The Relative Importance of Topography and RGD Ligand Density for Endothelial Cell Adhesion

The morphology and function of endothelial cells depends on the physical and chemical characteristics of the extracellular environment. Here, we designed silicon surfaces on which topographical features and surface densities of the integrin binding peptide arginine-glycine-aspartic acid (RGD) could be independently controlled. We used these surfaces to investigate the relative importance of the surface chemistry of ligand presentation versus surface topography in endothelial cell adhesion. We compared cell adhesion, spreading and migration on surfaces with nano- to micro-scaled pyramids and average densities of 6×102–6×1011 RGD/mm2. We found that fewer cells adhered onto rough than flat surfaces and that the optimal average RGD density for cell adhesion was 6×105 RGD/mm2 on flat surfaces and substrata with nano-scaled roughness. Only on surfaces with micro-scaled pyramids did the topography hinder cell migration and a lower average RGD density was optimal for adhesion. In contrast, cell spreading was greatest on surfaces with 6×108 RGD/mm2 irrespectively of presence of feature and their size. In summary, our data suggest that the size of pyramids predominately control the number of endothelial cells that adhere to the substratum but the average RGD density governs the degree of cell spreading and length of focal adhesion within adherent cells. The data points towards a two-step model of cell adhesion: the initial contact of cells with a substratum may be guided by the topography while the engagement of cell surface receptors is predominately controlled by the surface chemistry

Effective extra-cellular recording from vertebrate neurons in culture using a new type of micro-electrode array

We describe the fabrication and use of a new type of extracellular micro-electrode array mounted on a flexible transparent polyimide substrate that can be rapidly moved from one part of a culture of vertebrate neurons (rat nodose) to another, which permits co-culture of glia under the neurons and is easily and rapidly replaceable in the event of damage. The array can be mounted on a micromanipulator and moved into place whenever and wherever recordings with or without stimulation are needed. The basic electrode system consists of 20-30 microm diameter gold electrodes, with or without platinisation, exposed to the cells through openings in the polyimide and joined to the recording or stimulating circuitry through gold tracks embedded in the polyimide. If rigid control over neuron placement has been achieved the patterns of electrodes can be matched to the neuron positions

Implementing Digital Enterprise Technologies for Agile Design in the virtual enterprise

Digital Enterprise Technology (DET) is defined as a synthesis of digital and physical systems across the product lifecycle which can be exploited for two main benefits: risk mitigation through consistent and seamless data standards; and reduction in product development times through improved access to the most accurate project data at any time, from anywhere, by anyone. Agility is defined as responsiveness to unpredictability, particularly unpredictable events in the environment external to a process. The general need for agile response in turbulent environments is well documented and has been analysed at the manufacture phase. This paper introduces a framework for an agile response to these turbulent environments during the design stages of product development. The Agile Design Framework is based on the founding principles described as DET, with the added benefit of reduced reaction time and therefore greater agility in the face of unpredicted external events. A 4 level classification scheme for event impact is discussed and a common toolbox of Digital Enterprise Technologies (Core Tools) for agile design is introduced. The paper proposes the implementation of the DET-based Core Tools during a meta-design stage, for maximum benefit from the synergies of the many systems