used to investigate the groove dimensions and surface roughness of all samples followed by mechanical testing using a nano indenter to detect the Young’s modulus, stiffness and hardness of all four substrates. These tests were performed to determine which material has similar characteristics to cortical bone. These tests were followed by wettability and surface energy testing. Cell-substrate adhesion was examined using a cell viability assay to identify if there is a significant difference (p<0.05) between the percentage of viable cells on all four PEEK based materials. Imaging of MG-63 osteosarcoma cells using immunohistochemistry staining kits was conducted to observe the relationship between cell length and surface topography followed by a comparison between HaCaT (skin) cells and MG-63 (bone) cells. Following experimental testing mechanical variations between PEEK and GL/PEEK were identified alongside physical characterization differences. The grooved topography increased the surface roughness of PEEK and GL/PEEK in comparison to the planar surface. After 72 hours a correlation between the increased surface roughness and the percentage of viable MG-63 cells could be identified. When assessing the effect surface topography has on the water contact angles and surface energy, all four substrates showed no correlation. However, the grooved topography did increase the water contact angle and reduced the surface energy of PEEK in comparison to planar PEEK. Images of the four substrates after cell culture observed the grooved topography to affect the cellular orientation of both MG-63 and HaCaT cells. Polycaprolactone (PCL) scaffolds with a concentration of 1, 3, and 5% triclosan (an antimicrobial and antifungal agent) were fabricated using electrospinning. In addition to PCL + Triclosan scaffolds PCL with a concentration of 1% silver (an antimicrobial agent that can reduce the risk of infection) and 1, 3, and 5% triclosan were also electrospun. The pore size and fibre diameters of the scaffolds were investigated using SEM and Image J software followed by wettability and surface energy testing. MG-63 cells were cultured on all PCL scaffolds to study cellular viability percentage after 24 and 72 hours. The findings obtained showed the physical characteristics of PCL scaffolds to affect cellular viability of MG-63 cells. The output from these findings aim to provide data at a proof of concept level in understanding the relationship between the mechanical and physical characteristics of biomaterials and cellular behaviour.