Research highlights: Highlights from the last year in nanomedicine.

Synthetic biology attempts to reproduce emergent behaviors from natural biology with the goal of creating artificial life. The main challenge in this field is the reduction of complex phenomena into functional components, which can be individually engineered and later combined to replicate the macroscopic behavior of the model biological system. Nawroth and coworkers reverse-engineered the mechanics of jellyfish propulsion by studying the structural design, stroke kinematics and fluid–solid interactions of the jellyfish, and exploiting the natural properties of the living and nonliving materials used in the design. The artificial jellyfish, dubbed ‘medusoids’, were composed of a bilayer of living muscle tissue and synthetic elastomer arranged in freely movable lobes around a central disc. Medusoid propulsion, like that of a jellyfish, was externally driven by electrically paced power and recovery strokes that alternately contracted the body into a quasi-closed ‘bell’ and then relaxed into the open-lobed form. The muscle layer, comprised of anisotropic rat cardiac tissue that intrinsically enables spatiotemporally synchronous contraction, replicated the power stroke of the jellyfish. The recovery stroke, which is a consequence of elastic recoil in the jellyfish compliant matrix, was replicated by tuning the stiffness of the synthetic elastomer substrate. The geometry was further refined to allow the formation of overlapping boundary layers between lobes, thereby resisting flow across the lobe gaps. Qualitative and quantitative comparisons of jellyfish and medusoid propulsion showed that the engineered system was able to replicate the momentum, transport and body lengths traveled per swimming stroke of the natural system. This serves as a powerful demonstration of biomimetic swimming of a simple, natural life form, that can be engineered from a few materials and some well-arranged cells. It also represents an important developmental milestone in the rise of biological actuators and has implications in tissue engineering and drug discovery/screening applications. Reverse engineering jellyfish with rat heart cells