Microcontact Printing for Protein Microarray Applications

Abstract: This thesis introduces the microcontact printing (μCP) method to pattern and tailor the desired substrates for protein microarray applications. The ink molecules used to create the patterns, hydrophobic barriers, are tetraalkyl ammonium salt, polycationic polymers and oligo(ethylene glycol)-terminated self-assembled monolayers. The hydrophobicityof the printed barriers facilitates pinning of aqueous protein droplets in desired areas thereby promoting protein ligand immobilization.The characterizations of the printed microstructures (barriers) have been exploited by using a range of surface analytical methods including microscopic wetting, imaging null ellipsometry, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared reflection-absorption spectroscopy (FTIRAS) and fluorescence microscopy. These techniques reveal that the intrinsic property of the ink molecules and the difference in the interfacial free energies of the ink solutions and thepoly(dimethylsiloxane) (PDMS) stamp lead to the different morphologies at the printed patterns.Several strategies have been employed to remove or passivate the barriers after protein ligand immobilization in order to reduce the nonspecific interaction between the protein analytes and hydrophobic barriers.Protein ligand immobilization has been facilitated by using a piezo-dispenser. The biospecific interactions between the protein ligands and their counterparts are monitored by surface plasmon microscopy (SPM). The aim of this study is to demonstrate the generality of using microcontact printing to create protein microarrays for high throughput applications.