Affinity capture of proteins from solution and their dissociation by contact printing

Biological experiments at the solid/liquid interface, in general, require surfaces with a thin layer of purified molecules, which often represent precious material. Here, we have devised a method to extract proteins with high selectivity from crude biological sample solutions and place them on a surface in a functional, arbitrary pattern. This method, called affinity-contact printing (α CP), uses a structured elastomer derivatized with ligands against the target molecules. After the target molecules have been captured, they are printed from the elastomer onto a variety of surfaces. The ligand remains on the stamp for reuse. In contrast with conventional affinity chromatography, here dissociation and release of captured molecules to the substrate are achieved mechanically. We demonstrate this technique by extracting the cell adhesion molecule neuron-glia cell adhesion molecule (NgCAM) from tissue homogenates and cell culture lysates and patterning affinity-purified NgCAM on polystyrene to stimulate the attachment of neuronal cells and guide axon outgrowth. The placement of functional molecules as biological layers on a substrate with highly controlled purity, density, functionality, and spatialization facilitates the study of biological phenomena such as protein deposition, molecular recognition, biocompatibility, and cell attachment at interfaces 1 . Conventionally, protein-coated surfaces are prepared by incubating the surface (for ~1 h) with a solution of the selected protein. This method requires concentrated solutions of purified proteins (up to 1 mg/ml), which often necessitates lengthy purification procedures 2 . We have developed a new procedure, called α CP, to extract proteins from complex media and place them as printed patterns directly on various solid substrates. The method weds the virtues of affinity purification 3