One-dimensional self-assembly of mouse embryonic stem cells using an array of hydrogel microstrands.

The ability of embryonic stem (ES) cells to self-renew indefinitely and to differentiate into multiple cell lineages holds promise for advances in modeling disease progression, screening drugs and treating diseases. To realize these potentials, it is imperative to study self-assembly in an embryonic microenvironment, as this may increase our understanding of ES cell maintenance and differentiation. In this study, we synthesized an array of one-dimensional alginate gel microstrands and aqueous microstrands through an SU-8 filter device by means of capillary action. Furthermore, we investigated self-assembly behaviors and differentiation potentials of mouse ES cells cultured in microstrands of varying diameters. We found that microstrands with an aqueous interior facilitated high density cell culture and formed compact microtissue structures, while microstrands with gelled interiors promote smaller cell aggregate structures. In particular, we noticed that ES cells collected from one-dimensional aqueous microstrands favored the differentiation towards cell lineages of endoderm and mesoderm, whereas those from gelled microstrands preferred to differentiate into ectoderm and mesoderm lineages. In addition to providing a "liquid-like" tubular microenvironment to understand one-dimensional self-assembly process of ES cells, this alginate hydrogel microstrand system also offers an alternative way to manipulate the stem cell fate-decision using bioengineered microenvironments.

A living cell-based biosensor utilizing G-protein coupled receptors: principles and detection methods.

This study explores the feasibility of using a bullfrog fibroblast cell line (FT cells) expressing G protein coupled receptors (GPCRs) as the basis for a living cell-based biosensor. We have fabricated gold microelectrode arrays on a silicon dioxide substrate that supports long term, robust growth of the cells at room temperature and under ambient atmospheric conditions. Activation of an endogenous GPCR to ATP was monitored with an optical method that detects rises in intracellular calcium and with an electrochemical method that monitors the increased secretion of pre-loaded norepinephrine on a MEMS device. FT cells were also transfected to express reporter genes driven by several different promoters, raising the possibility that they could be modified genetically to express novel GPCRs as well. The ability to harness GPCRs for BioMEMS applications by using cells that are easy to grow on MEMS devices and to modify genetically opens the way for a new generation of devices based on these naturally selective and highly sensitive chemoreceptors.