Shape changes of the human red cell studied by aqueous two-phase partition

Tuning cell adhesion by controlling the roughness and wettability of 3D micro/nano silicon structures

The aim of this study is to investigate fibroblast cell adhesion and viability on highly rough three-dimensional (3D) silicon (Si) surfaces with gradient roughness ratios and wettabilities. Culture surfaces were produced by femtosecond (fs) laser structuring of Si wafers and comprised forests of conical spikes exhibiting controlled dual-scale roughness at both the micro- and the nano-scale. Variable roughness could be achieved by changing the laser pulse fluence and control over wettability and therefore surface energy could be obtained by covering the structures with various conformal coatings, which altered the surface chemistry without, however, affecting morphology. The results showed that optimal cell adhesion was obtained for small roughness ratios, independently of the surface wettability and chemistry, indicating a non-monotonic dependence of fibroblast adhesion on surface energy. Additionally, it was shown that, for the same degree of roughness, a proper change in surface energy could switch the behaviour from cell-phobic to cell-philic and vice versa, transition that was always correlated to surface wettability. These experimental findings are discussed on the basis of previous theoretical models describing the relation of cell response to surface energy. The potential use of the patterned Si substrates as model scaffolds for the systematic exploration of the role of 3D micro/nano morphology and/or surface energy on cell adhesion and growth is envisaged.

Surface properties of crosslinked erythrocytes as studied by counter-current distribution in aqueous polymer two-phase systems

The bifunctional imidoester dimethyl suberimidate hydrochloride can stabilize rat red blood cells (RBCs) by membrane protein crosslinking, and in that way they can be used as carrier systems for exogenous substances. Counter-current distribution fractionation in charge-sensitive dextran-polyethyleneglycol two-phase systems has been used to detect slight changes in surface charge in stabilized cells. A decrease in the surface charge of crosslinked RBCs and an apparent masking of the age-related cell surface properties have been found to result from the protein crosslinking. Digitonin treatment used to permeabilize crosslinked RBCs produces a significant decrease of the cell surface charge while the age-related surface properties do not seem to be modified by the treatment.

On the shape of human red blood cells interacting with flat artificial surfaces--the 'glass effect'

The morphology of the human red blood cell (RBC) contained between two flat artificial surfaces has been investigated. Shape transformation from the discocytic into various crenated (echinocytic) states was not caused solely by glass ('glass effect'). Various organic polymers, and mica, were effective, provided the distance (0.1 mm) between the two surfaces was carefully controlled. The discocytic state could only be preserved using moderately hydrophobic glass, extensive dimethylsilylation induced stomatocytes. With washed blood samples crenation occurred in a potassium chloride medium and in the presence of EDTA. Temperature-dependent transformation in the shape of human erythrocytes occurred between two glass surfaces 0.1 mm apart, e.g., in a hemacytometer. With cells in blood diluted directly 200-times with isotonic saline crenation appeared at 32-36 degrees C. A sphero-echinocytic state prevailed at 34 degrees C and outside the temperature range of 32-36 degrees C the RBCs retained the shape of a biconcave disk. Cells responding to the 'glass effect' even at temperatures below the transition region did not respond further at elevated temperatures. The 'glass effect' was found to be dependent on the RBC concentration (hematocrit). Raising this concentration reversibly decreased the degree of crenation. The amount of endogenous albumin present was estimated to be insufficient to cover the exposed glass surfaces with a protein monolayer. With washed cells over a wide concentration range, approximately the same total amount of albumin (serum) had to be present to avoid crenation, as long as observation was performed at a fixed low cell concentration. The effect of albumin was not abolished by gamma-globulin or anti-human albumin IgG. The discocyte-stabilizing influence of albumin is discussed.