Short Peptides Enhance Single Cell Adhesion and Vi- ability on Microarrays

Abstract Single cell patterning holds important implications for biology, biochemistry, biotechnology, medicine, and bioinformatics. The challenge for single cell patterning is to produce small islands hosting only single cells and retaining their viability for a prolonged period of time. This study demonstrated a surface engineering approach that uses a covalently-bound short peptide as a mediator to pattern cells with improved single cell adhesion and prolonged cellular viability on gold patterned SiO 2 substrates. The underlying hypothesis is that cell adhesion is regulated by the type, availability and stability of effective cell adhesion peptides, and thus covalently bound short peptides would promote cell spreading and thus, single cell adhesion and viability. The effectiveness of this approach and the underlying mechanism for the increased probability of single cell adhesion and prolonged cell viability by short peptides were studied by comparing cellular behavior of human umbilical cord vein endothelial cells on three model surfaces whose gold electrodes were immobilized with fibronectin, physically adsorbed Arg-Glu-Asp-Val-Tyr, and covalently-bound Lys-Arg-Glu-Asp-Val-Tyr, respectively. The surface chemistry and binding properties were characterized by reflectance Fourier transform infrared spectroscopy. Both short peptides were superior to fibronectin in producing adhesion of only single cells, while the covalently bound peptide also reduced apoptosis and necrosis of adhered cells. Controlling cell spreading by peptide binding domains to regulate apoptosis and viability represents a fundamental mechanism in cell-materials interaction and provides an effective strategy in engineering arrays of single cells

Structure and Mechanical Properties of a Copper Combustion Chamber throughout Its Life Cycle

The material of a combustion chamber is subjected to high thermal and mechanical fatigue that can result in premature failure. Nevertheless, there is very little information in the literature concerning its characterization. In this work, the study of some properties of the copper combustion chambers in water heaters throughout their life cycle is described. The microstructure, hardness, morphology, mechanical strength and roughness were evaluated, from the pristine copper sheet to a chamber subjected to 53,000 cycles. Throughout the whole cycle, changes were detected in the organization of the crystalline structure. Both after conformation and after completing the manufacturing process, the material exhibits a preferential orientation according to the direction [110], which is the most favorable to degradation of the material by thermal fatigue. The prevalence of the less dense crystallographic planes of the material in all stages of the life cycle allowed a better diffusion of the oxidant species facilitating the corrosion of the material. The oxidation products did not form a passivated layer and detached from the bulk copper, causing a progressive deterioration of the material