Microscopic Fabrication And Selective Adsorption Of Protein On Polymer Surfaces

The fabrication of microscopic topology on polymer surfaces is essential for the design of high performance biosensors and medical devices by the control of interactions between material surfaces and biomolecules. Protein and other biomolecules can be selectively adsorbed onto the designated micro areas by the functionality and patterning of polymer surfaces. For example, surfaces containing COOH functionalities are widely used to bind proteins ionically or covalently for biosensors applications and for cell growth assays; and the surfaces modificated with PEG chains, which resist non-specific protein adsorption, are used to improve the biocompatibility of polymer surfaces. However, the functional groups introduced onto an inert polymer surface directly will be unstable and lose reactivity over time for the surface rearrangement. Storing the functionalized surface cold or in a polar solvent may minimize surface rearrangement, while both the resolutions will limit the practical applications of polymers in biomedicine. Therefore the solution of this surface restructuring problem is worthy of consideration.Recently noble metals such as gold and silver, have been deposited on polymer surfaces to modify the chemical inertness of the surface. If metal composites can be firmly combined onto polymer substrates, further grafting with macromolecules containing sulfydryl groups could be conducted to control the biocompatibility of polymer surfaces. Sulfydryl group containing species, which could be immobilized firmly and easily on metal surfaces via covalent bonds due to the strong interaction between the metal surface and the sulfydryl group, can control interactions between polymer surfaces and biomolecules through another reactive end groups such as carboxyl group, amino group, ethylene glycol group etc. Meanwhile base on that a metal surface does not exist the surface rearrangement phenomenon, it has become one of the most valuable platforms for biomolecular immobilization. Protein selective adsorption can be realized through further modification after metal patterning on polymer surfaces. However, site-selective adsorption of biomolecules on polymer surfaces controlled by metal micropatterning has rarely been reported so far. Proteins were precisely patterned on PET surfaces through VUV lithography and chemical selectivity.We have exploited two different methods to realize selective protein adsorption on PET surfaces:one is VUV modification, and the other is metal modification. And we compared both the methods in the selectivity effect at last. The main research contents are listed as follows:1. Protein micropattern was fabricated on the patterned PET surfaces modified with PEG, which was realized by VUV technique and self-assembled monolayer. Chemical composition and topographies changes of the modified PET surfaces were characterized and analyzed by X-ray photoelectron spectroscopy (XPS), atomic force microscope (AFM) and static water contact angle, which showed that both APTES and PEG modification were successful. Fluorescence microscope showed that uniform biological patterns were obtained and bovine serum albumin (BSA) molecules were selectively adsorbed to designated micro areas on the PET surface. These results suggested that this technique can be extended to other polymeric materials and will be useful in fields where arrays of protein patterns are desired.2. Selective adsorption of protein controlled by silver patterns was realized on PET surfaces through electroless metallization. The PET regions were finally modified using UV irradiation to have a high affinity for the desired proteins. Contact angle measurements for surface wettability, XPS for chemical compositions and Field emission scanning electron microscopy (FESEM) for metal patterns characterization were conducted to confim the success of the surface modification reactions and the surface patterning effect. All the detection results showed that the surface modification reactions were successfully and the silver patterns obtained were uniform and sharp. Protein surface coverage was visualized by fluorescence microscopy, which investigated that protein patterns obtained were clear and uniform, and BSA was selectively absorbed on the designated micro areas of PET surface.3. Two methods mentioned in this paper were compared in the selectivity effect at last. It is discovered that protein patterning controlled by silver patterns has better selectivity with higher stability of functional groups on modified polymer surfaces. Our research supplies new direction for selective protein adsorption, and contributes to biosensor fabrication in theoretical analysis.