Surface sulfonates lock serum albumin into a "hard" corona.

The composition of the layer of proteins adsorbed to macro- or microscopic surfaces of synthetic origin influences the response of living systems to these materials. This adsorbed layer of proteins usually comprises a "soft" coating or corona of labile or exchangeable adsorbed proteins on top of a more tenaciously held "hard" corona in contact with the surface. Here, we link the dependence of cell adhesion on a 20 nm film of polyelectrolyte complex to the "hardness" of the initial corona using albumin, the most prevalent protein in serum.

Stressful Surfaces: Cell Metabolism on a Poorly Adhesive Substrate.

The adhesion and proliferation of cells are exquisitely sensitive to the nature of the surface to which they attach. Aside from cell counting, cell "health" on surfaces is typically established by measuring the metabolic rate with dyes that participate in the metabolic pathway or using "live/dead" assays with combinations of membrane permeable/impermeable dyes. The binary information gleaned from these tests-whether cells are attached or not, and whether they are living or dead-provides an incomplete picture of cell health.

Cell Adhesion and Proliferation on the "Living" Surface of a Polyelectrolyte Multilayer.

The adhesion of living eukaryotic cells to a substrate, one of the most complex problems in surface science, requires adsorption of extracellular proteins such as fibronectin. Thin films of polyelectrolyte complex made layer-by-layer (polyelectrolyte multilayers or PEMUs) offer a high degree of control of surface charge and composition-interconnected and essential variables for protein adhesion. Fibroblasts grown on multilayers of poly(styrenesulfonate), PSS, and poly(diallyldimethylammonium), PDADMA, with increasing thickness exhibit good adhesion until the 12th layer of polyelectrolyte has been added, whereupon there is a sudden transition to nonadhesive behavior.

Quasi-Spherical Cell Clusters Induced by a Polyelectrolyte Multilayer.

Fibroblasts cultured on polyelectrolyte multilayers, PEMUs, made from poly(diallyldimethylammonium), PDADMA, and poly(styrene sulfonate), PSS, showed a variety of attachment modes, depending on the charge of the last layer and deposition conditions. PEMUs terminated with PDADMA (cationic) were cytotoxic when built in 1.0 M NaCl but cytophilic when built in 0.