A novel adhesion Layer is described that enables covalent attachment of cell adherent molecules to the surfaces of poly(ethylene terephthalate) (PET) and poly(aryl-ether-ether-ketone) PEEK. Vapor of zirconium or titanium tetra (tert-butoxides) can be deposited on the surface of PET or PEEK at room temperature at a pressure of ca. 10(-3) mm Hg. The thickness of this layer can be controlled by exposure time and monitored by quartz crystal microgravimetry on a surrogate substrate. Controlled thermolysis of the deposited alkoxide gives the metal a mixed oxide-alkoxide layer, which reacts with solutions of phosphonic acids to attach monolayer films of phosphonates, several of which are shown to significantly enhance cell growth compared with the untreated surface.