Development of 3D stress field mapping for bioprinted cardiac tissue

Generating contractile forces, and withstanding compressive and stretching stress are requisite cardiac functions. With advancement in tissue engineering, it is critical to develop a systematic way to characterize mechanical behaviors in 3D engineered tissues to assure the quality of potential clinical applications. We mapped 3D stress fields in bioprinted cardiac tissues by dynamically tracking micron-sized particles labeling the tissue. Based on the displacement of the particles, values of three metrics were extracted: velocity, beating frequency, and contraction force using the modified Stokes’ Equation. The viscoelasticity of the tissue was assessed using magnetic tweezers. Combining the measurement results, force and stress were mapped to the tissue by finite element method (FEM). We observed that contractile frequency ranges from 0.5 Hz to 1 Hz, agreeing with the physiological heart rate. Force maps revealed that contractile forces are heterogeneous over the cardiac tissue. Computationally, 3D force/stress maps by FEM were modeled constitutively and compared with the measurement data. We conclude our new methods are accurate in informing functional properties of engineered cardiac tissues, and potentially applicable to clinical practice.