Calibrated micropost arrays for biomechanical characterisation of cardiomyocytes

The study of biomechanics of isolated cardiomyocytes can allow us to understand the cardiac function and disease development in the absence of viscoelastic or contractile properties of the surrounding tissue. However, popular techniques such as micropipettes and carbon fibre-based measurements require serial, single-cell measurements and limit the amount of data passing through a system or process. The authors utilise elastomer micropost arrays microfabricated by a replica molding technique for precise and quantitative force measurements of cardiomyocytes with the potential for high throughput. The authors also present a calibration system using a piezoresistive force sensor and video-analysis technique to improve the resolution and validate the analysis of these low-force measurements. Calibrated microposts arrays are applied to measure the contractile forces of rat neonatal cardiomyocytes. Using image processing, the contractile forces for a sample of cardiomyocytes are extracted. It was found that isolated rat neonatal myocytes generate 39 ± 5 nN average contractile force per post and an integrated axial contractile force of 189 ± 20 nN, which is four times smaller than isolated adult Wistar rat cardiomyocytes and 30 times smaller than isolated adult rat cardiomyocytes. With calibration and quantitative image analysis, this study demonstrates that micropost systems can provide precise high-throughput test beds for myocyte mechanics using pharmacologic, small peptide, gene therapies or heart disease models.