Tissue engineered grafts may be useful in myocardial repair, however previous scaffolds have been structurally incompatible with recapitulating cardiac anisotropy. Utilizing microfabrication techniques, a novel accordion-like honeycomb microstructure was rendered in poly(glycerol sebacate) to yield porous, elastomeric 3-D scaffolds with controllable stiffness and anisotropy. Accordion-like honeycomb scaffolds with cultured neonatal rat heart cells demonstrated utility via: (1) closely matched mechanical properties compared to native adult rat right ventricular myocardium, with stiffnesses controlled by polymer curing time; (2) heart cell contractility inducible by electric field stimulation with directionally-dependent electrical excitation thresholds (p<0.05); and (3) greater heart cell alignment (p<0.0001) than isotropic control scaffolds. Prototype bilaminar scaffolds with 3-D interconnected pore networks yielded electrically excitable grafts with multi-layered neonatal rat heart cells. Accordion-like honeycombs can thus overcome principal structural-mechanical limitations of previous scaffolds, promoting the formation of grafts with aligned heart cells and mechanical properties more closely resembling native myocardium.

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Until now, supercapacitors have been optimized in many ways to solve the abovementioned two main issues, such as the modification of existing materials, [5,6] the discovery of new materials, [7][8][9] the exploration of electrolytes, [10][11][12] the assembly of full supercapacitors, [13] the optimization of the voltage window etc. [14,15] Specifically, from the perspective of material development, RuO 2 is regarded as an ideal supercapacitor electrode material due to its high specific capacitance, but its high cost limits its practical application. [16,17] Thus, other nonnoble pseudocapacitive materials (for example, MnO 2 , [18] Fe 2 O 3 , [19] MoO 3 , [20] Nb 2 O 5 , [21] and VN [22] ) have attracted much attention. However, the poor electronic conductivity of most pseudocapacitor materials lead to their higher electrode resistances and lower power densities compared with those of EDLCs (Electrical Double Layer Capacitors) and electrolytic capacitors. [23] Very recently, 2D materials with high capacitances, such as MXenes, have been reported, but their main drawbacks are their complex synthetic processes and the use of highly toxic hydrofluoric acid (HF). [7,9] With regard to electrolytes, most researchers prefer aqueous electrolytes for their higher ionic concentration, lower resistance, lower cost, and better environmental-friendliness compared to those of organic electrolytes. [13,24,25] However, the limited potential window of aqueous supercapacitors, owing to the theoretical water splitting potential window of 1.23 V, is a challenge. To widen the potential window, supercapacitor electrodes must always be assembled into supercapacitor systems or so-called full supercapacitors, including symmetric supercapacitors, asymmetric supercapacitors, and hybrid supercapacitors. [4,5,13] To further enhance the voltage window of a single electrode or full supercapacitor, some methods have been adopted, including surface charge optimization, [14] electrode material modification, [15,26] electrolyte exploration, [5,10,24,27] and unique full supercapacitor system assemblies. [4,5,13] Although the above strategies have resulted in great progress for supercapacitors over the past few decades, the application of supercapacitors is still limited. Acquiring excellent performance while using simple methods is still a challenge. Thus, new strategies for the further development of supercapacitors are urgently needed. Herein, we propose a new view of the supercapacitor called the "integrated supercapacitor." As shown in the "supercapacitor tree" (Figure 1a), the integrated supercapacitor is a powerful strategy for integrating the traditional concepts of positive electrodes, negative electrodes, symmetric Charging times ranging from seconds to minutes with high power densities can be achieved by electrochemical capacitors in principle. Over the past few decades, the performance of supercapacitors has been greatly improved by the utilization of new materials, preparation of unique nanostructures, investigation of electrolytes, and ...

Biochemical and mechanical signals enabling cardiac regeneration can be elucidated using in vitro tissue-engineering models. We hypothesized that insulin-like growth factor-I (IGF) and slow, bi-directional perfusion could act independently and interactively to enhance the survival, differentiation, and contractile performance of tissue-engineered cardiac grafts. Heart cells were cultured on three-dimensional porous scaffolds in medium with or without supplemental IGF and in the presence or absence of slow, bi-directional perfusion that enhanced transport and provided shear stress. Structural, molecular, and electrophysiologic properties of the resulting grafts were quantified on culture day 8. IGF had independent, beneficial effects on apoptosis (p < 0.01), cellular viability (p < 0.01), contractile amplitude (p < 0.01), and excitation threshold (p < 0.01). Perfusion independently affected the four aforementioned parameters and also increased amounts of cardiac troponin-I (p < 0.01), connexin-43 (p < 0.05), and total protein (p < 0.01) in the grafts. Interactive effects of IGF and perfusion on apoptosis were also present (p < 0.01). Myofibrillogenesis and spontaneous contractility were present only in grafts cultured with perfusion, although contractility was inducible by electrical field stimulation of grafts from all groups. Our findings demonstrate that multi-factorial stimulation of tissue-engineered cardiac grafts using IGF and perfusion resulted in independent and interactive effects on heart cell survival, differentiation, and contractility.