Preparation and characterisation of dry thin native protein trehalose films on titanium-coated cyclo-olefin polymer (COP) foil generated by spin-coating/drying process and applied for protein transfer by Laser-Induced-Forward Transfer (LIFT)

Laser-Induced-Forward Transfer (LIFT) is a non-contact method for transferring bioactive substances such as proteins from a so-called LIFT target, here a titanium-coated cyclo-olefin polymer (COP) foil, to a surface of a solid work piece, e.g. a medical implant. The quality of the surface coating of the LIFT target, i.e. its homogeneity and the bioactivity of the ingredients to be transferred, is crucial for the quality and the efficiency of the overall process. Here, aqueous trehalose solutions containing the proteins streptavidin, green fluorescent protein (GFP), and bovine serum albumin were used in a spin-coating/drying process to render dry thin native protein trehalose films on titanium-coated COP foils. The homogeneity of the layer thicknesses was characterised by spectroscopic ellipsometry and the homogeneity of the GFP distribution within the layer was monitored by fluorescence scan analyses. The bioactivity of the embedded proteins was probed after short- and long-term storage by FT-IR spectroscopy in spectral reflection method and biological activity tests based on fluorescence scan analyses. After application of the LIFT process, the transferred proteins were tested in their bioactivity by fluorescence scan analyses and their topology by AFM analysis, proving that highly functional LIFT targets can be prepared by the chosen method.