Surface-patterned SU-8 cantilever arrays for preliminary screening of cardiac toxicity

Arrays of a μgrooved SU-8 cantilever were utilized to analyze changes in the contraction force and beating frequency of cardiomyocytes in vitro. The longitudinally patterned μgrooves facilitates alignment of cardiomyocytes on top of the SU-8 cantilever, which increases the contraction force of cardiomyocytes by a factor of about 2.5. The bending displacement of the SU-8 cantilever was precisely measured in nanoscale using a laser-based measurement system combined with a motorized xyz stage. The cantilever displacement due to contraction of the cardiomyocytes showed the maximum on day 8 after their cultivation. Following preliminary experiments, Isoproterenol, Verapamil, and Astemizole were used to investigate the effect of drug toxicity on the physiology of cardiomyocytes. The experimental results indicated that 1 µM of Isoproterenol treatment increased contraction force and beating frequencies of cardiomyocytes by 30% and 200%, respectively, whereas 500 nM of Verapamil treatment decreased contraction force and beating frequencies of cardiomyocytes by 56% and 42%, respectively. A concentration of less than 5 nM of the hERG channel suppression drug Astemizole did not change the contraction forces in the displacement but slightly decreased the beating frequencies. However, irregular or abnormal heartbeats were observed at Astemizole concentrations of 5 nM and higher. We experimentally conformed that the proposed SU-8 cantilever arrays combined with the laser-based measurement systems has the great potential for a high-throughput drug toxicity screening system in future.