Chemically patterned, metal oxide based surfaces produced by photolithographic techniques for studying protein- and cell-surface interactions I: Microfabrication and surface characterization.
Chemical patterns on smooth wafer substrates comprising areas with two different metals have been produced by vacuum metal deposition and photolithographic techniques. The combination of metals has been chosen from the series titanium (Ti), aluminium (Al), vanadium (V) and niobium (Nb), producing patterns (dots and stripes with dimensions of 50, 100 and 150 micrometer) with one of the metals as the background and with the second metal (foreground pattern) deposited on the background metal. The structure and chemical composition of the patterned surfaces were evaluated by scanning electron microscopy, X-ray photoelectron spectroscopy and imaging time-of-flight secondary-ion mass spectrometry. The surfaces proved to be geometrically well defined with the expected surface-chemical composition, i.e. a surface oxide (passive) film essentially composed of TiO(2),Al(2)O(3),V(2)O(5), or Nb(2)O(5). Ti/Ti patterned surfaces were produced as controls and found to show no chemical composition contrast. The surface roughness of the pattern was greater than that of the background by a factor of 2-3, but was still extremely smooth with Ra<2nm. The patterns serve as model surfaces for studying in vitro the behaviour of cells as well as the adsorption of serum proteins on different metal oxides, which will be reported in a companion paper. These surfaces can be used to compare and contrast the response of osteoblasts to Ti and other alloy components, such as Al, V, or Nb, which are used in load-bearing medical implants.