Cardiac myocytes and fibroblasts are essential elements of myocardial tissue structure and function. In vivo, myocytes constitute the majority of cardiac tissue volume, whereas fibroblasts dominate in numbers. In vitro, cardiac cell cultures are usually designed to exclude fibroblasts, which, because of their maintained proliferative potential, tend to overgrow the myocytes. Recent advances in microstructuring of cultures and cell growth on elastic membranes have greatly enhanced in vitro preservation of tissue properties and offer a novel platform technology for producing more in vivo-like models of myocardium. We used microfluidic techniques to grow two-dimensional structured cardiac tissue models, containing both myocytes and fibroblasts, and characterized cell morphology, distribution, and coupling using immunohistochemical techniques. In vitro findings were compared with in vivo ventricular cyto-architecture. Cardiac myocytes and fibroblasts, cultured on intersecting 30-μm-wide collagen tracks, acquire an in vivo-like phenotype. Their spatial arrangement closely resembles that observed in native tissue: Strands of highly aligned myocytes are surrounded by parallel threads of fibroblasts. In this in vitro system, fibroblasts form contacts with other fibroblasts and myocytes, which can support homogeneous and heterogeneous gap junctional coupling, as observed in vivo. We conclude that structured cocultures of cardiomyocytes and fibroblasts mimic in vivo ventricular tissue organization and provide a novel tool for in vitro research into cardiac electromechanical function.

Applying life sciences and engineering principles to the study of cells and engineered tissue has resulted in various successes. These endeavors are poised towards development of functional neo-organs used as native tissue substitutes. Concurrent with this goal, research arenas are directed in the general areas of biocompatible polymer scaffolds, biomimmetic extracellular matrices, control of stem cell differentiation, biomolecule signaling, and directed material delivery. Optomec Inc. is developing an aerosol-based direct-write process for deposition of biological materials into three dimensional, micron-scale patterns. The process uses pneumatic atomization to produce aerosol droplets of proteinacious colloidal dispersions and whole cell suspensions. The droplets are entrained in an air stream and deposited with a proprietary deposition tool. The biological materials can be seeded into three dimensional polymer scaffolds and various substrate surfaces. Optomec's direct write process has applicability to the additive fabrication of engineered tissue. Other applications of the direct write tool include rapid prototyping of analytical biosensors, hybrid BioMEMS, and bio-chip microarray devices.

A focused ion beam (FIB) interface attached to a column of 200 keV transmission electron microscope (TEM) was developed for in situ micropatterning to semiconductors. TEM specimens of Si and GaAs, and those of a thin Ni2Si layer on a Si substrate were micromilled in the TEM during observation. A set of 6 x 6-um squares and alphabet letters were patterned with a 25 keV Ga+-FIB of 0.2-μm beam diameter at room temperature. The effect of FIB irradiation on the structural evolution was observed simultaneously by a TV-rate video camera and sequentially by regular film. FIB micropatterning to semiconductor specimens caused amorphization and Ga injection. The excess Ga in the specimens precipitated as metastable solid γ-phase for Si and as liquid phase for GaAs. Ni2Si/Si specimens lost silicide crystallinity after FIB patterning. Annealing of these bilayer specimens at 673K resulted in the precipitation of Ni-rich silicide.