Application of advanced material analyses for the investigation of the role of nano-mechanical properties in cell - scaffold interactions
The fate of cells seeded onto a scaffold is determined by a number of factors including chemical, topographical and mechanical stimuli. The combination of these factors regulates a number of cellular functions and ultimately determines the performance of the engineered tissue. In recent years, focus has shifted from investigating bulk scaffold properties to nano-scale properties that are more relevant on the cellular scale. This trend has been partially fuelled by a significant increase in the availability of nano-scale analysis techniques and a general development in scientific investigations on such scales. Standard Euler's principles do not apply on the nano-scale, and a number of previous publications have examined and modelled various strain dependent nano-mechanical properties. Size effect theories predict that the effective modulus of elasticity increases as the length scale of measurement decreases. These changes occur at the length scales of the order of the cell and their effects on cellular mechanotransduction have not yet been investigated. This body of work attempts to lay the foundations and develop techniques that can eventually be used to investigate the influence of nano-mechanical properties on cell mechanotransduction in fibrous scaffolds. Medical grade polyurethanes (Biomer Technology Limited, Runcorn, UK) were chosen for this study because of their wide range of mechanical properties while maintaining similar chemistry. Solvent-cast films fabricated from various grades of these materials were first characterised on both the nano- and macro- scale in order to inform the fabrication of three-dimensional electrospun fibrous scaffolds. Such scaffolds were then fabricated with a variety of nano-mechanical properties by altering fibre diameter distributions. Dual spinning was also used in order to fabricate a scaffold with mixed nano-mechanical properties. The stability of such polymers when stored under physiological conditions over a period of 90 days was then investigated. Thereafter, samples were prepared for use in an initial assessment of cell attachment in order to investigate the extent to which three different cell types were able to adhere and proliferate on both scaffold forms fabricated from two grades of polyurethane with distinct macro- and nano- mechanical properties. The implications that such changes in nano-mechanical properties could have on cell mechanotransduction are discussed. Further experiments are suggested in order to develop a better understanding of these interactions.
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