SURFACE CHEMISTRY EVALUATION IN THE DESIGN AND FABRICATION OF MICRO-DEVICES FOR PROTEIN ANALYSIS

In this Ph.D. thesis, the problem of the coating and adhesion of polymers onto selected surfaces has been investigated with the aim of designing micro-devices and/or microarrays for protein analysis. In the first part of the thesis, the micro-fabrication of a device for isoelectric focusing has been studied. The development of this device has required the covalent attachment of hydrogel plugs functionalized with pH buffering monomers on an Indium Tin Oxide (ITO) flat surface. The two ITO-coated slides are separated by silicon frames (both 3mm thick) stuck on the surface and the whole device was named as Micro Parallel Isoelectric focusing Device (MPID). The problem of the adhesion of the hydrogel plugs onto the ITO anode under the high vacuum conditions of the MALDI-TOF/TOF analysis has been solved, by properly selecting the percentage of monomers and related polymerization conditions. The MPID fabricated in accord to previous observations did not afford a completely efficient isolectric separation of the model protein mixture (commercial carbonic anhydrase). Furthermore, the proteins were absorbed onto plugs too tightly for a satisfactory, direct analysis by MALDITOF/ TOF of the plugs. At this stage of the Ph.D. program, the MPID project has been abandoned and the second part of the Ph.D. thesis has been directed towards the study of a functional coating onto different surfaces using a polymer that is the result of the co-polymerization of N,N-dimethylacrylamide (DMA), 3- (trimethoxysilyl)-propylmethacrylate (MAPS) and acryloyloxysuccinimide (NAS) [ Copoly (DMANAS- MAPS)]. It has been shown that this copolymer is able to generate thin layer of nanometer size onto inorganic substrates like glass, silicon oxide, or gold, typically used for the development of microarrays or bio-sensors for immunoassays. Applications of silicon and gold surfaces coated by Copoly (DMA-NAS-MAPS) are presented and discussed.