Aligned Carbon Nanotube–Based Flexible Gel Substrates for Engineering Biohybrid Tissue Actuators

Abstract

Muscle-based biohybrid actuators have generated significant interest as the future of biorobotics but so far they move without having much control over their actuation behavior. Integration of microelectrodes into the backbone of these systems may enable guidance during their motion and allow precise control over these actuators with specific activation patterns. Here, we addressed this challenge by developing aligned CNT forest microelectrode arrays and incorporated them into scaffolds for stimulating the cells. Aligned CNTs were successfully embedded into flexible and biocompatible hydrogel exhibiting excellent anisotropic electrical conductivity. Bioactuators were then engineered by culturing cardiomyocytes on the CNT microelectrode-integrated hydrogel constructs. The resulting cardiac tissue showed homogeneous cell organization with improved cell-to-cell coupling and maturation, which was directly related to the contractile force of muscle tissue. This centimeter-scale bioactuator has excellent mechanical integrity, embedded microelectrodes and is capable of spontaneous actuation behavior. Furthermore, we demonstrated that a biohybrid machine can be controlled by an external electrical field provided by the integrated CNT microelectrode arrays. In addition, due to the anisotropic electrical conductivity of the electrodes provided from aligned CNTs, significantly different excitation thresholds were observed in different configurations such as the ones in parallel vs. perpendicular direction to the CNT alignment.

Advances in engineering hydrogels

“…To this end, a combination of myocytes (skeletal muscle cells or cardiomyocytes) and hydrogels that enable communications between these cells is usually adopted. For example, carbon nanotube–composited gelatin methacryloyl hydrogels have been processed into flexible substrates as large as centimeter scales, and cardiomyocytes spontaneously and synchronously beating on the surfaces allow these bioactuators to exhibit rhythmic contraction or extension and swimming behaviors(95, 96). Engineered skeletal muscles, when bound to bioprinted hydrogel frameworks, could also actuate and move the devices in defined patterns (13, 14).…”

Nanoparticles for bone tissue engineering

“… with permission from Elsevier), carbon NTs (H, adapted from Ref. with permission from John Wiley & Sons), and QDs (I, adapted from Ref. with permission from SAGE Publications).…”

Micro- and nano-patterned conductive graphene–PEG hybrid scaffolds for cardiac tissue engineering

“…Previous work has shown that engineered biohybrid actuators with anisotropic electrical conductivities can be manipulated to produce cardiac sheets with significantly different excitation thresholds 21 . These data suggest that modulation of directional conductivity cues can impact the functional phenotype of cultured cardiac cells.…”