Development of Light-Responsive Liquid Crystalline Elastomers to Assist Cardiac Contraction

Abstract

Despite major advances in cardiovascular medicine, heart disease remains a leading cause of death worldwide. However, the field of tissue engineering has been growing exponentially in the last decade and restoring heart functionality is now an affordable target; yet, new materials are still needed for effectively provide rapid and long-lasting interventions. Liquid crystalline elastomers (LCEs) are biocompatible polymers able to reversibly change shape in response to a given stimulus and generate movement. Once stimulated, LCEs can produce tension or movement like a muscle. However, so far their application in biology was limited by slow response times and a modest possibility to modulate tension levels during activation. Objective: To develop suitable LCE-based materials to assist cardiac contraction. Methods and Results: Thanks to a quick, simple, and versatile synthetic approach, a palette of biocompatible acrylate-based light-responsive LCEs with different molecular composition was prepared and mechanically characterized. Out of this, the more compliant one was selected. This material was able to contract for some weeks when activated with very low light intensity within a physiological environment. Its contraction was modulated in terms of light intensity, stimulation frequency, and t on /t off ratio to fit different contraction amplitude/time courses, including those of the human heart. Finally, LCE strips were mounted in parallel with cardiac trabeculae, and we demonstrated their ability to improve muscular systolic function, with no impact on diastolic properties. Conclusions: Our results indicated LCEs are promising in assisting cardiac mechanical function and developing a new generation of contraction assist devices. (Circ Res. 2019;124:e44-e54.

Body‐temperature shape‐shifting liquid crystal elastomers

“…3 Since the conception of the liquid crystal elastomers, various novel engineering applications have been proposed based on the reversible actuation including actuators, [4][5][6] soft robotics, 7,8 optical elements 9 and mechanical damping. 10,11 Additionally, LCEs are proposed for biomedical applications such as artificial muscle, [12][13][14] scaffolds for tissue engineering, 15 drugdelivery vehicles, 16 vascular implants, 17 interbody fusion cages 18 and synthetic intervertebral disc. 19 However, the proposed biomedical applications mostly focused on either the non-actuation behavior or externally controlled shape-activation.…”

Opposite Self-Folding Behavior of Polymeric Photoresponsive Actuators Enabled by a Molecular Approach

“…In this specific case, the dye has a strong absorption in the visible range, and therefore a green light was employed to activate the shape-change [25]. Both laser and incoherent light irradiation (by an LED lamp) can be used to drive the deformation [38]. Within the selected formulations, the mechanism of the material reshaping has to be ascribed to thermal heating (where light energy is dissipated inside the network as heat) [39], rather than an optical effect, due to the trans-to-cis isomerization that, on the other hand, affords a photo-softening effect at low light power [27].…”

Pros and Cons: Magnetic versus Optical Microrobots

“…LCEs typically exhibit a larger deformation but their backbone is quite soft, which means they produce small forces under actuation. LCNs, on the other hand, produce stronger forces that can be of the order of hundreds of mN mm −2 39. The liquid‐crystalline order at room temperature (typically resulting in a highly anisotropic medium) is lost upon heating resulting in a controlled and fully reversible shape change.…”