A ToF-SSIMS study of plasma polymer-based patterned metal affinity surfaces

Polymers that exhibit an affinity to metal ions are important for separation science and sensor applications. In this paper, we describe the creation of surface micropatterns with three plasma polymers, acrylic acid (ppAAc), allylamine (ppAAm) and tetraglyme (ppTG). Time-of-Flight Static Secondary Ion Mass Spectrometry (ToF-SSIMS) imaging has been used to visualise the chemical specificity and selectivity of the plasma polymers as substrates for immoblised metal affinity protein separation. This technique provides the necessary spatial resolution to chemically resolve the multiple components present on these surfaces. Enzyme-linked immunosorbent assay (ELISA) was also employed to confirm the biological specificity of these surfaces. The results clearly demonstrate that under the correct solvent conditions, ppAAc-modified surfaces coordinate gallium and are able to selectively attract phosphoproteins. Critically, it is possible to then remove the protein from the surface and regenerate the chemistry using a simple elevated pH washing step. These results indicate the potential of these surfaces for implementation in microfluidic devices for the rapid isolation or pre-concentration of phosphopeptides/proteins.