Spiral-shaped SU-8 cantilevers for monitoring mechanical response of cardiomyocytes treated with cardiac drugs

Abstract

In this paper, a spiral-shaped SU-8 cantilever with biocompatibility was proposed to monitor the changes of cardiac contraction in response to injection of drug in real time. The cantilever comprises a thick quadrate body and a filmy spiral cantilever with micro-grooves and gold patterns on the top of its surface. The longitudinally patterned micro-grooves facilitate the aligned growth of cardiomyocytes in order to increase the contraction force. In addition, the spiral shape increases the cantilever’s effective length and decreases its spring constant, which means its bending displacement can be increased for the same force as compared to that observed in a conventional rectangular cantilever. The bending displacement of the spiral SU-8 cantilever induced by the contraction of cardiomyocytes can be precisely measured at the nanoscale using a homemade laser-based measurement system. The displacement in the spiral SU-8 cantilever without micro-grooves was much greater than that in the case of traditional rectangular SU-8 cantilevers. The displacement produced by the spiral cantilever with grooves is 240% greater than that without grooves. Following preliminary experiments, cardiac drugs including Verapamil, Quinidine, Lidocaine, E-4031, and Bay K 8644 were used to evaluate their side effects on cardiomyocytes. Quantitative analysis of measurements shows that not only Verapamil and Quinidine but also Lidocaine and E-4031 treatment can decrease the cell beating frequency, and both the Verapamil and Lidocaine treatment can decrease the cell contraction force. Furthermore, Bay K 8644 assay results indicate that it can decrease the contraction force and increase the beating frequency of cardiomyocytes.