Highly aligned electrospun micro- and nanoscale fibers and pseudowoven mats were produced via electrospinning by incorporating an auxiliary counter electrode to create an electric field of controlled geometry and magnitude. Two polymers were examined using this technique: a polyimide (CP2) and a biodegradable polymer, poly(glycolic acid) (PGA). Highly aligned electrospun CP2 fibers were on the order of 10 μm in diameter, and fiber spacing in the spun mats ranged between 25 and 30 μm. Electrospun PGA aligned fibers were on the order of 500 nm in diameter with spacing between fibers ranging from 7 to 10 μm in the spun mats. High-speed videography illustrated the influence of the auxiliary electrode on the elimination of jet whipping and bending instability commonly associated with the electrospinning process. The data presented here demonstrate the direct influence of an opposing electric field on the degree of fiber alignment and control of fiber placement.

On Earth, biological systems have evolved in response to environmental stressors, interactions dictated by physical forces that include gravity. The absence of gravity is an extreme stressor and the impact of its absence on biological systems is ill-defined. Astronauts who have spent extended time under conditions of minimal gravity (microgravity) experience an array of biological alterations, including perturbations in cardiovascular function. We hypothesized that physiological perturbations in cardiac function in microgravity may be a consequence of alterations in molecular and organellar dynamics within the cellular milieu of cardiomyocytes. We used a combination of mass spectrometry-based approaches to compare the relative abundance and turnover rates of 848 and 196 proteins, respectively, in rat neonatal cardiomyocytes exposed to simulated microgravity or normal gravity. Gene functional enrichment analysis of these data suggested that the protein content and function of the mitochondria, ribosomes, and endoplasmic reticulum were differentially modulated in microgravity. We confirmed experimentally that in microgravity protein synthesis was decreased while apoptosis, cell viability, and protein degradation were largely unaffected. These data support our conclusion that in microgravity cardiomyocytes attempt to maintain mitochondrial homeostasis at the expense of protein synthesis. The overall response to this stress may culminate in cardiac muscle atrophy.

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