AVS 60th International Symposium and Exhibition
    Thin Film Wednesday Sessions
       Session TF+AS+BI+EM+SE+SS-WeA

Paper TF+AS+BI+EM+SE+SS-WeA8
Controlled Modification of Protein-Repelling Monomolecular Films by Ultraviolet Light: The Effect of Wavelength and Implications for Lithography

Wednesday, October 30, 2013, 4:20 pm, Room 104 A

Session: Applications of Self-Assembled Monolayers and Nano-Structured Assemblies
Presenter: M. Zharnikov, University of Heidelberg, Germany
Authors: Y.L. Jeyachandran, University of Heidelberg, Germany
A. Terfort, Frankfurt University, Germany
M. Zharnikov, University of Heidelberg, Germany
Correspondent: Click to Email
Advanced lithographic techniques applied to monomolecular resists enable the fabrication of well-defined patterns of functional biomolecules, above all proteins, and specific receptors, which are the key elements of biosensors, bio-fouling analysis assays, cell studies, and tissue engineering applications. An essential element of such patterns is a protein-repelling “background” surrounding the pre-selected sensing areas and preventing non-specific adsorption of proteins beyond these regions. Here we use protein-repelling oligo(ethylene glycol) (OEG) terminated alkanethiolate (AT) monolayers on gold as matrix for the preparation of such patterns. Exposure of this matrix to ultraviolet (UV) light results in the damage of the OEG chains and photooxidation of the thiolate headgroups, which can be used for controlled tuning of protein-repelling properties within so-called UV direct writing (UVDW) approach or for the preparation of mixed OEG-AT/specific-receptor films by so-called UV-promoted exchange reaction (UVPER). Using several model systems, we studied the effect of the wavelength (254 – 390 nm) on the course and efficiency of the UVDW and UVPER processes applied to different OEG-AT matrices. The cross sections of the UV induced damage were found to decrease significantly with increasing wavelength of UV light. In accordance with this behavior, the efficiencies of both UVDW and UVPER were maximal at a wavelength of 254 nm, somewhat lower at 313 and 365 nm, and lowest at 390 nm. Both UVDW and UVPER allowed a fine tuning of protein affinity for non-specific and specific adsorption, respectively, but UVDW did not occur below a certain, wavelength-dependent threshold dose. Performing UVPER below this dose enables to suppress possible non-specific adsorption of proteins even in the case of non-complete exchange of the UV-damaged molecules of the primary OEG-AT matrix by receptor-bearing moieties. The obtained results are of direct relevance for the preparation of high-quality mixed OEG-AT/specific-receptor films and the fabrication of complex protein patterns.